Measurements of Four-Lepton Production at the Z Resonance in pp Collisions at $\sqrt s=$7 and 8 TeV with ATLAS

EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)

CERN-PH-EP-2014-047

Submitted to: Phys. Rev. Lett.

Measurement of the 4

`

Cross Section at the

Z

Resonance and

Determination of the Branching Fraction of

Z → 4`

in

pp

Collisions at

√

s

= 7 and 8

TeV

with ATLAS

The ATLAS Collaboration

Abstract

Measurements of four-lepton (4`, ` = e, µ) production cross sections at the Z resonance in pp

collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant

mass region

m

`+<sub>`</sub>−

> 5 GeV and 80 < m

_4`

< 100 GeV, the measured cross sections are 76±18 (stat) ±

4 (syst) ±1.4 (lumi) fb and 107±9 (stat) ±4 (syst) ±3.0 (lumi) fb at

√

s = 7 and 8 TeV, respectively. By

subtracting the non-resonant 4` production contributions and normalizing with Z → µ

+

_µ

−

_{events, the}

branching fraction for the

Z boson decay to 4` is determined to be (3.20 ± 0.25 (stat) ± 0.13 (syst)) ×

10

−6

_{, consistent with the Standard Model prediction.}

c

2014 CERN for the benefit of the ATLAS Collaboration.

Reproduction of this article or parts of it is allowed as specified in the CC-BY-3.0 license.

Measurement of the 4` Cross Section at the Z Resonance and Determination of the

Branching Fraction of Z → 4` in pp Collisions at

√

s = 7 and 8 TeV with ATLAS

G. Aad et al. (ATLAS Collaboration)

Measurements of four-lepton (4`, ` = e, µ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass region m`+<sub>`</sub>− > 5 GeV and 80 < m4` < 100 GeV, the measured cross sections are 76 ±

18 (stat) ± 4 (syst) ± 1.4 (lumi) fb and 107 ± 9 (stat) ± 4 (syst) ± 3.0 (lumi) fb at√s = 7 and 8 TeV, respectively. By subtracting the non-resonant 4` production contributions and normalizing with Z → µ+µ− events, the branching fraction for the Z boson decay to 4` is determined to be (3.20 ± 0.25 (stat) ± 0.13 (syst)) × 10−6, consistent with the Standard Model prediction.

PACS numbers: 13.38.Dg

This Letter presents measurements of the cross sec-tions for the inclusive production of four leptons (4`, ` = e, µ) at the Z resonance in proton–proton

colli-sions at √s = 7 and 8 TeV using data recorded by the

ATLAS detector [1] at the LHC [2] in 2011 and 2012. In

the Standard Model (SM), 4` production in the Z reso-nance region occurs dominantly via an s-channel diagram

such as shown in Fig. 1(a) where the Z boson decay to

charged leptons includes the production of an additional lepton pair from the internal conversion of a virtual Z or γ. A small fraction of 4` events is also produced in a

t-channel process such as shown in Fig.1(b). The process

gg → Z(∗)_Z(∗)_{→ 4` accounts for only about 10}−3 _{of the}

total 4` event rate around the Z resonance [3]. A

reso-Z/γ∗ Z∗_/γ∗ ¯ q q ℓ+ ℓ+ ℓ− ℓ− _Z∗_/γ∗ Z∗_/γ∗ ¯ q q ℓ+ ℓ− ℓ+ ℓ− (a) (b)

FIG. 1. Examples of (a) s-channel and (b) t-channel Feyn-man diagrams for 4` production in pp collisions.

nant peak around the Z mass in the 4` invariant mass spectrum is observed along with the nearby peak from

the Higgs boson decay H → 4` [4,5]. A measurement of

the 4` production cross section at the Z resonance pro-vides a test of the SM and a cross-check of the detector response to the 4` final state from Higgs decays.

Since the interference between the resonant and non-resonant (t-channel and gg) production mechanisms is expected to be very small around the Z resonance, the branching fraction of the rare decay Z → 4` can be de-termined by subtracting the expected non-resonant 4` contributions from the measured 4` rate. For

simplic-ity, inclusive 4` production around the Z resonance, in-cluding the non-resonant contributions, is denoted as Z → 4` from here on, except that the branching

frac-tion ΓZ→4`/ΓZrefers to the s-channel contribution alone.

The CMS Collaboration has observed the Z → 4`

reso-nance in √s = 7 TeV data and determined a branching

fraction, summed over the 4e, 4µ and 2e2µ final states, of

ΓZ→4`/ΓZ = 4.2+0.9_−0.8(stat) ± 0.2 (syst)
× 10−6, where

80 < m4` < 100 GeV and m`` > 4 GeV for all pairs of

leptons (regardless of lepton flavor or charge) [6]. The

results presented here include the first cross section

mea-surement of the 4` production at the Z resonance at√s =

8 TeV, and a determination of ΓZ→4`/ΓZ with improved

statistical precision.

The inclusive 4` production cross section at the Z resonance is measured separately for the 4e, 4µ and

2e2µ final states for each of the √s = 7 and 8 TeV

datasets in a fiducial region (defined below) correspond-ing closely to the experimental acceptance. The mea-sured fiducial cross sections are then extrapolated to a final phase-space region defined by the dilepton and

four-lepton invariant mass requirements m`+<sub>`</sub>− > 5 GeV and

80 < m4` < 100 GeV, where `+`− denotes all

same-flavor lepton pairs with opposite charge. The branching

fraction ΓZ_→4`/ΓZ is determined by normalizing the

res-onant 4` production rate to the Z → µ+_µ− _production

rate measured in the same dataset.

The ATLAS detector has a cylindrical geometry [7] and

consists of an inner tracking detector surrounded by a 2 T superconducting solenoid, electromagnetic and hadronic calorimeters, and a muon spectrometer with a toroidal magnetic field. The inner detector (ID) provides preci-sion tracking for charged particles for |η| < 2.5. It con-sists of silicon pixel and strip detectors surrounded by a straw tube tracker that also provides transition radiation measurements for electron identification. The calorime-ter system covers the pseudorapidity range |η| < 4.9. For |η| < 2.5, the liquid-argon electromagnetic calorimeter is finely segmented and plays an important role in elec-tron identification. The muon spectrometer includes

fast-trigger chambers (|η| < 2.4) and high-precision tracking chambers covering |η| < 2.7.

The datasets for this analysis are recorded using single-lepton and disingle-lepton triggers. The transverse momentum

(pT) thresholds of these triggers vary from 20 to 24 GeV

for the single-lepton triggers and from 8 to 13 GeV for the dilepton triggers, depending on lepton flavor and data-taking period. The overall trigger efficiency for Z → 4` events ranges from 94 to 99%.

After removing the short data-taking periods having problems that affect the lepton reconstruction, the total

integrated luminosity used in the analysis is 4.5 fb−1 _at

7 TeV and 20.3 fb−1 _{at 8 TeV. The overall uncertainty}

on the integrated luminosity is 1.8% [8] and 2.8% [9] for

the√s = 7 and 8 TeV datasets, respectively.

The Powheg Monte Carlo (MC) program [10–12],

used to calculate the signal cross sections, includes per-turbative QCD corrections to next-to-leading order. The calculation also includes the interference terms between the s-channel and the t-channel as well as the

interfer-ence terms between the Z and the γ∗ _{diagrams. The}

CT10 [13] set of parton distribution functions (PDFs)

and QCD renormalization and factorization scales of

µR, µF = m4` are used. In the m`+_`− > 5 GeV and

80 < m4` < 100 GeV phase space, the production

cross sections calculated by Powheg are 53.4 ± 1.2 fb (45.8 ± 1.1 fb) for the sum of the 4e and 4µ final states, and 51.5 ± 1.2 fb (44.2 ± 1.1 fb) for the 2e2µ final state at 8 TeV (7 TeV). The cross sections for 4e and 4µ are larger than for 2e2µ due to the interference between the two same-flavor lepton pairs. The expected fraction

of 4` events produced via the t-channel process, ft, is

(3.35 ± 0.02) % and (3.90 ± 0.02) % for same-flavor (4e, 4µ) and mixed-flavor (2e2µ) final states, respectively, for both 7 and 8 TeV. The gg → ZZ → 4` process is

mod-eled by gg2zz [14], and the 4` event fraction from this

process is calculated to be around 0.1%. The overall

non-resonant fraction (fnr) from the t-channel and gg

contri-butions combined is (3.45 ± 0.02)% and (4.00 ± 0.02)% for the same-flavor and mixed-flavor final states, respec-tively. To generate MC events with a simulation of the detector to determine the signal acceptance, Powheg is

interfaced to Pythia6 [15] or Pythia8 [16] for

shower-ing and hadronization and to Photos [17] for radiated

photons from charged leptons.

The MC generators used to simulate the reducible

background contributions are MC@NLO [18] (to model

t¯t and single-top production) and Alpgen [19] (to model

Z boson production in association with jets, referred to as

Z+jets). These generators are interfaced to Herwig [20]

and Jimmy [21] for parton showering and

underlying-event simulations. The diboson background processes

W Z and Zγ, and Z(∗)Z(∗) → 4` decays involving τ →

e/µ+2ν, are modeled by Powheg (interfaced to Pythia

for parton showering) and Sherpa [22].

The detector response simulation [23] is based on the

GEANT4 program [24]. Additional inelastic pp

interac-tions (referred to as pile-up) are included in the simu-lation, and events are re-weighted to reproduce the ob-served distribution of the average number of collisions per bunch-crossing in the data.

The Z → 4` event selection closely follows the H →

ZZ∗ _{→ 4` analysis [25] with muon p}

T and dilepton

in-variant mass requirements loosened to increase the ac-ceptance for the Z → 4` process.

Muons are identified by tracks (or track segments) re-constructed in the muon spectrometer and are matched to tracks reconstructed in the ID. The muon momen-tum is calculated by combining the information from the two subsystems, correcting for the energy lost in the calorimeters. Additionally, one muon in each event is al-lowed to be a stand-alone muon or a calorimeter-tagged muon, where the stand-alone muon is identified by only a muon spectrometer track in 2.5 < |η| < 2.7, and the calorimeter-tagged muon is identified by an ID track with

pT > 15 GeV associated with a compatible calorimeter

energy deposit in |η| < 0.1. All muon candidates are

required to have pT > 4 GeV and |η| < 2.7.

Electrons are reconstructed from energy deposits in the electromagnetic calorimeter matched to a track in

the ID [26]. Tracks associated with electromagnetic

clus-ters are fitted using a Gaussian Sum Filter [27], which

allows bremsstrahlung energy losses to be taken into

ac-count. For√s = 8 TeV data, improved electron

discrim-ination from jets is obtained using a likelihood function formed from parameters characterizing the shower shape and track association, resulting in a reduction of the elec-tron misidentification rate by more than a factor of two compared to that at 7 TeV. Electron candidates are

re-quired to have pT> 7 GeV and |η| < 2.47.

Collision events are selected by requiring at least one reconstructed vertex with at least three charged

parti-cle tracks with pT > 0.4 GeV. If more than one vertex

satisfies the selection requirement, the primary vertex is

chosen as the one with the highestP p2

T, summed over

all tracks associated with the vertex.

In order to reject electrons and muons from jets, only isolated leptons are selected, requiring the scalar sum of

the transverse momenta,P pT, of other tracks inside a

cone size of ∆R = p(∆η)2_{+ (∆φ)}2 _{= 0.2 around the}

lepton to be less than 15% of the lepton pT. In addition,

theP ETdeposited in calorimeter cells inside a cone size

of ∆R = 0.2 around the lepton direction, excluding the transverse energy due to the lepton and corrected for the expected pile-up contribution, is required to be less than

30% of the lepton pT, reduced to 20% for electrons in

the 8 TeV dataset and 15% for stand-alone muons. To further reject leptons from heavy-flavor jets, the impact parameter relative to the primary vertex is required to be less than 3.5 (6.0) standard deviations for all muons (electrons), where the looser electron requirement allows for tails in the electron impact parameter distribution

due to bremsstrahlung in the ID.

Candidate quadruplets are formed by selecting two opposite-sign, same-flavor dilepton pairs in an event. The four leptons of the quadruplets are required to be well separated, ∆R > 0.1 for same-flavor lepton pairs and ∆R > 0.2 for eµ pairs. The two leading leptons must

have pT > 20 GeV and pT > 15 GeV. The third lepton

must have pT > 10 (8) GeV if it is an electron (muon).

The dilepton pair with greatest invariant mass (denoted

m12) is called the leading lepton pair, while the

sub-leading lepton pair is chosen to have the largest

invari-ant mass (denoted m34) among the remaining possible

pairs. The dilepton masses must satisfy m12 > 20 GeV

and m34 > 5 GeV. In the 4e and 4µ channels all

same-flavor, opposite-sign lepton pairs are required to have

m`+`− > 5 GeV. This helps to reject events containing

J/ψ → `+<sub>`</sub>− _{decays. The invariant mass of the lepton}

quadruplet is restricted to 80 < m4`< 100 GeV. A total

of 21 and 151 Z → 4` candidate events are selected in the 7 and 8 TeV datasets, respectively. The distributions

of m12, m34, and m4` are shown in Fig. 2. The number

of events observed in each channel is shown in Table I.

The 2e2µ channel is divided into ee + µµ and µµ + ee channels indicating the lepton flavors of the leading and sub-leading lepton pairs.

The overall signal selection efficiency is the product of

efficiency and acceptance factors, C4` and A4`,

respec-tively. The efficiency factor C4` is the ratio of the

num-ber of Z → 4` events passing the reconstructed event selections to the number in the fiducial region, and is determined using the signal MC samples after the detec-tor simulation. The fiducial region, defined at the MC generator level using the lepton four-momenta, requires

pT> 20, 15, 10(8), 7(4) GeV and |η| < 2.5(2.7) of the pT

-ordered e(µ), ∆R(`, `0_{) > 0.1(0.2) for all}

same(different)-flavor lepton pairs, m`+<sub>`</sub>− > 20 GeV for at least one

lepton pair, m`+<sub>`</sub>− > 5 GeV for all same-flavor lepton

pairs, and 80 < m4` < 100 GeV. The four-momenta of

all final state photons within ∆R = 0.1 of a lepton are summed into the four-momentum of that lepton. The

acceptance factor A4`is the fraction of Z → 4` events in

the final phase space which falls into the fiducial region.

The C4` uncertainty is mostly experimental and the A4`

uncertainty is entirely theoretical. The A4`and C4`

val-ues are listed in Table I for each channel and dataset.

The C4` values for 8 TeV are larger than for 7 TeV due

to a variety of factors, including electron identification improvements with better bremsstrahlung treatment and additional muon detector coverage.

The MC lepton identification and trigger efficiencies are corrected based on studies performed in data control regions. The energy and momentum scales and resolu-tions of the MC events are calibrated to reproduce data

from Z → `+<sub>`</sub>− _{and J/ψ → `</sub>+<sub>`}− _{decays. The}

uncer-tainties on the Z → 4` signal detection efficiency are de-termined by varying the nominal calibrations (including

lepton energy and momentum resolutions and scales, and the trigger, reconstruction and identification efficiencies) in the MC samples by one standard deviation. For the 8 TeV (7 TeV) analysis, the relative uncertainties on the

C4` factors are 2.7% (2.7%), 3.7% (4.9%), 6.2% (9.8%),

and 9.4% (14.9%) for µµ + µµ, ee + µµ, µµ + ee, and

ee + ee, respectively, where the labeling `` + `0<sub>`</sub>0 _indicates

the leading and sub-leading lepton pairs. The major un-certainty contributions come from the lepton reconstruc-tion and identificareconstruc-tion efficiencies.

The relative uncertainties on the A4` factors,

evalu-ated using Powheg MC samples, range from 1.3% to 1.7% depending on channel. The theoretical uncertain-ties reflect uncertainuncertain-ties from the choice of QCD scales and PDFs. The scales are varied independently from 0.5

to 2.0 times the nominal µR, µF= m4`. The PDF

uncer-tainties are estimated by taking the sum in quadrature

of the deviations of A4`for each PDF error set (52 CT10

eigenvectors varied by one standard deviation) and for

an alternative PDF set, MSTW2008 [28], with respect to

the nominal one.

The overall background in the selected 4` event

sam-ple is estimated to be below 1%, as shown in Table I.

The background contributions from diboson production are estimated, using MC simulations, to be 0.06 ± 0.01 and 0.49 ± 0.04 events in the 7 and 8 TeV datasets, re-spectively. Background contributions from Z+jets and top production processes are estimated from data. Such background events may contain two isolated leptons from Z decays or from W decays in top events, together with additional activity such as heavy-flavor jets or misidenti-fied components of jets yielding reconstructed leptons. These backgrounds are estimated from data using a

background-enriched control sample of ``j`j` events,

se-lected with the standard signal requirements except that

lepton-like jets, j`, are selected in place of two of the

signal leptons. Electron-like jets, je, in the ``j`j`

con-trol sample are obtained from electromagnetic clusters matched to tracks in the ID that do not satisfy the iden-tification criteria or isolation requirements. Muon-like

jets, jµ, are defined as muon candidates that fail the

re-quirements on isolation. The reducible background in the signal sample is estimated by scaling each event in

the ``j`j` control sample by f1× f2, where the factor

fi (i = 1, 2) for each of the two lepton-like jets depends

on lepton flavor and pT. The factor f is the ratio of

the probability for a jet to satisfy the signal lepton se-lection criteria to the probability for the jet to satisfy the lepton-like jet criteria, and is obtained from indepen-dent jet-enriched data samples dominated by Z+jets or

t¯t events. The uncertainties on f are determined from

the variations of f in data samples obtained with alter-native lepton-like jet selections and different jet compo-sitions. The estimated background from Z+jets and top processes ranges from 0.05 to 0.20 events for the different channels and datasets; for all 4` channels combined it is

[GeV] 12 m 20 30 40 50 60 70 80 90 100 Events / 2.5 GeV 0 5 10 15 20 25 30 35 ATLAS -1 = 7 TeV, 4.5 fb s -1

(a)

= 8 TeV, 20.3 fb s Data Z Bkg stat+syst σ 4l → Z [GeV] 34 m 0 5 10 15 20 25 30 35 40 45 50 Events / 2.5 GeV 0 10 20 30 40 50 60 70 80 90 ATLAS -1 = 7 TeV, 4.5 fb s -1

(b)

= 8 TeV, 20.3 fb s Data Z Bkg stat+syst σ 4l → Z [GeV] 4l m 75 80 85 90 95 100 105 Events / 3 GeV 0 20 40 60 80 100 120 ATLAS -1 = 7 TeV, 4.5 fb s -1

(c)

= 8 TeV, 20.3 fb s Data Z Bkg stat+syst σ 4l → Z

FIG. 2. Invariant mass distributions of (a) the leading lepton pair, m12, (b) the subleading lepton pair, m34 , and (c) the

four-lepton system, m4`. The MC simulation expectation for a combination of all channels is compared to

√

s = 7 and 8 TeV data. All selections are applied except in (c) there is no m4` requirement. The background contributes < 1% of the total

expected signal (invisible in the plots).

TABLE I. Summary of the observed (Nobs

4` ) and expected (N exp

4` ) number of selected Z → 4` candidate events, and the estimated

number of background events (N<sub>4`</sub>bkg) in each 4` channel for√s = 7 and 8 TeV. The associated uncertainties are statistical and systematic combined. The central values of the acceptance and efficiency factors (A4`) and (C4`), the measured fiducial cross

sections (σZ4`fid ), and the total cross sections for m`+<sub>`</sub>− > 5 GeV, 80 < m4`< 100 GeV (σZ4`) are also presented. The fiducial

regions are defined in the text and are different for each channel. The σZ4`are given for same-flavor (4e and 4µ), different-flavor

(2e2µ), and all channels combined. The uncertainties on σfidZ4` and σZ4` are the statistical and systematic uncertainties, and

the uncertainty due to the luminosity measurement. √ s 4` state N4`obs N exp 4` N bkg 4` C4` σfidZ4` [fb] A4` σZ4`[fb] 7 TeV ee + ee 1 1.8 ± 0.3 0.12 ± 0.04 21.5% 0.9+1.4−0.7± 0.14 ± 0.02 7.5% o_{4e, 4µ 32 ± 11 ± 1.0 ± 0.6} µµ + µµ 8 11.3 ± 0.5 0.08 ± 0.04 59.2% 3.0+1.2−0.9± 0.07 ± 0.05 18.3% ee + µµ 7 7.9 ± 0.4 0.18 ± 0.09 49.0% 3.1+1.4−1.1± 0.16 ± 0.05 15.8% o_{2e2µ 44 ± 14 ± 3.3 ± 0.9} µµ + ee 5 3.3 ± 0.3 0.07 ± 0.04 36.3% 3.0+1.6 −1.2± 0.30 ± 0.06 8.8% combined 21 24.2 ± 1.2 0.44 ± 0.14 76 ± 18 ± 4 ± 1.4 8 TeV ee + ee 16 14.4 ± 1.4 0.14 ± 0.03 36.1% 2.2+0.6−0.5± 0.20 ± 0.06 7.3% o_{4e, 4µ 56 ± 6 ± 1.8 ± 1.6} µµ + µµ 71 68.8 ± 2.7 0.34 ± 0.05 71.1% 4.9+0.7−0.6± 0.13 ± 0.14 17.8% ee + µµ 48 43.2 ± 2.1 0.32 ± 0.05 55.5% 4.2+0.7−0.6± 0.16 ± 0.12 14.8% o_{2e2µ 52 ± 7 ± 2.4 ± 1.5} µµ + ee 16 19.3 ± 1.3 0.18 ± 0.04 46.2% 1.7+0.5 −0.4± 0.10 ± 0.04 7.9% combined 151 146 ± 7 1.0 ± 0.11 107 ± 9 ± 4 ± 3.0

estimated to be 0.38 ± 0.14 and 0.49 ± 0.10 events for the 7 and 8 TeV data, respectively.

The numbers of signal events predicted by MC simu-lation are 23.8 ± 1.2 and 145 ± 7 for 7 and 8 TeV,

respec-tively. The data and MC predictions, as shown in Fig.2,

are in good agreement. Denoting the integrated

lumi-nosity by L, the measured fiducial cross sections (σfid

Z4`),

determined by (Nobs

4` - N bkg

4` )/(L × C4`), are given in

Ta-bleI.

The cross section in the final phase space for each

chan-nel is calculated by σfid

Z4`/A4`. The cross sections

ob-tained for the ee + ee and µµ + µµ channels, and for the 2e+2µ and 2µ+2e channels, are compatible within errors and are combined using 2 × 2 covariance matrices. The total inclusive 4` cross section is a sum of the two

com-bined cross sections, and the uncertainty includes cor-relations between the four channels. The cross sections

listed in TableI are consistent with the SM predictions

given earlier.

The Z → 4` branching fraction, ΓZ→4`/ΓZ, is

deter-mined by subtracting the non-resonant contributions to the selected events and normalizing the resulting yield to

the observed number of Z → µ+_µ− _{events in the same}

dataset, ΓZ→4` ΓZ = ΓZ→µµ ΓZ   Nobs 4` − N bkg 4`  (1 − fnr) C2µ· A2µ  Nobs 2µ − N bkg 2µ  C4`· A4` , where ΓZ→µµ/ΓZ = (3.366 ± 0.007) % [29], N2µobs is

datasets, respectively, and (C × A)2µ is (41.4 ± 0.6) %

and (41.8 ± 0.6) %, respectively. The background (N2µbkg)

is estimated to be around 0.3% of the selected Z → µ+_µ−

events, where the multijet and W +jets contributions are obtained using a data-driven method similar to that used for the Z → 4` background estimation, and other back-ground contributions are estimated with simulated MC samples. The branching fraction for Z → 4`, summed over all ` = e, µ final states, is determined with both the 7 and 8 TeV datasets. The measured branching fractions for each dataset are consistent within uncertainties and are combined, giving

ΓZ→4`/ΓZ = (3.20 ± 0.25 (stat) ± 0.13 (syst)) × 10−6

in the final phase-space region, where the systematic un-certainty includes a contribution (about 0.2%) due to the interference between the s-channel and t-channel

pro-cesses, calculated using CalcHep [30]. The measured

branching fraction is consistent with the SM prediction

of (3.33 ± 0.01) × 10−6, calculated using Powheg. For

a larger final phase-space region defined by m`+<sub>`</sub>− >

4 GeV and 80 < m4` < 100 GeV, similar to that

used by CMS, the acceptance factors A4` and the

non-resonant fractions fnr, and their uncertainties, are also

evaluated (leaving the fiducial region unchanged), and

the measured branching fraction becomes ΓZ→4`/ΓZ =

(4.31 ± 0.34 (stat) ± 0.17 (syst)) × 10−6_{, compared with}

an SM prediction of (4.50 ± 0.01) × 10−6_{. This result}

is consistent with the CMS result measured with data collected from pp collisions at 7 TeV.

In summary, measurements of the cross sections of 4` production at the Z resonance in pp collision data col-lected by the ATLAS detector at the LHC have been presented. The datasets analyzed correspond to an

in-tegrated luminosity of 4.5 fb−1 _{and 20.3 fb}−1 _at√_{s = 7}

and 8 TeV, respectively. The total Z → 4` production

cross sections in the phase-space region m`+<sub>`</sub>− > 5 GeV

and 80 < m4`< 100 GeV are measured to be σZ4`= 76±

18 (stat) ± 4 (syst) ± 1.4 (lumi) fb at 7 TeV and 107 ± 9 (stat) ± 4 (syst) ± 3.0 (lumi) fb at 8 TeV, consistent with the SM predictions of 90.0±2.1 fb and 104.8±2.5 fb,

respectively. Normalizing to the measured Z → µ+_µ−

production, the Z → 4` branching fraction is determined

to be (3.20 ± 0.25 (stat) ± 0.13 (syst)) × 10−6, consistent

with the SM prediction of (3.33 ± 0.01) × 10−6.

We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWF and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC

and Lundbeck Foundation, Denmark; EPLANET, ERC

and NSRF, European Union; IN2P3-CNRS,

CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; GSRT and NSRF, Greece; ISF, MINERVA, GIF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; BRF and RCN, Norway; MNiSW and NCN, Poland; GRICES and FCT, Portugal; MNE/IFA, Romania; MES of Russia and ROSATOM, Russian Federation; JINR;

MSTD, Serbia; MSSR, Slovakia; ARRS and MIZˇS,

Slove-nia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SER, SNSF and Cantons of Bern and Geneva, Switzerland; NSC, Tai-wan; TAEK, Turkey; STFC, the Royal Society and Lev-erhulme Trust, United Kingdom; DOE and NSF, United States of America.

The crucial computing support from all WLCG part-ners is acknowledged gratefully, in particular from CERN and the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Tai-wan), RAL (UK) and BNL (USA) and in the Tier-2 fa-cilities worldwide.

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G. Aad84_{, B. Abbott}112_{, J. Abdallah}152_{, S. Abdel Khalek}116_{, O. Abdinov}11_{, R. Aben}106_{, B. Abi}113_{, M. Abolins}89_,

O.S. AbouZeid159, H. Abramowicz154, H. Abreu137, R. Abreu30, Y. Abulaiti147a,147b, B.S. Acharya165a,165b,a,

L. Adamczyk38a_{, D.L. Adams}25_{, J. Adelman}177_{, S. Adomeit}99_{, T. Adye}130_{, T. Agatonovic-Jovin}13a_,

J.A. Aguilar-Saavedra125f,125a_{, M. Agustoni}17_{, S.P. Ahlen}22_{, A. Ahmad}149_{, F. Ahmadov}64,b_{, G. Aielli}134a,134b_,

H. Akerstedt147a,147b_{, T.P.A. ˚Akesson}80_{, G. Akimoto}156_{, A.V. Akimov}95_{, G.L. Alberghi}20a,20b_{, J. Albert}170_,

S. Albrand55_{, M.J. Alconada Verzini}70_{, M. Aleksa}30_{, I.N. Aleksandrov}64_{, C. Alexa}26a_{, G. Alexander}154_,

G. Alexandre49_{, T. Alexopoulos}10_{, M. Alhroob}165a,165c_{, G. Alimonti}90a_{, L. Alio}84_{, J. Alison}31_{, B.M.M. Allbrooke}18_,

L.J. Allison71_{, P.P. Allport}73_{, S.E. Allwood-Spiers}53_{, J. Almond}83_{, A. Aloisio}103a,103b_{, A. Alonso}36_{, F. Alonso}70_,

C. Alpigiani75_{, A. Altheimer}35_{, B. Alvarez Gonzalez}89_{, M.G. Alviggi}103a,103b_{, K. Amako}65_{, Y. Amaral Coutinho}24a_,

C. Amelung23_{, D. Amidei}88_{, S.P. Amor Dos Santos}125a,125c_{, A. Amorim}125a,125b_{, S. Amoroso}48_{, N. Amram}154_,

G. Amundsen23_{, C. Anastopoulos}140_{, L.S. Ancu}49_{, N. Andari}30_{, T. Andeen}35_{, C.F. Anders}58b_{, G. Anders}30_,

K.J. Anderson31_{, A. Andreazza}90a,90b_{, V. Andrei}58a_{, X.S. Anduaga}70_{, S. Angelidakis}9_{, I. Angelozzi}106_{, P. Anger}44_,

A. Angerami35_{, F. Anghinolfi}30_{, A.V. Anisenkov}108_{, N. Anjos}125a_{, A. Annovi}47_{, A. Antonaki}9_{, M. Antonelli}47_,

A. Antonov97_{, J. Antos}145b_{, F. Anulli}133a_{, M. Aoki}65_{, L. Aperio Bella}18_{, R. Apolle}119,c_{, G. Arabidze}89_,

I. Aracena144_{, Y. Arai}65_{, J.P. Araque}125a_{, A.T.H. Arce}45_{, J-F. Arguin}94_{, S. Argyropoulos}42_{, M. Arik}19a_,

A.J. Armbruster30_{, O. Arnaez}82_{, V. Arnal}81_{, H. Arnold}48_{, O. Arslan}21_{, A. Artamonov}96_{, G. Artoni}23_{, S. Asai}156_,

N. Asbah94, A. Ashkenazi154, B. ˚Asman147a,147b, L. Asquith6, K. Assamagan25, R. Astalos145a, M. Atkinson166,

N.B. Atlay142_{, B. Auerbach}6_{, K. Augsten}127_{, M. Aurousseau}146b_{, G. Avolio}30_{, G. Azuelos}94,d_{, Y. Azuma}156_,

M.A. Baak30_{, C. Bacci}135a,135b_{, H. Bachacou}137_{, K. Bachas}155_{, M. Backes}30_{, M. Backhaus}30_{, J. Backus Mayes}144_,

E. Badescu26a_{, P. Bagiacchi}133a,133b_{, P. Bagnaia}133a,133b_{, Y. Bai}33a_{, T. Bain}35_{, J.T. Baines}130_{, O.K. Baker}177_,

S. Baker77_{, P. Balek}128_{, F. Balli}137_{, E. Banas}39_{, Sw. Banerjee}174_{, D. Banfi}30_{, A. Bangert}151_{, A.A.E. Bannoura}176_,

V. Bansal170_{, H.S. Bansil}18_{, L. Barak}173_{, S.P. Baranov}95_{, E.L. Barberio}87_{, D. Barberis}50a,50b_{, M. Barbero}84_,

T. Barillari100_{, M. Barisonzi}176_{, T. Barklow}144_{, N. Barlow}28_{, B.M. Barnett}130_{, R.M. Barnett}15_{, Z. Barnovska}5_,

A. Baroncelli135a_{, G. Barone}49_{, A.J. Barr}119_{, F. Barreiro}81_{, J. Barreiro Guimar˜aes da Costa}57_{, R. Bartoldus}144_,

A.E. Barton71_{, P. Bartos}145a_{, V. Bartsch}150_{, A. Bassalat}116_{, A. Basye}166_{, R.L. Bates}53_{, L. Batkova}145a_,

J.R. Batley28_{, M. Battistin}30_{, F. Bauer}137_{, H.S. Bawa}144,e_{, T. Beau}79_{, P.H. Beauchemin}162_{, R. Beccherle}123a,123b_,

P. Bechtle21_{, H.P. Beck}17_{, K. Becker}176_{, S. Becker}99_{, M. Beckingham}139_{, C. Becot}116_{, A.J. Beddall}19c_{, A. Beddall}19c_,

S. Bedikian177_{, V.A. Bednyakov}64_{, C.P. Bee}149_{, L.J. Beemster}106_{, T.A. Beermann}176_{, M. Begel}25_{, K. Behr}119_,

C. Belanger-Champagne86_{, P.J. Bell}49_{, W.H. Bell}49_{, G. Bella}154_{, L. Bellagamba}20a_{, A. Bellerive}29_{, M. Bellomo}85_,

A. Belloni57_{, O.L. Beloborodova}108,f_{, K. Belotskiy}97_{, O. Beltramello}30_{, O. Benary}154_{, D. Benchekroun}136a_,

K. Bendtz147a,147b_{, N. Benekos}166_{, Y. Benhammou}154_{, E. Benhar Noccioli}49_{, J.A. Benitez Garcia}160b_,

D.P. Benjamin45, J.R. Bensinger23, K. Benslama131, S. Bentvelsen106, D. Berge106, E. Bergeaas Kuutmann16,

N. Berger5_{, F. Berghaus}170_{, E. Berglund}106_{, J. Beringer}15_{, C. Bernard}22_{, P. Bernat}77_{, C. Bernius}78_,

F.U. Bernlochner170_{, T. Berry}76_{, P. Berta}128_{, C. Bertella}84_{, F. Bertolucci}123a,123b_{, D. Bertsche}112_{, M.I. Besana}90a_,

G.J. Besjes105_{, O. Bessidskaia}147a,147b_{, N. Besson}137_{, C. Betancourt}48_{, S. Bethke}100_{, W. Bhimji}46_{, R.M. Bianchi}124_,

L. Bianchini23_{, M. Bianco}30_{, O. Biebel}99_{, S.P. Bieniek}77_{, K. Bierwagen}54_{, J. Biesiada}15_{, M. Biglietti}135a_,

J. Bilbao De Mendizabal49_{, H. Bilokon}47_{, M. Bindi}54_{, S. Binet}116_{, A. Bingul}19c_{, C. Bini}133a,133b_{, C.W. Black}151_,

J.E. Black144_{, K.M. Black}22_{, D. Blackburn}139_{, R.E. Blair}6_{, J.-B. Blanchard}137_{, T. Blazek}145a_{, I. Bloch}42_,

C. Blocker23_{, W. Blum}82,∗_{, U. Blumenschein}54_{, G.J. Bobbink}106_{, V.S. Bobrovnikov}108_{, S.S. Bocchetta}80_{, A. Bocci}45_,

C.R. Boddy119_{, M. Boehler}48_{, J. Boek}176_{, T.T. Boek}176_{, J.A. Bogaerts}30_{, A.G. Bogdanchikov}108_{, A. Bogouch}91,∗_,

C. Bohm147a_{, J. Bohm}126_{, V. Boisvert}76_{, T. Bold}38a_{, V. Boldea}26a_{, A.S. Boldyrev}98_{, M. Bomben}79_{, M. Bona}75_,

M. Boonekamp137_{, A. Borisov}129_{, G. Borissov}71_{, M. Borri}83_{, S. Borroni}42_{, J. Bortfeldt}99_{, V. Bortolotto}135a,135b_,

K. Bos106_{, D. Boscherini}20a_{, M. Bosman}12_{, H. Boterenbrood}106_{, J. Boudreau}124_{, J. Bouffard}2_,

E.V. Bouhova-Thacker71_{, D. Boumediene}34_{, C. Bourdarios}116_{, N. Bousson}113_{, S. Boutouil}136d_{, A. Boveia}31_,

J. Boyd30_{, I.R. Boyko}64_{, I. Bozovic-Jelisavcic}13b_{, J. Bracinik}18_{, P. Branchini}135a_{, A. Brandt}8_{, G. Brandt}15_,

O. Brandt58a_{, U. Bratzler}157_{, B. Brau}85_{, J.E. Brau}115_{, H.M. Braun}176,∗_{, S.F. Brazzale}165a,165c_{, B. Brelier}159_,

K. Brendlinger121, A.J. Brennan87, R. Brenner167, S. Bressler173, K. Bristow146c, T.M. Bristow46, D. Britton53,

F.M. Brochu28_{, I. Brock}21_{, R. Brock}89_{, C. Bromberg}89_{, J. Bronner}100_{, G. Brooijmans}35_{, T. Brooks}76_,

W.K. Brooks32b_{, J. Brosamer}15_{, E. Brost}115_{, G. Brown}83_{, J. Brown}55_{, P.A. Bruckman de Renstrom}39_,

D. Bruncko145b_{, R. Bruneliere}48_{, S. Brunet}60_{, A. Bruni}20a_{, G. Bruni}20a_{, M. Bruschi}20a_{, L. Bryngemark}80_,

T. Buanes14_{, Q. Buat}143_{, F. Bucci}49_{, P. Buchholz}142_{, R.M. Buckingham}119_{, A.G. Buckley}53_{, S.I. Buda}26a_,

I.A. Budagov64_{, F. Buehrer}48_{, L. Bugge}118_{, M.K. Bugge}118_{, O. Bulekov}97_{, A.C. Bundock}73_{, H. Burckhart}30_,

S. Burdin73_{, B. Burghgrave}107_{, S. Burke}130_{, I. Burmeister}43_{, E. Busato}34_{, D. B¨uscher}48_{, V. B¨uscher}82_{, P. Bussey}53_,

W. Buttinger28_{, A. Buzatu}53_{, M. Byszewski}10_{, S. Cabrera Urb´an}168_{, D. Caforio}20a,20b_{, O. Cakir}4a_{, P. Calafiura}15_,

A. Calandri137_{, G. Calderini}79_{, P. Calfayan}99_{, R. Calkins}107_{, L.P. Caloba}24a_{, D. Calvet}34_{, S. Calvet}34_,

R. Camacho Toro49_{, S. Camarda}42_{, D. Cameron}118_{, L.M. Caminada}15_{, R. Caminal Armadans}12_{, S. Campana}30_,

M. Campanelli77, A. Campoverde149, V. Canale103a,103b, A. Canepa160a, M. Cano Bret75, J. Cantero81,

R. Cantrill76_{, T. Cao}40_{, M.D.M. Capeans Garrido}30_{, I. Caprini}26a_{, M. Caprini}26a_{, M. Capua}37a,37b_{, R. Caputo}82_,

R. Cardarelli134a_{, T. Carli}30_{, G. Carlino}103a_{, L. Carminati}90a,90b_{, S. Caron}105_{, E. Carquin}32a_,

G.D. Carrillo-Montoya146c_{, A.A. Carter}75_{, J.R. Carter}28_{, J. Carvalho}125a,125c_{, D. Casadei}77_{, M.P. Casado}12_,

E. Castaneda-Miranda146b_{, A. Castelli}106_{, V. Castillo Gimenez}168_{, N.F. Castro}125a_{, P. Catastini}57_{, A. Catinaccio}30_,

J.R. Catmore118_{, A. Cattai}30_{, G. Cattani}134a,134b_{, S. Caughron}89_{, V. Cavaliere}166_{, D. Cavalli}90a_,

M. Cavalli-Sforza12_{, V. Cavasinni}123a,123b_{, F. Ceradini}135a,135b_{, B. Cerio}45_{, K. Cerny}128_{, A.S. Cerqueira}24b_,

A. Cerri150_{, L. Cerrito}75_{, F. Cerutti}15_{, M. Cerv}30_{, A. Cervelli}17_{, S.A. Cetin}19b_{, A. Chafaq}136a_{, D. Chakraborty}107_,

I. Chalupkova128_{, K. Chan}3_{, P. Chang}166_{, B. Chapleau}86_{, J.D. Chapman}28_{, D. Charfeddine}116_{, D.G. Charlton}18_,

C.C. Chau159_{, C.A. Chavez Barajas}150_{, S. Cheatham}86_{, A. Chegwidden}89_{, S. Chekanov}6_{, S.V. Chekulaev}160a_,

G.A. Chelkov64_{, M.A. Chelstowska}88_{, C. Chen}63_{, H. Chen}25_{, K. Chen}149_{, L. Chen}33d,g_{, S. Chen}33c_{, X. Chen}146c_,

Y. Chen35_{, H.C. Cheng}88_{, Y. Cheng}31_{, A. Cheplakov}64_{, R. Cherkaoui El Moursli}136e_{, V. Chernyatin}25,∗_{, E. Cheu}7_,

L. Chevalier137_{, V. Chiarella}47_{, G. Chiefari}103a,103b_{, J.T. Childers}6_{, A. Chilingarov}71_{, G. Chiodini}72a_,

A.S. Chisholm18_{, R.T. Chislett}77_{, A. Chitan}26a_{, M.V. Chizhov}64_{, S. Chouridou}9_{, B.K.B. Chow}99_,

D. Chromek-Burckhart30_{, M.L. Chu}152_{, J. Chudoba}126_{, J.C. Chwastowski}39_{, L. Chytka}114_{, G. Ciapetti}133a,133b_,

A.K. Ciftci4a, R. Ciftci4a, D. Cinca62, V. Cindro74, A. Ciocio15, P. Cirkovic13b, Z.H. Citron173, M. Citterio90a,

M. Ciubancan26a_{, A. Clark}49_{, P.J. Clark}46_{, R.N. Clarke}15_{, W. Cleland}124_{, J.C. Clemens}84_{, C. Clement}147a,147b_,

Y. Coadou84_{, M. Cobal}165a,165c_{, A. Coccaro}139_{, J. Cochran}63_{, L. Coffey}23_{, J.G. Cogan}144_{, J. Coggeshall}166_,

B. Cole35_{, S. Cole}107_{, A.P. Colijn}106_{, C. Collins-Tooth}53_{, J. Collot}55_{, T. Colombo}58c_{, G. Colon}85_{, G. Compostella}100_,

P. Conde Mui˜no125a,125b_{, E. Coniavitis}167_{, M.C. Conidi}12_{, S.H. Connell}146b_{, I.A. Connelly}76_{, S.M. Consonni}90a,90b_,

V. Consorti48_{, S. Constantinescu}26a_{, C. Conta}120a,120b_{, G. Conti}57_{, F. Conventi}103a,h_{, M. Cooke}15_{, B.D. Cooper}77_,

A.M. Cooper-Sarkar119_{, N.J. Cooper-Smith}76_{, K. Copic}15_{, T. Cornelissen}176_{, M. Corradi}20a_{, F. Corriveau}86,i_,

A. Corso-Radu164_{, A. Cortes-Gonzalez}12_{, G. Cortiana}100_{, G. Costa}90a_{, M.J. Costa}168_{, D. Costanzo}140_{, D. Cˆot´e}8_,

G. Cottin28_{, G. Cowan}76_{, B.E. Cox}83_{, K. Cranmer}109_{, G. Cree}29_{, S. Cr´ep´e-Renaudin}55_{, F. Crescioli}79_,

W.A. Cribbs147a,147b_{, M. Crispin Ortuzar}119_{, M. Cristinziani}21_{, V. Croft}105_{, G. Crosetti}37a,37b_{, C.-M. Cuciuc}26a_,

C. Cuenca Almenar177_{, T. Cuhadar Donszelmann}140_{, J. Cummings}177_{, M. Curatolo}47_{, C. Cuthbert}151_{, H. Czirr}142_,

P. Czodrowski3_{, Z. Czyczula}177_{, S. D’Auria}53_{, M. D’Onofrio}73_{, M.J. Da Cunha Sargedas De Sousa}125a,125b_,

C. Da Via83_{, W. Dabrowski}38a_{, A. Dafinca}119_{, T. Dai}88_{, O. Dale}14_{, F. Dallaire}94_{, C. Dallapiccola}85_{, M. Dam}36_,

A.C. Daniells18_{, M. Dano Hoffmann}137_{, V. Dao}105_{, G. Darbo}50a_{, G.L. Darlea}26c_{, S. Darmora}8_{, J.A. Dassoulas}42_,

A. Dattagupta60_{, W. Davey}21_{, C. David}170_{, T. Davidek}128_{, E. Davies}119,c_{, M. Davies}154_{, O. Davignon}79_,

A.R. Davison77, P. Davison77, Y. Davygora58a, E. Dawe143, I. Dawson140, R.K. Daya-Ishmukhametova23, K. De8,

R. de Asmundis103a_{, S. De Castro}20a,20b_{, S. De Cecco}79_{, N. De Groot}105_{, P. de Jong}106_{, H. De la Torre}81_,

F. De Lorenzi63_{, L. De Nooij}106_{, D. De Pedis}133a_{, A. De Salvo}133a_{, U. De Sanctis}165a,165b_{, A. De Santo}150_,

J.B. De Vivie De Regie116_{, G. De Zorzi}133a,133b_{, W.J. Dearnaley}71_{, R. Debbe}25_{, C. Debenedetti}46_{, B. Dechenaux}55_,

D.V. Dedovich64_{, J. Degenhardt}121_{, I. Deigaard}106_{, J. Del Peso}81_{, T. Del Prete}123a,123b_{, F. Deliot}137_,

C.M. Delitzsch49_{, M. Deliyergiyev}74_{, A. Dell’Acqua}30_{, L. Dell’Asta}22_{, M. Dell’Orso}123a,123b_{, M. Della Pietra}103a,h_,

D. della Volpe49_{, M. Delmastro}5_{, P.A. Delsart}55_{, C. Deluca}106_{, S. Demers}177_{, M. Demichev}64_{, A. Demilly}79_,

S.P. Denisov129_{, D. Derendarz}39_{, J.E. Derkaoui}136d_{, F. Derue}79_{, P. Dervan}73_{, K. Desch}21_{, C. Deterre}42_,

P.O. Deviveiros106_{, A. Dewhurst}130_{, S. Dhaliwal}106_{, A. Di Ciaccio}134a,134b_{, L. Di Ciaccio}5_{, A. Di Domenico}133a,133b_,

C. Di Donato103a,103b_{, A. Di Girolamo}30_{, B. Di Girolamo}30_{, A. Di Mattia}153_{, B. Di Micco}135a,135b_{, R. Di Nardo}47_,

A. Di Simone48_{, R. Di Sipio}20a,20b_{, D. Di Valentino}29_{, M.A. Diaz}32a_{, E.B. Diehl}88_{, J. Dietrich}42_{, T.A. Dietzsch}58a_,

S. Diglio84_{, A. Dimitrievska}13a_{, J. Dingfelder}21_{, C. Dionisi}133a,133b_{, P. Dita}26a_{, S. Dita}26a_{, F. Dittus}30_{, F. Djama}84_,

T. Djobava51b_{, M.A.B. do Vale}24c_{, A. Do Valle Wemans}125a,125g_{, T.K.O. Doan}5_{, D. Dobos}30_{, C. Doglioni}49_,

T. Doherty53_{, T. Dohmae}156_{, J. Dolejsi}128_{, Z. Dolezal}128_{, B.A. Dolgoshein}97,∗_{, M. Donadelli}24d_{, S. Donati}123a,123b_,

P. Dondero120a,120b_{, J. Donini}34_{, J. Dopke}30_{, A. Doria}103a_{, A. Dos Anjos}174_{, M.T. Dova}70_{, A.T. Doyle}53_{, M. Dris}10_,

J. Dubbert88, S. Dube15, E. Dubreuil34, E. Duchovni173, G. Duckeck99, O.A. Ducu26a, D. Duda176, A. Dudarev30,

F. Dudziak63_{, L. Duflot}116_{, L. Duguid}76_{, M. D¨uhrssen}30_{, M. Dunford}58a_{, H. Duran Yildiz}4a_{, M. D¨uren}52_,

A. Durglishvili51b_{, M. Dwuznik}38a_{, M. Dyndal}38a_{, J. Ebke}99_{, W. Edson}2_{, N.C. Edwards}46_{, W. Ehrenfeld}21_,

T. Eifert144_{, G. Eigen}14_{, K. Einsweiler}15_{, T. Ekelof}167_{, M. El Kacimi}136c_{, M. Ellert}167_{, S. Elles}5_{, F. Ellinghaus}82_,

N. Ellis30_{, J. Elmsheuser}99_{, M. Elsing}30_{, D. Emeliyanov}130_{, Y. Enari}156_{, O.C. Endner}82_{, M. Endo}117_,

R. Engelmann149_{, J. Erdmann}177_{, A. Ereditato}17_{, D. Eriksson}147a_{, G. Ernis}176_{, J. Ernst}2_{, M. Ernst}25_{, J. Ernwein}137_,

D. Errede166_{, S. Errede}166_{, E. Ertel}82_{, M. Escalier}116_{, H. Esch}43_{, C. Escobar}124_{, B. Esposito}47_{, A.I. Etienvre}137_,

Y. Fang33a_{, M. Fanti}90a,90b_{, A. Farbin}8_{, A. Farilla}135a_{, T. Farooque}12_{, S. Farrell}164_{, S.M. Farrington}171_,

P. Farthouat30_{, F. Fassi}168_{, P. Fassnacht}30_{, D. Fassouliotis}9_{, A. Favareto}50a,50b_{, L. Fayard}116_{, P. Federic}145a_,

O.L. Fedin122,j_{, W. Fedorko}169_{, M. Fehling-Kaschek}48_{, S. Feigl}30_{, L. Feligioni}84_{, C. Feng}33d_{, E.J. Feng}6_{, H. Feng}88_,

A.B. Fenyuk129, S. Fernandez Perez30, S. Ferrag53, J. Ferrando53, A. Ferrari167, P. Ferrari106, R. Ferrari120a,

D.E. Ferreira de Lima53_{, A. Ferrer}168_{, D. Ferrere}49_{, C. Ferretti}88_{, A. Ferretto Parodi}50a,50b_{, M. Fiascaris}31_,

F. Fiedler82_{, A. Filipˇciˇc}74_{, M. Filipuzzi}42_{, F. Filthaut}105_{, M. Fincke-Keeler}170_{, K.D. Finelli}151_,

M.C.N. Fiolhais125a,125c_{, L. Fiorini}168_{, A. Firan}40_{, J. Fischer}176_{, W.C. Fisher}89_{, E.A. Fitzgerald}23_{, M. Flechl}48_,

I. Fleck142_{, P. Fleischmann}175_{, S. Fleischmann}176_{, G.T. Fletcher}140_{, G. Fletcher}75_{, T. Flick}176_{, A. Floderus}80_,

L.R. Flores Castillo174_{, A.C. Florez Bustos}160b_{, M.J. Flowerdew}100_{, A. Formica}137_{, A. Forti}83_{, D. Fortin}160a_,

D. Fournier116_{, H. Fox}71_{, S. Fracchia}12_{, P. Francavilla}79_{, M. Franchini}20a,20b_{, S. Franchino}30_{, D. Francis}30_,

M. Franklin57_{, S. Franz}61_{, M. Fraternali}120a,120b_{, S.T. French}28_{, C. Friedrich}42_{, F. Friedrich}44_{, D. Froidevaux}30_,

J.A. Frost28_{, C. Fukunaga}157_{, E. Fullana Torregrosa}82_{, B.G. Fulsom}144_{, J. Fuster}168_{, C. Gabaldon}55_{, O. Gabizon}173_,

A. Gabrielli20a,20b_{, A. Gabrielli}133a,133b_{, S. Gadatsch}106_{, S. Gadomski}49_{, G. Gagliardi}50a,50b_{, P. Gagnon}60_,

C. Galea105_{, B. Galhardo}125a,125c_{, E.J. Gallas}119_{, V. Gallo}17_{, B.J. Gallop}130_{, P. Gallus}127_{, G. Galster}36_,

K.K. Gan110_{, R.P. Gandrajula}62_{, J. Gao}33b,g_{, Y.S. Gao}144,e_{, F.M. Garay Walls}46_{, F. Garberson}177_{, C. Garc´ıa}168_,

J.E. Garc´ıa Navarro168_{, M. Garcia-Sciveres}15_{, R.W. Gardner}31_{, N. Garelli}144_{, V. Garonne}30_{, C. Gatti}47_,

G. Gaudio120a_{, B. Gaur}142_{, L. Gauthier}94_{, P. Gauzzi}133a,133b_{, I.L. Gavrilenko}95_{, C. Gay}169_{, G. Gaycken}21_,

E.N. Gazis10_{, P. Ge}33d_{, Z. Gecse}169_{, C.N.P. Gee}130_{, D.A.A. Geerts}106_{, Ch. Geich-Gimbel}21_{, K. Gellerstedt}147a,147b_,

C. Gemme50a, A. Gemmell53, M.H. Genest55, S. Gentile133a,133b, M. George54, S. George76, D. Gerbaudo164,

A. Gershon154_{, H. Ghazlane}136b_{, N. Ghodbane}34_{, B. Giacobbe}20a_{, S. Giagu}133a,133b_{, V. Giangiobbe}12_,

P. Giannetti123a,123b_{, F. Gianotti}30_{, B. Gibbard}25_{, S.M. Gibson}76_{, M. Gilchriese}15_{, T.P.S. Gillam}28_{, D. Gillberg}30_,

G. Gilles34_{, D.M. Gingrich}3,d_{, N. Giokaris}9_{, M.P. Giordani}165a,165c_{, R. Giordano}103a,103b_{, F.M. Giorgi}20a_,

F.M. Giorgi16_{, P.F. Giraud}137_{, D. Giugni}90a_{, C. Giuliani}48_{, M. Giulini}58b_{, B.K. Gjelsten}118_{, I. Gkialas}155,k_,

L.K. Gladilin98_{, C. Glasman}81_{, J. Glatzer}30_{, P.C.F. Glaysher}46_{, A. Glazov}42_{, G.L. Glonti}64_{, M. Goblirsch-Kolb}100_,

J.R. Goddard75_{, J. Godfrey}143_{, J. Godlewski}30_{, C. Goeringer}82_{, S. Goldfarb}88_{, T. Golling}177_{, D. Golubkov}129_,

A. Gomes125a,125b,125d_{, L.S. Gomez Fajardo}42_{, R. Gon¸calo}125a_{, J. Goncalves Pinto Firmino Da Costa}137_,

L. Gonella21_{, S. Gonz´alez de la Hoz}168_{, G. Gonzalez Parra}12_{, M.L. Gonzalez Silva}27_{, S. Gonzalez-Sevilla}49_,

L. Goossens30_{, P.A. Gorbounov}96_{, H.A. Gordon}25_{, I. Gorelov}104_{, G. Gorfine}176_{, B. Gorini}30_{, E. Gorini}72a,72b_,

A. Goriˇsek74_{, E. Gornicki}39_{, A.T. Goshaw}6_{, C. G¨ossling}43_{, M.I. Gostkin}64_{, M. Gouighri}136a_{, D. Goujdami}136c_,

M.P. Goulette49_{, A.G. Goussiou}139_{, C. Goy}5_{, S. Gozpinar}23_{, H.M.X. Grabas}137_{, L. Graber}54_{, I. Grabowska-Bold}38a_,

P. Grafstr¨om20a,20b_{, K-J. Grahn}42_{, J. Gramling}49_{, E. Gramstad}118_{, S. Grancagnolo}16_{, V. Grassi}149_{, V. Gratchev}122_,

H.M. Gray30_{, E. Graziani}135a_{, O.G. Grebenyuk}122_{, Z.D. Greenwood}78,l_{, K. Gregersen}77_{, I.M. Gregor}42_,

P. Grenier144_{, J. Griffiths}8_{, N. Grigalashvili}64_{, A.A. Grillo}138_{, K. Grimm}71_{, S. Grinstein}12,m_{, Ph. Gris}34_,

Y.V. Grishkevich98, J.-F. Grivaz116, J.P. Grohs44, A. Grohsjean42, E. Gross173, J. Grosse-Knetter54,

G.C. Grossi134a,134b_{, J. Groth-Jensen}173_{, Z.J. Grout}150_{, K. Grybel}142_{, L. Guan}33b_{, F. Guescini}49_{, D. Guest}177_,

O. Gueta154_{, C. Guicheney}34_{, E. Guido}50a,50b_{, T. Guillemin}116_{, S. Guindon}2_{, U. Gul}53_{, C. Gumpert}44_,

J. Gunther127_{, J. Guo}35_{, S. Gupta}119_{, P. Gutierrez}112_{, N.G. Gutierrez Ortiz}53_{, C. Gutschow}77_{, N. Guttman}154_,

C. Guyot137_{, C. Gwenlan}119_{, C.B. Gwilliam}73_{, A. Haas}109_{, C. Haber}15_{, H.K. Hadavand}8_{, N. Haddad}136e_,

P. Haefner21_{, S. Hageboeck}21_{, Z. Hajduk}39_{, H. Hakobyan}178_{, M. Haleem}42_{, D. Hall}119_{, G. Halladjian}89_,

K. Hamacher176_{, P. Hamal}114_{, K. Hamano}170_{, M. Hamer}54_{, A. Hamilton}146a_{, S. Hamilton}162_{, P.G. Hamnett}42_,

L. Han33b_{, K. Hanagaki}117_{, K. Hanawa}156_{, M. Hance}15_{, P. Hanke}58a_{, R. Hanna}137_{, J.R. Hansen}36_{, J.B. Hansen}36_,

J.D. Hansen36_{, P.H. Hansen}36_{, K. Hara}161_{, A.S. Hard}174_{, T. Harenberg}176_{, S. Harkusha}91_{, D. Harper}88_,

R.D. Harrington46_{, O.M. Harris}139_{, P.F. Harrison}171_{, F. Hartjes}106_{, S. Hasegawa}102_{, Y. Hasegawa}141_{, A Hasib}112_,

S. Hassani137_{, S. Haug}17_{, M. Hauschild}30_{, R. Hauser}89_{, M. Havranek}126_{, C.M. Hawkes}18_{, R.J. Hawkings}30_,

A.D. Hawkins80_{, T. Hayashi}161_{, D. Hayden}89_{, C.P. Hays}119_{, H.S. Hayward}73_{, S.J. Haywood}130_{, S.J. Head}18_,

T. Heck82_{, V. Hedberg}80_{, L. Heelan}8_{, S. Heim}121_{, T. Heim}176_{, B. Heinemann}15_{, L. Heinrich}109_{, S. Heisterkamp}36_,

J. Hejbal126_{, L. Helary}22_{, C. Heller}99_{, M. Heller}30_{, S. Hellman}147a,147b_{, D. Hellmich}21_{, C. Helsens}30_{, J. Henderson}119_,

R.C.W. Henderson71_{, C. Hengler}42_{, A. Henrichs}177_{, A.M. Henriques Correia}30_{, S. Henrot-Versille}116_{, C. Hensel}54_,

G.H. Herbert16, Y. Hern´andez Jim´enez168, R. Herrberg-Schubert16, G. Herten48, R. Hertenberger99, L. Hervas30,

G.G. Hesketh77_{, N.P. Hessey}106_{, R. Hickling}75_{, E. Hig´on-Rodriguez}168_{, E. Hill}170_{, J.C. Hill}28_{, K.H. Hiller}42_,

S. Hillert21_{, S.J. Hillier}18_{, I. Hinchliffe}15_{, E. Hines}121_{, M. Hirose}117_{, D. Hirschbuehl}176_{, J. Hobbs}149_{, N. Hod}106_,

M.C. Hodgkinson140_{, P. Hodgson}140_{, A. Hoecker}30_{, M.R. Hoeferkamp}104_{, J. Hoffman}40_{, D. Hoffmann}84_,

J.I. Hofmann58a_{, M. Hohlfeld}82_{, T.R. Holmes}15_{, T.M. Hong}121_{, L. Hooft van Huysduynen}109_{, J-Y. Hostachy}55_,

S. Hou152_{, A. Hoummada}136a_{, J. Howard}119_{, J. Howarth}42_{, M. Hrabovsky}114_{, I. Hristova}16_{, J. Hrivnac}116_,

T. Hryn’ova5_{, P.J. Hsu}82_{, S.-C. Hsu}139_{, D. Hu}35_{, X. Hu}25_{, Y. Huang}42_{, Z. Hubacek}30_{, F. Hubaut}84_{, F. Huegging}21_,

J. Huston89_{, J. Huth}57_{, G. Iacobucci}49_{, G. Iakovidis}10_{, I. Ibragimov}142_{, L. Iconomidou-Fayard}116_{, J. Idarraga}116_,

E. Ideal177_{, P. Iengo}103a_{, O. Igonkina}106_{, T. Iizawa}172_{, Y. Ikegami}65_{, K. Ikematsu}142_{, M. Ikeno}65_{, D. Iliadis}155_,

N. Ilic159_{, Y. Inamaru}66_{, T. Ince}100_{, P. Ioannou}9_{, M. Iodice}135a_{, K. Iordanidou}9_{, V. Ippolito}57_{, A. Irles Quiles}168_,

C. Isaksson167, M. Ishino67, M. Ishitsuka158, R. Ishmukhametov110, C. Issever119, S. Istin19a, J.M. Iturbe Ponce83,

J. Ivarsson80_{, A.V. Ivashin}129_{, W. Iwanski}39_{, H. Iwasaki}65_{, J.M. Izen}41_{, V. Izzo}103a_{, B. Jackson}121_{, J.N. Jackson}73_,

M. Jackson73_{, P. Jackson}1_{, M.R. Jaekel}30_{, V. Jain}2_{, K. Jakobs}48_{, S. Jakobsen}30_{, T. Jakoubek}126_{, J. Jakubek}127_,

D.O. Jamin152_{, D.K. Jana}78_{, E. Jansen}77_{, H. Jansen}30_{, J. Janssen}21_{, M. Janus}171_{, G. Jarlskog}80_{, N. Javadov}64,b_,

T. Jav˚urek48_{, L. Jeanty}15_{, G.-Y. Jeng}151_{, D. Jennens}87_{, P. Jenni}48,n_{, J. Jentzsch}43_{, C. Jeske}171_{, S. J´ez´equel}5_,

H. Ji174_{, W. Ji}82_{, J. Jia}149_{, Y. Jiang}33b_{, M. Jimenez Belenguer}42_{, S. Jin}33a_{, A. Jinaru}26a_{, O. Jinnouchi}158_,

M.D. Joergensen36_{, K.E. Johansson}147a_{, P. Johansson}140_{, K.A. Johns}7_{, K. Jon-And}147a,147b_{, G. Jones}171_,

R.W.L. Jones71_{, T.J. Jones}73_{, J. Jongmanns}58a_{, P.M. Jorge}125a,125b_{, K.D. Joshi}83_{, J. Jovicevic}148_{, X. Ju}174_,

C.A. Jung43_{, R.M. Jungst}30_{, P. Jussel}61_{, A. Juste Rozas}12,m_{, M. Kaci}168_{, A. Kaczmarska}39_{, M. Kado}116_,

H. Kagan110_{, M. Kagan}144_{, E. Kajomovitz}45_{, C.W. Kalderon}119_{, S. Kama}40_{, N. Kanaya}156_{, M. Kaneda}30_,

S. Kaneti28_{, T. Kanno}158_{, V.A. Kantserov}97_{, J. Kanzaki}65_{, B. Kaplan}109_{, A. Kapliy}31_{, D. Kar}53_{, K. Karakostas}10_,

N. Karastathis10_{, M. Karnevskiy}82_{, S.N. Karpov}64_{, K. Karthik}109_{, V. Kartvelishvili}71_{, A.N. Karyukhin}129_,

L. Kashif174_{, G. Kasieczka}58b_{, R.D. Kass}110_{, A. Kastanas}14_{, Y. Kataoka}156_{, A. Katre}49_{, J. Katzy}42_{, V. Kaushik}7_,

K. Kawagoe69_{, T. Kawamoto}156_{, G. Kawamura}54_{, S. Kazama}156_{, V.F. Kazanin}108_{, M.Y. Kazarinov}64_{, R. Keeler}170_,

P.T. Keener121_{, R. Kehoe}40_{, M. Keil}54_{, J.S. Keller}42_{, J.J. Kempster}76_{, H. Keoshkerian}5_{, O. Kepka}126_,

B.P. Kerˇsevan74, S. Kersten176, K. Kessoku156, J. Keung159, F. Khalil-zada11, H. Khandanyan147a,147b,

A. Khanov113_{, A. Khodinov}97_{, A. Khomich}58a_{, T.J. Khoo}28_{, G. Khoriauli}21_{, A. Khoroshilov}176_{, V. Khovanskiy}96_,

E. Khramov64_{, J. Khubua}51b_{, H.Y. Kim}8_{, H. Kim}147a,147b_{, S.H. Kim}161_{, N. Kimura}172_{, O. Kind}16_{, B.T. King}73_,

M. King168_{, R.S.B. King}119_{, S.B. King}169_{, J. Kirk}130_{, A.E. Kiryunin}100_{, T. Kishimoto}66_{, D. Kisielewska}38a_,

F. Kiss48_{, T. Kitamura}66_{, T. Kittelmann}124_{, K. Kiuchi}161_{, E. Kladiva}145b_{, M. Klein}73_{, U. Klein}73_{, K. Kleinknecht}82_,

P. Klimek147a,147b_{, A. Klimentov}25_{, R. Klingenberg}43_{, J.A. Klinger}83_{, T. Klioutchnikova}30_{, P.F. Klok}105_,

E.-E. Kluge58a_{, P. Kluit}106_{, S. Kluth}100_{, E. Kneringer}61_{, E.B.F.G. Knoops}84_{, A. Knue}53_{, T. Kobayashi}156_,

M. Kobel44_{, M. Kocian}144_{, P. Kodys}128_{, P. Koevesarki}21_{, T. Koffas}29_{, E. Koffeman}106_{, L.A. Kogan}119_,

S. Kohlmann176_{, Z. Kohout}127_{, T. Kohriki}65_{, T. Koi}144_{, H. Kolanoski}16_{, I. Koletsou}5_{, J. Koll}89_{, A.A. Komar}95,∗_,

Y. Komori156_{, T. Kondo}65_{, N. Kondrashova}42_{, K. K¨oneke}48_{, A.C. K¨onig}105_{, S. K¨onig}82_{, T. Kono}65,o_,

R. Konoplich109,p_{, N. Konstantinidis}77_{, R. Kopeliansky}153_{, S. Koperny}38a_{, L. K¨opke}82_{, A.K. Kopp}48_{, K. Korcyl}39_,

K. Kordas155_{, A. Korn}77_{, A.A. Korol}108_{, I. Korolkov}12_{, E.V. Korolkova}140_{, V.A. Korotkov}129_{, O. Kortner}100_,

S. Kortner100_{, V.V. Kostyukhin}21_{, S. Kotov}100_{, V.M. Kotov}64_{, A. Kotwal}45_{, C. Kourkoumelis}9_{, V. Kouskoura}155_,

A. Koutsman160a_{, R. Kowalewski}170_{, T.Z. Kowalski}38a_{, W. Kozanecki}137_{, A.S. Kozhin}129_{, V. Kral}127_,

V.A. Kramarenko98_{, G. Kramberger}74_{, D. Krasnopevtsev}97_{, M.W. Krasny}79_{, A. Krasznahorkay}30_{, J.K. Kraus}21_,

A. Kravchenko25, S. Kreiss109, M. Kretz58c, J. Kretzschmar73, K. Kreutzfeldt52, P. Krieger159, K. Kroeninger54,

H. Kroha100_{, J. Kroll}121_{, J. Kroseberg}21_{, J. Krstic}13a_{, U. Kruchonak}64_{, H. Kr¨uger}21_{, T. Kruker}17_{, N. Krumnack}63_,

Z.V. Krumshteyn64_{, A. Kruse}174_{, M.C. Kruse}45_{, M. Kruskal}22_{, T. Kubota}87_{, S. Kuday}4a_{, S. Kuehn}48_{, A. Kugel}58c_,

A. Kuhl138_{, T. Kuhl}42_{, V. Kukhtin}64_{, Y. Kulchitsky}91_{, S. Kuleshov}32b_{, M. Kuna}133a,133b_{, J. Kunkle}121_{, A. Kupco}126_,

H. Kurashige66_{, Y.A. Kurochkin}91_{, R. Kurumida}66_{, V. Kus}126_{, E.S. Kuwertz}148_{, M. Kuze}158_{, J. Kvita}114_,

A. La Rosa49_{, L. La Rotonda}37a,37b_{, C. Lacasta}168_{, F. Lacava}133a,133b_{, J. Lacey}29_{, H. Lacker}16_{, D. Lacour}79_,

V.R. Lacuesta168_{, E. Ladygin}64_{, R. Lafaye}5_{, B. Laforge}79_{, T. Lagouri}177_{, S. Lai}48_{, H. Laier}58a_{, L. Lambourne}77_,

S. Lammers60_{, C.L. Lampen}7_{, W. Lampl}7_{, E. Lan¸con}137_{, U. Landgraf}48_{, M.P.J. Landon}75_{, V.S. Lang}58a_,

C. Lange42_{, A.J. Lankford}164_{, F. Lanni}25_{, K. Lantzsch}30_{, S. Laplace}79_{, C. Lapoire}21_{, J.F. Laporte}137_{, T. Lari}90a_,

M. Lassnig30_{, P. Laurelli}47_{, W. Lavrijsen}15_{, A.T. Law}138_{, P. Laycock}73_{, B.T. Le}55_{, O. Le Dortz}79_{, E. Le Guirriec}84_,

E. Le Menedeu12_{, T. LeCompte}6_{, F. Ledroit-Guillon}55_{, C.A. Lee}152_{, H. Lee}106_{, J.S.H. Lee}117_{, S.C. Lee}152_{, L. Lee}177_,

G. Lefebvre79_{, M. Lefebvre}170_{, F. Legger}99_{, C. Leggett}15_{, A. Lehan}73_{, M. Lehmacher}21_{, G. Lehmann Miotto}30_,

X. Lei7_{, W.A. Leight}29_{, A.G. Leister}177_{, M.A.L. Leite}24d_{, R. Leitner}128_{, D. Lellouch}173_{, B. Lemmer}54_,

K.J.C. Leney77_{, T. Lenz}106_{, G. Lenzen}176_{, B. Lenzi}30_{, R. Leone}7_{, K. Leonhardt}44_{, S. Leontsinis}10_{, C. Leroy}94_,

C.G. Lester28_{, C.M. Lester}121_{, M. Levchenko}122_{, J. Levˆeque}5_{, D. Levin}88_{, L.J. Levinson}173_{, M. Levy}18_{, A. Lewis}119_,

G.H. Lewis109, A.M. Leyko21, M. Leyton41, B. Li33b,q, B. Li84, H. Li149, H.L. Li31, L. Li45, L. Li33e, S. Li45,

Y. Li33c,r_{, Z. Liang}138_{, H. Liao}34_{, B. Liberti}134a_{, P. Lichard}30_{, K. Lie}166_{, J. Liebal}21_{, W. Liebig}14_{, C. Limbach}21_,

A. Limosani87_{, S.C. Lin}152,s_{, F. Linde}106_{, B.E. Lindquist}149_{, J.T. Linnemann}89_{, E. Lipeles}121_{, A. Lipniacka}14_,

M. Lisovyi42_{, T.M. Liss}166_{, D. Lissauer}25_{, A. Lister}169_{, A.M. Litke}138_{, B. Liu}152_{, D. Liu}152_{, J.B. Liu}33b_{, K. Liu}33b,t_,

L. Liu88_{, M. Liu}45_{, M. Liu}33b_{, Y. Liu}33b_{, M. Livan}120a,120b_{, S.S.A. Livermore}119_{, A. Lleres}55_{, J. Llorente Merino}81_,

S.L. Lloyd75_{, F. Lo Sterzo}152_{, E. Lobodzinska}42_{, P. Loch}7_{, W.S. Lockman}138_{, T. Loddenkoetter}21_{, F.K. Loebinger}83_,

A.E. Loevschall-Jensen36_{, A. Loginov}177_{, C.W. Loh}169_{, T. Lohse}16_{, K. Lohwasser}42_{, M. Lokajicek}126_,