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LHCb Physics reach

LHCb Physics reach. Marco Musy Universit à di Milano Bicocca and INFN Milano LHC2003 International Symposium Fermilab, 3 th May 2003. Overconstrain the unitarity triangles Search for New Physics beyond SM. Ambitious physics goals of LHCb. Precision CPV measurements, using also

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LHCb Physics reach

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  1. LHCb Physics reach Marco Musy Università di Milano Bicocca and INFN Milano LHC2003 International Symposium Fermilab, 3th May 2003 Fermilab 3th May 2003

  2. Overconstrain the unitarity triangles • Search for New Physics beyond SM Ambitious physics goals of LHCb Precision CPV measurements, using also pure hadronic and multi-body final states (Bd pp, BdD*p, . . .) Exploit CPV in new decay channels as in Bs (BsKK, BsDsK, BsJ/yf , . . .) Rare b-decays (BdK* g, BdK*mm, Bsmm . . .) New particles may show up in loop diagrams, overconstrain will allow to disentangle SM components from the new-physics ones b b t High statistics is a requirement NP? d d t Fermilab 3th May 2003

  3. BdJ/yKS BdD*p Bs mixing fNR  |Vub/lVcs| • If New Physics is there LHCb experiment can spot it in 2008 ! r r 2007 CPV from LHCb in one year |Vtd/Vts| sin 2b gand dgnotwell known |Vub/lVcs| 2008 LHCb 2007 h now Bdpp BdJ/yKS BsJ/yf BsDsK Fermilab 3th May 2003

  4. Experimental challenge HIGH STATISTICS BdK*g BdJ/y r 0 • LHCb has to deal with a large variety of final states with different topologies • Hot pp environment needs a robust trigger sbb / sinel.~ 0.01 (sbb~ 500 mb), many particles are not associated to b-hadrons • b-hadrons do not evolve coherently • High bb yield, 1012/year of Bd, Bs , baryons, Bc with bgct ~ 7mm Fermilab 3th May 2003

  5. LHCb detector Detector has undergone a reduction of material in front of RICH2 (60%  40% for X0, 20%  12% for lI) Less interactions in detector, Level-1 Trigger includes momentum measurement Technologies have not changed  September 2003: “Detector Reoptimization TDR” and “Trigger TDR” Construction phase is in good shape ( T. Nakada talk) Fermilab 3th May 2003

  6. Fully simulated bb event in Geant3 • MC Pythia 6.2 tuned on CDF and UA5 data • Multiple pp interactions and spill-over effects included • Complete description of material from TDRs • Individual detector responses tuned on test beam results • Complete pattern recognition in reconstruction: MC true information is never used • 1M inclusive bb events produced in Summer 2002 • New “Spring” production ready: 10M events for September TDRs • Sensitivities quoted here are obtained by rescaling earlier studies to the new yields Fermilab 3th May 2003

  7. RICH RICH-1 2<p<100 GeV/c <e(KK)>= 88% <e(K )>=2.7% Tracking • <Ntracks>= 27 “physics” tracks etrack~95% p>5 GeV/c “ghost” rate ~ 8% @pT>0.5GeV e, m PID <e(mm)>= 86% <e(ee )>= 78% <e( e,m)>=1% Main performances VELO PV: s~ 47 mm SV: s~170 mm VELO Bs mixing Measure Dms at 5s up to 48 ps-1  see dedicated talks! Fermilab 3th May 2003

  8. eacc* e2track* ecut* eL0* eL1= 13% * (96%)2* 22% * 61% * 51% Event yielduntagged 1 year = 2 fb -1 L= 2x1032 cm–2s-1 Efficiency includes: • Geometrical acceptance, eacc including detection efficiency, material • Trigger efficiency: Level-0 && Level-1, eL0,1 including expected Pile-up rate veto • Reconstruction efficiency (tracking, calorimeters, PID),etrack • Selection cuts efficiency to reconstruct the final state and reject background, ecut norm. to 4p Fermilab 3th May 2003

  9. p+ p- B0 B0 D K- l b B0 d b d p+ u u Flavour tagging Knowledge of flavour at birth is essential for the majority of CPV measurements Opposite side lepton tag ( b l ) Opposite side kaon tag ( b  c s ) - unique to LHCb, BTeV - correlated to hadron trigger Same side pion and kaon tag (with p coming either from B** or fragm. successfully used by CDF already) Vertex charge tagging • Only single particle tagging (e, m, K) from opposite side B decay used in this presentation e= 0.40,D = 0.40 eD2 = 6.4% • The new MC data give similar results Fermilab 3th May 2003

  10. eeff Bs Opposite Side Flavour tagging K-tag Typical tagging efficiencies: in BsK p, KK, Dsp channels (after L0*L1 trigger, any nr of collisions) IP/s Bs Same Side K-tag Work is in progress to update and improve the efficiencies Fermilab 3th May 2003

  11. B(s) pp,K p,K K min IP/s max pT Proper time s = 41 fs incl. bb • Selection cuts on Signal charged tracks, PID Reconstructed B signal 92% purity s=18 MeV/c2 pT(B) L/sL • Combinatorial bb bckgr, can be fully rejected even relaxing mass cut S/B ~ 1 Fermilab 3th May 2003

  12. g from B(s) pp, K K(proposedby R. Fleischer ) • Relies on “U-spin” symmetry assumption (ds) which is the only source of theoretical uncertainty • Clean measurement of g assuming dg from Bs J/y f and bfrom B  J/y Ks • Sensitive to New Physics contribution which can be pointed out by comparing with g obtained from DsK Fermilab 3th May 2003

  13. BS K+ K- B0  +- g from B(s) pp, K K input values Evaluation of and sensitivity from time-dependent measured asymmetry Fermilab 3th May 2003

  14. g from B(s) pp, K K BS K+ K- increasing xs BS K+ K- CP asymmetry can be measured in Bs KK up to xs=40 with an error increase of a factor 1.6 For xs=20 s(g) ~ 3o New! tagging efficiency  In one year: B0  +- BS K+ K- Fermilab 3th May 2003

  15. afrom B0 pp RICH PID and hadron trigger are fundamental Decay is polluted by penguin diagrams Penguin/Tree might be as high as 0.2 If |P/T| will be known to ±0.1 then 5°< s(a) < 10°(depending on parameter value) Fermilab 3th May 2003

  16. , K Bs K K Ds  Bs Dsp,DsK 72k Ds 8k DsK • ~ 6.5 MeV/c2 s = 168 mm s = 418 mm Bs vtx resolution (mm) Ds vtx resolution (mm) Dsmass (GeV) When selectingBs DsK BR(Ds K)/BR(Ds ) = 1/15 while (Ds K)/(Ds ) = 70 thanks to the RICH PID Fermilab 3th May 2003

  17. gfromBs D-s K+ , D+s K- Needed: • Hadronic trigger • K/p separation • Good proper time resolution From the measurement of 4 time-dependent asymmetries one gets g-2dg (with 2dg from BsJ/yf) 2 same order tree level amplitudes (3) : large asymmetries, NP contributes unlikely Sensitivity depends upon • relative amplitudes • strong phase difference • values of g, Dms , DGs /Gs For Dms=20 ps–1: s(g) ~ 10o For Dms=30 ps–1: s(g) ~ 12o In one year: 8k BsDsKreconstructed events Same principle holds for B0D*p, (study at the time of TP gives similar precision on g, a new evaluation is under way) Fermilab 3th May 2003

  18. dgfromBs J/y f In SM fS = -2dg = -2l2h ~10-2 Sensitive to New Physics effects in the Bs-Bs system J/y f is not CP eigenstate: needs fit to angular distributions of decay final states as a function of proper time In one year: 109 k events Bs J/y (m+m-) f 19 k events Bs J/y (e+e-) f Assuming Dms=20 ps–1: s (2dg) ~ 2o s=36±1 fs will be updated for TDR Determination of DGs s( DGs/ Gs) ~ 0.03 for DGs/Gs = 0.15 Fermilab 3th May 2003

  19. bfromB0 J/y Ks The ‘gold plated’ channel at B-factories Precision measurement of this parameter is very important: =sin 2b =0 in SM LHCb will bring a lot of statistics to this channel, which can be used to look into higher order effects, and fit Adir will be updated for TDR In one year with 119k events: s (sin 2b ) ~ 0.02 Comparing with other channels may indicate NP in penguin diagrams Fermilab 3th May 2003

  20. Rare decays:B0 K0*g BR( B0 K0*g ) = (4.30.4)10-5 Direct CP violation in SM <2%  Sensitive to New Physics effects g W b u,c,t s Mass resolution ~72 MeV Background from B0K*p0 can be rejected using K* helicity In one year: 20k events B0 K0* (K+p-) g triggered and reconstructed Fermilab 3th May 2003

  21. Bc mesons • LHCb acceptance ~30% • Possible CPV with Bc J/yD, Bc  DsD, DD, ... • Precision measurement of mass, life-time CDF: mBc= 6.4  0.4 GeV, tBc ~ 0.5 ps p (GeV) LHCb preliminary study s(ppBc) ~300 nb 109 Bc/ year Bc  J/y p (BR ~10-2) e ~ 2% 12k events/year Background from B J/y X and prompt J/y reduced cutting on the distance between primary vertex and Bc vertex M( J/y(mm) p) GeV/c2 Fermilab 3th May 2003

  22. Current status of LHCbPhysics Reach in 1 year (2fb–1) *Precisions obtained by scaling old results with the new yields All numbers will be updated together with more channels in the re-optimization TDR (September 2003) Fermilab 3th May 2003

  23. Systematics in CPV measurements Possible sources of systematic uncertainty: • Asymmetry of b vs b production • Detector efficiencies which depend on charge can bias tagging efficiencies can fake CP asymmetries • CP asymmetry also in background processes • Alternate runs, swapping the orientation of magnetic field • Use control samples available with high statistics: Bs Dsp 72k events/year B0 J/y K* 600k events/year B J/y K 600k events/year • Study CP asymmetries in the B mass side bands (from Technical Proposal) Fermilab 3th May 2003

  24. Conclusion • LHCb is a dedicated detector for B physics measurements in many channels from the beginning of LHC • A very precise determination of CKM unitarity triangle will be possible • Detector performances are being evaluated with a realistic and complete Monte Carlo simulation • LHCb offers an excellent opportunity to spot New Physics signals beyond Standard Model very soon at LHC Fermilab 3th May 2003

  25. back-up slides Fermilab 3th May 2003

  26. p0 reconstruction • PreShower (scintillator+Pb+scintillator) 2X0 • ECAL (Pb+ “shashlik” scintillator) 25X0 s(E)/E=10% /E1.5% • HCAL (Fe+scintillator) 5.6 lI s(E)/E=80% /E10% pT>200 MeV Purity ~20% in range 0.1<m <0.17 GeV/c2 Fermilab 3th May 2003

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