Status and Physics prospect at LHCb

1. Status and Physics prospect at LHCb Éric Conte, on behalf of LHCb collaboration Laboratoire de Physique Corpusculaire de Clermont-Ferrand QCD08, 7-12 July 2008, Montpellier

2. Detector design Detector and Trigger are designed for B physics studies @ LHC collider • LHC characteristics : √s = 14 TeV, stotal = 100mb,sinelastic = 80mb • Cross-section of bb production : large uncertainty LHCb conventions : s(ppbb) ~ 500 µb(0.5% of the total cross section) • bb production is sharply peaked forward-backward  LHCb single-arm forward spectrometer : 1.9<|η|<4.9 • LHCb limits luminosity to few1032cm-2s-1 instead of 1034cm-2s-1 by not focusing the beam as much as ATLAS and CMS maximizes probability of a single interaction per crossing • ~1012 bb pairs produced with 2 fb-1 Status and Physics prospect at LHCb Slide 2 / 17

3. Calorimeters Magnet RICH2 Muon RICH1 IT+OT VELO LHCb detector elements HCAL ECAL M5 M4 PS/SPD 5m M3 M2 RICH2 Magnet M1 T3 T2 T1 RICH1 TT VELO 20m 15m 10m 5m Status and Physics prospect at LHCb Slide 3 / 17

4. ε(K K) : 97% ε(p  K) : 5% Detector requirements & performances • B hadron signature : particles with high PT (few GeV) coming from a displaced vertex (typically L~1cm from primary vertex) • Reconstruction of b hadrons decays is based on : • mass resolution and excellent particle id to reject background • good proper time resolution to resolve B0S oscillations • Tagging the quark flavour at production : • From combination of several methods, effective tagging power : 4 - 5% for B0d, 7 - 9% for B0s 5 μm hit resolution ~30 μm IP resolution  40 fs resolution B mass resolution ~15-20 MeV/c2 Status and Physics prospect at LHCb Slide 4 / 17

5. LHCb 2-level Trigger Status and Physics prospect at LHCb Slide 5 / 17

6. Installation and commissioning status • All subdetectors are installed and cabled (except M1 muon station which is not required for the first runs) • Integration, calibration and time-alignment of the different elements are performed with cosmic data. In the following event, cosmic particle hits Outer Tracker (OT), calorimeters and muon stations. The yellow line is the track fit by calorimeter hits, although the green line is the track fit by OT hits. x y z z We will be ready for the LHC start-up !!! 1rst July 2008 Status and Physics prospect at LHCb Slide 6 / 17

7. LHCb schedule Status and Physics prospect at LHCb Slide 7 / 17

8. LHCb physics program, part I : CP violation b  d transitions broadly studied, in general good agreement with Standard Model measurement and confirmation of B0d mixing parameters still limited knowledge, space for New Physics (NP) effects especially, the mixing phase Φs of B0s-B0s oscillations : b  s transitions Φs is predicted with precision by the Standard Model : Could be much larger if NP contribute to B0s-B0s transitions B0s eiΦs f Current measures must to be improved : B0s Status and Physics prospect at LHCb Slide 8 / 17

9. LHCb physics program, part I : CP violation Φs can be extracted from CP time-dependent asymmetry in decay rates : with nf = ±1 CP eigenstate • Which signal for this measurement ? • Pure CP eigenstates • ex : B0sJ/Ψη, B0sJ/Ψη’, B0sηcΦ, B0dDs+Ds- • Low yield, high background • Admixture of CP eigenstates • B0s  J/ΨΦ : Large yield (130k for 2fb-1), nice signatures  golden channel • BUT requires angular analysis to disentangle even (ηf=+1) and odd (ηf=-1) eigenstate Yield of 2-8 k/channel with 2fb-1 s(fs)=0.046 s(fs)=0.023 with 2fb-1 Status and Physics prospect at LHCb Slide 9 / 17

10. LHCb physics program, part I : CP violation CKM mechanism parameter measurement Unitarity triangle in the -η plane • angle is poorly constraint and LHCb contribution to this measurement is expected ! Status and Physics prospect at LHCb Slide 10 / 17

11. LHCb physics program, part I : CP violation 1 3 independent ways to extract g angle : • from tree amplitudes : B0s DsK • 2 amplitudes, bc & bu, interfere via B0s mixing • Access to g+Fs in a very clean way •  σ(g+Fs ) = 9-12° with 2fb-1 • 2) from tree amplitudes : B  DK • 2 amplitudes, bc & bu, interfere in decays to a common D0 and D0 modes state, fD • Analysis methods (GLW, ADS, Dalitz) depend on the fD nature • g can extracted from the time independent asymmetry •  global fit of all the channels : σ(g) = 4.3-6.2° with 2fb-1 • 3) from penguin amplitudes : B  hh • Interference of bu tree & bd(s) penguin diagrams leads to CP violation effect which depends on g • Sensitive to New Physics •  σ(g)=10° with 2fb-1 2 3 Status and Physics prospect at LHCb Slide 11 / 17

12. LHCb physics program, part II : rare decays Rare B decays give opportunities to constrain New Physics contributions (bl+l-, bsl+l-, bsg, ...) We will focus on 2 relevant examples : B0s µ+ µ- BR sensitive to NP, especially SUSY MSSM enhancement ~tan6β/MA larger value Standard Model prediction : BR = (3.35 ± 0.32)  10-9 D0 & CDF results : BR < 4.710-8 (90% CL)  NP can contribute to one order of magnitude LHCb potential : 3 (blue) and 5 (red) observation of a BR as a function of integrated luminosity SM BR With SM Branching ratio 2 fb–1 3 evidence 6 fb–1 5 observation Status and Physics prospect at LHCb Slide 12 / 17

13. LHCb physics program, part II : rare decays 10-7 2x10-8 Useful informations to constrain SUSY model parameters 5x10-9 Status and Physics prospect at LHCb Slide 13 / 17

14. LHCb physics program, part II : rare decays B0d K*0 µ+ µ- Observable sensitive to NP: muon forward-backward asymmetry in the µ+µ- rest frame µ+  B K0* µ- First measurement : AFBzero point crossing SM prediction : Status and Physics prospect at LHCb Slide 14 / 17

15. LHCb physics program, part III : other Physics • ppbb cross-section estimation • production knowledge improvement • charm physics : D0 mixing and other CP violation studies • measurement B+c or Λ0b particle characteristics (mass, lifetime, …) • spectroscopy of heavy-flavoured hadrons • potential to observe News Physics processes with b-jets • … Status and Physics prospect at LHCb Slide 15 / 17

16. LHCb physics program, part III : other Physics b cross-section measurement Test predictions on pQCD and constrain fragmentation models. LHCb : comparison with QCD in region of phase space not accessible to previous hadron-collider experiments. The cross-section of a process X can be determined by : Used process : bJ/ΨX BR = (1.16±0.10)% Analysis : distinguish J/Ψ from b and prompt J/Ψ. Discriminating variable : 1% statistical precision on total b-cross section already at 50 nb−1. This measure is limited by the BR(bJ/ΨX) uncertainty. Status and Physics prospect at LHCb Slide 16 / 17

17. SUMMARY LHCb is an experiment dedicated to B physics, searching New Physics @ LHC energy scale. August 2008 : first proton beams used for detector calibration. 2009 : physics runs will begin with 0.5 fb-1. We hope to collect 10 fb-1 by 2013. LHCb will extend Babar, Belle and Tevatron results and will contribute to improve our B physics knowledge, essentially : CP violation Rare decays • Fs mixing phase : s=0.023° • g from trees : s=5°-10° • g from penguins : s=10° • B0smm : 3s of the SM BR • BK*mm : s(s0)=0.5 GeV2 with 2fb-1 We are ready to run and to do physics !!! Status and Physics prospect at LHCb Slide 17 / 17