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Published for SISSA by Springer

Received: April 20, 2012

Revised: June 10, 2012

Accepted: July 12, 2012

Published: August 3, 2012

Search for leptonic decays of W
′
bosons in pp

collisions at
√
s = 7TeV

The CMS collaboration

Abstract: A search for a new heavy gauge boson W
′

decaying to an electron or muon,

plus a low mass neutrino, is presented. This study uses data corresponding to an integrated

luminosity of 5.0 fb−1, collected using the CMS detector in pp collisions at a centre-of-mass

energy of 7 TeV at the LHC. Events containing a single electron or muon and missing trans-

verse momentum are analyzed. No significant excess of events above the standard model

expectation is found in the transverse mass distribution of the lepton-neutrino system, and

upper limits for cross sections above different transverse mass thresholds are presented.

Mass exclusion limits at 95% CL for a range of W
′

models are determined, including a

limit of 2.5 TeV for right-handed W
′

bosons with standard-model-like couplings and limits

of 2.43–2.63 TeV for left-handed W
′

bosons, taking into account their interference with the

standard model W boson. Exclusion limits have also been set on Kaluza-Klein WKK states

in the framework of split universal extra dimensions.

Keywords: Hadron-Hadron Scattering

Open Access, Copyright CERN,

for the benefit of the CMS collaboration

doi:10.1007/JHEP08(2012)023

http://dx.doi.org/10.1007/JHEP08(2012)023


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Contents

1 Introduction 1

2 Physics models 1

3 The CMS detector 3

4 Event selection 4

5 Signal and background simulation 5

6 Systematic uncertainties 7

7 Results and limits 8

8 Summary 13

The CMS collaboration 16

1 Introduction

This Letter describes a search for a new heavy gauge boson W
′
, using proton-proton

collision data collected during 2011 using the Compact Muon Solenoid (CMS) detector [1]

at the Large Hadron Collider (LHC) at a centre-of-mass energy of 7 TeV. The dataset

corresponds to an integrated luminosity of 5.0 ± 0.1 fb−1 [2]. The search attempts to

identify an excess of events with a charged lepton (an electron or muon) and a neutrino

in the final state, and an interpretation of the results is provided in the context of several

theoretical models.

2 Physics models

New heavy gauge bosons such as the W
′

and Z′ are predicted by various extensions of

the standard model (SM). In the sequential standard model (SSM) [3], the W
′

boson is

considered to be a left-handed heavy analogue of the W. It is assumed to be a narrow

s-channel resonance with decay modes and branching fractions similar to those of the W,

with the addition of the tb channel that becomes relevant for W
′

masses above 180 GeV.

Interference between the W
′

and W is assumed to be negligible. If the W
′

is heavy enough

to decay to top and bottom quarks, the predicted branching fraction is about 8.5% for each

of the two leptonic channels studied in the present analysis. Under these assumptions, the

width of a 1 TeV W
′

is about 33 GeV. Decays of the W
′

into WZ dibosons are usually

suppressed in this model.

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The assumptions of the SSM were used in previous searches in leptonic channels at

the Tevatron [4, 5] and the LHC [6–9]. The signature of a charged high-momentum lepton

and a neutrino would also be observed in the decays of a right-handed W′
R, predicted by

left-right symmetric models [10–13]. This particle is typically predicted to decay to a heavy

right-handed neutrino [14–16].

However, the mass of the right-handed neutrino is not constrained, and it could be

light as long as it does not couple to SM weak bosons. This would result in the same W′
R

decay signature as for the W.

If the W
′

is right-handed it will not interfere with the W. However, if it is left-handed

(W′
L), interference with the W is expected expected [17–19]. Constructive (destructive)

interference occurs in the mass range between W and W
′

if the coupling of the W
′

boson

to quarks and leptons has opposite sign to (same sign as) the coupling of the W boson

to left-handed fermions (gL). While constructive interference increases the W
′

production

cross section, and therefore allows experimental sensitivity at higher masses, destructive

interference would yield a lower cross section, rendering previously published LHC mass

exclusion limits [7, 9] slightly optimistic. Interference has previously been considered in

searches for the decay to top and bottom quarks [19, 20], but never for leptonic decays.

Figure 1 shows the transverse mass distribution for a W
′

of 2.5 TeV mass for the cases

of constructive, destructive and non-interference, along with the background due to the

SM W. In the absence of interference the cross sections and transverse mass spectrum

of left- and right-handed W
′

are identical. The W
′

manifests itself as a Jacobian peak

with its width almost independent of the presence and type of interference. However, the

intermediate region around MT ∼ 1 TeV shows a clear variation of the shape. Destructive

interference of a W′
L boson with mass ≥ 2 TeV modulates the W transverse mass tail,

resulting in a faster fall-off. The modulation strength and the resulting effect on the cross

section both increase with the W
′

mass and width. Given sufficient detector resolution,

the constructive and destructive interference scenarios may be distinguishable.

The leptonic final states under study may also be interpreted in the framework of

universal extra dimensions (UED) with bulk mass fermions, or split-UED [21, 22]. This is

a model based on an extended space-time with an additional compact fifth dimension of

radius R. All SM fermions and gauge bosons have Kaluza-Klein (KK) states, for instance

Wn
KK, where n denotes the n-th KK excitation mode, and

m2
Wn

KK
≡ m2

n = m2
W +

( n
R

)2
, (2.1)

gn = gSMFn(πµR), (2.2)

Fn(x) =


0 if n = 2m+ 1

x2[−1 + (−1)me2x](cothx− 1)√
2(1 + δm0)(x2 +m2π2/4)

if n = 2m.
(2.3)

Here µ is the bulk mass parameter in five dimensions of the fermion field, with [1/R, µ]

defining the UED parameter space. The coupling of the Wn
KK to SM fermions is denoted gn

and defined as a modification of the SM coupling gSM of the W. The function F2m(x) tends

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T
/d

M
σ

di
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1

No Interference MadGraph
Destructive Interference MadGraph

Constructive Interference MadGraph

Standard Model (No W') MadGraph
Destructive Interference CompHep

m(W') = 2500 GeV

CMS Simulation

Figure 1. MadGraph and CompHEP predictions of the transverse mass distribution for the SM

W background and various W
′

models for m(W
′
)=2.5 TeV. In the absence of interference, W′R and

W′L cross sections are identical. A W′L could experience constructive or destructive interference

with the SM W, yielding the shown modulation of the MT spectrum.

to approach (−1)m
√

2 as x → ∞. In minimal UED models, the parameter µ is assumed

to be zero [23]. Following [21, 22], we assume a non-zero value for µ, thus increasing the

cross sections sufficiently to allow observation by LHC experiments.

KK-odd modes of Wn
KK do not couple to SM fermions, owing to KK-parity conserva-

tion. Moreover, there is no expected sensitivity for n ≥ 4 modes at the LHC centre-of-mass

energy and luminosity used in this analysis. W2
KK is therefore the only mode considered.

Under this assumption, the decay to leptons is kinematically identical to the sequential

SM-like W
′

decay, and the observed limits obtained from the W
′ → eν and W

′ → µν

searches can directly be reinterpreted in terms of the Wn
KK mass considering the different

widths. The width of a Wn
KK is F2

n times the SSM-like W
′

width:

ΓWn
KK

= F2
n

4

3

mWn
KK

mW
ΓW. (2.4)

3 The CMS detector

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 field volume are the silicon pixel

and strip tracker, the crystal electromagnetic calorimeter and the brass/scintillator hadron

calorimeter. The electromagnetic calorimeter consists of nearly 76 000 lead tungstate crys-

tals. The energy resolution for electrons with the very high transverse momentum used in

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this analysis, which are predominantly in the central pseudorapidity region, is about 1%.

In the forward region the resolution is about 2%. Muons are measured in gas-ionization de-

tectors embedded in the steel return yoke. Central and forward regions are instrumented

with four muon stations combining high precision tracking detectors (drift tubes in the

central region and forward cathode strip chambers) with resistive plate chambers, which

contribute to the trigger as well as the track measurement. The muon transverse mo-

mentum, pµT, is determined from the curvature of its track, measured as it traverses the

magnetized return yoke. Each muon track is matched to a track measured in the silicon

tracker, resulting in a muon pT resolution of 1 to 10% for pT of up to 1 TeV. CMS uses

a two-level trigger system comprising custom hardware processors and a High-Level Trig-

ger processor farm. Together, these systems select around 300 Hz of the most interesting

recorded bunch-crossings for permanent storage. A detailed description of CMS can be

found in ref. [1].

A cylindrical coordinate system about the beam axis is used, in which the polar angle

θ is measured with respect to the counterclockwise beam direction and the azimuthal angle

φ is measured in the xy plane, where the x axis points towards the center of the LHC ring.

The quantity η is the pseudo-rapidity, defined as η = − ln[tan θ/2].

4 Event selection

Candidate events with at least one high-transverse-momentum (pT) lepton were selected

using single-muon and single-electron triggers. The trigger thresholds were raised as the

LHC luminosity increased during the data-taking period, the highest values being pT >

80 GeV for electrons and pT > 40 GeV for muons. Offline, electrons and muons were

required to have pT at least 5 GeV higher than the online threshold, which does not impair

the search in the high mass region.

Muons were reconstructed by combining tracks from the inner tracker and the outer

muon system. Well-reconstructed muons were selected by requiring at least one pixel hit,

hits in eight tracker layers and segments in two muon stations. Since the segments have

multiple hits and are typically found in different muon detectors separated by thick layers

of iron, the latter requirement significantly reduces the amount of hadronic punch-through.

The transverse impact parameter |d0| of a muon track with respect to the beam spot is

required to be less than 0.02 cm, in order to reduce the cosmic ray muon background.

Furthermore, the muon is required to be isolated within a ∆R ≡
√

(∆φ)2 + (∆η)2 < 0.3

cone around its direction. Muon isolation requires that the scalar sum of the transverse

momenta of all tracks originating at the interaction vertex, excluding the muon, is less

than 15% of its pT. An additional requirement is that there be no second muon in the

event with pT > 25 GeV to reduce the Z, Drell-Yan and cosmic ray muon backgrounds.

Electrons were reconstructed as isolated objects in the electromagnetic calorimeter,

with additional requirements on the shower shape and the ratio of hadronic to electro-

magnetic deposited energies. The electrons were required to have at least one inner hit,

a transverse energy greater than 85 GeV, and required to be isolated in a cone of radius

∆R < 0.3 around the electron candidate direction, both in the tracker and in the calorime-

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ter. In the tracker, the sum of the pT of the tracks, excluding tracks within an inner cone

of 0.04, was required to be less than 5 GeV. For the isolation using calorimeters, the total

transverse energy in the barrel, excluding deposits associated to the electron, was required

to be less than 0.03 ·peleT +2.0 GeV. The isolation requirements were modified as luminosity

increased, owing to the increase in the typical number of additional pp interactions (‘pile-

up’) per LHC bunch crossing. These selections are designed to ensure high efficiency for

electrons and a high rejection of misreconstructed electrons from multi-jet backgrounds.

The main observable in this search is the transverse mass MT of the lepton-Emiss
T

system, calculated as

MT ≡
√

2 · p`T · Emiss
T · (1− cos ∆φ`,ν) (4.1)

where ∆φ`,ν is the azimuthal opening angle between the charged lepton’s transverse mo-

mentum (p`T) and missing transverse energy (Emiss
T ) direction. The neutrino is not detected

directly, but gives rise to experimentally observed Emiss
T . This quantity was determined

using a particle-flow technique [24], an algorithm designed to reconstruct a complete list

of distinct particles using all the subcomponents of the CMS detector. Muons, electrons,

photons, and charged and neutral hadrons were all reconstructed individually. The Emiss
T

for each event was then calculated as the vector opposing the total transverse momentum

of all reconstructed particles in each event.

In W
′
decays, the lepton and Emiss

T are expected to be almost back-to-back in the trans-

verse plane, and balanced in transverse energy. Candidate events were therefore selected

through a requirement on the ratio of the lepton pT and the Emiss
T , 0.4 < pT/E

miss
T < 1.5.

A requirement was also imposed on the angular difference in the transverse plane of the

lepton and Emiss
T direction, ∆φ`,ν > 0.8 × π. No selection is made on jets. After these

selections, the average W
′

signal efficiency for masses up to 2.5 TeV in simulated events

was found to be around 80% in both channels, including the roughly 90% geometrical ac-

ceptance corresponding to a requirement of |ηµ| < 2.1 for muons, and with |ηe| < 1.442 or

1.56 < |ηe| < 2.5 for electrons. The transverse mass distributions after these selections are

shown in figure 2.

5 Signal and background simulation

Several large samples of simulated events were used to evaluate signal and background

efficiencies. The generated events were processed through a full simulation of the CMS

detector based on Geant4 [25, 26], a trigger emulation, and the event reconstruction chain.

The event samples for the W′
R signal were produced separately from the SM W sample,

using the pythia 6.4.9 generator [27]. This is consistent with the case of non-interference

assumed for the previous ATLAS and CMS studies. In order to include interference of

W′
L and W in this analysis, a model of a single new heavy vector boson W

′
with a SM-

like left-handed coupling strength |g′L| ≈ 0.65 was implemented in the MadGraph event

generator [28]. This model includes spin correlations as well as finite-width effects. For

such a left-handed scenario with interference, the generation of samples is technically more

challenging. Since the scattering amplitude responsible for the `ν final state is the sum of

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ντ →W 

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Top

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Multijet

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Data

=2.3 TeV)
W'

W' (m

Background Prediction

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 = 7 TeVs

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ντ →W 

Dibosons

Top

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Multijet

Data

=2.3 TeV)
W'

W' (m

Background Prediction

CMS
-1 L dt = 5.0 fb∫

 = 7 TeVs

ν µ →W' 

o
ve

rf
lo

w
 b

in

Figure 2. Observed transverse mass distributions for the electron (left) and muon (right) channels.

Simulated signal distributions for a (left- or right-handed) W
′

without interference of 2.3 TeV mass

are also shown, including detector resolution effects. The simulated background labelled as ‘diboson’

includes WW, ZZ and WZ contributions. The top background prediction includes single top and

top pair production. The total background prediction from a fit to the simulated transverse mass

spectrum in each channel is shown by the dashed line.

W′
L and SM W boson terms, both contributions have to be generated simultaneously. A

threshold in MT was applied to suppress the dominant W contribution around the W-mass,

where interference effects are negligible for the W′
L masses considered in this search. The

simulation uses MadGraph 4.5.1, matched to pythia for showering and hadronisation.

For the hadronisation model, the pythia Tune Z2 was used for both the W′
R and W′

L

simulations. Both generators simulate at leading order (LO) and use the CTEQ6L1 parton

distribution functions (PDF) [29]. Mass-dependent K-factors, varying from 1.14 to 1.36,

for the next-to-next-to-leading order (NNLO) correction were calculated with fewz [30,

31]. The resulting NNLO W
′ → `ν production cross section times branching fraction

ranged from 17.7 pb (for mW′ = 0.5 TeV) to 0.71 fb (for mW′ = 3 TeV) for a W
′

without

interference (see table 1 for cross sections). Efficiencies and detector acceptance are then

taken into account for estimating the expected number of signal events. The acceptance

is nearly maximal since the decay products of such heavy particles tend to populate low

pseudorapidities. Efficiencies are high because the selections have been optimised. Detailed

numbers for both quantities are given in section 4. The Tevatron W′
L → tb search used the

CompHEP generator [32, 33] which has the case of destructive interference implemented.

The agreement between the model implementations in CompHEP and MadGraph is

demonstrated for the case of destructive interference in figure 1.

The primary source of background is the off-peak, high transverse mass tail of the

standard model W → `ν decays. Other important backgrounds arise from QCD multijet,

tt, and Drell-Yan events. Dibosons (WW, WZ, ZZ) decaying to electrons, muons, or taus

were also considered. The event samples for the electroweak background processes W → `ν

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and Z→ `` (` = e, µ, τ) were produced using pythia. NNLO cross sections were accounted

for via a single K-factor of 1.32 for the W, and mass-dependent K-factors, ranging from

1.28 to 1.23, for the Z. The pythia generator was also used for QCD multijet events.

The tt events were generated with MadGraph in combination with pythia, and the

newly-calculated NNLL (next-to-leading-order including the leading logarithms of NNLO)

cross section was applied [34]. All other event samples were normalised to the integrated

luminosity of the recorded data, using calculated NNLO cross sections. The only exceptions

were the diboson and QCD samples, for which the NLO and LO cross sections were used

respectively. We note that multijet background is largely suppressed by the event selection

requirements. The simulation of pile-up is included in all event samples by superimposing

minimum bias interactions onto the main background processes.

In order to provide a background estimate independent of any interference effects in

the W transverse mass tail, the shape of the background was determined from simulation.

The full transverse mass spectrum was modelled by a function optimised to best describe

the spectrum in either channel up to very high masses. This function, of the form

f(MT) =
a

(MT + b)c
(5.1)

was fitted to the simulation and then normalised to data in the region 200 GeV <

MT < 500 GeV, and used to estimate the expected number of SM background events for

all transverse mass bins (shown as the dashed lines in figure 2). A cross check under the

assumption of no interference was done by fitting the MT distribution in data confirming

the simulation. To determine the uncertainty introduced by this method, in addition to

statistical errors on the fit parameters, two alternative functions were fitted:

f(MT) =
a

(M2
T + b ·MT + c)d

(5.2)

f(MT) =
a(1 +MT)b

(M c+d·lnMT
T )

(5.3)

The largest difference in the background prediction with respect to the original fit was taken

as a systematic uncertainty. For MT larger than 1.4 TeV, this corresponds to an additional

uncertainty of 0.14 events with a background expectation of 0.98 events in the muon channel

and 0.26 events with a background expectation of 1.28 events in the electron channel.

6 Systematic uncertainties

The expected number of potential signal and background events was evaluated from simu-

lation. In addition to uncertainties due to the fit procedure for the background, systematic

uncertainties due to imperfections in the description of the detector performance were in-

cluded. Uncertainties due to the lepton energy or momentum resolution and scale, ranging

between 0.4% and 10% [6, 7] were applied to the transverse mass spectrum. Uncertainties

due to momentum scale were evaluated using detailed studies of the Z → µµ shape and

high pT muons. The muon pT resolution has been previously determined with cosmic ray

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muons to be within 10% for high momentum tracks [35]. In order to estimate the un-

certainty on the number of expected events, the muon pT spectrum was distorted (scaled

and smeared) according to the values extracted from comparisons with data. The missing

transverse energy was adjusted accordingly, and finally a distorted transverse mass spec-

trum was obtained and observed to vary by ∼1%. The electron energy scale uncertainty

was around 1% in the ECAL barrel and 3% in the endcaps. Its impact on the number of

signal events above the threshold of MT > 600 GeV was ascertained to be less than 1% for

all W
′

masses. We assume an uncertainty of 10% on the hadronic component of the Emiss
T

resolution (that is, excluding the lepton), and the x and y components of the reconstructed

Emiss
T in the simulation were smeared accordingly. The impact on the number of signal

events was found to be around 2%.

Effects caused by pile-up were modeled by adding to the generated events multiple in-

teractions with a multiplicity distribution matched to the luminosity profile of the collision

data. The resulting impact on the signal was studied by varying the mean of the distri-

bution of pile-up interactions by 8%, yielding a variation of the signal efficiency of ∼2%.

Following the recommendations of the PDF4LHC group [36], the signal event samples for

W′
R generated with pythia were reweighted using the LHAPDF package [37]. PDF and

αs variations of the MSTW2008 [38], CTEQ6.6 [39] and NNPDF2.0 [40] PDF sets were

taken into account and the impact on the signal cross sections was estimated.

7 Results and limits

A W
′ → eν or W

′ → µν signal is expected to manifest itself as an excess over the SM

expectation in the tail of the MT distribution. No significant excess has been observed in

the data.

For W
′

masses well below the centre-of-mass energy of
√
s = 7 TeV the signal events

are expected to lie in the Jacobian peak corresponding to the W
′

mass. For masses above

2.3 TeV, the reduced phase space results in many events below the Jacobian peak, and the

acceptance for the Mmin
T cut drops from about 40% for intermediate masses to 14% at very

high W
′

masses. The expected signal yields given in table 1 for a range of W′
R masses are

largely unaffected when introducing interference effects, owing to the high MT cut corre-

sponding to the optimum search window, which naturally lies around the Jacobian peak.

We set upper limits on the production cross section times the branching fraction

σW′
R
× B(W′

R → `ν), with ` = e or µ. The observed highest transverse mass events had

MT = 1.6± 0.1 TeV in the electron channel, and MT = 2.4± 0.1 TeV in the muon channel.

For MT > 1.6 TeV, the background expectation from the fit to simulation is less than one

event in each channel. Cross-section limits were derived using a Bayesian method [41] with

a uniform prior probability distribution for the signal cross section. The number of data

events above an optimised transverse mass threshold Mmin
T was compared to the expected

number of signal and background events. Systematic uncertainties on the signal and back-

ground yield were included via nuisance parameters with a log-normal prior distribution.

The Mmin
T threshold was optimised for the best expected exclusion limit, a procedure used

in previous analyses [7] which is also appropriate for establishing a W
′
discovery. The Mmin

T

threshold defining the search window increases with W
′

mass up to masses around 2.5 TeV,

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W
′

mass Mmin
T Nsig Nbkg Nobs σtheory Exp. Limit Obs. Limit

( GeV) ( GeV) (Events) (Events) (Events) (fb) (fb) (fb)

Electron channel

500 350 44000 ± 4200 830 ± 85 850 17723 64.15 70.18

700 550 9600 ± 1500 114 ± 15 128 4514 16.94 22.48

900 700 3160 ± 460 37.4 ± 5.7 41 1470 8.38 9.61

1000 800 1730 ± 280 20.0 ± 3.8 22 886 6.77 7.55

1400 1050 294 ± 36 5.4 ± 1.6 6 144 3.56 3.77

1600 1150 128 ± 13 3.4 ± 1.1 5 63.3 3.02 3.80

1800 1200 63.9 ± 5.5 2.79 ± 0.99 3 28.5 2.53 2.57

2100 1350 18.7 ± 1.5 1.55 ± 0.64 2 9.37 2.38 2.61

2400 1450 5.47 ± 0.39 1.08 ± 0.49 2 3.40 2.69 3.39

2700 1450 1.75 ± 0.13 1.08 ± 0.49 2 1.43 3.54 4.46

3000 1400 0.59 ± 0.05 1.29 ± 0.56 2 0.71 5.45 6.42

Muon channel

500 350 41000 ± 3200 749 ± 47 732 17723 44.65 39.13

700 550 8700 ± 1000 102 ± 10 100 4514 15.42 14.28

900 700 2920 ± 370 32.6 ± 5.0 36 1470 8.24 9.51

1000 750 1840 ± 150 23.3 ± 4.2 26 886 6.62 7.57

1400 1000 313 ± 25 5.6 ± 1.9 6 144 3.37 3.47

1600 1100 136.3 ± 9.2 3.4 ± 1.4 4 63.3 2.83 3.04

1800 1250 56.5 ± 3.7 1.78 ± 0.86 3 28.5 2.48 3.18

2100 1300 18.5 ± 0.9 1.45 ± 0.75 2 9.37 2.35 2.65

2400 1400 5.54 ± 0.26 0.98 ± 0.56 2 3.40 2.59 3.37

2700 1450 1.68 ± 0.08 0.81 ± 0.49 2 1.43 3.45 4.77

3000 1400 0.58 ± 0.03 0.98 ± 0.56 2 0.71 5.17 6.73

Table 1. Mmin
T requirement for different W′R masses, expected number of signal and background

events, number of observed events, theoretical cross section and upper limits on σ(W′R)×B(W′R →
`ν), with ` = e, µ.

following the Jacobian peak. For larger masses, cross sections become so small that fewer

than two events are expected in the recorded data. These events are likely to have lower

transverse mass because the production is shifted to the off-peak region, as mentioned

above. Both these effects serve to lower the Mmin
T threshold of the search window for very

heavy W
′

bosons. The expected number of signal and background events listed separately

for the two channels are summarized in table 1. A common theoretical NNLO cross section

is assumed.

The expected and observed upper limits for both channels and their combination, in the

right-handed scenario without interference, are shown in figure 3. Using the central value of

the theoretical cross section times the branching fraction, we exclude at 95% confidence level

(CL) the existence of a W′
R with SM-like couplings of masses less than 2.5 TeV (compared

with an expected limit of 2.6 TeV). Note that the background uncertainty has a negligible

impact on the lower limits on W
′

mass, owing to the lack of observed events in the tail of

the MT distribution.

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W' mass [GeV]
500 1000 1500 2000 2500 3000

) 
[fb

]
ν

 +
 

µ
  e

 / 
→

 B
R

(W
' 

.  σ

1

10

210

310

410

CMS
 = 7 TeVs

-1 L dt = 5.0 fb∫

95% Observed Limit (Electron) 

95% Observed Limit (Muon) 

95% Observed (Combined)

95% Expected (Combined)

Theoretical Cross Section SSM W' with K-factor

Theoretical Cross Section SSM W' without K-factor

 = 10 TeV)µ (KKTheoretical Cross Section for W

 = 0.05 TeV)µ (KKTheoretical Cross Section for W

Figure 3. Upper limits on σ(W′R) × B(W′R → `ν), with ` = e, µ, and their combination at

95% confidence level. The one (two) sigma uncertainty bands are shown in green (yellow). The

theoretical cross section, with PDF uncertainties, is displayed with and without a mass-dependent

NNLO K-factor for the right-handed model without interference. The theoretical cross sections for

Kaluza-Klein W2
KK with µ=0.05 TeV and µ=10 TeV are also shown.

A similar search procedure was performed including the effect of interference. The

theoretical cross sections are approximately 10–30% lower (higher) for destructive (con-

structive) interference when integrating over the transverse mass spectrum above 500 GeV

and hence influence the resulting mass limits [17]. Optimising for the best expected cross

section limit resulted in very similar search windows at high MT, yielding lower limits on

the W′
L mass of 2.63 (2.43) TeV for constructive (destructive) interference, based on the

same MadGraph cross sections and K-factors as the ones used in figure 3. We note that

the interference affects mainly the medium MT and hardly the Jacobian peak region, with

the latter being used to set the limits. The limits shown do not take into account higher

order electroweak corrections at high mass, which can be sizable. The effect of these miss-

ing corrections would be a reduction of the size of interference effects, leading to limits that

are closer to the ones quoted for the no-interference case.

In addition to the model dependent results on W
′
production, upper limits for the cross

section of beyond-the-SM production of charged lepton-neutrino events are given in table 2

and figure 4. The results are presented as a function of the transverse mass threshold,

Mmin
T , and listed separately for the electron and the muon channels, and their combina-

tion. The only assumptions made here are that we are searching for a narrow s-channel

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Electron channel Muon channel Combined channels

Mmin
T Events Limit (fb) Events Limit (fb) Limit (fb)

( GeV) Nbkg Nobs Exp. Obs. Nbkg Nobs Exp. Obs. Exp. Obs.

500 175 ± 22 192 10.14 13.85 158 ± 14 141 8.20 6.13 6.86 6.04

600 77 ± 10 83 5.99 7.13 67.9 ± 8.1 62 5.12 4.46 4.01 3.95

700 37.4 ± 5.7 41 3.80 4.57 32.6 ± 5.0 36 3.60 4.41 2.65 3.31

800 20.0 ± 3.8 22 3.03 3.24 17.0 ± 3.6 16 2.95 2.54 1.94 1.99

900 11.4 ± 2.6 12 2.10 2.30 9.5 ± 2.6 11 2.01 2.46 1.46 1.68

1000 6.8 ± 1.8 8 1.79 2.02 5.6 ± 1.9 6 1.57 1.80 1.11 1.32

1100 4.3 ± 1.3 6 1.40 1.88 3.4 ± 1.4 4 1.32 1.56 0.94 1.19

1200 2.79 ± 0.98 3 1.32 1.32 2.2 ± 1.0 3 1.18 1.45 0.78 0.92

1300 1.87 ± 0.74 2 1.15 1.15 1.45 ± 0.75 2 0.97 1.26 0.69 0.77

1400 1.29 ± 0.56 2 0.94 1.22 0.98 ± 0.56 2 1.00 1.32 0.59 0.85

1500 0.91 ± 0.43 1 0.97 0.97 0.68 ± 0.43 2 0.72 1.37 0.53 0.76

Table 2. Excluded cross sections times branching fraction in the search window (MT > Mmin
T ) in

the electron and muon channels individually, along with their combination. The number of expected

background events was taken from simulation. The expected and observed cross section limits are

given for each search window.

 [GeV]min
TM

600 800 1000 1200 1400

E
xc

lu
de

d 
B

S
M

 c
ro

ss
 s

ec
tio

n 
x 

B
R

 [f
b]

1

10

CMS

 = 7 TeVs
-1 L dt = 5.0 fb∫

ν l →W' 

95% Observed Limit (Electron)

95% Observed Limit (Muon)

95% Observed (Combined)

95% Expected (Combined)

 (Combined)σ1±Expected 

 (Combined)σ2±Expected 

Figure 4. 95% confidence level upper limits on the cross section times branching fraction for

physics beyond the SM (labelled BSM) for the charged lepton-neutrino production with transverse

masses exceeding Mmin
T . The results for the electron, the muon channel, as well as for both channels

combined are presented. The one (two) sigma uncertainty bands are shown in green (yellow).

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1/R [TeV]
0 0.5 1 1.5 2

 [T
eV

]
µ

-110

1

10

Excluded

Electron
channel

Muon
channel

Combined
channels

CMS

 = 7 TeVs

-1
 L dt = 5.0 fb∫

Figure 5. 95% confidence limits on the split-UED parameters µ and R derived from the W
′

mass

limits taking into account the corresponding width of the W2
KK. The colored areas correspond to

the W2
KK exclusion regions with the same final state as the SM-like W

′
. Results are shown for the

electron and muon channels, as well as for both channels combined. The W2
KK is the lowest state

that can couple to SM fermions. Since it has even parity it can be produced singly.

produced resonance, using the detector acceptance and selection efficiency outlined in sec-

tion 4. Note that the Mmin
T threshold is on an experimentally-measured quantity affected

by detector resolution.

These exclusion limits on the cross-section can be translated to excluded W
′

masses

within the context of a given model, such as constructive or destructive W′
L, W′

R or some-

thing else.

The observed limits illustrated in figure 3 can be reinterpreted in terms of the W2
KK

mass, as shown in the same figure for values of the bulk mass parameters µ = 0.05 TeV

and µ = 10 TeV. For these parameters the second Kaluza-Klein excitation W2
KK has been

excluded for masses below 1.4 TeV (µ = 0.05 TeV) or 2.9 TeV (µ = 10 TeV), respectively.

The corresponding widths (eq. (2.4)) are taken into account in the calculation of the cross

section times the branching fraction of W2
KK. These lower limits on the mass can be

directly translated to bounds on the split-UED parameter space [1/R, µ] with µ being the

mass parameter for bulk fermions and R the radius of the extra dimension. The results

are displayed in figure 5, using the relations between R, µ and the W2
KK mass, and the

couplings to SM fermions described by expressions (2.1), (2.2) and (2.3). The split-UED

model also allows for W-W
′

interference. When the constructive case is considered, it has

a comparable sensitivity to the no-interference case.

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8 Summary

A search for an excess of events with a final state consisting of a charged lepton (electron or

muon) and significant missing transverse momentum has been performed, using 5.0 fb−1 of√
s = 7 TeV pp collision data. No significant excess over the SM expectation was observed

in the distribution of transverse mass. A W′
R in the SSM with a mass of less than 2.5 TeV

has been excluded at 95% CL. For the first time in such a study, W-W
′

interference effects

have been taken into account, and mass exclusion limits have been determined as 2.63 TeV

and 2.43 TeV for constructive and destructive interference respectively. These are the most

stringent limits yet published. An interpretation of the search results has also been made

in a specific framework of universal extra dimensions with bulk mass fermions. The second

Kaluza-Klein excitation W2
KK has been excluded for masses below 1.4 TeV, assuming a bulk

mass parameter µ of 0.05 TeV or masses below 2.9 TeV for µ=10 TeV.

Acknowledgments

We congratulate our colleagues in the CERN accelerator departments for the excellent

performance of the LHC machine. We thank the technical and administrative staff at

CERN and other CMS institutes, and acknowledge support from: FMSR (Austria); FNRS

and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria);

CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia);

RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC,

and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany);

GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); I± (Iran); SFI

(Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONA-

CYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and

NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan);

MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); MICINN and CPAN (Spain);

Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey);

STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from

the Marie-Curie programme and the European Research Council (European Union); the

Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Founda-

tion; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche

dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie

door Wetenschap en Technologie (IWT-Belgium); the Council of Science and Industrial

Research, India; and the HOMING PLUS programme of Foundation for Polish Science,

cofinanced from European Union, Regional Development Fund.

Open Access. This article is distributed under the terms of the Creative Commons

Attribution License which permits any use, distribution and reproduction in any medium,

provided the original author(s) and source are credited.

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http://inspirehep.net/search?p=find+J.Phys.,G37,075021


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The CMS collaboration

Yerevan Physics Institute, Yerevan, Armenia

S. Chatrchyan, V. Khachatryan, A.M. Sirunyan, A. Tumasyan

Institut für Hochenergiephysik der OeAW, Wien, Austria

W. Adam, T. Bergauer, M. Dragicevic, J. Erö, C. Fabjan, M. Friedl, R. Frühwirth,

V.M. Ghete, J. Hammer1, N. Hörmann, J. Hrubec, M. Jeitler, W. Kiesenhofer, V. Knünz,

M. Krammer, D. Liko, I. Mikulec, M. Pernicka†, B. Rahbaran, C. Rohringer, H. Rohringer,

R. Schöfbeck, J. Strauss, A. Taurok, F. Teischinger, P. Wagner, W. Waltenberger,

G. Walzel, E. Widl, C.-E. Wulz

National Centre for Particle and High Energy Physics, Minsk, Belarus

V. Mossolov, N. Shumeiko, J. Suarez Gonzalez

Universiteit Antwerpen, Antwerpen, Belgium

S. Bansal, K. Cerny, T. Cornelis, E.A. De Wolf, X. Janssen, S. Luyckx, T. Maes,

L. Mucibello, S. Ochesanu, B. Roland, R. Rougny, M. Selvaggi, H. Van Haevermaet, P. Van

Mechelen, N. Van Remortel, A. Van Spilbeeck

Vrije Universiteit Brussel, Brussel, Belgium

F. Blekman, S. Blyweert, J. D’Hondt, R. Gonzalez Suarez, A. Kalogeropoulos, M. Maes,

A. Olbrechts, W. Van Doninck, P. Van Mulders, G.P. Van Onsem, I. Villella

Université Libre de Bruxelles, Bruxelles, Belgium

O. Charaf, B. Clerbaux, G. De Lentdecker, V. Dero, A.P.R. Gay, T. Hreus, A. Léonard,

P.E. Marage, T. Reis, L. Thomas, C. Vander Velde, P. Vanlaer

Ghent University, Ghent, Belgium

V. Adler, K. Beernaert, A. Cimmino, S. Costantini, G. Garcia, M. Grunewald, B. Klein,

J. Lellouch, A. Marinov, J. Mccartin, A.A. Ocampo Rios, D. Ryckbosch, N. Strobbe,

F. Thyssen, M. Tytgat, L. Vanelderen, P. Verwilligen, S. Walsh, E. Yazgan, N. Zaganidis

Université Catholique de Louvain, Louvain-la-Neuve, Belgium

S. Basegmez, G. Bruno, L. Ceard, C. Delaere, T. du Pree, D. Favart, L. Forthomme,

A. Giammanco2, J. Hollar, V. Lemaitre, J. Liao, O. Militaru, C. Nuttens, D. Pagano,

A. Pin, K. Piotrzkowski, N. Schul

Université de Mons, Mons, Belgium

N. Beliy, T. Caebergs, E. Daubie, G.H. Hammad

Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil

G.A. Alves, M. Correa Martins Junior, D. De Jesus Damiao, T. Martins, M.E. Pol,

M.H.G. Souza

Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil

W.L. Aldá Júnior, W. Carvalho, A. Custódio, E.M. Da Costa, C. De Oliveira Martins,

S. Fonseca De Souza, D. Matos Figueiredo, L. Mundim, H. Nogima, V. Oguri, W.L. Prado

Da Silva, A. Santoro, S.M. Silva Do Amaral, L. Soares Jorge, A. Sznajder

– 16 –



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Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil

T.S. Anjos3, C.A. Bernardes3, F.A. Dias4, T.R. Fernandez Perez Tomei, E. M. Gregores3,

C. Lagana, F. Marinho, P.G. Mercadante3, S.F. Novaes, Sandra S. Padula

Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria

V. Genchev1, P. Iaydjiev1, S. Piperov, M. Rodozov, S. Stoykova, G. Sultanov, V. Tcholakov,

R. Trayanov, M. Vutova

University of Sofia, Sofia, Bulgaria

A. Dimitrov, R. Hadjiiska, V. Kozhuharov, L. Litov, B. Pavlov, P. Petkov

Institute of High Energy Physics, Beijing, China

J.G. Bian, G.M. Chen, H.S. Chen, C.H. Jiang, D. Liang, S. Liang, X. Meng, J. Tao,

J. Wang, J. Wang, X. Wang, Z. Wang, H. Xiao, M. Xu, J. Zang, Z. Zhang

State Key Lab. of Nucl. Phys. and Tech., Peking University, Beijing, China

C. Asawatangtrakuldee, Y. Ban, S. Guo, Y. Guo, W. Li, S. Liu, Y. Mao, S.J. Qian, H. Teng,

S. Wang, B. Zhu, W. Zou

Universidad de Los Andes, Bogota, Colombia

C. Avila, B. Gomez Moreno, A.F. Osorio Oliveros, J.C. Sanabria

Technical University of Split, Split, Croatia

N. Godinovic, D. Lelas, R. Plestina5, D. Polic, I. Puljak1

University of Split, Split, Croatia

Z. Antunovic, M. Dzelalija, M. Kovac

Institute Rudjer Boskovic, Zagreb, Croatia

V. Brigljevic, S. Duric, K. Kadija, J. Luetic, S. Morovic

University of Cyprus, Nicosia, Cyprus

A. Attikis, M. Galanti, G. Mavromanolakis, J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis

Charles University, Prague, Czech Republic

M. Finger, M. Finger Jr.

Academy of Scientific Research and Technology of the Arab Republic of Egypt,

Egyptian Network of High Energy Physics, Cairo, Egypt

Y. Assran6, S. Elgammal, A. Ellithi Kamel7, S. Khalil8, M.A. Mahmoud9, A. Radi8,10

National Institute of Chemical Physics and Biophysics, Tallinn, Estonia

M. Kadastik, M. Müntel, M. Raidal, L. Rebane, A. Tiko

Department of Physics, University of Helsinki, Helsinki, Finland

V. Azzolini, P. Eerola, G. Fedi, M. Voutilainen

Helsinki Institute of Physics, Helsinki, Finland

J. Härkönen, A. Heikkinen, V. Karimäki, R. Kinnunen, M.J. Kortelainen, T. Lampén,

K. Lassila-Perini, S. Lehti, T. Lindén, P. Luukka, T. Mäenpää, T. Peltola, E. Tuominen,

J. Tuominiemi, E. Tuovinen, D. Ungaro, L. Wendland

– 17 –



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Lappeenranta University of Technology, Lappeenranta, Finland

K. Banzuzi, A. Korpela, T. Tuuva

DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France

M. Besancon, S. Choudhury, M. Dejardin, D. Denegri, B. Fabbro, J.L. Faure, F. Ferri,

S. Ganjour, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, E. Locci,

J. Malcles, L. Millischer, A. Nayak, J. Rander, A. Rosowsky, I. Shreyber, M. Titov

Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau,

France

S. Baffioni, F. Beaudette, L. Benhabib, L. Bianchini, M. Bluj11, C. Broutin, P. Busson,

C. Charlot, N. Daci, T. Dahms, L. Dobrzynski, R. Granier de Cassagnac, M. Haguenauer,

P. Miné, C. Mironov, C. Ochando, P. Paganini, D. Sabes, R. Salerno, Y. Sirois, C. Veelken,

A. Zabi

Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Univer-

sité de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France

J.-L. Agram12, J. Andrea, D. Bloch, D. Bodin, J.-M. Brom, M. Cardaci, E.C. Chabert,

C. Collard, E. Conte12, F. Drouhin12, C. Ferro, J.-C. Fontaine12, D. Gelé, U. Goerlach,

P. Juillot, M. Karim12, A.-C. Le Bihan, P. Van Hove

Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique

des Particules (IN2P3), Villeurbanne, France

F. Fassi, D. Mercier

Université de Lyon, Université Claude Bernard Lyon 1, CNRS-IN2P3, Institut

de Physique Nucléaire de Lyon, Villeurbanne, France

S. Beauceron, N. Beaupere, O. Bondu, G. Boudoul, H. Brun, J. Chasserat, R. Chierici1,

D. Contardo, P. Depasse, H. El Mamouni, J. Fay, S. Gascon, M. Gouzevitch, B. Ille,

T. Kurca, M. Lethuillier, L. Mirabito, S. Perries, V. Sordini, S. Tosi, Y. Tschudi, P. Verdier,

S. Viret

Institute of High Energy Physics and Informatization, Tbilisi State University,

Tbilisi, Georgia

Z. Tsamalaidze13

RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany

G. Anagnostou, S. Beranek, M. Edelhoff, L. Feld, N. Heracleous, O. Hindrichs, R. Jussen,

K. Klein, J. Merz, A. Ostapchuk, A. Perieanu, F. Raupach, J. Sammet, S. Schael,

D. Sprenger, H. Weber, B. Wittmer, V. Zhukov14

RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany

M. Ata, J. Caudron, E. Dietz-Laursonn, D. Duchardt, M. Erdmann, A. Güth, T. Hebbeker,

C. Heidemann, K. Hoepfner, T. Klimkovich, D. Klingebiel, P. Kreuzer, D. Lanske†,

J. Lingemann, C. Magass, M. Merschmeyer, A. Meyer, M. Olschewski, P. Papacz, H. Pieta,

H. Reithler, S.A. Schmitz, J.F. Schulte, L. Sonnenschein, J. Steggemann, D. Teyssier,

S. Thüer, M. Weber

– 18 –



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RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany

M. Bontenackels, V. Cherepanov, M. Davids, G. Flügge, H. Geenen, M. Geisler, W. Haj

Ahmad, F. Hoehle, B. Kargoll, T. Kress, Y. Kuessel, A. Linn, A. Nowack, L. Perchalla,

O. Pooth, J. Rennefeld, P. Sauerland, A. Stahl

Deutsches Elektronen-Synchrotron, Hamburg, Germany

M. Aldaya Martin, J. Behr, W. Behrenhoff, U. Behrens, M. Bergholz15, A. Bethani,

K. Borras, A. Burgmeier, A. Cakir, L. Calligaris, A. Campbell, E. Castro, F. Costanza,

D. Dammann, G. Eckerlin, D. Eckstein, D. Fischer, G. Flucke, A. Geiser, I. Glushkov,

S. Habib, J. Hauk, H. Jung1, M. Kasemann, P. Katsas, C. Kleinwort, H. Kluge,

A. Knutsson, M. Krämer, D. Krücker, E. Kuznetsova, W. Lange, W. Lohmann15,

B. Lutz, R. Mankel, I. Marfin, M. Marienfeld, I.-A. Melzer-Pellmann, A.B. Meyer,

J. Mnich, A. Mussgiller, S. Naumann-Emme, J. Olzem, H. Perrey, A. Petrukhin, D. Pitzl,

A. Raspereza, P.M. Ribeiro Cipriano, C. Riedl, M. Rosin, J. Salfeld-Nebgen, R. Schmidt15,

T. Schoerner-Sadenius, N. Sen, A. Spiridonov, M. Stein, R. Walsh, C. Wissing

University of Hamburg, Hamburg, Germany

C. Autermann, V. Blobel, S. Bobrovskyi, J. Draeger, H. Enderle, J. Erfle, U. Gebbert,

M. Görner, T. Hermanns, R.S. Höing, K. Kaschube, G. Kaussen, H. Kirschenmann,

R. Klanner, J. Lange, B. Mura, F. Nowak, N. Pietsch, D. Rathjens, C. Sander, H. Schettler,

P. Schleper, E. Schlieckau, A. Schmidt, M. Schröder, T. Schum, M. Seidel, H. Stadie,

G. Steinbrück, J. Thomsen

Institut für Experimentelle Kernphysik, Karlsruhe, Germany

C. Barth, J. Berger, T. Chwalek, W. De Boer, A. Dierlamm, M. Feindt, M. Guthoff1,

C. Hackstein, F. Hartmann, M. Heinrich, H. Held, K.H. Hoffmann, S. Honc, I. Katkov14,

J.R. Komaragiri, D. Martschei, S. Mueller, Th. Müller, M. Niegel, A. Nürnberg, O. Oberst,

A. Oehler, J. Ott, T. Peiffer, G. Quast, K. Rabbertz, F. Ratnikov, N. Ratnikova, S. Röcker,

C. Saout, A. Scheurer, F.-P. Schilling, M. Schmanau, G. Schott, H.J. Simonis, F.M. Stober,

D. Troendle, R. Ulrich, J. Wagner-Kuhr, T. Weiler, M. Zeise, E.B. Ziebarth

Institute of Nuclear Physics ”Demokritos”, Aghia Paraskevi, Greece

G. Daskalakis, T. Geralis, S. Kesisoglou, A. Kyriakis, D. Loukas, I. Manolakos, A. Markou,

C. Markou, C. Mavrommatis, E. Ntomari

University of Athens, Athens, Greece

L. Gouskos, T.J. Mertzimekis, A. Panagiotou, N. Saoulidou

University of Ioánnina, Ioánnina, Greece

I. Evangelou, C. Foudas1, P. Kokkas, N. Manthos, I. Papadopoulos, V. Patras

KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary

G. Bencze, C. Hajdu1, P. Hidas, D. Horvath16, K. Krajczar17, B. Radics, F. Sikler1,

V. Veszpremi, G. Vesztergombi17

Institute of Nuclear Research ATOMKI, Debrecen, Hungary

N. Beni, S. Czellar, J. Molnar, J. Palinkas, Z. Szillasi

– 19 –



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University of Debrecen, Debrecen, Hungary

J. Karancsi, P. Raics, Z.L. Trocsanyi, B. Ujvari

Panjab University, Chandigarh, India

S.B. Beri, V. Bhatnagar, N. Dhingra, R. Gupta, M. Jindal, M. Kaur, J.M. Kohli,

M.Z. Mehta, N. Nishu, L.K. Saini, A. Sharma, J. Singh, S.P. Singh

University of Delhi, Delhi, India

S. Ahuja, A. Bhardwaj, B.C. Choudhary, A. Kumar, A. Kumar, S. Malhotra, M. Naimud-

din, K. Ranjan, V. Sharma, R.K. Shivpuri

Saha Institute of Nuclear Physics, Kolkata, India

S. Banerjee, S. Bhattacharya, S. Dutta, B. Gomber, Sa. Jain, Sh. Jain, R. Khurana,

S. Sarkar

Bhabha Atomic Research Centre, Mumbai, India

A. Abdulsalam, R.K. Choudhury, D. Dutta, S. Kailas, V. Kumar, A.K. Mohanty1,

L.M. Pant, P. Shukla

Tata Institute of Fundamental Research - EHEP, Mumbai, India

T. Aziz, S. Ganguly, M. Guchait18, A. Gurtu19, M. Maity20, G. Majumder, K. Mazumdar,

G.B. Mohanty, B. Parida, K. Sudhakar, N. Wickramage

Tata Institute of Fundamental Research - HECR, Mumbai, India

S. Banerjee, S. Dugad

Institute for Research in Fundamental Sciences (IPM), Tehran, Iran

H. Arfaei, H. Bakhshiansohi21, S.M. Etesami22, A. Fahim21, M. Hashemi, H. Hesari,

A. Jafari21, M. Khakzad, A. Mohammadi23, M. Mohammadi Najafabadi, S. Paktinat

Mehdiabadi, B. Safarzadeh24, M. Zeinali22

INFN Sezione di Bari a, Università di Bari b, Politecnico di Bari c, Bari, Italy

M. Abbresciaa,b, L. Barbonea,b, C. Calabriaa,b,1, S.S. Chhibraa,b, A. Colaleoa,

D. Creanzaa,c, N. De Filippisa,c,1, M. De Palmaa,b, L. Fiorea, G. Iasellia,c, L. Lusitoa,b,

G. Maggia,c, M. Maggia, B. Marangellia,b, S. Mya,c, S. Nuzzoa,b, N. Pacificoa,b,

A. Pompilia,b, G. Pugliesea,c, G. Selvaggia,b, L. Silvestrisa, G. Singha,b, G. Zitoa

INFN Sezione di Bologna a, Università di Bologna b, Bologna, Italy

G. Abbiendia, A.C. Benvenutia, D. Bonacorsia,b, S. Braibant-Giacomellia,b,

L. Brigliadoria,b, P. Capiluppia,b, A. Castroa,b, F.R. Cavalloa, M. Cuffiania,b,

G.M. Dallavallea, F. Fabbria, A. Fanfania,b, D. Fasanellaa,b,1, P. Giacomellia,

C. Grandia, L. Guiducci, S. Marcellinia, G. Masettia, M. Meneghellia,b,1, A. Montanaria,

F.L. Navarriaa,b, F. Odoricia, A. Perrottaa, F. Primaveraa,b, A.M. Rossia,b, T. Rovellia,b,

G. Sirolia,b, R. Travaglinia,b

INFN Sezione di Catania a, Università di Catania b, Catania, Italy

S. Albergoa,b, G. Cappelloa,b, M. Chiorbolia,b, S. Costaa,b, R. Potenzaa,b, A. Tricomia,b,

C. Tuvea,b

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INFN Sezione di Firenze a, Università di Firenze b, Firenze, Italy

G. Barbaglia, V. Ciullia,b, C. Civininia, R. D’Alessandroa,b, E. Focardia,b, S. Frosalia,b,

E. Galloa, S. Gonzia,b, M. Meschinia, S. Paolettia, G. Sguazzonia, A. Tropianoa,1

INFN Laboratori Nazionali di Frascati, Frascati, Italy

L. Benussi, S. Bianco, S. Colafranceschi25, F. Fabbri, D. Piccolo

INFN Sezione di Genova, Genova, Italy

P. Fabbricatore, R. Musenich

INFN Sezione di Milano-Bicocca a, Università di Milano-Bicocca b, Milano,

Italy

A. Benagliaa,b,1, F. De Guioa,b, L. Di Matteoa,b,1, S. Fiorendia,b, S. Gennaia,1, A. Ghezzia,b,

S. Malvezzia, R.A. Manzonia,b, A. Martellia,b, A. Massironia,b,1, D. Menascea, L. Moronia,

M. Paganonia,b, D. Pedrinia, S. Ragazzia,b, N. Redaellia, S. Salaa, T. Tabarelli de Fatisa,b

INFN Sezione di Napoli a, Università di Napoli ”Federico II” b, Napoli, Italy

S. Buontempoa, C.A. Carrillo Montoyaa,1, N. Cavalloa,26, A. De Cosaa,b, O. Doganguna,b,

F. Fabozzia,26, A.O.M. Iorioa,1, L. Listaa, S. Meolaa,27, M. Merolaa,b, P. Paoluccia

INFN Sezione di Padova a, Università di Padova b, Università di

Trento (Trento) c, Padova, Italy

P. Azzia, N. Bacchettaa,1, P. Bellana,b, D. Biselloa,b, A. Brancaa,1, R. Carlina,b,

P. Checchiaa, T. Dorigoa, U. Dossellia, F. Gasparinia,b, A. Gozzelinoa, K. Kanishcheva,c,

S. Lacapraraa, I. Lazzizzeraa,c, M. Margonia,b, A.T. Meneguzzoa,b, L. Perrozzia,

N. Pozzobona,b, P. Ronchesea,b, F. Simonettoa,b, E. Torassaa, M. Tosia,b,1, S. Vaninia,b,

P. Zottoa,b, G. Zumerlea,b

INFN Sezione di Pavia a, Università di Pavia b, Pavia, Italy

M. Gabusia,b, S.P. Rattia,b, C. Riccardia,b, P. Torrea,b, P. Vituloa,b

INFN Sezione di Perugia a, Università di Perugia b, Perugia, Italy

G.M. Bileia, L. Fanòa,b, P. Laricciaa,b, A. Lucaronia,b,1, G. Mantovania,b, M. Menichellia,

A. Nappia,b, F. Romeoa,b, A. Saha, A. Santocchiaa,b, S. Taronia,b,1

INFN Sezione di Pisa a, Università di Pisa b, Scuola Normale Superiore di

Pisa c, Pisa, Italy

P. Azzurria,c, G. Bagliesia, T. Boccalia, G. Broccoloa,c, R. Castaldia, R.T. D’Agnoloa,c,

R. Dell’Orsoa, F. Fioria,b,1, L. Foàa,c, A. Giassia, A. Kraana, F. Ligabuea,c, T. Lomtadzea,

L. Martinia,28, A. Messineoa,b, F. Pallaa, F. Palmonaria, A. Rizzia,b, A.T. Serbana,29,

P. Spagnoloa, P. Squillacioti1, R. Tenchinia, G. Tonellia,b,1, A. Venturia,1, P.G. Verdinia

INFN Sezione di Roma a, Università di Roma ”La Sapienza” b, Roma, Italy

L. Baronea,b, F. Cavallaria, D. Del Rea,b,1, M. Diemoza, C. Fanellia,b, M. Grassia,1,

E. Longoa,b, P. Meridiania,1, F. Michelia,b, S. Nourbakhsha, G. Organtinia,b, F. Pandolfia,b,

R. Paramattia, S. Rahatloua,b, M. Sigamania, L. Soffia,b

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INFN Sezione di Torino a, Università di Torino b, Università del Piemonte

Orientale (Novara) c, Torino, Italy

N. Amapanea,b, R. Arcidiaconoa,c, S. Argiroa,b, M. Arneodoa,c, C. Biinoa, C. Bottaa,b,

N. Cartigliaa, R. Castelloa,b, M. Costaa,b, N. Demariaa, A. Grazianoa,b, C. Mariottia,1,

S. Masellia, E. Migliorea,b, V. Monacoa,b, M. Musicha,1, M.M. Obertinoa,c, N. Pastronea,

M. Pelliccionia, A. Potenzaa,b, A. Romeroa,b, M. Ruspaa,c, R. Sacchia,b, V. Solaa,b,

A. Solanoa,b, A. Staianoa, A. Vilela Pereiraa

INFN Sezione di Trieste a, Università di Trieste b, Trieste, Italy

S. Belfortea, F. Cossuttia, G. Della Riccaa,b, B. Gobboa, M. Maronea,b,1, D. Montaninoa,b,1,

A. Penzoa, A. Schizzia,b

Kangwon National University, Chunchon, Korea

S.G. Heo, T.Y. Kim, S.K. Nam

Kyungpook National University, Daegu, Korea

S. Chang, J. Chung, D.H. Kim, G.N. Kim, D.J. Kong, H. Park, S.R. Ro, D.C. Son, T. Son

Chonnam National University, Institute for Universe and Elementary Particles,

Kwangju, Korea

J.Y. Kim, Zero J. Kim, S. Song

Konkuk University, Seoul, Korea

H.Y. Jo

Korea University, Seoul, Korea

S. Choi, D. Gyun, B. Hong, M. Jo, H. Kim, T.J. Kim, K.S. Lee, D.H. Moon, S.K. Park,

E. Seo

University of Seoul, Seoul, Korea

M. Choi, S. Kang, H. Kim, J.H. Kim, C. Park, I.C. Park, S. Park, G. Ryu

Sungkyunkwan University, Suwon, Korea

Y. Cho, Y. Choi, Y.K. Choi, J. Goh, M.S. Kim, E. Kwon, B. Lee, J. Lee, S. Lee, H. Seo,

I. Yu

Vilnius University, Vilnius, Lithuania

M.J. Bilinskas, I. Grigelionis, M. Janulis, A. Juodagalvis

Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico

H. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-de La Cruz, R. Lopez-Fernandez,

R. Magaña Villalba, J. Mart́ınez-Ortega, A. Sánchez-Hernández, L.M. Villasenor-Cendejas

Universidad Iberoamericana, Mexico City, Mexico

S. Carrillo Moreno, F. Vazquez Valencia

Benemerita Universidad Autonoma de Puebla, Puebla, Mexico

H.A. Salazar Ibarguen

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Universidad Autónoma de San Luis Potośı, San Luis Potośı, Mexico

E. Casimiro Linares, A. Morelos Pineda, M.A. Reyes-Santos

University of Auckland, Auckland, New Zealand

D. Krofcheck

University of Canterbury, Christchurch, New Zealand

A.J. Bell, P.H. Butler, R. Doesburg, S. Reucroft, H. Silverwood

National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan

M. Ahmad, M.I. Asghar, H.R. Hoorani, S. Khalid, W.A. Khan, T. Khurshid, S. Qazi,

M.A. Shah, M. Shoaib

Institute of Experimental Physics, Faculty of Physics, University of Warsaw,

Warsaw, Poland

G. Brona, K. Bunkowski, M. Cwiok, W. Dominik, K. Doroba, A. Kalinowski, M. Konecki,

J. Krolikowski

Soltan Institute for Nuclear Studies, Warsaw, Poland

H. Bialkowska, B. Boimska, T. Frueboes, R. Gokieli, M. Górski, M. Kazana, K. Nawrocki,

K. Romanowska-Rybinska, M. Szleper, G. Wrochna, P. Zalewski

Laboratório de Instrumentação e F́ısica Experimental de Part́ıculas, Lisboa,

Portugal

N. Almeida, P. Bargassa, A. David, P. Faccioli, P.G. Ferreira Parracho, M. Gallinaro,

P. Musella, J. Seixas, J. Varela, P. Vischia

Joint Institute for Nuclear Research, Dubna, Russia

I. Belotelov, M. Gavrilenko, I. Golutvin, I. Gorbunov, A. Kamenev, V. Karjavin, G. Kozlov,

A. Lanev, A. Malakhov, P. Moisenz, V. Palichik, V. Perelygin, M. Savina, S. Shmatov,

V. Smirnov, A. Volodko, A. Zarubin

Petersburg Nuclear Physics Institute, Gatchina (St Petersburg), Russia

S. Evstyukhin, V. Golovtsov, Y. Ivanov, V. Kim, P. Levchenko, V. Murzin, V. Oreshkin,

I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev, An. Vorobyev

Institute for Nuclear Research, Moscow, Russia

Yu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov, N. Krasnikov,

V. Matveev, A. Pashenkov, D. Tlisov, A. Toropin

Institute for Theoretical and Experimental Physics, Moscow, Russia

V. Epshteyn, M. Erofeeva, V. Gavrilov, M. Kossov1, N. Lychkovskaya, V. Popov,

G. Safronov, S. Semenov, V. Stolin, E. Vlasov, A. Zhokin

Moscow State University, Moscow, Russia

A. Belyaev, E. Boos, V. Bunichev, M. Dubinin4, L. Dudko, A. Ershov, A. Gribushin,

V. Klyukhin, O. Kodolova, I. Lokhtin, A. Markina, S. Obraztsov, M. Perfilov,

S. Petrushanko, A. Popov, L. Sarycheva†, V. Savrin

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P.N. Lebedev Physical Institute, Moscow, Russia

V. Andreev, M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, G. Mesyats,

S.V. Rusakov, A. Vinogradov

State Research Center of Russian Federation, Institute for High Energy

Physics, Protvino, Russia

I. Azhgirey, I. Bayshev, S. Bitioukov, V. Grishin1, V. Kachanov, D. Konstantinov,

A. Korablev, V. Krychkine, V. Petrov, R. Ryutin, A. Sobol, L. Tourtchanovitch, S. Troshin,

N. Tyurin, A. Uzunian, A. Volkov

University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear

Sciences, Belgrade, Serbia

P. Adzic30, M. Djordjevic, M. Ekmedzic, D. Krpic30, J. Milosevic

Centro de Investigaciones Energéticas Medioambientales y Tec-

nológicas (CIEMAT), Madrid, Spain

M. Aguilar-Benitez, J. Alcaraz Maestre, P. Arce, C. Battilana, E. Calvo, M. Cerrada,

M. Chamizo Llatas, N. Colino, B. De La Cruz, A. Delgado Peris, C. Diez Pardos,

D. Domı́nguez Vázquez, C. Fernandez Bedoya, J.P. Fernández Ramos, A. Ferrando,

J. Flix, M.C. Fouz, P. Garcia-Abia, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez,

M.I. Josa, G. Merino, J. Puerta Pelayo, I. Redondo, L. Romero, J. Santaolalla, M.S. Soares,

C. Willmott

Universidad Autónoma de Madrid, Madrid, Spain

C. Albajar, G. Codispoti, J.F. de Trocóniz

Universidad de Oviedo, Oviedo, Spain

J. Cuevas, J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero, L. Lloret Iglesias,

J. Piedra Gomez31, J.M. Vizan Garcia

Instituto de F́ısica de Cantabria (IFCA), CSIC-Universidad de Cantabria,

Santander, Spain

J.A. Brochero Cifuentes, I.J. Cabrillo, A. Calderon, S.H. Chuang, J. Duarte Campderros,

M. Felcini32, M. Fernandez, G. Gomez, J. Gonzalez Sanchez, C. Jorda, P. Lobelle Pardo,

A. Lopez Virto, J. Marco, R. Marco, C. Martinez Rivero, F. Matorras, F.J. Munoz Sanchez,

T. Rodrigo, A.Y. Rodŕıguez-Marrero, A. Ruiz-Jimeno, L. Scodellaro, M. Sobron Sanudo,

I. Vila, R. Vilar Cortabitarte

CERN, European Organization for Nuclear Research, Geneva, Switzerland

D. Abbaneo, E. Auffray, G. Auzinger, P. Baillon, A.H. Ball, D. Barney, C. Bernet5,

G. Bianchi, P. Bloch, A. Bocci, A. Bonato, H. Breuker, T. Camporesi, G. Cerminara,

T. Christiansen, J.A. Coarasa Perez, D. D’Enterria, A. De Roeck, S. Di Guida, M. Dobson,

N. Dupont-Sagorin, A. Elliott-Peisert, B. Frisch, W. Funk, G. Georgiou, M. Giffels,

D. Gigi, K. Gill, D. Giordano, M. Giunta, F. Glege, R. Gomez-Reino Garrido, P. Govoni,

S. Gowdy, R. Guida, M. Hansen, P. Harris, C. Hartl, J. Harvey, B. Hegner, A. Hinzmann,

V. Innocente, P. Janot, K. Kaadze, E. Karavakis, K. Kousouris, P. Lecoq, P. Lenzi,

C. Lourenço, T. Mäki, M. Malberti, L. Malgeri, M. Mannelli, L. Masetti, F. Meijers,

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S. Mersi, E. Meschi, R. Moser, M.U. Mozer, M. Mulders, E. Nesvold, M. Nguyen,

T. Orimoto, L. Orsini, E. Palencia Cortezon, E. Perez, A. Petrilli, A. Pfeiffer, M. Pierini,

M. Pimiä, D. Piparo, G. Polese, L. Quertenmont, A. Racz, W. Reece, J. Rodrigues Antunes,

G. Rolandi33, T. Rommerskirchen, C. Rovelli34, M. Rovere, H. Sakulin, F. Santanastasio,

C. Schäfer, C. Schwick, I. Segoni, S. Sekmen, A. Sharma, P. Siegrist, P. Silva, M. Simon,

P. Sphicas35, D. Spiga, M. Spiropulu4, M. Stoye, A. Tsirou, G.I. Veres17, J.R. Vlimant,

H.K. Wöhri, S.D. Worm36, W.D. Zeuner

Paul Scherrer Institut, Villigen, Switzerland

W. Bertl, K. Deiters, W. Erdmann, K. Gabathuler, R. Horisberger, Q. Ingram,

H.C. Kaestli, S. König, D. Kotlinski, U. Langenegger, F. Meier, D. Renker, T. Rohe,

J. Sibille37

Institute for Particle Physics, ETH Zurich, Zurich, Switzerland

L. Bäni, P. Bortignon, M.A. Buchmann, B. Casal, N. Chanon, Z. Chen, A. Deisher,

G. Dissertori, M. Dittmar, M. Dünser, J. Eugster, K. Freudenreich, C. Grab, P. Lecomte,

W. Lustermann, A.C. Marini, P. Martinez Ruiz del Arbol, N. Mohr, F. Moortgat,

C. Nägeli38, P. Nef, F. Nessi-Tedaldi, L. Pape, F. Pauss, M. Peruzzi, F.J. Ronga, M. Rossini,

L. Sala, A.K. Sanchez, A. Starodumov39, B. Stieger, M. Takahashi, L. Tauscher†, A. Thea,

K. Theofilatos, D. Treille, C. Urscheler, R. Wallny, H.A. Weber, L. Wehrli

Universität Zürich, Zurich, Switzerland

E. Aguilo, C. Amsler, V. Chiochia, S. De Visscher, C. Favaro, M. Ivova Rikova, B. Millan

Mejias, P. Otiougova, P. Robmann, H. Snoek, S. Tupputi, M. Verzetti

National Central University, Chung-Li, Taiwan

Y.H. Chang, K.H. Chen, A. Go, C.M. Kuo, S.W. Li, W. Lin, Z.K. Liu, Y.J. Lu,

D. Mekterovic, A.P. Singh, R. Volpe, S.S. Yu

National Taiwan University (NTU), Taipei, Taiwan

P. Bartalini, P. Chang, Y.H. Chang, Y.W. Chang, Y. Chao, K.F. Chen, C. Dietz,

U. Grundler, W.-S. Hou, Y. Hsiung, K.Y. Kao, Y.J. Lei, R.-S. Lu, D. Majumder,

E. Petrakou, X. Shi, J.G. Shiu, Y.M. Tzeng, M. Wang

Cukurova University, Adana, Turkey

A. Adiguzel, M.N. Bakirci40, S. Cerci41, C. Dozen, I. Dumanoglu, E. Eskut, S. Girgis,

G. Gokbulut, I. Hos, E.E. Kangal, G. Karapinar, A. Kayis Topaksu, G. Onengut,

K. Ozdemir, S. Ozturk42, A. Polatoz, K. Sogut43, D. Sunar Cerci41, B. Tali41, H. Topakli40,

L.N. Vergili, M. Vergili

Middle East Technical University, Physics Department, Ankara, Turkey

I.V. Akin, T. Aliev, B. Bilin, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler, K. Ocalan,

A. Ozpineci, M. Serin, R. Sever, U.E. Surat, M. Yalvac, E. Yildirim, M. Zeyrek

Bogazici University, Istanbul, Turkey

M. Deliomeroglu, E. Gülmez, B. Isildak, M. Kaya44, O. Kaya44, S. Ozkorucuklu45,

N. Sonmez46

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Istanbul Technical University, Istanbul, Turkey

K. Cankocak

National Scientific Center, Kharkov Institute of Physics and Technology,

Kharkov, Ukraine

L. Levchuk

University of Bristol, Bristol, United Kingdom

F. Bostock, J.J. Brooke, E. Clement, D. Cussans, H. Flacher, R. Frazier, J. Goldstein,

M. Grimes, G.P. Heath, H.F. Heath, L. Kreczko, S. Metson, D.M. Newbold36, K. Nirun-

pong, A. Poll, S. Senkin, V.J. Smith, T. Williams

Rutherford Appleton Laboratory, Didcot, United Kingdom

L. Basso47, K.W. Bell, A. Belyaev47, C. Brew, R.M. Brown, D.J.A. Cockerill, J.A. Cough-

lan, K. Harder, S. Harper, J. Jackson, B.W. Kennedy, E. Olaiya, D. Petyt, B.C. Radburn-

Smith, C.H. Shepherd-Themistocleous, I.R. Tomalin, W.J. Womersley

Imperial College, London, United Kingdom

R. Bainbridge, G. Ball, R. Beuselinck, O. Buchmuller, D. Colling, N. Cripps, M. Cutajar,

P. Dauncey, G. Davies, M. Della Negra, W. Ferguson, J. Fulcher, D. Futyan, A. Gilbert,

A. Guneratne Bryer, G. Hall, Z. Hatherell, J. Hays, G. Iles, M. Jarvis, G. Karapostoli,

L. Lyons, A.-M. Magnan, J. Marrouche, B. Mathias, R. Nandi, J. Nash, A. Nikitenko39,

A. Papageorgiou, J. Pela1, M. Pesaresi, K. Petridis, M. Pioppi48, D.M. Raymond, S. Roger-

son, N. Rompotis, A. Rose, M.J. Ryan, C. Seez, P. Sharp†, A. Sparrow, A. Tapper,

M. Vazquez Acosta, T. Virdee, S. Wakefield, N. Wardle, T. Whyntie

Brunel University, Uxbridge, United Kingdom

M. Barrett, M. Chadwick, J.E. Cole, P.R. Hobson, A. Khan, P. Kyberd, D. Leggat,

D. Leslie, W. Martin, I.D. Reid, P. Symonds, L. Teodorescu, M. Turner

Baylor University, Waco, USA

K. Hatakeyama, H. Liu, T. Scarborough

The University of Alabama, Tuscaloosa, USA

C. Henderson, P. Rumerio

Boston University, Boston, USA

A. Avetisyan, T. Bose, C. Fantasia, A. Heister, J. St. John, P. Lawson, D. Lazic, J. Rohlf,

D. Sperka, L. Sulak

Brown University, Providence, USA

J. Alimena, S. Bhattacharya, D. Cutts, A. Ferapontov, U. Heintz, S. Jabeen, G. Kukartsev,

G. Landsberg, M. Luk, M. Narain, D. Nguyen, M. Segala, T. Sinthuprasith, T. Speer,

K.V. Tsang

University of California, Davis, Davis, USA

R. Breedon, G. Breto, M. Calderon De La Barca Sanchez, S. Chauhan, M. Chertok,

J. Conway, R. Conway, P.T. Cox, J. Dolen, R. Erbacher, M. Gardner, R. Houtz, W. Ko,

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A. Kopecky, R. Lander, O. Mall, T. Miceli, R. Nelson, D. Pellett, B. Rutherford, M. Searle,

J. Smith, M. Squires, M. Tripathi, R. Vasquez Sierra

University of California, Los Angeles, Los Angeles, USA

V. Andreev, D. Cline, R. Cousins, J. Duris, S. Erhan, P. Everaerts, C. Farrell, J. Hauser,

M. Ignatenko, C. Plager, G. Rakness, P. Schlein†, J. Tucker, V. Valuev, M. Weber

University of California, Riverside, Riverside, USA

J. Babb, R. Clare, M.E. Dinardo, J. Ellison, J.W. Gary, F. Giordano, G. Hanson,

G.Y. Jeng49, H. Liu, O.R. Long, A. Luthra, H. Nguyen, S. Paramesvaran, J. Sturdy,

S. Sumowidagdo, R. Wilken, S. Wimpenny

University of California, San Diego, La Jolla, USA

W. Andrews, J.G. Branson, G.B. Cerati, S. Cittolin, D. Evans, F. Golf, A. Holzner,

R. Kelley, M. Lebourgeois, J. Letts, I. Macneill, B. Mangano, J. Muelmenstaedt, S. Padhi,

C. Palmer, G. Petrucciani, M. Pieri, R. Ranieri, M. Sani, V. Sharma, S. Simon, E. Sudano,

M. Tadel, Y. Tu, A. Vartak, S. Wasserbaech50, F. Würthwein, A. Yagil, J. Yoo

University of California, Santa Barbara, Santa Barbara, USA

D. Barge, R. Bellan, C. Campagnari, M. D’Alfonso, T. Danielson, K. Flowers, P. Geffert,

J. Incandela, C. Justus, P. Kalavase, S.A. Koay, D. Kovalskyi1, V. Krutelyov, S. Lowette,

N. Mccoll, V. Pavlunin, F. Rebassoo, J. Ribnik, J. Richman, R. Rossin, D. Stuart, W. To,

C. West

California Institute of Technology, Pasadena, USA

A. Apresyan, A. Bornheim, Y. Chen, E. Di Marco, J. Duarte, M. Gataullin, Y. Ma, A. Mott,

H.B. Newman, C. Rogan, V. Timciuc, P. Traczyk, J. Veverka, R. Wilkinson, Y. Yang,

R.Y. Zhu

Carnegie Mellon University, Pittsburgh, USA

B. Akgun, R. Carroll, T. Ferguson, Y. Iiyama, D.W. Jang, Y.F. Liu, M. Paulini, H. Vogel,

I. Vorobiev

University of Colorado at Boulder, Boulder, USA

J.P. Cumalat, B.R. Drell, C.J. Edelmaier, W.T. Ford, A. Gaz, B. Heyburn, E. Luiggi

Lopez, J.G. Smith, K. Stenson, K.A. Ulmer, S.R. Wagner

Cornell University, Ithaca, USA

L. Agostino, J. Alexander, A. Chatterjee, N. Eggert, L.K. Gibbons, B. Heltsley, W. Hop-

kins, A. Khukhunaishvili, B. Kreis, N. Mirman, G. Nicolas Kaufman, J.R. Patterson,

A. Ryd, E. Salvati, W. Sun, W.D. Teo, J. Thom, J. Thompson, J. Vaughan, Y. Weng,

L. Winstrom, P. Wittich

Fairfield University, Fairfield, USA

D. Winn

Fermi National Accelerator Laboratory, Batavia, USA

S. Abdullin, M. Albrow, J. Anderson, L.A.T. Bauerdick, A. Beretvas, J. Berryhill,

P.C. Bhat, I. Bloch, K. Burkett, J.N. Butler, V. Chetluru, H.W.K. Cheung, F. Chlebana,

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V.D. Elvira, I. Fisk, J. Freeman, Y. Gao, D. Green, O. Gutsche, A. Hahn, J. Hanlon,

R.M. Harris, J. Hirschauer, B. Hooberman, S. Jindariani, M. Johnson, U. Joshi, B. Kilmin-

ster, B. Klima, S. Kunori, S. Kwan, C. Leonidopoulos, D. Lincoln, R. Lipton, L. Lueking,

J. Lykken, K. Maeshima, J.M. Marraffino, S. Maruyama, D. Mason, P. McBride, K. Mishra,

S. Mrenna, Y. Musienko51, C. Newman-Holmes, V. O’Dell, O. Prokofyev, E. Sexton-

Kennedy, S. Sharma, W.J. Spalding, L. Spiegel, P. Tan, L. Taylor, S. Tkaczyk, N.V. Tran,

L. Uplegger, E.W. Vaandering, R. Vidal, J. Whitmore, W. Wu, F. Yang, F. Yumiceva,

J.C. Yun

University of Florida, Gainesville, USA

D. Acosta, P. Avery, D. Bourilkov, M. Chen, S. Das, M. De Gruttola, G.P. Di Giovanni,

D. Dobur, A. Drozdetskiy, R.D. Field, M. Fisher, Y. Fu, I.K. Furic, J. Gartner, J. Hugon,

B. Kim, J. Konigsberg, A. Korytov, A. Kropivnitskaya, T. Kypreos, J.F. Low, K. Matchev,

P. Milenovic52, G. Mitselmakher, L. Muniz, R. Remington, A. Rinkevicius, P. Sellers,

N. Skhirtladze, M. Snowball, J. Yelton, M. Zakaria

Florida International University, Miami, USA

V. Gaultney, L.M. Lebolo, S. Linn, P. Markowitz, G. Martinez, J.L. Rodriguez

Florida State University, Tallahassee, USA

T. Adams, A. Askew, J. Bochenek, J. Chen, B. Diamond, S.V. Gleyzer, J. Haas,

S. Hagopian, V. Hagopian, M. Jenkins, K.F. Johnson, H. Prosper, V. Veeraraghavan,

M. Weinberg

Florida Institute of Technology, Melbourne, USA

M.M. Baarmand, B. Dorney, M. Hohlmann, H. Kalakhety, I. Vodopiyanov

University of Illinois at Chicago (UIC), Chicago, USA

M.R. Adams, I.M. Anghel, L. Apanasevich, Y. Bai, V.E. Bazterra, R.R. Betts, J. Callner,

R. Cavanaugh, C. Dragoiu, O. Evdokimov, E.J. Garcia-Solis, L. Gauthier, C.E. Gerber,

D.J. Hofman, S. Khalatyan, F. Lacroix, M. Malek, C. O’Brien, C. Silkworth, D. Strom,

N. Varelas

The University of Iowa, Iowa City, USA

U. Akgun, E.A. Albayrak, B. Bilki53, K. Chung, W. Clarida, F. Duru, S. Griffiths, C.K. Lae,

J.-P. Merlo, H. Mermerkaya54, A. Mestvirishvili, A. Moeller, J. Nachtman, C.R. Newsom,

E. Norbeck, J. Olson, Y. Onel, F. Ozok, S. Sen, E. Tiras, J. Wetzel, T. Yetkin, K. Yi

Johns Hopkins University, Baltimore, USA

B.A. Barnett, B. Blumenfeld, S. Bolognesi, D. Fehling, G. Giurgiu, A.V. Gritsan, Z.J. Guo,

G. Hu, P. Maksimovic, S. Rappoccio, M. Swartz, A. Whitbeck

The University of Kansas, Lawrence, USA

P. Baringer, A. Bean, G. Benelli, O. Grachov, R.P. Kenny Iii, M. Murray, D. Noonan,

V. Radicci, S. Sanders, R. Stringer, G. Tinti, J.S. Wood, V. Zhukova

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Kansas State University, Manhattan, USA

A.F. Barfuss, T. Bolton, I. Chakaberia, A. Ivanov, S. Khalil, M. Makouski, Y. Maravin,

S. Shrestha, I. Svintradze

Lawrence Livermore National Laboratory, Livermore, USA

J. Gronberg, D. Lange, D. Wright

University of Maryland, College Park, USA

A. Baden, M. Boutemeur, B. Calvert, S.C. Eno, J.A. Gomez, N.J. Hadley, R.G. Kellogg,

M. Kirn, T. Kolberg, Y. Lu, M. Marionneau, A.C. Mignerey, A. Peterman, K. Rossato,

A. Skuja, J. Temple, M.B. Tonjes, S.C. Tonwar, E. Twedt

Massachusetts Institute of Technology, Cambridge, USA

G. Bauer, J. Bendavid, W. Busza, E. Butz, I.A. Cali, M. Chan, V. Dutta, G. Gomez

Ceballos, M. Goncharov, K.A. Hahn, Y. Kim, M. Klute, Y.-J. Lee, W. Li, P.D. Luckey,

T. Ma, S. Nahn, C. Paus, D. Ralph, C. Roland, G. Roland, M. Rudolph, G.S.F. Stephans,

F. Stöckli, K. Sumorok, K. Sung, D. Velicanu, E.A. Wenger, R. Wolf, B. Wyslouch, S. Xie,

M. Yang, Y. Yilmaz, A.S. Yoon, M. Zanetti

University of Minnesota, Minneapolis, USA

S.I. Cooper, P. Cushman, B. Dahmes, A. De Benedetti, G. Franzoni, A. Gude, J. Haupt,

S.C. Kao, K. Klapoetke, Y. Kubota, J. Mans, N. Pastika, R. Rusack, M. Sasseville,

A. Singovsky, N. Tambe, J. Turkewitz

University of Mississippi, University, USA

L.M. Cremaldi, R. Kroeger, L. Perera, R. Rahmat, D.A. Sanders

University of Nebraska-Lincoln, Lincoln, USA

E. Avdeeva, K. Bloom, S. Bose, J. Butt, D.R. Claes, A. Dominguez, M. Eads, P. Jindal,

J. Keller, I. Kravchenko, J. Lazo-Flores, H. Malbouisson, S. Malik, G.R. Snow

State University of New York at Buffalo, Buffalo, USA

U. Baur, A. Godshalk, I. Iashvili, S. Jain, A. Kharchilava, A. Kumar, S.P. Shipkowski,

K. Smith

Northeastern University, Boston, USA

G. Alverson, E. Barberis, D. Baumgartel, M. Chasco, J. Haley, D. Trocino, D. Wood,

J. Zhang

Northwestern University, Evanston, USA

A. Anastassov, A. Kubik, N. Mucia, N. Odell, R.A. Ofierzynski, B. Pollack, A. Pozdnyakov,

M. Schmitt, S. Stoynev, M. Velasco, S. Won

University of Notre Dame, Notre Dame, USA

L. Antonelli, D. Berry, A. Brinkerhoff, M. Hildreth, C. Jessop, D.J. Karmgard, J. Kolb,

K. Lannon, W. Luo, S. Lynch, N. Marinelli, D.M. Morse, T. Pearson, R. Ruchti,

J. Slaunwhite, N. Valls, J. Warchol, M. Wayne, M. Wolf, J. Ziegler

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8
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2
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The Ohio State University, Columbus, USA

B. Bylsma, L.S. Durkin, C. Hill, R. Hughes, P. Killewald, K. Kotov, T.Y. Ling, D. Puigh,

M. Rodenburg, C. Vuosalo, G. Williams, B.L. Winer

Princeton University, Princeton, USA

N. Adam, E. Berry, P. Elmer, D. Gerbaudo, V. Halyo, P. Hebda, J. Hegeman, A. Hunt,

E. Laird, D. Lopes Pegna, P. Lujan, D. Marlow, T. Medvedeva, M. Mooney, J. Olsen,

P. Piroué, X. Quan, A. Raval, H. Saka, D. Stickland, C. Tully, J.S. Werner, A. Zuranski

University of Puerto Rico, Mayaguez, USA

J.G. Acosta, E. Brownson, X.T. Huang, A. Lopez, H. Mendez, S. Oliveros, J.E. Ramirez

Vargas, A. Zatserklyaniy

Purdue University, West Lafayette, USA

E. Alagoz, V.E. Barnes, D. Benedetti, G. Bolla, D. Bortoletto, M. De Mattia, A. Everett,

Z. Hu, M. Jones, O. Koybasi, M. Kress, A.T. Laasanen, N. Leonardo, V. Maroussov,

P. Merkel, D.H. Miller, N. Neumeister, I. Shipsey, D. Silvers, A. Svyatkovskiy, M. Vidal

Marono, H.D. Yoo, J. Zablocki, Y. Zheng

Purdue University Calumet, Hammond, USA

S. Guragain, N. Parashar

Rice University, Houston, USA

A. Adair, C. Boulahouache, V. Cuplov, K.M. Ecklund, F.J.M. Geurts, B.P. Padley,

R. Redjimi, J. Roberts, J. Zabel

University of Rochester, Rochester, USA

B. Betchart, A. Bodek, Y.S. Chung, R. Covarelli, P. de Barbaro, R. Demina, Y. Eshaq,

A. Garcia-Bellido, P. Goldenzweig, Y. Gotra, J. Han, A. Harel, S. Korjenevski, D.C. Miner,

D. Vishnevskiy, M. Zielinski

The Rockefeller University, New York, USA

A. Bhatti, R. Ciesielski, L. Demortier, K. Goulianos, G. Lungu, S. Malik, C. Mesropian

Rutgers, the State University of New Jersey, Piscataway, USA

S. Arora, A. Barker, J.P. Chou, C. Contreras-Campana, E. Contreras-Campana, D. Dug-

gan, D. Ferencek, Y. Gershtein, R. Gray, E. Halkiadakis, D. Hidas, D. Hits, C. Kilic55,

A. Lath, S. Panwalkar, M. Park, R. Patel, V. Rekovic, A. Richards, J. Robles, K. Rose,

S. Salur, S. Schnetzer, C. Seitz, S. Somalwar, R. Stone, S. Thomas

University of Tennessee, Knoxville, USA

G. Cerizza, M. Hollingsworth, S. Spanier, Z.C. Yang, A. York

Texas A&M University, College Station, USA

R. Eusebi, W. Flanagan, J. Gilmore, T. Kamon56, V. Khotilovich, R. Montalvo, I. Os-

ipenkov, Y. Pakhotin, A. Perloff, J. Roe, A. Safonov, T. Sakuma, S. Sengupta, I. Suarez,

A. Tatarinov, D. Toback

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Texas Tech University, Lubbock, USA

N. Akchurin, J. Damgov, P.R. Dudero, C. Jeong, K. Kovitanggoon, S.W. Lee, T. Libeiro,

Y. Roh, I. Volobouev

Vanderbilt University, Nashville, USA

E. Appelt, D. Engh, C. Florez, S. Greene, A. Gurrola, W. Johns, P. Kurt, C. Maguire,

A. Melo, P. Sheldon, B. Snook, S. Tuo, J. Velkovska

University of Virginia, Charlottesville, USA

M.W. Arenton, M. Balazs, S. Boutle, B. Cox, B. Francis, J. Goodell, R. Hirosky,

A. Ledovskoy, C. Lin, C. Neu, J. Wood, R. Yohay

Wayne State University, Detroit, USA

S. Gollapinni, R. Harr, P.E. Karchin, C. Kottachchi Kankanamge Don, P. Lamichhane,

A. Sakharov

University of Wisconsin, Madison, USA

M. Anderson, M. Bachtis, D. Belknap, L. Borrello, D. Carlsmith, M. Cepeda, S. Dasu,

L. Gray, K.S. Grogg, M. Grothe, R. Hall-Wilton, M. Herndon, A. Hervé, P. Klabbers,

J. Klukas, A. Lanaro, C. Lazaridis, J. Leonard, R. Loveless, A. Mohapatra, I. Ojalvo,

G.A. Pierro, I. Ross, A. Savin, W.H. Smith, J. Swanson

†: Deceased

1: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland

2: Also at National Institute of Chemical Physics and Biophysics, Tallinn, Estonia

3: Also at Universidade Federal do ABC, Santo Andre, Brazil

4: Also at California Institute of Technology, Pasadena, USA

5: Also at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France

6: Also at Suez Canal University, Suez, Egypt

7: Also at Cairo University, Cairo, Egypt

8: Also at British University, Cairo, Egypt

9: Also at Fayoum University, El-Fayoum, Egypt

10: Now at Ain Shams University, Cairo, Egypt

11: Also at Soltan Institute for Nuclear Studies, Warsaw, Poland

12: Also at Université de Haute-Alsace, Mulhouse, France

13: Now at Joint Institute for Nuclear Research, Dubna, Russia

14: Also at Moscow State University, Moscow, Russia

15: Also at Brandenburg University of Technology, Cottbus, Germany

16: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary

17: Also at Eötvös Loránd University, Budapest, Hungary

18: Also at Tata Institute of Fundamental Research - HECR, Mumbai, India

19: Now at King Abdulaziz University, Jeddah, Saudi Arabia

20: Also at University of Visva-Bharati, Santiniketan, India

21: Also at Sharif University of Technology, Tehran, Iran

22: Also at Isfahan University of Technology, Isfahan, Iran

23: Also at Shiraz University, Shiraz, Iran

– 31 –



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24: Also at Plasma Physics Research Center, Science and Research Branch, Islamic Azad

University, Teheran, Iran

25: Also at Facoltà Ingegneria Università di Roma, Roma, Italy

26: Also at Università della Basilicata, Potenza, Italy

27: Also at Università degli Studi Guglielmo Marconi, Roma, Italy

28: Also at Università degli studi di Siena, Siena, Italy

29: Also at University of Bucharest, Faculty of Physics, Bucuresti-Magurele, Romania

30: Also at Faculty of Physics of University of Belgrade, Belgrade, Serbia

31: Also at University of Florida, Gainesville, USA

32: Also at University of California, Los Angeles, Los Angeles, USA

33: Also at Scuola Normale e Sezione dell’ INFN, Pisa, Italy

34: Also at INFN Sezione di Roma; Università di Roma ”La Sapienza”, Roma, Italy

35: Also at University of Athens, Athens, Greece

36: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom

37: Also at The University of Kansas, Lawrence, USA

38: Also at Paul Scherrer Institut, Villigen, Switzerland

39: Also at Institute for Theoretical and Experimental Physics, Moscow, Russia

40: Also at Gaziosmanpasa University, Tokat, Turkey

41: Also at Adiyaman University, Adiyaman, Turkey

42: Also at The University of Iowa, Iowa City, USA

43: Also at Mersin University, Mersin, Turkey

44: Also at Kafkas University, Kars, Turkey

45: Also at Suleyman Demirel University, Isparta, Turkey

46: Also at Ege University, Izmir, Turkey

47: Also at School of Physics and Astronomy, University of Southampton, Southampton,

United Kingdom

48: Also at INFN Sezione di Perugia; Università di Perugia, Perugia, Italy

49: Also at University of Sydney, Sydney, Australia

50: Also at Utah Valley University, Orem, USA

51: Also at Institute for Nuclear Research, Moscow, Russia

52: Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences,

Belgrade, Serbia

53: Also at Argonne National Laboratory, Argonne, USA

54: Also at Erzincan University, Erzincan, Turkey

55: Now at University of Texas at Austin, Austin, USA

56: Also at Kyungpook National University, Daegu, Korea

– 32 –


	Introduction
	Physics models
	The CMS detector
	Event selection
	Signal and background simulation
	Systematic uncertainties
	Results and limits
	Summary
	The CMS collaboration