Transcript Slide 1
LHCb Status and Prospects Doris Eckstein (CERN) on behalf of the LHCb Collaboration 3rd International Conference on Flavor Physics Chungli, Taiwan, 3-8 October 2005 1. 2. 3. Introduction Status and Performance of Detector Physics Prospects - Examples Introduction •LHCb experiment to study CP violation in B-hadron decays •LHC: pp-collisions @ 14TeV full spectrum of B-hadrons produced B-cross-section large ~500mb •Pile-up at high luminosity: choose 2x1032 cm-2 s-1 Interactions/crossing most events have single interactions •1012 b-hadrons per nominal year of data taking (2 fb-1) bb correlated Lorentz boost LHCb: forward spectrometer 15-250mrad acceptance 8 October 2005 Doris Eckstein, ICFP2005 2 Introduction cont’d LHCb: study CP violation look for New Physics rare B decays Need: efficient trigger on leptons and hadrons efficient particle ID for flavour tagging and background rejection good proper time resolution for time dependent measurements of Bs decays good B mass reconstruction for background rejection 8 October 2005 Doris Eckstein, ICFP2005 3 Introduction - LHCb detector Vertex Reconstruction VELO p 8 October 2005 Tracking system VELO Trigger Tracker Inner/Outer Tracker Particle ID RICH1 and RICH2 Calorimeters Muon system Kinematics Magnet + Trackers Calorimeters 10 mrad p Doris Eckstein, ICFP2005 4 Detector Status - VELO Interaction region ~1m Silicon microstrip sensors 42 modules around interaction region R-F geometry Strip pitch varies from 40mm to 100mm Sensors close to beam (8 mm) Beetle FE chip VELO hybrid Module production starting 8 October 2005 Doris Eckstein, ICFP2005 5 Detector Status - VELO Ensure high resolution short extrapolation distance small multiple scattering Sensors are at 8 mm from beam Sensors in secondary vacuum Roman Pots Mechanics to allow for retraction Vacuum Vessel and stand manufactured. Mechanics to move VELO ready. 8 October 2005 Doris Eckstein, ICFP2005 6 Detector Performance - Vertexing Impact parameter resolution dIP = 14mm+35mm/pT • • proper time t=lm/p Proper time resolution is dominated by B vertex resolution Bs→Dsp •Impact parameter resolution crucial for proper time resolution • ~40 fs for most channels 8 October 2005 Doris Eckstein, ICFP2005 7 Detector Status - Magnet • • • ∫Bdl = 4 Tm Warm dipole magnet (Al), Fe yoke = 1600 t Regularly reverse field to control systematics •Installed in 2004 •Field mapping ongoing 8 October 2005 Doris Eckstein, ICFP2005 8 Outer Tracker cm Detector Status – Tracker T1, T2, T3 made of Outer Tracker and Inner Tracker Inner Tracker for Region of high occupancy cm Trigger Tracker Production started •Measurement in fringe field of magnet •Covers full detector acceptance Provide pt for Trigger (together with VELO) 2*2 layers Silicon microstrip sensors 500mm thickness ~200mm readout pitch 8 October 2005 Doris Eckstein, ICFP2005 9 Detector Status – Tracker Inner Tracker: •only 2% of area, but 20% of tracks Silicon microstrip sensors •11 cm strips, ~200mm pitch Tracking behind the Magnet – IT and OT Outer Tracker: •3 stations •each made up of 4 double-layers of Kapton/Al straw tubes •glued together to form modules two-sensor ladders: 410 mm thickness Single sensors: 320 mm thickness Modules in production 8 October 2005 Module production close to completion Doris Eckstein, ICFP2005 10 Detector Performance – Tracking •tracks passing through full spectrometer: e ~ 95%, a few percent of ghost tracks •Momentum resolution Dp/p ~ 0.4% VELO TT red = detected hits blue = reconstructed tracks T1 T2 T3 Mass resolution BsDsp+ Typical sm~15 MeV 8 October 2005 Doris Eckstein, ICFP2005 11 Detector Status – RICHes For hadron ID Efficient p/K separation up to 100 GeV Aerogel C4F10 gas CF4 gas RICH2: High momentum tracks •CF4: 16 - ~100 GeV RICH1: Low momentum tracks •Aerogel: 2 - ~10 GeV •C4F10: 10 - ~60 GeV 8 October 2005 5cm Aerogel n=1.030 Doris Eckstein, ICFP2005 12 Detector Status – RICHes •Novel photon detectors: Hybrid Photon Detectors Si pixel detectors encapsulated in photo-tube • ~ 500 tubes, each with ~1000 pixels •Production underway HPD tubes RICH2 ready for transportation HPDs in production Outside RICH1 in production RICH2 Spherical mirrors aligned to 50mrad 8 October 2005 Doris Eckstein, ICFP2005 13 Detector Status – Calorimeters •Scintillating Pad Detector/PreShower 2.5 X0 Pb between 2 Scintillator planes size corresponds to size of ECAL pads in production SPD/PS •Hadronic Calorimeter (HCAL) Fe/Scintillator tile calorimeter, 5.6 lI Granularity varies transversally 13x13 and 26x26cm HCAL ECAL HCAL 8 October 2005 installed, commissioning starts Doris Eckstein, ICFP2005 14 Detector Status – Calorimeters Electromagnetic Calorimeter (ECAL) Pb-Scintillator Shashlik, 25 X0 granularity varies transversally from 1 to 3 Rm sE/E = 10% /E 1% resolution from testbeam installed Comissioning started 8 October 2005 Doris Eckstein, ICFP2005 15 Detector Status – Muon System MWPC’s Triple-GEM in inner part of M1 (highest rate region) Projective pad geometry (used in Trigger) Muon-Identification Efficiency ~95% for <1% pion misidentification calorimeters 8 October 2005 MWPC’s in production GEM production will start soon Doris Eckstein, ICFP2005 16 Detector Performance – Particle ID K/p separation by RICH Pion id efficiency ~97% Pion misid ~3% Kaon id efficiency ~88% Kaon misid ~12% Signal Background Large rings: aerogel Small rings: C4F10 Lepton ID by Calorimeters and Muon System: <e(mm)> = 94% <e (p m)> = 1% <e(ee )> = 81% <e(p e)> = 1% 8 October 2005 Doris Eckstein, ICFP2005 17 Trigger 40 MHz L0 High pt hadron, lepton, g Flag multiple interactions, busy events Hardware (custom boards), latency 4ms Calo, Muon, Pileup, SPD 1 MHz L1 Combined high pt, high IP Software (PC farm), partial event information,decision in 1ms VELO, TT 40 kHz HLT Inclusive and exclusive Software (PC farm), complete event, 10ms Full information from detector L0, L1 L0×L1 •Recent change: •Full detector information read out at 1 MHz •Zero suppressed •Combined software trigger 2 kHz On tape 8 October 2005 Doris Eckstein, ICFP2005 18 Physics Prospects – Baseline Measurements •Bs mixing (new physics effects in box diagrams) – Dms from Bs→Dsp – fs and DGs from Bs→J/yf •CKM angles from different processes to over-constrain unitary triangle sin(2b) from Bd → J/yKs Important check/comparison with B-factories g from various channels different sensitivity to new physics – g from Bs → DsK time dependent asymmetries – g from B → pp, Bs → KK time dependent asymmetries – g from B → D0K*0 decay rates a from Bd → rp •rare B decays (b → s processes, NP now yet well constrained) –Bs → mm down to SM BR –Bd → K*mm : measure forward-backward asymmetry 8 October 2005 Doris Eckstein, ICFP2005 19 Physics Prospects – Dms Decay time resolution •Bs Ds-p+ •Proper time resolution ~ 40 fs •S/B~3 •80k events/year Dms=25ps-1 1 year of LHCb data •Statistical uncertainty on amplitude of Bs oscillation as function of Dms oscillations clearly observed with 1 year of data taking! •5σ measurement in 1 year of running for Δms up to 68 ps-1 • (far beyond Standard Model expectation Δms < 26 ps-1) Once oscillations are established, determine Δms with σ(Δms) ~ 0.01ps-1 stat. 8 October 2005 Doris Eckstein, ICFP2005 20 Physics Prospects – g from Bs→DsK s c u b Bs s •Interference of tree diagrams yields phase K+ s s u Bs Ds- c b s s K+ Ds- Sensitivity after 1 year: Dms 20ps-1 25ps-1 30ps-1 s(g) 18.3 14.2 8 October 2005 16.2 of g+fs •fit four time dependant decay rates: Bs → Ds-/+ K+/Bs → Ds-/+ K+/- fs measured through Bs→J/yf •Free of new physics contributions in penguin diagrams •Measured g not affected by new physics in Bs mixing •Discrepancy with indirect g from CKM fit will signify new physics in mixing Doris Eckstein, ICFP2005 21 Physics Prospects – g from B→hh p/K p/K Bd/s • • • • p/K • Bd ->pp 25k events/year • Bs -> KK 37k events/year Bd/s p/K time dependent asymmetries for Bd→pp and Bs→KK ACP(t) = Adir cos(Dm t) + Amix sin(Dm t) Parameters: – Mixing phases fd or fs through Bd→J/yKs and Bs→J/yf – Penguin/Tree=deiq U-spin symmetry: dpp=dKK, qpp=qKK 4 observables, 3 unknowns: solve for g Dms=20ps-1, DGs/Gs=0.1, g=65o, q=160o, d=0.3, Fs=-0.04 One year: s(g) ~ 5+ uncertainty from U-spin symmetry breaking Sensitive to new physics in penguin 8 October 2005 Doris Eckstein, ICFP2005 22 Summary •The detector is designed for precise vertexing and tracking and excellent particle identification. •LHCb has a high performance trigger dedicated to B physics. •LHCb will extend the B physics results from B-factories and Tevatron due to the high statistics expected and the full spectrum of B-hadrons available. •LHCb spectrometer construction is progressing well. •Overall commissioning will start end of 2006. •We are looking forward to first data in 2007! 8 October 2005 Doris Eckstein, ICFP2005 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