Efficient Triggering with the LHCb Detector as long as Precise CP Measurements LHCb det
Dempsey, Courtney, Features Reporter has reference to this Academic Journal, PHwiki organized this Journal Efficient Triggering with the LHCb Detector as long as Precise CP Measurements LHCb detector Changes in geometry since Technical Proposal (98) Technical Design Report Sep 2003 Trigger Technical Design Report Sep 2003 Physics per as long as mance 8th International Conference on Advanced Technology in addition to Particle Physics 6 October 2003 Como, Italy Niels Tuning (CERN) on behalf of the LHCb collaboration LHCb A Large Hadron Collider Beauty Experiment as long as Precision Measurements of CP-Violation in addition to Rare Decays Measure B-decays: CP violation in St in addition to ard Model New particles in loop diagrams Additional CP violation! Branching fraction of rare decays Colliding beams: 7 TeV x 7 TeV pp (every 25 ns) L = 2.1032 cm-2 s-1 (visible) = 68 mb (ppbbX) = 0.5 mb ~1012 bb / year BR(interesting ch.) ~10-4 10-9 The LHCb detector VELO: primary vertex impact parameter displaced vertex Trigger Tracker: p as long as trigger Tracking Stations: p of charged particles Calorimeters: PID: e,, 0 Trigger on hadr. Muon System RICH: PID: K, separation
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Detectors in the Trigger Trigger Tracker: Full Si tracker 4 layers (x,u [30 cm gap] v,x) Wide pitch: 200 m 180k channels Placed in front of magnet VELO 21 stations, 100cm Vertex Locator: 220 m n-on-n Si Pitch: 40-100 m R- geometry 170k channels Pileup System 2 VELO disks sensor: stereo angle +10o,-20o R sensor: 4 sectors 16 mm 84 mm Trigger Overview L0: high PT Calorimeter+Muon Fully synchronous on custom boards L1: high PT + impact parameter VELO+TT Max. latency 52.4 ms (L1 buffer size: 58254 events) Software trigger HLT: high PT + displaced vertex + B-mass Full detector in as long as mation available 1 MHz 40 kHz 40 MHz L0 (4 s) L1 (~1 ms) HLT (~14 ms) L0: pileup system Calculate vertex as long as all combinations of 2 points a in addition to b. Find highest peak (= prim.vtx) Remove the hits in addition to find 2nd peak Veto if peak>threshold (Zvtx) 2.8 mm, (beam) 53 mm
L0 High-pT , e, in addition to hadrons with Calorimeter in addition to Muon system Muons: Fraction of events L1: 1 MHz 40 kHz 2d tracks in VELO ~80 / event Vertex z = 60 m High imp.par 3d tracks pT in as long as mation L0: muons TT: dp/p = 30% J/(+-) 45o slice L1 HLT pT in as long as mation from TT dp/p = 30% 2 high-IP tracks with highest pT: pT in as long as mation from T dp/p = 0.6% Confirm L1 decision: down to 20kHz 95% efficiency In only 4 ms 14 ms as long as the rest L1+HLT implemented on same CPU farm: ~1000 CPUs as long as L1, ~800 as long as HLT+reconstruction HLT runs in the background to limit deadtime.
Trigger per as long as mance Good efficiencies as long as useful events: L0: 50 90% L1: 50 70% Timing is OK: 2007: L0: 3.5 s (4 s) L1: 8 ms (1 ms, max. 50 ms) What do we do with the triggered events CP violation Mixing Small in B0 system, 1-p/q~10-3 BH0~ pB0>+qB0> LHCb: B0sDs-+, B0D-+. Decay Interference between diagrams with same final states (e.g. tree, penguin) e.g. (B+f+)-(B-f -) (NB: no mixing) Interference between (B0f) in addition to (B0B0 f) f=fCP: LHCb: B0J/KS, B0sJ/, B0. ffCP: LHCb: B0sDSK , B0D, B0D0K. Present status: sin(2)=0.731 0.055 (BJ/KS from e+e-) sin(2)=0.695 0.055 (from md in addition to Vub) = 64.5o 7o (combining all measurements) Measuring CKM angle in LHCb: B0sD+/-sK-/+ Only tree diagrams: theoretically clean. B0-+, B0sK-K+ Penguin contributions solved with SU(3) symm. B0D0K0,D0K0 Sensitive to new physics in D0,D0 mixing
Rare decays Branching ratios of rare decays might be enhanced by the presence of new particles in the loop BR ~10-5: (~104 selected events/year) B0K0 B0 BR ~10-6: (~103 sel. events/year) B0+- K0 BR ~10-9: (~101 sel. events/year) B0s+- Event selection Variables: pT, impact parameter, PID. Decay length, vertex, mass constraints. B-mass, pointing. B0sD-sK+ . B0sD-s+ Yields Efficiencies: Acceptance x Reconstruction x Selection x Trigger 10% x 80% x 20% x 35% ~ 0.5% Branching ratios: ~ 10-5 Yields: 1012 bb x 0.005 x 10-5 ~ 50k Typically
CP measurement Examples: ACP(B0J/KS) = ACP( B0sD+sK-) = Extract CP parameters from fast simulation Given the resolutions, yields in addition to background from full simulation f = LHCb physics reach in 1 year Excellent sensitivity Twice current BABAR+BELLE sensitivity Various measurements to disentangle new physics Rare decay (B0K0) 2% higher than SM 3 significance Conclusions The LHCb trigger: reduces the rate from 40 MHz to 200 Hz (5.10-6 !), with high efficiencies (~20-70%), in addition to within the tight time budgets. Precise measurements of CKM parameters: with many different approaches, to disentangle new physics. Precise measurements of branching ratios: where new physics could show up.
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