Constraints on the double-parton scattering cross section from same-sign W boson pair production in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV

Journal of High Energy Physics, Feb 2018

Abstract A first search for same-sign WW production via double-parton scattering is performed based on proton-proton collision data at a center-of-mass energy of 8 TeV using dimuon and electron-muon final states. The search is based on the analysis of data corresponding to an integrated luminosity of 19.7 fb−1. No significant excess of events is observed above the expected single-parton scattering yields. A 95% confidence level upper limit of 0.32 pb is set on the inclusive cross section for same-sign WW production via the double-parton scattering process. This upper limit is used to place a 95% confidence level lower limit of 12.2 mb on the effective double-parton cross section parameter, closely related to the transverse distribution of partons in the proton. This limit on the effective cross section is consistent with previous measurements as well as with Monte Carlo event generator predictions. Open image in new window

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Constraints on the double-parton scattering cross section from same-sign W boson pair production in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV

HJE 8 TeV A rst search for same-sign WW production via double-parton scattering is performed based on proton-proton collision data at a center-of-mass energy of 8 TeV using dimuon and electron-muon nal states. The search is based on the analysis of data corresponding to an integrated luminosity of 19.7 fb 1 observed above the expected single-parton scattering yields. A 95% con dence level upper limit of 0.32 pb is set on the inclusive cross section for same-sign WW production via the double-parton scattering process. This upper limit is used to place a 95% con dence level lower limit of 12.2 mb on the e ective double-parton cross section parameter, closely related to the transverse distribution of partons in the proton. This limit on the e ective cross section is consistent with previous measurements as well as with Monte Carlo event generator predictions. Hadron-Hadron scattering (experiments) - W 1 Introduction The CMS detector Data and simulated samples Experimental methods 4.1 4.2 4.3 4.4 Event selection Background evaluation Multivariate analysis Systematic uncertainties Results Summary The CMS collaboration 2 3 4 5 6 as: 1 Introduction In proton-proton (pp) collisions at the CERN LHC, the large density of partons inside the proton at small x, where x is the momentum fraction of the proton carried by a parton, results in a signi cant probability for the simultaneous occurrence of two or more partonparton interactions within a single pp collision [1]. These short-distance inelastic processes, called multiple-parton interactions (MPI), usually produce particles with relatively small transverse momenta (pT) that predominantly constitute the so-called \underlying event". With increased parton densities at high center-of-mass energies, there is a nonnegligible probability for the production of high-pT or high-mass particles even from the secondhardest parton-parton scattering, a process known as double-parton scattering (DPS). The production cross section for a DPS process, ADBPS, involving two independent processes \A" and \B" with respective individual production cross sections A and B, can be factorized DPS = AB m 2 A B e ; (1.1) where m is a combinatorial factor (m = 1 for identical and m = 2 for di erent processes) and e is an e ective cross section, mainly determined by the transverse pro le of partons inside the colliding hadrons and their overlap in a collision. Such a simple geometric interpretation of e assumes negligible parton-parton correlations (in momentum, space, { 1 { colour, avour,. . . ) [2], which is an assumption particularly well justi ed at low x values where the parton densities are very large [ 3 ]. The measurement of the DPS cross section is important as it provides valuable information on the distribution of partons inside the proton in the transverse direction and on the correlations between them [2{7]. DPS also constitutes a background to searches for new physics, in rare nal states with multiple heavy particles, as well as to measurements of standard model processes, such as the associated production of a Higgs and a W or Z boson [8, 9]. Studies of DPS have been proposed using a variety of processes, including double Drell-Yan (DY) production [10], the production of same-sign W bosons [ 3 ], W or Z boson production in association with jets [11, 12], and four-jet production [13, 14]. A number of experiments have previously measured DPS cross sections, using various nal states at different collision energies [15{22]. The magnitude of the cross section for a given DPS process depends on the value of e and on the cross sections for the individual single-parton scattering (SPS) processes involved, according to eq. (1.1). In the simplest approaches, e is expected to be independent of collision energy and of the processes involved [ 2, 4, 5, 23, 24 ]. Values of e 20 mb are predicted by Monte Carlo (MC) event generators, tuned to reproduce low-pT MPI measurements [25], that assume the independence of e with respect to the scale of MPI, as de ned by the momentum transfer in a given parton-parton interaction. However, the existing measurements of e have large systematic uncertainties [21] and hence it is not possible to draw a rm conclusion about the dependence of e on either the process or the collision energy. It is therefore important to perform further DPS cross section measurements using a variety of processes at di erent center-of-mass energies. This paper presents the rst measurement of the DPS process for same-sign WW events in the dilepton nal state using pp collision data collected by the CMS experiment at a center-of-mass energy of p s = 8 TeV. In the case of WW production via DPS, the scale of the second hard interaction is comparable to the mass of the W boson, which is the largest scale explored experimentally so far in DPS cross section measurements. Only same-sign WW events are considered in order to suppress the contribution from the DY and SPS processes. Leptonic decays of the two W bosons into either a pair of muons or an electron-muon pair are considered, as only these W decay channels result in a properlyreconstructed nal state that is not completely overwhelmed by background. Figure 1 illustrates the production of a same-sign W boson pair via the DPS process (left) and via a selection of leading order SPS processes (right). A set of DPS-sensitive observables is used in a multivariate analysis based on boosted decision trees (BDT) to enhance the signal sensitivity. The shape of the BDT discriminant is then used to set a limit on the cross section for same-sign WW production via DPS, and subsequently on e . This paper is organized as follows: in section 2, a brief description of the CMS detector is presented, followed by a description of the data and the simulated samples in section 3. The event selection criteria, a description of the BDT, and the systematic uncertainties a ecting the measurement are described in section 4. The results are presented in section 5, and section 6 summarizes the studies presented here. { 2 { the DPS process (left) and via SPS processes (right). 2 The CMS detector 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 ( ) coverage provided by the barrel and endcap detectors. Muons are detected and measured using the gasionization chambers embedded in the steel ux-return yoke outside the solenoid. The rst level (L1) of the CMS trigger and data acquisition systems is designed to select potentially interesting events with high e ciency [26]. The L1 trigger uses information collected by the calorimeters and muon detectors to select the most interesting events in less than 4 s. The detector data are pipelined to ensure negligible deadtime up to a L1 rate of 100 kHz. After L1 triggering, data are transferred from the readout electronics of all subdetectors to the high-level trigger processor farm, where a further reduction of event rate to few hundred Hz is achieved for the purpose of data storage. 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. [27]. 3 Data and simulated samples The analyzed data correspond to an integrated luminosity of 19.7 fb 1 recorded by the CMS detector during 2012 in pp collisions at p s = 8 TeV. The decays of W bosons into a muon or an electron (plus the corresponding neutrinos) are considered, but only the same-sign dimuon and electron-muon nal states are actually used in the current analysis. { 3 { These nal states also include the contributions from the leptonic decay of leptons coming from the W bosons. The dielectron nal state is not considered because of the relatively high probability of charge misidenti cation for electrons, which results in this pT > 17 (8) GeV. The dilepton trigger, used for the online selection of the electron-muon nal state, required one electron (muon) with pT > 17 GeV and one muon (electron) with pT > 8 GeV. The e ciencies of the dimuon and electron-muon triggers with respect to the o ine selection are 90% and 94%, respectively. The simulated signal events for DPS W boson pair production are generated using the pythia8 event generator (version 8.165) with the 4C tune [ 28, 29 ] to describe the underlying event processes. The contribution of W boson pair production via SPS is removed from the signal sample. In pythia8, MPI are predominantly driven by the amount of overlap of the transverse matter distributions of the protons in impact parameter space [1], and are interleaved with parton showering. For the tune used, the DPS cross section for (leading order) inclusive same-sign WW production (including all W boson decays) is 0.30 pb, and the corresponding e ective DPS cross section amounts to e = 28 mb. Several SPS processes share the same like-sign dilepton nal state as our DPS signal. All backgrounds have been studied in detail with MC simulated events as well as with data-driven estimates. The production of same-sign W boson pairs, electroweak and strong production of W boson pairs in association with jets (WW+jets), fully leptonic decays of top quark-antiquark pairs (tt), DY, W , and W/Z events are simulated using the madgraph5 (version 5.1.3.30) event generator [30]. The single top quark production processes in t- and s-channels are modeled using the powheg (version 1.0) event generator [31]. The WZ and ZZ production processes are generated with the pythia6 event generator. All simulated samples use the CTEQ6L1 [32] parton density functions (PDF) set, with parton showering and hadronization performed with pythia6 (version 6.4.25) using the Z2* tune for the modeling of underlying event activity [33, 34]. The generated MC simulations are scaled to their respective theoretical cross sections (at next-to-leading order or next-to-next-to-leading order (NNLO) accuracy, the highest order prediction available in each case) [35{38], and multiplied by the integrated luminosity of the data sample. In addition, other background processes that result from jets being misidenti ed as leptons | such as single W boson production in association with jets (W+jets), tt in lepton+jets, and quantum chromodynamics (QCD) multijet production | are directly estimated from the data, as discussed in section 4.2. The data sample analysed in this work was collected with high instantaneous luminosities which lead to additional pp interactions (pileup) produced within the same bunch crossing. The simulated samples include the e ect of pileup, with a multiplicity of pp interactions matching that from the data. The average number of measured pileup interactions per beam crossing in the 8 TeV data set is about 21. The detector response is simulated using the Geant4 package [39] and the resulting simulated events are reconstructed with the same algorithms used for the data. { 4 { HJEP02(18)3 4.1 Event selection A particle- ow (PF) algorithm [40] is used for event reconstruction. The information from all subdetectors of the CMS detector is combined to reconstruct individual candidates for muons, electrons, photons, as well as charged and neutral hadrons produced in an event. The o ine event selection criteria require the presence of at least two well reconstructed and isolated leptons with the same sign (either two muons or an electron and a muon). The leading (subleading) lepton is required to have pT > 20 (10) GeV. The muon candidates are identi ed using charged-particle tracks reconstructed in the muon system that are compatare required to lie within a geometrical acceptance de ned by j j < 2:4. The electrons are identi ed using a multivariate approach based on shower shape variables, the energy sharing between the ECAL and HCAL, and the matching information provided by the tracker [42]. The electrons with j j < 2:5, except those falling in the transition region between the barrel and endcap of the ECAL (1:44 < j j < 1:57), are considered for this analysis. A lepton isolation variable (RIso) [38], measured relative to the lepton pT, is used to discriminate between the prompt leptons originating from a W/Z boson decay and those from quark and hadron decays. This variable is de ned based on the sum of the transverse energies of all reconstructed particles, charged or neutral, within a cone of R = )2 + ( ) 2 < 0:3 around the lepton direction, after subtracting the contributions from pileup and underlying event activity [43, 44] on an event-by-event basis. The value of RIso is required to be smaller than 0.12 (0.15) for muon (electron) candidates. The two lepton candidates also need to be associated with the same primary vertex, through the requirement that the longitudinal (transverse) impact parameter of each lepton is smaller than 0.1 (0.02) cm. The missing transverse momentum vector (p~Tmiss) is de ned as the projection of the negative vector sum of the momenta of all reconstructed PF objects in an event onto the plane perpendicular to the beam axis. Its magnitude is referred to as pTmiss, and is corrected for anisotropic detector responses, inactive calorimeter cells, and detector misalignment. To suppress Z ! `+` contributions, pTmiss is required to be greater than 20 GeV. The jets are reconstructed using the anti-kT clustering algorithm with the FastJet (version 2.1) package [43, 45] with a distance parameter of 0.5. To eliminate the jets originating from or being seeded by noisy channels in the calorimeters, a jet quality requirement, primarily based on the energy ratio between the charged and neutral hadrons, is applied [46]. Jet energy scale corrections [47, 48] are used to account for the nonlinear energy response of the calorimeters and other instrumental e ects. The e ect of jet energy scale corrections is also propagated to pmiss. T To reduce the contributions from ZZ, WZ, and W production processes, where the nal state can have more than two leptons, events having three or more well reconstructed and isolated leptons with pT > 10 GeV are rejected. Furthermore, to reduce events from low-mass resonances, the two selected leptons are required to have an invariant mass (m``) greater than 20 GeV. Additionally, for the dimuon nal state, m`` is also required to be { 5 { Dimuon channel Electron-muon channel Pair of same-sign leptons Leading lepton pT > 20 GeV Subleading lepton pT > 10 GeV No third isolated and identi ed lepton with pT > 10 GeV jpT 1 j + jpT 2 j > 45 GeV away from the Z boson mass peak (m`` 2= [75; 105] GeV). A minimum threshold of 45 GeV on the scalar sum of the pT of the two muons is also applied to reduce the contributions from QCD multijet events. The main background in the electron-muon nal state comes from events in which a pair of top quarks are produced and subsequently decay via their semileptonic mode t ! bW; W ! ` l, with ` = e; ; . The contribution from this background for the dimuon channel is found to be negligible. A b jet veto is applied in the electron-muon to reduce the contribution from this source. The combined secondary vertex b tagging algorithm [49] is used to identify jets that are likely to originate from the hadronization of b quarks. Events containing one or more b-tagged jets with pT > 30 GeV and j j < 2.1 are vetoed. The b tagging e ciency is 60{80%, while the mistag rate for light- avored jets is about 2{3% after the same-sign WW selection criteria, given in table 1, have been applied. 4.2 Background evaluation The majority of background events originate from processes in which one or both of the leptons, coming from leptonic decays of heavy quarks or in- ight decays of light mesons, pass the event selection criteria. In the case of the electrons, overlaps of 0 ! charged hadrons may also contaminate the sample. These lepton candidates are referred decays with to as misidenti ed leptons. Events containing one prompt and one misidenti ed lepton, referred to as prompt-misid. events, mainly come from W+jets production and from semileptonic decays of top quarks. The QCD multijet events fall into the category of misid.-misid. events, as both leptons are misidenti ed. A method based on control samples in the data is used to estimate the contributions of misid.-misid. and prompt-misid. backgrounds [38]. The method relies on a lepton misidenti cation rate estimated from the e ciency for a lepton-like object, passing loose lepton selection criteria of RIso < 1.0 and pT > 10 GeV, to also pass the complete set of lepton selection criteria described in section 4.1. The lepton misidenti cation rates are measured using a control sample in the data that is enriched with misidenti ed leptons, and are parametrized as a function of the lepton pT and . { 6 { Region 1 of least one b-tagged jet, is used in the electron-muon channel to reduce semileptonically decaying tt events. 1 and Region 2) in the data that are enriched with misidenti ed leptons. Region 1 is used for the dimuon nal state while Region 2, which additionally requires the presence of at least one b-tagged jet, is used in the electron-muon nal state, since it includes a major contribution from semileptonically decaying tt events. Both regions require the presence of only one loosely identi ed (\loose") lepton in order to suppress Z ! `+` contributions. Also, to further reduce the contributions from W/Z boson decays in the regions enriched with misidenti ed leptons, the transverse mass of the lepton and pmiss, mT(`; pTmiss), is T required to be less than 20 GeV and pTmiss to be less than 20 GeV. The backgrounds with one prompt and one misidenti ed lepton are estimated using the tight-fail control sample that is constructed by requiring that one of the leptons passes the loose selection criteria only, whilst the other passes the full lepton selection criteria. Similarly, another control sample with fail-fail lepton pairs is de ned in which both of the leptons pass only the loose selection criteria. Finally, the selection criteria, given in table 1, are applied to these samples and the resulting numbers of events are scaled using the lepton misidenti cation rate to estimate the contributions from prompt-misid. and misid.-misid. backgrounds in the signal region. For the W background contribution, a correction factor for the simulated events is obtained from a high-purity data sample enriched with W events, identi ed by the presence of three reconstructed leptons, as described in ref. [38]. A factor of 1.5 0.3 with respect to the predicted leading-order cross section is determined. Charged dilepton nalstates from DY and tt decays contribute to the background when the charge of one of the leptons is misidenti ed. These processes also contribute to the background if a hadronically decaying lepton is misidenti ed as an electron or a muon and combines with a prompt lepton to form a same-sign electron-muon pair. The charge misidenti cation probability for electrons in the data is found to be compatible with that from the simulation; these backgrounds can therefore be estimated using the simulated samples. However, due to the limited statistical precision of the MC simulated samples, the shapes of the kinematic observables are obtained with opposite-sign electron-muon pairs in order to increase the sample sizes; all the other selection criteria given in table 1 are applied unchanged. The resulting distributions are then normalized to the corresponding same-sign yields. The { 7 { normalizations of these two backgrounds are cross-checked by constructing control regions enriched with these backgrounds. To construct a DY-enriched control region, opposite-sign pairs of electrons and muons are required to have a dilepton invariant mass that satis es 40 < m`` < 80 GeV, and a dilepton transverse mass that satis es mT < 60 GeV. For the dileptonic tt decays, a control region enriched with top quark events is constructed by inverting the b jet veto criteria in the opposite-sign WW selection requirements. The background contributions arising from lepton misidenti cation constitute the dominant fraction (72%) of the total event yield after the same-sign WW selection criteria have been applied for both nal states. 4.3 Multivariate analysis The BDT-based framework [50] is used to discriminate between the signal and the background events, combining information from a set of kinematic variables that are sensitive to the di erences between DPS WW production and the background processes. The BDT is trained using the DPS signal and the major background processes, including those originating from misidenti cation of leptons and diboson processes. The variables used as input for the BDT are based on energy-momentum conservation and are sensitive to the energy imbalance in the reference system of the W boson pair. For the dimuon channel, the following set of variables has been used for the training and testing of the BDT: pT of the two muons: pT1 , pT2 ; pTmiss; (p~T1 ; p~Tmiss) and (p~T2 ; p~Tmiss); azimuthal angular separation between the leading/subleading muon and p~miss: T azimuthal angular separation between the two muons: transverse mass of the leading/subleading muon and p~miss: mT( 1;2; pTmiss) = 2pT1;2 pTmiss(1 cos ( (p~T1;2 ; p~miss))); T T dimuon transverse mass: mT( 1; 2) = p2pT1 pT2 (1 For the electron-muon channel, the BDT variables include: pT of the two leptons: pT1 , pT2 ; vector sum of the pT of the two leptons: p~T12 = p~T1 + p~T2 ; cos ( (p~T1 ; p~T2 ))). pTmiss; (p~T2 ; p~Tmiss); pseudorapidity separation between the two leptons: (`1; `2); azimuthal angular separation between the subleading lepton and p~miss: T { 8 { HJEP02(18)3 azimuthal angular separation between the two leptons: azimuthal angular separation between the resultant direction of the dilepton system and p~miss: T (p~T12 ; p~Tmiss). These sets of variables have been selected based on their power to discriminate between the signal and background processes. Figures 2 and 3 compare the data to the signal and background predictions for the most sensitive of the input variables for the dimuon and electron-muon nal states, respectively, after applying the same-sign WW selection criteria. Overall, the data and simulation are found to be consistent within the uncertainties. The BDT discriminant after the full event selection has been applied is used to extract the limits on the DPS cross section and e using statistical analysis techniques. 4.4 Systematic uncertainties The systematic uncertainties in this analysis arise from the background estimation techniques, experimental measurements, and theoretical predictions. The dominant source of systematic uncertainty is associated with the method adopted for the estimation of misid.-misid. and prompt-misid. backgrounds, and with the de nition of the control sample used to obtain the lepton misidenti cation rate. To estimate the e ects of the jet pT spectra and jet avor on the lepton misidenti cation rate, these backgrounds are estimated by changing the de nition of the misidenti ed leptonenriched region. The observed di erences in the estimated event yields and in the shapes of the kinematic observables, for the di erent de nitions of the control samples, are taken as the systematic uncertainty. For the dimuon channel, the lepton misidenti cation rate is recalculated by requiring the presence of a jet with pT > 25 GeV in addition to the nominal selection criteria for Region 1. To estimate the e ect of jet avor, the lepton misidenti cation rate is measured using the QCD multijet simulated sample and applied to the W+jets simulated sample. For the electron-muon channel, these backgrounds are recalculated after removing the requirement of the presence of a b-tagged jet in the de nition of the misidenti ed leptonenriched region. The e ect of statistical uctuations on the lepton misidenti cation rate is also considered when calculating the nal background yields. The systematic uncertainty arising from this background estimation method results in a 40% variation in the misid.misid. event yields for both nal states, and in the prompt-misid. event yield for the dimuon channel. For the electron-muon channel this systematic uncertainty results in a 20% to 40% variation of the yield of prompt-misid. events, depending on the shape of the kinematic observable being considered. The uncertainty on the yields of the various simulated samples from pileup mismodeling is evaluated to be 4{5%. This is determined by varying the inelastic pp cross section, which is used to estimate the pileup contribution in data, from its central value within its 5% uncertainty. The measurements are also a ected by the uncertainty on the integrated luminosity calibration, and an uncertainty of 2.6% [51] is assigned to the simulated samples to account for this. { 9 { prompt-misid. Data 1d07 a r 1.306 1t/s005 1en04 v 1E03 102 10 1 10−1 10−2 CMS C 2 −3 0 −3 −2 −2 −1 −1 0 0 HJEP02(18)3 0 20 40 60 80 100 120 140 160 180 CMS 1G06 10−1 10−2 1en04 v 10−1 10−2 /aM1.5 ta 1 D0.5 0 0 20 20 0.5 0.5 30 30 1 1 40 40 50 50 60 60 70 80 p7T0 [GeV] 2 80 19.7 fb-1 (8 TeV) Data (p~T2 ; p~Tmiss) (bottom-right) variables for the dimuon channel, after the same-sign WW selection criteria have been applied. The data are represented by the black dots and the shaded histograms represent the predicted signal and background processes normalized according to the estimated cross sections and the luminosity. For each individual distribution, the bottom panels show the ratio of the number of events observed in the data to that predicted by the simulation, along with the associated statistical uncertainty. The hatched bands in all cases represent the sum of the systematic and statistical uncertainties of the simulated samples, added in quadrature. The trigger and lepton identi cation e ciencies in the data and simulation are measured using the \tag-and-probe" method [38]. The ratio of the e ciencies obtained from the data and simulation is used to scale the selection e ciency in the simulated samples. The uncertainty on this scale factor for the trigger e ciency is of the order of 1% and is also applied to all the simulated samples. The systematic uncertainty associated with the lepton identi cation e ciency (1% for muons and 4% for electrons) is applied to all simulated samples. The lepton momentum scale has uncertainties due to detector misalignment [38]. For the muons, a momentum scale uncertainty of 1%, independent of its , is 1G06 10−1 10−2 DY Data 20 30 40 50 60 70 80 pT9[0GeV1]00 1 CMS CMS 1G06 5 1t/s05 n 1ve04 E 103 102 10 1 10−1 10−2 /aM1.5 1ad07 r 1506 2 /aM1.5 t 0.5 0.5 30 30 1 1 DY Data (p~T2 ; p~Tmiss) (bottom-left), and (p~T12 ; p~Tmiss) (bottom-right) variables for the electron-muon channel, after the same-sign WW selection criteria have been applied. Symbols and patterns are the same as in gure 2. assigned. A momentum scale uncertainty of 2% is assigned for electrons in the barrel, and 4% for electrons in the endcaps of the ECAL. The lepton momentum scale a ects the nal predicted yields by 1{2% in each channel. The e ects of the jet energy scale uncertainty and the jet energy resolution are evaluated by shifting the pT of the leptons and the jets by their respective uncertainties, with the e ect being propagated to p~miss [47, 48, 52]. These uncertainties cause the predicted event yields to vary by 2{4% for the dimuon and by 5% T for the electron-muon channels, respectively. A scale factor is applied to the simulation to correct for di erent b jet tagging e ciencies and mistag rates measured in the data [53]. This correction is applied by reweighting all the simulated samples on an event-by-event basis, where the weight depends on the avor and kinematics of the jets. This results in an uncertainty of 4% on the b jet dominated background and less than 1% for other background processes. It should be noted that this particular source of systematic uncertainty a ects the electron-muon channel only. To check the normalization of the DY background for the electron-muon channel, a DY-enriched control region is constructed from the data, as de ned in section 4.2. A normalization uncertainty of 10% is derived for the DY background by looking at the ratio of the data to simulation in this control region. backgrounds, a 30% uncertainty is derived for the normalization factor for both of the nal states. The e ects of varying the PDFs and the value of S, as well as the e ect of higher-order corrections, are estimated using the PDF4LHC prescription [54, 55]. 5 The expected and observed upper limits at 95% con dence level (CL) on the cross section for inclusive same-sign WW production via DPS have been extracted. The statistical interpretation of the results is performed using an asymptotic approximation of the CLs method [56{58]. These limits are estimated by tting the shape of the BDT discriminant, using the methodology developed by the ATLAS and CMS collaborations [59]. A log-normal probability distribution function is assumed for the nuisance parameters that a ect the event yields of the signal and various background contributions. Systematic uncertainties a ecting the shape of the BDT discriminant are assumed to have a Gaussian probability distribution function. A binned maximum likelihood t is performed on the selected events while the systematic uncertainties are included in the t as nuisance parameters and are pro led during the minimization [59]. While performing the combination of the results from the two nal states, the systematic uncertainties arising from theoretical predictions or from the background estimation techniques are taken to be fully correlated across the two nal states, while no correlation is assumed for uncertainties of statistical origin. The uncertainty associated with the absolute scale of the integrated luminosity and the e ects of pileup are correlated across the two nal states. Experimental uncertainties on the lepton selection and trigger e ciencies for the same kind of physics objects are assumed to be correlated. Theoretical uncertainties on the production cross sections for each process are correlated across the two nal states. However, the uncertainties on di erent processes are assumed to be independent. for the backgrounds and pre- t ones for the signal, for the dimuon and electron-muon nal states with the corresponding uncertainty bands (shown as hatched bands). The expected and observed 95% CL limits on the cross section for same-sign WW production via DPS ( WDPS W ) are summarized in table 3. The expected value of the DPS cross section derived with the factorization formula DPS W W given by eq. (1.1) is = 0:18 0:06 pb, as obtained for the e ective cross section e = 20:7 6:6 mb measured in the W+2 jets nal state at 7 TeV [21], and the single-parton NNLO cross sections of W+ = 72:1 2:5 nb and W = 50:8 1:9 nb [60] combined. Figure 5 provides a summary of the sensitivity of the BDT-based analysis for the di erent nal states. The expected value of same-sign taken from pythia8 is shown as a red line, while that extracted using the factorization approach is represented DPS W W 1in07 b 1t/s06 n 1ve05 E 104 103 102 10 1 10−1 10−2 C 2 Data DY Data muon channel (right). The data are represented by the black dots and the shaded histograms represent the pre- t signal and post- t background processes. The bottom panels show the ratio of data to the sum of all signal and background contributions. The hatched bands represent the post- t uncertainty, which includes both the statistical and systematic components. 95% CL Expected Expected Expected Observed 1 2 Dimuon production via DPS for the dimuon and electron-muon channels along with their combination. by a blue line. The observed and expected limits are consistent within the statistical uctuations since the observed limits are within the green (68%) or yellow (95%) bands of the expected limit values. The observed limits for the combined analysis are more stringent than the limits from the individual nal states. Assuming the two scatterings to be independent, a limit can be placed on e using eq. (1.1) together with the SPS W+ and W CL limit on e can be calculated as: cross section values at NNLO. A lower 95% The obtained lower limit on e is compatible with the values of e 10{20 mb obtained from measurements at di erent center-of-mass energies using a variety of processes [21]. e > W2+ + 2 W 2 DPS W W = 12:2 mb: Combined Observed Limit Expected Limit Expected ± 1 s.d. Expected ± 2 s.d. PYTHIA 8 prediction Factorization approach HJEP02(18)3 0 nal states, along with their combination. The predicted values of WDPSW from W W pythia8 and from the factorization approach [21] are also shown. 6 A rst search for same-sign W boson pair production via double-parton scattering (DPS) in pp collisions at a center-of-mass energy of 8 TeV has been presented. The analyzed data were collected by the CMS detector at the LHC during 2012 and correspond to an integrated luminosity of 19.7 fb 1. The results presented here are based on the analysis of events containing two same-sign W bosons decaying into either same-sign muon-muon or electron-muon pairs. Several kinematic observables have been studied to identify those that can better discriminate between DPS and the single-parton scattering (SPS) backgrounds. These observables with discriminating power are used as an input to a multivariate analysis based on boosted decision trees. No excess over the expected contributions from SPS processes is observed. A 95% con dence level (CL) upper limit of 0.32 pb is placed on the inclusive cross section for same-sign WW production via DPS. A corresponding 95% CL lower limit of 12.2 mb on the e ective double-parton cross section is also derived, compatible with previous measurements as well as with Monte Carlo event generator expectations. Acknowledgments We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the technical and administrative sta s at CERN and at other CMS institutes for their contributions to the success of the CMS e ort. In addition, we gratefully acknowledge the computing centres and personnel of the Worldwide LHC Computing Grid for delivering so e ectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, RFBR and RAEP (Russia); MESTD (Serbia); SEIDI, CPAN, PCTI and FEDER (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU and SFFR (Ukraine); STFC (United Kingdom); DOE and NSF (U.S.A.). Individuals have received support from the Marie-Curie programme and the European Research Council and Horizon 2020 Grant, contract No. 675440 (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy O ce; the Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Council of Science and Industrial Research, India; the HOMING PLUS programme of the Foundation for Polish Science, co nanced from European Union, Regional Development Fund, the Mobility Plus programme of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/02861, Sonata-bis 2012/07/E/ST2/01406; the National Priorities Research Program by Qatar National Research Fund; the Programa Severo Ochoa del Principado de Asturias; the Thalis and Aristeia programmes co nanced by EU-ESF and the Greek NSRF; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Welch Foundation, contract C-1845; and the Weston Havens Foundation (U.S.A.). 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Dreyer, E. Garutti, D. Gonzalez, J. Haller, A. Hinzmann, M. Ho mann, 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, 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 G. Karathanasis, S. Kesisoglou, A. Panagiotou, N. Saoulidou National Technical University of Athens, Athens, Greece K. Kousouris University of Ioannina, Ioannina, Greece I. Evangelou, C. Foudas, P. Kokkas, S. Mallios, 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.I. Veres19 Wigner Research Centre for Physics, Budapest, Hungary G. Bencze, C. Hajdu, D. Horvath20, A. Hunyadi, F. Sikler, V. Veszpremi, A.J. Zsigmond 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. Bartok19, P. Raics, Z.L. Trocsanyi, B. Ujvari Indian Institute of Science (IISc), Bangalore, India S. Choudhury, J.R. Komaragiri 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, 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 Saha Institute of Nuclear Physics, HBNI, Kolkata, India R. Bhardwaj, R. Bhattacharya, S. Bhattacharya, U. Bhawandeep, 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 HJEP02(18)3 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, P. Shukla, A. Topkar Tata Institute of Fundamental Research-A, Mumbai, India T. Aziz, S. Dugad, B. Mahakud, S. Mitra, G.B. Mohanty, 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, A. Colaleoa, D. Creanzaa;c, L. Cristellaa;b, N. De Filippisa;c, M. De Palmaa;b, F. Erricoa;b, L. Fiorea, G. Iasellia;c, S. Lezkia;b, G. Maggia;c, M. Maggia, G. Minielloa;b, S. Mya;b, S. Nuzzoa;b, A. Pompilia;b, G. Pugliesea;c, R. Radognaa, 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. Battilanaa;b, D. Bonacorsia;b, S. Braibant-Giacomellia;b, R. Campaninia;b, P. Capiluppia;b, A. Castroa;b, F.R. Cavalloa, S.S. Chhibraa, G. Codispotia;b, M. Cu ania;b, G.M. Dallavallea, F. Fabbria, A. Fanfania;b, D. Fasanellaa;b, P. Giacomellia, C. Grandia, L. Guiduccia;b, S. Marcellinia, G. Masettia, A. Montanaria, F.L. Navarriaa;b, A. Perrottaa, A.M. Rossia;b, T. Rovellia;b, G.P. Sirolia;b, N. Tosia 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 L. Viliania;b;15 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, 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 A. Benagliaa, 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, N. Redaellia, 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, N. Bacchettaa, L. Benatoa;b, M. Benettonia, 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, F. Gasparinia;b, U. Gasparinia;b, A. Gozzelinoa, S. Lacapraraa, P. Lujan, M. Margonia;b, N. Pozzobona;b, P. Ronchesea;b, R. Rossina;b, F. Simonettoa;b, E. Torassaa, S. Venturaa, M. Zanettia;b, P. Zottoa;b INFN Sezione di Pavia a, Universita di Pavia b, Pavia, Italy A. Braghieria, A. Magnania, P. Montagnaa;b, S.P. Rattia;b, V. Rea, M. Ressegottia;b, 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, M. Biasinia;b, G.M. Bileia, C. Cecchia;b, D. Ciangottinia;b, L. Fanoa;b, P. Laricciaa;b, R. Leonardia;b, E. Manonia, G. Mantovania;b, V. Mariania;b, M. Menichellia, A. Rossia;b, A. Santocchiaa;b, D. Spigaa INFN Sezione di Pisa a, Universita di Pisa b, Scuola Normale Superiore di Pisa c, Pisa, Italy K. Androsova, P. Azzurria;15, G. Bagliesia, 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, A. Messineoa;b, F. Pallaa, A. Rizzia;b, A. Savoy-Navarroa;31, P. Spagnoloa, R. Tenchinia, 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, N. Dacia, D. Del Rea;b;15, E. Di Marcoa;b, M. Diemoza, S. Gellia;b, E. Longoa;b, F. Margarolia;b, B. Marzocchia;b, HJEP02(18)3 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, 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, C.S. Moon, Y.D. Oh, S. Sekmen, D.C. Son, Y.C. Yang Chonbuk National University, Jeonju, Korea A. Lee 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.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 Sungkyunkwan University, Suwon, Korea Y. Choi, C. Hwang, J. Lee, I. Yu Vilnius University, Vilnius, Lithuania V. Dudenas, A. Juodagalvis, J. Vaitkus 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, 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, HJEP02(18)3 Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico Reyes-Almanza, R, Ramirez-Sanchez, G., Duran-Osuna, M. C., H. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-De La Cruz34, Rabadan-Trejo, R. I., 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 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, M. Szleper, P. Zalewski Warsaw, Poland Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 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, A. Di Francesco, P. Faccioli, B. Galinhas, M. Gallinaro, J. Hollar, N. Leonardo, L. Lloret Iglesias, M.V. Nemallapudi, J. Seixas, G. Strong, O. Toldaiev, D. Vadruccio, J. Varela Joint Institute for Nuclear Research, Dubna, Russia A. Baginyan, A. Golunov, I. Golutvin, V. Karjavin, V. Korenkov, G. Kozlov, A. Lanev, A. Malakhov, V. Matveev36;37, V.V. Mitsyn, V. Palichik, V. Perelygin, S. Shmatov, V. Smirnov, N. Voytishin, B.S. Yuldashev38, A. Zarubin, V. Zhiltsov Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia Y. Ivanov, V. Kim39, E. Kuznetsova40, 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 Moscow Institute of Physics and Technology, Moscow, Russia T. Aushev, A. Bylinkin37 National Research Nuclear University 'Moscow Engineering Physics Institute' (MEPhI), Moscow, Russia M. Chadeeva41, P. Parygin, D. Philippov, S. Polikarpov, E. Popova, V. Rusinov 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 A. Snigirev A. Baskakov, A. Belyaev, E. Boos, A. Ershov, A. Gribushin, L. Khein, V. Klyukhin, O. Kodolova, I. Lokhtin, O. Lukina, I. Miagkov, S. Obraztsov, S. Petrushanko, V. Savrin, Novosibirsk State University (NSU), Novosibirsk, Russia V. Blinov42, D. Shtol42, Y. Skovpen42 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. 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, D. Moran, 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 C. Albajar, J.F. de Troconiz, M. Missiroli 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, P. Vischia, J.M. Vizan Garcia Instituto de F sica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain I.J. Cabrillo, A. Calderon, B. Chazin Quero, E. Curras, J. Duarte Campderros, 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, M. Dobson, T. du Pree, M. Dunser, N. Dupont, A. Elliott-Peisert, P. Everaerts, F. Fallavollita, G. Franzoni, J. Fulcher, W. Funk, D. Gigi, A. Gilbert, K. Gill, F. Glege, D. Gulhan, P. Harris, J. Hegeman, V. Innocente, P. Janot, O. Karacheban18, J. Kieseler, H. Kirschenmann, V. Knunz, A. Kornmayer15, M.J. Kortelainen, M. Krammer1, 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. Milenovic44, F. Moortgat, M. Mulders, H. Neugebauer, J. Ngadiuba, S. Orfanelli, L. Orsini, L. Pape, E. Perez, M. Peruzzi, A. Petrilli, G. Petrucciani, A. Pfei er, M. Pierini, A. Racz, T. Reis, G. Rolandi45, M. Rovere, H. Sakulin, C. Schafer, C. Schwick, M. Seidel, M. Selvaggi, A. Sharma, P. Silva, P. Sphicas46, A. Stakia, J. Steggemann, M. Stoye, M. Tosi, D. Treille, A. Triossi, A. Tsirou, V. Veckalns47, M. Verweij, W.D. Zeuner Paul Scherrer Institut, Villigen, Switzerland W. Bertly, L. Caminada48, K. Deiters, W. Erdmann, R. Horisberger, Q. Ingram, H.C. Kaestli, D. Kotlinski, U. Langenegger, T. Rohe, S.A. Wiederkehr ETH Zurich - Institute for Particle Physics and Astrophysics (IPA), Zurich, Switzerland 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. Reichmann, M. Schonenberger, L. Shchutska, V.R. Tavolaro, K. Theo latos, M.L. Vesterbacka Olsson, R. Wallny, D.H. Zhu Universitat Zurich, Zurich, Switzerland T.K. Aarrestad, C. Amsler49, M.F. Canelli, A. De Cosa, R. Del Burgo, S. Donato, C. Galloni, T. Hreus, B. Kilminster, D. Pinna, G. Rauco, P. Robmann, D. Salerno, C. Seitz, Y. Takahashi, A. Zucchetta National Central University, Chung-Li, Taiwan V. Candelise, T.H. Doan, Sh. Jain, R. Khurana, C.M. Kuo, W. Lin, A. Pozdnyakov, S.S. Yu Thailand Turkey C. Zorbilmez 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, E. Paganis, A. Psallidas, A. Steen, 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, M.N. Bakirci50, F. Boran, S. Cerci51, S. Damarseckin, Z.S. Demiroglu, C. Dozen, E. Eskut, S. Girgis, G. Gokbulut, Y. Guler, I. Hos52, E.E. Kangal53, O. Kara, U. Kiminsu, M. Oglakci, G. Onengut54, K. Ozdemir55, A. Polatoz, H. Topakli50, S. Turkcapar, I.S. Zorbakir, Middle East Technical University, Physics Department, Ankara, Turkey B. Bilin, G. Karapinar56, K. Ocalan57, M. Yalvac, M. Zeyrek Bogazici University, Istanbul, Turkey E. Gulmez, M. Kaya58, O. Kaya59, S. Tekten, E.A. Yetkin60 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 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, O. Davignon, H. Flacher, J. Goldstein, M. Grimes, G.P. Heath, H.F. Heath, J. Jacob, L. Kreczko, C. Lucas, D.M. Newbold61, 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. Belyaev62, 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 G. Auzinger, R. Bainbridge, J. Borg, 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, A. Elwood, 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. Nikitenko6, V. Palladino, M. Pesaresi, D.M. Raymond, A. Richards, A. Rose, E. Scott, C. Seez, A. Shtipliyski, S. Summers, A. Tapper, K. Uchida, M. Vazquez Acosta63, T. Virdee15, N. Wardle, 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, M. Turner Baylor University, Waco, U.S.A. A. Borzou, K. Call, J. Dittmann, K. Hatakeyama, H. Liu, N. Pastika, C. Smith 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 D. Yu 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, J. Pazzini, S. Piperov, S. Sagir, R. Syarif, University of California, Davis, Davis, U.S.A. R. Band, C. Brainerd, R. Breedon, 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, 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, S. Regnard, 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, E. Kennedy, F. Lacroix, O.R. Long, M. Olmedo Negrete, M.I. Paneva, A. Shrinivas, W. Si, L. Wang, H. Wei, S. Wimpenny, B. R. Yates University of California, San Diego, La Jolla, U.S.A. J.G. Branson, S. Cittolin, M. Derdzinski, R. Gerosa, 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. Wasserbaech64, 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, M. Alyari, G. Apollinari, A. Apresyan, A. Apyan, S. Banerjee, L.A.T. Bauerdick, A. Beretvas, J. Berryhill, P.C. Bhat, G. Bollay, 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, 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, D. Bourilkov, A. Brinkerho , A. Carnes, M. Carver, D. Curry, 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, 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, G. Martinez, T. Perry, H. Prosper, A. Saha, A. Santra, V. Sharma, 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. Bilki65, W. Clarida, K. Dilsiz66, S. Durgut, R.P. Gandrajula, M. Haytmyradov, V. Khristenko, J.-P. Merlo, H. Mermerkaya67, A. Mestvirishvili, A. Moeller, J. Nachtman, H. Ogul68, Y. Onel, F. Ozok69, 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, 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 HJEP02(18)3 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. J. Dolen, A. Godshalk, C. Harrington, I. Iashvili, D. Nguyen, A. Parker, S. Rappoccio, B. Roozbahani Northeastern University, Boston, U.S.A. R. Teixeira De Lima, D. Trocino, D. Wood Northwestern University, Evanston, U.S.A. G. Alverson, E. Barberis, A. Hortiangtham, A. Massironi, D.M. Morse, T. Orimoto, 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. S. Cooperstein, O. Driga, P. Elmer, J. Hardenbrook, P. Hebda, S. Higginbotham, D. Lange, J. Luo, D. Marlow, K. Mei, I. Ojalvo, J. Olsen, C. Palmer, P. Piroue, D. Stickland, 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. Das, S. Folgueras, L. Gutay, M.K. Jha, M. Jones, A.W. Jung, A. Khatiwada, D.H. Miller, N. Neumeister, C.C. Peng, 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. A.G. Delannoy, M. Foerster, J. Heideman, G. Riley, K. Rose, S. Spanier, K. Thapa Texas A&M University, College Station, U.S.A. O. Bouhali70, A. Castaneda Hernandez70, A. Celik, M. Dalchenko, M. De Mattia, A. Delgado, S. Dildick, R. Eusebi, J. Gilmore, T. Huang, T. Kamon71, 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, K. Padeken, P. Sheldon, S. Tuo, J. Velkovska, Q. Xu University of Virginia, Charlottesville, U.S.A. M.W. Arenton, P. Barria, B. Cox, R. Hirosky, M. Joyce, A. Ledovskoy, H. Li, C. Neu, T. Sinthuprasith, Y. Wang, E. Wolfe, F. Xia Wayne State University, Detroit, U.S.A. R. Harr, P.E. Karchin, J. Sturdy, S. Zaleski University of Wisconsin - Madison, Madison, WI, U.S.A. M. Brodski, 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. 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 Institute for Theoretical and Experimental Physics, Moscow, Russia 7: Also at Joint Institute for Nuclear Research, Dubna, Russia 8: Also at Suez University, Suez, Egypt 9: Now at British University in Egypt, Cairo, Egypt 10: Also at Fayoum University, El-Fayoum, Egypt 11: Now at Helwan University, Cairo, Egypt 12: Also at Universite de Haute Alsace, Mulhouse, France HJEP02(18)3 Moscow, Russia 14: Also at Tbilisi 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 MTA-ELTE Lendulet CMS Particle and Nuclear Physics Group, Eotvos Lorand University, Budapest, Hungary 20: Also at Institute of Nuclear Research ATOMKI, Debrecen, 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 Uzbekistan 38: Also at Institute of Nuclear Physics of the Uzbekistan Academy of Sciences, Tashkent, 39: Also at St. Petersburg State Polytechnical University, St. Petersburg, Russia 40: Also at University of Florida, Gainesville, U.S.A. 41: Also at P.N. Lebedev Physical Institute, Moscow, Russia 42: Also at Budker Institute of Nuclear Physics, Novosibirsk, Russia 43: Also at Faculty of Physics, University of Belgrade, Belgrade, Serbia 44: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia 45: Also at Scuola Normale e Sezione dell'INFN, Pisa, Italy 46: Also at National and Kapodistrian University of Athens, Athens, Greece 47: Also at Riga Technical University, Riga, Latvia 48: Also at Universitat Zurich, Zurich, Switzerland 49: Also at Stefan Meyer Institute for Subatomic Physics (SMI), Vienna, Austria 50: Also at Gaziosmanpasa University, Tokat, Turkey 51: Also at Adiyaman University, Adiyaman, Turkey 52: Also at Istanbul Aydin University, Istanbul, Turkey 53: Also at Mersin University, Mersin, Turkey 54: Also at Cag University, Mersin, Turkey 56: Also at Izmir Institute of Technology, Izmir, Turkey 57: Also at Necmettin Erbakan University, Konya, Turkey 58: Also at Marmara University, Istanbul, Turkey 59: Also at Kafkas University, Kars, Turkey 60: Also at Istanbul Bilgi University, Istanbul, Turkey 61: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom 62: Also at School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom 63: Also at Instituto de Astrof sica de Canarias, La Laguna, Spain 64: Also at Utah Valley University, Orem, U.S.A. 65: Also at Beykent University, Istanbul, Turkey 66: Also at Bingol University, Bingol, Turkey 67: Also at Erzincan University, Erzincan, Turkey 68: Also at Sinop University, Sinop, Turkey 69: Also at Mimar Sinan University, Istanbul, Istanbul, Turkey 70: Also at Texas A&M University at Qatar, Doha, Qatar 71: Also at Kyungpook National University, Daegu, Korea [3] J.R. Gaunt , C.-H. Kom , A. Kulesza and W.J. Stirling , Same-sign W pair production as a probe of double parton scattering at the LHC , Eur. Phys. J. C 69 ( 2010 ) 53 [4] G. Calucci and D. Treleani , Disentangling correlations in multiple parton interactions , Phys. Rev. D 83 ( 2011 ) 016012 [arXiv: 1009 .5881] [INSPIRE]. [5] M. Rinaldi , S. Scopetta , M. Traini and V. Vento , Double parton correlations and constituent quark models: a light front approach to the valence sector , JHEP 12 ( 2014 ) 028 [6] M. Diehl , D. Ostermeier and A. Sch afer, Elements of a theory for multiparton interactions in [22] M. Bahr , M. Myska, M.H. Seymour and A. Siodmok , Extracting e ective from the CDF [24] D. Treleani , Double parton scattering, di raction and e ective cross section , Phys. Rev . D [28] T. Sj ostrand, S. Mrenna and P.Z. Skands , A brief introduction to PYTHIA 8:1, Comput . Phys. Commun . 178 ( 2008 ) 852 [arXiv: 0710 .3820] [INSPIRE]. [29] R. Corke and T. 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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, 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, 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, Q. Python, K. Skovpen, S. Tavernier, W. Van Doninck, P. Van Mulders, I. Van Parijs, D. Beghin, H. Brun, B. Clerbaux, G. De Lentdecker, H. Delannoy, B. Dorney, G. Fasanella, L. Favart, R. Goldouzian, A. Grebenyuk, G. Karapostoli, T. Lenzi, J. Luetic, T. Maerschalk, A. Marinov, A. Randle-conde, T. Seva, C. Vander Velde, P. Vanlaer, D. Vannerom, R. Yonamine, F. Zenoni, F. Zhang, A. Cimmino, T. Cornelis, D. Dobur, A. Fagot, M. Gul, I. Khvastunov, D. Poyraz, C. Roskas, S. Salva, M. Tytgat, W. Verbeke, N. Zaganidis, H. Bakhshiansohi, O. Bondu, S. Brochet, G. Bruno, C. Caputo, A. Caudron, S. De Visscher, C. Delaere, M. Delcourt, B. Francois, A. Giammanco, A. Jafari, M. Komm, G. Krintiras, V. Lemaitre, A. Magitteri, A. Mertens, M. Musich, K. Piotrzkowski, L. Quertenmont, M. Vidal Marono, S. Wertz, N. Beliy, W. L. Aldá Júnior, F. L. Alves, G. A. Alves, L. Brito, M. Correa Martins Junior, C. Hensel, A. Moraes, M. E. Pol, P. Rebello Teles, E. Belchior Batista Das Chagas, W. Carvalho, J. Chinellato, E. Coelho, E. M. Da Costa, G. G. Da Silveira, D. De Jesus Damiao, S. Fonseca De Souza, L. M. Huertas Guativa, H. Malbouisson, M. Melo De Almeida, C. Mora Herrera, L. Mundim, H. Nogima, A. Santoro, A. Sznajder, E. J. Tonelli Manganote, F. Torres Da Silva De Araujo, A. Vilela Pereira, S. Ahuja, C. A. Bernardes, T. R. Fernandez Perez Tomei, E. M. Gregores, P. G. Mercadante, S. F. Novaes, Sandra S. Padula, D. Romero Abad, J. C. Ruiz Vargas, A. Aleksandrov, R. Hadjiiska, P. Iaydjiev, M. Misheva, M. Rodozov, M. Shopova, G. Sultanov, A. Dimitrov, I. Glushkov, L. Litov, B. Pavlov, P. Petkov, W. Fang, X. Gao, M. Ahmad, J. G. Bian, G. M. Chen, H. S. Chen, M. Chen, Y. Chen, C. H. Jiang, D. Leggat, H. Liao, Z. Liu, F. Romeo, S. M. Shaheen, A. Spiezia, J. Tao, C. Wang, Z. Wang, E. Yazgan, H. Zhang, S. Zhang, J. Zhao, Y. Ban, G. Chen, Q. Li, S. Liu, Y. Mao, S. J. Qian, D. Wang, Z. Xu, C. Avila, A. Cabrera, L. F. Chaparro Sierra, C. Florez, C. F. González Hernández, J. D. Ruiz Alvarez, B. Courbon, N. Godinovic, D. Lelas, I. Puljak, P. M. Ribeiro Cipriano, T. Sculac, Z. Antunovic, M. Kovac, V. Brigljevic, D. Ferencek, K. Kadija, B. Mesic, A. Starodumov, T. Susa, M. W. Ather, A. Attikis, G. Mavromanolakis, J. Mousa, C. Nicolaou, F. Ptochos, P. A. Razis, H. Rykaczewski, M. Finger, M. Finger, E. Carrera Jarrin, Y. Assran, M. A. Mahmoud, A. Mahrous, R. K. Dewanjee, M. Kadastik, L. Perrini, M. Raidal, A. Tiko, C. Veelken, P. Eerola, J. Pekkanen, M. Voutilainen, T. Järvinen, V. Karimäki, R. Kinnunen, T. Lampén, K. Lassila-Perini, S. Lehti, T. Lindén, P. Luukka, E. Tuominen, J. Tuominiemi, J. Talvitie, T. Tuuva, 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. Ö. Sahin, M. Titov, A. Abdulsalam, C. Amendola, I. Antropov, S. Baffioni, F. Beaudette, P. Busson, L. Cadamuro, C. Charlot, R. Granier de Cassagnac, M. Jo, S. Lisniak, A. Lobanov, J. Martin Blanco, M. Nguyen, C. Ochando, G. Ortona, P. Paganini, P. Pigard, R. Salerno, J. B. Sauvan, Y. Sirois, A. G. Stahl Leiton, T. Strebler, Y. Yilmaz, A. Zabi, A. 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Kress, A. Künsken. Constraints on the double-parton scattering cross section from same-sign W boson pair production in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV, Journal of High Energy Physics, 2018, 32, DOI: 10.1007/JHEP02(2018)032