Measurements of the $$\mathrm {p}\mathrm {p}\rightarrow \mathrm{Z}\mathrm{Z}$$ production cross section and the $$\mathrm{Z}\rightarrow 4\ell $$Z→4ℓ branching fraction, and constraints on anomalous triple gauge couplings at $$\sqrt{s} = 13\,\text {TeV} $$s=13TeV
Eur. Phys. J. C
Measurements of the pp → ZZ production cross section and the Z → 4 branching fraction, and constraints on anomalous triple √ gauge couplings at s = 13 TeV
CMS Collaboration 0 1 2 3 6 7
0 CERN , 1211 Geneva 23 , Switzerland
1 Universiteit Antwerpen, Antwerpen, Belgium E. A. De Wolf , D. Di Croce, X. Janssen, J. Lauwers, M. Van De Klundert, H. Van Haevermaet, P. Van Mechelen, N. Van Remortel
2 University of Split, Faculty of Science , Split , Croatia Z. Antunovic, M. Kovac
3 Wigner Research Centre for Physics , Budapest, Hungary G. Bencze, C. Hajdu, D. Horvath
4 , Á. Hunyadi , F. Sikler, V. Veszpremi, G. Vesztergombi
5 , A. J. Zsigmond
6 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. Matveev
7 Institute of Experimental Physics, Faculty of Physics, University of Warsaw , Warsaw , Poland K. Bunkowski, A. Byszuk
8 , K. Doroba , A. Kalinowski, M. Konecki, J. Krolikowski, M. Misiura, M. Olszewski, A. Pyskir, M. Walczak
Four-lepton production in proton-proton collisions, pp → (Z/γ ∗)(Z/γ ∗) → 4 , where = e or μ, is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb−1. The ZZ production cross section, σ (pp → ZZ) = 17.2 ± 0.5 (stat) ± 0.7 (syst) ± 0.4 (theo) ± 0.4 (lumi) pb, measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 < m + − < 120 GeV, is consistent with standard model predictions. Differential cross sections are measured and are well described by the theoretical predictions. The Z boson branching fraction to four leptons is measured to be mass in the range 80 < m4 < 100 GeV and a dilepton mass m > 4 GeV for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings at 95% confidence level: − 0.0012 < f4Z < 0.0010, − 0.0010 < f5Z < 0.0013, − 0.0012 < f4γ < 0.0013, − 0.0012 < f5γ < 0.0013.
-
1 Introduction
Measurements of diboson production at the CERN LHC
allow precision tests of the standard model (SM). In the SM,
ZZ production proceeds mainly through quark-antiquark t
and u-channel scattering diagrams. In calculations at higher
orders in quantum chromodynamics (QCD), gluon-gluon
fusion also contributes via box diagrams with quark loops.
There are no tree-level contributions to ZZ production from
triple gauge boson vertices in the SM. Anomalous triple
gauge couplings (aTGC) could be induced by new physics
models such as supersymmetry [
1
]. Nonzero aTGCs may be
parametrized using an effective Lagrangian as in Ref. [
2
].
In this formalism, two ZZZ and two ZZγ couplings are
allowed by electromagnetic gauge invariance and Lorentz
invariance for on-shell Z bosons. These are described by two
CP-violating ( f4V) and two CP-conserving ( f5V) parameters,
where V = Z or γ .
Previous measurements of the ZZ production cross
section by the CMS Collaboration were performed for pairs of
on-shell Z bosons, produced in the dilepton mass range 60–
120 GeV [
3–6
]. These measurements were made with data
sets corresponding to integrated luminosities of 5.1 fb−1 at
√s = 7 TeV and 19.6 fb−1 at √s = 8 TeV in the ZZ →
2 2 and ZZ → 2 2ν decay channels, where = e or μ
and = e, μ, or τ , and with an integrated luminosity of
2.6 fb−1 at √s = 13 TeV in the ZZ → 2 2 decay
channel, where = e or μ. All of them agree with SM
predictions. The ATLAS Collaboration produced similar results
at √s = 7, 8, and 13 TeV [
7–10
], which also agree with
the SM. These measurements are important for testing
predictions that were recently made available at
next-to-nextto-leading order (NNLO) in QCD [
11
]. Comparing these
predictions with data at a range of center-of-mass energies
provides information about the electroweak gauge sector of
the SM. Because the uncertainty of the CMS measurement at
√s = 13 TeV [
6
] was dominated by the statistical uncertainty
of the observed data, repeating and extending the
measurement with a larger sample of proton-proton collision data at
√s = 13 TeV improves the precision of the results.
The most stringent previous limits on ZZZ and ZZγ
aTGCs from CMS were set using the 7 and 8 TeV data
samples: − 0.0022 < f4Z < 0.0026, − 0.0023 < f5Z < 0.0023,
− 0.0029 < f4γ < 0.0026, and − 0.0026 < f5γ < 0.0027
at 95% confidence level (CL) [
4,5
]. Similar limits were
obtained by the ATLAS Collaboration [12], who also recently
produced limits using 13 TeV data [
10
].
Extending the dilepton mass range to lower values allows
measurements of (Z/γ ∗) (Z/γ ∗) production, where Z
indicates an on-shell Z boson or an off-shell Z∗ boson. The
resulting sample includes Higgs boson events in the H → ZZ∗ →
2 2 channel, and rare decays of a single Z boson to four
leptons. The Z → + −γ ∗ → 2 2 decay was studied
in detail at LEP [
13
] and was observed in pp collisions by
CMS [
6,14
] and ATLAS [15]. Although the branching
fraction for this decay is orders of magnitude smaller than that
for the Z → + − decay, the precisely known mass of the
Z boson makes the four-lepton mode useful for calibrating
mass measurements of the nearby Higgs boson resonance.
This paper reports a study of four-lepton production
(pp → 2 2 , where 2 and 2 indicate opposite-sign pairs
of electrons or muons) at √s = 13 TeV with a data set
corresponding to an integrated luminosity of 35.9 ± 0.9 fb−1
recorded in 2016. Cross sections are measured for
nonresonant production of pairs of Z bosons, pp → ZZ, where both Z
bosons are produced on-shell, defined as the mass range 60–
120 GeV, and resonant pp → Z → 4 production. Detailed
discussion of resonant Higgs boson production decaying to
ZZ∗, is beyond the scope of this paper and may be found in
Ref. [
16
].
2 The CMS detector
A detailed description of the CMS detector, together with
a definition of the coordinate system used and the relevant
kinematic variables, can be found in Ref. [
17
].
The central feature of the CMS apparatus is a
superconducting solenoid of 6 m internal diameter, providing a
magnetic field 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, which provide coverage in
pseudorapidity |η| < 1.479 in a cylindrical barrel and 1.479 < |η| < 3.0
in two endcap regions. Forward calorimeters extend the
coverage provided by the barrel and endcap detectors to
|η| < 5.0. Muons are measured in gas-ionization detectors
embedded in the steel flux-return yoke outside the solenoid
in the range |η| < 2.4, with detection planes made using
three technologies: drift tubes, cathode strip chambers, and
resistive plate chambers.
Electron momenta are estimated by combining energy
measurements in the ECAL with momentum measurements
in the tracker. The momentum resolution for electrons with
transverse momentum pT ≈ 45 GeV from Z → e+e−
decays ranges from 1.7% for nonshowering electrons in
the barrel region to 4.5% for showering electrons in the
endcaps [
18
]. Matching muons to tracks identified in the
silicon tracker results in a pT 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 [
19
].
3 Signal and background simulation
Signal events are generated with powheg 2.0 [
20–24
] at
nextto-leading order (NLO) in QCD for quark-antiquark
processes and leading order (LO) for quark-gluon processes.
This includes ZZ, Zγ ∗, Z, and γ ∗γ ∗ production with a
constraint of m > 4 GeV applied to all pairs of
oppositely charged leptons at the generator level to avoid infrared
divergences. The gg → ZZ process is simulated at LO
with mcfm v7.0 [
25
]. These samples are scaled to
correspond to cross sections calculated at NNLO in QCD for
qq → ZZ [
11
] (a scaling K factor of 1.1) and at NLO in
QCD for gg → ZZ [
26
] (K factor of 1.7). The gg → ZZ
process is calculated to O αs3 , where αs is the strong
coupling constant, while the other contributing processes are
calculated to O αs2 ; this higher-order correction is included
because the effect is known to be large [
26
]. Electroweak
ZZ production in association with two jets is generated with
Phantom v1.2.8 [
27
].
A sample of Higgs boson events is produced in the
gluongluon fusion process at NLO with powheg. The Higgs boson
decay is modeled with jhugen 3.1.8 [
28–30
]. Its cross
section is scaled to the NNLO prediction with a K factor of
1.7 [
26
].
Samples for background processes containing four prompt
leptons in the final state, ttZ and WWZ production, are
produced with MadGraph5_amc@nlo v2.3.3 [
31
]. The
qq → WZ process is generated with powheg.
Samples with aTGC contributions included are
generated at LO with sherpa v2.1.1 [
32
]. Distributions from the
sherpa samples are normalized such that the total yield of
the SM sample is the same as that of the powheg sample.
The pythia v8.175 [
23,33,34
] package is used for parton
showering, hadronization, and the underlying event
simulation, with parameters set by the CUETP8M1 tune [
35
], for all
samples except the samples generated with sherpa, which
performs these functions itself. The NNPDF 3.0 [
36
] set is
used as the default set of parton distribution functions (PDFs).
For all simulated event samples, the PDFs are calculated to
the same order in QCD as the process in the sample.
The detector response is simulated using a detailed
description of the CMS detector implemented with the
Geant4 package [
37
]. The event reconstruction is
performed with the same algorithms used for data. The simulated
samples include additional interactions per bunch crossing,
referred to as pileup. The simulated events are weighted so
that the pileup distribution matches the data, with an average
of about 27 interactions per bunch crossing.
4 Event reconstruction
All long-lived particles—electrons, muons, photons, and
charged and neutral hadrons—in each collision event are
identified and reconstructed with the CMS particle-flow (PF)
algorithm [
38
] from a combination of the signals from all
subdetectors. Reconstructed electrons [
18
] and muons [
19
] are
considered candidates for inclusion in four-lepton final states
if they have pTe > 7 GeV and |ηe| < 2.5 or pTμ > 5 GeV and
|ημ| < 2.4.
Lepton candidates are also required to originate from
the event vertex, defined as the reconstructed proton-proton
interaction vertex with the largest value of summed physics
object pT2. The physics objects used in the event vertex
definition are the objects returned by a jet finding algorithm [
39,40
]
applied to all charged tracks associated with the vertex, plus
the corresponding associated missing transverse
momentum [41]. The distance of closest approach between each
lepton track and the event vertex is required to be less than
0.5 cm in the plane transverse to the beam axis, and less
than 1 cm in the direction along the beam axis. Furthermore,
the significance of the three-dimensional impact parameter
relative to the event vertex, SIP3D, is required to satisfy
SIP3D ≡ |IP/σIP| < 10 for each lepton, where IP is the
distance of closest approach of each lepton track to the event
vertex and σIP is its associated uncertainty.
Lepton candidates are required to be isolated from other
particles in the event. The relative isolation is defined as
Riso =
pT + max 0,
pT +
pT − pTPU
charged
hadrons
neutral
hadrons
photons
pT,
(1)
where the sums run over the charged and neutral hadrons and
photons identified by the PF algorithm, in a cone defined by
√
R ≡ ( η)2 + ( φ)2 < 0.3 around the lepton
trajectory. Here φ is the azimuthal angle in radians. To minimize
the contribution of charged particles from pileup to the
isolation calculation, charged hadrons are included only if they
originate from the event vertex. The contribution of neutral
particles from pileup is pTPU. For electrons, pPU is
evaluT
ated with the “jet area” method described in Ref. [
42
]; for
muons, it is taken to be half the sum of the pT of all charged
particles in the cone originating from pileup vertices. The
factor one-half accounts for the expected ratio of charged to
neutral particle energy in hadronic interactions. A lepton is
considered isolated if Riso < 0.35.
The lepton reconstruction, identification, and isolation
efficiencies are measured with a “tag-and-probe”
technique [
43
] applied to a sample of Z → + − data events.
The measurements are performed in several bins of pT and
|η |. The electron reconstruction and selection efficiency in
the ECAL barrel (endcaps) varies from about 85% (77%)
at pTe ≈ 10 GeV to about 95% (89%) for pTe ≥ 20 GeV,
while in the barrel-endcap transition region this efficiency
is about 85% averaged over all electrons with pTe > 7 GeV.
The muons are reconstructed and identified with efficiencies
above ∼ 98% within |ημ| < 2.4.
5 Event selection
The primary triggers for this analysis require the presence
of a pair of loosely isolated leptons of the same or different
flavors [
44
]. The highest pT lepton must have pT > 17 GeV,
and the subleading lepton must have pTe > 12 GeV if it is
an electron or pTμ > 8 GeV if it is a muon. The tracks of the
triggering leptons are required to originate within 2 mm of
each other in the plane transverse to the beam axis. Triggers
requiring a triplet of lower- pT leptons with no isolation
criterion, or a single high- pT electron or muon, are also used.
An event is used if it passes any trigger regardless of the
decay channel. The total trigger efficiency for events within
the acceptance of this analysis is greater than 98%.
The four-lepton candidate selections are based on those
used in Ref. [
45
]. A signal event must contain at least two
Z/γ ∗ candidates, each formed from an oppositely charged
pair of isolated electron candidates or muon candidates.
Among the four leptons, the highest pT lepton must have
pT > 20 GeV, and the second-highest pT lepton must have
pTe > 12 GeV if it is an electron or pTμ > 10 GeV if it is
a muon. All leptons are required to be separated from each
other by R ( 1, 2) > 0.02, and electrons are required to
be separated from muons by R (e, μ) > 0.05.
Within each event, all permutations of leptons giving a
valid pair of Z/γ ∗ candidates are considered separately.
Within each 4 candidate, the dilepton candidate with an
invariant mass closest to 91.2 GeV, taken as the nominal Z
boson mass [
46
], is denoted Z1 and is required to have a mass
greater than 40 GeV. The other dilepton candidate is denoted
Z2. Both mZ1 and mZ2 are required to be less than 120 GeV.
All pairs of oppositely charged leptons in the 4 candidate
are required to have m > 4 GeV regardless of their flavor.
If multiple 4 candidates within an event pass all
selections, the one with mZ1 closest to the nominal Z boson mass
is chosen. In the rare case of further ambiguity, which may
arise in less than 0.5% of events when five or more passing
lepton candidates are found, the Z2 candidate that maximizes
the scalar pT sum of the four leptons is chosen.
Additional requirements are applied to select events for
measurements of specific processes. The pp → ZZ cross
section is measured using events where both mZ1 and mZ2
are greater than 60 GeV. The Z → 4 branching fraction is
measured using events with 80 < m4 < 100 GeV, a range
chosen to retain most of the decays in the resonance while
removing most other processes with four-lepton final states.
Decays of the Z bosons to τ leptons with subsequent decays
to electrons and muons are heavily suppressed by
requirements on lepton pT, and the contribution of such events is
less than 0.5% of the total ZZ yield. If these events pass the
selection requirements of the analysis, they are considered
signal, while they are not considered at generator level in the
cross section unfolding procedure. Thus, the correction for
possible τ decays is included in the efficiency calculation.
6 Background estimate
The major background contributions arise from Z boson and
WZ diboson production in association with jets and from tt
production. In all these cases, particles from jet fragmentation
satisfy both lepton identification and isolation criteria, and
are thus misidentified as signal leptons.
The probability for such objects to be selected is measured
from a sample of Z + candidate events, where Z denotes a
pair of oppositely charged, same-flavor leptons that pass all
analysis requirements and satisfy |m + − − mZ| < 10 GeV,
where mZ is the nominal Z boson mass. Each event in this
sample must have exactly one additional object candidate that
passes relaxed identification requirements with no isolation
requirements applied. The misidentification probability for
each lepton flavor, measured in bins of lepton candidate pT
and η, is defined as the ratio of the number of candidates that
pass the final isolation and identification requirements to the
total number in the sample. The number of Z + candidate
events is corrected for the contamination from WZ
production and ZZ production in which one lepton is not
reconstructed. These events have a third genuine, isolated lepton
that must be excluded from the misidentification probability
calculation. The WZ contamination is suppressed by
requiring the missing transverse momentum pmiss to be below
T
25 GeV. The pmiss is defined as the magnitude of the missing
T
transverse momentum vector p miss, the projection onto the
T
plane transverse to the beams of the negative vector sum of
the momenta of all reconstructed PF candidates in the event,
corrected for the jet energy scale. Additionally, the
transverse mass calculated with p miss and the pT of candidate,
mT ≡ √( pT + pTmiss)2 − ( pTT+ pTmiss)2, is required to be
less than 30 GeV. The residual contribution of WZ and ZZ
events, which may be up to a few percent of the events with
candidate passing all selection criteria, is estimated from
simulation and subtracted.
To account for all sources of background events, two
control samples are used to estimate the number of background
events in the signal regions. Both are defined to contain events
with a dilepton candidate satisfying all requirements (Z1) and
two additional lepton candidates + −. In one control
sample, enriched in WZ events, one candidate is required to
satisfy the full identification and isolation criteria and the other
must fail the full criteria and instead satisfy only the relaxed
ones; in the other, enriched in Z+jets events, both
candi6–10
2–4
1–2
0.6–1.3
1–2
1
1
2.5
dates must satisfy the relaxed criteria, but fail the full
criteria. The additional leptons must have opposite charge and
the same flavor (e±e∓, μ±μ∓). From this set of events, the
expected number of background events in the signal region,
denoted “Z + X” in the figures, is obtained by scaling the
number of observed Z1 + + − events by the
misidentification probability for each lepton failing the selection. It is
found to be approximately 4% of the total expected yield.
The procedure is described in more detail in Ref. [
45
].
In addition to these nonprompt backgrounds, ttZ and
WWZ processes contribute a smaller number of events with
four prompt leptons, which is estimated from simulated
samples to be around 1% of the expected ZZ → 4 yield. In
the Z → 4 selection, the contribution from these
backgrounds is negligible. The total background contributions to
the Z → 4 and ZZ → 4 signal regions are summarized in
Sect. 8.
7 Systematic uncertainties
The major sources of systematic uncertainty and their effect
on the measured cross sections are summarized in Table 1.
In both data and simulated event samples, trigger efficiencies
are evaluated with a tag-and-probe technique. The ratio of
data to simulation is applied to simulated events, and the
size of the resulting change in expected yield is taken as
the uncertainty in the determination of the trigger efficiency.
This uncertainty is around 2% of the final estimated yield.
For Z → 4e events, the uncertainty increases to 4%.
The lepton identification, isolation, and track
reconstruction efficiencies in simulation are corrected with scaling
factors derived with a tag-and-probe method and applied as a
function of lepton pT and η. To estimate the uncertainties
associated with the tag-and-probe technique, the total yield
is recomputed with the scaling factors varied up and down by
the tag-and-probe fit uncertainties. The uncertainties
associated with lepton efficiency in the ZZ → 4 (Z → 4 )
signal regions are found to be 6(10)% in the 4e, 3(6)% in the
2e2μ, and 2(7)% in the 4μ final states. These uncertainties are
higher for Z → 4 events because the leptons generally have
lower pT, and the samples used in the tag-and-probe method
have fewer events and more contamination from nonprompt
leptons in this low- pT region.
Uncertainties due to the effect of factorization (μF) and
renormalization (μR) scale choices on the ZZ → 4
acceptance are evaluated with powheg and mcfm by varying the
scales up and down by a factor of two with respect to the
default values μF = μR = mZZ. All combinations are
considered except those in which μF and μR differ by a factor
of four. Parametric uncertainties (PDF + αs ) are evaluated
according to the pdf4lhc prescription [
47
] in the acceptance
calculation, and with NNPDF3.0 in the cross section
calculations. An additional theoretical uncertainty arises from
scaling the powheg qq → ZZ simulated sample from its
NLO cross section to the NNLO prediction, and the mcfm
gg → ZZ samples from their LO cross sections to the NLO
predictions. The change in the acceptance corresponding to
this scaling procedure is found to be 1.1%. All these
theoretical uncertainties are added in quadrature.
The largest uncertainty in the estimated background yield
arises from differences in sample composition between the
Z + candidate control sample used to calculate the lepton
misidentification probability and the Z + + − control
sample. A further uncertainty arises from the limited number of
events in the Z + candidate sample. A systematic uncertainty
of 40% is applied to the lepton misidentification probability
to cover both effects. The size of this uncertainty varies by
channel, but is less than 1% of the total expected yield.
The uncertainty in the integrated luminosity of the data
sample is 2.5% [
48
].
8 Cross section measurements
The distributions of the four-lepton mass and the masses of
the Z1 and Z2 candidates are shown in Fig. 1. The expected
distributions describe the data well within uncertainties. The
SM predictions include nonresonant ZZ predictions,
production of the SM Higgs boson with mass 125 GeV [
49
], and
resonant Z → 4 production. The backgrounds estimated
from data and simulation are also shown. The reconstructed
invariant mass of the Z1 candidates, and a scatter plot
showing the correlation between mZ2 and mZ1 in data events, are
shown in Fig. 2. In the scatter plot, clusters of events
corresponding to ZZ → 4 , Zγ ∗ → 4 , and Z → 4 production
can be seen.
165
The four-lepton invariant mass distribution below 100 GeV
is shown in Fig. 3 (upper). Figure 3 (lower) shows mZ2 plotted
against mZ1 for events with m4 between 80 and 100 GeV, and
the observed and expected event yields in this mass region
are given in Table 2. The yield of events in the 4e final state
is significantly lower than in the 4μ final state because
minimum pT thresholds are higher for electrons than for muons,
and inefficiencies in the detection of low- pT leptons affect
electrons more strongly than they affect muons.
The reconstructed four-lepton invariant mass is shown in
Fig. 4 (upper) for events with two on-shell Z bosons. Figure 4
(lower) shows the invariant mass distribution for all Z boson
candidates in these events. The corresponding observed and
expected yields are given in Table 3.
The observed yields are used to evaluate the pp → Z →
4 and pp → ZZ → 4 production cross sections from a
combined fit to the number of observed events in all the final
states. The likelihood is a combination of individual
channel likelihoods for the signal and background hypotheses
with the statistical and systematic uncertainties in the form
of scaling nuisance parameters. The fiducial cross section is
measured by scaling the cross section in the simulation by
the ratio of the measured and predicted event yields given by
the fit.
The definitions for the fiducial phase spaces for the Z →
4 and ZZ → 4 cross section measurements are given
in Table 4. In the ZZ → 4 case, the Z bosons used in
the fiducial definition are built by pairing final-state leptons
using the same algorithm as is used to build Z boson
candidates from reconstructed leptons. The generator-level leptons
used for the fiducial cross section calculation are “dressed”
by adding the momenta of generator-level photons within
R ( , γ ) < 0.1 to their momenta.
The measured cross sections are
σfid(pp → Z → 4 )
= 31.2−+11..45 (stat)+−21..91 (syst) ± 0.8 (lumi) fb,
σfid(pp → ZZ → 4 )
= 40.9 ± 1.3 (stat) ± 1.4 (syst) ± 1.0 (lumi) fb.
The pp → Z → 4 fiducial cross section can be compared to
27.9+1.0
−1.5 ± 0.6 fb calculated at NLO in QCD with powheg
using the same settings as used for the simulated sample
described in Sect. 3, with dynamic scales μF = μR = m4 .
The uncertainties correspond to scale and PDF variations,
respectively. The ZZ fiducial cross section can be compared
to 34.4+0.7
−0.6 ± 0.5 fb calculated with powheg and mcfm using
the same settings as the simulated samples, or to 36.0+0.9
−0.8
computed with matrix at NNLO. The powheg and matrix
calculations used dynamic scales μF = μR = m4 , while the
contribution from mcfm was computed with dynamic scales
μF = μR = 0.5m4 .
The pp → Z → 4 fiducial cross section is scaled to
σ (pp → Z)B(Z → 4 ) using the acceptance correction
factor A = 0.125 ± 0.002, estimated with powheg. This factor
(2)
165
Fig. 4 Distributions of (upper) the four-lepton invariant mass mZZ and
(lower) dilepton candidate mass for four-lepton events selected with
both Z bosons on-shell. Points represent the data, while filled histograms
represent the SM prediction and background estimate. Vertical bars on
the data points show their statistical uncertainty. Shaded grey regions
around the predicted yield represent combined statistical, systematic,
theoretical, and integrated luminosity uncertainties. In the mZZ
distribution, bin contents are normalized to the bin widths, using a unit bin
size of 50 GeV; horizontal bars on the data points show the range of the
corresponding bin
corrects the fiducial Z → 4 cross section to the phase space
with only the 80–100 GeV mass window and m + − > 4 GeV
requirements, and also includes a correction, 0.96 ± 0.01, for
the contribution of nonresonant four-lepton production to the
signal region. The uncertainty takes into account the
interference between doubly- and singly-resonant diagrams. The
measured cross section is
σ (pp → Z)B(Z → 4 )
= 249 ± 11(st at )+−1165(s yst ) ± 4(t heo) ± 6(lumi ) f b (3)
The branching fraction for the Z → 4 decay, B(Z → 4 ),
is measured by comparing the cross section given by Eq. (3)
with the Z → + − cross section, and is computed as
B(Z → 4 ) =
σ (pp → Z → 4 )
C8600––110200 σ (pp → Z →
+ −)/B(Z →
+ −)
where σ (pp → Z → + −) = 1870−+4500 pb is the Z →
+ − cross section times branching fraction calculated at
NNLO with fewz v2.0 [
50
] in the mass range 60–120 GeV.
Its uncertainty includes PDF uncertainties and
uncertainties in αs , the charm and bottom quark masses, and the
effect of neglected higher-order corrections to the
calcula60–120
tion. The factor C80–100 = 0.926 ± 0.001 corrects for the
difference in Z boson mass windows and is estimated using
powheg. Its uncertainty includes scale and PDF variations.
The nominal Z to dilepton branching fraction B(Z → + −)
is 0.03366 [
46
]. The measured value is
B(Z → 4 ) = 4.83+−00..2232(st at )+−00..3229(s yst ) ± 0.08(t heo)
±0.12(lumi ) × 10−6
where the theoretical uncertainty includes the
uncertainties in σ (pp → Z)B(Z → + −), C8600––110200, and A. This
can be compared with 4.6 × 10−6, computed with
MadGraph5_amc@nlo, and is consistent with the CMS and
ATLAS measurements at √s = 7, 8, and 13 TeV [
6, 14, 15
].
,
(4)
(5)
The total ZZ production cross section for both dilep
tons produced in the mass range 60–120 GeV and m + − >
4 GeV is found to be
σ (pp → ZZ) = 17.5+−00..65 (stat) ± 0.6 (syst) ± 0.4 (theo)
± 0.4 (lumi) pb.
The measured total cross section can be compared to the
theoretical value of 14.5+0.5
−0.4 ± 0.2 pb calculated with a
combination of powheg and mcfm with the same settings
as described for σfid(pp → ZZ → 4 ). It can also be
compared to 16.2−+00..46 pb, calculated at NNLO in QCD via
matrix v1.0.0_beta4 [
11, 51
], or 15.0+0.7
−0.6 ± 0.2 pb,
calculated with mcfm at NLO in QCD with additional
contributions from LO gg → ZZ diagrams. Both values are
calculated with the NNPDF3.0 PDF sets, at NNLO and NLO,
respectively, and fixed scales set to μF = μR = mZ.
This measurement agrees with the previously published
cross section measured by CMS at 13 TeV [
6
] based on a
2.6 fb−1 data sample collected in 2015:
σ (pp → ZZ) = 14.6−+11..89 (stat)+−00..35 (syst) ± 0.2 (theo)
± 0.4 (lumi) pb.
(6)
(7)
165
pythia v8 was used for parton showering, hadronization, and
underlying event simulation in the powheg, MadGraph5_amc@nlo, and
mcfm samples. The lower part of each plot represents the ratio of the
measured cross section to the theoretical distributions. The shaded grey
areas around the points represent the sum in quadrature of the statistical
and systematic uncertainties, while the crosses represent the statistical
uncertainties only
The two measurements can be combined to yield the “2015 + 2016 cross section”
σ (pp → ZZ) = 17.2 ± 0.5 (stat) ± 0.7 (syst) ± 0.4 (theo)
± 0.4 (lumi) pb. (8)
The combination was performed once considering the
experimental uncertainties to be fully correlated between the 2015
and 2016 data sets, and once considering them to be fully
uncorrelated. The results were averaged, and the difference
was added linearly to the systematic uncertainty in the
combined cross section.
The total ZZ cross section is shown in Fig. 5 as a
function of the proton-proton center-of-mass energy. Results from
CMS [
3, 4
] and ATLAS [
7, 8, 10
] are compared to predictions
from matrix and mcfm with the NNPDF3.0 PDF sets and
fixed scales μF = μR = mZ. The matrix prediction uses
PDFs calculated at NNLO, while the mcfm prediction uses
NLO PDFs. The uncertainties are statistical (inner bars) and
statistical and systematic added in quadrature (outer bars).
The band around the matrix predictions reflects scale
uncertainties, while the band around the mcfm predictions reflects
both scale and PDF uncertainties.
The measurement of the differential cross sections
provides detailed information about ZZ kinematics. The
observed yields are unfolded using the iterative technique described
in Ref. [
52
]. Unfolding is performed with the RooUnfold
package [
53
] and regularized by stopping after four
iterations. Statistical uncertainties in the data distributions are
propagated through the unfolding process to give the
statistical uncertainties on the normalized differential cross
sections.
The three decay channels, 4e, 4μ, and 2e2μ, are combined
after unfolding because no differences are expected in their
kinematic distributions. The generator-level leptons used for
the unfolding are dressed as in the fiducial cross section
calculation.
Fig. 7 Normalized ZZ differential cross sections as a function of the
pT of (upper) all Z bosons and (lower) the leading lepton in ZZ events.
Other details are as described in the caption of Fig. 6
The differential distributions normalized to the fiducial
cross sections are presented in Figs. 6, 7, 8 for the
combination of the 4e, 4μ, and 2e2μ decay channels. The
fiducial cross section definition includes pT and |η | selections
on each lepton, and the 60–120 GeV mass requirement, as
described in Table 4 and Sect. 4. Figure 6 shows the
normalized differential cross sections as functions of the mass
and pT of the ZZ system, Fig. 7 shows them as functions
of the pT of all Z bosons and the pT of the leading
lepton in each event, and Fig. 8 shows the angular correlations
between the two Z bosons. The data are corrected for
background contributions and compared with the theoretical
predictions from powheg and mcfm, MadGraph5_amc@nlo
and mcfm, and matrix. The bottom part of each plot shows
the ratio of the measured to the predicted values. The bin
sizes are chosen according to the resolution of the relevant
variables, while also keeping the statistical uncertainties at a
similar level in all bins. The data are well reproduced by the
simulation except in the low pT regions, where data tend to
have a steeper slope than the prediction.
Figure 9 shows the normalized differential four-lepton
cross section as a function of m4 , subject only to the
common requirements of Table 4. This includes contributions
from the Z and Higgs boson resonances and continuum ZZ
production.
9 Limits on anomalous triple gauge couplings
The presence of aTGCs would increase the yield of events at
high four-lepton masses. Figure 10 presents the distribution
of the four-lepton reconstructed mass of events with both
Z bosons in the mass range 60–120 GeV for the combined
4e, 4μ, and 2e2μ channels. This distribution is used to set
the limits on possible contributions from aTGCs. Two
simulated samples with nonzero aTGCs are shown as examples,
along with the SM distribution simulated by both sherpa
and powheg.
Fig. 9 The normalized differential four-lepton cross section as a
function of the four-lepton mass, subject only to the common requirements
of Table 4. SM gg → H → ZZ∗ production is included, simulated with
powheg. Other details are as described in the caption of Fig. 6
The invariant mass distributions are interpolated from the
sherpa simulations for different values of the anomalous
couplings in the range between 0 and 0.015. For each
distribution, only one or two couplings are varied while all
others are set to zero. The measured signal is obtained from
a comparison of the data to a grid of aTGC models in the
γ γ
( f4Z, f4 ) and ( f5Z, f5 ) parameter planes. Expected signal
values are interpolated between the 2D grid points using a
second-degree polynomial, since the cross section for the
signal depends quadratically on the coupling parameters. A
binned profile likelihood method, Wald Gaussian
approximation, and Wilk’s theorem are used to derive one-dimensional
limits at a 95% confidence level (CL) on each of the four
aTGC parameters, and two-dimensional limits at a 95% CL
on the pairs ( f4Z, f4γ ) and ( f5Z, f5γ ) [
46,54,55
]. When the
limits are calculated for each parameter or pair, all other
parameters are set to their SM values. The systematic uncertainties
described in Sect. 7 are treated as nuisance parameters with
log-normal distributions. No form factor is used when
deriving the limits so that the results do not depend on any assumed
energy scale characterizing new physics. The constraints on
anomalous couplings are displayed in Fig. 11. The curves
indicate 68 and 95% confidence levels, and the solid dot
shows the coordinates where the likelihood reaches its
maximum. Coupling values outside the contours are excluded at
and f5Z,γ anomalous coupling parameters are:
the corresponding confidence levels. The limits are
dominated by statistical uncertainties.
The observed one-dimensional 95% CL limits for the f4Z,γ
− 0.0012 < f4Z < 0.0010,
− 0.0012 < f4γ < 0.0013,
− 0.0010 < f5Z < 0.0013,
− 0.0012 < f5γ < 0.0013.
These are the most stringent limits to date on anomalous ZZZ
and ZZγ trilinear gauge boson couplings, improving on the
previous strictest results from CMS [
5
] by factors of two or
more and constraining the coupling parameters more than
the corresponding ATLAS results [
10
].
One way to impose unitarity on the aTGC models is to
restrict the range of four-lepton invariant mass used in the
limit calculation. The limits will then depend on the “cutoff”
value used. The computation of the one-dimensional limits
is repeated for different maximum allowed values of m4 ,
and the results are presented in Fig. 12 as a function of this
cutoff.
Fig. 11 Two-dimensional observed 95% CL limits (solid contour) and
expected 68 and 95% CL limits (dashed contour) on the ZZZ and
ZZγ aTGCs. The upper(lower) plot shows the exclusion contour in
the f4Z(5), f4γ(5) parameter planes. The values of couplings outside of
contours are excluded at the corresponding confidence level. The solid
dot is the point at which the likelihood is at its maximum. The solid
lines at the center show the observed one-dimensional 95% CL limits
for f4γ,5 (horizontal) and f4Z,5 (vertical). No form factor is used
10 Summary
A series of measurements of four-lepton final states in
protonproton collisions at √s = 13 TeV have been performed
with the CMS detector at the CERN LHC. The measured
pp → ZZ cross section is σ (pp → ZZ) = 17.2 ± 0.5 (stat)±
0.7 (syst) ± 0.4 (theo) ± 0.4 (lumi) pb for Z boson masses in
the range 60 < mZ < 120 GeV. The measured branching
fraction for Z boson decays to four leptons is B(Z → 4 ) =
4.83+−00..2232(st at )+−00..3229(s yst ) ± 0.08(t heo) ± 0.12(lumi ) ×
10−6 for four-lepton mass in the range 80 < m4 < 100 GeV
and dilepton mass m > 4 GeV for all oppositely charged
same-flavor lepton pairs. Normalized differential cross
sections were also measured. All results agree well with the SM
predictions. Improved limits on anomalous ZZZ and ZZγ
triple gauge couplings were established, the most stringent
to date.
Acknowledgements We congratulate our colleagues in the CERN
accelerator departments for the excellent performance of the LHC and
thank the technical and administrative staffs at CERN and at other CMS
institutes for their contributions to the success of the CMS effort. In
addition, we gratefully acknowledge the computing centers and
personnel of the Worldwide LHC Computing Grid for delivering so
effectively 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
(USA). Individuals have received support from the Marie-Curie
program 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 Office; the Fonds pour la
Formation à la Recherche dans l’Industrie et dans l’Agriculture
(FRIABelgium); 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 program of the
Foundation for Polish Science, cofinanced from European Union, Regional
Development Fund, the Mobility Plus program 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 programs cofinanced 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 (USA).
Open Access This article is distributed under the terms of the Creative
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ons.org/licenses/by/4.0/), which permits unrestricted use, distribution,
and reproduction in any medium, provided you give appropriate credit
to the original author(s) and the source, provide a link to the Creative
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Funded by SCOAP3.
CMS Collaboration
Yerevan Physics Institute, Yerevan, Armenia
A. M. Sirunyan, A. Tumasyan
Institut für Hochenergiephysik, Vienna, Austria
W. Adam, F Ambrogi, E. Asilar, T. Bergauer, J. Brandstetter, E. Brondolin, M. Dragicevic, J. Erö, M. Flechl, M. Friedl,
R. Frühwirth1, V. M. Ghete, J. Grossmann, J. Hrubec, M. Jeitler1, A. König, N. Krammer, I. Krätschmer, D. Liko,
T. Madlener, I. Mikulec, E. Pree, D. Rabady, N. Rad, H. Rohringer, J. Schieck1, R. Schöfbeck, M. Spanring, D. Spitzbart,
W. Waltenberger, J. Wittmann, C.-E. Wulz1, M. Zarucki
Institute for Nuclear Problems, Minsk, Belarus
V. Chekhovsky, V. Mossolov, J. Suarez Gonzalez
Vrije Universiteit Brussel, Brussel, Belgium
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
Université de Mons, Mons, Belgium
N. Beliy
Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
E. Belchior Batista Das Chagas, W. Carvalho, J. Chinellato3, A. Custódio, E. M. Da Costa, G. G. Da Silveira4,
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 Manganote3,
F. Torres Da Silva De Araujo, A. Vilela Pereira
Universidade Estadual Paulistaa , Universidade Federal do ABCb, São Paulo, Brazil
S. Ahujaa , C. A. Bernardesa , T. R. Fernandez Perez Tomeia , E. M. Gregoresb, P. G. Mercadanteb, S. F. Novaesa ,
Sandra S. Padulaa , D. Romero Abadb, J. C. Ruiz Vargasa
Institute for Nuclear Research and Nuclear Energy, Bulgaria Academy of Sciences, Sofia, Bulgaria
A. Aleksandrov, R. Hadjiiska, P. Iaydjiev, M. Misheva, M. Rodozov, M. Shopova, S. Stoykova, G. Sultanov
University of Sofia, Sofia, Bulgaria
A. Dimitrov, I. Glushkov, L. Litov, B. Pavlov, P. Petkov
Beihang University, Beijing, China
W. Fang5, X. Gao5
State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
Y. Ban, G. Chen, Q. Li, S. Liu, Y. Mao, S. J. Qian, D. Wang, Z. Xu
University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Split, Croatia
B. Courbon, N. Godinovic, D. Lelas, I. Puljak, P. M. Ribeiro Cipriano, T. Sculac
Institute Rudjer Boskovic, Zagreb, Croatia
V. Brigljevic, D. Ferencek, K. Kadija, B. Mesic, A. Starodumov6, T. Susa
University of Cyprus, Nicosia, Cyprus
M. W. Ather, A. Attikis, G. Mavromanolakis, J. Mousa, C. Nicolaou, F. Ptochos, P. A. Razis, H. Rykaczewski
Charles University, Prague, Czech Republic
M. Finger7, M. Finger Jr.7
Universidad San Francisco de Quito, Quito, Ecuador
E. Carrera Jarrin
Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy
Physics, Cairo, Egypt
Y. Assran8,9, M. A. Mahmoud9,10, A. Mahrous11
National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
R. K. Dewanjee, M. Kadastik, L. Perrini, M. Raidal, A. Tiko, C. Veelken
Department of Physics, University of Helsinki, Helsinki, Finland
P. Eerola, J. Pekkanen, M. Voutilainen
Lappeenranta University of Technology, Lappeenranta, Finland
J. Talvitie, T. Tuuva
Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS/IN2P3, Université Paris-Saclay, Palaiseau, France
A. Abdulsalam, 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, S. Regnard,
R. Salerno, J. B. Sauvan, Y. Sirois, A. G. Stahl Leiton, T. Strebler, Y. Yilmaz, A. Zabi, A. Zghiche
Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000, Strasbourg, France
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. Gelé, U. Goerlach, M. Jansová, A.-C. Le Bihan, N. Tonon, P. Van Hove
Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3,
Villeurbanne, France
S. Gadrat
Georgian Technical University, Tbilisi, Georgia
A. Khvedelidze7
Tbilisi State University, Tbilisi, Georgia
Z. Tsamalaidze7
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, E. Dietz-Laursonn, D. Duchardt, M. Endres, M. Erdmann, S. Erdweg, T. Esch, R. Fischer, A. Güth, 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. Thüer
Deutsches Elektronen-Synchrotron, Hamburg, Germany
M. Aldaya Martin, T. Arndt, C. Asawatangtrakuldee, K. Beernaert, O. Behnke, U. Behrens, A. Bermúdez Martínez,
A. A. Bin Anuar, K. Borras15, V. Botta, A. Campbell, P. Connor, C. Contreras-Campana, F. Costanza, C. Diez Pardos,
G. Eckerlin, D. Eckstein, T. Eichhorn, E. Eren, E. Gallo16, J. Garay Garcia, A. Geiser, A. Gizhko, J. M. Grados Luyando,
A. Grohsjean, P. Gunnellini, M. Guthoff, A. Harb, J. Hauk, M. Hempel17, H. Jung, A. Kalogeropoulos, M. Kasemann,
J. Keaveney, C. Kleinwort, I. Korol, D. Krücker, W. Lange, A. Lelek, T. Lenz, J. Leonard, K. Lipka, W. Lohmann17,
R. Mankel, I.-A. Melzer-Pellmann, A. B. Meyer, G. Mittag, J. Mnich, A. Mussgiller, E. Ntomari, D. Pitzl, 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
Institut für 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. Giffels, A. Gilbert, D. Haitz, F. Hartmann14, S. M. Heindl, U. Husemann, F. Kassel14, S. Kudella,
H. Mildner, M. U. Mozer, Th. Müller, M. Plagge, G. Quast, K. Rabbertz, M. Schröder, I. Shvetsov, G. Sieber,
H. J. Simonis, R. Ulrich, S. Wayand, M. Weber, T. Weiler, S. Williamson, C. Wöhrmann, R. Wolf
Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece
G. Anagnostou, G. Daskalakis, T. Geralis, V. A. Giakoumopoulou, A. Kyriakis, D. Loukas, I. Topsis-Giotis
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
MTA-ELTE Lendület CMS Particle and Nuclear Physics Group, Eötvös Loránd University, Budapest, Hungary
M. Csanad, N. Filipovic, G. Pasztor, G. I. Veres18
Institute of Nuclear Research ATOMKI, Debrecen, Hungary
N. Beni, S. Czellar, J. Karancsi20, A. Makovec, J. Molnar, Z. Szillasi
Institute of Physics, University of Debrecen, Debrecen, Hungary
M. Bartók18, P. Raics, Z. L. Trocsanyi, B. Ujvari
Indian Institute of Science (IISc), Bangalore, India
S. Choudhury, J. R. Komaragiri
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
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. Mohanty14, 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
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. Chenarani25, E. Eskandari Tadavani, S. M. Etesami25, M. Khakzad, M. Mohammadi Najafabadi, M. Naseri,
S. Paktinat Mehdiabadi26, F. Rezaei Hosseinabadi, B. Safarzadeh27, M. Zeinali
University College Dublin, Dublin, Ireland
M. Felcini, M. Grunewald
INFN Sezione di Baria , Università di Barib, Politecnico di Baric, 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 ,b, A. Ranieria , G. Selvaggia ,b, A. Sharmaa , L. Silvestrisa ,14, R. Vendittia , P. Verwilligena
INFN Sezione di Bolognaa , Università di Bolognab, 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. Cuffiania ,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 Cataniaa , Università di Cataniab, 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 Firenzea , Università di Firenzeb, 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 ,28, G. Sguazzonia , D. Stroma , L. Viliania ,b,14
INFN Laboratori Nazionali di Frascati, Frascati, Italy
L. Benussi, S. Bianco, F. Fabbri, D. Piccolo, F. Primavera14
INFN Sezione di Genovaa , Università di Genovab, Genova, Italy
V. Calvellia ,b, F. Ferroa , E. Robuttia , S. Tosia ,b
INFN Sezione di Milano-Bicoccaa , Università di Milano-Bicoccab, 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, D. Pedrinia ,
S. Pigazzinia ,b,29, S. Ragazzia ,b, T. Tabarelli de Fatisa ,b
INFN Sezione di Napolia , Università di Napoli ’Federico II’ b, Napoli, Italy, Università della Basilicatac, Potenza,
Italy, Università G. Marconid , Roma, Italy
S. Buontempoa , N. Cavalloa ,c, S. Di Guidaa ,d ,14, F. Fabozzia ,c, F. Fiengaa ,b, A. O. M. Iorioa ,b, W. A. Khana , L. Listaa ,
S. Meolaa ,d ,14, P. Paoluccia ,14, C. Sciaccaa ,b, F. Thyssena
INFN Sezione di Padovaa , Università di Padovab, Padova, Italy, Università di Trentoc, Trento, Italy
P. Azzia ,14, N. Bacchettaa , L. Benatoa ,b, D. Biselloa ,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 , P. Lujan, M. Margonia ,b, A. T. Meneguzzoa ,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 Paviaa , Università di Paviab, Pavia, Italy
A. Braghieria , 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 Perugiaa , Università di Perugiab, Perugia, Italy
L. Alunni Solestizia ,b, M. Biasinia ,b, G. M. Bileia , C. Cecchia ,b, D. Ciangottinia ,b, L. Fanòa ,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 Pisaa , Università di Pisab, Scuola Normale Superiore di Pisac, Pisa, Italy
K. Androsova , P. Azzurria ,14, 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 ,28, 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 ,30, P. Spagnoloa , R. Tenchinia ,
G. Tonellia ,b, A. Venturia , P. G. Verdinia
INFN Sezione di Romaa , Università di Romab, Roma, Italy
L. Baronea ,b, F. Cavallaria , M. Cipriania ,b, N. Dacia , D. Del Rea ,b,14, E. Di Marcoa ,b, M. Diemoza , S. Gellia ,b,
E. Longoa ,b, F. Margarolia ,b, B. Marzocchia ,b, P. Meridiania , G. Organtinia ,b, R. Paramattia ,b, F. Preiatoa ,b,
S. Rahatloua ,b, C. Rovellia , F. Santanastasioa ,b
INFN Sezione di Torinoa , Università di Torinob, Turin, Italy, Università del Piemonte Orientalec, 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 Triestea , Università di Triesteb, 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
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
National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia
I. Ahmed, Z. A. Ibrahim, M. A. B. Md Ali31, F. Mohamad Idris32, W. A. T. Wan Abdullah, M. N. Yusli, Z. Zolkapli
Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico
R. Reyes-Almanza, G. Ramirez-Sanchez, M. C. Duran-Osuna, H. Castilla-Valdez, E. De La Cruz-Burelo,
I. Heredia-De La Cruz33, R. I. Rabadan-Trejo, 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 Autónoma de San Luis Potosí, San Luis Potosi, Mexico
A. Morelos Pineda
University of Auckland, Auckland, New Zealand
D. Krofcheck
University of Canterbury, Christchurch, New Zealand
P. H. Butler
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, M. Waqas
National Centre for Nuclear Research, Swierk, Poland
H. Bialkowska, M. Bluj, B. Boimska, T. Frueboes, M. Górski, M. Kazana, K. Nawrocki, M. Szleper, P. Zalewski
Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, Portugal
P. Bargassa, C. Beirão 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
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. Bylinkin36
National Research Nuclear University ‘Moscow Engineering Physics Institute’ (MEPhI), Moscow, Russia
M. Chadeeva39, P. Parygin, D. Philippov, S. Polikarpov, E. Popova, V. Rusinov
P.N. Lebedev Physical Institute, Moscow, Russia
V. Andreev, M. Azarkin36, I. Dremin36, M. Kirakosyan37, A. Terkulov
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia
A. Baskakov, A. Belyaev, E. Boos, M. Dubinin40, L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova,
I. Lokhtin, I. Miagkov, S. Obraztsov, S. Petrushanko, V. Savrin, A. Snigirev
Novosibirsk State University (NSU), Novosibirsk, Russia
V. Blinov41, Y. Skovpen41, D. Shtol41
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. Adzic42, P. Cirkovic, D. Devetak, M. Dordevic, J. Milosevic, V. Rekovic
Universidad Autónoma de Madrid, Madrid, Spain
C. Albajar, J. F. de Trocóniz, M. Missiroli, D. Moran
Instituto de Física 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
ETH Zurich - Institute for Particle Physics and Astrophysics (IPA), Zurich, Switzerland
F. Bachmair, L. Bäni, P. Berger, L. Bianchini, B. Casal, G. Dissertori, M. Dittmar, M. Donegà, 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. Pandolfi, J. Pata, F. Pauss, G. Perrin, L. Perrozzi, M. Quittnat, M. Reichmann,
M. Schönenberger, L. Shchutska, V. R. Tavolaro, K. Theofilatos, M. L. Vesterbacka Olsson, R. Wallny, D. H. Zhu
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
Chulalongkorn University, Faculty of Science, Department of Physics, Bangkok, Thailand
B. Asavapibhop, K. Kovitanggoon, G. Singh, N. Srimanobhas
Çukurova University, Physics Department, Science and Art Faculty, Adana, Turkey
F. Boran, S. Cerci49, S. Damarseckin, Z. S. Demiroglu, C. Dozen, I. Dumanoglu, S. Girgis, G. Gokbulut, Y. Guler,
I. Hos50, E. E. Kangal51, O. Kara, A. Kayis Topaksu, U. Kiminsu, M. Oglakci, G. Onengut52, K. Ozdemir53,
D. Sunar Cerci49, B. Tali49, S. Turkcapar, I. S. Zorbakir, C. Zorbilmez
Middle East Technical University, Physics Department, Ankara, Turkey
B. Bilin, G. Karapinar54, K. Ocalan55, M. Yalvac, M. Zeyrek
Bogazici University, Istanbul, Turkey
E. Gülmez, M. Kaya56, O. Kaya57, S. Tekten, E. A. Yetkin58
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
National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine
L. Levchuk, P. Sorokin
University of Bristol, Bristol, UK
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. Newbold59, S. Paramesvaran, A. Poll,
T. Sakuma, S. Seif El Nasr-storey, D. Smith, V. J. Smith
Rutherford Appleton Laboratory, Didcot, UK
K. W. Bell, A. Belyaev60, 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
Brunel University, Uxbridge, UK
J. E. Cole, P. R. Hobson, A. Khan, P. Kyberd, I. D. Reid, P. Symonds, L. Teodorescu, M. Turner
Baylor University, Waco, USA
A. Borzou, K. Call, J. Dittmann, K. Hatakeyama, H. Liu, N. Pastika, C. Smith
Catholic University of America, Washington, DC, USA
R. Bartek, A. Dominguez
The University of Alabama, Tuscaloosa, USA
A. Buccilli, S. I. Cooper, C. Henderson, P. Rumerio, C. West
Boston University, Boston, USA
D. Arcaro, A. Avetisyan, T. Bose, D. Gastler, D. Rankin, C. Richardson, J. Rohlf, L. Sulak, D. Zou
University of California, Davis, Davis, USA
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, Riverside, Riverside, USA
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, L. Wang, H. Wei, S. Wimpenny, B. R. Yates
University of California, Santa Barbara-Department of Physics, Santa Barbara, USA
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
Carnegie Mellon University, Pittsburgh, USA
M. B. Andrews, T. Ferguson, T. Mudholkar, M. Paulini, J. Russ, M. Sun, H. Vogel, I. Vorobiev, M. Weinberg
University of Colorado Boulder, Boulder, USA
J. P. Cumalat, W. T. Ford, F. Jensen, A. Johnson, M. Krohn, S. Leontsinis, T. Mulholland, K. Stenson, S. R. Wagner
Cornell University, Ithaca, USA
J. Alexander, J. Chaves, J. Chu, S. Dittmer, K. Mcdermott, N. Mirman, J. R. Patterson, A. Rinkevicius, A. Ryd,
L. Skinnari, L. Soffi, S. M. Tan, Z. Tao, J. Thom, J. Tucker, P. Wittich, M. Zientek
Florida International University, Miami, USA
Y. R. Joshi, S. Linn, P. Markowitz, J. L. Rodriguez
Florida Institute of Technology, Melbourne, USA
M. M. Baarmand, V. Bhopatkar, S. Colafranceschi, M. Hohlmann, D. Noonan, T. Roy, F. Yumiceva
University of Illinois at Chicago (UIC), Chicago, USA
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
Kansas State University, Manhattan, USA
A. Ivanov, K. Kaadze, Y. Maravin, A. Mohammadi, L. K. Saini, N. Skhirtladze, S. Toda
Lawrence Livermore National Laboratory, Livermore, USA
F. Rebassoo, D. Wright
University of Maryland, College Park, USA
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, USA
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 Mississippi, Oxford, USA
J. G. Acosta, S. Oliveros
State University of New York at Buffalo, Buffalo, USA
M. Alyari, J. Dolen, A. Godshalk, C. Harrington, I. Iashvili, D. Nguyen, A. Parker, S. Rappoccio, B. Roozbahani
Northwestern University, Evanston, USA
S. Bhattacharya, O. Charaf, K. A. Hahn, N. Mucia, N. Odell, B. Pollack, M. H. Schmitt, K. Sung, M. Trovato, M. Velasco
The Ohio State University, Columbus, USA
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
University of Puerto Rico, Mayaguez, USA
S. Malik, S. Norberg
Purdue University Northwest, Hammond, USA
T. Cheng, N. Parashar, J. Stupak
University of Rochester, Rochester, USA
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, USA
R. Ciesielski, K. Goulianos, C. Mesropian
Rutgers, The State University of New Jersey, Piscataway, USA
A. Agapitos, J. P. Chou, Y. Gershtein, T. A. Gómez 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. Sheffield, S. Somalwar, R. Stone, S. Thomas, P. Thomassen, M. Walker
University of Tennessee, Knoxville, USA
A. G. Delannoy, M. Foerster, J. Heideman, G. Riley, K. Rose, S. Spanier, K. Thapa
Texas Tech University, Lubbock, USA
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, USA
S. Greene, A. Gurrola, R. Janjam, W. Johns, C. Maguire, A. Melo, H. Ni, P. Sheldon, S. Tuo, J. Velkovska, Q. Xu
Wayne State University, Detroit, USA
R. Harr, P. E. Karchin, J. Sturdy, S. Zaleski
† Deceased
1: Also at Vienna University of Technology, Vienna, Austria
2: Also at State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China
3: Also at Universidade Estadual de Campinas, Campinas, Brazil
4: Also at Universidade Federal de Pelotas, Pelotas, Brazil
5: Also at Université 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 Université de Haute Alsace, Mulhouse, France
13: Also at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia
14: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland
15: Also at RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany
Page 28 of 29
16: Also at University of Hamburg, Hamburg, Germany
17: Also at Brandenburg University of Technology, Cottbus, Germany
18: Also at MTA-ELTE Lendület CMS Particle and Nuclear Physics Group, Eötvös Loránd University, Budapest, Hungary
19: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary
20: Also at Institute of Physics, University of Debrecen, Debrecen, Hungary
21: Also at Indian Institute of Technology Bhubaneswar, Bhubaneswar, India
22: Also at Institute of Physics, Bhubaneswar, India
23: Also at University of Visva-Bharati, Santiniketan, India
24: Also at University of Ruhuna, Matara, Sri Lanka
25: Also at Isfahan University of Technology, Isfahan, Iran
26: Also at Yazd University, Yazd, Iran
27: Also at Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran
28: Also at Università degli Studi di Siena, Siena, Italy
29: Also at INFN Sezione di Milano-Bicocca; Università di Milano-Bicocca, Milano, Italy
30: Also at Purdue University, West Lafayette, USA
31: Also at International Islamic University of Malaysia, Kuala Lumpur, Malaysia
32: Also at Malaysian Nuclear Agency, MOSTI, Kajang, Malaysia
33: Also at Consejo Nacional de Ciencia y Tecnología, Mexico city, Mexico
34: Also at Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
35: Also at Institute for Nuclear Research, Moscow, Russia
36: Now at National Research Nuclear University ’Moscow Engineering Physics Institute’ (MEPhI), Moscow, Russia
37: Also at St. Petersburg State Polytechnical University, St. Petersburg, Russia
38: Also at University of Florida, Gainesville, USA
39: Also at P.N. Lebedev Physical Institute, Moscow, Russia
40: Also at California Institute of Technology, Pasadena, USA
41: Also at Budker Institute of Nuclear Physics, Novosibirsk, Russia
42: Also at Faculty of Physics, University of Belgrade, Belgrade, Serbia
43: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia
44: Also at Scuola Normale e Sezione dell’INFN, Pisa, Italy
45: Also at National and Kapodistrian University of Athens, Athens, Greece
46: Also at Riga Technical University, Riga, Latvia
47: Also at Universität Zürich, Zurich, Switzerland
48: Also at Stefan Meyer Institute for Subatomic Physics, (SMI), Vienna, Austria
49: Also at Adiyaman University, Adiyaman, Turkey
50: Also at Istanbul Aydin University, Istanbul, Turkey
51: Also at Mersin University, Mersin, Turkey
52: Also at Cag University, Mersin, Turkey
53: Also at Piri Reis University, Istanbul, Turkey
54: Also at Izmir Institute of Technology, Izmir, Turkey
55: Also at Necmettin Erbakan University, Konya, Turkey
56: Also at Marmara University, Istanbul, Turkey
57: Also at Kafkas University, Kars, Turkey
58: Also at Istanbul Bilgi University, Istanbul, Turkey
59: Also at Rutherford Appleton Laboratory, Didcot, UK
60: Also at School of Physics and Astronomy, University of Southampton, Southampton, UK
61: Also at Instituto de Astrofísica de Canarias, La Laguna, Spain
62: Also at Utah Valley University, Orem, USA
63: Also at USABeykent University, Istanbul, Turkey
64: Also at Bingol University, Bingol, Turkey
65: Also at Erzincan University, Erzincan, Turkey
66: Also at Sinop University, Sinop, Turkey
67: Also at Mimar Sinan University, Istanbul, Istanbul, Turkey
68: Also at Texas A&M University at Qatar, Doha, Qatar
69: Also at Kyungpook National University, Taegu, Korea
1. G.J. Gounaris , J. Layssac , F.M. Renard , New and standard physics contributions to anomalous Z and γ self-couplings . Phys. Rev. D 62 , 073013 ( 2000 ). https://doi.org/10.1103/PhysRevD.62.073013. arXiv: hep-ph/0003143
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