Search for pair production of vector-like T and B quarks in single-lepton final states using boosted jet substructure in proton-proton collisions at \( \sqrt{s}=13 \) TeV

Journal of High Energy Physics, Nov 2017

Abstract A search for pair production of massive vector-like T and B quarks in proton-proton collisions at \( \sqrt{s}=13 \) TeV is presented. The data set was collected in 2015 by the CMS experiment at the LHC and corresponds to an integrated luminosity of up to 2.6 fb−1. The T and B quarks are assumed to decay through three possible channels into a heavy boson (either a W, Z or Higgs boson) and a third generation quark. This search is performed in final states with one charged lepton and several jets, exploiting techniques to identify W or Higgs bosons decaying hadronically with large transverse momenta. No excess over the predicted standard model background is observed. Upper limits at 95% confidence level on the T quark pair production cross section are set that exclude T quark masses below 860 GeV in the singlet, and below 830 GeV in the doublet branching fraction scenario. For other branching fraction combinations with ℬ(T → tH) + ℬ(T → bW) ≥ 0.4, lower limits on the T quark range from 790 to 940 GeV. Limits are also set on pair production of singlet vector-like B quarks, which can be excluded up to a mass of 730 GeV. The techniques showcased here for understanding highly-boosted final states are important as the sensitivity to new particles is extended to higher masses. Open image in new window

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Search for pair production of vector-like T and B quarks in single-lepton final states using boosted jet substructure in proton-proton collisions at \( \sqrt{s}=13 \) TeV

Received: June 13 TeV substructure in proton-proton collisions A search for pair production of massive vector-like T and B quarks in protonproton collisions at p s = 13 TeV is presented. The data set was collected in 2015 by the CMS experiment at the LHC and corresponds to an integrated luminosity of up to 2.6 fb 1 . The T and B quarks are assumed to decay through three possible channels into a heavy boson (either a W, Z or Higgs boson) and a third generation quark. This search is performed in nal states with one charged lepton and several jets, exploiting techniques to identify W or Higgs bosons decaying hadronically with large transverse momenta. No excess over the predicted standard model background is observed. Upper limits at 95% con dence level on the T quark pair production cross section are set that exclude T quark masses below 860 GeV in the singlet, and below 830 GeV in the doublet branching fraction scenario. For other branching fraction combinations with B(T ! tH) + B(T ! bW) Hadron-Hadron scattering (experiments); Heavy quark production; vector- - and B The CMS collaboration 0:4, lower limits on the T quark range from 790 to 940 GeV. Limits are also set on pair production of singlet vector-like B quarks, which can be excluded up to a mass of 730 GeV. The techniques showcased here for understanding highly-boosted nal states are important as the sensitivity to new particles is extended to higher masses. 1 Introduction 2 The CMS detector and event reconstruction 3 Data and simulated samples 4 Reconstruction methods 5 Boosted H channel Lepton reconstruction and selection Hadronic W and H tagging Event selection and categorization Background modeling 4.1 4.2 5.1 5.2 6.1 6.2 6 Boosted W channel Event selection Background modeling 7 Systematic uncertainties 8 Results 9 Summary The CMS collaboration 1 Introduction The discovery of a light mass Higgs boson (H) [1{3] motivates searches for new interactions and particles at the LHC [4]. Cancellation of the loop corrections to the Higgs boson mass without precise ne tuning of parameters requires new particles at the TeV scale. Such new particles are the bosonic partners of the top quark, in supersymmetric models, or the fermionic top quark partners predicted by many other theories, such as little Higgs [5, 6] and composite Higgs [7{10] models. These heavy quark partners predominantly mix with the third-generation quarks of the standard model (SM) [11, 12] and have vector-like transformation properties under the SM gauge group SU(2)L U(1)Y SU(3)C, hence the term \vector-like quarks" (VLQ). While a chiral extension of the SM quark family has been strongly disfavored by precision electroweak studies at electron-positron colliders [13, 14] and by observed production cross sections and branching fractions of the Higgs boson [15], models with VLQs are not excluded by present data. { 1 { g T T b W W, H, Z b, t, t g g t H W, H, Z b, t, t g g T T T T T quark decaying to bW (left), tH (middle), and tZ (right). We search for a vector-like T quark with charge 2/3 (in units of the electron charge) that is produced via the strong interaction in proton-proton collisions along with its antiquark, T. Many models in which VLQs appear assume that T quarks decay to three nal states: bW, tZ, or tH [16]. Leading-order Feynman diagrams of these three processes are shown in gure 1, created with the tools of ref. [17]. The partial decay widths depend on the particular model [18], so that the branching fractions of these decay modes can take on various possible values, with the sum of all three branching fractions equal to unity. An electroweak isospin singlet T quark is expected to have a branching fraction of approximately 50% for T ! bW, and 25% for each of T ! tZ and tH, and is used as a benchmark for gures and tables. A T quark in a weak isospin doublet has no decays to bW and equal branching fractions for tZ and tH decays [18{20]. As these are, however, not the only possible representations of T quarks, the nal results are interpreted for many allowed branching fraction combinations. Though this search is optimized for TT production, decays of vector-like bottom quark partners (B quarks) can produce similar topologies and BB production is also considered. The B quark with charge 1=3 is expected to decay to tW, bH, or bZ and can also transform either as a singlet or doublet under the electroweak symmetry group. The respective branching fractions are equal to those of the corresponding T quark decays to the same SM bosons. For this search we assume that only one new particle is present, either the T or B quark. p s = 13 TeV [27, 28]. Most recently, searches for pair-produced T and B quarks were performed by both the ATLAS and CMS collaborations at p s = 8 TeV [21{26]. Depending on the assumed combination of branching fractions to the three decay modes, the CMS collaboration observed lower limits on the T quark mass with values ranging from 720 to 920 GeV and on the B quark mass with values ranging from 740 to 900 GeV at 95% con dence level (CL) [21, 25]. The ATLAS collaboration found similar lower mass limits, so that vector-like T and B quarks with masses below 720 GeV are already excluded for all possible branching fraction combinations. We therefore only consider VLQ masses above 700 GeV in this search. The ATLAS collaboration has also searched for pair production of T and B quarks at We require one electron or one muon in the nal state, along with several jets. All decay modes of the T and B quarks produce t quarks and/or W bosons, which are the dominant sources of leptons. In the high mass region that we consider, the decay products { 2 { t Z W, H, Z b, t, t HJEP1(207)85 can have a large Lorentz boost and result in highly collinear nal state particles. This search makes use of techniques to identify b quark jets and reconstruct hadronic decays of massive particles that are highly Lorentz-boosted in the reference frame of the TT system. The data are analyzed in two channels that are optimized for sensitivity to either boosted W or Higgs bosons, referred to as the \boosted W" and \boosted H" channels. The boosted W channel is most sensitive to scenarios where the T quark has a large branching fraction for bW decays (such as the electroweak singlet benchmark) while the boosted H channel has the highest sensitivity to scenarios with a large branching fraction to tH (such as the electroweak doublet benchmark). The T ! tZ decay mode is not a particular target of this search, but Lorentz-boosted Z bosons decaying hadronically can be selected in either channel since the signatures are similar to those of boosted hadronic W or Higgs boson decays, thus providing some sensitivity to the tZ decay mode. 2 The CMS detector and event reconstruction from Z ! e+e The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic eld of 3.8 T. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forward calorimeters extend the pseudorapidity ( ) [29] coverage provided by the barrel and endcap detectors. Muons are measured in gas-ionization detectors embedded in the steel ux-return yoke outside the solenoid. A particle- ow (PF) algorithm [30] is used to reconstruct and identify each individual particle in an event with an optimized combination of information from the various elements of the CMS detector. The energy of photons is directly obtained from the ECAL measurement, corrected for zero-suppression e ects. The energy of electrons is determined from a combination of the electron momentum at the primary interaction vertex as determined by the tracker, the energy of the corresponding ECAL cluster, and the energy sum of all bremsstrahlung photons spatially compatible with originating from the electron track. The momentum resolution for electrons with transverse momentum pT 45 GeV decays ranges from 1.7% for low-bremsstrahlung electrons in the barrel region to 4.5% for showering electrons in the endcaps [31]. The energy of muons is obtained from the curvature of the corresponding track. Matching muons to tracks measured in the silicon tracker results in a relative transverse momentum resolution for muons with 20 < pT < 100 GeV of 1.3{2.0% in the barrel and better than 6% in the endcaps. The pT resolution in the barrel is better than 10% for muons with pT up to 1 TeV [32]. The energy of charged hadrons is determined from a combination of their momenta measured in the tracker and the matching ECAL and HCAL energy deposits, corrected for zerosuppression e ects and for the response function of the calorimeters to hadronic showers. Finally, the energy of neutral hadrons is obtained from the corresponding corrected ECAL and HCAL energy. Jets are reconstructed from the individual particles produced by the PF event algorithm, clustered using the anti-kT algorithm [ 33, 34 ] with distance parameters of 0.4 (\AK4 { 3 { jets") or 0.8 (\AK8 jets"). Jet momentum is de ned as the vectorial sum of all particle momenta in the jet, and is found from simulation to be within 5 to 10% of the true momentum over the whole pT spectrum and detector acceptance. All jets are required to have j j < 2:5 and AK4 (AK8) jets must have pT > 30 (200) GeV. An o set correction is applied to jet energies to take into account the contribution from additional proton-proton interactions within the same or nearby bunch crossings (pileup) [35]. Jet energy corrections are derived from simulation, and are con rmed with in situ measurements of the energy applied to jets are propagated to ETmiss. balance in dijet and photon/Z(! ee= ) + jet events [36]. A smearing of the jet energy is applied to simulated events to mimic the energy resolution observed in data, typically 15% at 10 GeV, 8% at 100 GeV, and 4% at 1 TeV. Additional selection criteria are applied to each event to remove spurious jet-like features originating from isolated noise patterns in the HCAL [37], anomalously high energy deposits in certain regions of the ECAL, and cosmic ray and beam halo particles that are detected in the muon chambers. The missing transverse momentum vector is de ned as the projection on the plane perpendicular to the beams of the negative vector sum of the momenta of all reconstructed particles in an event. Its magnitude is referred to as ETmiss. The energy scale corrections A more detailed description of the CMS detector, together with a de nition of the coordinate system used and the relevant kinematic variables, can be found in ref. [29]. 3 Data and simulated samples The data used in this analysis were collected during 2015 when the LHC collided protons at p s = 13 TeV with a bunch spacing of 25 ns. The data set for the boosted W channel corresponds to an integrated luminosity of 2.3 fb 1. The data set for the boosted H channel in the electron (muon) channel corresponds to 2.5 (2.6) fb 1 and includes additional data collected with poor forward calorimeter performance where the ETmiss has been re-computed excluding the a ected region of the detector. To compare the SM expectation with the experimental data, samples of events for all relevant SM background processes and the TT signal are produced using Monte Carlo (MC) simulation. Background processes are simulated using several matrix element generators. The powheg v2 generator [38{41] is used to simulate tt events, as well as single top quark events in the tW channel at next-to-leading order (NLO). The MadGraph5 amc@nlo 2.2.2 generator [42] is used for generation at NLO of Drell-Yan + jets and tt + W events, as well as tt + Z events, and s- and t-channel production of single top quarks. The FxFx scheme [43] for merging matrix element generation to the parton shower is used. The MadGraph v5.2.2.2 generator is used with the MLM scheme [44] to generate W + jets, Drell-Yan + jets, and multijet events at leading order. pythia 8.212 [45, 46] is used for the simulation of multijet and diboson events. The boosted W channel uses the NLO Drell-Yan + jets simulation and the MadGraph multijet simulation. The boosted H channel uses the MadGraph Drell-Yan + jets simulation, and the pythia multijet simulation which is ltered for processes likely to pass the lepton selection in this channel. Background samples are grouped into three { 4 { T or B quark mass [GeV] Cross section [fb] 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 455 196 90 44 22 samples; and \QCD", including multijet samples. Signal samples for both TT and BB production are simulated using MadGraph for mass points between 700 and 1800 GeV in steps of 100 GeV. A narrow width of 10 GeV is assumed for the vector-like quarks. Predicted cross sections, which depend only on the vector-like quark mass, are computed at next-to-next-to-leading order (NNLO) with the Top++2.0 program [47{52] and are listed in table 1. Parton showering and the underlying event for all simulated samples are obtained with pythia using the CUETP8M1 tune [53, 54]. To simulate the momentum spectrum of partons inside the colliding protons, the NNPDF3.0 [55] parton distribution functions (PDFs) are used. Detector simulation for all MC samples is performed with Geant4 [56] and includes the e ect of pileup. 4 Reconstruction methods We perform a search for T quarks that decay to nal states with an electron or a muon, and jets. Selected events must have one or more pp interaction vertices within the luminous region (longitudinal position jzj < 24 cm and radial position < 2 cm), reconstructed using a deterministic annealing lter algorithm [57]. The primary interaction vertex is the vertex with the largest P p2T from its associated jets, leptons, and ETmiss. The number of pileup interactions di ers between data and simulation, so simulated events are weighted to re ect the pileup distribution expected in data given a total inelastic cross section of 69 mb [58]. { 5 { Two observables that are useful in discriminating signal from background events, exploiting the fact that the decays of T quarks to single-lepton nal states produce a large number of hadronic objects, are the following: the quantity HT, de ned as the scalar pT de ned as the scalar sum of ETmiss, the pT of the lepton, and HT. sum of all reconstructed AK4 jets with pT > 30 GeV and j j < 2:4, and the quantity ST, Lepton reconstruction and selection This search requires one charged lepton, either an electron or a muon, to be reconstructed within the acceptance region of j j < 2:4. The event must satisfy a single-electron or singlemuon trigger. The choice of triggers is adapted to the particular nal state targeted in each channel. In T ! bW decays, the W boson is generally well separated from the associated bottom quark since the T quark has low pT compared to its mass, leading to a low level of hadronic activity in close proximity to the lepton. In contrast, a lepton originating from a top quark decay (e.g., from a T ! tH decay) becomes increasingly collinear with the associated bottom quark as the T quark mass increases and the Lorentz boost of the top quark rises. As a consequence of the above, the boosted W channel uses triggers selecting leptons that are isolated with respect to nearby PF candidates, either electron candidates with pT > 27 GeV and j j < 2:1, or muon candidates with pT > 20 GeV. The triggers used in the boosted H channel do not require that the leptons are isolated. In the electron channel, events with at least one electron candidate with pT > 45 GeV, one AK4 jet with pT > 200 GeV, and another AK4 jet with pT > 50 GeV are selected by the trigger. The muon channel trigger selects events with a muon candidate with pT > 45 GeV and j j < 2.1. Methods to evaluate lepton isolation e ciency after trigger selection are described below. Additional lepton identi cation quality criteria are required to reduce the contribution from background events containing other particles misidenti ed as leptons. For electrons these quality requirements [31] combine variables measuring track quality, the association between the track and electromagnetic shower, shower shape, and the likelihood of the electron to originate from a photon. Electrons are identi ed in the boosted H channel using a set of selection criteria with an e ciency of 88% and misidenti cation rate of 7%. In the boosted W channel, two working points are de ned based on a multivariate identi cation algorithm: a tight level with 88% e ciency ( 4% misidenti cation rate) and a loose level with 95% e ciency ( 5% misidenti cation rate). Muons are reconstructed by tting hits in the silicon tracker together with hits in the muon detectors [32]. Identi cation algorithms consider the quality of this t, the number or fraction of valid hits in the trackers and muon detectors, track kinks, and the minimum distance between the extrapolated track from the silicon tracker and the primary interaction vertex. Several working points are de ned: the boosted W channel uses so-called \tight" (\loose") muons with 97% (100%) e ciency in the barrel region, and the boosted H channel uses \medium" muons with 99% e ciency in the barrel region. All muon identi cation working points have hadron misidenti cation rates of <1%. Leptons that pass the requirements in the two channels are removed from jets that have an angular separation of R < 0:4 from the lepton. This is done by matching PF { 6 { candidates identi ed as leptons to the ones identi ed as jets and subtracting the fourmomentum of a matched lepton candidate from the jet four-momentum. In order to reduce the rate of background events that contain a soft lepton (e.g., from semileptonic bottom quark decays in multijet events), several metrics can be used to evaluate the isolation of a lepton from surrounding particles. In the boosted H channel, either an angular separation of R(`; j) > 0:4, or prTel(`; j) > 40 GeV is required. Here, ` denotes the highest pT lepton, j is the jet closest to that lepton in angular separation, and prTel(`; j) is the projection of the lepton momentum on the direction perpendicular to the jet momentum in the `-j plane. These criteria, also referred to as \2D isolation", ensure a high signal e ciency for decays such as T ! tH, with leptons produced close to jets, while rejecting a large fraction of the multijet background. In the boosted W channel, where fewer leptons with nearby b quarks are expected, isolation is evaluated using mini-isolation (Imini), de ned as the sum of the transverse momenta of PF candidates within a pT-dependent cone around the lepton, corrected for the e ects of pileup and divided by the lepton pT. The radius of the isolation cone, RI , is de ned as: RI = 10 GeV min(max(pT; 50 GeV); 200 GeV) : (4.1) Using a pT-dependent cone size allows for greater e ciency at high energies where jets and leptons are more likely to overlap. \Tight" electrons (muons) must have Imini < 0:1 (0:2) while \loose" electrons and muons satisfy Imini < 0:4. In addition, the 2D isolation requirement is applied to remove any residual overlap between mini-isolated leptons and jets. Scale factors that account for selection e ciency di erences between data and simulation are calculated as a function of lepton pT and using a \tag-and-probe" method [31, 32, 59]. These were calculated in separate measurements for the single-lepton trigger, lepton identi cation, and Imini requirements. These scale factors are applied to simulated events for both lepton avors. For the 2D isolation requirement, no signi cant di erence is found between the selection e ciencies in data and simulation and hence no scale factor is applied. 4.2 Hadronic W and H tagging In the decay of a heavy T quark, particles are produced with high momentum and large Lorentz boost. The decay products of top quarks and W, Z, or Higgs bosons are therefore often collimated. This can be seen in gure 2 in which the angular separation R between the products of simulated W ! qq0 and H ! bb decays are shown for several T quark masses. Even for the lightest considered mass point this separation often has values of R < 0:8, where the decay products of heavy bosons can merge into a single AK8 jet. A jet shape variable called \N -subjettiness" [60], denoted as N , is de ned as the sum of the transverse momenta of k constituent particles weighted by their minimum angular separation from one of N subjet candidates ( RN;k), which are in a jet of characteristic { 7 { HJEP1(207)85 n n CMS (right) decay processes for three di erent mass points of the T quark. Even for the lowest mass point shown, the nal state particles are typically emitted with a separation of R < 0:8 and are HJEP1(207)85 This variable quanti es the consistency of a jet with originating from an N -prong particle decay. The ratio 2= 1 provides high sensitivity to two-prong decays such as W ! qq0. Jet grooming techniques (\pruning" and \soft drop") are used to remove soft and wide-angle radiation so that the mass of the hard constituents can be measured more precisely [61, 62]. The pruning procedure reclusters the jet, removing soft or large-angle particles, while the soft drop algorithm recursively declusters the jet, removing sub-clusters until two subjets are identi ed within the AK8 jet. AK8 jets are reconstructed independently of AK4 jets, so they will frequently overlap. Unless otherwise stated, such overlapping jets are not removed when applying selections based on jet multiplicity. The AK4 jets and subjets of AK8 jets can be tagged as originating from b quarks based on information about secondary vertices and displaced tracks within the jet. The e ciency for tagging b hadron jets in simulation is approximately 65%, averaged over jet pT (slightly lower for subjets of AK8 jets), and the probability of mistagging a charm (light) quark jet is 13% (1%) [63]. Scale factors, which are functions of jet pT and avor, are applied to account for e ciency di erences between data and simulation. An AK8 jet is labeled as \W tagged" if it has pT > 200 GeV, j j < 2:4, pruned jet mass between 65 and 105 GeV, and the ratio 2= 1 < 0:6. Di erences in the pruned jet mass distribution and 2= 1 selection e ciency between data and simulation have been evaluated in ref. [64]. To account for these di erences, pruned jet mass scale factors and mass resolution smearing factors are applied in simulation to all AK8 jets. A 2= 1 selection scale factor is applied in simulation to jets that are spatially matched to true boosted products of a hadronic W boson decay. Higgs boson candidate jets are reconstructed by exploiting the signi cant branching fraction of the Higgs boson to bb pairs. AK8 jets are marked as \H tagged" if they have pT > 300 GeV, soft drop jet mass in the range 60{160 GeV, and if at least one of the two subjets from the soft drop algorithm is tagged as a bottom subjet. { 8 { 5.1 Boosted H channel Event selection and categorization In this channel, one electron with pT > 50 GeV and j j < 2:4, or one muon with pT > 47 GeV and j j < 2:1 is required. In events with an electron, at least one AK4 jet with pT > 250 GeV and a second AK4 jet with pT > 70 GeV are required to select events with a nearly constant trigger e ciency. Furthermore, selected events must have ST > 800 GeV, at least three AK4 jets, and at least two AK8 jets, since we expect a hadronic decay of a boosted Higgs boson in each event along with at least one other hadronic t quark, W, Z, or further Higgs boson decay. For the rejection of non top quark backgrounds, at least one b-tagged AK4 jet is required. Distributions of the variables used in the H-tagging algorithm, as described in section 4, are shown in gure 3. These distributions are from events that pass all selection criteria outlined above except for the b-tagging requirement, and that have the corrections described in section 5.2 applied. The distribution of the number of b-tagged subjets for the highest pT AK8 jet with soft drop jet mass within 60{160 GeV is shown along with the mass of the highest pT AK8 jet with two b-tagged subjets, before the mass requirement. To illustrate the sensitivity of the H-tagging algorithm to the presence of boosted Higgs bosons, the TT signal with a mass of 1200 GeV is split into two curves: the solid curve shows TT events where at least one Higgs boson is present in the decay chain and the dashed curve shows TT events with only T ! tZ or T ! bW decays. It can be seen that signal events with at least one T ! tH decay produce a clear peak at 125 GeV in the mass distribution of the H-tagged jet. Signal events without a Higgs boson in the decay chain have a less pronounced increase at 90 GeV because of hadronic Z boson decays. After passing the selection de ned above, events are split into two exclusive categories, which depend on the number of b-tagged subjets of H-tagged jets, and are de ned as follows: H2b: events with at least one H-tagged jet with exactly two b-tagged subjets. H1b: events with at least one H-tagged jet with exactly one b-tagged subjet. To avoid an overlap between the two categories, any event is rst checked whether it falls into the H2b category and only if it does not, it can enter into the H1b category. 5.2 Background modeling To evaluate the modeling of tt and W + jets production, the dominant background processes, two control regions that are enriched in events from these processes are de ned by modifying the event selection de ned in section 5.1. In the tt control region, at least two b-tagged jets are required instead of at least one. In the W + jets control region, the requirement of at least one b-tagged jet is inverted and events with any b-tagged jets are rejected. Events with an H-tagged jet are rejected in both control regions to reduce the signal contribution in these regions, and ETmiss > 100 GeV is required to reject events from multijet production. The signal to background ratio is about six times smaller than the one in the H2b category in the tt control region and about 30 times smaller in the W + jets { 9 { HJEP1(207)85 )kg .ve 1 b Data TOP EW QCD TT (MT=0.8 TeV)→ tH+X TT (MT=0.8 TeV)→ other TOP EW QCD with pT > 300 GeV and Mjet in the range [60, 160] GeV (left), and Mjet of the highest pT H-tagged jet candidate with pT > 300 GeV and two subjet b tags (right). A T quark signal with M(T) = 0.8 TeV is shown (right), normalized to the predicted cross section and scaled by a factor of 20, with the singlet benchmark branching fractions assumed. The solid (dashed) curve shows TT events with at least one (zero) Higgs boson decay, where contributions from each decay mode are weighted to re ect the singlet branching fraction scenario. The uncertainty in the background includes the statistical and systematic uncertainties described in section 7. control region. Events are corrected for all known sources of discrepancies between the data and simulation such as di ering reconstruction or tagging e ciencies. It is observed that jets have a harder pT spectrum in simulation, leading to signi cant discrepancies from observed distributions of quantities such as HT. The discrepancies in both control regions are well described by 2-parameter linear ts with negative slopes to the ratio between data and simulation in the HT distributions [65, 66]. Modeling of the tt and W + jets background samples is corrected using the results of these ts. The ST distributions for both control regions are shown in gure 4 with all corrections applied. To evaluate the uncertainty in the normalization of the tt and W + jets background processes, a binned maximum likelihood t [ 67 ] of the background-only hypothesis is performed in the two control regions using the Theta framework [ 68 ]. All systematic uncertainties (discussed in more detail in section 7) are accounted for, except for uncertainties in the rate of tt and W + jets backgrounds that are constrained using this t. The resulting uncertainties in the normalizations of the two backgrounds are 8.7% for tt and 6% for W + jets. These uncertainties are included in the nal statistical interpretation of the results (discussed in section 8) as rate uncertainties. In both control regions, data and simulation agree within the systematic uncertainties described in section 7. 6 6.1 Boosted W channel Event selection The selection in this channel is optimized for the identi cation of boosted W boson decays. Selected events are required to have no H-tagged jets ensuring that the event sample in this 0G105 0 /1103 s t Data TTTT ((MMTT==01..82 TTeeVV)) TOP EW QCD Data TTTT ((MMTT==01..82 TTeeVV)) TOP EW QCD 0eG106 for T quark masses of 0.8 and 1.2 TeV, is normalized to the theoretical cross section and the singlet benchmark branching fractions are assumed. The uncertainty in the background includes statistical and systematic uncertainties described in section 7. channel is complementary to that for the boosted Higgs channel, allowing a straightforward combination of the two channels. Events are selected that have one electron or muon, usually from the decay of a W boson in the T ! bW decay mode or from a leptonic top quark decay in the T ! tZ or tH decay modes. Electrons (muons) must have pT > 40 GeV, j j < 2:1 (2:4) and pass the tight identi cation and isolation requirements described in section 4. Events having additional loose electrons or muons with pT > 10 GeV are rejected. Each event must have three or more AK4 jets, and the three highest pT jets must satisfy pT > 300, 150, and 100 GeV, respectively. Since a neutrino is expected from a leptonic W boson decay, ETmiss is required to be greater than 75 GeV, which also signi cantly reduces the background from multijet events. Control regions are separated from the signal region based on the angular separation between the lepton and the second-highest pT jet in the event, R(`; j2). In both TT and background processes, the lepton is usually observed back-to-back with the highest transverse momentum AK4 jet, and in TT events the secondhighest pT jet also tends to be back-to-back with the lepton, as seen in gure 5. The signal region selection requires R(`; j2) > 1. Figure 5 shows the distribution of R(`; j2) after all selection requirements except for R(`; j2) > 1. All selection e ciency corrections for di erences between data and simulation are applied, as well as the HT-based reweighting described in section 5.2. To maximize sensitivity to the presence of TT production, events are divided into 16 categories based on lepton avor (e, ), the number of b-tagged jets (0, 1, 2, 3), and the number of boosted W-tagged jets (0, 1). In events with no W-tagged jet, we require a fourth jet with pT > 30 GeV. Figure 6 shows the distributions used for tagging boosted W bosons as well as the number of b-tagged and W-tagged jets. The pruned mass distribution for AK8 jets with 2= 1 < 0:6 shows a signi cant contribution of boosted W bosons in signal events weighted to correspond to the singlet branching fraction benchmark. The 2= 1 distribution in AK8 jets with pruned mass between 65{105 GeV shows that W + jets TOP EW QCD R(`; j2) in the boosted W channel after all selection requirements except for R(`; j2) > 1. Also shown are the distributions of TT signal events with T quark masses of 0.8 and 1.2 TeV, scaled by factors of 20 and 60, respectively. The uncertainty in the background includes the statistical and systematic uncertainties described in section 7. and multijet backgrounds are concentrated at higher values, as expected for jets without substructure. We nally analyze the minimum mass constructed from the lepton (`) and a b-tagged AK4 jet, labeled min[M (`; b)]. In leptonic top quark decays, forming a mass from two of the three decay products, the lepton and b quark jet, produces a sharp edge near the top quark mass. Therefore this distribution is particularly suited to identifying T ! bW decays, where the corresponding edge forms at much higher masses, near M(T). In the categories with zero b-tagged AK4 jets, we consider the minimum mass of the lepton and any AK4 jet, denoted min[M (`; j)]. This combination of discriminating variables provides the best sensitivity to low mass T quark production (.1 TeV) in the singlet branching fraction scenario. Figure 7 shows distributions of min[M (`; j)] and min[M (`; b)] after the nal selection but before the likelihood ts described in section 8. 6.2 Background modeling To cross check the modeling of background processes, we consider two control regions enriched by two dominant background processes, W + jets and tt. To de ne these regions we invert the signal region requirement of R(`; j2) > 1 and modify the requirement on the number of b-tagged jets to maximize either W + jets or tt yield. For an 800 GeV T quark we expect only 3 events in both control regions compared to a total background of 444, for a signal to background ratio that is a factor of 3 smaller than in the signal region. The W + jets control region has zero b-tagged jets and events are categorized according to the number of W-tagged jets (0, 1). The tt region has one or more b-tagged jets and events are categorized according to the number of b-tagged jets (1, 2). Figure 8 shows distributions of min[M (`; j)] in the W + jets control region and min[M (`; b)] in the tt control region. Both regions show that simulation-based background predictions agree with data within the systematic uncertainties described in section 7. Observed and predicted TOP EW QCD TOP EW QCD 0:6, 2= 1 for AK8 jets with pruned mass within 65{105 GeV, number of b-tagged AK4 jets, and number of W-tagged AK8 jets in the boosted W channel with all categories combined. Also shown are the distributions of TT signal events with T quark masses of 0.8 and 1.2 TeV, scaled by factors of 20 and 60, respectively, in the upper gures. The uncertainty in the background includes the statistical and systematic uncertainties described in section 7. event yields in the control regions for all categories are compared as a closure test, and di erences in yields are assigned as an additional systematic uncertainty. This uncertainty accounts for any background mismodeling after selection and scale factor application. 7 Systematic uncertainties We consider sources of systematic uncertainty that can a ect the normalization and/or the shape of both background and signal distributions. A summary of these systematic uncertainties along with their numerical values and whether they are applied to signal or background samples can be found in table 2. The uncertainty in the integrated luminosity is 2.3% [69] and is applied to all simulated samples. Normalization uncertainties in the rates of SM processes include 20% for single top quark production and 15% for diboson production, based on CMS measureeV180 CMS 0G160 2 TOP EW QCD TOP EW QCD Distributions of min[M (`; j)] in events without b-tagged AK4 jets (left) and min[M (`; b)] in events with 1 b-tagged AK4 jets (right) in the boosted W channel with all categories combined. Also shown are the distributions of TT signal events with T quark masses of 0.8 and 1.2 TeV, scaled by factors of 20 and 60, respectively. The uncertainty in the background includes the statistical and systematic uncertainties described in section 7. ments [70, 71]. For multijet production a rate uncertainty of 100% is assigned in the boosted H channel since the simulation used in this channel does not contain either the PDF or matrix element scale uncertainties, unlike those used in the boosted W channel. No rate uncertainty is applied to Z + jets production since for this process experimental and theoretical uncertainties are small compared to the energy scale and PDF uncertainties described below. Additionally, both channels derive normalization uncertainties for tt and W + jets samples from control regions, with values of 5{12% and 4{20% in the boosted W channel, and 8.7% and 6.0% in the boosted H channel. Trigger, lepton identi cation, and lepton isolation e ciency scale factor uncertainties are also applied as normalization uncertainties. Uncertainties in both channels a ecting the shape and normalization of the distributions include uncertainties related to jet energy scale, jet energy resolution, pruned or soft drop jet mass scale and resolution, and b tagging and light- avor mistagging e ciencies. These are evaluated by raising and lowering their values with respect to the central values by one standard deviation of the respective uncertainties and recreating a distribution using shifted values at each step of the analysis. An additional uncertainty of 5% is applied in the boosted H channel to account for potential di erences when propagating the jet mass scale and resolution scale factors, measured using hadronic W boson decays, to Higgs boson candidate jets. This uncertainty has been determined by comparing samples simulated with the pythia 8 and herwig++ [72] (with the CUETP8M1 tune [53, 54]) hadronization programs and evaluating the di erence between the two programs in the jet mass distributions for hadronically decaying W and Higgs bosons. In the boosted W channel we also apply shape uncertainties to the W boson tagging corrections for the 2/ 1 selection e ciency and its pT dependence. To account for small di erences in the H-tagging e ciency between the boosted W and boosted H channel, a 3% normalization uncertainty TOP EW QCD Bkg uncert. TOP EW QCD Bkg uncert. (upper) for 0/ 1 W tag categories (left/right), and min[M (`; b)] in the tt control region of the boosted W channel (lower) for 1/ 2 b tag categories (left/right). Also shown are the distributions of TT signal events with T quark masses of 0.8 and 1.2 TeV. The uncertainty in the background includes the statistical and systematic uncertainties described in section 7. is assigned that is correlated with the b tagging uncertainty in the boosted H channel and anticorrelated in the boosted W channel. The uncertainty due to pileup modeling is evaluated by varying by 5% the total inelastic cross section used to calculate the pileup distribution. The systematic uncertainty in the HT-based background reweighting procedure is taken to be the di erence between the unweighted distribution and a distribution where the correction factor is applied twice. The uncertainties in the PDFs used in MC simulation are evaluated from the set of NNPDF3.0 tted replicas, following the standard procedure [55]. Renormalization and factorization scale uncertainties are calculated by varying the corresponding scales up or down (either independently or simultaneously) by a factor of two and taking as uncertainty the envelope, or largest spread, of all possible variations. These theoretical uncertainties are applied to the signal simulation as shape uncertainties, together with small normalization uncertainty contributions due to changes in acceptance. The PDF and scale variation uncertainties a ect both the normalization and shape of background distributions for multijet (in the boosted W channel), Z + jets, and single top quark MC samples. For the tt and W + jets backgrounds the theoretical and HT reweighting uncertainties dominate the total uncertainty in this search, and theoretical uncertainties are treated di erently across the two channels. Changes of energy scale or parton momentum strongly in uence HT and therefore these uncertainties are correlated with the uncertainty in the HT reweighting method. In the boosted H channel, only the uncertainty in the HT reweighting procedure is considered as this uncertainty dominates over energy scale variations and PDF uncertainties, especially in the tails of the ST distribution. In the boosted W channel the uncertainty in the HT reweighting dominates over the PDF uncertainty, but is comparable in shape and magnitude to the scale variation uncertainty, with scale variations providing the dominant uncertainty at low values of min[M (`; b)]. In this channel both HT reweighting and scale variation uncertainties are considered for tt and W + jets backgrounds. All of these shared uncertainties are treated as correlated between the two analysis channels in the statistical interpretation of the results. 8 Results Signal e ciencies for all possible nal states of TT and BB production in the boosted W and boosted H channels (after combining all categories in each channel) are listed in table 3 for two signal hypotheses with a high and a low vector-like quark mass. The values are derived by dividing the number of signal events that have the corresponding decay mode in each category by the number of expected events in the same decay mode before any selection. It can be seen that the selection applied in the boosted H channel is most e cient if a Higgs boson is present in the nal state, whereas the selection in the boosted W channel favors T ! bW decays, thus showing how the combination of the two channels improves sensitivity to most branching fraction combinations of the T quark. For B quark decays the boosted W channel has high e ciency for the tW decays and reduced e ciency for the bZ/bH decays owing to the lack of semileptonic top quark decays. Similarly, the boosted H channel is most e cient for the bHtW nal state since a leptonic decay is required as well as an H-tag. In gure 9, min[M (`; j)] or min[M (`; b)] distributions are shown for each of the 8 tagging categories in the boosted W channel after the nal event selection, with the electron and muon channels combined. Figure 10 shows distributions of ST in the H1b and H2b categories after combining the electron and muon channels. As these two variables provide good discrimination between signal and background in their respective categories, they are used for the nal statistical interpretation of the data. In all plots, the TT signal distributions assume the singlet benchmark branching fractions. The event yields are given in table 4. After the nal event selection, no signi cant excess above the SM expectations is observed in data. We set 95% CL upper limits on the cross section of TT production in various branching fraction scenarios. These limits are de ned as Bayesian credible intervals [ 67 ] and are derived using the Theta [ 68 ] program. Statistical uncertainties due to the nite size of the MC samples are accounted for using the Barlow-Beeston lite method [73]. Systematic uncertainties are treated as nuisance parameters with log-normal priors for norSource Int. luminosity Diboson rate Single t quark rate QCD rate tt rate W + jets rate Trigger (e) Trigger ( ) Identi cation (e, ) Isolation (e, ) Pileup Jet energy scale Jet energy res. HT reweighting b tag: b b tag: light avors W/H tag: mass scale W/H tag: mass res. H tag: e ciency H tag: propagation W tag: 2= 1 W tag: 2= 1 pT Renorm./fact. scale PDF | 5{12% 4{20% 5% 5% 1% 1% to signal and/or background samples. The second column gives the magnitude of normalization uncertainties or the procedure used to evaluate shape uncertainties. The symbol indicates one standard deviation of the corresponding systematic uncertainty. Renormalization and factorization energy scale uncertainties are treated as shape-only for signal but include normalization uncertainties in background. Values stated for shape uncertainties indicate a representative range over the categories for the dominant backgrounds and/or signal. malization uncertainties, Gaussian priors for shape uncertainties with shifted templates, and a at prior on the signal cross section. The limits are then calculated by simultaneously tting the binned marginal likelihoods obtained from the min[M (`; b)] distributions in all boosted W categories and the ST distributions in all boosted H categories. This creates a combined search with 20 categories after dividing into electron and muon channels: 16 categories from the boosted W channel and 4 categories with a boosted Higgs boson. The systematic uncertainties for these categories are correlated, as described in section 7. Results for the individual channels are shown in gure 11. The boosted W channel excludes T quarks decaying only to bW with masses below 910 GeV (870 GeV expected), and the boosted H channel excludes T quarks decaying only to tH for masses below 890 GeV (860 GeV expected). In gure 12 we present combined 95% CL upper limits on the TT production cross section for two VLQ benchmark branching fraction combinations: singlet (50% bW, 25% tZ/tH) and doublet (50% tZ/tH). For an electroweak singlet T quark, All diboson QCD W + jets t tt All All All | All (0{3%) All (0{4)% All (0{1)% tt, W + jets (13{21%) All (3{8%) All (1{4%) All (0{7%) All (0{7%) All All | | Production process Decay mode Boosted W categories Boosted H categories TT (0.8 TeV) TT (1.2 TeV) BB (0.8 TeV) BB (1.2 TeV) tHtH tHtZ tHbW tZtZ tZbW bWbW tHtH tHtZ tHbW tZtZ tZbW bWbW bHbH bHbZ bHtW bZbZ bZtW tWtW bHbH bHbZ bHtW bZbZ bZtW tWtW 13:2% 10:0% 2:9% 3:2% 5:8% 3:7% 6:3% 3:6% 4:1% 7:3% 4:7% 8:3% 1:7% 1:3% 5:8% 0:8% 6:4% 7:9% 1:7% 1:4% 7:3% 0:8% 8:2% 11:4% 10:5% 8:7% 7:3% 6:3% 5:6% 4:2% 2:5% 9:0% 7:1% 6:7% 4:8% 2:5% 1:9% 1:9% 6:1% 1:4% 4:2% 5:7% 2:1% 1:9% 7:1% 1:5% 4:7% 7:0% nal states, of both TT and BB production for two illustrative mass points. E ciencies are calculated with respect to the expected number of events in the corresponding nal state before any selection. The relative uncertainty in the e ciencies after combining systematic and statistical uncertainties in the MC samples is about 8% in the boosted W categories and about 12% in the boosted H categories. the observed (expected) upper limits on the production cross section range from 0.26 to 0.04 pb (0.31 to 0.04 pb) and we exclude masses below 860 GeV (790 GeV). For a doublet T quark, the observed (expected) upper limits on the production cross section range from 0.37 to 0.04 pb (0.34 to 0.03 pb) and we exclude masses below 830 GeV (780 GeV). The corresponding benchmarks for B quark production are shown in gure 13, and we can exclude masses below 730 GeV (720 GeV expected) for the singlet branching fraction combination while for the doublet scenario, no lower mass limit above 700 GeV was observed. Sensitivity to BB production in this search is limited by the single lepton selection e ciency for bZ and bH decays, as noted above. The combinations bene t from the di erence in discriminating variables between the channels: the min[M(`,b)] distributions used in the 1>02 V /ts10 vE 1 10−1 10−2 10−3 10−3 10−2 10−3 TOP EW QCD Data channels in the boosted W categories with 0 (left) or 1 (right) W-tagged jets and (upper to lower) 0, 1, 2, or 3 b-tagged jets. Also shown are the distributions of TT signal events with T quark masses of 0.8 and 1.2 TeV. The uncertainty in the background includes the statistical and systematic uncertainties described in section 7. 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Kadastik, L. Perrini, M. Raidal, A. Tiko, C. Veelken Department of Physics, University of Helsinki, Helsinki, Finland P. Eerola, J. Pekkanen, M. Voutilainen Helsinki Institute of Physics, Helsinki, Finland J. Harkonen, T. Jarvinen, V. Karimaki, R. Kinnunen, T. Lampen, K. Lassila-Perini, S. Lehti, T. Linden, P. Luukka, E. Tuominen, J. Tuominiemi, E. Tuovinen Lappeenranta University of Technology, Lappeenranta, Finland J. Talvitie, T. Tuuva IRFU, CEA, Universite Paris-Saclay, Gif-sur-Yvette, France M. Besancon, F. Couderc, M. Dejardin, D. Denegri, J.L. Faure, F. Ferri, S. Ganjour, S. Ghosh, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, I. Kucher, E. Locci, M. Machet, J. Malcles, G. Negro, J. Rander, A. Rosowsky, M.O . Sahin, M. Titov Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Universite Paris-Saclay, Palaiseau, France A. Abdulsalam, I. Antropov, S. Ba oni, F. Beaudette, P. Busson, L. Cadamuro, C. Charlot, O. Davignon, R. Granier de Cassagnac, M. Jo, S. Lisniak, A. Lobanov, J. Martin Blanco, M. Nguyen, C. Ochando, G. Ortona, P. Paganini, P. Pigard, S. Regnard, R. Salerno, J.B. Sauvan, Y. Sirois, A.G. Stahl Leiton, T. Strebler, Y. Yilmaz, A. Zabi, A. Zghiche Universite de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France S. Gadrat J.-L. Agram12, J. Andrea, D. Bloch, J.-M. Brom, M. Buttignol, E.C. Chabert, N. Chanon, C. Collard, E. Conte12, X. Coubez, J.-C. Fontaine12, D. Gele, U. Goerlach, M. Jansova, A.-C. Le Bihan, P. Van Hove Centre de Calcul de l'Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3, Villeurbanne, France Universite de Lyon, Universite Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucleaire de Lyon, Villeurbanne, France S. Beauceron, C. Bernet, G. Boudoul, R. Chierici, D. Contardo, P. Depasse, H. El Mamouni, J. Fay, L. Finco, S. Gascon, M. Gouzevitch, G. Grenier, B. Ille, F. Lagarde, I.B. Laktineh, M. Lethuillier, L. Mirabito, A.L. Pequegnot, S. Perries, A. Popov13, V. Sordini, M. Vander Donckt, S. Viret A. Khvedelidze6 I. Bagaturia14 Georgian Technical University, Tbilisi, Georgia Tbilisi State University, Tbilisi, Georgia RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany C. Autermann, S. Beranek, L. Feld, M.K. Kiesel, K. Klein, M. Lipinski, M. Preuten, C. Schomakers, J. Schulz, T. Verlage RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany A. Albert, M. Brodski, E. Dietz-Laursonn, D. Duchardt, M. Endres, M. Erdmann, S. Erdweg, T. Esch, R. Fischer, A. Guth, M. Hamer, T. Hebbeker, C. Heidemann, K. Hoepfner, S. Knutzen, M. Merschmeyer, A. Meyer, P. Millet, S. Mukherjee, M. Olschewski, K. Padeken, T. Pook, M. Radziej, H. Reithler, M. Rieger, F. Scheuch, D. Teyssier, S. Thuer RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany G. Flugge, B. Kargoll, T. Kress, A. Kunsken, J. Lingemann, T. Muller, A. Nehrkorn, A. Nowack, C. Pistone, O. Pooth, A. Stahl15 Deutsches Elektronen-Synchrotron, Hamburg, Germany M. Aldaya Martin, T. Arndt, C. Asawatangtrakuldee, K. Beernaert, O. Behnke, U. Behrens, A.A. Bin Anuar, K. Borras16, V. Botta, A. Campbell, P. Connor, C. ContrerasCampana, F. Costanza, C. Diez Pardos, G. Eckerlin, D. Eckstein, T. Eichhorn, E. Eren, E. Gallo17, J. Garay Garcia, A. Geiser, A. Gizhko, J.M. Grados Luyando, A. Grohsjean, P. Gunnellini, A. Harb, J. Hauk, M. Hempel18, H. Jung, A. Kalogeropoulos, M. Kasemann, J. Keaveney, C. Kleinwort, I. Korol, D. Krucker, W. Lange, A. Lelek, T. Lenz, J. Leonard, K. Lipka, W. Lohmann18, R. Mankel, I.-A. Melzer-Pellmann, A.B. Meyer, G. Mittag, J. Mnich, A. Mussgiller, E. Ntomari, D. Pitzl, R. Placakyte, A. Raspereza, B. Roland, M. Savitskyi, P. Saxena, R. Shevchenko, S. Spannagel, N. Stefaniuk, G.P. Van Onsem, R. Walsh, Y. Wen, K. Wichmann, C. Wissing, O. Zenaiev University of Hamburg, Hamburg, Germany S. Bein, V. Blobel, M. Centis Vignali, A.R. Draeger, T. Dreyer, E. Garutti, D. Gonzalez, J. Haller, M. Ho mann, A. Junkes, A. Karavdina, R. Klanner, R. Kogler, N. Kovalchuk, S. Kurz, T. Lapsien, I. Marchesini, D. Marconi, M. Meyer, M. Niedziela, D. Nowatschin, F. Pantaleo15, T. Pei er, A. Perieanu, C. Scharf, P. Schleper, A. Schmidt, S. Schumann, J. Schwandt, J. Sonneveld, H. Stadie, G. Steinbruck, F.M. Stober, M. Stover, H. Tholen, D. Troendle, E. Usai, L. Vanelderen, A. Vanhoefer, B. Vormwald Institut fur Experimentelle Kernphysik, Karlsruhe, Germany M. Akbiyik, C. Barth, S. Baur, E. Butz, R. Caspart, T. Chwalek, F. Colombo, W. De Boer, A. Dierlamm, B. Freund, R. Friese, M. Gi els, A. Gilbert, D. Haitz, F. Hartmann15, S.M. Heindl, U. Husemann, F. Kassel15, S. Kudella, H. Mildner, M.U. Mozer, Th. Muller, M. Plagge, G. Quast, K. Rabbertz, M. Schroder, I. Shvetsov, G. Sieber, H.J. Simonis, R. Ulrich, S. Wayand, M. Weber, T. Weiler, S. Williamson, C. Wohrmann, R. Wolf Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece I. Topsis-Giotis G. Anagnostou, G. Daskalakis, T. Geralis, V.A. Giakoumopoulou, A. Kyriakis, D. Loukas, National and Kapodistrian University of Athens, Athens, Greece S. Kesisoglou, A. Panagiotou, N. Saoulidou University of Ioannina, Ioannina, Greece I. Evangelou, C. Foudas, P. Kokkas, N. Manthos, I. Papadopoulos, E. Paradas, J. Strologas, F.A. Triantis MTA-ELTE Lendulet CMS Particle and Nuclear Physics Group, Eotvos Lorand University, Budapest, Hungary M. Csanad, N. Filipovic, G. Pasztor G. Bencze, C. Hajdu, G. Vesztergombi20, A.J. Zsigmond Wigner Research Centre for Physics, Budapest, Hungary Institute of Nuclear Research ATOMKI, Debrecen, Hungary N. Beni, S. Czellar, J. Karancsi21, A. Makovec, J. Molnar, Z. Szillasi Institute of Physics, University of Debrecen, Debrecen, Hungary M. Bartok20, P. Raics, Z.L. Trocsanyi, B. Ujvari Indian Institute of Science (IISc), Bangalore, India S. Choudhury, J.R. Komaragiri D. Horvath19, A. Hunyadi, F. Sikler, V. Veszpremi, National Institute of Science Education and Research, Bhubaneswar, India S. Bahinipati22, S. Bhowmik, P. Mal, K. Mandal, A. Nayak23, D.K. Sahoo22, N. Sahoo, S.K. Swain Panjab University, Chandigarh, India S. Bansal, S.B. Beri, V. Bhatnagar, U. Bhawandeep, R. Chawla, N. Dhingra, A.K. Kalsi, A. Kaur, M. Kaur, R. Kumar, P. Kumari, A. Mehta, J.B. Singh, G. Walia University of Delhi, Delhi, India Ashok Kumar, Aashaq Shah, A. Bhardwaj, S. Chauhan, B.C. Choudhary, R.B. Garg, S. Keshri, A. Kumar, S. Malhotra, M. Naimuddin, K. Ranjan, R. Sharma, V. Sharma Saha Institute of Nuclear Physics, HBNI, Kolkata, India R. Bhardwaj, R. Bhattacharya, S. Bhattacharya, S. Dey, S. Dutt, S. Dutta, S. Ghosh, N. Majumdar, A. Modak, K. Mondal, S. Mukhopadhyay, S. Nandan, A. Purohit, A. Roy, D. Roy, S. Roy Chowdhury, S. Sarkar, M. Sharan, S. Thakur Indian Institute of Technology Madras, Madras, India P.K. Behera Bhabha Atomic Research Centre, Mumbai, India R. Chudasama, D. Dutta, V. Jha, V. Kumar, A.K. Mohanty15, P.K. Netrakanti, L.M. Pant, HJEP1(207)85 P. Shukla, A. Topkar Tata Institute of Fundamental Research-A, Mumbai, India T. Aziz, S. Dugad, B. Mahakud, S. Mitra, G.B. Mohanty, B. Parida, N. Sur, B. Sutar Tata Institute of Fundamental Research-B, Mumbai, India S. Banerjee, S. Bhattacharya, S. Chatterjee, P. Das, M. Guchait, Sa. Jain, S. Kumar, M. Maity24, G. Majumder, K. Mazumdar, T. Sarkar24, N. Wickramage25 Indian Institute of Science Education and Research (IISER), Pune, India S. Chauhan, S. Dube, V. Hegde, A. Kapoor, K. Kothekar, S. Pandey, A. Rane, S. Sharma Institute for Research in Fundamental Sciences (IPM), Tehran, Iran S. Chenarani26, E. Eskandari Tadavani, S.M. Etesami26, M. Khakzad, M. Mohammadi Najafabadi, M. Naseri, S. Paktinat Mehdiabadi27, F. Rezaei Hosseinabadi, B. Safarzadeh28, M. Zeinali University College Dublin, Dublin, Ireland M. Felcini, M. Grunewald INFN Sezione di Bari a, Universita di Bari b, Politecnico di Bari c, Bari, Italy M. Abbresciaa;b, C. Calabriaa;b, C. Caputoa;b, A. Colaleoa, D. Creanzaa;c, L. Cristellaa;b, N. De Filippisa;c, M. De Palmaa;b, F. Erricoa;b, L. Fiorea, G. Iasellia;c, G. Maggia;c, M. Maggia, G. Minielloa;b, S. Mya;b, S. Nuzzoa;b, A. Pompilia;b, G. Pugliesea;c, R. Radognaa;b, A. Ranieria, G. Selvaggia;b, A. Sharmaa, L. Silvestrisa;15, R. Vendittia, P. Verwilligena INFN Sezione di Bologna a, Universita di Bologna b, Bologna, Italy G. Abbiendia, C. Battilana, D. Bonacorsia;b, S. Braibant-Giacomellia;b, L. Brigliadoria;b, R. Campaninia;b, P. Capiluppia;b, A. Castroa;b, F.R. Cavalloa, S.S. Chhibraa;b, G. Codispotia;b, M. Cu ania;b, G.M. Dallavallea, F. Fabbria, A. Fanfania;b, D. Fasanellaa;b, P. Giacomellia, L. Guiduccia;b, S. Marcellinia, G. Masettia, F.L. Navarriaa;b, A. Perrottaa, A.M. Rossia;b, T. Rovellia;b, G.P. Sirolia;b, N. Tosia;b;15 INFN Sezione di Catania a, Universita di Catania b, Catania, Italy S. Albergoa;b, S. Costaa;b, A. Di Mattiaa, F. Giordanoa;b, R. Potenzaa;b, A. Tricomia;b, C. Tuvea;b INFN Sezione di Firenze a, Universita di Firenze b, Firenze, Italy G. Barbaglia, K. Chatterjeea;b, V. Ciullia;b, C. Civininia, R. D'Alessandroa;b, E. Focardia;b, P. Lenzia;b, M. Meschinia, S. Paolettia, L. Russoa;29, G. Sguazzonia, D. Stroma, L. Viliania;b;15 INFN Laboratori Nazionali di Frascati, Frascati, Italy L. Benussi, S. Bianco, F. Fabbri, D. Piccolo, F. Primavera15 INFN Sezione di Genova a, Universita di Genova b, Genova, Italy V. Calvellia;b, F. Ferroa, E. Robuttia, S. Tosia;b INFN Sezione di Milano-Bicocca a, Universita di Milano-Bicocca b, Milano, Italy L. Brianzaa;b, F. Brivioa;b, V. Cirioloa;b, M.E. Dinardoa;b, S. Fiorendia;b, S. Gennaia, A. Ghezzia;b, P. Govonia;b, M. Malbertia;b, S. Malvezzia, R.A. Manzonia;b, D. Menascea, L. Moronia, M. Paganonia;b, K. Pauwelsa;b, D. Pedrinia, S. Pigazzinia;b;30, S. Ragazzia;b, T. Tabarelli de Fatisa;b INFN Sezione di Napoli a, Universita di Napoli 'Federico II' b, Napoli, Italy, Universita della Basilicata c, Potenza, Italy, Universita G. Marconi d, Roma, Italy F. Thyssena S. Buontempoa, N. Cavalloa;c, S. Di Guidaa;d;15, F. Fabozzia;c, F. Fiengaa;b, A.O.M. Iorioa;b, W.A. Khana, L. Listaa, S. Meolaa;d;15, P. Paoluccia;15, C. Sciaccaa;b, INFN Sezione di Padova a, Universita di Padova b, Padova, Italy, Universita di Trento c, Trento, Italy P. Azzia;15, N. Bacchettaa, L. Benatoa;b, A. Bolettia;b, R. Carlina;b, A. Carvalho Antunes De Oliveiraa;b, P. Checchiaa, M. Dall'Ossoa;b, P. De Castro Manzanoa, T. Dorigoa, U. Dossellia, U. Gasparinia;b, A. Gozzelinoa, S. Lacapraraa, M. Margonia;b, A.T. Meneguzzoa;b, N. Pozzobona;b, P. Ronchesea;b, R. Rossina;b, M. Sgaravattoa, F. Simonettoa;b, E. Torassaa, S. Venturaa, M. Zanettia;b, P. Zottoa;b, G. Zumerlea;b INFN Sezione di Pavia a, Universita di Pavia b, Pavia, Italy A. Braghieria, F. Fallavollitaa;b, A. Magnania;b, P. Montagnaa;b, S.P. Rattia;b, V. Rea, M. Ressegotti, C. Riccardia;b, P. Salvinia, I. Vaia;b, P. Vituloa;b INFN Sezione di Perugia a, Universita di Perugia b, Perugia, Italy L. Alunni Solestizia;b, G.M. Bileia, D. Ciangottinia;b, L. Fanoa;b, P. Laricciaa;b, R. Leonardia;b, G. Mantovania;b, V. Mariania;b, M. Menichellia, A. Sahaa, A. Santocchiaa;b, D. Spiga Pisa c, Pisa, Italy INFN Sezione di Pisa a, Universita di Pisa b, Scuola Normale Superiore di K. Androsova, P. Azzurria;15, G. Bagliesia, J. Bernardinia, T. Boccalia, L. Borrello, R. Castaldia, M.A. Cioccia;b, R. Dell'Orsoa, G. Fedia, L. Gianninia;c, A. Giassia, M.T. Grippoa;29, F. Ligabuea;c, T. Lomtadzea, E. Mancaa;c, G. Mandorlia;c, L. Martinia;b, G. Tonellia;b, A. Venturia, P.G. Verdinia INFN Sezione di Roma a, Sapienza Universita di Roma b, Rome, Italy L. Baronea;b, F. Cavallaria, M. Cipriania;b, D. Del Rea;b;15, M. Diemoza, S. Gellia;b, E. Longoa;b, F. Margarolia;b, Meridiania, R. Paramattia;b, F. Preiatoa;b, S. Rahatloua;b, C. Rovellia, F. Santanastasioa;b INFN Sezione di Torino a, Universita di Torino b, Torino, Italy, Universita del Piemonte Orientale c, Novara, Italy N. Amapanea;b, R. Arcidiaconoa;c;15, S. Argiroa;b, M. Arneodoa;c, N. Bartosika, R. Bellana;b, C. Biinoa, N. Cartigliaa, F. Cennaa;b, M. Costaa;b, R. Covarellia;b, A. Deganoa;b, N. Demariaa, B. Kiania;b, C. Mariottia, S. Masellia, E. Migliorea;b, V. Monacoa;b, E. Monteila;b, M. Montenoa, M.M. Obertinoa;b, L. Pachera;b, N. Pastronea, M. Pelliccionia, G.L. Pinna Angionia;b, F. Raveraa;b, A. Romeroa;b, M. Ruspaa;c, R. Sacchia;b, K. Shchelinaa;b, V. Solaa, A. Solanoa;b, A. Staianoa, P. Traczyka;b INFN Sezione di Trieste a, Universita di Trieste b, Trieste, Italy S. Belfortea, M. Casarsaa, F. Cossuttia, G. Della Riccaa;b, A. Zanettia Kyungpook National University, Daegu, Korea D.H. Kim, G.N. Kim, M.S. Kim, J. Lee, S. Lee, S.W. Lee, Y.D. Oh, S. Sekmen, D.C. Son, Y.C. Yang A. Lee Chonbuk National University, Jeonju, Korea Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea H. Kim, D.H. Moon, G. Oh Hanyang University, Seoul, Korea J.A. Brochero Cifuentes, J. Goh, T.J. Kim Korea University, Seoul, Korea J. Lim, S.K. Park, Y. Roh Seoul National University, Seoul, Korea S. Cho, S. Choi, Y. Go, D. Gyun, S. Ha, B. Hong, Y. Jo, Y. Kim, K. Lee, K.S. Lee, S. Lee, J. Almond, J. Kim, J.S. Kim, H. Lee, K. Lee, K. Nam, S.B. Oh, B.C. Radburn-Smith, S.h. Seo, U.K. Yang, H.D. Yoo, G.B. Yu University of Seoul, Seoul, Korea M. Choi, H. Kim, J.H. Kim, J.S.H. Lee, I.C. Park, G. Ryu Sungkyunkwan University, Suwon, Korea Y. Choi, C. Hwang, J. Lee, I. Yu Vilnius University, Vilnius, Lithuania V. Dudenas, A. Juodagalvis, J. Vaitkus HJEP1(207)85 National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia M.N. Yusli, Z. Zolkapli I. Ahmed, Z.A. Ibrahim, M.A.B. Md Ali32, F. Mohamad Idris33, W.A.T. Wan Abdullah, Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico H. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-De La Cruz34, R. Lopez-Fernandez, J. Mejia Guisao, A. Sanchez-Hernandez Universidad Iberoamericana, Mexico City, Mexico S. Carrillo Moreno, C. Oropeza Barrera, F. Vazquez Valencia Benemerita Universidad Autonoma de Puebla, Puebla, Mexico I. Pedraza, H.A. Salazar Ibarguen, C. Uribe Estrada Universidad Autonoma de San Luis Potos , San Luis Potos , Mexico A. Morelos Pineda University of Auckland, Auckland, New Zealand HJEP1(207)85 D. Krofcheck P.H. Butler M. Waqas University of Canterbury, Christchurch, New Zealand National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan A. Ahmad, M. Ahmad, Q. Hassan, H.R. Hoorani, A. Saddique, M.A. Shah, M. Shoaib, National Centre for Nuclear Research, Swierk, Poland H. Bialkowska, M. Bluj, B. Boimska, T. Frueboes, M. Gorski, M. Kazana, K. Nawrocki, K. Romanowska-Rybinska, M. Szleper, P. Zalewski Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland K. Bunkowski, A. Byszuk35, K. Doroba, A. Kalinowski, M. Konecki, J. Krolikowski, M. Misiura, M. Olszewski, A. Pyskir, M. Walczak Laboratorio de Instrumentac~ao e F sica Experimental de Part culas, Lisboa, Portugal P. Bargassa, C. Beir~ao Da Cruz E Silva, B. Calpas, A. Di Francesco, P. Faccioli, M. Gallinaro, J. Hollar, N. Leonardo, L. Lloret Iglesias, M.V. Nemallapudi, J. Seixas, O. Toldaiev, D. Vadruccio, J. Varela Joint Institute for Nuclear Research, Dubna, Russia S. Afanasiev, P. Bunin, M. Gavrilenko, I. Golutvin, I. Gorbunov, A. Kamenev, V. Karjavin, A. Lanev, A. Malakhov, V. Matveev36;37, V. Palichik, V. Perelygin, S. Shmatov, S. Shulha, N. Skatchkov, V. Smirnov, N. Voytishin, A. Zarubin Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia Y. Ivanov, V. Kim38, E. Kuznetsova39, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev Institute for Nuclear Research, Moscow, Russia Yu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, A. Karneyeu, M. Kirsanov, N. Krasnikov, A. Pashenkov, D. Tlisov, A. Toropin Institute for Theoretical and Experimental Physics, Moscow, Russia V. Epshteyn, V. Gavrilov, N. Lychkovskaya, V. Popov, I. Pozdnyakov, G. Safronov, A. Spiridonov, A. Stepennov, M. Toms, E. Vlasov, A. Zhokin HJEP1(207)85 Moscow Institute of Physics and Technology, Moscow, Russia T. Aushev, A. Bylinkin37 National Research Nuclear University 'Moscow Engineering Physics Institute' (MEPhI), Moscow, Russia R. Chistov40, M. Danilov40, P. Parygin, D. Philippov, S. Polikarpov, E. Tarkovskii P.N. Lebedev Physical Institute, Moscow, Russia V. Andreev, M. Azarkin37, I. Dremin37, M. Kirakosyan37, A. Terkulov Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia V. Savrin A. Baskakov, A. Belyaev, E. Boos, V. Bunichev, M. Dubinin41, L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova, I. Lokhtin, I. Miagkov, S. Obraztsov, M. Per lov, Novosibirsk State University (NSU), Novosibirsk, Russia V. Blinov42, Y.Skovpen42, D. Shtol42 State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia I. Azhgirey, I. Bayshev, S. Bitioukov, D. Elumakhov, V. Kachanov, A. Kalinin, D. Konstantinov, V. Krychkine, V. Petrov, R. Ryutin, A. Sobol, S. Troshin, N. Tyurin, A. Uzunian, A. Volkov University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia P. Adzic43, P. Cirkovic, D. Devetak, M. Dordevic, J. Milosevic, V. Rekovic Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Madrid, Spain J. Alcaraz Maestre, M. Barrio Luna, M. Cerrada, N. Colino, B. De La Cruz, A. Delgado Peris, A. Escalante Del Valle, C. Fernandez Bedoya, J.P. Fernandez Ramos, J. Flix, M.C. Fouz, P. Garcia-Abia, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa, A. Perez-Calero Yzquierdo, J. Puerta Pelayo, A. Quintario Olmeda, I. Redondo, L. Romero, M.S. Soares, A. Alvarez Fernandez Universidad Autonoma de Madrid, Madrid, Spain J.F. de Troconiz, M. Missiroli, D. Moran Universidad de Oviedo, Oviedo, Spain J. Cuevas, C. Erice, J. Fernandez Menendez, I. Gonzalez Caballero, J.R. Gonzalez Fernandez, E. Palencia Cortezon, S. Sanchez Cruz, I. Suarez Andres, P. Vischia, J.M. Vizan Garcia Santander, Spain Instituto de F sica de Cantabria (IFCA), CSIC-Universidad de Cantabria, I.J. Cabrillo, A. Calderon, B. Chazin Quero, E. Curras, M. Fernandez, J. Garcia-Ferrero, G. Gomez, A. Lopez Virto, J. Marco, C. Martinez Rivero, P. Martinez Ruiz del Arbol, F. Matorras, J. Piedra Gomez, T. Rodrigo, A. Ruiz-Jimeno, L. Scodellaro, N. Trevisani, I. Vila, R. Vilar Cortabitarte CERN, European Organization for Nuclear Research, Geneva, Switzerland D. Abbaneo, E. Au ray, P. Baillon, A.H. Ball, D. Barney, M. Bianco, P. Bloch, A. Bocci, C. Botta, T. Camporesi, R. Castello, M. Cepeda, G. Cerminara, E. Chapon, Y. Chen, D. d'Enterria, A. Dabrowski, V. Daponte, A. David, M. De Gruttola, A. De Roeck, E. Di Marco44, M. Dobson, B. Dorney, T. du Pree, M. Dunser, N. Dupont, A. Elliott-Peisert, P. Everaerts, G. Franzoni, J. Fulcher, W. Funk, D. Gigi, K. Gill, F. Glege, D. Gulhan, S. Gundacker, M. Gutho , P. Harris, J. Hegeman, V. Innocente, P. Janot, O. Karacheban18, J. Kieseler, H. Kirschenmann, V. Knunz, A. Kornmayer15, M.J. Kortelainen, C. Lange, P. Lecoq, C. Lourenco, M.T. Lucchini, L. Malgeri, M. Mannelli, A. Martelli, F. Meijers, J.A. Merlin, S. Mersi, E. Meschi, P. Milenovic45, F. Moortgat, M. Mulders, H. Neugebauer, S. Orfanelli, L. Orsini, L. Pape, E. Perez, M. Peruzzi, A. Petrilli, G. Petrucciani, A. Pfei er, M. Pierini, A. Racz, T. Reis, G. Rolandi46, M. Rovere, H. Sakulin, C. Schafer, C. Schwick, M. Seidel, M. Selvaggi, A. Sharma, P. Silva, P. Sphicas47, J. Steggemann, M. Stoye, M. Tosi, D. Treille, A. Triossi, A. Tsirou, V. Veckalns48, G.I. Veres20, M. Verweij, N. Wardle, W.D. Zeuner Paul Scherrer Institut, Villigen, Switzerland W. Bertly, K. Deiters, W. Erdmann, R. Horisberger, Q. Ingram, H.C. Kaestli, D. Kotlinski, U. Langenegger, T. Rohe, S.A. Wiederkehr Institute for Particle Physics, ETH Zurich, Zurich, Switzerland F. Bachmair, L. Bani, P. Berger, L. Bianchini, B. Casal, G. Dissertori, M. Dittmar, M. Donega, C. Grab, C. Heidegger, D. Hits, J. Hoss, G. Kasieczka, T. Klijnsma, W. Lustermann, B. Mangano, M. Marionneau, M.T. Meinhard, D. Meister, F. Micheli, P. Musella, F. Nessi-Tedaldi, F. Pandol , J. Pata, F. Pauss, G. Perrin, L. Perrozzi, M. Quittnat, M. Rossini, M. Schonenberger, L. Shchutska, A. Starodumov49, V.R. Tavolaro, K. Theo latos, M.L. Vesterbacka Olsson, R. Wallny, A. Zagozdzinska35, D.H. Zhu Universitat Zurich, Zurich, Switzerland T.K. Aarrestad, C. Amsler50, L. Caminada, M.F. Canelli, A. De Cosa, S. Donato, C. Galloni, A. Hinzmann, T. Hreus, B. Kilminster, J. Ngadiuba, D. Pinna, G. Rauco, P. Robmann, D. Salerno, C. Seitz, A. Zucchetta National Central University, Chung-Li, Taiwan V. Candelise, T.H. Doan, Sh. Jain, R. Khurana, M. Konyushikhin, C.M. Kuo, W. Lin, A. Pozdnyakov, S.S. Yu National Taiwan University (NTU), Taipei, Taiwan Arun Kumar, P. Chang, Y. Chao, K.F. Chen, P.H. Chen, F. Fiori, W.-S. Hou, Y. Hsiung, Y.F. Liu, R.-S. Lu, M. Min~ano Moya, E. Paganis, A. Psallidas, J.f. Tsai Chulalongkorn University, Faculty of Science, Department of Physics, Bangkok, B. Asavapibhop, K. Kovitanggoon, G. Singh, N. Srimanobhas Cukurova University, Physics Department, Science and Art Faculty, Adana, A. Adiguzel51, F. Boran, S. Damarseckin, Z.S. Demiroglu, C. Dozen, E. Eskut, S. Girgis, G. Gokbulut, Y. Guler, I. Hos52, E.E. Kangal53, O. Kara, A. Kayis Topaksu, U. Kiminsu, M. Oglakci, G. Onengut54, K. Ozdemir55, S. Ozturk56, A. Polatoz, B. Tali57, S. Turkcapar, I.S. Zorbakir, C. Zorbilmez Middle East Technical University, Physics Department, Ankara, Turkey B. Bilin, G. Karapinar58, K. Ocalan59, M. Yalvac, M. Zeyrek Bogazici University, Istanbul, Turkey E. Gulmez, M. Kaya60, O. Kaya61, S. Tekten, E.A. Yetkin62 Istanbul Technical University, Istanbul, Turkey M.N. Agaras, S. Atay, A. Cakir, K. Cankocak Institute for Scintillation Materials of National Academy of Science of Ukraine, Kharkov, Ukraine B. Grynyov Kharkov, Ukraine L. Levchuk, P. Sorokin National Scienti c Center, Kharkov Institute of Physics and Technology, University of Bristol, Bristol, United Kingdom R. Aggleton, F. Ball, L. Beck, J.J. Brooke, D. Burns, E. Clement, D. Cussans, H. Flacher, J. Goldstein, M. Grimes, G.P. Heath, H.F. Heath, J. Jacob, L. Kreczko, C. Lucas, D.M. Newbold63, S. Paramesvaran, A. Poll, T. Sakuma, S. Seif El Nasr-storey, D. Smith, V.J. Smith Rutherford Appleton Laboratory, Didcot, United Kingdom K.W. Bell, A. Belyaev64, C. Brew, R.M. Brown, L. Calligaris, D. Cieri, D.J.A. Cockerill, J.A. Coughlan, K. Harder, S. Harper, E. Olaiya, D. Petyt, C.H. Shepherd-Themistocleous, A. Thea, I.R. Tomalin, T. Williams Imperial College, London, United Kingdom M. Baber, R. Bainbridge, S. Breeze, O. Buchmuller, A. Bundock, S. Casasso, M. Citron, D. Colling, L. Corpe, P. Dauncey, G. Davies, A. De Wit, M. Della Negra, R. Di Maria, P. Dunne, A. Elwood, D. Futyan, Y. Haddad, G. Hall, G. Iles, T. James, R. Lane, C. Laner, L. Lyons, A.-M. Magnan, S. Malik, L. Mastrolorenzo, T. Matsushita, J. Nash, A. Nikitenko49, J. Pela, M. Pesaresi, D.M. Raymond, A. Richards, A. Rose, E. Scott, C. Seez, A. Shtipliyski, S. Summers, A. Tapper, K. Uchida, M. Vazquez Acosta65, T. Virdee15, D. Winterbottom, J. Wright, S.C. Zenz Brunel University, Uxbridge, United Kingdom J.E. Cole, P.R. Hobson, A. Khan, P. Kyberd, I.D. Reid, P. Symonds, L. Teodorescu, Baylor University, Waco, U.S.A. A. Borzou, K. Call, J. Dittmann, K. Hatakeyama, H. Liu, N. Pastika Catholic University of America, Washington DC, U.S.A. R. Bartek, A. Dominguez The University of Alabama, Tuscaloosa, U.S.A. A. Buccilli, S.I. Cooper, C. Henderson, P. Rumerio, C. West Boston University, Boston, U.S.A. D. Arcaro, A. Avetisyan, T. Bose, D. Gastler, D. Rankin, C. Richardson, J. Rohlf, L. Sulak, D. Zou Brown University, Providence, U.S.A. G. Benelli, D. Cutts, A. Garabedian, J. Hakala, U. Heintz, J.M. Hogan, K.H.M. Kwok, E. Laird, G. Landsberg, Z. Mao, M. Narain, S. Piperov, S. Sagir, R. Syarif, D. Yu University of California, Davis, Davis, U.S.A. R. Band, C. Brainerd, D. Burns, M. Calderon De La Barca Sanchez, M. Chertok, J. Conway, R. Conway, P.T. Cox, R. Erbacher, C. Flores, G. Funk, M. Gardner, W. Ko, R. Lander, C. Mclean, M. Mulhearn, D. Pellett, J. Pilot, S. Shalhout, M. Shi, J. Smith, M. Squires, D. Stolp, K. Tos, M. Tripathi, Z. Wang University of California, Los Angeles, U.S.A. M. Bachtis, C. Bravo, R. Cousins, A. Dasgupta, A. Florent, J. Hauser, M. Ignatenko, N. Mccoll, D. Saltzberg, C. Schnaible, V. Valuev University of California, Riverside, Riverside, U.S.A. E. Bouvier, K. Burt, R. Clare, J. Ellison, J.W. Gary, S.M.A. Ghiasi Shirazi, G. Hanson, J. Heilman, P. Jandir, E. Kennedy, F. Lacroix, O.R. Long, M. Olmedo Negrete, M.I. Paneva, A. Shrinivas, W. Si, H. Wei, S. Wimpenny, B. R. Yates University of California, San Diego, La Jolla, U.S.A. J.G. Branson, S. Cittolin, M. Derdzinski, B. Hashemi, A. Holzner, D. Klein, G. Kole, V. Krutelyov, J. Letts, I. Macneill, M. Masciovecchio, D. Olivito, S. Padhi, M. Pieri, M. Sani, V. Sharma, S. Simon, M. Tadel, A. Vartak, S. Wasserbaech66, J. Wood, F. Wurthwein, A. Yagil, G. Zevi Della Porta University of California, Santa Barbara - Department of Physics, Santa Barbara, U.S.A. N. Amin, R. Bhandari, J. Bradmiller-Feld, C. Campagnari, A. Dishaw, V. Dutta, M. Franco Sevilla, C. George, F. Golf, L. Gouskos, J. Gran, R. Heller, J. Incandela, S.D. Mullin, A. Ovcharova, H. Qu, J. Richman, D. Stuart, I. Suarez, J. Yoo California Institute of Technology, Pasadena, U.S.A. D. Anderson, J. Bendavid, A. Bornheim, J.M. Lawhorn, H.B. Newman, T. Nguyen, C. Pena, M. Spiropulu, J.R. Vlimant, S. Xie, Z. Zhang, R.Y. Zhu Carnegie Mellon University, Pittsburgh, U.S.A. M.B. Andrews, T. Ferguson, T. Mudholkar, M. Paulini, J. Russ, M. Sun, H. Vogel, I. Vorobiev, M. Weinberg University of Colorado Boulder, Boulder, U.S.A. J.P. Cumalat, W.T. Ford, F. Jensen, A. Johnson, M. Krohn, S. Leontsinis, T. Mulholland, K. Stenson, S.R. Wagner Cornell University, Ithaca, U.S.A. J. Alexander, J. Chaves, J. Chu, S. Dittmer, K. Mcdermott, N. Mirman, J.R. Patterson, A. Rinkevicius, A. Ryd, L. Skinnari, L. So , S.M. Tan, Z. Tao, J. Thom, J. Tucker, P. Wittich, M. Zientek Fermi National Accelerator Laboratory, Batavia, U.S.A. S. Abdullin, M. Albrow, G. Apollinari, A. Apresyan, A. Apyan, S. Banerjee, L.A.T. Bauerdick, A. Beretvas, J. Berryhill, P.C. Bhat, G. Bolla, K. Burkett, J.N. Butler, A. Canepa, G.B. Cerati, H.W.K. Cheung, F. Chlebana, M. Cremonesi, J. Duarte, V.D. Elvira, J. Freeman, Z. Gecse, E. Gottschalk, L. Gray, D. Green, S. Grunendahl, O. Gutsche, R.M. Harris, S. Hasegawa, J. Hirschauer, Z. Hu, B. Jayatilaka, S. Jindariani, M. Johnson, U. Joshi, B. Klima, B. Kreis, S. Lammel, D. Lincoln, R. Lipton, M. Liu, T. Liu, R. Lopes De Sa, J. Lykken, K. Maeshima, N. Magini, J.M. Marra no, S. Maruyama, D. Mason, P. McBride, P. Merkel, S. Mrenna, S. Nahn, V. O'Dell, K. Pedro, O. Prokofyev, G. Rakness, L. Ristori, B. Schneider, E. Sexton-Kennedy, A. Soha, W.J. Spalding, L. Spiegel, S. Stoynev, J. Strait, N. Strobbe, L. Taylor, S. Tkaczyk, N.V. Tran, L. Uplegger, E.W. Vaandering, C. Vernieri, M. Verzocchi, R. Vidal, M. Wang, H.A. Weber, A. Whitbeck University of Florida, Gainesville, U.S.A. D. Acosta, P. Avery, P. Bortignon, A. Brinkerho , A. Carnes, M. Carver, D. Curry, S. Das, R.D. Field, I.K. Furic, J. Konigsberg, A. Korytov, K. Kotov, P. Ma, K. Matchev, H. Mei, G. Mitselmakher, D. Rank, D. Sperka, N. Terentyev, L. Thomas, J. Wang, S. Wang, J. Yelton Florida International University, Miami, U.S.A. Y.R. Joshi, S. Linn, P. Markowitz, G. Martinez, J.L. Rodriguez Florida State University, Tallahassee, U.S.A. A. Ackert, T. Adams, A. Askew, S. Hagopian, V. Hagopian, K.F. Johnson, T. Kolberg, T. Perry, H. Prosper, A. Santra, R. Yohay Florida Institute of Technology, Melbourne, U.S.A. M.M. Baarmand, V. Bhopatkar, S. Colafranceschi, M. Hohlmann, D. Noonan, T. Roy, F. Yumiceva University of Illinois at Chicago (UIC), Chicago, U.S.A. M.R. Adams, L. Apanasevich, D. Berry, R.R. Betts, R. Cavanaugh, X. Chen, O. Evdokimov, C.E. Gerber, D.A. Hangal, D.J. Hofman, K. Jung, J. Kamin, I.D. Sandoval Gonzalez, M.B. Tonjes, H. Trauger, N. Varelas, H. Wang, Z. Wu, J. Zhang The University of Iowa, Iowa City, U.S.A. B. Bilki67, W. Clarida, K. Dilsiz68, S. Durgut, R.P. Gandrajula, M. Haytmyradov, V. Khristenko, J.-P. Merlo, H. Mermerkaya69, A. Mestvirishvili, A. Moeller, J. Nachtman, H. Ogul70, Y. Onel, F. Ozok71, A. Penzo, C. Snyder, E. Tiras, J. Wetzel, K. Yi Johns Hopkins University, Baltimore, U.S.A. B. Blumenfeld, A. Cocoros, N. Eminizer, D. Fehling, L. Feng, A.V. Gritsan, P. Maksimovic, J. Roskes, U. Sarica, M. Swartz, M. Xiao, C. You The University of Kansas, Lawrence, U.S.A. A. Al-bataineh, P. Baringer, A. Bean, S. Boren, J. Bowen, J. Castle, S. Khalil, A. Kropivnitskaya, D. Majumder, W. Mcbrayer, M. Murray, C. Royon, S. Sanders, E. Schmitz, R. Stringer, J.D. Tapia Takaki, Q. Wang Kansas State University, Manhattan, U.S.A. A. Ivanov, K. Kaadze, Y. Maravin, A. Mohammadi, L.K. Saini, N. Skhirtladze, S. Toda Lawrence Livermore National Laboratory, Livermore, U.S.A. F. Rebassoo, D. Wright University of Maryland, College Park, U.S.A. C. Anelli, A. Baden, O. Baron, A. Belloni, B. Calvert, S.C. Eno, C. Ferraioli, N.J. Hadley, S. Jabeen, G.Y. Jeng, R.G. Kellogg, J. Kunkle, A.C. Mignerey, F. Ricci-Tam, Y.H. Shin, A. Skuja, S.C. Tonwar Massachusetts Institute of Technology, Cambridge, U.S.A. D. Abercrombie, B. Allen, V. Azzolini, R. Barbieri, A. Baty, R. Bi, S. Brandt, W. Busza, I.A. Cali, M. D'Alfonso, Z. Demiragli, G. Gomez Ceballos, M. Goncharov, D. Hsu, Y. Iiyama, G.M. Innocenti, M. Klute, D. Kovalskyi, Y.S. Lai, Y.-J. Lee, A. Levin, P.D. Luckey, B. Maier, A.C. Marini, C. Mcginn, C. Mironov, S. Narayanan, X. Niu, C. Paus, C. Roland, G. Roland, J. Salfeld-Nebgen, G.S.F. Stephans, K. Tatar, D. Velicanu, J. Wang, T.W. Wang, B. Wyslouch University of Minnesota, Minneapolis, U.S.A. A.C. Benvenuti, R.M. Chatterjee, A. Evans, P. Hansen, S. Kalafut, Y. Kubota, Z. Lesko, J. Mans, S. Nourbakhsh, N. Ruckstuhl, R. Rusack, J. Turkewitz University of Mississippi, Oxford, U.S.A. J.G. Acosta, S. Oliveros University of Nebraska-Lincoln, Lincoln, U.S.A. E. Avdeeva, K. Bloom, D.R. Claes, C. Fangmeier, R. Gonzalez Suarez, R. Kamalieddin, I. Kravchenko, J. Monroy, J.E. Siado, G.R. Snow, B. Stieger State University of New York at Bu alo, Bu alo, U.S.A. M. Alyari, J. Dolen, A. Godshalk, C. Harrington, I. Iashvili, D. Nguyen, A. Parker, S. Rappoccio, B. Roozbahani Northeastern University, Boston, U.S.A. G. Alverson, E. Barberis, A. Hortiangtham, A. Massironi, D.M. Morse, D. Nash, T. Orimoto, R. Teixeira De Lima, D. Trocino, R.-J. Wang, D. Wood Northwestern University, Evanston, U.S.A. S. Bhattacharya, O. Charaf, K.A. Hahn, N. Mucia, N. Odell, B. Pollack, M.H. Schmitt, K. Sung, M. Trovato, M. Velasco University of Notre Dame, Notre Dame, U.S.A. N. Dev, M. Hildreth, K. Hurtado Anampa, C. Jessop, D.J. Karmgard, N. Kellams, K. Lannon, N. Loukas, N. Marinelli, F. Meng, C. Mueller, Y. Musienko36, M. Planer, A. Reinsvold, R. Ruchti, G. Smith, S. Taroni, M. Wayne, M. Wolf, A. Woodard The Ohio State University, Columbus, U.S.A. J. Alimena, L. Antonelli, B. Bylsma, L.S. Durkin, S. Flowers, B. Francis, A. Hart, C. Hill, W. Ji, B. Liu, W. Luo, D. Puigh, B.L. Winer, H.W. Wulsin Princeton University, Princeton, U.S.A. A. Benaglia, S. Cooperstein, O. Driga, P. Elmer, J. Hardenbrook, P. Hebda, D. Lange, J. Luo, D. Marlow, K. Mei, I. Ojalvo, J. Olsen, C. Palmer, P. Piroue, D. Stickland, A. Svyatkovskiy, C. Tully University of Puerto Rico, Mayaguez, U.S.A. S. Malik, S. Norberg Purdue University, West Lafayette, U.S.A. A. Barker, V.E. Barnes, S. Folgueras, L. Gutay, M.K. Jha, M. Jones, A.W. Jung, A. Khatiwada, D.H. Miller, N. Neumeister, J.F. Schulte, J. Sun, F. Wang, W. Xie Purdue University Northwest, Hammond, U.S.A. T. Cheng, N. Parashar, J. Stupak Rice University, Houston, U.S.A. A. Adair, B. Akgun, Z. Chen, K.M. Ecklund, F.J.M. Geurts, M. Guilbaud, W. Li, B. Michlin, M. Northup, B.P. Padley, J. Roberts, J. Rorie, Z. Tu, J. Zabel University of Rochester, Rochester, U.S.A. A. Bodek, P. de Barbaro, R. Demina, Y.t. Duh, T. Ferbel, M. Galanti, A. Garcia-Bellido, J. Han, O. Hindrichs, A. Khukhunaishvili, K.H. Lo, P. Tan, M. Verzetti The Rockefeller University, New York, U.S.A. R. Ciesielski, K. Goulianos, C. Mesropian Rutgers, The State University of New Jersey, Piscataway, U.S.A. A. Agapitos, J.P. Chou, Y. Gershtein, T.A. Gomez Espinosa, E. Halkiadakis, M. Heindl, E. Hughes, S. Kaplan, R. Kunnawalkam Elayavalli, S. Kyriacou, A. Lath, R. Montalvo, K. Nash, M. Osherson, H. Saka, S. Salur, S. Schnetzer, D. She eld, S. Somalwar, R. Stone, S. Thomas, P. Thomassen, M. Walker University of Tennessee, Knoxville, U.S.A. M. Foerster, J. Heideman, G. Riley, K. Rose, S. Spanier, K. Thapa Texas A&M University, College Station, U.S.A. O. Bouhali72, A. Castaneda Hernandez72, A. Celik, M. Dalchenko, M. De Mattia, A. Delgado, S. Dildick, R. Eusebi, J. Gilmore, T. Huang, T. Kamon73, R. Mueller, Y. Pakhotin, R. Patel, A. Perlo , L. Pernie, D. Rathjens, A. Safonov, A. Tatarinov, K.A. Ulmer Texas Tech University, Lubbock, U.S.A. N. Akchurin, J. Damgov, F. De Guio, P.R. Dudero, J. Faulkner, E. Gurpinar, S. Kunori, K. Lamichhane, S.W. Lee, T. Libeiro, T. Peltola, S. Undleeb, I. Volobouev, Z. Wang Vanderbilt University, Nashville, U.S.A. S. Greene, A. Gurrola, R. Janjam, W. Johns, C. Maguire, A. Melo, H. Ni, P. Sheldon, S. Tuo, J. Velkovska, Q. Xu University of Virginia, Charlottesville, U.S.A. sith, X. Sun, Y. Wang, E. Wolfe, F. Xia Wayne State University, Detroit, U.S.A. C. Clarke, R. Harr, P.E. Karchin, J. Sturdy, S. Zaleski M.W. Arenton, P. Barria, B. Cox, R. Hirosky, A. Ledovskoy, H. Li, C. Neu, T. SinthupraUniversity of Wisconsin - Madison, Madison, WI, U.S.A. J. Buchanan, C. Caillol, S. Dasu, L. Dodd, S. Duric, B. Gomber, M. Grothe, M. Herndon, A. Herve, U. Hussain, P. Klabbers, A. Lanaro, A. Levine, K. Long, R. Loveless, G.A. Pierro, G. Polese, T. Ruggles, A. Savin, N. Smith, W.H. Smith, D. Taylor, N. Woods y: Deceased China 1: Also at Vienna University of Technology, Vienna, Austria 2: Also at State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, 3: Also at Universidade Estadual de Campinas, Campinas, Brazil 4: Also at Universidade Federal de Pelotas, Pelotas, Brazil 5: Also at Universite Libre de Bruxelles, Bruxelles, Belgium 6: Also at Joint Institute for Nuclear Research, Dubna, Russia 7: Also at Helwan University, Cairo, Egypt 8: Now at Zewail City of Science and Technology, Zewail, Egypt 9: Now at Fayoum University, El-Fayoum, Egypt 11: Now at Ain Shams University, Cairo, Egypt 12: Also at Universite de Haute Alsace, Mulhouse, France Moscow, Russia 13: Also at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 14: Also at Ilia State University, Tbilisi, Georgia 15: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland 16: Also at RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany 17: Also at University of Hamburg, Hamburg, Germany 18: Also at Brandenburg University of Technology, Cottbus, Germany 19: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary 20: Also at MTA-ELTE Lendulet CMS Particle and Nuclear Physics Group, Eotvos Lorand University, Budapest, Hungary 21: Also at Institute of Physics, University of Debrecen, Debrecen, Hungary 22: Also at Indian Institute of Technology Bhubaneswar, Bhubaneswar, India 23: Also at Institute of Physics, Bhubaneswar, India 24: Also at University of Visva-Bharati, Santiniketan, India 25: Also at University of Ruhuna, Matara, Sri Lanka 26: Also at Isfahan University of Technology, Isfahan, Iran 27: Also at Yazd University, Yazd, Iran 28: Also at Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran 29: Also at Universita degli Studi di Siena, Siena, Italy 30: Also at INFN Sezione di Milano-Bicocca; Universita di Milano-Bicocca, Milano, Italy 31: Also at Purdue University, West Lafayette, U.S.A. 32: Also at International Islamic University of Malaysia, Kuala Lumpur, Malaysia 33: Also at Malaysian Nuclear Agency, MOSTI, Kajang, Malaysia 34: Also at Consejo Nacional de Ciencia y Tecnolog a, Mexico city, Mexico 35: Also at Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland 36: Also at Institute for Nuclear Research, Moscow, Russia 37: Now at National Research Nuclear University 'Moscow 38: Also at St. Petersburg State Polytechnical University, St. Petersburg, Russia 39: Also at University of Florida, Gainesville, U.S.A. 40: Also at P.N. Lebedev Physical Institute, Moscow, Russia 41: Also at California Institute of Technology, Pasadena, U.S.A. 42: Also at Budker Institute of Nuclear Physics, Novosibirsk, Russia 43: Also at Faculty of Physics, University of Belgrade, Belgrade, Serbia 44: Also at INFN Sezione di Roma; Sapienza Universita di Roma, Rome, Italy Belgrade, Serbia 46: Also at Scuola Normale e Sezione dell'INFN, Pisa, Italy 47: Also at National and Kapodistrian University of Athens, Athens, Greece 48: Also at Riga Technical University, Riga, Latvia 49: Also at Institute for Theoretical and Experimental Physics, Moscow, Russia 50: Also at Albert Einstein Center for Fundamental Physics, Bern, Switzerland 51: Also at Istanbul University, Faculty of Science, Istanbul, Turkey 52: Also at Istanbul Aydin University, Istanbul, Turkey 45: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, 54: Also at Cag University, Mersin, Turkey 55: Also at Piri Reis University, Istanbul, Turkey 56: Also at Gaziosmanpasa University, Tokat, Turkey 57: Also at Adiyaman University, Adiyaman, Turkey 58: Also at Izmir Institute of Technology, Izmir, Turkey 59: Also at Necmettin Erbakan University, Konya, Turkey 60: Also at Marmara University, Istanbul, Turkey 61: Also at Kafkas University, Kars, Turkey 62: Also at Istanbul Bilgi University, Istanbul, Turkey 63: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom 64: Also at School of Physics and Astronomy, University of Southampton, Southampton, United 65: Also at Instituto de Astrof sica de Canarias, La Laguna, Spain 66: Also at Utah Valley University, Orem, U.S.A. 67: Also at Beykent University, Istanbul, Turkey 68: Also at Bingol University, Bingol, Turkey 69: Also at Erzincan University, Erzincan, Turkey 70: Also at Sinop University, Sinop, Turkey 71: Also at Mimar Sinan University, Istanbul, Istanbul, Turkey 72: Also at Texas A&M University at Qatar, Doha, Qatar 73: Also at Kyungpook National University, Daegu, Korea [33] M. Cacciari , G.P. Salam and G. Soyez, The anti-kt jet clustering algorithm , JHEP 04 ( 2008 ) [34] M. Cacciari , G.P. Salam and G. Soyez, FastJet user manual , Eur. Phys. J. C 72 ( 2012 ) 1896 [35] M. Cacciari , G.P. Salam and G. Soyez, The catchment area of jets , JHEP 04 ( 2008 ) 005 [46] T. Sj ostrand et al ., An introduction to PYTHIA 8.2, Comput . Phys. Commun . 191 ( 2015 ) [47] M. Czakon and A. Mitov , Top++ : a program for the calculation of the top-pair cross-section at hadron colliders , Comput. Phys. Commun . 185 ( 2014 ) 2930 [arXiv: 1112 .5675] [INSPIRE]. [48] M. Czakon , P. Fiedler and A. Mitov , Total top-quark pair-production cross section at hadron colliders through O( S4 ), Phys. Rev. Lett . 110 ( 2013 ) 252004 [arXiv: 1303 .6254] [INSPIRE]. [49] M. Czakon and A. Mitov , NNLO corrections to top pair production at hadron colliders: the quark-gluon reaction , JHEP 01 ( 2013 ) 080 [arXiv: 1210 .6832] [INSPIRE]. [52] M. Cacciari , M. Czakon , M. Mangano , A. Mitov and P. 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The CMS collaboration, A. M. Sirunyan, A. Tumasyan, W. Adam, F. Ambrogi, E. Asilar, T. Bergauer, J. Brandstetter, E. Brondolin, M. Dragicevic, J. Erö, M. Flechl, M. Friedl, R. Frühwirth, V. M. Ghete, J. Grossmann, J. Hrubec, M. Jeitler, A. König, N. Krammer, I. Krätschmer, D. Liko, T. Madlener, I. Mikulec, E. Pree, D. Rabady, N. Rad, H. Rohringer, J. Schieck, R. Schöfbeck, M. Spanring, D. Spitzbart, J. Strauss, W. Waltenberger, J. Wittmann, C.-E. Wulz, M. Zarucki, V. Chekhovsky, V. Mossolov, J. Suarez Gonzalez, E. A. De Wolf, D. Di Croce, X. Janssen, J. Lauwers, M. Van De Klundert, H. Van Haevermaet, P. Van Mechelen, N. Van Remortel, A. Van Spilbeeck, S. Abu Zeid, F. Blekman, J. D’Hondt, I. De Bruyn, J. De Clercq, K. Deroover, G. Flouris, D. Lontkovskyi, S. Lowette, S. Moortgat, L. Moreels, A. Olbrechts, Q. Python, K. Skovpen, S. Tavernier, W. Van Doninck, P. Van Mulders, I. Van Parijs, H. Brun, B. Clerbaux, G. De Lentdecker, H. Delannoy, G. Fasanella, L. Favart, R. Goldouzian, A. 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