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Heavy flavour results from ATLAS P.J.Bella Universite´deGene`ve,1211Gene`ve4,Switzerland Abstract. Aselectionofheavy-flavourphysicsresultsfromtheATLASexperimentispresented, basedon datacollectedinproton-protoncollisionsattheLHCduring2010.Differentialcross-sectionsfortheproduction 2 ofheavyflavours,charmoniumandbottomoniumstatesandD-mesonsarepresentedandcomparedtovarious 1 theoreticalmodels.ResultsofB-hadronlifetimemeasurementsarealsoreported. 0 2 Keywords. HeavyFlavour n a J 4 1 Introduction V] 1 2 Thegoalsoftheheavy-flavourphysicsprogrammeatAT- b / Ge ∫s L = d 7t =Te 1V.4 pb-1 EMlueoctnr odna tdaa 2ta0 120010 x] LduAcStioanrewtiothtienstththeeSotraentidcaarldmMooddeelsl(fSoMrh)eaanvdy-tfloasveoaurcrhpfroor- µ [pT10-1 FFOONNLLLL ((NNLLOO)+NLL) -e new physics through rare decays or new sources of CP σ / d PPyotwhHiae ×g +0P.4y9t hniaorm. p violation.Theseproceedingspresentanon-exhaustivese- d PowHeg+Herwig e lectionofanalysescompletedduring2011basedon2010 10-2 h data,dividedintocross-sectionmeasurements(Section2) [ andlifetimemeasurements(Section3). 1 Details of the ATLAS detector may be found in [1]. 10-3 |η|<2.0 excluding 1.37<|η|<1.52 v The sub-detectorsof greatest importance to the analyses 3 presentedhereare in the InnerDetector (ID)tracker and NLL ATLAS 3 Muon Spectrometer (MS) systems. In addition, in many FO1.5 9 σ 4 cases the data collectionhas reliedon specific B-physics σ/ triggerselections implementedin the HigherLevelTrig- . 1 ger(HLT). 1 0 2 1 2 Cross-sectionmeasurements : 0.5 v i 2.1 Heavy-flavourcross-sectionmeasurements X 8 10 12 14 16 18 20 22 24 26 p [GeV] ar At low transverse momentum (pT . 30 GeV) the inclu- T sivespectraofchargedelectronsormuonsaredominated Fig. 1. Electron and muon differential cross-sections from by decays of heavy-flavour hadrons. Using 1.13 pb−1 of heavy-flavourproductionasafunctionofp for|η|<2.0exclud- T early2010data,forwhichnon-isolatedlow-p electrons ing1.37 < |η| < 1.52.Theratioofthemeasuredandpredicted T were recorded without any HLT selection bias, electron cross-sectionstotheFONLLcalculationisgiveninthebottom. and muonsignals are extractedfrom the dominantback- ThePYTHIA(LO)cross-sectionsarenormalisedtothedata. groundof QCD fakes, conversions(in the electron case) and pion and kaon decays in flight (in the muon case). 2.2 Quarkoniumcross-sectionmeasurements Thewell-understoodtheoreticalpredictionforthecontri- butionfromW/Z/γ∗productionisthensubtractedtoleave Despitebeingamongthemoststudiedoftheboundquark theheavy-flavourcomponentofthesignal. systems, there is still no clear understanding of the pro- The results [2] for electrons and muons within 7 < duction mechanisms for quarkonium states like the J/ψ p < 26GeVand|η| < 2.0(excluding1.37 < |η| < 1.52) T andtheΥthatcanconsistentlyexplainboththeproduction areshowninFig.1,comparedtothepredictionsfromthe cross-section and spin alignment measurements in e+e−, FONLLtheoreticalframework,inwhichtheheavyquark hadron and heavy ion collisions. Data from the LHC al- productioncross-sectioniscalculatedinpQCDbymatch- lowtestsoftheoreticalmodelsofquarkoniumproduction ingtheFixedOrderNLOtermswithNLLhigh-p resum- T inanewenergyregime. mation. Good agreementwith the FONLL calculation is TheinclusiveJ/ψandΥ(1S)productioncross-sections observed,includingthesensitivitytotheNLLterms. aremeasuredatATLASinthedi-muondecaychannelus- a e-mail:[email protected] ing2.3pb−1and1.1pb−1of2010data,respectively[3,4]. EPJWebofConferences The true numbersof J/ψ or Υ(1S)candidatesare recov- V]102 ered from the observeddi-muon pairs by applying event e Inclusive cross-section G ATLAS |y |<0.75 wficeiiegnhctystfoacutnofroslbdetihnegrdeestpeormnsieneodftahlemdoestteecntotirr,ewlyitfhrothmetehfe- y [nb/ 10 SCpMinS- alignm|yJeJ//ψψn|t< e1n.2velope data.(MonteCarloisusedtoprovidetriggerefficienciesin d 1 T p finerbinningthanwouldbepossiblewiththedatastatis- d tics,withscalefactorsbeingobtainedfromdata.)TheJ/ψ σ2/d10-1 andΥ(1S)yieldsarethendeterminedfromfitstothedi- µ+-)10-2 muonmassinbinsof pTandη. µ→ ATLAS In the J/ψ analysis, a correction for the detector ac- ψ10-3 ∫s= 7 TeV J/ L dt = 2.2 pb-1 ceptance (the probability for muons to fall into the fidu- Br( cialvolumeofdetector)isalsoappliedinordertoobtain 7 8910 20 30 40 50 a total cross-section measurement. Since this correction pJ/ψ [GeV] T dependsontheunknownspinalignmentoftheJ/ψ,anen- velopeofallpossiblepolarisationassumptionsistakenas V] Data 2010 asunreamddeintitonnoalacthceeoprteatniccealcuonrrceecrttiaoinntiys.aFpoprlitehde,aΥn(d1tSh)emfideua-- b/Ge 102 ATLAS NRQCD, Pythia8 p cspiaalccerowshs-esreectthioenmisuroenpsoartreeddienteacrteesdtr,ifcrteeedorefgainoynaosfspuhmaspe- µ-) [ (CdiSreMct oNnlLy)O tions about the spin alignment. The J/ψ and Υ(1S) in- µ+ 10 clusive cross-sections in an example rapidity (y) bin are → showninFig.2.FortheΥ(1S)case,theresultsarecom- S) paredtopredictionsfromPYTHIA8.135usingtheNRQCD 1 ( frameworkandtoNLOQCDcalculationsasimplemented ϒ( 1 in MCFM. Significant deviations from the data are seen BR |yϒ(1S)|<1.2 iftnoeecbdoo-ndthtorwipbrnuetdferiocatbmioounhtsig,ahthfeaorcutmogrhasoMsfstCwtaFotMesatwdtohheeiscThneovwatatirsnocenls.utidmeaatnedy × dy dpT10-1 |ηsµ=|7< T2e.V5,,∫ pLµTd>t=41 .1G3 epVb-1 σ/ OftheJ/ψinclusivecross-section,thenon-promptfrac- 2d 0 5 10 15 20 25 30 tion coming from B-hadrondecays can be identified ex- pϒ(1S) [GeV] perimentallyduetotheassociateddisplacementoftheJ/ψ T vertexinthetransverseplane,L ,duetothelonglifetime xy Fig.2.(Top) Inclusive J/ψproduction cross-sectionasafunc- of the parent B-hadron. A simultaneous unbinned maxi- tionof p fortheexample J/ψrapiditybinof|y| < 0.75,com- mumlikelihoodfittothe J/ψinvariantmassandpseudo- T pared to the equivalent results from CMS. (Bottom) Inclusive properdecaytime,τ = LxymPJ/DψG/pTJ/ψ, isusedtoextract Υ(1S) production cross-section asa function of pT for theex- thisfractionfromthedata,allowingthepromptandnon- ampleΥ(1S)rapiditybin|y| < 1.2,forthegivenkinematicac- promptcross-sectionstobeobtained.Theresultsinanex- ceptanceofthetwomuons.Theresultiscomparedtothecolour- amplerapiditybinareshowninFig.3.Forthenon-prompt singletmodel(CSM)NLOpredictionforwhichtheshadedarea component,good agreementis seen with the predictions showsthechangeinthepredictionwhenvaryingtherenormal- ofFONLL.Forthepromptcomponent,thedataarecon- isation and factorisation scales (nominally m ) by a factor of T sistentwithNNLO∗calculations. two.TheCSMNLOcalculationaccountsonlyfordirectproduc- tionofΥ(1S)mesonsandexcludesanyfeed-downfromexcited states.TheNRQCDpredictionasimplementedinPYTHIA8is alsoshownforaparticularchoiceofparameters. 2.3 Dmesoncross-sectionmeasurements Using an integratedluminosityof1.1 nb−1, D∗±, D± and D± (yield 1546± 81) and D± (yield 304± 51) mesons, S D± charmed mesons with p > 3.5 GeV and |y| < 2.1 massesconsistentwithPDGworldaveragesarefound. s T are reconstructed using tracks measured in the ATLAS UsingMonteCarlotocorrectforthedetectorresponse, ID[5].TakingtheexampleoftheD∗±,whichisidentified the D∗± and D± production cross-sections (in the kine- in the decaychannel D∗± → D0π±s → (K−π+)π±s, where maticacceptancefortheD-mesonsof pT > 3.5GeVand the π± is the slow pion in the D∗± decay frame, pairs of |y| < 2.1) are found, as shown in in Fig. 4 (Bottom) for s oppositely-charged tracks with p > 1.0 GeV are com- the D∗± example. Within the large theoretical uncertain- T binedto form D0 candidates,withkaonandpionmasses ties,NLOQCDpredictionsareseentobeconsistentwith assumedinturnforeachtrackinordertocalculatethein- thedata,theuncertaintyonwhichisdominatedbythesta- variantmass. Any additionaltrack, with p > 0.25 GeV tisticalerror. T andachargeoppositetothatofthekaontrack,isassigned thepionmassandcombinedwiththeD0candidatetoform a D∗± candidate.A clear signalisseen inFig. 4(Top)in 3 Lifetime measurements thedistributionofthemassdifference∆M = M(Kππ )− s M(Kπ) at the nominal value of M(D∗±)− M(D0). From 3.1 B-hadronaveragelifetime afittothe∆M distribution,a D∗± yieldof2310±130is obtained,anditsmassfoundtobe145.41±0.03MeV,in PrecisemeasurementsofB-hadronlifetimesallowtestsof agreementwiththePDGworldaverage.Similarlyforthe theoreticalpredictionsfrom the Heavy Quark Expansion HadronColliderPhysicssymposium(HCP-2011) n 1 V3000 on fractio 00..89 ACCTMDLFSA Ss s ==s17=. 9T76e T VTe,eVV,|,yJ|/y|ψyJ|/J<ψ/ψ1|<|.<200.7.65 er 0.5 Me2500 ATDrwLigraoAhtnta-Sgc -h2ca0hPra1grre0ge eclo icmmombininbaiantairoytniosns s = 7 TeV Lint = 1.1 nb-1 ψ productimpt J/ 00000.....34567 A∫TLSL dpAti Sn~- a2l.i3g npmb-e1nt envelope Combinations p112050000000 fit : N(D*±) = 2310 ± 130 Non-pro 00..21 500 σ∆m Mod (=∆ 1M4)5 .=4 10 .±4 60 .±0 30 .M03e VMeV 0 0 0.14 0.145 0.15 0.155 0.16 0.165 0.17 1 10 pJ/ψ [GeV] ∆M = M(Kππs) - M(Kπ) [GeV] T eV] Non-prompt cross-section GeV]GeV] ATLASPreliminary s = 7 TeV Lint = 1.1 nb-1 dy [nb/G 101 FSAOpTiLNnA-LaSLli gB|yn→Jm/ψ e|J<n/0ψt .Xe7n5velope ±±µµb/) [D*b/) [D*110022 DPPOOatWWa HH20EE1GG0--PHYETRHWIAIG non-promptσ/dpT1100--21 σσ(/dpd(/dpdTT110011 MC@NLO 2d10-3 µ-) ATLAS µ→ψ+ 10-4 ∫sL= d 7t =T e2V.2 pb-1 1100--11 Br(J/10-5 10 pJ/ψ [GeV] 55 1100 1155 2200 2255 3300ppTT((DD33**±±55)) [[GGeeVV44]]00 T Fig. 4. (Top) The distribution of the mass difference, ∆M = V] M(Kππ )−M(Kπ),for D∗± candidates.Thedashedlinesshow promptσ2dy [nb/Ge/dpdT1110010--0-1321 PromSCNNApTpoLNitlOLLno cAO-u raCSro*l oi sEgClsonv|yo-aumsJlopr/eψe uoSc|n<rtrii tan0oS etg.ni7ionnle5nvgt elMelotopdeel tcstH2hheu.E1eecr.tvRNideToWisLnhsOteIsfrrGoiebbQrpauarnCDtneidsDd∗os±ennMscmthafCoolectwsr@huoelwntNahstrfiLieooatOnesngsrsate-ficoosfmhuufralanPDtrtcsOeg.t-deimWo(tnBechHsoeoooEmotfntrGobspemi-tTpniPc)rafYaootilDdrTouudnHinffcasIecteAadearren,ctwnPadotiimOintaththWplyieancHroesr|fyEood|tslGhits<doe-- µ-) POWHEG-PYTHIAcalculation. µ→+ 10-4 AsT=L 7A STeV ψBr(J/10-5 ∫L dt = 2.2 pb-1 Theinclusivelifetimemeasurementgivestheaverage lifetime of the admixture of B-hadrons produced at the 0 10 20 30 40 50 60 70 pJ/ψ [GeV] LHCanddecayingtofinalstatesincludinga J/ψ.Asdis- T cussed above, J/ψ mesons produced from the decays of B-hadronsarenon-prompt,havingadisplaceddecayver- Fig. 3. (Top) J/ψ non-prompt to inclusive fraction as a func- tex due to the B-hadronlifetime. The average B-lifetime tion of the J/ψ p compared to equivalent results from CMS T andCDF.(Middle)Non-promptJ/ψproductioncross-sectionas isthusextractedfromthedatabyperforminganunbinned a function of J/ψ p , compared to predictions from FONLL. maximumlikelihoodfitsimultaneouslytothe J/ψinvari- T (Bottom)Prompt J/ψproductioncross-sectionasafunctionof ant mass and the pseudo-proper decay time. In order to J/ψ p ,comparedtopredictionsfromNLOandNNLO∗ calcu- extract the real lifetime of the B-hadrons, which are not T lations,andtheColourEvaporationModel.Allplotsareinthe fully reconstructed, a correction for the smearing intro- exampleJ/ψrapiditybin|y|<0.75. ducedbytheuseofthepseudo-properdecaytimeinthefit isrequired.Thiscorrection(“F-factor”)isobtainedfrom Monte Carlo, with the J/ψ spectrumin B-hadrondecays re-weightedtomatchBaBardata.Theinvariantmassand pseudo-properdecay time projectionsof the fit, with the framework,whichcanpredictlifetimeratiosfordifferent respectivepulldistributions,areshowninFig.5.Theav- B-hadron species with per cent level accuracy. With the erageB-lifetimeismeasuredtobe: goalofpreparingtheway forprecisionmeasurementsof B-hadron lifetimes, an average lifetime measurement of hτ i=1.1489±0.016(stat.)±0.043(syst.)ps, (1) B inclusive B → J/ψX → µµX is made on the full 2010 dataset (35 pb−1) [6]. With orders of magnitude higher withthemainsystematicuncertaintyoriginatingfromthe statisticsthanforfullyreconstructedexclusive B-mesons uncertainty (in 2010) on the radial alignment of the ID. orB-baryoncandidates,theinclusivesampleenablesade- Thisresultisinagreementwiththemostrecentonefrom tailedinvestigationofthedecaylengthresolutionandthe the CDF collaborationand the expectedaveragelifetime impact of the residual misalignment of the tracking sys- computed using PDG lifetimes and production fractions tem. fromdifferentB-hadronspecies. EPJWebofConferences ing certain selections then fully reconstructthe B0 or B0 nts / [ 0.003 Gev ] 567800000000 7CB aoTcmekVbg irdnoaeutdan dfit component ATLLiAntS = 3P5r eplbim-1inary cpbmarinaonsnpdseei,ddriadnmteeaocsx.radiySmeitrniumctmoeelteτihxke=etrlBaiLhc-hoxtyaotmdhdreBfio/yntiptieosTlgdBfe,,utclhmlaeyanrsrwbseeciatohunnsdtsehtdlreiufiicenntdtveiamadnr,eiutahninnes-t e Ev 400 eachchannel. 300 ForB0thelifetimeisfoundtobe d 200 100 τ =1.51±0.04(stat.)±0.04(syst.)ps (2) B0 0 d 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 Invariant Mass [Gev] andforB0 s Pulls / [0.003 GeV ] ----02343211 whereaτmBa0si=ns1o.u4r1c±eo0f.0sy8s(tsetmata.)ti±cu0n.0c5er(tsayinstty.)cposm, esfro(3m) 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 thedetectoralignment.Withalimitednumberof B0 can- Invariant Mass [Gev] s didates (463 ± 26) the current measurement ignores the s ] 104 lifetimedifferenceofthemasseigenstates.However,within 3 p ATLAS Preliminary thecurrentprecisionthefittedvalueagreeswellwiththe 7 0.0 Lint = 35 pb-1 worldaverageoftheaveragelifetime(1.472±0.026ps). s / [ 103 7C oTmeVb idnaetda fit ent Signal component v E Background component 102 4 Summary TheATLASheavy-flavourphysicsprogrammehasmade 10 manyimportantmeasurementsofproductioncross-sections andmassesandlifetimesofvariousheavy-flavourstates. -2 0 2 4 6 8 10 Pseudo-proper Time [ps] Inseveralcasesthesearealreadychallengingcurrentthe- Pulls / [ 0.073 ps ] --20211 odwtireoaemnytiocafnaonlsrdtmrfrauoattirduoeerneldsoemacfteatatyhhsseeu.rLeTexHmhpeCeenraietbmsnielaeirnntgydtyatlsroeetaegprciecmhrhnfeeoi.sqrMmufeoosrtrhCepeoaPsvveeevrmsi,ottelhhaaee-- -2 0 2 4 6 8 10 surements has been particularly dependent on the excel- Pseudo-proper Time [ps] lent performanceof the ATLAS ID, MS and trigger sys- Fig.5. Invariantmass(Top)andpseudo-properdecaytime(Bot- tems. tom)projections(withtheirrespectivepulldistributions)ofthe simultaneous fit to these distributions in the B-hadron average lifetime measurement, showing the data and the signal, back- References groundandcombinedfitresults. 1. TheATLASCollaboration,JINST,3,(2008),S08003 3.2 B0 and B0 lifetimes 2. TheATLASCollaboration,arXiv:1109:0525[hep-ex], d s submittedtoPhys.Lett.B(2011) 3. The ATLAS Collaboration, Nucl. Phys. B850, 3, The lifetimes of B0 and B0 mesons are determined from d s (2011),387-444 their exclusive decay modes B0 → J/ψK∗0 and B0 → d s 4. The ATLAS Collaboration, Phys. Lett. B705, 1-2, J/ψφ,usingthe J/ψdecaytoadi-muonfinalstate,based (2011),9-27 on an integrated luminosityof 40 pb−1 [7]. The study of 5. The ATLAS Collaboration, ATLAS-CONF-2011-017 the B0 → J/ψφ decay is of special interest as it allows s (2011) themeasurementofthe B0 mixingphasewhichcangen- s 6. The ATLAS Collaboration, ATLAS-CONF-2011-145 erateCPviolationinthischannel.TheSMpredictionfor (2011) this CP violating phase is small meaning that any mea- 7. The ATLAS Collaboration, ATLAS-CONF-2011-092 suredexcesswouldbe a clear indicationofnew physics. (2011) Inadditionthelight(B )andheavy(B )masseigenstates L H have two distinct decay widths Γ and Γ which have L H beendeterminedattheTevatronusingatechniqueoftime- dependent angular analyses that allow the simultaneous extractionoftheCP-evenandCP-oddamplitudes.TheB0 d channel provides a valuable testing ground for measure- mentsoftheB0decayduetotheequivalenteventtopology s withadvantageofhigherstatistics. The K∗0 or φ candidates are reconstructed by select- ing all pairs of oppositely charged tracks not previously identified as muons, fitted to a common vertex with the twomuontracksfromtheJ/ψ.Quadrupletsoftrackspass-