Ï and Î¥ production measurements at LHCb - Physics at LHCb
Ï and Î¥ production measurements at LHCb - Physics at LHCb
Ï and Î¥ production measurements at LHCb - Physics at LHCb
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ψ <strong>and</strong> Υ <strong>production</strong> <strong>measurements</strong><strong>at</strong> <strong>LHCb</strong>Giovanni Sab<strong>at</strong>ino for the <strong>LHCb</strong> collabor<strong>at</strong>ionUniversità degli studi di Roma “Tor Verg<strong>at</strong>a”<strong>and</strong> INFN28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 1
Outline• Prompt J/ψ <strong>and</strong> J/ψ from b cross-sectionmeasurement• Y cross-section measurement• Work in progress (coming soon)• prompt J/ψ polaris<strong>at</strong>ion• ψ(2S) <strong>production</strong> cross-section• Plans for future28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 2
J/ψ cross-section• Double differential cross-section, as a function of p T <strong>and</strong> y:– 14 p T bins, p T < 14 GeV/c– 5 y bins, 2
J/ψ: trigger <strong>and</strong> selectionL0 TriggerSingle Muon: p T >1.4 GeV/cDi-Muon: p T,1 >0.56 GeV/c, p T,2 >0.48 GeV/cHLT1 TriggerSingle Muon:Di-Muon:confirms L0 Single Muon <strong>and</strong> p T >1.8 GeV/c(Pre-scaled by 0.2 in 3 pb -1 of d<strong>at</strong>a)confirms L0 Di-Muon <strong>and</strong> M μμ >2.5 GeV/c 2HLT2 Trigger Unbiased Di-Muon: M μμ >2.9 GeV/c 2Offline selectionμ tracks:• long tracks identified as muons in themuon detector• muon p T > 0.7 GeV/c• track fit quality (χ 2 /nDoF < 4)Reconstructed J/y:• mass window: 0.15 GeV/c 2• vertex fit quality (p(χ 2 )>0.5%)• nPV≥128/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 4
J/ψ: mass distributions<strong>LHCb</strong> Preliminary√s = 7 TeV5.2 pb -1 d<strong>at</strong>aN = 564603 ± 924Each mass distribution in the (p T ,y)bin is fitted with:• a Crystal Ball function for the signal• an exponential function for the background28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 5
Separ<strong>at</strong>ion prompt/non-prompt J/ψPrompt J/ψTailJ/ψ from b<strong>LHCb</strong> Preliminary√s = 7 TeV5.2 pb -1 d<strong>at</strong>aTail:• signal J/ψ associ<strong>at</strong>ed witha wrong primary vertex• shape determined directlyfrom real d<strong>at</strong>a simul<strong>at</strong>ingan uncorrel<strong>at</strong>ed PV (nextevent)28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 6
Separ<strong>at</strong>ion prompt/non-prompt J/ψ• Signal:• Convolved by resolution function: sum of 2 Gaussians• Background: fit with function describing the shape seen in the J/ψmass sideb<strong>and</strong>s: 3 positive exponentials <strong>and</strong> 2 neg<strong>at</strong>iveexponentialsσ tz : 53 fs28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 7
J/ψ cross-sectionN: number of reconstructed signal J/ψ (separ<strong>at</strong>ely prompt <strong>and</strong> from b)L: integr<strong>at</strong>ed luminosity = (5.2±0.5) pb -1ε tot : total efficiencyB: (5.94 ± 0.06) %Δy = 0.5, Δ p T =1 GeV/c: bin sizes28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 8
J/ψ: efficiencies<strong>LHCb</strong> Simul<strong>at</strong>ion• Efficiencies are computed from MC <strong>and</strong> have been checked on d<strong>at</strong>a withcontrol samples• prompt <strong>and</strong> from b J/ψ show the same efficiency in each bin28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 9
Î tot (J/y)Î tot (J/y)Î tot (J/y)J/ψ: polaris<strong>at</strong>ion scenariosJ/ψ polaris<strong>at</strong>ion (unknown for the moment) affects the muon distributionThree extreme polaris<strong>at</strong>ion scenarios have been simul<strong>at</strong>ed (l q =+1, l q =-1,l q =0 which correspond to transverse, longitudinal <strong>and</strong> no polaris<strong>at</strong>ion inthe Helicity frame) three Xsec results are given10.90.80.70.60.50.40.30.20.14.0 < y < 4.53.5 < y < 4.03.0 < y < 3.52.5 < y < 3.02.0 < y < 2.500 5 10 15(GeV/c)pT10.90.80.70.60.50.40.30.20.14.0 < y < 4.53.5 < y < 4.03.0 < y < 3.52.5 < y < 3.02.0 < y < 2.500 5 10 15(GeV/c)pT10.90.80.70.60.50.40.30.20.14.0 < y < 4.53.5 < y < 4.03.0 < y < 3.52.5 < y < 3.02.0 < y < 2.500 5 10 15(GeV/c)l q =+1 l q =0 l q =-1pT28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 10
J/ψ: system<strong>at</strong>ic errors• Many system<strong>at</strong>ic sources studied, moslty comparingd<strong>at</strong>a with simul<strong>at</strong>ion• In general small differences (some %) found between d<strong>at</strong>a<strong>and</strong> MC: scale factors to compens<strong>at</strong>e• The most important:• Tracking efficiency: 8% syst. error• Luminosity uncertainty: 10%• Bin size: 0.1 to 15 % (bin dependent, important close to theedges of the fiducial region)28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 11
J/ψ cross-section: resultsunpolarised J/ψ hypothesis28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 12
Prompt J/ψ: comparison with theoryP. Artoisenet[PoS ICHEP 2010(2010) 192]M. Butenschön<strong>and</strong>B. Kniehl[Phys. Rev. Lett. 106 (2011)022301, arXiv:1009.5662 [hep-ph]]J.-P. Lansberg[Eur. Phys.J. C 61 (2009) 693,arXiv:0811.4005[hep-ph]]K. T. Chao et al.[Phys. Rev. Lett. 106 (2011)042002, arXiv:1009.3655 [hep-ph]]R. Vogt[Phys. Rep. 462 (2008) 125,arXiv:0806.1013 [nucl-ex]]28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 13
J/ψ from b: comparison with theoryM. Cacciari, M. Greco, P. Nason,J. High Energy Phys. 9805 (1998)007 hep-ph/9803400M. Cacciari, S. Frixione, P. Nason,J. High Energy Phys. 0103 (2001)006 hep-ph/010213428/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 14
Y cross-sectionY(nS) produced in pp collisions can be• prompt-direct if the resonance arises directly from the b-bbar• prompt-indirect when it comes from higher st<strong>at</strong>es feeddown:χ b Y(nS) γ, Y(n’S) Y(nS) + X• Measurement of the Y cross-section: same str<strong>at</strong>egyalready discussed for J/ψ• D<strong>at</strong>a sample: 32.4 pb -1• Selection similar to the J/ψ one: 2 muons, IsMuon, p T >1 GeV/c,track fit χ 2 /nDoF < 4, vertex fit p(χ 2 )>0.01%28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 15
Y mass fitThree CB plus exponential for background. Fixed 2S, 3S masses <strong>and</strong> widths.Only Y(1S) considered for cross-section measurement28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 16
Y mass fit in (p T ,y) bin2
Y cross-section: results• Efficiencies computed from Monte Carlo• Polaris<strong>at</strong>ion effect studied in the same way as done for the J/ψ cross-section30 .9(1S), p 15 GeV/ c,2 y 4.5 108 .3 0.7(st<strong>at</strong>) (syst) nbT 25 .828/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 18
Y cross-section: comparison with theory28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 19
Y cross-section: comparison with CMS28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 20
Measurements in progress: J/ψ polaris<strong>at</strong>ion• Theories give clear predictions of prompt J/ψ polaris<strong>at</strong>ion: thismeasurement is an important test• Polaris<strong>at</strong>ion knowledge helps to decrease the error on the crosssectionsmeasured• Delic<strong>at</strong>e point: to correct thedistributions for the detector effect• Coming soon: polaris<strong>at</strong>ionmeasurement (λ θ , λ θφ , λ φ ) in thehelicity frame, in 15 p T bins,0
Measurements in progress: J/ψ polaris<strong>at</strong>ionThe st<strong>at</strong>istical sensitivity of the λ parametersdepends on the p T bin st<strong>at</strong>isticsParameter min maxλ θ 0.01 0.16λ θφ 0.006 0.06λ φ 0.004 0.0628/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 22
Measurements in progress: ψ(2S) <strong>and</strong> χ c crosssections• Coming soon: ψ(2S) cross-section inbins (p T ,y)– 0
Plans for future• Y(2S), Y(3S) cross-section <strong>measurements</strong> are underway• To extend J/ψ polaris<strong>at</strong>ion measurement (available soon inthe Helicity frame) to other reference frames (CS-GJ)• Measurement of the ψ(2S) <strong>and</strong> Y polaris<strong>at</strong>ion are possiblealso• It is interesting to underst<strong>and</strong> whether different phase-spaceranges should be probed• 0
Conclusions• J/ψ (prompt <strong>and</strong> from b) <strong>and</strong> Y cross-section<strong>measurements</strong> have been presented– Both are in good agreement with theory predictions• ψ(2S) cross-section <strong>and</strong> J/ψ polaris<strong>at</strong>ion– Results are expected to be approved very soon• Other possible <strong>measurements</strong> in the near future: Y(nS),ψ, polaris<strong>at</strong>ion28/04/2011 Bad Honnef <strong>Physics</strong> <strong>at</strong> <strong>LHCb</strong> 25
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