Status and Physics reach of LHCb

1. Heavy Quarks & Leptons 08 Melbourne 5-9 June 2008 Status and Physics reachof LHCb Marta Calvi Università Milano-Bicocca and INFN On behalf of the LHCb collaboration

2. The Large Hadron Collider LHC start up is approaching: - Cooling down proceeding well, aiming for machine cold in the first half of July. - Beam injected end July - early August. First collision 1-2 months later. - Luminosity 1031 cm–2s–1

3. bb angular correlation in pp collisions at s = 14 TeV (Pythia) pp interactions/crossing LHCb n=0 n=1 LHCb @ LHC Huge bb production in pp collisions at s=14TeV, in the forward region • sbb = 500 mb  N 1012 bb events in Lint =2 fb-1 • inel = 80 mb A possible running scenario: 2008 Expect 50 days of data taking with limited efficiency, L1031 cm–2s–1 Calibration and Trigger commissioning / First results for non-CP physics 2009 Expect 140 days of data taking, L2x1032 cm–2s–1 First results on rare decays and CP physics ~ 0.5 fb–1 2010- Stable running. Expect~ 2 fb–1/ year LHCb planes to collect an integrated luminosityof10 fb–1for year2013

4. LHCb Detector in place Detector installed, going to close and be ready for data-taking. Commissioning with cosmics on-going. Calorimeters OT+IT Magnet RICH-2 Muon detector RICH-1 VELO

5. 144mm  Bs 47mm K K Ds 1 cm  440mm  Primary vertex Bs  μμ Bs KK LHCb expected performance (I)B vertex and mass measurement B proper time resolution 40 fs VErtex LOcator (Silicon strip)  5 mm hit resolution  30 mm IP resolution From full tracking system (TT+ IT + OT): Momentum resolution s(p)/p 0.3%-0.5% increasing with p B mass resolution 15-20 MeV/c2 All results obtained from full Detector (GEANT4) MC simulation

6. m-,e- K– Qvtx D B– Bs PV K+ LHCb expected performance (II)Particle IDentification RICH1: 5cm aerogel n=1.03 4m3 C4F10 n=1.0014 KK : 97.29 ± 0.06% pK : 5.15 ± 0.02% RICH2: 100m3 CF4 n=1.0005 Flavour Tagging performance from combination of several methods (electron, muon, kaon, pion, inclusive vertex): eD2 =4-5% for Bd eD2 =7- 9 % for Bs depending on channel

7. ECAL+ HCAL VELO MUON e, g, h high pT m high pT Pile up LHCb Trigger L0, HLT and L0×HLT efficiency 40 MHz Level-0 All DATA 1 MHz High Level Trigger 2 kHz Storage event size ~50 kB

8.  Improve precision on g and other CKM parameters, search for NP from comparison between tree and box / penguin contributions. Examples: bs from BsJ/yf, g from B(s)D(s)K, penguins in Bsff • Search for NP in rare decays, with high precision measurements of BRs and time dependent CP asymmetries. • Examples: Bsmm, Bd K0*mm, Bsfg LHCb: motivation and Physics Program LHCb is a 2nd generation precision experiment coming after B-Factories and Tevatron: • b  d transitions: broadly studied, in general good agreement with SM. • b  s transitions: still limited knowledge, space for NP effects. • Strong constraints to SM available from precision measurements of CKM parameters, but g angle still poorly known. • High statistics production of all kind of b- (and c-) hadrons at LHC allows extensive studies in wide set of channels.

9. Bs Mixing phase bs with bccs (I) • The sin 2bd analogous in the Bs sector. • The phase arising from interference between B decays with and without mixing is a sensitive probe to new physics. In the SM FSM = -2bs=-0.0368±0.0017 • Could be much larger if New Physics contributes to Bs-Bs transitions. From BsJ/yf we measureFmeas = FSM + FNP • Tevatron results: D0 2bs= - 0.57 + 0.24-0.30 with 2.8 fb-1 could be a hint of NP? CDF 2bs= [0.32,2.82] @ 68%CL with 1.35 fb-1 • Time-dependent asymmetry in decay rates:

10. total CP even CP odd flat background Bs Mixing phase bs with bccs (II) • BsJ/y(m+m-)f(K+K-) is the golden channel, requires angular analysis to disentangle the mixture of CP-even (hf= -1 ) and CP odd (hf=+1) • Use flavour tagged and untagged events. • Need very good proper time resolution to resolve Bs oscillations. • Can add pure CP modes: J/, J/’, c, Ds+Ds- • but much lower statistics. With 0.5 fb–1(2bs)0.046 With 10 fb-1stat(2bs) 0.009 > 3 evidence of non-zerobs even if only SM Sensitivity to other fit parameters (with 2 fb-1): s(Γs/Γs )=0.0092, s(RT)=0.0040

11. New Physics in Bs mixing Ligeti, Paucci,Perez, hep-ph/0604112 New Physics in Bs mixing amplitude M12 parameterized with hs and s: s 2006 including ms measurement Additional constraints can come from semileptonic Asymmetry. In SM: ASLs10-5. ASLs With 2bsfrom BsJ/ LHCb 2fb-1 hs Preliminary results on the LHCb measurement of time dependent charge asymmetry in BsDsn Expect 109 events/ 2fb-1d(ASLs )2x10-3 in 2fb-1 hs

12. bsss hadronic penguin decays Bs  • In SM CP violation < 1% due to cancellation of the mixing and penguin phase: Bs  SM  2 arg(Vts*Vtb) – arg(VtsVtb*) = 0 • In presence of NP expect different contributions in boxes and in penguins: Bs  NP = MNP -DNP + NP? • From the time dependent angular distribution of flavour tagged events, in 2 fb–1 stat(NP) = 0.11 • Less statistics on Bd  f KS , expected precision: (sin(2eff)) ≈0.23

13. Different ways to g at LHCb tree decays only And several additional modes under study: B+→D*K+ (DKp,KK,pp), B+→DK+(DKppp) …

14. DsKtagged as Bs  from Bs DsK • Two tree decays which interfere via Bs mixing  determine  in a very clean way • Fit time-dependent rates of Bs→DsK and Bs→Dsp - Including BsDsp to constrain Dms and mistag - Use tagged and untagged Bs→DsK samples Sensitivity with 2fb–1:

15. Different ways to g at LHCb • Global fit combining χ2 from the different ADS/GLW rates and Dalitz: s(g) 2fb-1 • Combining with time dependent measurements ( DsK and Dp ) gives a global LHCb sensitivity to  with tree decays only:() ~ 4º with 2 fb–1

16. Bs mm SM • Highly suppressed in SM: BR(Bs→mm)=(3.35±0.32) x10-9 - Could be strongly enhanced by SUSY: BR(Bs→ mm)  tan6b/MH2 - Current limits from Tevatron ~2 fb-1: CDF BR < 4.7 x 10-8 90% CL D0 BR < 7.5 x 10-8 90% CL LHCb: high stat. & high trigger efficiency for signal, main issue is background rejection. Largest background is b m, b m. Specific background dominated by Bc± →J/y(mm) m±n Exploit good mass resolution and vertexing, and good particle ID.

17. Bs mm • Analysis in a Phase Space with 3 axis: • Geometrical Likelihood (GL) (impact parameters, distance of closest approach between mm, Bs lifetime, vertex isolation) • Particle-ID Likelihood • Invariant mass window around Bs peak • - Sensitive Region: GL > 0.5 • - Divide in N bins • Evaluate expected number of events for signal/background in each bin. • Assuming SM BR, in 2fb-130 signal events • 83 background events signal bb inc. b μ, b μ Bc+ J/Ψμν (arbitrary normalization) • Normalization from B+J/yK+ events. Dominant uncertainty on BR from relative • Bs,B+ hadronization fractions 14%.

18. 90% CL limit on BR (only bkg is observed) 10-7 2x10-8 (~0.05 fb-1) BR (x10–9) Expected final CDF+D0 limit Uncertainty in background prediction SM prediction 5x10-9 (~ 0.4 fb-1) Integrated luminosity (fb–1) Sensitivity to signal (signal+bkg is observed) BR (x10–9) 5 observation SM prediction 3 evidence Integrated luminosity (fb–1) Bs mm NUHM J.Ellis et al. arXiv:0709.0098v1 [hep-ph] (2007) Exclusion: 0.5 fb–1 < SM Within SM BR: 2 fb–1 3 evidence 6 fb–1 5 observation

19. Fast MC, LHCb 2 fb–1 AFB(s) s = m2 [GeV2] Bd K*mm • BR measured at B-factories, in agreement with SM: BR(BdK*mm)=(1.22+0.38-0.32)x10-6 • Decay described by three angles (qm, f, qK*). • Zero crossing point of forward-backward asymmetry AFB in qm angle, as a function of mmm, precisely computed in SM: s0SM(C7,C9)=4.39+0.38-0.35 GeV2 hep-ph/0412400 Ignoring non-resonant Kpmm events • Simple linear fit suggests precision:

20. FL AT(2) BdK*mm transverse asymmetries • Fitting projections of qm, f, qK*angular distributions can measure the fraction of longitudinal polarization FL and the transverse asymmetry AT(2): Points LHCb 2 fb-1 Stat. precisions in the region s = m2  [1, 6] (GeV/c2)2 where theory calculations are most reliable Sensitivity with Kruger & Matias, Phys. Rev. D71: 094009, 2500 m2 [GeV2] m2 [GeV2] Under investigation also full angular fit in terms of transversity amplitudes AL,R, A//L,R, A0L,R. Will improve precision on AFB.

21. Equivalent of 13mins of simulated bb events – already see a peak! True K*g signal events Combinatorial background Radiative decays Bd  K*AdirCP < 1% in SM, up to 40% in SUSY. Bs   Time dependent CP asymmetry allows to test the helicity structure of the emitted photon. In SM bsg predominantly left-handed. M(K*) In SM: Adir=0 (direct CPV) Amix=sin 2y sin AΔ= sin 2y cos  with tany =|b→sgR| / |b→sgL| As DGs≠0 Bs   probes AD, as well as Adir and Amix For cos≈ 1 ADsin 2ydetermines the fraction of “wrongly” polarized photon. With 2fb-1: s (AD) = 0.22 s (Adir, Amix )= 0.11

22. Charm physics • LHCb will collect a large tagged D*D0p sample (also used for PID calibration). A dedicated D* trigger is foreseen for this purpose. • Tag D0 or anti-D0 flavour with pion from D*±  D0 ± • Performance studies not as detailed as for B physics. • Interesting (sensitive to NP) & promising searches/measurements: • Time-dependent D0 mixing with wrong-sign D0K+– decays stat(x’2) ~0.14 x10–3, stat(y’) ~2 x10–3 with 2 fb–1 • Direct CP violation in D0K+K– • ACP 10–3 in SM, up to 1% with New Physics • Expect stat(ACP) ~ 0.001 with 2 fb–1 • D0+– • BR  10–12 in SM, up to 10–6 with New Physics • Expect to reach down to ~510–8 with 2 fb–1

23. LHCb beyond 10 fb–1 • Several measurements limited by stat. precision after 10 fb-1: investigating upgrade of detector to handle luminosity 2x1033 cm–2s–1 and integrate up to100 fb-1 – Not directly coupled to SLHC machine upgrade since luminosity already available, but may overlap in time with upgrades of ATLAS and CMS. • Technical solutions under study (increase trigger efficiency for hadronic modes, fast vertex detection, electronics, radiation dose, pile-up, higher occupancy etc.)  Expression of Interest for an LHCb upgrade submitted to LHCC. • Physics case: • CPV in Bs mixing (tree and penguins) • g angle with 1° precision • Chiral structure of bs from Bf and BK*m+m– Expected sensitivity for 100 fb-1 assuming a factor 2 in hadronic trigger efficiency and same reconstruction efficiency

24. Conclusions • LHCb is ready for data taking at LHC start-up. • Very interesting results will come already with first 0.5 fb-1 of data: • Bs J/yf 2bs measurement with 0.05 precision • Bs mmBR limit down to SM value • Bd  K0*mm1800events,overtaking B-Factories statistics • LHCb results will provide in the coming years a strong improvement to flavour physics, in particular to the knowledge of all Bs sector. • Actively preparing for analysis of several channels with high potential for indirect NP discovery. • Looking forward next HQ&L Conference to show all that!

25. BACK-UP

26.  from B±→ D0K ±(ADS+GLW) (I) Atwood, Dunietz and Soni, Phys. Rev. Lett. 78, 3257 (1997) Gronau, London, Wyler, PLB. 253, 483 (1991) • Charged B decay Weak phase difference – Strong phase difference dB Amplitude ratio rB ~ 0.08 colour favoured colour suppressed • D0and D0 can both decay into K-π+ (or K+π- ) Strong phase difference dDK Amplitude ratio rDKp =0.060±0.003 Cabibbo favoured doubly Cabibbo suppressed right sign, lower sensitivity to g wrong sign, high sensitivity to g Add CP eigenstatedecays D0→K+K–, +–

27.  from B±  DK±(ADS+GLW) (II) 6 decay rates and 7 parameters (rB, rD, δB,δD, γ , Nhh, NKp) . rD well-measured andδDconstrainedby CLEO-c ( from final statistics expect DcosδD~20%) Can solve for unknowns, including the weak phase . Add constraint on the relative D0 two body BR and selection efficiencies (know to better than 3%) () = 11–14 with 2 fb–1 • depending on D strong phases ( Inputs: =60, rB =0.1, dB =130, δKπ from Cleo-c)

28. colour-suppressed colour-suppressed  from B0 D0K*0 (ADS+GLW) Weak phase difference =  Magnitude ratio = rB ~ 0.4 • Treat with same ADS+GLW method as charged case: • So far used only D decays to K–+, K+–, K+K– and +– final states • Envisage also GGSZ analysis () = 9 with 2 fb–1 ( Inputs: =60, rB =0.4, dB =10)

29. m2(KS–) (770) K*(892) m2(KS+) D0 g from B±D0(Ksp+p-)K± (GGSZ) Giri, Grossman, Soffer, Zupan, PRD 68, 050418 (2003). Amplitude analysis of the D - Dalitz plots for B+ and B– decaysallows the extraction of γand rB,δB. Assume no CP violation in D0 decays B decay amplitudes: A(B-DK-) AD(mKp-2,mKp+2)+ rBei(dB- g ) AD(mKp+2,mKp-2) A(B+DK+) AD(mKp+2,mKp-2)+ rBei(dB+g ) AD(mKp-2,mKp+2) Sensitivity spread due to different background scenarios

30. 2 fb–1 stat() = 10+ fake solution 10 fb–1 stat() = 5+ decreased fake  from B and BsKK Sensitive to NP in penguins. Measure: Competitive with final Tevatron luminosity already for L=0.5fb-1 Advantage of strong PID system to separate Bh+h- modes. 2 fb–1 • Adir and Amix depend on d, bs, , deiq (P/T ratio) • Exploit U-spin symmetry (Fleischer): Assume: d=dKK and =KK: 4 meas. and 3 unknowns  can solve for  (taking d, bs from other modes) • Can relax U-spin requirements: 0.8<dKK/d<1.2 ,  ,KKfree

31. RK in B+ K+ℓℓ in SM (Hiller,Krüger PRD69 (2004) 074020) - Large corrections O(10%) possible in models that distinguish between lepton flavours (eg.MSSM at large tanb). Constraints to NP also from RK andBR(Bs→µµ) combined. LHCb 10 fb-1 Bu  eeK 9.2 k events Bu  mmK 19 k events • sstat(RK )= 0.043 • Trigger eff 70% on ee channel under study - not included. • Similar sensitivity expected for RK* =Bd mmK*/ Bd eeK*. 4mmm2< mll2< 6 (GeV/c2)2