Strange particle production in pp collisions at root{s}=0.9 and 7 TeV

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-PH-EP/2010-094 2011/05/30 CMS-QCD-10-007 S ange Pa icle P oduc ion in pp Collisions a √s= 0.9 and 7 TeV The CMS Collabo a ion∗ Abs ac The spec a o s ange had ons a e measu ed in p o on-p o on collisions, eco ded by he CMS expe imen a he CERN LHC, a cen e-o -mass ene gies o 0.9 and 7 TeV. The K0 S,Λ, and Ξ−pa icles and hei an ipa icles a e econs uc ed om hei decay opologies and he p oduc ion a es a e measu ed as unc ions o apidi y and ans- e se momen um, pT. The esul s a e compa ed o o he expe imen s and o p edic- ions o he PYTHIA Mon e Ca lo p og am. The pTdis ibu ions a e ound o di e subs an ially om he PYTHIA esul s and he p oduc ion a es exceed he p edic ions by up o a ac o o h ee. 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 :1102.4282 2 [hep-ex] 27 May 2011 1 1 In oduc ion Measu emen s o pa icle yields and spec a a e an essen ial s ep in unde s anding p o on- p o on collisions a he La ge Had on Collide (LHC). The Compac Muon Solenoid (CMS) Collabo a ion has published esul s on spec a o cha ged pa icles a cen e-o -mass ene - gies o 0.9, 2.36, and 7 TeV [1, 2]. In his analysis he measu emen is ex ended o s ange mesons and ba yons (K0 S,Λ,Ξ−)1a cen e-o -mass ene gies o 0.9 and 7 TeV. The in es i- ga ion o s ange had on p oduc ion is an impo an ing edien in unde s anding he na u e o he s ong o ce. The LHC expe imen s ALICE and LHCb ha e ecen ly epo ed esul s on s ange had on p oduc ion a √s=0.9 TeV [3, 4]. In addi ion o esul s a √s=0.9 TeV, we also p esen esul s a √s=7 TeV, opening up a new ene gy egime in which o s udy he s ong in e ac ion. As he s ange qua k is hea ie han up and down qua ks, p oduc ion o s ange had ons is gene ally supp essed ela i e o had ons con aining only up and down qua ks. The amoun o s angeness supp ession is an impo an componen in Mon e Ca lo (MC) models such as PYTHIA [5] and HIJING/BB [6]. Because he h eshold o s ange qua k p oduc ion in a qua k-gluon plasma is much smalle han in a had on gas, an enhancemen in s ange pa icle p oduc ion has equen ly been sugges ed as an indica ion o qua k-gluon plasma o ma ion [7]. This e ec would be u he enhanced in ba yons wi h mul iple s ange qua ks. While a qua k-gluon plasma is mo e likely o be ound in collisions o hea y nuclei, he enhancemen o s ange qua k p oduc ion in high ene gy pp collisions would be a sign o a collec i e e ec , acco ding o some models [8, 9]. In con as , ecen Regge- heo y calcula ions indica e li le change in he a io o K0 S o cha ge pa icle p oduc ion wi h inc easing collision ene gy [10, 11]. Thus, hese measu emen s can be used o cons ain heo ies, p o ide inpu o uning o Mon e Ca lo models, and se e as a e e ence o he in e p e a ion o s angeness p oduc ion esul s in hea y-ion collisions. Minimum bias collisions a he LHC can be classi ied as elas ic sca e ing, inelas ic single- di ac i e dissocia ion (SD), inelas ic double-di ac i e dissocia ion, and inelas ic non-di ac i e sca e ing. The esul s p esen ed he e a e no malized o he sum o double-di ac i e and non-di ac i e in e ac ions, e e ed o as non-single-di ac i e (NSD) in e ac ions [1, 2]. This choice is made o mos closely ma ch he e en selec ion and o compa e wi h p e ious expe i- men s, which o en used simila c i e ia. The K0 S,Λ, and Ξ−a e long-li ed pa icles (cτ>1 cm) and can be iden i ied om hei decay p oduc s o igina ing om a displaced e ex. The pa - icles a e econs uc ed om hei decays: K0 S→π+π−,Λ→pπ−, and Ξ−→Λπ−o e he apidi y ange |y|<2, whe e he apidi y is de ined as y=1 2ln E+pL E−pL,Eis he pa icle ene gy, and pLis he pa icle momen um along he an iclockwise beam di ec ion. Fo each pa icle species, we measu e he p oduc ion a e e sus apidi y and ans e se momen um pT, he a e age pT, he cen al p oduc ion a e dN dy |y≈0, and he in eg a ed yield o |y|<2 pe NSD e en . We compa e ou measu emen s o esul s om Mon e Ca lo models and lowe ene gy da a. 2 CMS expe imen and collec ed da a CMS is a gene al pu pose expe imen a he LHC [12]. The silicon acke , lead- ungs a e c ys al elec omagne ic calo ime e , and b ass-scin illa o had on calo ime e a e all imme sed in a 3.8 T axial magne ic ield while muon de ec o s a e in e spe sed wi h lux e u n s eel ou side o he 6 m diame e supe conduc ing solenoid. The silicon acke is used o econs uc cha ged pa icle ajec o ies wi h |η|<2.5, whe e he pseudo apidi y is de ined as η=−ln an θ 2,θ 1Pa icle-conjuga e s a es a e implied h oughou his pape . 23 S ange pa icle econs uc ion being he pola angle wi h espec o he an iclockwise beam. The acke consis s o laye s o 100×150 µm2pixel senso s a adii less han 15 cm and laye s o s ip senso s, wi h pi ch anging om 80 o 183 µm, co e ing adii om 25 o 110 cm. In addi ion o ba el and endcap de ec o s, CMS has ex ensi e o wa d calo ime y including a s eel and qua z- ib e had on calo ime e (HF), which co e s 2.9 <|η|<5.2. The da a p esen ed in his pape we e collec ed by he CMS expe imen in sp ing 2010 om p o on-p o on collisions a cen e-o -mass ene gies o 0.9 and 7 TeV du ing a pe iod in which he p obabili y o wo collisions in he same bunch c ossing was negligible and he bunch c ossings we e well sepa a ed. The online selec ion o e en s equi ed ac i i y in he beam scin illa o coun e s a 3.23 <|η|< 4.65 in coincidence wi h colliding p o on bunches. The o line selec ion equi ed deposi s o a leas 3 GeV o ene gy in each end o he HF [1], p e e en ially selec ing NSD e en s. A p i- ma y e ex econs uc ed in he acke was equi ed and beam-halo and o he beam- ela ed backg ound e en s we e ejec ed as desc ibed in Re . [1]. The da a selec ed wi h hese c i- e ia con ain 9.08 and 23.86 million e en s a 0.9 and 7 TeV, co esponding o app oxima e in eg a ed luminosi ies o 240 and 480 µb−1, espec i ely. To de e mine he accep ance and e - iciency, minimum-bias Mon e Ca lo samples we e gene a ed a bo h cen e-o -mass ene gies using PYTHIA 6.422 [5] wi h une D6T [13]. These e en s we e passed h ough a CMS de ec o simula ion package based on GEANT 4 [14]. 3 S ange pa icle econs uc ion Ioniza ion deposi s eco ded by he silicon acke a e used o econs uc acks. To maxi- mize econs uc ion e iciency, we use a combined ack collec ion o med om me ging acks ound wi h he s anda d acking desc ibed in Re . [15] and he minimum bias acking de- sc ibed in Re . [1]. Bo h acking collec ions use he same basic algo i hm; he di e ences a e in he equi emen s o seeding, p opaga ing, and il e ing acks. As desc ibed in Re . [15], he K0 Sand Λ(gene ically e e ed o as V0) econs uc ion combines pai s o opposi ely cha ged acks; i he no malized χ2o he i o a common e ex is less han 7, he candida e is kep . The p ima y e ex is e i o each candida e, emo ing he wo acks associa ed wi h he V0candida e. The nex wo pa ag aphs desc ibe he selec ion o candida es o measu emen o V0and Ξ−p ope ies, espec i ely. Selec ion a iables a e measu ed in uni s o σ, he calcula ed unce ain y including all co ela ions. To emo e K0 Spa icles misiden i ied as Λpa icles and ice e sa, he K0 S(Λ)candida es mus ha e a co esponding pπ−(π+π−)mass mo e han 2.5σaway om he wo ld-a e age Λ(K0 S) mass. The p oduc ion c oss sec ions we measu e a e in ended o ep esen he p omp p oduc- ion o K0 Sand Λ, including s ong and elec omagne ic decays. Howe e , V0pa icles can also be p oduced om weak decays and om seconda y nuclea in e ac ions. These unwan ed con- ibu ions a e educed by equi ing ha he V0momen um ec o poin s back o he p ima y e ex. This is done by equi ing he 3D dis ance o closes app oach o he V0 o he p ima y e ex o be less han 3σ. To emo e gene ic p omp backg ounds, he 3D V0 e ex sepa a ion om he p ima y e ex mus be g ea e han 5σand bo h V0daugh e acks mus ha e a 3D dis ance o closes app oach o he p ima y e ex g ea e han 3σ. Wi h he abo e selec ion, he backg ound le el o low ans e se-momen um Λcandida es emains high. The e o e, addi ional cu s a e applied o Λcandida es wi h pT<0.6 GeV/c: •3D sepa a ion be ween he p ima y and Λ e ices >10σ(ins ead o >5σ), • ans e se (2D) sepa a ion be ween he pp collision egion (beamspo ) and Λ e ex >10σ(ins ead o no cu ), whe e he unce ain y is domina ed by he Λ e ex, and 3 •3D impac pa ame e o he pion and p o on acks wi h espec o he p ima y e - ex >(7−2|y|)σ(ins ead o >3σ) whe e yis he apidi y o he Λcandida e. The apidi y dependence is a consequence o he obse a ion ha , o he low ans e se momen um candida es, la ge backg ounds domina e a small apidi y, while low e iciency cha ac e izes he la ge apidi y beha iou . The esul ing mass dis ibu ions o K0 Sand Λcandida es om he 0.9 and 7 TeV da a a e shown in Figs. 1 and 2. The π+π−mass dis ibu ion is i wi h a double Gaussian (wi h a common mean) signal unc ion plus a quad a ic backg ound. The pπ−mass dis ibu ion is i wi h a double Gaussian (common mean) signal unc ion and a backg ound unc ion o he o m AqB, whe e q=Mpπ−−(mp+mπ−),Mpπ−is he pπ−in a ian mass, and Aand Ba e ee pa ame e s. The i ed K0 S(Λ)yields a √s=0.9 and 7 TeV a e 1.4×106(2.8×105)and 6.5× 106(1.5×106), espec i ely. ] 2 in a ian mass [MeV/c − π + π 450 500 550 600 2 Candida es / 1 MeV/c 0 20 40 60 80 100 3 10× 3 10×Yield: 1393 2 Mean: 497.8 MeV/c 2 : 8.4 MeV/cσA g CMS = 0.9 TeVs ] 2 in a ian mass [MeV/c − π + π 450 500 550 600 2 Candida es / 1 MeV/c 0 100 200 300 400 3 10× 3 10×Yield: 6534 2 Mean: 497.8 MeV/c 2 : 8.2 MeV/cσA g CMS = 7 TeVs Figu e 1: The π+π−in a ian mass dis ibu ions om da a collec ed a √s=0.9 TeV (le ) and 7 TeV ( igh ). The solid cu es a e i s o a double Gaussian and quad a ic polynomial. The dashed cu es show he quad a ic backg ound con ibu ion. To econs uc he Ξ−, cha ged acks o he co ec sign a e combined wi h Λcandida es. The χ2p obabili y o he i o a common e ex o he Λand he cha ged ack mus be g ea e han 5%. In his i , he Λcandida e is cons ained o ha e he co ec wo ld-a e age mass [16]. The p ima y e ex is e i o each Ξ−candida e, emo ing all acks associa ed wi h he Ξ−. The Ξ−candida es mus hen pass he ollowing selec ion c i e ia: •3D impac pa ame e wi h espec o he p ima y e ex >2σ o he p o on ack om he Λdecay, >3σ o he π− ack om he Λdecay, and >4σ o he π− ack om he Ξ−decay, •in a ian mass om he π+π−hypo hesis o he acks associa ed wi h he Λcan- dida e a leas 20 MeV/c2away om he wo ld-a e age K0 Smass, •3D impac pa ame e o he Ξ−candida e wi h espec o he p ima y e ex <3σ, •3D sepa a ion be ween Λ e ex and p ima y e ex >10σ, and •3D sepa a ion be ween Ξ− e ex and p ima y e ex >2σ. The mass dis ibu ions o Ξ−candida es om he √s=0.9 and 7 TeV da a a e shown in Fig. 3. The Λπ−mass is i wi h a double Gaussian (wi h a common mean) signal unc ion and a 44 E iciency co ec ion ] 2 in a ian mass [MeV/c − πp 1100 1120 1140 2 Candida es / 0.5 MeV/c 0 5 10 15 20 3 10× 3 10×Yield: 276 2 Mean: 1116.1 MeV/c 2 : 3.6 MeV/cσA g CMS = 0.9 TeVs ] 2 in a ian mass [MeV/c − πp 1100 1120 1140 2 Candida es / 0.5 MeV/c 0 20 40 60 80 100 120 3 10× 3 10×Yield: 1460 2 Mean: 1116.0 MeV/c 2 : 3.4 MeV/cσA g CMS = 7 TeVs Figu e 2: The pπ−in a ian mass dis ibu ions om da a collec ed a √s=0.9 TeV (le ) and 7 TeV ( igh ). The solid cu es a e i s o a double Gaussian signal and a backg ound unc- ion gi en by AqB, whe e q=Mpπ−−(mp+mπ−). The dashed cu es show he backg ound con ibu ion. backg ound unc ion o he o m Aq1/2 +Bq3/2, whe e q=MΛπ−−(mΛ+mπ−)and MΛπ−is he Λπ−in a ian mass. The i ed Ξ−yields a √s=0.9 and 7 TeV a e 6.2×103and 3.4×104, espec i ely. 4 E iciency co ec ion The e iciency co ec ion is de e mined om a Mon e Ca lo simula ion which is used o mea- su e he e ec s o accep ance and he e iciency o e en selec ion (including he igge ) and pa icle econs uc ion. The Mon e Ca lo samples a e eweigh ed o ma ch he obse ed ack mul iplici y in da a, as his has been shown o be an impo an componen o he igge e i- ciency [1, 2]. This is e e ed o as ack weigh ing. The e iciency co ec ion also accoun s o he o he decay channels o he s ange pa icles ha we do no a emp o econs uc , such as K0 S→π0π0. The e iciency is gi en by he numbe o econs uc ed pa icles di ided by he numbe o gene a ed pa icles, subjec o wo modi ica ions. Fi s ly, he e iciency co ec ion is used o ac- coun o candida es om SD e en s. As he esul s a e no malized o NSD e en s, candida es om SD e en s which pass he e en selec ion mus be emo ed. This is done by de ining he e iciency as he numbe o econs uc ed candida es in all e en s di ided by he numbe o gene a ed candida es in NSD e en s. Secondly, he e iciency is modi ied o accoun o he small con ibu ion o econs uc ed non-p omp s ange pa icles which pass he selec ion c i- e ia. This is only an issue o he Λpa icles which ecei e con ibu ions om Ξand Ωdecays. Since hese non-p omp Λpa icles a e p esen in bo h he MC and da a, we modi y he e i- ciency o emo e his con ibu ion by calcula ing he nume a o using all o he econs uc ed s ange pa icles and he denomina o wi h only he p omp gene a ed s ange pa icles. As he MC ails o p oduce enough Ξpa icles (see Sec ion 6), he non-p omp Λ’s a e weigh ed mo e han p omp Λ’s in he e iciency calcula ion. The esul s o his analysis a e p esen ed in e ms o wo kinema ic dis ibu ions: ans e se 5 ] 2 in a ian mass [MeV/c − πΛ 1300 1350 1400 2 Candida es / 2 MeV/c 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 3 10× 3 10×Yield: 6.2 2 Mean: 1322.2 MeV/c 2 : 4.3 MeV/cσA g CMS = 0.9 TeVs ] 2 in a ian mass [MeV/c − πΛ 1300 1350 1400 2 Candida es / 2 MeV/c 0 2 4 6 8 3 10× 3 10×Yield: 34.4 2 Mean: 1322.1 MeV/c 2 : 4.1 MeV/cσA g CMS = 7 TeVs Figu e 3: The Λπ−in a ian mass dis ibu ions om da a collec ed a √s=0.9 TeV (le ) 7 TeV ( igh ). The solid cu es a e i s o a double Gaussian signal and a backg ound unc ion gi en by Aq1/2 +Bq3/2, whe e q=MΛπ−−(mΛ+mπ−). The dashed cu es show he backg ound con ibu ion. momen um and apidi y. Fo all modes, |y|is di ided in o 10 equal size bins om 0 o 2 and pTis di ided in o 20 equal size bins om 0 o 4 GeV/cplus one bin each om 4 o 5 GeV/cand 5 o 6 GeV/c. In addi ion, he V0modes also ha e 6–8 GeV/cand 8–10 GeV/c pTbins. All esul s a e o pa icles wi h |y|<2. The e iciency co ec ion o he V0modes uses a wo-dimensional binning in pTand |y|. Thus, he da a a e di ided in o 240 bins in he |y|,pTplane. The in a ian mass his og ams in each bin a e i o a double Gaussian signal unc ion (wi h a common mean) and a backg ound unc ion. In bins wi h ew en ies, a single Gaussian signal unc ion is used. Fo he Λsample, some bins a e me ged due o spa se popula ions in |y|,pTspace. The me ging is pe o med sepa a ely when measu ing |y|and pTsuch ha he me ging occu s ac oss pTand |y|bins, espec i ely. The e iciency om MC is e alua ed in each bin and applied o he measu ed yield o ob ain he co ec ed yield. The wo-dimensional binning used o he V0e iciency co ec ion g ea ly educes p oblems a ising om emaining di e ences in p oduc ion dynamics be ween he da a and he simula ion. The much smalle sample o Ξ−candida es p e en s he use o 2D binning. Thus, he da a a e di ided in o |y|bins o measu e he |y|dis ibu ion and in o pTbins o measu e he pTdis ibu ion. Howe e , he MC spec a do no ma ch he da a. The e o e, each Mon e Ca lo Ξ−pa icle is weigh ed in pT(|y|) o ma ch he dis ibu ion in da a when measu ing he e iciency e sus |y|(pT). Thus, he MC and da a dis ibu ions a e o ced o ma ch in he a iable o e which we in eg a e o de e mine he e iciency. We e e o his as kinema ic weigh ing. The e iciencies o all h ee pa icles a e shown e sus |y| and pTin Fig. 4. The e iciencies ( o pa icles wi h |y|<2) include he accep ance, e en selec ion, econs uc ion and selec ion, and also accoun o o he decay channels. The inc ease in e iciency wi h pTis due o he imp o emen in acking e iciency as ack pTinc eases and o he selec ion c i e ia designed o emo e p omp decays. The sligh dec ease a high pTis due o pa icles decaying oo a ou o ha e econs uc ed acks. While he e is no cen e-o - mass ene gy dependence on he e iciency e sus pT, pa icles p oduced a √s=7 TeV ha e a highe a e age-pT, esul ing in a highe e iciency when plo ed e sus apidi y. As a check on he abili y o he Mon e Ca lo simula ion o ep oduce he e iciency, he (well- 64 E iciency co ec ion |y| 0 0.5 1 1.5 2 E iciency 0 0.05 0.1 0.15 0.2 0.25 0.3 0 S = 7 TeV: Ks 0 S = 0.9 TeV: Ks Λ = 7 TeV: s Λ = 0.9 TeV: s − Ξ = 7 TeV: s − Ξ = 0.9 TeV: s CMS [GeV/c] T p 0 2 4 6 8 10 E iciency 0 0.1 0.2 0.3 0.4 0 S = 7 TeV: Ks 0 S = 0.9 TeV: Ks Λ = 7 TeV: s Λ = 0.9 TeV: s − Ξ = 7 TeV: s − Ξ = 0.9 TeV: s CMS Figu e 4: To al e iciencies, including accep ance, igge and e en selec ion, econs uc ion and pa icle selec ion, and o he decay modes, as a unc ion o |y|(le ) and pT( igh ) o K0 S, Λ, and Ξ−p oduced p omp ly in he ange |y|<2. E o ba s come om MC s a is ics. known) K0 S,Λ, and Ξ−li e imes a e measu ed. Fo he K0 Smeasu emen , he da a a e di ided in o bins o pTand c , whe e c is calcula ed as c =cmL/pwhe e m,L, and pa e, espec i ely, he mass, decay leng h, and momen um o he pa icle. In each bin he da a is co ec ed by he MC e iciency and he co ec ed yields summed in pT o ob ain he c dis ibu ion. Due o smalle sample sizes, he Λand Ξ−yields a e only measu ed in bins o c . Using he kinema ic weigh ing echnique, he MC e iciency in each bin o c is calcula ed wi h he pTspec um co ec ly weigh ed o ma ch da a. The co ec ed li e ime dis ibu ions, shown in Fig. 5, display exponen ial beha iou . The e ex sepa a ion equi emen s esul in e y low e iciencies and low yields in he i s li e ime bin and a e hus expec ed o ha e some disc epancies. An ac ual measu emen o he li e ime would emo e his issue by using he educed p ope ime, whe e one measu es he li e ime ela i e o he poin a which he pa icle had a chance o be econ- s uc ed. The measu ed alues o he li e imes a e also easonably consis en wi h he wo ld a e ages [16] (shown in Fig. 5) conside ing ha only s a is ical unce ain ies a e epo ed and ha his is no he op imal me hod o a li e ime measu emen . To con e he e iciency co ec ed yields o pe e en yields equi es he ue numbe o NSD e en s, which is ob ained by co ec ing he numbe o selec ed e en s o he e en selec ion ine iciency. The e en selec ion includes bo h he online igge and o line selec ion desc ibed in Sec ion 2. The e en selec ion e iciency is de e mined in wo ways. In he de aul me hod, i is calcula ed di ec ly om he Mon e Ca lo simula ion (app op ia ely weigh ed by he ack mul iplici y o ep oduce he da a). In he al e na i e me hod, he e en selec ion e iciency e - sus ack mul iplici y is de i ed om he Mon e Ca lo. Then, each measu ed e en is weigh ed by he in e se o he e en selec ion e iciency based on i s numbe o acks. The numbe o e en s di ided by he numbe o weigh ed e en s gi es he e en selec ion e iciency. How- e e , since he e en selec ion equi es a p ima y e ex, no e en s will ha e ewe han wo acks. The e o e, he Mon e Ca lo is also used o de e mine he ac ion o NSD e en s which ha e ewe han wo acks and he e en selec ion e iciency is adjus ed o include his e ec . In bo h me hods, he e en selec ion e iciency accoun s o unwan ed SD e en s which pass he e en selec ion. The nume a o in he e iciency a io con ains all selec ed e en s, including 7 c [cm] 0 S K 0 2 4 6 8 10 12 -1 ) dN / dc (cm) NSD (1/N -2 10 -1 10 0.1 ps± = 89.0 τ = 7 TeV: s 0.2 ps± = 89.3 τ = 0.9 TeV: s CMS 0.05 ps± = 89.53 PDG τ S a is ical unce ain ies only c [cm]Λ 0 2 4 6 8 10 12 14 16 18 20 -1 ) dN / dc (cm) NSD (1/N -2 10 -1 10 1.1 ps± = 261.4 τ = 7 TeV: s 3.1 ps± = 264.6 τ = 0.9 TeV: s CMS 2.0 ps± = 263.1 PDG τ S a is ical unce ain ies only c [cm] − Ξ 0 1 2 3 4 5 6 7 8 9 10 -1 ) dN / dc (cm) NSD (1/N -3 10 -2 10 5 ps± = 167 τ = 7 TeV: s 8 ps± = 178 τ = 0.9 TeV: s CMS 1.5 ps± = 163.9 PDG τ S a is ical unce ain ies only Figu e 5: K0 S(le ), Λ(middle), and Ξ−( igh ) co ec ed decay ime dis ibu ions a √s=0.9 and 7 TeV. The alues o he li e imes, de i ed om a i wi h an exponen ial unc ion (solid line), a e shown in he legend along wi h he wo ld-a e age alue. The e o ba s and unce ain ies on he li e imes e e o he s a is ical unce ain y only. single-di ac i e e en s, while he denomina o con ains all NSD e en s. 5 Sys ema ic unce ain ies The sys ema ic unce ain ies, epo ed in Table 1, a e di ided in o wo ca ego ies: no maliza- ion unce ain ies, which only a ec he o e all no maliza ion, and poin - o-poin unce ain- ies, which may also a ec he shape o he pTand |y|dis ibu ions. The lis below summa izes he sou ce and e alua ion o he poin - o-poin sys ema ic unce - ain ies. •Kinema ic weigh ing e sus 2D binning: The e iciency co ec ions using he 1D kine- ma ic weigh ing echnique (used o he Ξ−analysis) and he 2D binning echnique (used o he V0analysis) we e compa ed by measu ing he e iciency wi h bo h me hods on he highes s a is ics channel (K0 Sa 7 TeV). •Non-p omp Λ: The con ibu ion o non-p omp Λdecays is a ied by a ac o o wo in he simula ion. •MC une: The nominal e iciency calcula ed om he de aul PYTHIA 6 D6T une [13] is compa ed o he e iciency ob ained om he PYTHIA 6 Pe ugia0 (P0) une [17] and PYTHIA 8 [18]. •Va ia ion o econs uc ion cu s: The ollowing cu s a e a ied o all h ee modes: V0 e ex sepa a ion signi icance (±2σ), 3D impac pa ame e o V0and Ξ−(±2σ), 3D impac pa ame e o acks (±2σ), cu on K0 S(Λ)mass o Λ(K0 S)candida es (±1.5σ), and inc ease o numbe o hi s equi ed on each ack om 3 o 5. Fo he Ξ−, addi ional cu s we e a ied: he Ξ− e ex sepa a ion signi icance (±1σ) and Ξ− e ex i p obabili y (±3%). •De ached pa icle econs uc ion: Finding ha he co ec ed li e ime dis ibu ions a e exponen ial wi h he co ec li e ime is a e i ica ion o ou unde s anding o he econs uc ion e iciency e sus decay leng h. The sys ema ic unce ain y is aken as he di e ence be ween he i ed li e imes and he wo ld-a e age li e imes [16]. While he K0 Sand Λli e imes a e wi hin 1% o he wo ld-a e age, a 2% sys ema ic unce ain y is conse a i ely assigned. 14 6 Resul s [GeV/c] T p 0 2 4 6 8 10 ) 0 S ) / N(KΛN( 0 0.2 0.4 0.6 0.8 1 = 7 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 = 0.9 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 CMS [GeV/c] T p 0 1 2 3 4 5 6 )Λ) / N( − ΞN( 0 0.05 0.1 0.15 0.2 0.25 = 7 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 = 0.9 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 CMS Figu e 8: N(Λ)/N(K0 S)(le ) and N(Ξ−)/N(Λ)( igh ) in NSD e en s e sus pT. The inne e ical e o ba s (when isible) show he s a is ical unce ain ies, he ou e he s a is ical and all sys ema ic unce ain ies summed in quad a u e. Resul s a e shown o h ee PYTHIA p e- dic ions a each cen e-o -mass ene gy. om STAR [24] and a √s=0.9 TeV esul s om ALICE [3]. These h ee esul s show a ema k- able consis ency ac oss a wide a ie y o collision ene gies. In con as , he CDF alues o N(Λ)/N(K0 S)[26] a e signi ican ly highe han he CMS esul s while he CDF measu emen s o N(Ξ−)/N(Λ)[25] a e lowe , albei wi h less signi icance. Reducing he pTdis ibu ions o a single alue, he a e age pT, we compa e he CMS esul s wi h ea lie esul s a lowe ene gies in Fig. 11 [3, 24, 26–32]. The CMS esul s a e in excellen ag eemen wi h he ecen ALICE measu emen s a 0.9 TeV. The CMS esul s con inue he o e all end o inc easing a e age pTwi h inc easing pa icle mass and inc easing cen e-o - mass ene gy. 6.3 Analysis o p oduc ion a e As a measu e o he o e all p oduc ion a e in NSD e en s, dN dy |y≈0and he o al yield o |y|<2 we e ex ac ed and abula ed in Table 4. The quan i y dN dy |y≈0is he a e age alue o dN dy o e he egion |y|<0.2. The in eg a ed yields o |y|<2 a e ob ained by in eg a ing he pTspec a, using he Tsallis unc ion i o accoun o pa icles abo e he measu ed pT ange. The cen al p oduc ion a es o K0 S,Λ, and Ξ−a e compa ed o p e ious esul s in Fig. 12. The esul s show he expec ed inc ease in p oduc ion wi h cen e-o -mass ene gy wi h li le e idence o a di e ence due o beam pa icles. As he ALICE esul s a e no malized o all inelas ic collisions, hey a e expec ed o be somewha lowe han he CMS esul s. The p oduc ion a ios N(K0 S)/N(Λ)and N(Ξ−)/N(Λ) e sus |y|a e shown in Fig. 13. The apidi y dis ibu ions a e e y la and, as obse ed in he pTdis ibu ions o Fig. 8, show no dependence on cen e-o -mass ene gy. Th ee PYTHIA p edic ions a each cen e-o -mass ene gy a e also shown in Fig. 13. These esul s con i m wha can al eady be seen in he compa isons shown in he le panes o Fig. 6; PYTHIA unde es ima es he p oduc ion o s ange pa icles and he disc epancy g ows wi h pa icle mass. 6.3 Analysis o p oduc ion a e 15 [GeV/c] T p 0 1 2 3 4 5 6 -1 (GeV/c) T /dp − Ξ ) dN NSD (1/N -5 10 -4 10 -3 10 -2 10 CMS: pp @ 7 TeV CMS: pp @ 0.9 TeV @ 1.96 TeVpCDF: p ALICE: pp @ 0.9 TeV STAR: pp @ 0.2 TeV 0 1 2 3 4 5 6 -1 (GeV/c) T /dp Λ ) dN NSD (1/N -4 10 -3 10 -2 10 -1 10 0 1 2 3 4 5 6 -1 (GeV/c) T /dp 0 S K ) dN NSD (1/N -4 10 -3 10 -2 10 -1 10 1CMS Figu e 9: K0 S( op), Λ(middle), and Ξ−(bo om) p oduc ion pe e en e sus pT. The e o ba s on he CMS esul s show he combined s a is ical, poin - o-poin sys ema ic, and no maliza ion sys ema ic unce ain ies. The e o ba s on he CDF [25], ALICE [3], and STAR [24] esul s show he combined s a is ical and sys ema ic unce ain ies. The CMS, CDF, and STAR esul s a e no malized o NSD e en s while he ALICE esul s a e no malized o all inelas ic e en s. Table 4: dN dy |y≈0and in eg a ed yields (|y|<2.0)pe NSD e en om da a. In each da a column, he i s unce ain y is s a is ical and he second is sys ema ic. √s=0.9 TeV √s=7 TeV Pa icle dN dy |y≈0NdN dy |y≈0N K0 S0.205±0.001±0.015 0.784±0.002±0.056 0.346±0.001±0.025 1.341±0.001±0.097 Λ0.108±0.001±0.012 0.404±0.004±0.046 0.189±0.001±0.022 0.717±0.005±0.082 Ξ−0.011±0.001±0.001 0.043±0.001±0.006 0.021±0.001±0.003 0.080±0.001±0.011 16 6 Resul s [GeV/c] T p 0 1 2 3 4 5 6 )Λ ) / N( − ΞN( 0 0.1 0.2 0.3 @ 1.96 TeVpCDF: p @ 1.8 TeVpCDF: p @ 0.63 TeVpCDF: p ALICE: pp @ 0.9 TeV STAR: pp @ 0.2 TeV CMS: pp @ 7 TeV CMS: pp @ 0.9 TeV 0 1 2 3 4 5 6 ) 0 S ) / N(KΛN( 0.5 1 1.5 CMS Figu e 10: Ra io o Λ o K0 Sp oduc ion ( op) and Ξ− o Λp oduc ion (bo om) e sus pT. The CMS, ALICE [3], and STAR [24] e o ba s include he s a is ical and sys ema ic unce ain ies. The CDF e o ba s include he s a is ical unce ain ies o N(Λ)/N(K0 S)[26] and he s a is i- cal and sys ema ic unce ain ies o N(Ξ−)/N(Λ)[25]. The CDF N(Λ)/N(K0 S)bin sizes a e doubled o educed luc ua ions. Fo expe imen s in which he binning o Λand Ξ−is di e - en (ALICE and STAR), bins a e me ged o p o ide common bin anges in he N(Ξ−)/N(Λ) dis ibu ion. 6.3 Analysis o p oduc ion a e 17 [TeV] s -1 10 1 10 [GeV/c] − Ξ 〉 T p〈 0.6 0.8 1 1.2 − Ξ CMS (pp))pE735 (p ALICE (pp) )pUA5 (p STAR (pp) [GeV/c] Λ 〉 T p〈 0.6 0.7 0.8 0.9 1 1.1 Λ CMS (pp) )pCDF (p )pE735 (p ALICE (pp) )pUA5 (p STAR (pp) [GeV/c] 0 S K 〉 T p〈 0.5 0.6 0.7 0.8 0 S K CMS (pp) )pCDF (p ALICE (pp) )pUA5 (p STAR (pp) CMS Figu e 11: A e age pT o K0 S( op), Λ(middle), and Ξ−(bo om), as a unc ion o he cen e-o - mass ene gy. The CMS measu emen s a e o |y|<2. The o he esul s a e om UA5 [27–31] (p¯ p collisions co e ing |y|<2.5, |y|<2, and |y|<3 o K0 S,Λ, and Ξ−, espec i ely), E735 [32] (p¯ p collisions using acks wi h −0.36 <η<1.0), CDF [26] (p¯ p collisions co e ing |η|<1.0), STAR [24] (pp collisions co e ing |y|<0.5), and ALICE [3] (pp collisions co e ing |y|<0.75 o K0 Sand Λand |y|<0.8 o Ξ−). Some poin s ha e been sligh ly o se om he ue ene gy o imp o e isibili y. The e ical ba s indica e he s a is ical and sys ema ic unce ain ies (when a ailable) summed in quad a u e. 18 6 Resul s [TeV] s -1 10 1 10 0≈y /dy − Ξ ) dN e (1/N 0 0.005 0.01 0.015 0.02 0.025 − Ξ CMS NSD (pp) ALICE INEL (pp) STAR NSD (pp) 0≈y /dy Λ ) dN e (1/N 0.1 0.15 0.2 Λ CMS NSD (pp) ALICE INEL (pp) STAR NSD (pp) 0≈y /dy 0 S K ) dN e (1/N 0.1 0.15 0.2 0.25 0.3 0.35 S 0 K CMS NSD (pp) )pCDF MB (p ALICE INEL (pp) )pUA5 NSD (p STAR NSD (pp) CMS Figu e 12: The cen al apidi y p oduc ion a e o K0 S( op), Λ(middle), and Ξ−(bo om), as a unc ion o he cen e-o -mass ene gy. The p e ious esul s a e om UA5 [29, 30] (p¯ p), CDF [33] (p¯ p), STAR [24] (pp), and ALICE [3] (pp). The CMS, UA5, and STAR esul s a e no malized o NSD e en s. The CDF esul s a e no malized o e en s passing hei igge and e en selec ion de ined chie ly by ac i i y in bo h sides o he de ec o , a leas ou acks, and a p ima y e - ex. The ALICE esul s a e no malized o all inelas ic e en s. Some poin s ha e been sligh ly o se om he ue ene gy o imp o e isibili y. The e ical ba s indica e he s a is ical unce - ain ies o he UA5 and CDF esul s and he combined s a is ical and sys ema ic unce ain ies o he CMS, ALICE, and STAR esul s. 19 |y| 0 0.5 1 1.5 2 ) 0 S ) / N(KΛN( 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 = 7 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 = 0.9 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 CMS |y| 0 0.5 1 1.5 2 )Λ) / N( − ΞN( 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 = 7 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 = 0.9 TeVs PYTHIA6 D6T PYTHIA6 P0 PYTHIA8 CMS Figu e 13: The p oduc ion a ios N(Λ)/N(K0 S)(le ) and N(Ξ−)/N(Λ)( igh ) in NSD e en s e sus |y|. The inne e ical e o ba s (when isible) show he s a is ical unce ain ies, he ou e he s a is ical and all sys ema ic unce ain ies summed in quad a u e. Resul s a e shown o h ee PYTHIA p edic ions a each cen e-o -mass ene gy. Table 5 shows a compa ison o he p oduc ion a e o da a o PYTHIA 6 wi h he D6T une. The le column shows a la ge inc ease in he s ange pa icle p oduc ion c oss sec ion as he cen e-o -mass ene gy inc eases om 0.9 o 7 TeV. The sys ema ic unce ain ies o his a io a e educed as he same unce ain y a ec s bo h samples nea ly equally. The esul s o K0 S and Λa e consis en wi h he inc ease obse ed in inclusi e cha ged pa icle p oduc ion [1, 2] (5.82 3.48 =1.67)while he Ξ− esul s show a sligh ly g ea e inc ease. The inc ease in pa icle p oduc ion om 0.9 o 7 TeV is no well modelled by PYTHIA 6. Ano he ea u e, seen in he igh column, is he de ici o s ange pa icles p oduced by PYTHIA 6. The de ici o K0 Spa icles in he MC, 15% (28%) low a 0.9 (7) TeV, is consis en wi h he esul s ound in he p oduc ion o cha ged pa icles [1, 2]. Howe e , he de ici is much wo se as he mass inc eases, esul ing in a 63% educ ion in Ξ−pa icles in MC compa ed o da a a √s=7 TeV. While alues a e only p esen ed o PYTHIA 6 wi h he D6T une, he same ea u es a e also e iden o he o he wo PYTHIA compa isons in he apidi y dis ibu ion plo s in Fig. 6. Table 5: Compa ison o s angeness p oduc ion a es be ween PYTHIA 6 Mon e Ca lo (D6T) and da a. In each column, he i s unce ain y is s a is ical and he second is sys ema ic. Pa icle "dN dy |y≈0(7 TeV) dN dy |y≈0(0.9 TeV)# "dN dy |y≈0(MCD6T) dN dy |y≈0(Da a)# Da a MC (D6T) √s=0.9 TeV √s=7 TeV K0 S1.69 ±0.01 ±0.06 1.42 0.852 ±0.005 ±0.061 0.717 ±0.001 ±0.052 Λ1.75 ±0.02 ±0.08 1.48 0.606 ±0.007 ±0.070 0.514 ±0.003 ±0.059 Ξ−1.93 ±0.10 ±0.09 1.51 0.477 ±0.021 ±0.064 0.373 ±0.010 ±0.050 7 Conclusions This a icle p esen s a s udy o he p oduc ion o K0 S,Λ, and Ξ−pa icles in p o on-p o on col- lisions a cen e-o -mass ene gies 0.9 and 7 TeV. By ully exploi ing he low-momen um ack 20 7 Conclusions econs uc ion capabili ies o CMS, we ha e measu ed he ans e se-momen um dis ibu ion o hese s ange pa icles down o ze o. F om his sample o 10 million s ange pa icles, he ans e se momen um dis ibu ions we e measu ed ou o 10 GeV/c o K0 Sand Λand ou o 6 GeV/c o Ξ−. We i hese dis ibu ions wi h a Tsallis unc ion o ob ain in o ma ion on he exponen ial decay a low pTand he powe -law beha iou a high pT. All species show a la ening o he exponen ial decay as he cen e-o -mass ene gy inc eases. While he ba yons show li le change in he high-pT egion, he K0 Spowe -law pa ame e dec eases om 7.8 o 6.9. The a e age pT alues, calcula ed di ec ly om he da a, a e ound o inc ease wi h pa icle mass and cen e-o -mass ene gy, in ag eemen wi h p edic ions and o he expe imen al esul s. While he PYTHIA pTdis ibu ions used in his analysis show signi ican a ia ion based on une and e sion, hey a e all b oade han he da a dis ibu ions. We ha e also measu ed he p oduc ion e sus apidi y and ex ac ed he alue o dN/dy in he cen al apidi y egion. The inc ease in p oduc ion o s ange pa icles as he cen e-o - mass ene gy inc eases om 0.9 o 7 TeV is app oxima ely consis en wi h he esul s o in- clusi e cha ged pa icles. Howe e , as in he inclusi e cha ged pa icle case, PYTHIA ails o ma ch his inc ease. Fo K0 Sp oduc ion, he disc epancy is simila o wha has been ound in cha ged pa icles. Howe e , he de ici be ween PYTHIA and da a is signi ican ly la ge o he wo hype ons a bo h ene gies, eaching a ac o o h ee disc epancy o Ξ−p oduc ion a √s=7 TeV. I a qua k-gluon plasma o o he collec i e e ec s we e p esen , we migh ex- pec an enhancemen o double-s ange ba yons o single-s ange ba yons and/o an enhance- men o s ange ba yons o s ange mesons. Howe e , he p oduc ion a ios N(Λ)/N(K0 S)and N(Ξ−)/N(Λ) e sus apidi y and ans e se momen um show no change wi h cen e-o -mass ene gy. Thus, he de iciency in PYTHIA is likely o igina ing om pa ame e s egula ing he equency o s ange qua ks appea ing in colou s ings. The a ie y o measu emen s p e- sen ed he e can be used o une PYTHIA and o he models as well as a baseline o unde s and measu emen s o s angeness p oduc ion in hea y-ion collisions. 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, and acknowledge suppo om: FMSR (Aus ia); FNRS and FWO (Bel- gium); CNPq, CAPES, FAPERJ, and FAPESP (B azil); MES (Bulga ia); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (C oa ia); RPF (Cyp us); Academy o Sci- ences and NICPB (Es onia); Academy o Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (F ance); BMBF, DFG, and HGF (Ge many); GSRT (G eece); OTKA and NKTH (Hunga y); DAE and DST (India); IPM (I an); SFI (I eland); INFN (I aly); NRF and WCU (Ko ea); LAS (Li huania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakis an); SCSR (Poland); FCT (Po ugal); JINR (A menia, Bela us, Geo gia, Uk aine, Uzbekis an); MST and MAE (Russia); MSTD (Se bia); MICINN and CPAN (Spain); Swiss Funding Agencies (Swi ze - land); NSC (Taipei); TUBITAK and TAEK (Tu key); STFC (Uni ed Kingdom); DOE and NSF (USA). 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Kilmins e , B. Klima, K. Kousou is, S. Kuno i, S. Kwan, 33 C. Leonidopoulos, 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. Musienko41, C. Newman-Holmes, V. O’Dell, S. Popescu42, 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 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 , 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, E.J. Ga cia-Solis, L. Gau hie , C.E. Ge be , D.J. Ho man, S. Khala yan, 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, K. Cankocak43, 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 34 A The CMS Collabo a ion 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, D. Ralph, 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 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, S. Jain, A. Kha chila a, A. Kuma , S.P. Shipkowski, 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, 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, Z. Hu, M. Jones, O. Koybasi, M. K ess, A.T. Laasanen, N. Leona do, C. Liu, V. Ma ousso , P. Me kel, D.H. Mille , N. Neumeis e , 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 35 Rice Uni e si y, Hous on, USA C. Boulahouache, V. Cuplo , K.M. Ecklund, F.J.M. Geu s, J.H. Liu, 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, R. Co a elli, P. de Ba ba o, R. Demina, Y. Eshaq, H. Flache , A. Ga cia-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, R. Ciesielski, 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, I. Osipenko , 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, J. Damgo , C. Jeong, K. Ko i anggoon, S.W. Lee, 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, S. Tuo, 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, P. Lamichhane, 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, R. Lo eless, A. Mohapa a, 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 36 A The CMS Collabo a ion 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 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 Uni e si ` a degli s udi di Siena, Siena, I aly 19: Also a Cali o nia Ins i u e o Technology, Pasadena, USA 20: Also a Facul y o Physics o Uni e si y o Belg ade, Belg ade, Se bia 21: Also a Uni e si y o Cali o nia, Los Angeles, Los Angeles, USA 22: Also a Uni e si y o Flo ida, Gaines ille, USA 23: Also a Uni e si ´ e de Gen` e e, Gene a, Swi ze land 24: Also a Scuola No male e Sezione dell’ INFN, Pisa, I aly 25: Also a INFN Sezione di Roma; Uni e si ` a di Roma ”La Sapienza”, Roma, I aly 26: Also a Uni e si y o A hens, A hens, G eece 27: Also a The Uni e si y o Kansas, Law ence, USA 28: Also a Ins i u e o Theo e ical and Expe imen al Physics, Moscow, Russia 29: Also a Paul Sche e Ins i u , Villigen, Swi ze land 30: 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 31: Also a Gaziosmanpasa Uni e si y, Toka , Tu key 32: Also a Adiyaman Uni e si y, Adiyaman, Tu key 33: Also a Me sin Uni e si y, Me sin, Tu key 34: Also a Izmi Ins i u e o Technology, Izmi , Tu key 35: Also a Ka kas Uni e si y, Ka s, Tu key 36: Also a Suleyman Demi el Uni e si y, Ispa a, Tu key 37: Also a Ege Uni e si y, Izmi , Tu key 38: Also a Ru he o d Apple on Labo a o y, Didco , Uni ed Kingdom 39: Also a School o Physics and As onomy, Uni e si y o Sou hamp on, Sou hamp on, Uni ed Kingdom 40: Also a INFN Sezione di Pe ugia; Uni e si ` a di Pe ugia, Pe ugia, I aly 41: Also a Ins i u e o Nuclea Resea ch, Moscow, Russia 42: Also a Ho ia Hulubei Na ional Ins i u e o Physics and Nuclea Enginee ing (IFIN-HH), Bucha es , Romania 43: Also a Is anbul Technical Uni e si y, Is anbul, Tu key