Upsilon Production at LHCb

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LHCb-CONF-2011-016. Giulia Manca, Universita` degli Studi di Cagliari & I.N.F.N. on behalf of the LHCb collaboration. Upsilon Production at LHCb. Quarkonia Workshop, Vienna, 19 th April 2011. Outline. Theory and motivation The LHC and LHCb Selected quarkonia results ϒ cross section - PowerPoint PPT Presentation

Transcript of Upsilon Production at LHCb

  • Upsilon Production at LHCbQuarkonia Workshop, Vienna, 19th April 2011Giulia Manca, Universita` degli Studi di Cagliari & I.N.F.N.on behalf of the LHCb collaborationLHCb-CONF-2011-016

    G.Manca, Quarkonia Workshop

  • OutlineTheory and motivationThe LHC and LHCbSelected quarkonia results cross sectionConclusions and outlook

    19.4.2011G.Manca, Quarkonia Workshop*

    G.Manca, Quarkonia Workshop

  • IntroductionMany quarkonia states discovered ~30 years agoNevertheless theproduction mechanism is not fully understoodExpected large cross-sections at LHC ->among first measurements High rates make quarkonia central player for detector and software calibration

    19.4.2011G.Manca, Quarkonia Workshop*M=9.46 GeV/c2Fermilab, Summer 1977

    G.Manca, Quarkonia Workshop

  • MotivationsThe production mechanism in pp collisions still unclearSeveral models around :Started with Color singlet(CSM) Undershoots the data, no polarisation prdictionExtendend to color octet (COM) mechanismsBetter agreement for cross-section, predicts TRANSVERSE polarisation, not confirmed by experimentsNLO CSM describes cross-section and allows LONGITUDINAL polarisationOther models such as color evaporation model (CEM), kt factorization, soft color interaction model cannot describe the data or make predictions New data from LHC experiments will help to resolve this issue19.4.2011G.Manca, Quarkonia Workshop*J/y & cross section crucial milestone in understanding detector and first step to B cross section measurementpT(GeV/c)

    G.Manca, Quarkonia Workshop

  • Polarisation measurement19.4.2011G.Manca, Quarkonia Workshop* In the (1S) case, the D0 results (black) are incompatible with the CDF results (green) The CDF results are compatible with the NRQCD predictions (yellow) The D0 results are marginally incompatible with NRQCD predictions The curves are the limiting case of the kT factorization predictionsFor J/psi and Psi(2s) the NRQCD and the data disagree.

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  • CERN and the LHC19.4.2011*G.Manca, Quarkonia WorkshopppNOMINAL (2011) : s =14 TeVL = 21032 cm-2 s-1 (LHCb specific) pp collider : 2010 :@ s = 7 TeVL 1-21031 cm-2 s-1

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  • Luminosity @ LHCb 19.4.2011*G.Manca, Quarkonia WorkshopMar 2010 July 2010 Nov 2010 LHC running very well!LHCb efficiency 90%This analysis : L 35 pb-1 (10%)Goal : 1 fb-1 (end of 2011)

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  • The LHCb detectorpp collision PointVertex Locator VELOTracking SystemMuonSystemRICH DetectorsCalorimeterspp*19.4.2011G.Manca, Quarkonia WorkshopPerformance numbers relevant to quarkonium analyses:Charged tracks Dp/p = 0.35 % - 0.55%, s(m)=10-25 MeV/c2ECAL s(E)/E= 10% (E/GeV)-1/2 1 % Muon ID: e(mm) = 97%, mis-ID rate (pm) = 1-3 % Vertexing: proper time resolution 30-50 fsTrigger: dominantly software

    field regularly reversed to cancel detector asymmetriesh=2h=5

    G.Manca, Quarkonia Workshop

  • Rapidity Range19.4.2011G.Manca, Quarkonia Workshop*

    G.Manca, Quarkonia Workshop

  • mm Acceptance19.4.2011G.Manca, Quarkonia Workshop*LHCbCMSATLASCMSATLASLHCbALICETotal Acceptance3-14%ATLAS Acceptance 85% Total Acceptance20%CMS 85% Total Acceptance8%LHCb Acceptance 86%

    G.Manca, Quarkonia Workshop

  • production19.4.2011G.Manca, Quarkonia Workshop*

    G.Manca, Quarkonia Workshop

  • Three for the price of one! 19.4.2011G.Manca, Quarkonia WorkshopBR(Y(1S))=(2.480.05)%BR(Y(2S))=(1.930.17)%BR(Y(3S))=(2.180.21)%*

    G.Manca, Quarkonia Workshop

  • Trigger and Event Selection*L0 Trigger:Single Muon:Di-Muon:pT>1.4 GeV/c pT,1>0.56 GeV/c, pT,2>0.48 GeV/c HLT1 Trigger:Single Muon:Di-Muon:Confirm L0 single Muon and pT>1.8 GeV/c (Prescaled)M>2.9 GeV/c2 or cuts on vertex and track quality HLT2 Trigger: tracks: well reconstructed tracks identified as muons in muon detector, pT > 1 GeV/c, Track fit qualityReconstructed U: mass window: 8.5-11.5 GeV/c2, vertex fit quality (p(2)>0.5%).Global Event Cuts (GEC): reject events with very large multiplicities (93% efficiency)Confirm L0 Di-Muon and M>2.5 GeV/c2Di-Muon:

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  • Cross Section Measurement StrategyFor a generic resonance A:

    Nfit = number of events in the mass peak in each pT bin, corrected for acceptance and efficiency tot = total efficiency pt, y = bins of pT and yLdt = integrated luminosity

    19.4.2011G.Manca, Quarkonia Workshop*

    G.Manca, Quarkonia Workshop

  • a) Number of (1S) candidates19.4.2011G.Manca, Quarkonia Workshop Nfit : function=3 Crystal Balls(CB)+exponential for background. Fixed (a=2,n=1) and width (2S,3S) to scale with the masses. *Same function used on individualbin fits

    G.Manca, Quarkonia Workshop

  • 19.4.2011G.Manca, Quarkonia Workshopa) Number of (1S) candidates Nfit : extracted from Crystal Ball (CB) part of the fit with CB+ exponential. Fix width and masses Only (1s) considered.

    2.0 < y < 2.50

  • 19.4.2011G.Manca, Quarkonia Workshopa) Number of (1S) candidates*

    G.Manca, Quarkonia Workshop

  • 19.4.2011G.Manca, Quarkonia WorkshopEfficiencyThe efficiency tot has been broken in three pieces :tot = N(accepted, reconstructed and triggered)/N generated

    Naccepted Nreconstructed Ntriggered = Ngenerated Naccepted Nreconstructed

    -Ngenerated = Total number of s generated in the pT-y chosen range-Naccepted = Number of s generated inside the LHCb angular acceptance (10-400 mrad), in the pT-y chosen range-Nreconstructed=Number of s accepted, detected and reconstructed in range -Ntriggered =Number of s accepted, detected, reconstructed in range and triggered b) A c) reco d)trigfrom Monte Carlofrom Data and MC*

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  • 19.4.2011G.Manca, Quarkonia Workshopb) Acceptance Nevts gen with in 0
  • 19.4.2011G.Manca, Quarkonia Workshopc) Reconstruction Efficiency N s detected,reconstructed in range rec = efficiency for s to be detected, reconstructed and matched to MC N s generated in angular acceptance in range

    =*pT of Y (GeV/c)y of Y

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  • 25.2.2011G.Manca, A&S Weekd) Trigger EfficiencyTrigger efficiency: efficiency of the triggers used to select the events L0 HLT1HLT2

    Calculated in J/y events as a function of (pTm1+pTm2) and , for independent triggers, then weighed with LumSince some triggers were prescaled for a portion of the data, an average value is used, weighted by the corresponding luminosity. Several cross checks have been performed to make sure this was correctly handled.

    Systematic uncertainty estimated using J/y and Monte Carlo->later

    Applied as a weight to the candidate entering the M(mm) plot

    N s detected,reconstructed,triggered in rangetrig= efficiency s to be triggered N s detected,reconstructed, in range

    =*

    G.Manca, Quarkonia Workshop

  • d) Trigger Efficiency19.4.2011G.Manca, Quarkonia Workshop*Scaled number of candidates to get effect as a function of pT and ypT of Y (GeV/c)y of Yy of YpT of Y (GeV/c)

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  • Scaled number of (1S) candidates19.4.2011G.Manca, Quarkonia Workshop Nfit : function=3 Crystal Balls(CB)+exponential for background. Fixed (a=2,n=1) and width (2S,3S) to scale with the masses. *Scaled for the trigger efficiency

    G.Manca, Quarkonia Workshop

  • 19.4.2011G.Manca, Quarkonia WorkshopSystematic Uncertainties*

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  • 19.4.2011G.Manca, Quarkonia WorkshopPolarisation effect on ACalculated reweighting the MC unpolarised events assuming a=1a= 0a= -1a=+1* = 1 ->full longitudinal polarisation = +1 -> full transversepolarization, = 0 -> no polarisation = (T 2L)/(T +2L)With T /L cross sections for production of transverse and longitudinal polarisedpT of Y (GeV/c)pT of Y (GeV/c)pT of Y (GeV/c)pT of Y (GeV/c)y of Yy of Y

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  • 19.4.2011G.Manca, Quarkonia WorkshopPolarisation effect on erecoCalculated reweighting the MC unpolarised events assuming a=1* = 1 ->full longitudinal polarisation = +1 -> full transversepolarization, = 0 -> no polarisation = (T 2L)/(T +2L)With T /L cross sections for production of transverse and longitudinal polarisedy of YpT of Y (GeV/c)

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  • Upsilon Cross Section

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  • Comparison with Theory19.4.2011G.Manca, Quarkonia Workshop*Y. Q. Ma, K. Wang and K. T. Chao, Phys. Rev. Lett. 106 (2011) 042002.P. Artoisenet, PoS ICHEP 2010 (2010) 192.J.-P. Lansberg, Eur. Phys. J. C 61 (2009) 693A. D. Frawley, T. Ullrich and R. Vogt, Phys. Rep. 462 (2008) 125.

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  • Comparison with CMS19.4.2011G.Manca, Quarkonia Workshop*

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  • Conclusions(1S) cross section measured. (2S) and (3S) are under wayAgreement with theory good!Trigger efficiency and polarisation uncertainty can be improved polarisation next stepShould be ready for the summer 19.4.2011G.Manca, Quarkonia Workshop*

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  • Back up19.4.2011G.Manca, Quarkonia Workshop*

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  • cross section 19.4.2011G.Manca, Quarkonia Workshop*G.Bodwin, talk at Berkeley workshop May 2009 rate ~ 1/100 J/ rateLHC rate ~ 50 Tevatron rateCaveats:These plots only include the color-singlet contributions lower limitBranching ratios not includedOur energies lower than 5 GeV more eventsRapidity range different (but flat y)10 TeV!

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  • *Level 0: Hardware triggers From Muon system & calorimetersHigh Level Trigger (HLT) 1: Software triggersAdd information from VELO and tracking stations to Level 0 informationFind primary vertices, etc.HLT2: Software triggersUse all of the detector information to makeinclusive and exclusive selections

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  • Trigger and Event Selection19.4.2011G.Manca, Quarkonia Workshop*

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  • Trigger Efficiency25.2.2011G.Manca, A&S Week* Systematics: difference between e(trig) measured in J/y MC events and the true value in MC Caveat: this is the per bin effect, the effect on the cross section is 6-16%

    G.Manca, Quarkonia Workshop

  • 25.2.2011G.Manca, A&S Weeka) Number of (1S) candidates Nfit : extracted from Crystal Ball (CB) part of the fit with CB+ exponential. Fix width and masses Only (1s) considered.

    2.0 < y < 2.50

  • 25.2.2011G.Manca, A&S Weeka) Number of (1S) candidates Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. Fix width,m2S,m3S to 50 MeV. Only (1s) considered.

    2.5 < y < 3.00

  • 25.2.2011G.Manca, A&S Weeka) Number of (1S) candidates Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. Fix width,m2S,m3S to 50 MeV. Only (1s) considered.

    3.0 < y < 3.50

  • 25.2.2011G.Manca, A&S Weeka) Number of (1S) candidates Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. Fix width,m2S,m3S to 50 MeV. Only (1s) considered.

    3.5 < y < 4.00

  • 25.2.2011G.Manca, A&S Weeka) Number of (1S) candidates Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. Fix width,m2S,m3S to 50 MeV. Only (1s) considered.

    4.0 < y < 4.50

  • 25.2.2011G.Manca, A&S WeekChoice of Fit functionCB+exponential (default)*

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  • 25.2.2011G.Manca, A&S WeekChoice of Fit functionCB+polynomial*

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  • 25.2.2011G.Manca, A&S WeekY : Pt rec vs. Pt gen12.1.2011Giulia Manca, FWG Meeting*

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  • Towards 2S25.2.2011G.Manca, A&S Week*

    G.Manca, Quarkonia Workshop

  • ..and the 3S25.2.2011G.Manca, A&S Week*

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    ****Check where these numbers are coming from and how are they obtained **Put the Jpsi event display from Thomas for this slide.

    **