LHCb

1. Sheldon Stone Syracuse Univ. LHCb The Large Hadron Collider beauty Experiment & Physics

2. General Physics Justification • Expect New Physics will be seen at LHC • Standard Model is violated by the Baryon Asymmetry of Universe & by Dark Matter • Hierarchy problem (why MHiggs<<MPlanck) • However, it will be difficult to characterize this physics • How the new particles interfere virtually in the decays of b’s (& c’s) with W’s & Z’s can tell us a great deal about their nature, especially their phases Aspen Winter Conference, February, 2006

3. Contributions to direct CP violating decay B-fK- Asym=(MW/msquark)2sin(fm), ~0 in SM Example • MSSM from Hinchcliff & Kersting (hep-ph/0003090) • Contributions to Bs mixing BsJ/yh CP asymmetry  0.1sinfmcosfAsin(Dmst), ~10 x SM Aspen Winter Conference, February, 2006

4. cl>90% cl>5% cl>32% s h From Perez Limits on New Physics From b’s • Is there NP in Bo-Bo mixing? • Assume NP in tree decays is negligible • Use Vub, ADK, SyK, Srr, Dmd, ASL • Fit to h, r, h, s • For New Physics via Bdo mixing, h is limited to ~<0.3 of SM except when sBd is ~0o or ~180o of SM decays • New physics via Bs mixing, or bs transitions is unconstrained Aspen Winter Conference, February, 2006

5. Most Currently Desirable Modes • BS mixing using BSDS+p- • High Statistics Measurement of forward-backward asymmetry in B K*m+m- • Precision measurements of CP ’s • CP violating phase in BS mixing using BSJ/yf • g (or f3) Using B- DoK- tree level decays • g using BSDS+K- time dependent analysis • a especially measurement of Bo roro • b at high accuracy to pin down other physics • CPV in various rare decay modes • B(S) m+m- • Important: Other modes, not currently in vogue Aspen Winter Conference, February, 2006

6. Detector Requirements - General • Every modern heavy quark experiment needs: • Vertexing: to measure decay points and reduce backgrounds, especially at hadron colliders • Particle Identification: to eliminate insidious backgrounds from one mode to another where kinematical separation is not sufficient • Muon & electron identification because of the importance of semileptonic & leptonic final states including J/y decay • g, po & h detection • Triggering, especially at hadronic colliders • High speed DAQ coupled to large computing for data processing • An accelerator capable of producing a large rate of b & anti-b hadrons in the detector solid angle Aspen Winter Conference, February, 2006

7. Basics For Sensitivities • # of b’s into detector acceptance • Triggering • Flavor tagging • Background reduction • Good mass resolution • Good decay time resolution • Particle Identification Aspen Winter Conference, February, 2006

8. Pythia production cross section 100 mb 230 mb The Forward Direction at LHC • In the forward region at LHC the bb production s is large • The hadrons containing the b & b quarks are both likely to be in the acceptance • LHCb uses the forward direction, 4.9 > h >1.9, where the B’s are moving with considerable momentum ~100 GeV, thus minimizing multiple scattering • At L=2x1032/cm2-s, we get 1012 B hadrons in 107 sec pT h Production  Of B vs B q B (rad) q B (rad) Aspen Winter Conference, February, 2006

9. The LHCb Detector Muon Detector Tracking stations proton beam interaction region Trigger Tracking Aspen Winter Conference, February, 2006

10. Geometry R sensor: 38 mm pitch inside to 103 mm outside f sensor: 39 mm pitch inside to 98 mm outside 1 m  R sensors f sensors 3 cm separation Interaction point The VELO Sensor Half Vacuum Tank Aspen Winter Conference, February, 2006

11. Triggering • Necessary because b fraction is only ~1% of inelastic cross-section • At peak luminosity interaction rate is ~10 MHz, need to reduce to a few kHz. The B hadron rate into the acceptance is 50 kHz • General Strategy • Multilevel scheme: 1st level Hardware trigger on “moderate” pTm, di-muons, e, g & hadrons, e.g. pTm >1.3 GeV/c; veto on multiple interactions in a crossing except for muon triggers. • Uses custom electronics boards with 4 ms latency, all detectors read out at 1 MHz • Second level and Higher Level software triggers Aspen Winter Conference, February, 2006

12. Software Triggers • Second Level: All detector information available. Basic strategy is to use VELO information to find tracks from b decays that miss the main production vertex; also events with two good muons are accepted & single muon with pT > 2.1 GeV/c. Strategies are constantly being improved. • Higher Level Triggers: Here more sophisticated algorithms are applied. Both inclusive selections and exclusive selections tuned to specific final states done after full event reconstruction has finished. Output rate is ~2 kHz Aspen Winter Conference, February, 2006

13. Trigger Output • Rough guess at present (split between streams still to be determined) • Large inclusive streams to be used to control calibration and systematics (trigger, tracking, PID, tagging) Aspen Winter Conference, February, 2006

14. Trigger Monitoring • Trigger lines need constant monitoring to adjust prescales, especially at beginning of experiment. • General approach: for a particular trigger • Define TOSTrigger On Signal • Define TIS Trigger Independent of Signal • Efficiency =(TISTOS )/TIS Aspen Winter Conference, February, 2006

15. Trigger Monitoring Example • Comparison of L0 trigger efficiency on muon tracks that miss the IP as a function of Pt for both “traditional” Monte Carlo method & (TISTOS )/TIS • Can be done quickly with real data TIS & TOS Method Traditional MC Aspen Winter Conference, February, 2006

16. Flavor Tagging “opposite side” • For Mixing & CP measurements it is crucial to know the b-flavor at t=0. This can be done by detecting the flavor of the other B hadron (opposite side) or by using K± (for BS) p± (for Bd) (same side) • Efficacy characterized by eD2, where e is the efficiency and D the dilution = (1-2w) • Several ways to do this “same side” eD2 (%) Not exactly same cuts as table Expect eD2 ~ 7.5% for BS & 4.3% for Bd Aspen Winter Conference, February, 2006

17. Background Reduction Using st • Excellent time resolution ~40 fs for most modes based on VELO simulation • Example BS mixing Bs→Ds-π+ 100 mm Bs→Ds-π+(tagged as Bs) 10 mm LHCb can measure DmS up 68 ps-1 in 2 fb-1 Aspen Winter Conference, February, 2006

18. CDF data Bd signal Background Reduction from Particle ID • LHCb has two RICH detectors. Most tracks in range 100>P>2 GeV/c. Tagging kaons at lower momentum < 20 GeV/c; Bh+h- up to 200 GeV/c, but most below 100 GeV/c • Good Efficiencies with small fake rates Excellent mass resolution s=14 MeV Aspen Winter Conference, February, 2006

19. 80 mm The RICH Detectors HPD Photon Detectors RICH I Design Aspen Winter Conference, February, 2006

20. RICH II RICH2 –installed in the pit Aspen Winter Conference, February, 2006

21. CP Asymmetry in BSJ/ f • Just as BoJ/ KS measuresCPV phase bBSJ/ f measures CPV BS mixing phase fS • Since this is a Vector-Vector final state, must do an angular (transversity) analysis • The width difference DGS/GS also enters in the fit • LHCb will get 120,000 such events in 2fb-1. Projected errors are ±0.06 in fS & 0.02 in DGS/GS (for DmS = 20 ps-1) • Including BSJ/ h, will increase sensitivity (only 7K events) Aspen Winter Conference, February, 2006

22. Merged 0 Resolved 0 Neutral Reconstruction • Mass resolution is a useful s=~6 MeV • Efficiency within solid angle is OK using both merged and resolved po’s • Example: time dependent Dalitz Plot analysis ala’ Snyder & Quinn for Borp p+p-po • 14K signal events in 107 s with S/B 1/3, yielding s(a)=10o Aspen Winter Conference, February, 2006

23. Other Physics Sensitivities • Only a subset of modes • For ~1 year of running Zero to ±0.04 GeV2 Afb Aspen Winter Conference, February, 2006

24. Status • Magnet installed & mapped • ECAL, HCAL, RICH II & Muon Filter Installed • Construction on all other items proceeding • Software is progressing • New MC-data challenges using Grid Aspen Winter Conference, February, 2006

25. Overview Overall in very good shape for startup in 2007 Aspen Winter Conference, February, 2006

26. Muon system -iron shielding -electronics tower Calorimeter-E-cal, H-cal modules RICH2 Magnet RICH1 -HPD shielding box OT: straw module production completedMuon: more than half of chambers produced View of Pit Aspen Winter Conference, February, 2006

27. Bop+p- BSfg BSJ/yf BSDSK- Possible Improvements • Run at higher luminosity. Increase to 5x1032 /cm2-s • Gains in event yields, especially dimuon modes Aspen Winter Conference, February, 2006

28. Possible Upgrades • VELO needs to be replaced after ~6-8 fb-1 due to radiation damage • Are considering hybrid Silicon pixels as a replacement • Since they are much more rad hard than current VELO, we could move closer to the beam getting better vertex s • These could possibly allow some vertexing in first trigger level with minor modifications • EM calorimeter upgrades such as having a central PbWO4 region • Major modifications to readout including long digital pipelines that would enable extensive 1st level vertex triggering and allow higher luminosity running (very expensive) Aspen Winter Conference, February, 2006

29. Conclusions • LHCb will study CP Violation and Rare Decays in the BS, B-, & Bd systems at an unprecedented level of accuracy • These studies are crucial for specifying any new physics found directly at the Tevatron or LHC • LHCb is on schedule • LHCb is starting to think about upgrades From Hewett & Hitlin Aspen Winter Conference, February, 2006

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