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

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

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

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 h s cl>5% cl>32% cl>90% From Perez 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

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

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

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

The Forward Direction at LHC 100 mb 230 mb Pythia production cross section 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

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

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

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” pT m, di-muons, e, g & hadrons, e.g. pT m >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

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

Trigger Output Output rate Trigger Type Physics Use 200 Hz Exclusive B candidates Specific final states 600 Hz High Mass di-muons J/, bJ/X 300 Hz D* Candidates Charm, calibrations 900 Hz Inclusive b (e.g. bm) B data mining 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

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

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

Flavor Tagging Method (For BS) m± e± K± same K± opp 1.5 0.7 3.1 2.5 “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” Method (For BS) m± e± K± same K± opp Jet charge eD2(%) 1.5 0.7 3.1 2.5 0.8 eD2 (%) Not exactly same cuts as table Expect eD2 ~ 7.5% for BS & 4.3% for Bd Aspen Winter Conference, February, 2006

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

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 CDF data Bd signal Excellent mass resolution s=14 MeV Aspen Winter Conference, February, 2006

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

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

CP Asymmetry in BSJ/ f Just as BoJ/ KS measures CPV phase b BS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

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 Resolved 0 Merged 0 Aspen Winter Conference, February, 2006

Other Physics Sensitivities Afb Zero to ±0.04 GeV2 Only a subset of modes For ~2 years of running Aspen Winter Conference, February, 2006

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

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

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

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

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

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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