1. Malcolm John 1/17 Early physics of LHCb Malcolm John On behalf of the LHCb collaboration 1.Very brief introduction 2.Status of LHCb 3.A selection of the most promising results

2. Malcolm John 2/17 (0,0)(0,1) (,)(,) V ub V ud * V td V tb * V cd V cb *  (0,0)(0,1) (1- 2 /2)( ,  ) V ub V ud * V td V tb * V cd V cb *    (0,0) (,)(,) V ub V tb V cd V cb * * V ud V td V cd V cb * *    (1 -   ,   ) 2 V us V ts V cd V cb * * At LHCb terms up to 5 must be considered  Major LHCb goals: Weak phase,,  Bs mixing phase  s =  2  arg (V ts ) B (B s   )  

3. Malcolm John 3/17 bb produced into forward region  pp → bb (  s=14TeV)  500  b operate at ℒ = 2x10 32 cm  2 s  1 10 12 b-hadrons a [10 7 s] year  80 GeV/c = 7mm The LHCb detector status in a nut-shell All major sub-detector intrastructure is installed and instrumentation is well underway LHCb will be ready to [space and time] -align during the 2007 LHC engineering run 2008: Calibrate the complete detector and trigger for  s =14TeV Expect 0.5fb  1 (50 billion b-quarks) 2009: Full physics data-taking Expect 2fb  1 /year

4. Malcolm John 4/17 LHCb at LHC - P8 Inset: retracted HCAL & muon filter

5. Malcolm John 5/17 VErtex LOcator 170 000 channels 8.1mm from beam (40<pitch<100)  m  Z (PV) < 50  m   (B s ) < 40fs Beam’s eye view

6. Malcolm John 6/17 Simulation Expectations are evaluated using the LHCb MC simulation software: Pythia, EvtGen, GEANT4 and Gaudi-based reconstruction (2004 MC data) –Detailed detector and material description (GEANT) –Pattern recognition, trigger simulation and offline event selection –Implemented detector inefficiencies, noise hits, effects of events from the previous bunch crossings Slide by Peter Vankov

7. Malcolm John 7/17 (0,0)(0,1) (1- 2 /2)( ,  ) V ub V ud V cd V cb * * V td V tb V cd V cb * *    B s → D s K B → D 0 K ( * )  = (82  20)° ( current direct measurements )

8. Malcolm John 8/17  from B s → D s K  Expect 6200 D s K events in 2 fb –1 B/S < 0.5 Expect 6200 D s K events in 2 fb –1 B/S < 0.5 Expect 140 000 D s  98% suppression achieved with RICH PID system in the analysis Used to measure  m s 2 fb –1 :  (  m s )  0.012ps –1 Expect 140 000 D s  98% suppression achieved with RICH PID system in the analysis Used to measure  m s 2 fb –1 :  (  m s )  0.012ps –1 + ch.c. diagrams Study sensitivity by generating toy-experiments with experimental inputs derived from full MC ( Decay time and mass resolution, reconstruction efficiency, tagging…) –Sensitivity with 2 fb -1 : σ(  ) ~ 13° Two tree decays (b  c and b  u), which interfere via B s mixing: –can determine (  s +  ), hence  in a very clean way Fit 4 tagged, time-dependent rates –Extract  s + , strong phase difference , amplitude ratio –B s  D s  also used in the fit to constrain other parameters ( ,  m s,  s )

9. Malcolm John 9/17  from B u,d → D 0 K Interplay of B u and D 0 decays where interferes with –charged Bs only (time-independent, direct CPV) –choose decay hierarchies in which large CP asymmetry is possible –“tree-level” dominates. No penguins pollution Colour favoured b  c amplitudeColour suppressed b  u amplitude → X  Also known as… → X Yield / 2 fb –1  (  ), 2 fb –1 ADS, GLW KK ~700 (56k † ) <15 º KK,  5k, 1.6k D0-Dalitz (GGZS) K S  5.0k8º8º B 0 self-tagging variant K , KK,  530, 470, 130 (3.3k † )8 º– 10 º A similar analyses possible with B 0 → D 0 K* 0 decays –The b → c transition is also colour suppressed. Expect large CP-asymmetries –self-tagging (i.e. the b-quark flavour is given by the sign of the prompt signal kaon) † favoured decay (not sensitive to  ) Benefit from CLEO-c …

10. Malcolm John 10/17 B s → J/  …etc… and B s →   (0,0) (,)(,) V ub V tb V cd V cb * * V ud V td V cd V cb * *    (1 -   ,   ) 2 V us V ts V cd V cb * *  s  arg (V ts )

11. Malcolm John 11/17 B s mixing phase:  s The equivalent of “sin2  “ for B s mesons In the standard model,  s is small: = -2arg(V ts )  0.036  0.003 –Could be larger if New Physics is present in the box diagram –Recent D0 result  s = –0.79 ±0.56(stat) +0.14–0.01(syst) with 1.1 fb –1 To resolve B s oscillations, excellent proper time resolution is required Modes sensitive to  s : –CP-odd & even: B s → J/  –CP-even only: B s →  c  B s → J/   B s → D s D s Control channel (  m s ): B s → D s  Illustration of CPV: toy-modeling LHCb data with  s =  0.2 (i.e. 5  SM) events tagged as B s

12. Malcolm John 12/17 Precision on a measurement of  s = 0.04 Yield in 2fb  1 B/Sσ  (fs)  mass (MeV/c 2 ) Comment B s → J/  131k0.123614Large yield but full angular analysis required 0.023 B s →  c  3k0.63012 Low yield High background 0.108 B s → J/   11k<33530 0.105 B s → D s D s 4k0.3566Poorest proper-time resolution 0.133 >90% CL >32% CL >5% CL from hep-ph/0604112 Current, including first measurement of  m s hshs ss Arbtrary new physics parameterisation: M NP = M SM (1+h s e i  ) With  (  s )= ±0.03 (~ 2 fb –1 ) (different x-scale) hshs ss 0.5 0.020 0.044 2fb  1 0.5fb  1

13. Malcolm John 13/17 B s →  FCNC gluonic penguin decay. Analogue of B 0 →  K s for the B s Dependence on V ts in both the decay and B s mixing amplitudes, phase cancels and leads to the SM CP-violation expectation < 1% –Large CP asymmetry would be a signature of New Physics The P  VV decay requires a full angular, time-dependent CP analysis Expect 4000 events/2 fb -1 (based on a CDF B.F. measurement: 1.4  0.9 x10  5 ) –Early feasibility studies suggest LHCb statistical precision on a New Physics phase (defined at 0.2 for the purposes of this work) in 2fb  1 is: ~0.10 Current combined, B-factory measurement of sin 2 β in B 0 →  K 0 S : 0.39 ± 0.18 –For comparison, the 2 fb -1 LHCb sensitivity in this mode is 0.32

14. Malcolm John 14/17 B s →  and B s → K * 0  New Physics enhancement of very Z0Z0 WW t t b s BsBs   WW t b s BsBs   WW  H 0 /A 0  b b s BsBs   t B.F.(B s  ) MSSM  tan 6  B.F.(B s  ) SM  3.5 x 10  9 rare B-decays

15. Malcolm John 15/17 B s  expected sensitivity Very exciting possibility of sensitivity to New Physics enhancement in the early period Current upper limit from the Tevatron is around 20 x SM prediction The dominate background is b , b . –Background analysis is currently limited by Monte Carlo statistics (generation) LHCb’s superior B s invariant mass resolution is crucial in the background rejection LHCb limit on BR at 90% CL (only bkg is observed) LHCb sensitivity (signal+bkg is observed) 5  observation 3  evidence SM BF (x10 –9 ) Integrated luminosity (fb –1 ) BF (x10 –9 ) Expected final CDF+D0 limit SM “early ” perio d Uncertainty in bkg prediction

16. Malcolm John 16/17 NP model descrimination possible with B 0  K* 0     s = (m  ) 2 [GeV 2 ] A FB (s), theory A FB (s), fast MC, 2 fb –1 s = (m  ) 2 [GeV 2 ] ++ ––    Suppressed loop decay, BR ~1.2  10 –6 –Forward-backward asymmetry A FB (s) in the  rest-frame is sensitive probe of New Physics: Sensitivity (ignoring non-resonant K  evts for the time being) –7.2k signal events/2fb –1, B bb /S = 0.2 ± 0.1 –After 2 fb –1 : zero of A FB (s) located to ±0.52 GeV 2 –Other sensitive observables based on transversity angles accessible (under study)

17. Malcolm John 17/17 Conclusion LHCb is a spectrometer experiment at the LHC which instruments the forward region of the LHC hadron collision The final assembly and commissioning is on schedule: ready to take calibration and alignment data this autumn LHCb has a rich physics program and most analyses expect good results in the early period (<2fb  1 ): –Observation of B s →  –  (  ) LHCb  5 degrees –  (  s ) LHCb  0.02 radians –Sensitivity to New Physics phase in B s →  In addition, –  (  m s )  0.012ps –1 –  (sin(2  ))  0.02 (2x10 5 /2fb –1 ) [final B-factory result: σ( sin(2  ) )  ± 0.017 stat ] –  (  )  10 degrees –A CP (K *  ) measured at % level (A CP < 1% in SM) –Charm physics: D 0 mixing (expect ~ 45k D0 candidates in final fit sample… 5x B-factories’ combined yield) direct CPV in D 0  K + K – D 0  +  – and I’m sure I’ve under-represented someone…`

18. Malcolm John 18/17 Supplementary Slides  V ub V tb V cd V cb * * (0,0) (,)(,)   V ud V td V cd V cb * *  (1 -   ,   ) 2 V us V ts V cd V cb * *

19. Malcolm John 19/17 b b s s u u t =0 Time-dependent analysis requires B flavour tagging We need to know the flavour of the B at a reference t=0 (at the primary vertex) Tag (give best estimate of) the flavour by examining the rest of the event Bs0Bs0 PV  z/  c =  t rec  t picoseconds after leaving the primary vertex, the reconstructed B decays. K+K+ l  (e +,   ) l  (e ,   ) K  Uses flavour conservation in the hadronization around the B rec  D 2  1% (B 0 ), 3% (B s ) Same-side tag Assume: Opposite side tag  D 2  5% b-hadron

20. Malcolm John 20/17 RICH systems Particle ID: p~1-100 GeV provided by 2 RICH detectors Slide by Val Gibson Aerogel 22 tiles RICH2

21. Malcolm John 21/17 Only ~1% of inelastic collisions produces b-quarks. Branching fractions of interesting B decays are <10 -4 Properties of minimum bias events ate similar to those containing B decays First Level Trigger (L0) –Hardware (custom boards, 4  s latency) –Largest E T hadron, e(  ) and (di-)  –Pile-up system (not for  trigger) –Reduces 10 MHz inelastic rate to 1MHz High Level Triggers –Software trigger run on CPU farm (1800 nodes) –Access to all detector data –Full event reconstruction; inclusive and exclusive selections tuned to specific final states –Output rate 2 kHz, 35 kB per event A successful trigger is crucial in LHCb Output rateTrigger TypePhysics Use 200 HzExclusive B candidatesSpecific final states 600 HzHigh Mass di-muons J/ , b  J/  X 300 HzD* CandidatesCharm, calibrations 900 Hz Inclusive b (e.g. b  ) B data mining Slide by Olivier Schneider

22. Malcolm John 22/17 VELO TT T1 T2 T3 RICH2 RICH1 Magnet PYTHIA+GEANT full simulation Expected tracking performance High multiplicity environment: –In a bb event, ~30 charged particles traverse the whole spectrometer Track finding: –efficiency > 95% for long tracks from B decays (~ 4% ghosts for p T > 0.5 GeV/c) –K S  +  – reconstruction 75% efficient for decay in the VELO, lower otherwise Average B-decay track resolutions: –Impact parameter: ~30  m –Momentum: ~0.4% Typical B resolutions: –Proper time: ~40 fs (essential for B s physics) –Mass: 8–18 MeV/c 2 Mass resolution B s   18 MeV/c 2 Bs Ds Bs Ds  14 MeV/c 2 B s  J/   16 MeV/c 2 B s  J/   8 MeV/c 2 * with J/  mass constraint * Slide by Olivier Schneider

23. Malcolm John 23/17 Particle ID performance Average efficiency: –K id = 88% –  mis-id = 3% Good K/  separation in 2–100 GeV/c range –Low momentum kaon tagging –High momentum clean separation of the different B d,s  hh modes will be best performance ever achieved at a hadron collider  invariant massK  invariant mass With PID  invariant mass No PID Slide by Olivier Schneider

24. Malcolm John 24/17 (0,0) (0,1) (1- 2 /2)( ,  ) V ub V ud * V td V tb * V cd V cb *    (0,0) (,)(,) V ub V tb V cd V cb * * V ud V td V cd V cb * *    (1 -   ,   ) 2 V us V ts V cd V cb * * Major LHCb goals :Weak phase,,  Bs mixing phase  s =  2  2arg(Vts)  At LHCb terms up to 5 must be considered