Efficient Triggering with the LHCb Detector for Precise CP Measurements 8th International Conference on Advanced Technology and Particle Physics 6 October 2003 Como, Italy LHCb detector Changes in geometry since Technical Proposal (’98) Technical Design Report Sep 2003 Trigger Physics performance Niels Tuning (CERN) on behalf of the LHCb collaboration 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning LHCb A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays Measure B-decays: CP violation in Standard 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 (ppbbX) = 0.5 mb  ~1012 bb / year BR(interesting ch.) ~10-4 – 10-9 cern LHCb p 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning The LHCb detector RICH: PID: K, separation Trigger Tracker: p for trigger Tracking Stations: p of charged particles Calorimeters: PID: e,, 0 Trigger on hadr. VELO: primary vertex impact parameter displaced vertex Muon System 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

Detectors in the Trigger Vertex Locator: 220 m n-on-n Si Pitch: 40-100 m R- geometry 170k channels Pileup System 2 VELO disks VELO 16 mm 84 mm 21 stations, 100cm  sensor: stereo angle +10o,-20o R sensor: 4  sectors Trigger Tracker (TT) 20 ladders, 140cm 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 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning Trigger Overview Bunch crossing rate 40 MHz Non empty bunch x-rate 30 MHz Visible interaction rate ~12 MHz Output of L0 1 MHz 40 MHz L0 (4 s) 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 information available 1 MHz L1 (~1 ms) 40 kHz HLT (~14 ms) 200 Hz 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning L0: pileup system Calculate vertex for all combinations of 2 points a and b. Find highest peak (= prim.vtx) Remove the hits and find 2nd peak Veto if peak>threshold (Zvtx)  2.8 mm, (beam)  53 mm 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning L0 High-pT , e,  and hadrons with Calorimeter and Muon system Muons: Hadrons: Efficiency Fraction of events 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning L1: 1 MHz  40 kHz 45o slice 2d tracks in VELO ~80 / event Vertex z = 60 m High imp.par 3d tracks pT information L0: muons TT: dp/p = 30% J/(+-) 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning L1 HLT pT information from TT dp/p = 30% 2 high-IP tracks with highest pT: pT information from T dp/p = 0.6% Confirm L1 decision: down to 20kHz 95% efficiency In only 4 ms 14 ms for the rest ln pT ln IP/IP L1+HLT implemented on same CPU farm: ~1000 CPUs for L1, ~800 for HLT+reconstruction HLT runs in the background to limit deadtime. 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning Trigger performance Good efficiencies for 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) 8 ms (1 GHz PIII) 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

What do we do with the triggered events? 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning CP violation Mixing Small in B0 system, 1-|p/q|~10-3 BH0~ p|B0>+q|B0> LHCb: B0sDs-+, B0D-+. Decay Interference between diagrams with same final states (e.g. tree, penguin) e.g. (B+f+)-(B-f -) (NB: no mixing) Interference between (B0f) and (B0B0 f) f=fCP: LHCb: B0J/KS, B0sJ/, B0. ffCP: LHCb: B0sDSK , B0D*, B0D0K*. Present status: sin(2)=0.731  0.055 (BJ/KS from e+e-) sin(2)=0.695  0.055 (from md and |Vub|)  = 64.5o 7o (combining all measurements) Measuring CKM angle  in LHCb: B0sD+/-sK-/+ Only tree diagrams: theoretically clean. B0-+, B0sK-K+ Penguin contributions solved with SU(3) symm. B0D0K*0,D0K*0 Sensitive to new physics in D0,D0 mixing 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning 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) B0K*0 B0 BR ~10-6: (~103 sel. events/year) B0+- K*0 BR ~10-9: (~101 sel. events/year) B0s+- bs penguin 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning Event selection . B0sD-sK+ . B0sD-s+ Variables: pT, impact parameter, PID. Decay length, vertex, mass constraints. B-mass, pointing. 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning 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” 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning CP measurement (B0 -B0)/(B0+B0) (1 year of B0J/KS) sinmdt sin2 Extract CP parameters from fast simulation Given the resolutions, yields and background from full simulation Examples: ACP(B0J/KS) = ACP( B0sD+sK-) = (B0s -B0s)/(B0s+B0s) B proper lifetime (ps)  (5 years of B0sD-sK+) f = 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

LHCb physics reach in 1 year Excellent  sensitivity Twice current BABAR+BELLE sensitivity Various  measurements to disentangle new physics Rare decay (B0K*0) 2% higher than SM?  3 significance 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning

8th ICATPP Conference, Como, N.Tuning Conclusions The LHCb trigger: reduces the rate from 40 MHz to 200 Hz (5.10-6 !), with high efficiencies (~20-70%), and 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. 6 Oct 2003 8th ICATPP Conference, Como, N.Tuning