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:paul.bell@cern.ch 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

Heavy flavour results from ATLAS

Similar Heavy flavour results from ATLAS