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LHCb early results and prospects: final states including leptons

LHCb early results and prospects: final states including leptons. Liming Zhang (Syracuse University). Brookhaven Forum 2010 May 26-28. on behalf of the LHCb Collaboration. LHCb Physics Program. LHCb focus on searching for New Physics in the flavour sector

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LHCb early results and prospects: final states including leptons

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  1. LHCb early results and prospects: final states including leptons Liming Zhang (Syracuse University) Brookhaven Forum 2010May 26-28 on behalf of the LHCb Collaboration

  2. LHCb Physics Program • LHCb focus on searching for New Physics in the flavour sector • Complementary to direct search in ATLAS and CMS • Some key LHCb measurements • CP ViolationBs mixing phase fs, BDK : γ from loops and trees, Bhh • Rare DecaysBR(Bs μ+μ-), B K* For more details see the LHCb Roadmap document http://arxiv.org/abs/0912.4179 Brookhaven Forum 2010

  3. The LHCb Experiment Pythia production cross section (14TeV) 100 mb 230 mb • LHCb is a dedicated B physics experiment at LHC • High beauty cross section expected: 200-500 mb @ 7-14 TeV • Access to all b-hadrons: B+, B0, Bs, Bc, b-baryons • Luminosity limited to ~ 2x1032 to limit multiple interactions per bunch crossing • Expect to reach this in 2010 • Expect ~ 2fb-1 and ~1012 bb pairs per nominal year @ 14 TeV (107 secs) • ~200 pb-1 in 2010 and 1fb-1 in 2011 @ 7 TeV • LHCb acceptance optimised for forward bb production: Forward single arm spectrometer 1.9<<4.9 • b-hadrons produced at low angle • Correlated bb-production in same hemisphere pT h Production  of B vs B q B (rad) Brookhaven Forum 2010 q B (rad)

  4. LHCb Detector RICH: PID: primarily K, separation VELO: primary vertex impact parameter displaced vertex Muon System Interaction region Calorimeters: PID: h,e,, 0 Tracking Station: p for lower energy tracks and long lived V0reconstruction Tracking Stations: p of charged particles that traverse the magnet Brookhaven Forum 2010

  5. Detector Workings LHCb detector ~ fully installed and commissioned  walk through the detector using the example of a Bs→DsK decay Brookhaven Forum 2010

  6. B-VertexMeasurement 144 mm 47 mm K K Bs K Ds  d~1cm 440 mm Example: Bs → Ds K (MC simulation) s(t) ~40 fs f sensors R sensors Primary vertex Decay time resolution = 40 fs Vertex Locator (Velo) Silicon strip detector with ~ 5 mm hit resolution  30 mm IP resolution at pT~2GeV Vertexing: • trigger on impact parameter • measurement of decay distance (time) Brookhaven Forum 2010

  7. Momentum and Mass measurement p+, K Bs K K Ds  Primary vertex btag Momentum meas. + direction (VELO): Mass resolution for background suppression Mass resolution s ~14 MeV Bs→ Ds K Bs →Ds p (MC)  Brookhaven Forum 2010

  8. Hadron Identification RICH: K/p identification using Cherenkov light emission angle RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014 RICH2: 100 m3 CF4 n=1.0005 Brookhaven Forum 2010

  9. Particle identification and L0 trigger K Bs K Ds K  btag Primary vertex e h ECAL (inner modules): σ(E)/E ~ 8.2% /√E + 0.9% Calorimeter system : • Identify electrons, hadrons, π0 ,γ • Level 0 trigger: high ET electron and hadron Brookhaven Forum 2010

  10. Muon System m • Physics: BsJ/y f, Bsm+m-, etc. • Level 0 trigger: fast information from high Pt muons • OS flavour tagging Brookhaven Forum 2010

  11. Trigger Trigger is crucial as σbb is less than 1% of total inelastic cross section and B decays of interest typically have B < 10-5 40 MHz L0 m L0 had L0 e, g Level -0 • Hardware level (L0) Search for high-pT μ, e, γ and hadron candidates • Software level (High Level Trigger, HLT) Farm with O(2000) multi-core processors HLT1:Confirm L0 candidate with more complete info, add impact parameter and lifetime cuts HLT2: B reconstruction + selections 1 MHz ECAL Alley Had. Alley Muon Alley HLT1 High-LevelTrigger 30 kHz Global reconstruction Inclusive selections m, m+track, mm, topological, charm, ϕ HLT2 & Exclusive selections 2 kHz Storage: Event size ~35kB Very high efficiency Brookhaven Forum 2010

  12. p0,h and w in Data Data 2009 MC p0,hgg p0,hgg h,wppp0 Brookhaven Forum 2010

  13. First J/ψ data results (800mb-1) Loose selection Tight selection Pseudo-proper time in signal peak These are B→J/ψX candidates ! Can any be fully reconstructed? Brookhaven Forum 2010

  14. B+→J/ψK+ candidate Mass = (5326.7±10.9) MeV/c2Momentum: p = 62.7 GeV/c, pT = 10.48 GeV/cCos(a) = 0.9999, dist = 2.03mm Muons are magenta, kaon is red Brookhaven Forum 2010

  15. B+→J/ψK+ candidate XY Projection [mm] Tracks from primary vertex Primary vertex B+ m+ B decay vertex J/ψ K+ m- [mm] Brookhaven Forum 2010

  16. Muon identification studies Plan to use J/ym+m- to measure muon ID efficiency. Do not have sufficient statistics yet. Muon ID efficiency: ~94% (MC) Fake Rate of pm and pm Fake rate Fake rate LHCb 2010 preliminary LHCb 2010 preliminary p→μ dominated by combinatorics in muon stations p→μ dominated by decays in flight Brookhaven Forum 2010

  17. Search for CPV in Bs→J/ψf = - * * β arg( V V / V V ) s ts tb cs cb • Sensitive to New Physics effects in mixing • s= s(SM) + s(NP) • in SM: s = – 2βs= –0.036±0.002 • with 5.6 fb-1 current Tevatron result ~2.1σ away from SM value • Hope to improve significance with LHCb’s first year data +NP? CDF public note 9798 Brookhaven Forum 2010

  18. Bs→J/ψ(mm)f total CP even CP odd flat background • J/ is not a pure CP eigenstate (2 CP even, 1 CP odd amplitude) • Need to fit angular distributions of decay final states as function of proper time • Detector Requirements • Muon and Kaon ID • Proper time resolution (~40 fs) • Flavour tagging • LHCb expects about 2300 signal events / 100 pb-1 @ 7 TeV assuming s(bb)=219 mb Θtr= angle between l+ and normal to  decay plane Brookhaven Forum 2010

  19. LHCb prospects in Bs→J/ψf If nature agrees with Tevatron central value then LHCb can make 5σ discovery in coming run. Statistical precision on measured CPV phase of ~0.07 with 1 fb-1 • Including S-wave KK component will increase the error [Stone & Zhang arXiv: 0812.2832, 0908.3627] • Not included in Tevatron’s measurements 5s non-zero CPV phase if Tevatron central value is true This result will be complemented by equivalent measurement in CP-eigenstate Bs→J/ψf0(980), f0(980)→+-. fs sensitivity could be similar, depending on BR. [arXiv: 0909.5442] Brookhaven Forum 2010

  20. Bs→m+m- & Supersymmetry BR(Bs→μμ)SM = (3.35 ± 0.32) x 10-9 (Blanke et al., JHEP 0610:003,2006) Very high sensitivity to NP, eg. MSSM: SM Gaugino mass Brookhaven Forum 2010

  21. LHCb prospects for Bs→μμ @7+7TeV Exclusion limit @90% C.L. EACH • 3σobservation * 5σobservation BR(Bs0μ+μ-) (x10-9) • ~ 0.2 fb-1 to improve upon expected Tevatron limit with 8fb-1 • ~ 3 fb-1 for 3σ evidence and ~ 10 fb-1 for 5σ observation of SM value @ 14TeV Brookhaven Forum 2010

  22. B0K0m+m- • Very rare in the SM: B = (1.2 ± 0.1)×10-6 • Flavour-changing-neutral current (FCNC) process through penguin or box diagrams • Very sensitive to probe New Physics Brookhaven Forum 2010

  23. Angular Distributions ¶ G 2 3 3 µ q + - + q + q 2 2 F sin ( 1 F )( 1 cos ) A cos L l L l FB l ¶ q ¶ 2 cos q 4 8 l ¶ G 2 µ q + - q 2 2 2 F cos ( 1 F ) sin L K L K ¶ q ¶ 2 cos q K 1 0 G 2 d ò ò - q d cos l q 2 dq d cos = - l 0 1 A FB - 1 G 2 d ò q d cos l q 2 dq d cos - l 1 • Described by three angles (ql, f, qK) and di-m invariant mass q2 PRD61 (2000) 074024 SM Forward and backward asymmetry Compare with different SUSY models Zero point measures ratio of Wilson coeffs C9eff/C7eff Brookhaven Forum 2010

  24. From The Other Experiments • BELLE: 230 B →K*ℓℓ events in 657M BB [PRL 103: 171801, 2009] • BABAR:60B →K*ℓℓ events in 384M BB [PRD 79: 031102, 2009] • CDF: 100 B →K*mm events in 4.4 fb-1 [CDF note 10047] • LHCb expects ~350 in 300 pb-1(with m+m-only) @7TeV, B/S = 0.5±0.2 SM C7=-C7SM SM C9C10=-C9SMC10SM C7=-C7SM Both flipped sign Brookhaven Forum 2010

  25. LHCb Prospects for AFB • Assume Belle is right. If we measure the mean AFB in a bin 1-6 GeV2. How well can we exclude the SM? 100 pb-1: 1.5s 300 pb-1: 2.4s - 500 pb-1: 3.1s 1 fb-1: 4.0s With more data (~2fb-1), we can do full angular analysis to access more interesting observables (Egede, et al... arXiv:0807.2589) SM prediction - Belle - BaBar- LHCb expectation @ 7TeV Brookhaven Forum 2010

  26. Summary • LHCb is a precision heavy flavour experiment searching for New Physics at the LHC in CP violation and rare decays • 2010 run offers plenty of possibilities for significant measurements • Possibly improve Tevatron’s results on fs and Bsm+m- Exclusion limit @ 90% C.L. LHC and LHCb have highly successful run so far, the luminosity is increasing very fast log scale Brookhaven Forum 2010

  27. The LHCb Collaboration 730 members 15 countries 54 institutes Brookhaven Forum 2010

  28. Backup

  29. B0K0m+m- Sensitivity @ 14TeV Brookhaven Forum 2010

  30. Other Angular Variables in K*m+m- • Supersymmetry (Egede, et al... arXiv:0807.2589) • Use functions of the transverse polarization i are form factors 10 fb-1 model 1 With more L can distinguish between different SUSY models in some cases Brookhaven Forum 2010

  31. BSm+m- • Main concern: background suppression • Handles: mass resolution, vertex separation, use of pointing constraint • Muon misidentification dominated by decays in flight • For 2009, substitute Bsm+m- with a V0 m = (496.9 ± 0.2stat. ) MeV/c2 PDG: 497.61(2) MeV/c2s = (4.1 ± 0.1stat ) MeV/c2 MC: (3.6 ± 0.2stat ) MeV/c2 m = (1115.7 ± 0.1stat. ) MeV/c2 PDG: 1115.683(6) MeV/c2s = (1.4 ± 0.1stat ) MeV/c2 MC: (1.2 ± 0.2stat ) MeV/c2 • Mass resolutions of the V0 observed in 2009 data agree reasonably well with MC expectations. • Tracker alignment still ongoing. Alignment from magnet off data used.New alignment database for magnet on available since this week. • With 3.5 TeV, we expect a Bsm+m- massresolution of ~25 MeV/c2 Ks 

  32. BSm+m- • Main concern: background suppression • Handles: mass resolution, vertex separation, use of pointing constraint • Muon misidentification dominated by decays in flight • For 2009, substitute Bsm+m- with a V0 • Background rejection based on geometric likelihood Background Signal BSm+m-MC Geometriclikelihood

  33. Calibrating the signal source Prompt μ pJ/ψ PV z μ Δz From b Δz mJ/ψ t J/ψ= p J/ψ Tail from wrong PV z t J/ψ / ps Heavy flavour studies at LHCb will begin with a measurement of the bb cross-section, as determined from production rate of displaced J/ψ mesons Form pseudo proper-time, tJ/ψ: LHCb MC Combined fit to invariant mass and pseudo proper-time allows for both prompt J/ψ and bb production in bins of pt and pseudo-rapidity. Prompt J/ψ production a very interesting topic in its own right: Colour Octet Model (COM) predicts well cross-sections seen at Tevatron, but not polarisation Brookhaven Forum 2010

  34. LHCb J/ψ production studies Plan is to make study in: • 4 pseudo-rapidity bins, with 3 < η < 5 • 7 transverse momentum bins up between pt=0 and pt = 7 GeV/c LHCb inclusive J/ψ MC & background toy MC @ 14 TeV With 5 pb-1 all bins will have statistical uncertainty < 10% Largest systematic will come from unknown polarisation – varies bin to bin up to maximum of 25%. Polarisation will be measured in 2nd pass analysis. Expected integrated luminosity uncertainty ~5% through measurements of beam profile in beam-gas and beam-beam collisions. LHCb 2009 preliminary beam 2 vs empty beam 1 vs empty (Already determined to 15% in 2009, with uncertainty limited by knowledge of beam intensities) beam 1 vs beam 2 Brookhaven Forum 2010

  35. Bs→Dsμn candiate in first data Any New Physics phase contributing to Bs→J/ψФ will also be seen in semi-leptonic flavour asymmetry measured in eg. Bs→Dsμ These events are beginning to accumulate ! Brookhaven Forum 2010

  36. Flavour tagging at LHCb same side kaon tagger b Bs s b K+ s K- K+ u m+ m- u Same side primary vertex signal Bs proton proton vertex-charge taggerfrom inclusive vertexing Opposite side opposite B opposite kaon tagger (K-) K/p separation using RICH critical positive lepton taggers from bclcascade negative lepton taggers (e-, m-) from b-quark BsJ/: efficiency e~ 55.7%, mistag rate w~33.3%, e(1-2w)2~6.2% Brookhaven Forum 2010

  37. Kaon ID (MC) Bs → Ds K SS flavour tagging ,K Bs KK : 96.77 ± 0.06% pK : 3.94 ± 0.02% K K Ds  Primary vertex btag Brookhaven Forum 2010

  38. Angular Distributions ¶ G 2 3 3 µ q + - + q + q 2 2 F sin ( 1 F )( 1 cos ) A cos L l L l FB l ¶ q ¶ 2 cos q 4 8 l ¶ G 2 µ q + - q 2 2 2 F cos ( 1 F ) sin L K L K ¶ q ¶ 2 cos q K ¶ G 2 1 µ + - f + f (2) 1 ( 1 F ) A cos 2 A sin 2 L T Im ¶ f ¶ 2 q 2 K • Described by three angles (ql, f, qK) and di-m invariant mass q2 (a-d) MSSM with different inputs SM Transverse asymmetry AT sensitivity to right-handed current search. (2) arXiv:0807.2589 Brookhaven Forum 2010

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