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

Ambitious physics goals of LHCb Overconstrain the unitarity triangles Search for New Physics beyond SM 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 t b High statistics is a requirement NP? d t d Marco Musy Fermilab 3th May 2003

CPV from LHCb in one year 2007 CPV from LHCb in one year |Vtd/Vts| sin 2b g and dg not well known |Vub/lVcs| r  fNR Bs mixing BdJ/yKS Bd D*p |Vub/lVcs| If New Physics is there LHCb experiment can spot it in 2008 ! 2008 LHCb h 2007 now BdJ/yKS Bdpp BsJ/yf Bs DsK Marco Musy Fermilab 3th May 2003

Experimental challenge Bd K*g HIGH STATISTICS 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 Marco Musy Fermilab 3th May 2003

LHCb detector Technologies have not changed 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) Marco Musy Fermilab 3th May 2003

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 Marco Musy Fermilab 3th May 2003

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

Event yield untagged e tot L = 2x1032 cm–2s-1 eacc* e2track* ecut* eL0* eL1= 13% * (96%)2 * 22% * 61% * 51% Channel e tot Yield B0  p+p- 0.78 % 27 k B0  K+ p- 0.85 % 115 k Bs  K+ K- 0.94 % 35 k Bs Ds-p+ 0.26 % 72 k Bs Ds-K+ 0.34 % 8 k Bs J/y (m-m+ )f 1.66 % 109 k Bs J/y (e-e+ )f 0.29 % 19 k B0 J/y(m-m+) KS 0.76 % 119 k B0K0* g 0.09 % 20 k 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 Marco Musy Fermilab 3th May 2003

Flavour tagging l B0 D p+ p- K- 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 b d u B0 p+ Only single particle tagging (e, m, K) from opposite side B decay used in this presentation e = 0.40, D = 0.40  e D2 = 6.4% The new MC data give similar results Marco Musy Fermilab 3th May 2003

Flavour tagging eeff εtag ωtag εeff TOTAL Bs Opposite Side K-tag Typical tagging efficiencies: in Bs  K p, KK, Dsp channels (after L0*L1 trigger, any nr of collisions) Method εtag ωtag εeff m 12.4 35.5 1.0 ±0.1 e 7.7 43.3 0.14 ±0.07 K (OS) 26.3 36.2 2.1 ±0.3 K (SS) 17.3 29.7 2.9 ±0.3 Vtx Charge 23.9 40.0 0.9 ±0.2 IP/s Bs Same Side K-tag TOTAL 65.8 34.8 6.1 ±0.4 Work is in progress to update and improve the efficiencies Marco Musy Fermilab 3th May 2003

B(s)  p p, K p, K K max pT min IP/s pT(B) L/sL incl. bb 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 Marco Musy Fermilab 3th May 2003

g from B(s) p p, K K (proposed by 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 b from B  J/y Ks Sensitive to New Physics contribution which can be pointed out by comparing with g obtained from DsK Marco Musy Fermilab 3th May 2003

g from B(s) p p, K K BS  K+ K- BS  K+ K- B0  + - B0  + - yield 27k 35k B/S 0.8 0.55 xq 0.755 20 D2 0.064 -0.30 0.16 0.58 -0.17 DG 0.0 input values Evaluation of and sensitivity from time-dependent measured asymmetry B0  + - BS  K+ K- Marco Musy Fermilab 3th May 2003

g from B(s) p p, K K s(g) ~ 3o B0  + - BS  K+ K- In one year: tagging efficiency  BS  K+ K- In one year: B0  + - BS  K+ K- BS  K+ K- increasing xs  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! Marco Musy Fermilab 3th May 2003

a from B0  p p 5°< s(a) < 10° (depending on parameter value) 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) Marco Musy Fermilab 3th May 2003

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

g from Bs  D-s K+ , D+s K- s(g) ~ 10o s(g) ~ 12o 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 la collins dice 2.5k?? 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) Marco Musy Fermilab 3th May 2003

J/y f is not CP eigenstate: dg from Bs  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 paula c. dice 74k in totale!? e 2 gradi di precisione Determination of DGs s( DGs/ Gs) ~ 0.03 for DGs/Gs = 0.15 Marco Musy Fermilab 3th May 2003

b from B0  J/y Ks The ‘gold plated’ channel at B-factories Precision measurement of this parameter is very important: =0 in SM =sin 2b 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 Marco Musy Fermilab 3th May 2003

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 Marco Musy Fermilab 3th May 2003

Bc mesons s(ppBc) ~300 nb  109 Bc/ year LHCb acceptance ~30% Possible CPV with Bc J/y D, 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 Marco Musy Fermilab 3th May 2003

Current status of LHCb Physics Reach in 1 year (2fb–1) Channel Yield Precision* b Bd  J/y Ks 119 k s(b)  0.6o g Bs  DsK Bd  pp, Bs  KK 8 k 27 k, 35 k s(g) 10o s(g)  3o a Bd  p+p- 27 k s(a)  5o- 10o 2dg Bs  J/y f 128 k s(2dg)  2o |Vtd/Vts| Bs  Dsp 72 k Dms up to 58 ps-1 rare decays Bd  K* g 20 k *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) Marco Musy Fermilab 3th May 2003

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) Marco Musy Fermilab 3th May 2003

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 Marco Musy Fermilab 3th May 2003

back-up slides Marco Musy Fermilab 3th May 2003

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 Marco Musy Fermilab 3th May 2003