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Upsilon Production at LHCb

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

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Upsilon Production at LHCb

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  1. 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, 19th April 2011

  2. Outline • Theory and motivation • The LHC and LHCb • Selected quarkonia results • ϒ cross section • Conclusions and outlook G.Manca, Quarkonia Workshop

  3. Introduction • Many quarkonia states discovered ~30 years ago • Nevertheless the production mechanism is not fully understood • Expected large cross-sections at LHC ->among first measurements • High rates make quarkonia central player for detector and software calibration Fermilab, Summer 1977 G.Manca, Quarkonia Workshop M=9.46 GeV/c2

  4. Motivations • The production mechanism in pp collisions still unclear • Several models around : • Started with Colorsinglet(CSM) • Undershoots the data, no polarisation prdiction • Extendend to color octet (COM) mechanisms • Better agreement for cross-section, predicts TRANSVERSE polarisation, not confirmed by experiments • NLO CSM describes cross-section and allows LONGITUDINAL polarisation • Other 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 issue pT(GeV/c) J/y & ϒ cross section crucial milestone in understanding detector and first step to B cross section measurement G.Manca, Quarkonia Workshop

  5. Polarisation measurement • In the Υ(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 predictions • For J/psi and Psi(2s) the NRQCD and the data disagree. G.Manca, Quarkonia Workshop

  6. CERN and the LHC • pp collider : 2010 : • @ √s = 7 TeV • L ≈ 1-2·1031 cm-2 s-1 p p NOMINAL (2011) : √s =14 TeV L = 2·1032 cm-2 s-1 (LHCb specific) G.Manca, Quarkonia Workshop

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

  8. The LHCb detector h=2 Muon System RICH Detectors Vertex Locator VELO field regularly reversed to cancel detector asymmetries h=5 p p pp collision Point Tracking System Calorimeters • Performance numbers relevant to quarkonium analyses: • Charged tracks Dp/p = 0.35 % - 0.55%, s(m)=10-25 MeV/c2 • ECAL s(E)/E= 10% (E/GeV)-1/2 1 % • Muon ID: e(mm) = 97%, mis-ID rate (pm) = 1-3 % • Vertexing: proper time resolution 30-50 fs • Trigger: dominantly software G.Manca, Quarkonia Workshop

  9. Rapidity Range G.Manca, Quarkonia Workshop

  10. ϒ→mm Acceptance Total Acceptance≈20% CMS 85% CMS LHCb Total Acceptance≈3-14% ATLAS Acceptance 85% ATLAS CMS ALICE ATLAS Total Acceptance≈8% LHCb Acceptance 86% LHCb G.Manca, Quarkonia Workshop

  11. ϒ production G.Manca, Quarkonia Workshop

  12. Three for the price of one! BR(Y(1S))=(2.48±0.05)% BR(Y(2S))=(1.93±0.17)% BR(Y(3S))=(2.18±0.21)% G.Manca, Quarkonia Workshop

  13. Trigger and Event Selection pT>1.4 GeV/c Single Muon: L0 Trigger: Di-Muon: pT,1>0.56 GeV/c, pT,2>0.48 GeV/c Confirm L0 single Muon and pT>1.8 GeV/c (Prescaled) Single Muon: HLT1 Trigger: Confirm L0 Di-Muon and Mμμ>2.5 GeV/c2 Di-Muon: Mμμ>2.9 GeV/c2 or cuts on vertex and track quality Di-Muon: HLT2 Trigger: Global Event Cuts (GEC): reject events with very large multiplicities (93% efficiency) μ tracks: ● well reconstructed tracks identified as muons in muon detector, ● pT > 1 GeV/c, ● Track fit quality Reconstructed U: ● mass window: 8.5-11.5 GeV/c2, ● vertex fit quality (p(χ2)>0.5%).

  14. Cross Section Measurement Strategy For a generic resonance A: • Nfit = number of events in the mass peak in each pT bin, corrected for acceptance and efficiency • εtot = total efficiency • ∆pt, ∆y = bins of pT and y • ∫Ldt = integrated luminosity G.Manca, Quarkonia Workshop

  15. a) Number of ϒ(1S) candidates • 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 individual bin fits G.Manca, Quarkonia Workshop

  16. 0<pT<1 1<pT<2 2<pT<3 a) Number of ϒ (1S) candidates • Nfit : extracted from Crystal Ball (CB) part of the fit with CB+ exponential. • Fix width and masses • Only ϒ(1s) considered. • 2.0 < y < 2.5 3<pT<4 4<pT<5 5<pT<6 6<pT<7 7<pT<8 8<pT<9 10<pT<11 11<pT<12 9<pT<10 12<pT<13 13<pT<14 14<pT<15 G.Manca, Quarkonia Workshop

  17. a) Number of ϒ(1S) candidates G.Manca, Quarkonia Workshop

  18. Efficiency The efficiency εtot has been broken in three pieces : εtot = Nϒ(accepted, reconstructed and triggered)/Nϒgenerated Nϒaccepted Nϒreconstructed Nϒtriggered = Nϒgenerated Nϒaccepted Nϒreconstructed -Nϒgenerated = Total number of ϒ’s generated in the pT-y chosen range -Nϒaccepted = Number of ϒ’s generated inside the LHCb angular acceptance (10-400 mrad), in the pT-y chosen range -Nϒreconstructed=Number of ϒ’s accepted, detected and reconstructed in range -Nϒtriggered =Number of ϒ’s accepted, detected, reconstructed in range and triggered from Monte Carlo from Data and MC b) A c) εreco d)εtrig G.Manca, Quarkonia Workshop

  19. b) Acceptance Nevts gen with  in 0<pT<15,2.0<y<4.5,10<<400mrad A=acceptance of the LHCb geometry cut= Nevts generated with in 0<pT<15,2.0<y<4.5 A pT of Y (GeV/c) y of Y G.Manca, Quarkonia Workshop

  20. c) Reconstruction Efficiency N ϒ’s detected,reconstructed in range Εrec= efficiency for ϒ’s to be detected, reconstructed and matched to MC N ϒ’s generated in angular acceptance in range = pT of Y (GeV/c) y of Y G.Manca, Quarkonia Workshop

  21. d) Trigger Efficiency Trigger efficiency: efficiency of the triggers used to select the events • L0 • HLT1 • HLT2 • Calculated in J/y events as a function of (pTm1+pTm2) and <y>, for independent triggers, then weighed with Lum • Since 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 ϒ Monte Carlo->later • Applied as a weight to the candidate entering the M(mm) plot N ϒ’s detected,reconstructed,triggered in range εtrig= efficiency ϒ’s to be triggered N ϒ’s detected,reconstructed, in range = G.Manca, A&S Week

  22. d) Trigger Efficiency y of Y • Scaled number of candidates to get effect as a function of ϒ pT and y pT of Y (GeV/c) pT of Y (GeV/c) y of Y G.Manca, Quarkonia Workshop

  23. Scaled number of ϒ(1S) candidates • 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

  24. Systematic Uncertainties G.Manca, Quarkonia Workshop

  25. Polarisation effect on A y of Y Calculated reweighting the MC unpolarised events assuming a=±1 pT of Y (GeV/c) pT of Y (GeV/c) pT of Y (GeV/c) a=+1 a= -1 a= 0 α = (σT −2σL)/(σT +2σL) With σT /L cross sections for production of transverse and longitudinal polarised α = −1 ->full longitudinal polarisation α = +1 -> full transverse polarization, α = 0 -> no polarisation pT of Y (GeV/c) G.Manca, Quarkonia Workshop y of Y

  26. Polarisation effect on ereco • Calculated reweighting the MC unpolarised events assuming a=±1 y of Y pT of Y (GeV/c) α = −1 ->full longitudinal polarisation α = +1 -> full transverse polarization, α = 0 -> no polarisation α = (σT −2σL)/(σT +2σL) With σT /L cross sections for production of transverse and longitudinal polarised G.Manca, Quarkonia Workshop

  27. Upsilon Cross Section

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

  29. Comparison with CMS G.Manca, Quarkonia Workshop

  30. Conclusions • ϒ(1S) cross section measured. ϒ(2S) and ϒ(3S) are under way • Agreement with theory good! • Trigger efficiency and polarisation uncertainty can be improved • ϒ polarisation next step • Should be ready for the summer  G.Manca, Quarkonia Workshop

  31. Back up G.Manca, Quarkonia Workshop

  32. ϒ cross section G.Bodwin, talk at Berkeley workshop May 2009 ϒ rate ~ 1/100 J/ψ rate LHC rate ~ 50 Tevatron rate Caveats: These plots only include the color-singlet contributions lower limit Branching ratios not included Our energies lower than 5 GeV more events Rapidity range different (but flat y) 10 TeV! G.Manca, Quarkonia Workshop

  33. The LHCb Trigger Level 0: Hardware triggers From Muon system & calorimeters High Level Trigger (HLT) 1: Software triggers Add information from VELO and tracking stations to Level 0 information Find primary vertices, etc. HLT2: Software triggers Use all of the detector information to make inclusive and exclusive selections

  34. Trigger and Event Selection G.Manca, Quarkonia Workshop

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

  36. 0<pT<1 1<pT<2 2<pT<3 a) Number of ϒ (1S) candidates • Nfit : extracted from Crystal Ball (CB) part of the fit with CB+ exponential. • Fix width and masses • Only ϒ(1s) considered. • 2.0 < y < 2.5 3<pT<4 4<pT<5 5<pT<6 6<pT<7 7<pT<8 8<pT<9 10<pT<11 11<pT<12 9<pT<10 12<pT<13 13<pT<14 14<pT<15 G.Manca, A&S Week

  37. 0<pT<1 1<pT<2 2<pT<3 a) Number of ϒ (1S) candidates • Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. • Fix width,m2S,m3S to 50 MeV. • Only ϒ(1s) considered. • 2.5 < y < 3.0 3<pT<4 4<pT<5 5<pT<6 6<pT<7 7<pT<8 8<pT<9 10<pT<11 11<pT<12 9<pT<10 12<pT<13 13<pT<14 14<pT<15 G.Manca, A&S Week

  38. 0<pT<1 1<pT<2 2<pT<3 a) Number of ϒ (1S) candidates • Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. • Fix width,m2S,m3S to 50 MeV. • Only ϒ(1s) considered. • 3.0 < y < 3.5 3<pT<4 4<pT<5 5<pT<6 6<pT<7 7<pT<8 8<pT<9 10<pT<11 11<pT<12 9<pT<10 12<pT<13 13<pT<14 14<pT<15 G.Manca, A&S Week

  39. 0<pT<1 1<pT<2 2<pT<3 a) Number of ϒ (1S) candidates • Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. • Fix width,m2S,m3S to 50 MeV. • Only ϒ(1s) considered. • 3.5 < y < 4.0 3<pT<4 4<pT<5 5<pT<6 6<pT<7 7<pT<8 8<pT<9 10<pT<11 11<pT<12 9<pT<10 12<pT<13 13<pT<14 14<pT<15 G.Manca, A&S Week

  40. 0<pT<1 1<pT<2 2<pT<3 a) Number of ϒ (1S) candidates • Nfit : extracted from Crystal Ball (CB) part of the fit with CB+exponential. • Fix width,m2S,m3S to 50 MeV. • Only ϒ(1s) considered. • 4.0 < y < 4.5 3<pT<4 4<pT<5 5<pT<6 6<pT<7 7<pT<8 8<pT<9 10<pT<11 11<pT<12 9<pT<10 12<pT<13 13<pT<14 14<pT<15 G.Manca, A&S Week

  41. Choice of Fit function CB+exponential (default) G.Manca, A&S Week

  42. Choice of Fit function CB+polynomial G.Manca, A&S Week

  43. Y : Pt rec vs. Pt gen 12.1.2011 G.Manca, A&S Week Giulia Manca, FWG Meeting

  44. Towards 2S… G.Manca, A&S Week

  45. ..and the 3S G.Manca, A&S Week

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