EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP/2011-035
2011/04/11
CMS-EWK-10-013
Measu emen o he Inclusi e Z C oss Sec ion ia Decays o
Tau Pai s in pp Collisions a √s=7 TeV
The CMS Collabo a ion∗
Abs ac
A measu emen o inclusi e Z →τ+τ−p oduc ion in pp collisions is p esen ed, in
he inal s a es µ+had ons, e+had ons, e+µ, and µ+µ. The da a sample co esponds
o an in eg a ed luminosi y o 36 pb−1collec ed wi h he CMS de ec o a he LHC.
The measu ed c oss sec ion is σ(pp →ZX)×B(Z→τ+τ−)=1.00 ±0.05 (s a .)±
0.08 (sys .)±0.04 (lumi.)nb, which is in good ag eemen wi h he nex - o-nex - o-
leading o de QCD p edic ion and wi h p e ious measu emen s in he Z →e+e−and
µ+µ−channels. The econs uc ion e iciency o had onic τdecays is de e mined
wi h a p ecision o 7%.
Submi ed o he Jou nal o High Ene gy Physics
∗See Appendix A o he lis o collabo a ion membe s
a Xi :1104.1617 1 [hep-ex] 8 Ap 2011
1
1 In oduc ion
The measu emen o he p oduc ion c oss sec ion o pp →ZXwi h Z →τ+τ−cons i u es
an impo an physics benchma k a he La ge Had on Collide (LHC). The τlep on can decay
ei he in o pu ely lep onic inal s a es (τ→eνeντdeno ed as “τe” o τ→µνµντdeno ed as
“τµ”) o in o had onic inal s a es deno ed by “τhad” consis ing o a had onic sys em and a ντ.
Cons ained by he τmass, he had onic sys em is cha ac e ized by a low pa icle mul iplici y
and a highly collima ed je which allows a τhad signal o be sepa a ed om he la ge QCD je
backg ounds. The alida ion o he τhad signal is essen ial in sea ches o new physics based
on τlep ons, such as Higgs boson decays o τ+τ−[1]. The Compac Muon Solenoid (CMS)
Collabo a ion ecen ly epo ed a sea ch o he Higgs boson in his channel [2]. Tau lep ons
can also be impo an signa u es o sea ches o supe symme y, ex a dimensions, and ex a
gauge bosons [3].
The Z →τ+τ−p oduc ion c oss sec ion has been p e iously measu ed in p o on-an ip o on
collisions by he CDF and D0 Collabo a ions [4, 5]. In his s udy, Z →τ+τ−e en s in he τµτhad,
τeτhad,τeτµ, and τµτµ inal s a es a e selec ed om a sample o √s=7 TeV p o on-p o on
collision da a eco ded by he CMS expe imen a he LHC. The da a sample co esponds o
an in eg a ed luminosi y o 36 ±1 pb−1. The esul s a e compa ed o p e ious measu emen s
made in he e+e−and µ+µ− inal s a es [6], p o iding a alida ion o τhad econs uc ion and
iden i ica ion [7–9] and a di ec measu emen o he au selec ion e iciency.
2 CMS De ec o
The cen al ea u e o he CMS appa a us is a supe conduc ing solenoid, o 6 m in e nal di-
ame e , p o iding a magne ic ield o 3.8 T. Wi hin he ield olume a e he silicon pixel and
s ip acke , he c ys al elec omagne ic calo ime e (ECAL) and he b ass/scin illa o had on
calo ime e (HCAL). Muons a e measu ed in gas-ioniza ion de ec o s embedded in he s eel
e u n yoke.
CMS uses a igh -handed coo dina e sys em, wi h he o igin a he nominal in e ac ion poin ,
he xaxis poin ing o he cen e o he LHC, he yaxis poin ing up pe pendicula o he LHC
plane, and he zaxis along he coun e clockwise-beam di ec ion. The pola angle θis measu ed
om he posi i e zaxis and he azimu hal angle φis measu ed in he xy plane. Va iables
used in his a icle a e he pseudo apidi y, η≡ −ln[ an(θ/2)], and he ans e se momen um,
pT=qp2
x+p2
y.
The ECAL is designed o ha e bo h excellen ene gy esolu ion and high g anula i y, which
a e c ucial o econs uc ing elec ons and pho ons p oduced in τdecays. The ECAL is con-
s uc ed wi h p ojec i e lead ungs a e c ys als in wo pseudo apidi y egions: he ba el (|η|<
1.479) and he endcap (1.479 <|η|<3). The ansi ion egions be ween he ba el and he
endcaps, 1.444 <|η|<1.567, a e no used o elec on econs uc ion. In he ba el egion,
he c ys als a e 25.8 X0long, whe e X0is he adia ion leng h, and con o m o a g anula i y
o ∆η×∆φ=0.0174 ×0.0174. The endcap egion is ins umen ed wi h a lead–silicon-s ip
p eshowe de ec o consis ing o wo o hogonal s ip de ec o s wi h a s ip pi ch o 1.9 mm.
One plane is a a dep h o 2X0and he o he a 3X0. The ECAL has an ene gy esolu ion o
be e han 0.5% o uncon e ed pho ons wi h ans e se ene gies abo e 100 GeV. The en-
e gy esolu ion is 3% o be e o he ange o elec on ene gies ele an o his analysis. The
HCAL ba el and endcap egions co e he ange |η|<3 and a e subdi ided in o owe s wi h
a segmen a ion o ∆η×∆φ=0.087 ×0.087, co esponding o 5 ×5 ECAL c ys als in he ba el
23 Lep on Recons uc ion and Iden i ica ion
egion. The HCAL o wa d egion ex ends he calo ime y o |η|<5.
The inne acke measu es cha ged pa icle acks wi hin he ange |η|<2.5. I consis s o
1 440 silicon pixel and 15 148 silicon s ip de ec o modules and p o ides an impac pa ame-
e esolu ion o ∼15 µm and a ans e se momen um esolu ion o abou 1.5% o 100 GeV
pa icles.
The muon ba el egion is co e ed by d i ubes and he endcap egions by ca hode s ip cham-
be s. In bo h egions esis i e pla e chambe s p o ide addi ional coo dina e and iming in o -
ma ion. Muons can be econs uc ed in he ange |η|<2.4, wi h a ypical pT esolu ion o 1%
o pT≈40 GeV.
A mo e de ailed desc ip ion o CMS can be ound in [10].
3 Lep on Recons uc ion and Iden i ica ion
Muons p oduced by τdecays in he Z →τ+τ−p ocess a e econs uc ed in he acke and
muon chambe s [11]. Quali y cu s, based on he minimum numbe o hi s in he silicon acke ,
pixel de ec o , and muon chambe s, a e applied o supp ess backg ounds om punch- h oughs
and decays in ligh .
Elec ons a e econs uc ed by combining acks p oduced by he Gaussian Sum Fil e algo-
i hm wi h ECAL clus e s [12]. Requi emen s a e imposed ha dis inguish p omp elec ons
om cha ged pions mimicking elec on signa u es, and om elec ons p oduced by pho on
con e sions.
The CMS pa icle low (PF) algo i hm [8] is used o o m a mu ually exclusi e collec ion o
econs uc ed pa icles (muons, elec ons, pho ons, and cha ged and neu al had ons) by com-
bining acks and calo ime e clus e s. These econs uc ed pa icles a e used o build compos-
i e objec s such as τ’s and je s, and o measu e he missing ans e se ene gy E/T.
Elec ons and muons om τdecays a e expec ed o be isola ed in he de ec o , while lep ons
om hea y- la ou (c and b) decays and decays in ligh a e expec ed o be ound inside
je s. A measu e o isola ion is used o disc imina e he signal om he QCD mul ije back-
g ound, based on he cha ged had ons, pho ons, and neu al had ons alling wi hin a cone
∆R=p∆η2+∆φ2=0.4 a ound he lep on momen um di ec ion. In he τµτµ inal s a e, a
cone o ∆R=0.3 is used. A sum o he pT o each pa icle ype is made o cha ged had ons
wi h pT>0.5 GeV and o pho ons and neu al had ons wi h pT>1 GeV; pho ons and neu al
had ons a e excluded om he sum i hey all wi hin inne cones o ∆R=0.05 and ∆R=0.08,
espec i ely. The ela i e isola ion a iable is IPF
el =Σpcha ged
T+ppho on
T+pneu al
T/p`
T, whe e
pcha ged
T,ppho on
T, and pneu al
T e e o he cha ged had ons, pho ons, and neu al had ons in he
sum, espec i ely, and p`
T e e s o he pTo he lep on `=e, µ. Fo muons, i is equi ed ha
IPF
el <0.1, while o elec ons i is equi ed ha IPF
el <0.08 in he ba el and IPF
el <0.04 in
he endcaps. A simila o mula is used o he τeτµ inal s a e bu wi h he isola ion quan i ies
based di ec ly on acke and calo ime e in o ma ion, calcula ed in a cone o ∆R=0.3. In his
case, i is equi ed ha I el <0.15 o muons and I el <0.1 o elec ons.
The τhad iden i ica ion algo i hm used in his measu emen is known as he Had ons Plus S ips
algo i hm [9], which s a s om a high-pTcha ged had on and combines i wi h o he nea by
cha ged o neu al had ons o econs uc τdecay modes. The iden i ica ion o π0mesons
is enhanced by clus e ing elec ons and pho ons in ”s ips” along he bending plane o ake
in o accoun possible b oadening o calo ime e signa u es by pho on con e sions. To educe
3
he con amina ion om QCD je s, he τhad-candida e isola ion is calcula ed in a cone o ∆R=
0.5 a ound he econs uc ed τ-momen um di ec ion. I is eques ed ha he e be no cha ged
had ons wi h pT>1.0 GeV and no pho ons wi h ET>1.5 GeV in he isola ion cone, o he han
he τcons i uen s.
4 E en Selec ion
The e en s p eselec ed o his analysis in he τµτhad,τeτµ, and τµτµ inal s a es a e equi ed
o pass he single-muon Le el-1 (L1) igge wi h a pT h eshold o 7 GeV and he single muon
High Le el T igge (HLT) [13], wi h a h eshold a ying om 9 GeV o 15 GeV, depending on
he ins an aneous luminosi y. E en s in he τeτhad inal s a e a e selec ed using he single-
elec on L1 igge wi h a h eshold o 8 GeV in he ans e se ene gy, and a single-elec on
HLT igge wi h a h eshold o 12 GeV a highe ins an aneous luminosi y. A he end o he
2010 da a aking pe iod, a combined e+τ igge was used in o de o keep he a e low enough
wi hou a u he inc ease o he elec on h eshold. The igge has he same L1 equi emen s
as he elec on igge , bu he HLT equi es he p esence o an elec on o ans e se ene gy
la ge han 12 GeV and a had onic au decay wi h pTla ge han 15 GeV, agged wi h a sim-
pli ied e sion o he au econs uc ion algo i hm wi h a less es ic i e selec ion han he one
used in he o line analysis.
O line e en selec ion s a s wi h he equi emen o a well-de ined p ima y e ex [14]. Fo
he τµτhad and τeτhad inal s a es, one isola ed muon o elec on is equi ed wi h pT>15 GeV
and |η|<2.1. The associa ed τhad mus be opposi ely cha ged, wi h pT>20 GeV and |η|<2.3.
In o de o ejec e en s coming om he W+je s backg ound, he ans e se mass o he lep on
and he E/T,MT(`,E/T) = q2p`
TE/T·(1−cos ∆φ), is equi ed o be less han 40 GeV, whe e ∆φ
is he di e ence in azimu hal angle be ween he lep on and E/T ec o s. The MTdis ibu ion
and he selec ion equi emen applied a e illus a ed in Fig. 1 (le ) o he τµτhad inal s a e.
Fo he τeτµ inal s a e, one isola ed muon wi h |η|<2.1 and one opposi ely cha ged isola ed
elec on wi h |η|<2.4 a e equi ed, bo h wi h pT>15 GeV. Fu he backg ound supp ession
is achie ed by equi ing MT(µ,E/T)<50 GeV and MT(e, E/T)<50 GeV.
Fo he τµτµ inal s a e, e en s wi h wo opposi ely cha ged isola ed muons wi h |η|<2.1 a e
selec ed i one sa is ies pT>19 GeV and he o he pT>10 GeV. The equi emen E/T<50 GeV
supp esses and W+je s backg ounds, and a equi emen on he azimu hal angle di e ence
be ween he muons, ∆φµµ >2, ejec s QCD backg ound e en s, o muons o igina ing om he
same qua konia decay o om a decay chain o hea y- la ou had ons. E ec i e supp ession
o he D ell–Yan backg ound is achie ed wi h a mul i a ia e likelihood a io echnique. Fo
each e en , he ela i e p obabili ies o belong o wo e en classes (Z →τ+τ−→τµτµand
Z/γ∗→µ+µ−) a e compu ed, exploi ing he ollowing se o disc imina ing a iables: he
a io o he ans e se momen um o he dimuon sys em o he scala sum o he momen a
o he wo muons; he signi icance o he dis ance o closes app oach (DCA) be ween he wo
muon helix acks; he pseudo apidi y o he dimuon sys em; and he azimu hal angle be ween
he posi i e muon momen um and E/T. A no malized likelihood disc iminan is compu ed and
is shown in Fig. 1 ( igh ). E en s wi h a likelihood disc iminan alue la ge han 0.87 a e kep
in he inal sample.
Fo he plo s in Fig. 1, he QCD mul ije , W and diboson backg ounds we e simula ed wi h
PYTHIA [15], he D ell–Yan signal and backg ound wi h he nex - o-leading o de (NLO)
Mon e Ca lo gene a o POWHEG [16–18], and he op samples wi h Madg aph [19]. The au
decays we e pe o med wi h Tauola [20]. The samples we e no malized using he c oss sec ion

45 Backg ound Es ima ion
) [GeV]
T
E, µ(
T
M
0 20 40 60 80 100 120
E en s / (10 GeV)
0
50
100
150
200
250
300
da a ττ → Z
W+je s
EWK+
QCD
CMS
= 7 TeVs a
-1
36 pb
had
τ
µ
τ → ττ →Z
No malized Likelihood
0 0.2 0.4 0.6 0.8 1
E en s / 0.05
1
10
2
10
3
10
4
10
5
10 da a µµ →* γ Z/
ττ → Z νµ → W
QCD
CMS
= 7 TeVs a
-1
36 pb
µ
τ
µ
τ → ττ →Z
Figu e 1: Muon+E/T ans e se mass (le ) o he τµτhad inal s a e. Likelihood disc iminan
( igh ) o he τµτµ inal s a e. The a ows show he inal selec ion c i e ia applied.
a nex - o-nex - o-leading o de (NNLO) o D ell–Yan and W, a leading o de (LO) o QCD,
and NLO o he sample. The EWK label in he igu e e e s o he Z →e+e−,µ+µ−, and
diboson backg ounds.
5 Backg ound Es ima ion
The Z →τ+τ−signal is es ablished using he isible mass, which is he econs uc ed mass
o he `τhad sys em in he τ`τhad inal s a es, and he dilep on in a ian mass o he τeτµand
τµτµ inal s a es. Due o he p esence o neu inos in he inal s a e, he Z →τ+τ− isible mass
peak ex ends ac oss he ange 30–100 GeV, which is conside ably b oade han he Z esonance
i sel . The backg ounds gene ally span he same mass ange, so an accu a e de e mina ion o
he signal yield equi es e ec i e backg ound es ima ion echniques. The main backg ound
sou ces a e QCD mul ije p ocesses, W+je s, and Z →`+`−, wi h small con ibu ions om
op-qua k decays and dibosons. All backg ounds a e measu ed in con ol egions whe e hei
con ibu ions a e enhanced and ex apola ed o he signal selec ion egion using selec ion e i-
ciencies de e mined ei he om da a o he Mon e Ca lo simula ion. In he τ`τhad inal s a e, he
QCD mul ije backg ound is es ima ed using samples o same-sign (SS) and opposi e-sign (OS)
e en s om da a, o which he elec on o muon isola ion equi emen is in e ed; he QCD
backg ound es ima e is based on he a io o OS o SS yields. The isible mass dis ibu ion o
he SS e en s is used o desc ibe he backg ound in he signal egion. The W con ibu ion is
ex ac ed om he egion MT(`,E/T)>60 GeV, whe e i domina es he sample. In he τeτµ inal
s a e, he backg ound con ibu ions a e expec ed o be small and a e es ima ed om he simu-
la ion. The la ge- ans e se-mass egion is used o check he es ima ed backg ound con ibu-
ions om W, diboson, and backg ounds. Fo he τµτµ inal s a e, he D ell–Yan muon-pai
p oduc ion e en s a e selec ed wi h a educed likelihood wi hou including he muon DCA
signi icance, and he esul ing muon DCA signi icance dis ibu ion is i ed wi h signal and
backg ound shapes. The QCD mul ije backg ound es ima e is ob ained om a sample o SS
dimuon e en s.
The numbe s o selec ed e en s and he expec ed backg ound con ibu ions a e summa ized in
Table 1. The s a is ical and sys ema ic unce ain ies in he me hods used a e also gi en, whe e
5
he unce ain ies a e added in quad a u e.
Table 1: Numbe s o expec ed backg ound e en s and numbe o da a e en s passing all he
selec ion c i e ia in he ou inal s a es. The unce ain ies shown include he s a is ical and
sys ema ic unce ain ies added in quad a u e.
τµτhad τeτhad τeτµτµτµ
(Mµµ <70 GeV)
Z→`+`−, je misiden i ied as τ6.4 ±2.4 15.0 ±6.2 -
Z→`+`−, lep on misiden i ied as τ12.9 ±3.5 109 ±28 2.4 ±0.3 20.1 ±1.3
6.0 ±3.0 2.6 ±1.3 7.1 ±1.3 0.15 ±0.03
W→`ν54.9 ±4.8 30.6 ±3.1
W→τν 14.7 ±1.3 7.0 ±0.7 1.5 ±0.5 2.5 ±2.5
QCD mul ije 132 ±14 181 ±23
WW/WZ/ZZ 1.6 ±0.8 0.8 ±0.4 3.0 ±0.4 -
To al backg ound 228 ±16 346 ±37 14.0 ±1.8 22.8 ±2.8
To al da a 517 540 101 58
6 Sys ema ic Unce ain ies
The e iciencies o elec on and muon econs uc ion, iden i ica ion, and isola ion, as well as
he igge e iciencies a e ob ained om da a. Co ec ion ac o s o he alues ex ac ed om
he simula ion a e de e mined using he me hod desc ibed in Re . [6] ( ag-and-p obe me hod).
The measu ed e iciencies ha e a small dependence on pTand co e he ull ange o pTused
in he analysis. The unce ain ies on he co ec ion ac o s a e in he ange o 0.2–1.1%.
A simila echnique is used o es ima e he had onic au iden i ica ion e iciency. A da a sam-
ple o aus is selec ed using Z →τ+τ−→τµτhad e en s. The e en s a e p eselec ed wi hou
applying he ull au iden i ica ion bu only kinema ic cu s and a se o equi emen s o sup-
p ess he backg ound om Z →µ+µ−, W, and QCD e en s. The e iciency is hen calcula ed
as a a io o he numbe o e en s ha pass he au iden i ica ion equi emen o he numbe
o all p eselec ed e en s. The o al unce ain y o he measu emen a ises om he s a is ical
unce ain y o he sample and he sys ema ic unce ain ies ela ed o he unde s anding o he
backg ounds in he p eselec ion sample and amoun s o 23% [9].
To es ima e he e iciency o he MTselec ion and he likelihood selec ion e iciency o he τµτµ
inal s a e, an embedded sample is used whe e he muons in a Z →µ+µ−da a sample a e
eplaced by simula ed au decays wi h he o iginal muon momen um. The es ima ed unce -
ain ies amoun o 2%.
To es ima e he e ec o he ene gy-scale unce ain ies on he accep ance, he ene gy o all
econs uc ed objec s (elec ons, muons, aus, and je s) is a ied wi hin hei espec i e un-
ce ain y. A e each independen shi , he missing ans e se ene gy is ecalcula ed and he
e en selec ion is epea ed. The e en yield is compa ed o he nominal alue and he ela i e
di e ence is quo ed as he sys ema ic unce ain y. The sys ema ic unce ain ies a e in he ange
om 1% o 3.5%.
To ob ain he accep ance co ec ions, he D6T and Z2 PYTHIA unes [21] we e used in he
simula ion. The e ec o he use o di e en unes on he inal ex ac ed c oss sec ion is smalle
han 1% and is no included in he sys ema ic unce ain ies.
67 C oss Sec ion Measu emen
The main sou ce o heo e ical unce ain y in he calcula ion o he expe imen al accep ance
comes om he pa on dis ibu ion unc ions (PDFs). The cen al accep ance alue is ob ained
wi h he CT10 PDF [22]. The unce ain y is es ima ed using he e o se s o he PDFs: CT10,
MSTW2008NLO [23], and NNPDF2.0 [24], and amoun s o 2%.
The expe imen al and heo e ical unce ain ies a e summa ized in Table 2.
Table 2: Summa y o he sou ces o sys ema ic unce ain ies and hei es ima ed e ec on he
measu ed Z →τ+τ−c oss sec ion.
Sou ce τµτhad τeτhad τeτµτµτµ
T igge 0.2% 3% 0.2% 0.3%
Lep on iden i ica ion and isola ion 1.0% 1.1% 1% 1%
τhad iden i ica ion 23% -
E iciency o MTselec ion 2% -
Likelihood selec ion e iciency - 2%
Accep ance due o τhad ene gy scale, 3% 3.5% -
Accep ance due o e ene gy scale, 2% - 1.6% 1.6% -
Accep ance due o µmomen um scale, 1% 1% - 1% 2%
Luminosi y 4%
Pa on dis ibu ion unc ions 2%
7 C oss Sec ion Measu emen
The c oss sec ion is ob ained o each inal s a e wi h he ollowing o mula:
σ(pp →ZX)×B(Z→τ+τ−) = N
AeB0L, (1)
whe e Nis he numbe o ex ac ed signal e en s, Ais he accep ance o signal e en s, eis he
signal selec ion e iciency, B0is he b anching ac ion o he τ-decay mode conside ed [25], and
Lis he in eg a ed luminosi y [26].
The isible mass dis ibu ions o he τµτhad,τeτhad,τeτµand τµτµ inal s a es a e shown in Fig. 2.
To ex ac he signal, a i is pe o med using he isible mass shapes om he simula ion, ex-
cep o he QCD mul ije and Z →`+`−backg ounds, which a e ob ained om da a. Fo he
simula ion shapes, a a ia ion o he elec on and au ene gy scales wi hin hei unce ain ies is
conside ed. The e ec o he muon ene gy scale is negligible. The backg ound no maliza ions
co espond o he numbe s lis ed in Table 1 and a e allowed o a y wi hin he es ima ed un-
ce ain ies. The backg ound yields and signal shapes shown in Fig. 2 a e hose ob ained om
he i ing p ocedu e.
Table 3: Accep ance, selec ion e iciency and ac ion o selec ed e en s ou side he gene a o -
le el mass window o he ou inal s a es conside ed.
τµτhad τeτhad τeτµτµτµ
Accep ance A0.13 0.12 0.074 0.16
Selec ion e iciency e0.37 0.23 0.55 0.17
Mass window co ec ion ou 0.03 0.03 0.02 0.01
7
Visible Mass [GeV]
0 50 100 150 200
E en s / (10 GeV)
0
50
100
150
da a ττ → Z EWK+
QCD
yields om i
CMS
= 7 TeVs a
-1
36 pb
had
τ
µ
τ → ττ →Z
Visible Mass [GeV]
0 50 100 150 200
E en s / (10 GeV)
0
50
100
150
da a ττ → Z EWK+
QCD
yields om i
CMS
= 7 TeVs a
-1
36 pb
had
τ
e
τ → ττ →Z
In a ian Mass [GeV]µe-
0 50 100 150 200
E en s / (10 GeV)
0
10
20
30
40
50
da a ττ → Z EWK+
QCD
yields om i
CMS
= 7 TeVs a
-1
36 pb
µ
τ
e
τ → ττ →Z
In a ian Mass [GeV]µ-µ
0 50 100 150 200
E en s / (10 GeV)
1
10
2
10
3
10
da a ττ → Z µµ →* γ Z/
QCD
yields om i
CMS
= 7 TeVs a
-1
36 pb
µ
τ
µ
τ → ττ →Z
Figu e 2: Visible mass dis ibu ions o he τµτhad ( op le ), τeτhad ( op igh ), τeτµ(bo om le ),
and τµτµ(bo om igh ) inal s a es.
The accep ances we e ob ained wi h he NLO QCD p og am POWHEG in he Z →τ+τ−mass
egion 60 <Mτ+τ−<120 GeV. Table 3 shows he accep ances and he selec ion e iciencies
o he di e en inal s a es conside ed. The numbe o ex ac ed e en s om he i , N i , is
co ec ed o he ac ion o signal e en s ou side he gene a o -le el mass window, ou , whe e
N=N i ·(1− ou )in Eq. 1. The co ec ion ac o s used a e also shown in Table 3.
The measu ed alues o he c oss sec ion om he ou inal s a es conside ed a e shown in
Table 4, whe e he unce ain ies shown a e due o s a is ical, sys ema ic, in eg a ed luminosi y
and τiden i ica ion unce ain ies.
The measu ed alues a e compa ible wi h each o he and wi h he NNLO heo e ical p edic-
ion, 0.972 ±0.042 nb [27]. They a e also consis en wi h he CMS measu emen based on
Z→e+e−,µ+µ−e en s [6].
The dominan unce ain y on he Z →τ+τ−c oss sec ion measu emen comes om he τhad
econs uc ion and iden i ica ion e iciency. A simul aneous i o all ou inal s a es is pe -
o med o ob ain he c oss sec ion and a scale ac o o he τhad e iciency, which is he a io
o he e iciency in he da a o ha in he simula ion. The esul o he global i is shown in
14 A The CMS Collabo a ion
Uni e si y o So ia, So ia, Bulga ia
A. Dimi o , R. Hadjiiska, A. Ka adzhino a, V. Kozhuha o , L. Li o , M. Ma ee , B. Pa lo ,
P. Pe ko
Ins i u e o High Ene gy 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
S a e Key Lab. o Nucl. Phys. and Tech., Peking Uni e si y, Beijing, China
Y. Ban, S. Guo, Y. Guo, W. Li, Y. Mao, S.J. Qian, H. Teng, L. Zhang, B. Zhu, W. Zou
Uni e sidad de Los Andes, Bogo a, Colombia
A. Cab e a, B. Gomez Mo eno, A.A. Ocampo Rios, A.F. Oso io Oli e os, J.C. Sanab ia
Technical Uni e si y o Spli , Spli , C oa ia
N. Godino ic, D. Lelas, K. Lelas, R. Ples ina3, D. Polic, I. Puljak
Uni e si y o Spli , Spli , C oa ia
Z. An uno ic, M. Dzelalija
Ins i u e Rudje Bosko ic, Zag eb, C oa ia
V. B iglje ic, S. Du ic, K. Kadija, S. Mo o ic
Uni e si y o Cyp us, Nicosia, Cyp us
A. A ikis, M. Galan i, J. Mousa, C. Nicolaou, F. P ochos, P.A. Razis
Cha les Uni e si y, P ague, Czech Republic
M. Finge , M. Finge J .
Academy o Scien i ic Resea ch and Technology o he A ab Republic o Egyp , Egyp ian
Ne wo k o High Ene gy Physics, Cai o, Egyp
Y. Ass an4, S. Khalil5, M.A. Mahmoud6
Na ional Ins i u e o Chemical Physics and Biophysics, Tallinn, Es onia
A. Hek o , M. Kadas ik, M. M¨
un el, M. Raidal, L. Rebane
Depa men o Physics, Uni e si y o Helsinki, Helsinki, Finland
V. Azzolini, P. Ee ola, G. Fedi
Helsinki Ins i u e o Physics, Helsinki, Finland
S. Czella , J. H¨
a k¨
onen, A. Heikkinen, V. Ka im¨
aki, R. Kinnunen, M.J. Ko elainen, T. Lamp´
en,
K. Lassila-Pe ini, S. Leh i, T. Lind´
en, P. Luukka, T. M¨
aenp¨
a¨
a, E. Tuominen, J. Tuominiemi,
E. Tuo inen, D. Unga o, L. Wendland
Lappeen an a Uni e si y o Technology, Lappeen an a, Finland
K. Banzuzi, A. Ko pela, T. Tuu a
Labo a oi e d’Annecy-le-Vieux de Physique des Pa icules, IN2P3-CNRS, Annecy-le-Vieux,
F ance
D. Sillou
DSM/IRFU, CEA/Saclay, Gi -su -Y e e, F ance
M. Besancon, S. Choudhu y, M. Deja din, D. Deneg i, B. Fabb o, J.L. Fau e, F. Fe i, S. Ganjou ,
F.X. Gen i , A. Gi e naud, P. G as, G. Hamel de Monchenaul , P. Ja y, E. Locci, J. Malcles,
M. Ma ionneau, L. Millische , J. Rande , A. Rosowsky, I. Sh eybe , M. Ti o , P. Ve ecchia

15
Labo a oi e Lep ince-Ringue , Ecole Poly echnique, IN2P3-CNRS, Palaiseau, F ance
S. Ba ioni, F. Beaude e, L. Benhabib, L. Bianchini, M. Bluj7, C. B ou in, P. Busson, C. Cha lo ,
T. Dahms, L. Dob zynski, S. Elgammal, R. G anie de Cassagnac, M. Haguenaue , P. Min´
e,
C. Mi ono , C. Ochando, P. Paganini, D. Sabes, R. Sale no, Y. Si ois, C. Thiebaux, B. Wyslouch8,
A. Zabi
Ins i u Plu idisciplinai e Hube Cu ien, Uni e si ´e de S asbou g, Uni e si ´e de Hau e
Alsace Mulhouse, CNRS/IN2P3, S asbou g, F ance
J.-L. Ag am9, J. And ea, D. Bloch, D. Bodin, J.-M. B om, M. Ca daci, E.C. Chabe , C. Colla d,
E. Con e9, F. D ouhin9, C. Fe o, J.-C. Fon aine9, D. Gel´
e, U. Goe lach, S. G ede , P. Juillo ,
M. Ka im9, A.-C. Le Bihan, Y. Mikami, P. Van Ho e
Cen e de Calcul de l’Ins i u Na ional de Physique Nucleai e e de Physique des
Pa icules (IN2P3), Villeu banne, F ance
F. Fassi, D. Me cie
Uni e si ´e de Lyon, Uni e si ´e Claude Be na d Lyon 1, CNRS-IN2P3, Ins i u de Physique
Nucl´eai e de Lyon, Villeu banne, F ance
C. Ba y, S. Beauce on, N. Beaupe e, M. Bedjidian, O. Bondu, G. Boudoul, D. Boumediene,
H. B un, R. Chie ici, D. Con a do, P. Depasse, H. El Mamouni, J. Fay, S. Gascon, B. Ille, T. Ku ca,
T. Le G and, M. Le huillie , L. Mi abi o, S. Pe ies, V. So dini, S. Tosi, Y. Tschudi, P. Ve die
Ins i u e o High Ene gy Physics and In o ma iza ion, Tbilisi S a e Uni e si y, Tbilisi,
Geo gia
D. Lomidze
RWTH Aachen Uni e si y, I. Physikalisches Ins i u , Aachen, Ge many
G. Anagnos ou, M. Edelho , L. Feld, N. He acleous, O. Hind ichs, R. Jussen, K. Klein, J. Me z,
N. Moh , A. Os apchuk, A. Pe ieanu, F. Raupach, J. Samme , S. Schael, D. Sp enge , H. Webe ,
M. Webe , B. Wi me
RWTH Aachen Uni e si y, III. Physikalisches Ins i u A, Aachen, Ge many
M. A a, W. Bende , E. Die z-Lau sonn, M. E dmann, J. F angenheim, T. Hebbeke ,
A. Hinzmann, K. Hoep ne , T. Klimko ich, D. Klingebiel, P. K euze , D. Lanske†, C. Magass,
M. Me schmeye , A. Meye , P. Papacz, H. Pie a, H. Rei hle , S.A. Schmi z, L. Sonnenschein,
J. S eggemann, D. Teyssie , M. Tonu i
RWTH Aachen Uni e si y, III. Physikalisches Ins i u B, Aachen, Ge many
M. Bon enackels, M. Da ids, M. Duda, G. Fl¨
ugge, H. Geenen, M. Gi els, W. Haj Ahmad,
D. Heydhausen, T. K ess, Y. Kuessel, A. Linn, A. Nowack, L. Pe challa, O. Poo h, J. Renne eld,
P. Saue land, A. S ahl, M. Thomas, D. To nie , M.H. Zoelle
Deu sches Elek onen-Synch o on, Hambu g, Ge many
M. Aldaya Ma in, W. Beh enho , U. Beh ens, M. Be gholz10, A. Be hani, K. Bo as, A. Caki ,
A. Campbell, E. Cas o, D. Dammann, G. Ecke lin, D. Ecks ein, A. Flossdo , G. Flucke,
A. Geise , J. Hauk, H. Jung1, M. Kasemann, I. Ka ko 11, P. Ka sas, C. Kleinwo , H. Kluge,
A. Knu sson, M. K ¨
ame , D. K ¨
ucke , E. Kuzne so a, W. Lange, W. Lohmann10, R. Mankel,
M. Ma ien eld, I.-A. Melze -Pellmann, A.B. Meye , J. Mnich, A. Mussgille , J. Olzem, D. Pi zl,
A. Raspe eza, A. Ra al, M. Rosin, R. Schmid 10, T. Schoe ne -Sadenius, N. Sen, A. Spi idono ,
M. S ein, J. Tomaszewska, R. Walsh, C. Wissing
Uni e si y o Hambu g, Hambu g, Ge many
C. Au e mann, V. Blobel, S. Bob o skyi, J. D aege , H. Ende le, U. Gebbe , K. Kaschube,
G. Kaussen, R. Klanne , J. Lange, B. Mu a, S. Naumann-Emme, F. Nowak, N. Pie sch, C. Sande ,
16 A The CMS Collabo a ion
H. Sche le , P. Schlepe , M. Sch ¨
ode , T. Schum, J. Schwand , H. S adie, G. S einb ¨
uck,
J. Thomsen
Ins i u ¨u Expe imen elle Ke nphysik, Ka ls uhe, Ge many
C. Ba h, J. Baue , V. Buege, T. Chwalek, W. De Boe , A. Die lamm, G. Di kes, M. Feind ,
J. G uschke, C. Hacks ein, F. Ha mann, M. Hein ich, H. Held, K.H. Ho mann, S. Honc,
J.R. Koma agi i, T. Kuh , D. Ma schei, S. Muelle , Th. M¨
ulle , M. Niegel, O. Obe s , A. Oehle ,
J. O , T. Pei e , D. Pipa o, G. Quas , K. Rabbe z, F. Ra niko , N. Ra niko a, M. Renz, C. Saou ,
A. Scheu e , P. Schie e decke , F.-P. Schilling, M. Schmanau, G. Scho , H.J. Simonis, F.M. S obe ,
D. T oendle, J. Wagne -Kuh , T. Weile , M. Zeise, V. Zhuko 11, E.B. Zieba h
Ins i u e o Nuclea Physics ”Demok i os”, Aghia Pa aske i, G eece
G. Daskalakis, T. Ge alis, K. Ka a asoulis, S. Kesisoglou, A. Ky iakis, D. Loukas, I. Manolakos,
A. Ma kou, C. Ma kou, C. Ma omma is, E. N oma i, E. Pe akou
Uni e si y o A hens, A hens, G eece
L. Gouskos, T.J. Me zimekis, A. Panagio ou, E. S ilia is
Uni e si y o Io´annina, Io´annina, G eece
I. E angelou, C. Foudas, P. Kokkas, N. Man hos, I. Papadopoulos, V. Pa as, F.A. T ian is
KFKI Resea ch Ins i u e o Pa icle and Nuclea Physics, Budapes , Hunga y
A. A anyi, G. Bencze, L. Boldizsa , C. Hajdu1, P. Hidas, D. Ho a h12, A. Kapusi, K. K ajcza 13,
F. Sikle 1, G.I. Ve es13, G. Vesz e gombi13
Ins i u e o Nuclea Resea ch ATOMKI, Deb ecen, Hunga y
N. Beni, J. Molna , J. Palinkas, Z. Szillasi, V. Veszp emi
Uni e si y o Deb ecen, Deb ecen, Hunga y
P. Raics, Z.L. T ocsanyi, B. Uj a i
Panjab Uni e si y, Chandiga h, India
S. Bansal, S.B. Be i, V. Bha naga , N. Dhing a, R. Gup a, M. Jindal, M. Kau , J.M. Kohli,
M.Z. Meh a, N. Nishu, L.K. Saini, A. Sha ma, A.P. Singh, J.B. Singh, S.P. Singh
Uni e si y o Delhi, Delhi, India
S. Ahuja, S. Bha acha ya, B.C. Choudha y, P. Gup a, S. Jain, S. Jain, A. Kuma , K. Ranjan,
R.K. Shi pu i
Bhabha A omic Resea ch Cen e, Mumbai, India
R.K. Choudhu y, D. Du a, S. Kailas, V. Kuma , A.K. Mohan y1, L.M. Pan , P. Shukla
Ta a Ins i u e o Fundamen al Resea ch - EHEP, Mumbai, India
T. Aziz, M. Guchai 14, A. Gu u, M. Mai y15, D. Majumde , G. Majumde , K. Mazumda ,
G.B. Mohan y, A. Saha, K. Sudhaka , N. Wick amage
Ta a Ins i u e o Fundamen al Resea ch - HECR, Mumbai, India
S. Bane jee, S. Dugad, N.K. Mondal
Ins i u e o Resea ch and Fundamen al Sciences (IPM), Teh an, I an
H. A aei, H. Bakhshiansohi16, S.M. E esami, A. Fahim16, M. Hashemi, A. Ja a i16, M. Khakzad,
A. Mohammadi17, M. Mohammadi Naja abadi, S. Pak ina Mehdiabadi, B. Sa a zadeh,
M. Zeinali18
INFN Sezione di Ba i a, Uni e si `a di Ba i b, Poli ecnico di Ba i c, Ba i, I aly
M. Abb esciaa,b, L. Ba bonea,b, C. Calab iaa,b, A. Colaleoa, D. C eanzaa,c, N. De Filippisa,c,1,
17
M. De Palmaa,b, L. Fio ea, G. Iasellia,c, L. Lusi oa,b, G. Maggia,c, M. Maggia, N. Mannaa,b,
B. Ma angellia,b, S. Mya,c, S. Nuzzoa,b, N. Paci icoa,b, G.A. Pie oa, A. Pompilia,b, G. Pugliesea,c,
F. Romanoa,c, G. Rosellia,b, G. Sel aggia,b, L. Sil es isa, R. T en aduea, S. Tuppu ia,b, G. Zi oa
INFN Sezione di Bologna a, Uni e si `a di Bologna b, Bologna, I aly
G. Abbiendia, A.C. Ben enu ia, D. Bonaco sia, S. B aiban -Giacomellia,b, L. B igliado ia,
P. Capiluppia,b, A. Cas oa,b, F.R. Ca alloa, M. Cu iania,b, G.M. Dalla allea, F. Fabb ia,
A. Fan ania,b, D. Fasanellaa, P. Giacomellia, M. Giun aa, C. G andia, S. Ma cellinia, G. Mase i,
M. Meneghellia,b, A. Mon ana ia, F.L. Na a iaa,b, F. Odo icia, A. Pe o aa, F. P ima e aa,
A.M. Rossia,b, T. Ro ellia,b, G. Si olia,b
INFN Sezione di Ca ania a, Uni e si `a di Ca ania b, Ca ania, I aly
S. Albe goa,b, G. Cappelloa,b, M. Chio bolia,b,1, S. Cos aa,b, A. T icomia,b, C. Tu ea
INFN Sezione di Fi enze a, Uni e si `a di Fi enze b, Fi enze, I aly
G. Ba baglia, V. Ciullia,b, C. Ci ininia, R. D’Alessand oa,b, E. Foca dia,b, S. F osalia,b, E. Galloa,
S. Gonzia,b, P. Lenzia,b, M. Meschinia, S. Paole ia, G. Sguazzonia, A. T opianoa,1
INFN Labo a o i Nazionali di F asca i, F asca i, I aly
L. Benussi, S. Bianco, S. Cola anceschi19, F. Fabb i, D. Piccolo
INFN Sezione di Geno a, Geno a, I aly
P. Fabb ica o e, R. Musenich
INFN Sezione di Milano-Biccoca a, Uni e si `a di Milano-Bicocca b, Milano, I aly
A. Benagliaa,b, F. De Guioa,b,1, L. Di Ma eoa,b, A. Ghezzia,b, S. Mal ezzia, A. Ma ellia,b,
A. Massi onia,b, D. Menascea, L. Mo onia, M. Paganonia,b, D. Ped inia, S. Ragazzia,b,
N. Redaellia, S. Salaa, T. Taba elli de Fa isa,b, V. Tancinia,b
INFN Sezione di Napoli a, Uni e si `a di Napoli ”Fede ico II” b, Napoli, I aly
S. Buon empoa, C.A. Ca illo Mon oyaa,1, N. Ca alloa,20, A. De Cosaa,b, F. Fabozzia,20,
A.O.M. Io ioa,1, L. Lis aa, M. Me olaa,b, P. Paoluccia
INFN Sezione di Pado a a, Uni e si `a di Pado a b, Uni e si `a di T en o (T en o) c, Pado a,
I aly
P. Azzia, N. Bacche aa, P. Bellana,b, A. B ancaa, R. Ca lina,b, P. Checchiaa, M. De
Ma iaa,b, T. Do igoa, U. Dossellia, F. Gaspa inia,b, U. Gaspa inia,b, A. Kaminskiya,b,11,
S. Lacap a aa,21, I. Lazzizze aa,c, M. Ma gonia,b, M. Mazzuca oa, A.T. Meneguzzoa,b,
M. Nespoloa,1, M. Passaseoa, L. Pe ozzia,1, N. Pozzobona,b, P. Ronchesea,b, F. Simone oa,b,
E. To assaa, M. Tosia,b, S. Vaninia,b, S. Ven u aa, P. Zo oa,b
INFN Sezione di Pa ia a, Uni e si `a di Pa ia b, Pa ia, I aly
P. Baessoa,b, U. Be zanoa, S.P. Ra ia,b, C. Ricca dia,b, P. To ea,b, P. Vi uloa,b, C. Vi iania,b
INFN Sezione di Pe ugia a, Uni e si `a di Pe ugia b, Pe ugia, I aly
M. Biasinia,b, G.M. Bileia, B. Capone ia,b, L. Fan`
oa,b, P. La icciaa,b, A. Luca onia,b,1,
G. Man o ania,b, M. Menichellia, A. Nappia,b, F. Romeoa,b, A. San occhiaa,b, S. Ta onia,b,1,
M. Valda aa,b
INFN Sezione di Pisa a, Uni e si `a di Pisa b, Scuola No male Supe io e di Pisa c, Pisa, I aly
P. Azzu ia,c, G. Bagliesia, J. Be na dinia,b, T. Boccalia,1, G. B occoloa,c, R. Cas aldia,
R.T. D’Agnoloa,c, R. Dell’O soa, F. Fio ia,b, L. Fo`
aa,c, A. Giassia, A. K aana, F. Ligabuea,c,
T. Lom adzea, L. Ma inia,22, A. Messineoa,b, F. Pallaa, G. Segne ia, A.T. Se bana, P. Spagnoloa,
R. Tenchinia, G. Tonellia,b,1, A. Ven u ia,1, P.G. Ve dinia
18 A The CMS Collabo a ion
INFN Sezione di Roma a, Uni e si `a di Roma ”La Sapienza” b, Roma, I aly
L. Ba onea,b, F. Ca alla ia, D. Del Rea,b, E. Di Ma coa,b, M. Diemoza, D. F ancia,b, M. G assia,1,
E. Longoa,b, S. Nou bakhsha, G. O gan inia,b, F. Pandol ia,b,1, R. Pa ama ia, S. Raha loua,b
INFN Sezione di To ino a, Uni e si `a di To ino b, Uni e si `a del Piemon e O ien ale (No-
a a) c, To ino, I aly
N. Amapanea,b, R. A cidiaconoa,c, S. A gi oa,b, M. A neodoa,c, C. Biinoa, C. Bo aa,b,1,
N. Ca igliaa, R. Cas elloa,b, M. Cos aa,b, N. Dema iaa, A. G azianoa,b,1, C. Ma io ia,
M. Ma onea,b, S. Masellia, E. Miglio ea,b, G. Milaa,b, V. Monacoa,b, M. Musicha,b,
M.M. Obe inoa,c, N. Pas onea, M. Pelliccionia,b, A. Rome oa,b, M. Ruspaa,c, R. Sacchia,b,
V. Solaa,b, A. Solanoa,b, A. S aianoa, A. Vilela Pe ei aa,b
INFN Sezione di T ies e a, Uni e si `a di T ies e b, T ies e, I aly
S. Bel o ea, F. Cossu ia, G. Della Riccaa,b, B. Gobboa, D. Mon aninoa,b, A. Penzoa
Kangwon Na ional Uni e si y, Chunchon, Ko ea
S.G. Heo, S.K. Nam
Kyungpook Na ional Uni e si y, Daegu, Ko ea
S. Chang, J. Chung, D.H. Kim, G.N. Kim, J.E. Kim, D.J. Kong, H. Pa k, S.R. Ro, D. Son, D.C. Son,
T. Son
Chonnam Na ional Uni e si y, Ins i u e o Uni e se and Elemen a y Pa icles, Kwangju,
Ko ea
Ze o Kim, J.Y. Kim, S. Song
Ko ea Uni e si y, Seoul, Ko ea
S. Choi, B. Hong, M.S. Jeong, M. Jo, H. Kim, J.H. Kim, T.J. Kim, K.S. Lee, D.H. Moon, S.K. Pa k,
H.B. Rhee, E. Seo, S. Shin, K.S. Sim
Uni e si y o Seoul, Seoul, Ko ea
M. Choi, S. Kang, H. Kim, C. Pa k, I.C. Pa k, S. Pa k, G. Ryu
Sungkyunkwan Uni e si y, Suwon, Ko ea
Y. Choi, Y.K. Choi, J. Goh, M.S. Kim, E. Kwon, J. Lee, S. Lee, H. Seo, I. Yu
Vilnius Uni e si y, Vilnius, Li huania
M.J. Bilinskas, I. G igelionis, M. Janulis, D. Ma isiu e, P. Pe o , T. Sabonis
Cen o de In es igacion y de Es udios A anzados del IPN, Mexico Ci y, Mexico
H. Cas illa-Valdez, E. De La C uz-Bu elo, R. Lopez-Fe nandez, R. Maga˜
na Villalba, A. S´
anchez-
He n´
andez, L.M. Villaseno -Cendejas
Uni e sidad Ibe oame icana, Mexico Ci y, Mexico
S. Ca illo Mo eno, F. Vazquez Valencia
Beneme i a Uni e sidad Au onoma de Puebla, Puebla, Mexico
H.A. Salaza Iba guen
Uni e sidad Au ´onoma de San Luis Po os´ı, San Luis Po os´ı, Mexico
E. Casimi o Lina es, A. Mo elos Pineda, M.A. Reyes-San os
Uni e si y o Auckland, Auckland, New Zealand
D. K o check, J. Tam
Uni e si y o Can e bu y, Ch is chu ch, New Zealand
P.H. Bu le , R. Doesbu g, H. Sil e wood
19
Na ional Cen e o Physics, Quaid-I-Azam Uni e si y, Islamabad, Pakis an
M. Ahmad, I. Ahmed, M.I. Asgha , H.R. Hoo ani, W.A. Khan, T. Khu shid, S. Qazi
Ins i u e o Expe imen al Physics, Facul y o Physics, Uni e si y o Wa saw, Wa saw, Poland
G. B ona, M. Cwiok, W. Dominik, K. Do oba, A. Kalinowski, M. Konecki, J. K olikowski
Sol an Ins i u e o Nuclea S udies, Wa saw, Poland
T. F ueboes, R. Gokieli, M. G´
o ski, M. Kazana, K. Naw ocki, K. Romanowska-Rybinska,
M. Szlepe , G. W ochna, P. Zalewski
Labo a ´o io de Ins umen a¸c˜ao e F´ısica Expe imen al de Pa ´ıculas, Lisboa, Po ugal
N. Almeida, P. Ba gassa, A. Da id, P. Faccioli, P.G. Fe ei a Pa acho, M. Gallina o, P. Musella,
A. Nayak, P.Q. Ribei o, J. Seixas, J. Va ela
Join Ins i u e o Nuclea Resea ch, Dubna, Russia
S. A anasie , I. Belo elo , P. Bunin, I. Golu in, A. Kamene , V. Ka ja in, G. Kozlo , A. Lane ,
P. Moisenz, V. Palichik, V. Pe elygin, S. Shma o , V. Smi no , A. Volodko, A. Za ubin
Pe e sbu g Nuclea Physics Ins i u e, Ga china (S Pe e sbu g), Russia
V. Golo so , Y. I ano , V. Kim, P. Le chenko, V. Mu zin, V. O eshkin, I. Smi no , V. Sulimo ,
L. U a o , S. Va ilo , A. Vo obye , A. Vo obye
Ins i u e o Nuclea Resea ch, Moscow, Russia
Yu. And ee , A. De mene , S. Gninenko, N. Golube , M. Ki sano , N. K asniko , V. Ma ee ,
A. Pashenko , A. To opin, S. T oi sky
Ins i u e o Theo e ical and Expe imen al Physics, Moscow, Russia
V. Epsh eyn, V. Ga ilo , V. Ka ano †, M. Kosso 1, A. K okho in, N. Lychko skaya, V. Popo ,
G. Sa ono , S. Semeno , V. S olin, E. Vlaso , A. Zhokin
Moscow S a e Uni e si y, Moscow, Russia
E. Boos, M. Dubinin23, L. Dudko, A. E sho , A. G ibushin, O. Kodolo a, I. Lokh in, A. Ma kina,
S. Ob az so , M. Pe ilo , S. Pe ushanko, L. Sa yche a, V. Sa in, A. Snigi e
P.N. Lebede Physical Ins i u e, Moscow, Russia
V. And ee , M. Aza kin, I. D emin, M. Ki akosyan, A. Leonido , S.V. Rusako , A. Vinog ado
S a e Resea ch Cen e o Russian Fede a ion, Ins i u e o High Ene gy Physics, P o ino,
Russia
I. Azhgi ey, S. Bi iouko , V. G ishin1, V. Kachano , D. Kons an ino , A. Ko able , V. K ychkine,
V. Pe o , R. Ryu in, S. Slabospi sky, A. Sobol, L. Tou chano i ch, S. T oshin, N. Tyu in,
A. Uzunian, A. Volko
Uni e si y o Belg ade, Facul y o Physics and Vinca Ins i u e o Nuclea Sciences, Belg ade,
Se bia
P. Adzic24, M. Djo dje ic, D. K pic24, J. Milose ic
Cen o de In es igaciones Ene g´e icas Medioambien ales y Tecnol´ogicas (CIEMAT),
Mad id, Spain
M. Aguila -Beni ez, J. Alca az Maes e, P. A ce, C. Ba ilana, E. Cal o, M. Cepeda, M. Ce ada,
M. Chamizo Lla as, N. Colino, B. De La C uz, A. Delgado Pe is, C. Diez Pa dos, D. Dom´
ınguez
V´
azquez, C. Fe nandez Bedoya, J.P. Fe n´
andez Ramos, A. Fe ando, J. Flix, M.C. Fouz,
P. Ga cia-Abia, O. Gonzalez Lopez, S. Goy Lopez, J.M. He nandez, M.I. Josa, G. Me ino,
J. Pue a Pelayo, I. Redondo, L. Rome o, J. San aolalla, M.S. Soa es, C. Willmo

20 A The CMS Collabo a ion
Uni e sidad Au ´onoma de Mad id, Mad id, Spain
C. Albaja , G. Codispo i, J.F. de T oc´
oniz
Uni e sidad de O iedo, O iedo, Spain
J. Cue as, J. Fe nandez Menendez, S. Folgue as, I. Gonzalez Caballe o, L. Llo e Iglesias,
J.M. Vizan Ga cia
Ins i u o de F´ısica de Can ab ia (IFCA), CSIC-Uni e sidad de Can ab ia, San ande , Spain
J.A. B oche o Ci uen es, I.J. Cab illo, A. Calde on, S.H. Chuang, J. Dua e Campde os,
M. Felcini25, M. Fe nandez, G. Gomez, J. Gonzalez Sanchez, C. Jo da, P. Lobelle Pa do, A. Lopez
Vi o, J. Ma co, R. Ma co, C. Ma inez Ri e o, F. Ma o as, F.J. Munoz Sanchez, J. Pied a
Gomez26, T. Rod igo, A.Y. Rod ´
ıguez-Ma e o, A. Ruiz-Jimeno, L. Scodella o, M. Sob on
Sanudo, I. Vila, R. Vila Co abi a e
CERN, Eu opean O ganiza ion o Nuclea Resea ch, Gene a, Swi ze land
D. Abbaneo, E. Au ay, G. Auzinge , P. Baillon, A.H. Ball, D. Ba ney, A.J. Bell27, D. Benede i,
C. Be ne 3, W. Bialas, P. Bloch, A. Bocci, S. Bolognesi, M. Bona, H. B euke , K. Bunkowski,
T. Campo esi, G. Ce mina a, J.A. Coa asa Pe ez, B. Cu ´
e, D. D’En e ia, A. De Roeck, S. Di
Guida, A. Ellio -Peise , B. F isch, W. Funk, A. Gaddi, S. Gennai, G. Geo giou, H. Ge wig,
D. Gigi, K. Gill, D. Gio dano, F. Glege, R. Gomez-Reino Ga ido, M. Gouze i ch, P. Go oni,
S. Gowdy, L. Guiducci, M. Hansen, C. Ha l, J. Ha ey, J. Hegeman, B. Hegne , H.F. Ho mann,
A. Honma, V. Innocen e, P. Jano , K. Kaadze, E. Ka a akis, P. Lecoq, C. Lou enc¸o, T. M¨
aki,
M. Malbe i, L. Malge i, M. Mannelli, L. Mase i, A. Mau isse , F. Meije s, S. Me si, E. Meschi,
R. Mose , M.U. Moze , M. Mulde s, E. Nes old1, M. Nguyen, T. O imo o, L. O sini, E. Pe ez,
A. Pe illi, A. P ei e , M. Pie ini, M. Pimi¨
a, G. Polese, A. Racz, J. Rod igues An unes,
G. Rolandi28, T. Romme ski chen, C. Ro elli, M. Ro e e, H. Sakulin, C. Sch¨
a e , C. Schwick,
I. Segoni, A. Sha ma, P. Sieg is , M. Simon, P. Sphicas29, M. Spi opulu23, M. S oye, P. T opea,
A. Tsi ou, P. Vichoudis, M. Vou ilainen, W.D. Zeune
Paul Sche e Ins i u , Villigen, Swi ze land
W. Be l, K. Dei e s, W. E dmann, K. Gaba hule , R. Ho isbe ge , Q. Ing am, H.C. Kaes li,
S. K¨
onig, D. Ko linski, U. Langenegge , F. Meie , D. Renke , T. Rohe, J. Sibille30,
A. S a odumo 31
Ins i u e o Pa icle Physics, ETH Zu ich, Zu ich, Swi ze land
P. Bo ignon, L. Caminada32, N. Chanon, Z. Chen, S. Ci olin, G. Disse o i, M. Di ma ,
J. Eugs e , K. F euden eich, C. G ab, A. He ´
e, W. Hin z, P. Lecom e, W. Lus e mann,
C. Ma chica32, P. Ma inez Ruiz del A bol, P. Me idiani, P. Mileno ic33, F. Moo ga , C. N¨
ageli32,
P. Ne , F. Nessi-Tedaldi, L. Pape, F. Pauss, T. Punz, A. Rizzi, F.J. Ronga, M. Rossini, L. Sala,
A.K. Sanchez, M.-C. Sawley, B. S iege , L. Tausche †, A. Thea, K. Theo ila os, D. T eille,
C. U schele , R. Wallny, M. Webe , L. Weh li, J. Weng
Uni e si ¨a Z¨u ich, Zu ich, Swi ze land
E. Aguil´
o, C. Amsle , V. Chiochia, S. De Vissche , C. Fa a o, M. I o a Riko a, B. Millan Mejias,
P. O iougo a, C. Regen us, P. Robmann, A. Schmid , H. Snoek
Na ional Cen al Uni e si y, Chung-Li, Taiwan
Y.H. Chang, K.H. Chen, C.M. Kuo, S.W. Li, W. Lin, Z.K. Liu, Y.J. Lu, D. Mek e o ic, R. Volpe,
J.H. Wu, S.S. Yu
Na ional Taiwan Uni e si y (NTU), Taipei, Taiwan
P. Ba alini, P. Chang, Y.H. Chang, Y.W. Chang, Y. Chao, K.F. Chen, W.-S. Hou, Y. Hsiung,
K.Y. Kao, Y.J. Lei, R.-S. Lu, J.G. Shiu, Y.M. Tzeng, M. Wang
21
Cuku o a Uni e si y, Adana, Tu key
A. Adiguzel, M.N. Baki ci34, S. Ce ci35, C. Dozen, I. Dumanoglu, E. Esku , S. Gi gis,
G. Gokbulu , Y. Gule , E. Gu pina , I. Hos, E.E. Kangal, T. Ka aman, A. Kayis Topaksu,
A. Na , G. Onengu , K. Ozdemi , S. Oz u k, A. Pola oz, K. Sogu 36, D. Suna Ce ci35, B. Tali,
H. Topakli34, D. Uzun, L.N. Ve gili, M. Ve gili, C. Zo bilmez
Middle Eas Technical Uni e si y, Physics Depa men , Anka a, Tu key
I.V. Akin, T. Alie , S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Gule , K. Ocalan, A. Ozpineci,
M. Se in, R. Se e , U.E. Su a , E. Yildi im, M. Zey ek
Bogazici Uni e si y, Is anbul, Tu key
M. Deliome oglu, D. Demi 37, E. G¨
ulmez, B. Isildak, M. Kaya38, O. Kaya38, S. Ozko ucuklu39,
N. Sonmez40
Na ional Scien i ic Cen e , Kha ko Ins i u e o Physics and Technology, Kha ko , Uk aine
L. Le chuk
Uni e si y o B is ol, B is ol, Uni ed Kingdom
F. Bos ock, J.J. B ooke, T.L. Cheng, E. Clemen , D. Cussans, R. F azie , J. Golds ein,
M. G imes, M. Hansen, D. Ha ley, G.P. Hea h, H.F. Hea h, J. Jackson, L. K eczko, S. Me son,
D.M. Newbold41, K. Ni unpong, A. Poll, S. Senkin, V.J. Smi h, S. Wa d
Ru he o d Apple on Labo a o y, Didco , Uni ed Kingdom
L. Basso42, K.W. Bell, A. Belyae 42, C. B ew, R.M. B own, B. Camanzi, D.J.A. Cocke ill,
J.A. Coughlan, K. Ha de , S. Ha pe , B.W. Kennedy, E. Olaiya, D. Pe y , B.C. Radbu n-Smi h,
C.H. Shephe d-Themis ocleous, I.R. Tomalin, W.J. Wome sley, S.D. Wo m
Impe ial College, London, Uni ed Kingdom
R. Bainb idge, G. Ball, J. Ballin, R. Beuselinck, O. Buchmulle , D. Colling, N. C ipps, M. Cu aja ,
G. Da ies, M. Della Neg a, W. Fe guson, J. Fulche , D. Fu yan, A. Gilbe , A. Gune a ne B ye ,
G. Hall, Z. Ha he ell, J. Hays, G. Iles, M. Ja is, G. Ka apos oli, L. Lyons, B.C. MacE oy, A.-
M. Magnan, J. Ma ouche, B. Ma hias, R. Nandi, J. Nash, A. Niki enko31, A. Papageo giou,
M. Pesa esi, K. Pe idis, M. Pioppi43, D.M. Raymond, S. Roge son, N. Rompo is, A. Rose,
M.J. Ryan, C. Seez, P. Sha p, A. Spa ow, A. Tappe , S. Tou neu , M. Vazquez Acos a, T. Vi dee,
S. Wake ield, N. Wa dle, D. Wa d ope, T. Whyn ie
B unel Uni e si y, Uxb idge, Uni ed Kingdom
M. Ba e , M. Chadwick, J.E. Cole, P.R. Hobson, A. Khan, P. Kybe d, D. Leslie, W. Ma in,
I.D. Reid, L. Teodo escu
Baylo Uni e si y, Waco, USA
K. Ha akeyama
Bos on Uni e si y, Bos on, USA
T. Bose, E. Ca e a Ja in, C. Fan asia, A. Heis e , J. S . John, P. Lawson, D. Lazic, J. Rohl ,
D. Spe ka, L. Sulak
B own Uni e si y, P o idence, USA
A. A e isyan, S. Bha acha ya, J.P. Chou, D. Cu s, A. Fe apon o , U. Hein z, S. Jabeen,
G. Kuka se , G. Landsbe g, M. Na ain, D. Nguyen, M. Segala, T. Sin hup asi h, T. Spee ,
K.V. Tsang
Uni e si y o Cali o nia, Da is, Da is, USA
R. B eedon, M. Calde on De La Ba ca Sanchez, S. Chauhan, M. Che ok, J. Conway, P.T. Cox,
J. Dolen, R. E bache , E. F iis, W. Ko, A. Kopecky, R. Lande , H. Liu, S. Ma uyama, T. Miceli,
22 A The CMS Collabo a ion
M. Nikolic, D. Pelle , J. Robles, S. Salu , T. Schwa z, M. Sea le, J. Smi h, M. Squi es, M. T ipa hi,
R. Vasquez Sie a, C. Veelken
Uni e si y o Cali o nia, Los Angeles, Los Angeles, USA
V. And ee , K. A isaka, D. Cline, R. Cousins, A. Deishe , J. Du is, S. E han, C. Fa ell, J. Hause ,
M. Igna enko, C. Ja is, C. Plage , G. Rakness, P. Schlein†, J. Tucke , V. Value
Uni e si y o Cali o nia, Ri e side, Ri e side, USA
J. Babb, A. Chand a, R. Cla e, J. Ellison, J.W. Ga y, F. Gio dano, G. Hanson, G.Y. Jeng,
S.C. Kao, F. Liu, H. Liu, O.R. Long, A. Lu h a, H. Nguyen, B.C. Shen†, R. S inge , J. S u dy,
S. Sumowidagdo, R. Wilken, S. Wimpenny
Uni e si y o Cali o nia, San Diego, La Jolla, USA
W. And ews, J.G. B anson, G.B. Ce a i, E. Dusinbe e, D. E ans, F. Gol , A. Holzne , R. Kelley,
M. Lebou geois, J. Le s, B. Mangano, S. Padhi, C. Palme , G. Pe ucciani, H. Pi, M. Pie i,
R. Ranie i, M. Sani, V. Sha ma, S. Simon, Y. Tu, A. Va ak, S. Wasse baech44, F. W¨
u hwein,
A. Yagil, J. Yoo
Uni e si y o Cali o nia, San a Ba ba a, San a Ba ba a, USA
D. Ba ge, R. Bellan, C. Campagna i, M. D’Al onso, T. Danielson, K. Flowe s, P. Ge e ,
J. Incandela, C. Jus us, P. Kala ase, S.A. Koay, D. Ko alskyi, V. K u elyo , S. Lowe e, N. Mccoll,
V. Pa lunin, F. Rebassoo, J. Ribnik, J. Richman, R. Rossin, D. S ua , W. To, J.R. Vliman
Cali o nia Ins i u e o Technology, Pasadena, USA
A. Ap esyan, A. Bo nheim, J. Bunn, Y. Chen, M. Ga aullin, Y. Ma, A. Mo , H.B. Newman,
C. Rogan, K. Shin, V. Timciuc, P. T aczyk, J. Ve e ka, R. Wilkinson, Y. Yang, R.Y. Zhu
Ca negie Mellon Uni e si y, Pi sbu gh, USA
B. Akgun, R. Ca oll, T. Fe guson, Y. Iiyama, D.W. Jang, S.Y. Jun, Y.F. Liu, M. Paulini, J. Russ,
H. Vogel, I. Vo obie
Uni e si y o Colo ado a Boulde , Boulde , USA
J.P. Cumala , M.E. Dina do, B.R. D ell, C.J. Edelmaie , W.T. Fo d, A. Gaz, B. Heybu n, E. Luiggi
Lopez, U. Nauenbe g, J.G. Smi h, K. S enson, K.A. Ulme , S.R. Wagne , S.L. Zang
Co nell Uni e si y, I haca, USA
L. Agos ino, J. Alexande , D. Cassel, A. Cha e jee, S. Das, N. Egge , L.K. Gibbons, B. Hel sley,
W. Hopkins, A. Khukhunaish ili, B. K eis, G. Nicolas Kau man, J.R. Pa e son, D. Puigh,
A. Ryd, E. Sal a i, X. Shi, W. Sun, W.D. Teo, J. Thom, J. Thompson, J. Vaughan, Y. Weng,
L. Wins om, P. Wi ich
Fai ield Uni e si y, Fai ield, USA
A. Biselli, G. Ci ino, D. Winn
Fe mi Na ional Accele a o Labo a o y, Ba a ia, USA
S. Abdullin, M. Alb ow, J. Ande son, G. Apollina i, M. A ac, J.A. Bakken, S. Bane jee,
L.A.T. Baue dick, A. Be e as, J. Be yhill, P.C. Bha , I. Bloch, F. Bo che ding, K. Bu ke ,
J.N. Bu le , V. Che lu u, H.W.K. Cheung, F. Chlebana, S. Cihangi , W. Coope , D.P. Ea ly,
V.D. El i a, S. Esen, I. Fisk, J. F eeman, Y. Gao, E. Go schalk, D. G een, K. Gun ho i,
O. Gu sche, J. Hanlon, R.M. Ha is, J. Hi schaue , B. Hoobe man, H. Jensen, M. Johnson,
U. Joshi, R. Kha iwada, B. Klima, K. Kousou is, S. Kuno i, S. Kwan, C. Leonidopoulos,
P. Limon, D. Lincoln, R. Lip on, J. Lykken, K. Maeshima, J.M. Ma a ino, D. Mason, P. McB ide,
T. Miao, K. Mish a, S. M enna, Y. Musienko45, C. Newman-Holmes, V. O’Dell, R. Po des,
O. P oko ye , N. Saoulidou, E. Sex on-Kennedy, S. Sha ma, W.J. Spalding, L. Spiegel, P. Tan,
23
L. Taylo , S. Tkaczyk, L. Uplegge , E.W. Vaande ing, R. Vidal, J. Whi mo e, W. Wu, F. Yang,
F. Yumice a, J.C. Yun
Uni e si y o Flo ida, Gaines ille, USA
D. Acos a, P. A e y, D. Bou ilko , M. Chen, M. De G u ola, G.P. Di Gio anni, D. Dobu ,
A. D ozde skiy, R.D. Field, M. Fishe , Y. Fu, I.K. Fu ic, J. Ga ne , B. Kim, J. Konigsbe g,
A. Ko y o , A. K opi ni skaya, T. Kyp eos, K. Ma che , G. Mi selmakhe , L. Muniz, C. P esco ,
R. Reming on, M. Schmi , B. Scu lock, P. Selle s, N. Skhi ladze, M. Snowball, D. Wang,
J. Yel on, M. Zaka ia
Flo ida In e na ional Uni e si y, Miami, USA
C. Ce on, V. Gaul ney, L. K ame , L.M. Lebolo, S. Linn, P. Ma kowi z, G. Ma inez, D. Mesa,
J.L. Rod iguez
Flo ida S a e Uni e si y, Tallahassee, USA
T. Adams, A. Askew, D. Bandu in, J. Bochenek, J. Chen, B. Diamond, S.V. Gleyze , J. Haas,
S. Hagopian, V. Hagopian, M. Jenkins, K.F. Johnson, H. P ospe , L. Que enmon , S. Sekmen,
V. Vee a agha an
Flo ida Ins i u e o Technology, Melbou ne, USA
M.M. Baa mand, B. Do ney, S. Gu again, M. Hohlmann, H. Kalakhe y, R. Ralich,
I. Vodopiyano
Uni e si y o Illinois a Chicago (UIC), Chicago, USA
M.R. Adams, I.M. Anghel, L. Apanase ich, Y. Bai, V.E. Baz e a, R.R. Be s, J. Callne ,
R. Ca anaugh, C. D agoiu, L. Gau hie , C.E. Ge be , D.J. Ho man, S. Khala yan, G.J. Kunde46,
F. Lac oix, M. Malek, C. O’B ien, C. Sil es e, A. Smo on, D. S om, N. Va elas
The Uni e si y o Iowa, Iowa Ci y, USA
U. Akgun, E.A. Albay ak, B. Bilki, W. Cla ida, F. Du u, C.K. Lae, E. McClimen , J.-P. Me lo,
H. Me me kaya47, A. Mes i ish ili, A. Moelle , J. Nach man, C.R. Newsom, E. No beck,
J. Olson, Y. Onel, F. Ozok, S. Sen, J. We zel, T. Ye kin, K. Yi
Johns Hopkins Uni e si y, Bal imo e, USA
B.A. Ba ne , B. Blumen eld, A. Bona o, C. Eskew, D. Fehling, G. Giu giu, A.V. G i san, Z.J. Guo,
G. Hu, P. Maksimo ic, S. Rappoccio, M. Swa z, N.V. T an, A. Whi beck
The Uni e si y o Kansas, Law ence, USA
P. Ba inge , A. Bean, G. Benelli, O. G acho , R.P. Kenny Iii, M. Mu ay, D. Noonan, S. Sande s,
J.S. Wood, V. Zhuko a
Kansas S a e Uni e si y, Manha an, USA
A. . Ba uss, T. Bol on, I. Chakabe ia, A. I ano , S. Khalil, M. Makouski, Y. Ma a in, S. Sh es ha,
I. S in adze, Z. Wan
Law ence Li e mo e Na ional Labo a o y, Li e mo e, USA
J. G onbe g, D. Lange, D. W igh
Uni e si y o Ma yland, College Pa k, USA
A. Baden, M. Bou emeu , S.C. Eno, D. Fe encek, J.A. Gomez, N.J. Hadley, R.G. Kellogg, M. Ki n,
Y. Lu, A.C. Migne ey, K. Rossa o, P. Rume io, F. San anas asio, A. Skuja, J. Temple, M.B. Tonjes,
S.C. Tonwa , E. Twed
Massachuse s Ins i u e o Technology, Camb idge, USA
B. Al e , G. Baue , J. Benda id, W. Busza, E. Bu z, I.A. Cali, M. Chan, V. Du a, P. E e ae s,