EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP/1020-048
2010/11/29
CMS-QCD-10-004
Cha ged pa icle mul iplici ies in pp in e ac ions a
√s=0.9, 2.36, and 7 TeV
The CMS Collabo a ion∗
Abs ac
Measu emen s o p ima y cha ged had on mul iplici y dis ibu ions a e p esen ed o
non-single-di ac i e e en s in p o on-p o on collisions a cen e-o -mass ene gies o
√s=0.9, 2.36, and 7 TeV, in i e pseudo apidi y anges om |η|<0.5 o |η|<2.4.
The da a we e collec ed wi h he minimum-bias igge o he CMS expe imen du -
ing he LHC commissioning uns in 2009 and he 7 TeV un in 2010. The mul iplici y
dis ibu ion a √s=0.9 TeV is in ag eemen wi h p e ious measu emen s. A highe
ene gies he inc ease o he mean mul iplici y wi h √sis unde es ima ed by mos
e en gene a o s. The a e age ans e se momen um as a unc ion o he mul iplic-
i y is also p esen ed. The measu emen o highe -o de momen s o he mul iplici y
dis ibu ion con i ms he iola ion o Koba-Nielsen-Olesen scaling ha has been ob-
se ed a lowe ene gies.
Submi ed o he Jou nal o High Ene gy Physics (JHEP)
∗See Appendix A o he lis o collabo a ion membe s
a Xi :1011.5531 1 [hep-ex] 24 No 2010
1
1 In oduc ion
The cha ged had on mul iplici y, o numbe o p ima y cha ged had ons, n, is a basic global
obse able cha ac e ising inal s a es in high-ene gy-collision p ocesses. The mul iplici y dis-
ibu ion, Pn, is he p obabili y o p oduce ncha ged had ons in an e en , ei he in ull phase
space o in es ic ed phase space domains. In his pape we epo measu emen s o Pnin non-
single-di ac i e [1] p o on-p o on collisions, a cen e-o -mass ene gies √s=0.9, 2.36, and
7 TeV a he La ge Had on Collide (LHC) [2]. The measu emen s a e based on e en s eco ded
by he Compac Muon Solenoid (CMS) [3] expe imen , using a minimum-bias igge .
Ene gy-momen um and cha ge conse a ion signi ican ly in luence he mul iplici y dis ibu-
ion o he ull phase space. The dis ibu ion in es ic ed phase space, which is less a ec ed by
such cons ain s, is expec ed o be a mo e sensi i e p obe o he unde lying dynamics and can
be used o be e cons ain phenomenological models. Comp ehensi e e iews on he subjec
can be ound in [1, 4, 5]. The measu emen s desc ibed in his pape a e pe o med o in e -
als o inc easing ex en in pseudo apidi y om |η|<0.5 up o |η|<2.4, whe e ηis de ined as
−ln[ an(θ/2)], and θis he pola angle o he pa icle wi h espec o he coun e clockwise beam
di ec ion. In hese measu emen s p ima y cha ged had ons a e de ined as all cha ged had ons
p oduced in he in e ac ion, including he p oduc s o s ong and elec omagne ic decays, bu
excluding p oduc s o weak decays and had ons o igina ing om seconda y in e ac ions.
Independen emission o single pa icles yields a Poissonian Pn. De ia ions om his shape,
he e o e, e eal co ela ions. These co ela ions a e p edominan ly sho ange in apidi y,
a ibu ed o clus e decays, and e lec local conse a ion o quan um numbe s in he had oni-
sa ion p ocess. In had on-had on in e ac ions, addi ional la ge long- ange apidi y co ela ions
a e obse ed, whose magni ude inc eases wi h √s[6]. In con as , in e+e−annihila ions such
long- ange co ela ions a e much weake and p ac ically absen in wo- and h ee-je e en
samples [7].
The mean o he mul iplici y dis ibu ion, hni, is equal o he in eg al o he inclusi e single-
pa icle densi y in he conside ed phase-space domain. Highe -o de momen s o Pnmeasu e
e en - o-e en mul iplici y luc ua ions. They a e ela ed o he wo-pa icle and highe -o de
inclusi e densi y co ela ions and p o ide mo e de ailed dynamical in o ma ion han ha con-
ained in single-pa icle inclusi e spec a [8–12]. The a e age ans e se momen um o he
cha ged pa icles, hpTi, exhibi s a posi i e co ela ion wi h he e en mul iplici y in had on-
had on collisions ([13–19] and e e ences he ein).
T adi ionally, he sdependence o Pnand i s momen s has been much discussed [1, 4, 5] in
ela ion o Koba-Nielsen-Olesen (KNO) scaling [20, 21]. In his amewo k, one s udies he
KNO unc ion Ψ(z) = hniPn, whe e z=n/hni. I KNO scaling holds, Ψ(z)and he no malised
momen s Cq=hnqi/hniqa e independen o s.
Th oughou his pape , we compa e he da a wi h exis ing measu emen s a simila o lowe
cen e-o -mass ene gies and wi h p edic ions o he mul iplici y dis ibu ion and i s mean alue
om analy ical and e en gene a o Mon e Ca lo (MC) models. The models a e based on he as-
sump ion ha had ons a e p oduced ia he agmen a ion o colou s ings. This compa ison
should allow o a be e uning o he exis ing MC models o accu a ely simula e minimum-
bias e en s and unde lying-e en e ec s.
The nex sec ion gi es a sho desc ip ion o he CMS de ec o . Sec ion 3 desc ibes he MC
models used in he analysis, while Sec ion 4 p esen s he da a samples. The ack econs uc ion
and accep ance a e explained in Sec ion 5. Sec ion 6 desc ibes he co ec ions applied o he
da a. Sec ion 7 lis s all ele an sys ema ic unce ain ies. The esul s a e discussed in Sec ion 8.
23 Models
2 The CMS de ec o
A comple e desc ip ion o he CMS de ec o can be ound in [3]. The CMS expe imen uses
a igh -handed coo dina e sys em, wi h he o igin a he nominal in e ac ion poin (IP), he x
axis poin ing o he cen e o he LHC ing, he yaxis poin ing up, and he zaxis along he
coun e clockwise beam di ec ion.
The cen al ea u e o he CMS de ec o is a supe conduc ing solenoid o 6 m in e nal diame e ,
p o iding an axial magne ic ield wi h nominal s eng h o 3.8 T. Imme sed in he magne ic
ield a e he pixel acke , he silicon-s ip acke (SST), he lead ungs a e elec omagne ic cal-
o ime e , he b ass/scin illa o had on calo ime e and he muon de ec ion sys em. In addi ion
o he ba el and endcap calo ime e s, he s eel/qua z- ib e o wa d calo ime e (HF) co e s
he egion 2.9 <|η|<5.2.
Two o he CMS subde ec o s ac ing as LHC beam moni o s, he Beam Scin illa ion Coun e s
(BSC) and he Beam Pick-up Timing o he eXpe imen s (BPTX) de ices, we e used o ig-
ge he de ec o eadou . The BSCs a e loca ed along he beam line on each side o he IP a a
dis ance o 10.86 m and a e sensi i e in he ange 3.23 <|η|<4.65. The wo BPTX de ices,
which a e loca ed inside he beam pipe a dis ances o 175 m om he IP, a e designed o p o-
ide p ecise in o ma ion on he bunch s uc u e and iming o he incoming beams, wi h a ime
esolu ion be e han 0.2 ns.
The acking de ec o consis s o 1440 silicon-pixel and 15148 silicon-s ip de ec o modules.
The ba el pa consis s o 3 (10) laye s o pixel (SST) modules a ound he IP a dis ances ang-
ing om 4.4 cm o 1.1 m. Fi e ou o he 10 s ip laye s a e double sided and p o ide addi ional
zcoo dina e measu emen s. The wo endcaps consis o 2 (12) disks o pixel (SST) modules ha
ex end he pseudo apidi y accep ance o |η|<2.5. The acke p o ides an impac pa ame e
esolu ion o abou 100 µm and a pT esolu ion o abou 0.7% o 1 GeV/ccha ged pa icles a
no mal incidence [22, 23].
3 Models
The PYTHIA 6 [24] gene a o and i s agmen a ion model uned o CDF da a [25, 26], he ea e
called PYTHIA D6T, is used as a baseline model o simula e inelas ic pp collisions. Howe e ,
a 7 TeV a dedica ed PYTHIA une [27] desc ibing be e he high mul iplici ies is used o co -
ec ing he da a. Al e na i e unings ha di e mainly in he modelling o mul iple pa on
in e ac ions ha e also been conside ed [26, 28, 29]. PHOJET [30, 31] is used as an al e na i e
e en gene a o ha di e s mainly in he unde lying dynamical model o pa icle p oduc ion.
While PYTHIA con ains a leas one ha d sca e pe e en , pa icle p oduc ion in PHOJET, which
is based on he dual-pa on model [32], is p edominan ly so and con ains in gene al mul iple-
s ing con igu a ions de i ed om he dual-pa on model wi h mul i-Pome on exchanges [32].
Each Pome on exchange gi es ise o wo s ings s e ched be ween ei he alence o sea pa -
ons. A low ene gies he dominan p ocess is single-Pome on exchange, which leads o wo
s ings s e ched be ween alence qua ks and diqua ks. Wi h inc easing ene gy, addi ional
Pome on exchanges occu , o ming s ings s e ched be ween sea pa ons. Because he sea pa -
ons ca y on a e age only a small ac ion o he momen um o he inciden had ons, hese
s ings a e concen a ed in he cen al apidi y egion. These ex a s ings [33, 34] a e needed o
explain he KNO scaling iola ions obse ed a high ene gies [35, 36], he inc ease o he cen-
al pa icle densi y wi h inc easing ene gy [35–37], he hpTi e sus ndependence [38, 39], and
long- ange apidi y co ela ions [40]. The dis ibu ion o he numbe o exchanged Pome ons
can be ob ained om pe u ba i e Reggeon calculus and uni a i y, by means o i s o he mea-
3
su ed o al, elas ic, and di ac i e c oss sec ions as desc ibed in [41–43]. O he al e na i es
based on he Colou Glass Condensa e (CGC) pic u e wi h sa u a ed gluons [44] also make
p edic ions o he mul iplici y dependence o hpTiand o he long- ange apidi y co ela-
ions.
We also compa e ou measu emen s wi h a new agmen a ion model implemen ed in PYTHIA
8 [45]. In addi ion o ha ing pT-o de ed pa on showe s, a he han an o de ing by i uali y, i
di e s om i s p edecesso in he modelling o mul iple-pa on in e ac ions and he ea men
o beam emnan s and di ac ion. The de ailed MC simula ion o he CMS de ec o esponse is
based on GEANT4 [46]. Simula ed e en s we e p ocessed and econs uc ed in he same manne
as collision da a.
4 Da a sample
Nea he end o 2009, he CMS expe imen collec ed wo da ase s o p o on-p o on collisions a
cen e-o -mass ene gies o 0.9 and 2.36 TeV. In Ma ch 2010 a new unning pe iod a √s=7 TeV
s a ed, o which da a collec ed in he i s days ha e been analysed o his pape . The co e-
sponding inelas ic p o on-p o on in e ac ion a es we e abou 11, 3, and 50 Hz, espec i ely, o
hese da ase s. A hese a es, he ac ion o bunch c ossings in which wo o mo e minimum-
bias collisions occu ed is negligible [47, 48].
Di ac ion is commonly cha ac e ised by one (single-di ac ion) o wo (double-di ac ion)
colou less exchanges esul ing in he obse a ion o a la ge apidi y in e al de oid o any
had on ac i i y ( apidi y gap). All esul s p esen ed in his pape e e o inelas ic non-single-
di ac i e (NSD) in e ac ions and a e based on an e en selec ion ha e ains a la ge ac-
ion o he non-di ac i e (ND) and double-di ac i e (DD) e en s, while dis a ou ing single-
di ac i e (SD) e en s.
The igge and o line e en selec ion a e nea ly iden ical o hose used in [47, 48]; abou h ee
imes mo e e en s we e used in his analysis a √s=0.9 and 7 TeV. The igge equi ed a
signal in any o he BSC scin illa o coun e s, in coincidence wi h ei he o he wo BPTX de ices
indica ing he p esence o a leas one p o on bunch c ossing he IP. Beam halo backg ounds a e
educed by using he iming in o ma ion om he BSC coun e s a opposi e ends o he CMS
de ec o . Addi ional beam-induced backg ounds a e emo ed by equi ing he clus e sizes in
he pixel de ec o o be consis en wi h a single p ima y e ex, as desc ibed in [47]. NSD e en s
a e selec ed by equi ing a leas one HF calo ime e owe wi h mo e han 3 GeV o o al ene gy
in each o he posi i e-zand nega i e-zHF calo ime e s. Finally, a econs uc ed p ima y e ex
is equi ed wi h he zcoo dina e wi hin ±15 cm o he cen e o he beam collision egion.
Fo he inal analysis, o als o abou 132, 12, and 442 housand e en s we e e ained a √s=
0.9, 2.36, and 7 TeV, espec i ely. E en yields a a ious s ages o he selec ion a e shown in
Table 1.
5 T ack econs uc ion and accep ance de ini ion
The ba el and endcap pixel and SST de ec o s a e used in he econs uc ion o acks wi hin
an accep ance o |η|<2.5. Due o a la ge d op in econs uc ion e iciency nea he limi s o
his ange, we es ic he compu a ion o he mul iplici y spec a o he egion |η|<2.4.
In p o on-p o on collisions a he LHC, he e en s selec ed by minimum-bias igge s in ol e
p edominan ly so in e ac ions and con ain mos ly pa icles wi h small ans e se momen a.

45 T ack econs uc ion and accep ance de ini ion
Table 1: E en yields in each da a sample a e sequen ial igge and e en selec ion.
Selec ion √s(TeV)
0.9 2.36 7
beam backg ound ejec ion + L1 igge 254666 18739 610549
all p eceding + o wa d calo ime e s 146658 12019 500077
all p eceding + p ima y e ex 132294 11674 441924
These a e econs uc ed by ex ending he s anda d acking algo i hms o he CMS expe imen ,
which a e based on a combina o ial ack inde [22] ha pe o ms mul iple i e a ions. Hi s ha
can be assigned unambiguously o acks in one i e a ion a e emo ed om he collec ion o
acke hi s o c ea e a smalle collec ion ha can be used in he subsequen i e a ion. This i e -
a i e p ocedu e was u he op imised o p ima y ack econs uc ion wi h pT≥100 MeV/c
in minimum-bias e en s [47]. The econs uc ion e iciency, es ima ed by means o he de-
ec o simula ion, exceeds 90% o acks wi h pT>500 MeV/cand d ops below 70% o
acks wi h pT<100 MeV/c. Con amina ion om mis- econs uc ed acks is below 5% o
pT<500 MeV/c.
A e h ee i e a ions o he combina o ial ack inde , he posi ion o he p ima y e ex is
ecompu ed and hen used as an addi ional cons ain in a e i o all p e iously econs uc ed
acks, hus imp o ing he o e all esolu ion in ηand pT. An agglome a i e clus e ing al-
go i hm ollowed by a Gaussian mix u e model [49] we e applied in o de o op imise he
e ex- inding e iciency.
The con amina ion due o decays o long-li ed pa icles (deno ed as V0decays) is domina ed
by cha ged pions and p o ons o igina ing om K0
Sand Λdecays. The K0
Sp oduc ion a e is
oughly 5% o ha o all cha ged pa icles [50], and he esul ing cha ged seconda ies amoun
o 7% o all π±. The Λp oduc ion is measu ed o be 43% o K0
S[51, 52] in his kinema ic do-
main, yielding ano he 3% o cha ged seconda ies consis ing o p o ons and pions. In o de
o educe he con amina ion o hese V0decay p oduc s and seconda ies p oduced in in e ac-
ions o cha ged pa icles wi h he ma e ial o he de ec o , we equi e all econs uc ed acks
o be associa ed wi h he p ima y e ex. This is done by selec ing acks wi h a small impac
pa ame e wi h espec o he p ima y e ex posi ion bo h in he ans e se plane and along
he zaxis [47]. Only 1.5% o K0
Sand Λdecay p oduc s pass hese selec ions, esul ing in a inal
con amina ion o 0.2%.
The K±/π± a io is known o be ai ly cons an o e a wide ange o cen e-o -mass ene gies
and is be ween 8 and 12% [50]. The K±ha e a lowe econs uc ion e iciency a low pT han
pions and mismodeling o he K±/π± a io could esul in a change in he mul iplici y dis-
ibu ion. Howe e a doubling o he K±/π± a io yields a negligible shi o 0.25% in he
mul iplici y a e age. This is expec ed because he hpTio K±is subs an ially highe han π±,
and K± he e o e con ibu e e y li le in he pT ange whe e he econs uc ion e iciencies di -
e . Finally, only acks wi h a ela i e unce ain y on hei measu ed ans e se momen um
smalle han 10% a e selec ed; his equi emen ejec s mainly low-quali y and badly econ-
s uc ed acks.
5
Table 2: The pe cen age o single-di ac i e e en s (SD/inelas ic) a each cen e-o -mass ene gy
as p edic ed by PYTHIA D6Tand PHOJET.
Gene a o √s(TeV)
0.9 2.36 7
PYTHIA D6T22.5 21.0 19.2
PHOJET 18.9 16.2 13.8
6 Co ec ions
Due o he equi emen o signi ican ac i i y in bo h ends o he HF, he e en selec ion ac-
cep ance o SD e en s is small: 5% a 0.9 TeV and 7% a 7 TeV. This con ibu ion is he e o e
sub ac ed based on simula ed PYTHIA e en s. The PYTHIA and PHOJET p edic ions o he ini-
ial ac ions o SD e en s di e subs an ially, as seen om Table 2. The di e ence o he wo
p edic ions is aken as he sys ema ic unce ain y ela ed o he SD sub ac ion.
I is cus oma y o no malise he cha ged had on mul iplici y dis ibu ion Pn=σn/σ, whe e
σndeno es he c oss sec ion o a ixed mul iplici y n, o ei he he o al inelas ic c oss sec ion
o he NSD c oss sec ion. Fo he esul s p esen ed in his pape he no malisa ion ac o σ
co esponds o he la e .
The minimum-bias igge and NSD selec ion una oidably in oduce a bias in he measu ed
cha ged had on mul iplici y. Fu he mo e, a ac ion o he e en s a e emo ed by he equi e-
men o a good quali y p ima y e ex. These e ec s esul in an accep ed mul iplici y gi en
by
Tn=en·Pn, (1)
whe e enis he igge and e en econs uc ion e iciency o mul iplici y n. This e iciency is
close o 100% o mul iplici ies la ge han n=20 and d ops g adually o 40% o n=1.
Due o ine iciencies in ack econs uc ion and accep ance, he c ea ion o seconda y pa icles
by he in e ac ion o p ima ies wi h he beam pipe and he de ec o ma e ial, and he p esence
o decay p oduc s o long-li ed had ons, one will in gene al no measu e he ue mul iplici y
nbu a s a is ically ela ed quan i y m. The s a is ical dis ibu ion Omo his obse ed mul i-
plici y is ela ed o he ue accep ed mul iplici y dis ibu ion by he linea ela ion
Om=∑
n
Rm,n·Tn. (2)
The p oblem o in e ing he esponse ma ix Rm,n, he e aken om MC, is well known and
ex ensi e li e a u e on he opic exis s [53, 54]. When dealing wi h limi ed e en samples,
an algeb aic in e sion o Rm,n u ns ou o be impossible and leads o uns able esul s. We
he e o e use a Bayesian un olding me hod, as desc ibed in [55]. The un olding p ocedu e in-
oduces la ge s a is ical co ela ions be ween adjacen bins o he mul iplici y spec um. The
ull co a iance ma ix o he un olded mul iplici y spec um was calcula ed using a esampling
echnique [54].
The a e age ans e se momen um hpTias a unc ion o nwas measu ed as well. Fo each bin
in aw mul iplici y, a Mon e Ca lo based co ec ion ac o hpgen
Ti/hp ec
Tiwas applied o con e
he measu ed hpTi o he co esponding alue o p ima y cha ged had ons. Subsequen ly, he
esponse ma ix Rm,n, weigh ed by he co ec ed da a, was applied o co ec he mul iplici ies.
The co ec ness o he un olding p ocedu e was e i ied using MC e en s gene a ed wi h ou
67 Sys ema ic unce ain ies
baseline PYTHIA D6T une whe e we compa ed he mul iplici y dis ibu ion o gene a ed p i-
ma y had ons wi h ha o econs uc ed acks a e un olding. A all ene gies conside ed,
an excellen ag eemen wi h he gene a ed had ons is achie ed, p o ing he s abili y o he
p ocedu e.
The ack econs uc ion e iciency o he minimum-bias acking d ops d as ically o pT<
100 MeV/c, while he mis- econs uc ed ack a e inc eases. Ra he han co ec ing o hese
e ec s using MC simula ions, we econs uc he pTspec um in da a hemsel es and calcula e
he ac ion o cha ged had ons wi h pT<100 MeV/cby ex apola ing he measu ed spec um
in da a, using a pa ame isa ion based on an exponen ial o a hi d-deg ee polynomial in pT.
The ac ion o cha ged had ons added by his co ec ion anges be ween 5% and 7% depend-
ing on he cen e-o -mass ene gy and he pseudo apidi y in e al unde s udy. The unc ional
o m used o ex apola e o he lowes ans e se momen a in oduces an unce ain y o 1%
on his ac ion and is aken in o accoun in he sys ema ic unce ain ies. The e ec o all he
co ec ion p ocedu es on he measu ed aw mul iplici y dis ibu ion is illus a ed in Fig. 1 o
a cen e-o -mass ene gy o 7 TeV.
n
0 20 40 60 80 100 120 140 160
E en s / bin wid h
0
5000
10000
15000
20000
Be o e Co ec ions
A e Co ec ions
| < 2.4η|
CMS NSD 7 TeV
Figu e 1: A compa ison o he unco ec ed and ully co ec ed mul iplici y dis ibu ion a
√s=7 TeV o |η|<2.4 . The unce ain ies be o e co ec ions a e s a is ical only, while a -
e co ec ions he s a is ical and sys ema ic unce ain ies a e added in quad a u e.
7 Sys ema ic unce ain ies
Fou main sou ces o sys ema ic unce ain y con ibu e o he o al unce ain y on he mul i-
plici y dis ibu ion Pnand hpTi e sus n: he unce ain y on he igge and e en selec ion
e iciency, he unce ain y on he acking e iciency and accep ance, he model dependence o
he esponse ma ix, and he model dependen SD sub ac ion. All ou a e discussed below.
The e ec s o misalignmen o he acking de ec o , dead senso s, and he unce ain y on he
e ex posi ion a e much smalle and a e con ained wi hin he o e all acking sys ema ic un-
ce ain y. Fo hpTi e sus n, he e ec o he e en selec ion and SD sub ac ion was obse ed
o be negligible.
7
Table 3: Summa y o sys ema ic unce ain ies on he ack econs uc ion.
Sou ce acking unce ain y (%)
T acking e iciency 2.0
Accep ance 1.0
Pixel hi e iciency 0.3
Pixel clus e spli ing 0.2
Co ec ion o seconda ies 1.0
Misalignmen 0.1
Beam halo 0.1
Mul iple ack coun ing 0.1
Mis- econs uc ed acks 0.5
To al 2.5
T igge and e en selec ion e iciency. The co ec ions o he igge and e en selec ion e i-
ciency a e based en i ely on MC simula ion. The la ges impac on he o e all e iciency is ha
o he HF coincidence equi emen . A c oss-check o he mul iplici y dependen e iciency wi h
ze o-bias e en s, which a e by de ini ion no biased a all ( andom igge on collisions), shows
good ag eemen wi hin s a is ical e o s be ween da a and MC. A ela i e shi o he e iciency
co ec ion ac o s by +5%
−7% o low mul iplici ies, dec easing o ±1% o n∼20, co e s he igge
e iciency measu ed in ze o-bias da a. This leads o a maximum 5% sys ema ic unce ain y.
T acking e iciency and accep ance. A co ec desc ip ion o he acking e iciency in he MC
simula ion o he de ec o is essen ial o ob aining a co ec esponse ma ix. A low ans-
e se momen a, he e iciency d ops due o a loss o hi s on he acks ha a e s opped wi hin
he acking olume. As in [47], we assign a 2% unce ain y on his e iciency. The emaining
con amina ion is mos ly due o seconda y acks o igina ing om in e ac ions wi h he ma e-
ial o he LHC beam pipe a ound he in e ac ion poin . This is es ima ed in [47] o be no mo e
han 1%, and is con i med based on [56]. These unce ain ies, oge he wi h smalle con ibu-
ions om misalignmen o he acking de ec o , beam-halo backg ound, mul iple coun ing o
acks, and mis- econs uc ed acks a e added in quad a u e o p oduce a o al acking unce -
ain y o 2.5%. All co ec ion ac o s ela ed o ack econs uc ion a e summa ised in Table 3.
As was discussed in Sec ion 5, he con amina ion om V0decays a e associa ing acks wi h
he p ima y e ex is small (0.2%) and al eady included in he sys ema ic unce ain y o sec-
onda y acks. The di e ence in econs uc ion e iciency o cha ged kaons and pions also has
a negligible impac on he measu ed mul iplici y dis ibu ion. Finally, he ex apola ion unce -
ain y om pT=100 MeV/c o ze o is 1% (Sec ion 6). Fo hpTi e sus n, his was aken in o
accoun by changing he mean ans e se momen um by he a e age pTo acks los du ing
he e en econs uc ion olded wi h he acking e iciency unce ain y. The o e all e ec o
his sys ema ic unce ain y is less han 10% o small mul iplici ies, bu can each up o 30% o
he high mul iplici ies, whe e i is he main sou ce o sys ema ic unce ain y.
Model dependence. The baseline MC model ha is used o un old he mul iplici y dis ibu ion
unde es ima es he single-pa icle densi ies a ze o apidi y by 10% ela i ely o |η| ∼ 1.5 a
√s=0.9 and 2.36 TeV, bu co ec ly desc ibes he 7 TeV da a shapes. This disc epancy a ec s
he esponse ma ix used in he un olding p ocedu e. The e ec on he mul iplici y dis ibu ion
is es ima ed o be a mos 3% by means o an al e na i e MC une. The obus ness o he
un olding p ocedu e was e i ied by un olding pseudo-da a gene a ed wi h PHOJET using a
esponse ma ix cons uc ed wi h PYTHIA. The induced a ia ion on Pnis below 3% and is
14 9 Conclusions
none is able o desc ibe simul aneously he mul iplici y dis ibu ions and he pTspec um a
√s=7 TeV. In gene al, models p edic oo ew low-momen um pa icles, indica ing ha by
inc easing he amoun o mul iple-pa on in e ac ions one e ec i ely in oduces oo many ha d
sca e s in he e en .
The change o slope in Pnin he wides cen al pseudo apidi y in e als obse ed a √s=
7 TeV, combined wi h he s ong linea inc ease o he Cqmomen s, indica es a clea iola ion
o KNO scaling wi h espec o lowe ene gies. This obse a ion me i s u he s udies.
Acknowledgemen s
We wish o cong a ula e ou colleagues in he CERN accele a o depa men s o he excellen
pe o mance o he LHC machine. We hank he echnical and adminis a i e s a a CERN and
o he CMS ins i u es. This wo k was suppo ed by he Aus ian Fede al Minis y o Science and
Resea ch; he Belgium Fonds de la Reche che Scien i ique, and Fonds oo We enschappelijk
Onde zoek; he B azilian Funding Agencies (CNPq, CAPES, FAPERJ, and FAPESP); he Bul-
ga ian Minis y o Educa ion and Science; CERN; he Chinese Academy o Sciences, Minis y
o Science and Technology, and Na ional Na u al Science Founda ion o China; he Colombian
Funding Agency (COLCIENCIAS); he C oa ian Minis y o Science, Educa ion and Spo ; he
Resea ch P omo ion Founda ion, Cyp us; he Es onian Academy o Sciences and NICPB; he
Academy o Finland, Finnish Minis y o Educa ion, and Helsinki Ins i u e o Physics; he Ins i-
u Na ional de Physique Nucl´
eai e e de Physique des Pa icules / CNRS, and Commissa ia
`
a l’´
Ene gie A omique, F ance; he Bundesminis e ium ¨
u Bildung und Fo schung, Deu sche
Fo schungsgemeinscha , and Helmhol z-Gemeinscha Deu sche Fo schungszen en, Ge ma-
ny; he Gene al Sec e a ia o Resea ch and Technology, G eece; he Na ional Scien i ic Re-
sea ch Founda ion, and Na ional O ice o Resea ch and Technology, Hunga y; he Depa -
men o A omic Ene gy, and Depa men o Science and Technology, India; he Ins i u e o
S udies in Theo e ical Physics and Ma hema ics, I an; he Science Founda ion, I eland; he Is-
i u o Nazionale di Fisica Nuclea e, I aly; he Ko ean Minis y o Educa ion, Science and Tech-
nology and he Wo ld Class Uni e si y p og am o NRF, Ko ea; he Li huanian Academy o
Sciences; he Mexican Funding Agencies (CINVESTAV, CONACYT, SEP, and UASLP-FAI); he
Pakis an A omic Ene gy Commission; he S a e Commission o Scien i ic Resea ch, Poland; he
Fundac¸˜
ao pa a a Ciˆ
encia e a Tecnologia, Po ugal; JINR (A menia, Bela us, Geo gia, Uk aine,
Uzbekis an); he Minis y o Science and Technologies o he Russian Fede a ion, and Russian
Minis y o A omic Ene gy; he Minis y o Science and Technological De elopmen o Se -
bia; he Minis e io de Ciencia e Inno aci´
on, and P og ama Consolide -Ingenio 2010, Spain; he
Swiss Funding Agencies (ETH Boa d, ETH Zu ich, PSI, SNF, UniZH, Can on Zu ich, and SER);
he Na ional Science Council, Taipei; he Scien i ic and Technical Resea ch Council o Tu key,
and Tu kish A omic Ene gy Au ho i y; he Science and Technology Facili ies Council, UK; he
US Depa men o Ene gy, and he US Na ional Science Founda ion.
Indi iduals ha e ecei ed suppo om he Ma ie-Cu ie p og amme and he Eu opean Re-
sea ch Council (Eu opean Union); he Le en is Founda ion; he A. P. Sloan Founda ion; he
Alexande on Humbold Founda ion; he Associazione pe lo S iluppo Scien i ico e Tecno-
logico del Piemon e (I aly); he Belgian Fede al Science Policy O ice; he Fonds pou la Fo ma-
ion `
a la Reche che dans l’´
ındus ie e dans l’ ´
Ag icul u e (FRIA-Belgium); and he Agen schap
oo Inno a ie doo We enschap en Technologie (IWT-Belgium).

15
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20 9 Conclusions
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21
A The CMS Collabo a ion
Ye e an Physics Ins i u e, Ye e an, A menia
V. Khacha yan, A.M. Si unyan, A. Tumasyan
Ins i u ¨u Hochene giephysik de OeAW, Wien, Aus ia
W. Adam, T. Be gaue , M. D agice ic, J. E ¨
o, C. Fabjan, M. F iedl, R. F ¨
uhwi h, V.M. Ghe e,
J. Hamme 1, S. H¨
ansel, C. Ha l, M. Hoch, N. H¨
o mann, J. H ubec, M. Jei le , G. Kasieczka,
W. Kiesenho e , M. K amme , D. Liko, I. Mikulec, M. Pe nicka, H. Roh inge , R. Sch¨
o beck,
J. S auss, A. Tau ok, F. Teischinge , W. Wal enbe ge , G. Walzel, E. Widl, C.-E. Wulz
Na ional Cen e o Pa icle and High Ene gy Physics, Minsk, Bela us
V. Mossolo , N. Shumeiko, J. Sua ez Gonzalez
Uni e si ei An we pen, An we pen, Belgium
L. Benucci, L. Cea d, K. Ce ny, E.A. De Wol , X. Janssen, T. Maes, L. Mucibello, S. Ochesanu,
B. Roland, R. Rougny, M. Sel aggi, H. Van Hae e mae , P. Van Mechelen, N. Van Remo el
V ije Uni e si ei B ussel, B ussel, Belgium
V. Adle , S. Beauce on, F. Blekman, S. Blywee , J. D’Hond , O. De oede, A. Kaloge opoulos,
J. Maes, M. Maes, S. Ta e nie , W. Van Doninck, P. Van Mulde s, G.P. Van Onsem, I. Villella
Uni e si ´e Lib e de B uxelles, B uxelles, Belgium
O. Cha a , B. Cle baux, G. De Len decke , V. De o, A.P.R. Gay, G.H. Hammad, T. H eus,
P.E. Ma age, L. Thomas, C. Vande Velde, P. Vanlae , J. Wickens
Ghen Uni e si y, Ghen , Belgium
S. Cos an ini, M. G unewald, B. Klein, A. Ma ino , D. Ryckbosch, F. Thyssen, M. Ty ga ,
L. Vanelde en, P. Ve willigen, S. Walsh, N. Zaganidis
Uni e si ´e Ca holique de Lou ain, Lou ain-la-Neu e, Belgium
S. Basegmez, G. B uno, J. Caud on, J. De Fa e eau De Jene e , C. Delae e, P. Demin, D. Fa a ,
A. Giammanco, G. G ´
egoi e, J. Holla , V. Lemai e, J. Liao, O. Mili a u, S. O yn, D. Pagano,
A. Pin, K. Pio zkowski, L. Que enmon , N. Schul
Uni e si ´e de Mons, Mons, Belgium
N. Beliy, T. Caebe gs, E. Daubie
Cen o B asilei o de Pesquisas Fisicas, Rio de Janei o, B azil
G.A. Al es, D. De Jesus Damiao, M.E. Pol, M.H.G. Souza
Uni e sidade do Es ado do Rio de Janei o, Rio de Janei o, B azil
W. Ca alho, E.M. Da Cos a, C. De Oli ei a Ma ins, S. Fonseca De Souza, L. Mundim,
H. Nogima, V. Ogu i, W.L. P ado Da Sil a, A. San o o, S.M. Sil a Do Ama al, A. Sznajde ,
F. To es Da Sil a De A aujo
Ins i u o de Fisica Teo ica, Uni e sidade Es adual Paulis a, Sao Paulo, B azil
F.A. Dias, M.A.F. Dias, T.R. Fe nandez Pe ez Tomei, E. M. G ego es2, F. Ma inho, S.F. No aes,
Sand a S. Padula
Ins i u e o Nuclea Resea ch and Nuclea Ene gy, So ia, Bulga ia
N. Da meno 1, L. Dimi o , V. Genche 1, P. Iaydjie 1, S. Pipe o , M. Rodozo , S. S oyko a,
G. Sul ano , V. Tcholako , R. T ayano , I. Vanko
22 A The CMS Collabo a ion
Uni e si y o So ia, So ia, Bulga ia
M. Dyulenda o a, R. Hadjiiska, V. Kozhuha o , L. Li o , E. Ma ino a, 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, J. Wang, J. Wang, X. Wang,
Z. Wang, M. Yang, 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, W. Li, Y. Mao, S.J. Qian, H. Teng, B. Zhu
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, R. Fe eos, M. Galan i, J. Mousa, C. Nicolaou, F. P ochos, P.A. Razis, H. Rykaczewski
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, M.A. Mahmoud5
Na ional Ins i u e o Chemical Physics and Biophysics, Tallinn, Es onia
A. Hek o , M. Kadas ik, K. Kannike, 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
Helsinki Ins i u e o Physics, Helsinki, Finland
S. Czella , J. H¨
a k¨
onen, A. Heikkinen, V. Ka im¨
aki, R. Kinnunen, J. Klem, 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, 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
Labo a oi e Lep ince-Ringue , Ecole Poly echnique, IN2P3-CNRS, Palaiseau, F ance
S. Ba ioni, F. Beaude e, L. Bianchini, M. Bluj6, C. B ou in, P. Busson, C. Cha lo , L. Dob zynski,
R. G anie de Cassagnac, M. Haguenaue , P. Min´
e, C. Mi ono , C. Ochando, P. Paganini,
S. Po eboeu , D. Sabes, R. Sale no, Y. Si ois, C. Thiebaux, B. Wyslouch7, A. Zabi
23
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 am8, J. And ea, A. Besson, D. Bloch, D. Bodin, J.-M. B om, M. Ca daci, E.C. Chabe ,
C. Colla d, E. Con e8, F. D ouhin8, C. Fe o, J.-C. Fon aine8, D. Gel´
e, U. Goe lach, S. G ede ,
P. Juillo , M. Ka im8, 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, N. Beaupe e, M. Bedjidian, O. Bondu, G. Boudoul, D. Boumediene, H. B un,
N. Chanon, R. Chie ici, D. Con a do, P. Depasse, H. El Mamouni, A. Falkiewicz, 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 , H. Xiao
E. And onikash ili Ins i u e o Physics, Academy o Science, Tbilisi, Geo gia
V. Roinish ili
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 , M. E dmann, J. F angenheim, T. Hebbeke , A. Hinzmann, K. Hoep ne ,
C. Ho , T. Klimko ich, D. Klingebiel, P. K euze 1, D. Lanske†, C. Magass, G. Mase i,
M. Me schmeye , A. Meye , P. Papacz, H. Pie a, H. Rei hle , S.A. Schmi z, L. Sonnenschein,
J. S eggemann, D. Teyssie
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 gholz9, K. Bo as, A. Caki , A. Campbell,
E. Cas o, D. Dammann, G. Ecke lin, D. Ecks ein, A. Flossdo , G. Flucke, A. Geise , I. Glushko ,
J. Hauk, H. Jung, M. Kasemann, I. Ka ko , P. Ka sas, C. Kleinwo , H. Kluge, A. Knu sson,
D. K ¨
ucke , E. Kuzne so a, W. Lange, W. Lohmann9, R. Mankel, M. Ma ien eld, I.-A. Melze -
Pellmann, A.B. Meye , J. Mnich, A. Mussgille , J. Olzem, A. Pa en i, A. Raspe eza, A. Ra al,
R. Schmid 9, T. Schoe ne -Sadenius, N. Sen, M. S ein, J. Tomaszewska, D. Volyanskyy, R. Walsh,
C. Wissing
Uni e si y o Hambu g, Hambu g, Ge many
C. Au e mann, S. Bob o skyi, J. D aege , H. Ende le, U. Gebbe , K. Kaschube, G. Kaussen,
R. Klanne , B. Mu a, S. Naumann-Emme, F. Nowak, N. Pie sch, C. Sande , H. Sche le ,
P. Schlepe , M. Sch ¨
ode , T. Schum, J. Schwand , A.K. S i as a a, H. S adie, G. S einb ¨
uck,
J. Thomsen, R. Wol
Ins i u ¨u Expe imen elle Ke nphysik, Ka ls uhe, Ge many
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, S.M. Heindl, M. Hein ich, H. Held, K.H. Ho mann, S. Honc,
30 A The CMS Collabo a ion
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 han1, 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, R. Cla e, J. Ellison, J.W. Ga y, F. Gio dano, G. Hanson, G.Y. Jeng, S.C. Kao, F. Liu,
H. Liu, A. Lu h a, H. Nguyen, G. Pasz o 38, A. Sa pa hy, 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, E. Dusinbe e, D. E ans, F. Gol , A. Holzne , R. Kelley,
M. Lebou geois, J. Le s, B. Mangano, J. Muelmens aed , S. Padhi, C. Palme , G. Pe ucciani,
H. Pi, M. Pie i, R. Ranie i, M. Sani, V. Sha ma1, S. Simon, Y. Tu, A. Va ak, F. W¨
u hwein,
A. Yagil
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, 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. Bo nheim, J. Bunn, Y. Chen, M. Ga aullin, D. Kci a, V. Li ine, Y. Ma, A. Mo , H.B. Newman,
C. Rogan, 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,
N. Te en ye , 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, 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 , A. Cha e jee, S. Das, N. Egge , L.J. Fields, L.K. Gibbons, B. Hel sley,
W. Hopkins, A. Khukhunaish ili, B. K eis, V. Kuzne so , G. Nicolas Kau man, J.R. Pa e son,
D. Puigh, D. Riley, A. Ryd, 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 , M. Dema eau, D.P. Ea ly,
V.D. El i a, I. Fisk, J. F eeman, Y. Gao, E. Go schalk, D. G een, K. Gun ho i, O. Gu sche,
A. Hahn, J. Hanlon, R.M. Ha is, J. Hi schaue , B. Hoobe man, E. James, H. Jensen, M. Johnson,
U. Joshi, R. Kha iwada, B. Kilmins e , B. Klima, K. Kousou is, S. Kuno i, S. Kwan, P. Limon,
R. Lip on, J. Lykken, K. Maeshima, J.M. Ma a ino, D. Mason, P. McB ide, T. McCauley,
T. Miao, K. Mish a, S. M enna, Y. Musienko39, C. Newman-Holmes, V. O’Dell, S. Popescu40,
R. Po des, O. P oko ye , N. Saoulidou, E. Sex on-Kennedy, S. Sha ma, A. Soha, W.J. Spalding,
L. Spiegel, P. Tan, 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

31
Uni e si y o Flo ida, Gaines ille, USA
D. Acos a, P. A e y, D. Bou ilko , M. Chen, 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 , S. Goldbe g, B. Kim, S. Klimenko,
J. Konigsbe g, A. Ko y o , A. K opi ni skaya, T. Kyp eos, K. Ma che , G. Mi selmakhe ,
L. Muniz, Y. Pakho in, C. P esco , R. Reming on, M. Schmi , B. Scu lock, P. Selle s,
N. Skhi ladze, 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,
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 , 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, E.J. Ga cia-Solis, C.E. Ge be , D.J. Ho man, S. Khala yan, F. Lac oix,
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, K. Cankocak41, W. Cla ida, F. Du u, C.K. Lae, E. McClimen ,
J.-P. Me lo, H. Me me kaya, 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 , M. Mu ay, D. Noonan, V. Radicci, S. Sande s,
J.S. Wood, V. Zhuko a
Kansas S a e Uni e si y, Manha an, USA
T. Bol on, I. Chakabe ia, A. I ano , 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,
G. Gomez Ceballos, M. Goncha o , K.A. Hahn, P. Ha is, Y. Kim, M. Klu e, Y.-J. Lee, W. Li,
C. Loizides, P.D. Luckey, T. Ma, S. Nahn, C. Paus, C. Roland, G. Roland, M. Rudolph,
G.S.F. S ephans, K. Sumo ok, K. Sung, E.A. Wenge , S. Xie, M. Yang, Y. Yilmaz, A.S. Yoon,
M. Zane i
32 A The CMS Collabo a ion
Uni e si y o Minneso a, Minneapolis, USA
P. Cole, S.I. Coope , P. Cushman, B. Dahmes, A. De Benede i, P.R. Dude o, G. F anzoni,
J. Haup , K. Klapoe ke, Y. Kubo a, J. Mans, V. Reko ic, R. Rusack, M. Sasse ille, A. Singo sky
Uni e si y o Mississippi, Uni e si y, USA
L.M. C emaldi, R. Godang, R. K oege , L. Pe e a, R. Rahma , D.A. Sande s, D. Summe s
Uni e si y o Neb aska-Lincoln, Lincoln, USA
K. Bloom, S. Bose, J. Bu , D.R. Claes, A. Dominguez, M. Eads, J. Kelle , T. Kelly, I. K a chenko,
J. Lazo-Flo es, C. Lunds ed , H. Malbouisson, S. Malik, G.R. Snow
S a e Uni e si y o New Yo k a Bu alo, Bu alo, USA
U. Bau , A. Godshalk, I. Iash ili, A. Kha chila a, A. Kuma , K. Smi h
No heas e n Uni e si y, Bos on, USA
G. Al e son, E. Ba be is, D. Baumga el, O. Boe iu, M. Chasco, K. Kaadze, S. Reuc o , J. Swain,
D. Wood, J. Zhang
No hwes e n Uni e si y, E ans on, USA
A. Anas asso , A. Kubik, N. Odell, R.A. O ie zynski, B. Pollack, A. Pozdnyako , M. Schmi ,
S. S oyne , M. Velasco, S. Won
Uni e si y o No e Dame, No e Dame, USA
L. An onelli, D. Be y, M. Hild e h, C. Jessop, D.J. Ka mga d, J. Kolb, T. Kolbe g, K. Lannon,
W. Luo, S. Lynch, N. Ma inelli, D.M. Mo se, T. Pea son, R. Ruch i, J. Slaunwhi e, N. Valls,
J. Wa chol, M. Wayne, J. Ziegle
The Ohio S a e Uni e si y, Columbus, USA
B. Bylsma, L.S. Du kin, J. Gu, C. Hill, P. Killewald, K. Ko o , T.Y. Ling, M. Rodenbu g,
G. Williams
P ince on Uni e si y, P ince on, USA
N. Adam, E. Be y, P. Elme , D. Ge baudo, V. Halyo, P. Hebda, A. Hun , J. Jones, E. Lai d,
D. Lopes Pegna, D. Ma low, T. Med ede a, M. Mooney, J. Olsen, P. Pi ou´
e, X. Quan, H. Saka,
D. S ickland, C. Tully, J.S. We ne , A. Zu anski
Uni e si y o Pue o Rico, Mayaguez, USA
J.G. Acos a, X.T. Huang, A. Lopez, H. Mendez, S. Oli e os, J.E. Rami ez Va gas,
A. Za se klyaniy
Pu due Uni e si y, Wes La aye e, USA
E. Alagoz, V.E. Ba nes, G. Bolla, L. Bo ello, D. Bo ole o, A. E e e , A.F. Ga inkel, Z. Gecse,
L. Gu ay, M. Jones, O. Koybasi, A.T. Laasanen, N. Leona do, C. Liu, V. Ma ousso , P. Me kel,
D.H. Mille , N. Neumeis e , K. Po amianos, I. Shipsey, D. Sil e s, A. S ya ko skiy, H.D. Yoo,
J. Zablocki, Y. Zheng
Pu due Uni e si y Calume , Hammond, USA
P. Jindal, N. Pa asha
Rice Uni e si y, Hous on, USA
C. Boulahouache, V. Cuplo , K.M. Ecklund, F.J.M. Geu s, J.H. Liu, J. Mo ales, B.P. Padley,
R. Redjimi, J. Robe s, J. Zabel
Uni e si y o Roches e , Roches e , USA
B. Be cha , A. Bodek, Y.S. Chung, P. de Ba ba o, R. Demina, Y. Eshaq, H. Flache , A. Ga cia-
33
Bellido, P. Goldenzweig, Y. Go a, J. Han, A. Ha el, D.C. Mine , D. O bake , G. Pe illo,
D. Vishne skiy, M. Zielinski
The Rocke elle Uni e si y, New Yo k, USA
A. Bha i, L. Demo ie , K. Goulianos, G. Lungu, C. Mes opian, M. Yan
Ru ge s, he S a e Uni e si y o New Je sey, Pisca away, USA
O. A amen o , A. Ba ke , D. Duggan, Y. Ge sh ein, R. G ay, E. Halkiadakis, D. Hidas, D. Hi s,
A. La h, S. Panwalka , R. Pa el, A. Richa ds, K. Rose, S. Schne ze , S. Somalwa , R. S one,
S. Thomas
Uni e si y o Tennessee, Knox ille, USA
G. Ce izza, M. Hollingswo h, S. Spanie , Z.C. Yang, A. Yo k
Texas A&M Uni e si y, College S a ion, USA
J. Asaadi, R. Eusebi, J. Gilmo e, A. Gu ola, T. Kamon, V. Kho ilo ich, R. Mon al o,
C.N. Nguyen, J. Pi a ski, A. Sa ono , S. Sengup a, A. Ta a ino , D. Toback, M. Weinbe ge
Texas Tech Uni e si y, Lubbock, USA
N. Akchu in, C. Ba dak, J. Damgo , C. Jeong, K. Ko i anggoon, S.W. Lee, P. Mane, Y. Roh,
A. Sill, I. Voloboue , R. Wigmans, E. Yazgan
Vande bil Uni e si y, Nash ille, USA
E. Appel , E. B ownson, D. Engh, C. Flo ez, W. Gabella, W. Johns, P. Ku , C. Magui e, A. Melo,
P. Sheldon, J. Velko ska
Uni e si y o Vi ginia, Cha lo es ille, USA
M.W. A en on, M. Balazs, S. Bou le, M. Buehle , S. Cone i, B. Cox, B. F ancis, R. Hi osky,
A. Ledo skoy, C. Lin, C. Neu, R. Yohay
Wayne S a e Uni e si y, De oi , USA
S. Gollapinni, R. Ha , P.E. Ka chin, M. Ma son, C. Mils `
ene, A. Sakha o
Uni e si y o Wisconsin, Madison, USA
M. Ande son, M. Bach is, J.N. Bellinge , D. Ca lsmi h, S. Dasu, J. E on, L. G ay, K.S. G ogg,
M. G o he, R. Hall-Wil on1, M. He ndon, P. Klabbe s, J. Klukas, A. Lana o, C. Laza idis,
J. Leona d, D. Lomidze, R. Lo eless, A. Mohapa a, W. Pa ke , D. Reede , I. Ross, A. Sa in,
W.H. Smi h, J. Swanson, M. Weinbe g
†: Deceased
1: Also a CERN, Eu opean O ganiza ion o Nuclea Resea ch, Gene a, Swi ze land
2: Also a Uni e sidade Fede al do ABC, San o And e, B azil
3: Also a Labo a oi e Lep ince-Ringue , Ecole Poly echnique, IN2P3-CNRS, Palaiseau, F ance
4: Also a Suez Canal Uni e si y, Suez, Egyp
5: Also a Fayoum Uni e si y, El-Fayoum, Egyp
6: Also a Sol an Ins i u e o Nuclea S udies, Wa saw, Poland
7: Also a Massachuse s Ins i u e o Technology, Camb idge, USA
8: Also a Uni e si ´
e de Hau e-Alsace, Mulhouse, F ance
9: Also a B andenbu g Uni e si y o Technology, Co bus, Ge many
10: Also a Moscow S a e Uni e si y, Moscow, Russia
11: Also a Ins i u e o Nuclea Resea ch ATOMKI, Deb ecen, Hunga y
12: Also a E¨
o ¨
os Lo ´
and Uni e si y, Budapes , Hunga y
13: Also a Ta a Ins i u e o Fundamen al Resea ch - HECR, Mumbai, India
14: Also a Uni e si y o Vis a-Bha a i, San inike an, India
34 A The CMS Collabo a ion
15: Also a Facol `
a Ingegne ia Uni e si `
a di Roma ”La Sapienza”, Roma, I aly
16: Also a Uni e si `
a della Basilica a, Po enza, I aly
17: Also a Labo a o i Nazionali di Legna o dell’ INFN, Legna o, I aly
18: Also a Cali o nia Ins i u e o Technology, Pasadena, USA
19: Also a Facul y o Physics o Uni e si y o Belg ade, Belg ade, Se bia
20: Also a Uni e si y o Cali o nia, Los Angeles, Los Angeles, USA
21: Also a Uni e si y o Flo ida, Gaines ille, USA
22: Also a Uni e si ´
e de Gen`
e e, Gene a, Swi ze land
23: Also a Scuola No male e Sezione dell’ INFN, Pisa, I aly
24: Also a INFN Sezione di Roma; Uni e si `
a di Roma ”La Sapienza”, Roma, I aly
25: Also a Uni e si y o A hens, A hens, G eece
26: Also a The Uni e si y o Kansas, Law ence, USA
27: Also a Ins i u e o Theo e ical and Expe imen al Physics, Moscow, Russia
28: Also a Paul Sche e Ins i u , Villigen, Swi ze land
29: Also a Uni e si y o Belg ade, Facul y o Physics and Vinca Ins i u e o Nuclea Sciences,
Belg ade, Se bia
30: Also a Adiyaman Uni e si y, Adiyaman, Tu key
31: Also a Me sin Uni e si y, Me sin, Tu key
32: Also a Izmi Ins i u e o Technology, Izmi , Tu key
33: Also a Ka kas Uni e si y, Ka s, Tu key
34: Also a Suleyman Demi el Uni e si y, Ispa a, Tu key
35: Also a Ege Uni e si y, Izmi , Tu key
36: Also a Ru he o d Apple on Labo a o y, Didco , Uni ed Kingdom
37: Also a INFN Sezione di Pe ugia; Uni e si `
a di Pe ugia, Pe ugia, I aly
38: Also a KFKI Resea ch Ins i u e o Pa icle and Nuclea Physics, Budapes , Hunga y
39: Also a Ins i u e o Nuclea Resea ch, Moscow, Russia
40: Also a Ho ia Hulubei Na ional Ins i u e o Physics and Nuclea Enginee ing (IFIN-HH),
Bucha es , Romania
41: Also a Is anbul Technical Uni e si y, Is anbul, Tu key