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FRONTIERS OF MATTER XI th RENCONTRES DE BLOIS
Chateau de Blois, France June 27 - July 3, 1999 A Next Generation B-physics CP Violation Experiment The Expected Physics Performance Paul Colrain (CERN)
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History and Future August : Letter of Intent for a new collider mode b experiment at the LHC to exploit the b physics potential (30 institutes, 171 collaborators) February : Technical Proposal (42 institutes, 336 collaborators) September : Approval : Technical Design Reports : Production and Installation ? : Data Taking From day 1 of LHC Operation for many years
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The Collaboration 49 institutes
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The Physics : What is the origin of CP Violation?
The CKM Unitarity Triangles in 2005 (~108 bb): Vtd Vtb + Vcd Vcb + Vud Vub = 0 Vtd Vud + Vts Vus + Vtb Vub = 0 Bd , , D* |Vub| xs Bs Ds xs |Vub| BD* BDK*, BsDsK Bd J/ Ks Bs J/ sin2 measured to 0.05 by BaBar, Belle, HERA-B, CDF, D0 sin2 measured by BaBar, Belle (+CDF, D0 ?) with low statistics and and potentially serious theoretical uncertainties sin(2+) measured by BaBar and Belle not measured No direct measurement xs measured by CDF, D0 (if xs 40) |Vub| measured but with large hadronic error
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The Physics (Continued)
CP Violation in 2005 : Either Standard Model is “Alive” ! 1st Generation and Mixing measurements and Kaon results are Consistent (within error) with SM interpretation of CKM matrix Or Standard Model is “Dead” ! and Mixing measurements and Kaon results are Inconsistent with SM New Physics ! Either Way What is the Origin of CP Violation ? CKM matrix must be Over-Constrained : With Higher Statistics measure the same parameters (, , 2+) using the same channels Cross-check the same parameters using New Channels (BR 10-7) Measure New Parameters (, ) Study the Bs Sector Next Generation CP Violation Experiment at LHC
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The Physics (Continued)
LHC provides High statistics, L 2 1032 cm-2s-1, bb 500 b Nbb 1012/year and All species of B hadrons, including Bs LHCb is designed specifically to exploit this b physics potential : Efficient Trigger Particle Identification(e,,,K,p) - High pt hadron trigger - High pt lepton trigger - Secondary vertex trigger - Background Suppression (/K separation) - Flavour Tagging (, e, K) Good Mass Resolution Good Proper Time Resolution - Background Suppresion - Background Suppresion - CP Asymmetry in Bs
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The Detector Single Arm Spectrometer : 15 mrad < < 300 mrad
Beam-pipe, radiation Cost v Statistics b and b produced predominantly at low good acceptance (~40%) for both b and b Essential for tagging Forward geometry low threshold on trigger pt cuts efficient trigger
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The Vertex Detector 17 Silicon Strip (r,) Detectors
inside the Beam Pipe at 1cm from the beam during physics Retractable by 3cm during injection Provides excellent vertex and proper time resolution : Primary Vertex resolution = 40 m (along beam axis) Proper time resolution = 40 fs
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The RICH Detectors RICH 1 RICH 2 Pattern Recognition in RICH 1
Photodetectors Pattern Recognition in RICH 1 red dots are detected photo-electrons black circles are reconstructed rings RICH RICH 2 upstream downstream 1 < p < 70 GeV/c 20 < p < 150 GeV/c Small circles C4F10 Large circles Aerogel
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Particle Identification with RICH
-K separation > 3 for 1 < p < 150 GeV/c Suppression of same topology backgrounds Flavour tagging (b c K) Example : B +- ()
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The Detector (Continued)
Tracking System (11 stations) Inner tracker : Micro Strip Gas Chambers (MSGC) and (40cm60cm) p/p = 0.3% for Gaseous Electron Multipliers (GEM) Outer Tracker : Straw Tube Drift Chambers 5<p<200GeV/c Magnet : Warm Dipole, 4 Tm Field Integral Calorimetry Pre-Shower : Single Pb layer and Scintillators ECAL : “shashlik”, 25 X0 (E)/E = 0.1/E 0.015 HCAL : Fe and Scintillating Tiles, 5.6 (E)/E = 0.8/E 0.05 Muon System Cathode Pad Chambers (CPC) in high rate regions and either Resistive Plate Chambers (RPC) or Wire Pad/Strip Chambers (WPC) in low rate regions Calorimetry and Muon System = 22
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The Trigger Challenge : incl/bb 160, input rate = 40 MHz, output rate = 200 Hz Efficient : High pt leptons and hadrons at L0 Flexible : Multilevel with different ingredients Robust : Evenly spread data reduction at each level Level Description Detectors Data rates Latency high pt muon (~20%) Muon Chambers high pt electron (~10%) ECAL high pt hadron (~60%) ECAL+HCAL high pt photon ECAL pile-up veto Dedicated Si disks MHz 1 MHz s identification of secondary vertices Vertex Detector MHz 40 kHz s refined secondary vertices Vertex Detector + (SW) Tracker kHz 5 kHz ms reconstruction of specific decay modes (SW) All Detectors kHz 200 Hz ms 25% b purity
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The Trigger (Continued)
Trigger efficiencies (%, for reconstructed and tagged events) : L L L2 Total e h all BdJ/(ee)KS + tag BdJ/()KS + tag BsDsK + tag BdDK Bd + tag Lepton trigger Hadron Trigger Trigger Efficiency ~30% The Flavour Tag Uses the decay products from the accompanying b-hadron b e or and b c K (Jet Charge Tag not yet studied) Overall efficiency(K-tag dominant) = 40%, mistag rate = 30%
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Direct Measurement of
Extract from the relative rates of : (K* tags the flavour of the parent Bd) Bd D0 K*0 events hadron trigger -K separation Visible BRs ~ Performance (1 year) : m= 13 MeV/c2 No of events 350 (50) D0K*0 (D0K*0) S/B 1 () 10
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Measurement of -2 Extract -2 from the 4 BsDsK time-dependent decay rates Indirect measurement of ( from BsJ/) Visible BR ~ 10-6 BsDs background Bs oscillations Hadron trigger -K separation good proper time resolution t Performance (1 year) : No of events 2500 S/B 10 (-2) 6-13 Precision depends on , xs and strong Negligible theory error(no penguins) 1/Nyears
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Measurement of Extract from time-dependant CP Asymmetry in Bs J/ Counterpart of BdJ/ Ks In SM ~ 10-2 good place to look for new physics J/ is a mixture of CP-even and CP-odd states dilution of CP Asymmetry need angular analysis to separate contributions bb efficient trigger good proper time resolution, t Visible BR ~ 10-5 Bs oscillations Performance (1 year) : () 0.6 SM sensitivity in 1 year
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LHCb CP Sensitivities in 1 year
bb and trigger LHCb CP Sensitivities in 1 year Parameter Channels No of events (1 year) LHCb feature Bd + c.c (2+ = +-) |P/T| = -5 -K sep. |P/T|=0.20 ?? -K sep. Bd D* -K sep. BdJ/Ks -2 Bs DsK -13 -K sep., t Bd DK* -K sep. Bs J/ t Bs oscillations xs Bs Ds upto t Rare Decays Br Bs <2 t No Bd K* photon trigger
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Summary LHCb is a 2nd Generation CP Violation Experiment :
Massive Statistics ~1012 bb events per year (Bd, Bs, b baryons,...) trigger efficient in all modes (hadron trigger) Particle Identification negligible background systematics in CP measurements efficient flavour tag (Kaon) Excellent proper time resolution (t ~ 40 fs) Precision measurements in Bs system LHCb offers a unique opportunity to improve our understanding of the origin of CP Violation either within the framework of the SM or Beyond !
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