Status of the LHCb Experiment. Ueli Strauman, University of Zurich, Switzerland. Sept. 13, 2001

Transcription

1 Status of the LHCb Experiment Ueli Strauman, University of Zurich, Switzerland. Sept. 13,

2 P b b P Number of pp inelastic interactions in one bunch crossing (σ inelastic = 80 mb): b b correlation A single forward arm spectrometer covers a good fraction of bb pairs. Running at a modest luminosity will enhance the single interaction events: 2 easy flavour tag, lower level of radiation, etc.

3 The LHCb detector VELO Inner Tracker Outer Tracker RICH 1 RICH 2 Calorimeters Muon system 3

4 Technical Proposal LHCb Experiment approved in September 1998 Subsystem Technical Design Reports TDR Outer Tracking Approved Approved Approved Submitted May 2001 Submitted May 2001 Submitted 4 Sep. 2001

5 Muons: Trigger and Identify larger particle flux (<200 khz/cm²): MWPC 1.5mm Anode wires Detector ground 2.5mm 2.5mm Guard trace Cathode pads small particle flux (<1 khz/cm²): Resistive Plate Chamber pick-up electrodes(s) signal q e Q d x - - Q q 0 GAS HV + - 5

6 MWPC: 4 gaps for redundancy total area 228 m² cathode pad and wire readout RPC: 2 gaps for redundancy total area 207 m² R4 Chamber R3 Chamber R1 R2 Chamber Z4 Ch. Z3 Z4 Z3 Z4 Z3 6 Z2 Z1 Z2 Z1 Z2

7 physical channels are combined to logical channels (input for trigger) 4804 Region 4 Logical channel and pad size are determined by occupancy momentum resolution (L0 trigger) 2002 Logical channel 50mm x 250mm Logical channel 4003 logical pad size varies from cm² to cm² 1001 Region 3 25mm x 125mm Logical pad 500 Region Reg 1 6.3mm x 31mm 12.5mm x 63mm Beam Pipe Sheilding

8 Efficiency as a function of rate: MWPC RPC Efficiency (%) Efficiency Sigma Rate (khz) Time Resolution (ns) Efficiency HV= 9.8 kv Irradiated chamber Reference chamber Max Rate (Hz/cm 2 )

9 Calorimeter Function Level 0 trigger high P T electron, photon, hadron electron, photon identification π 0 reconstruction Technology Scintillator (SPD) 2X0 Pb Scintillator (PS) Ecal: Shashlik a la HERA B Hcal: Fe Scintillator tile similar to ATLAS, simpler design 9

10 H cal module SPD and preshower detector E cal modules module 0 finished mass production starts Nov

11 Expected performance Electromagnetic energy (GeV): σe 0.10 E = E σe 0.80 Hadronic energy (GeV): = E E (verified by prototype tests) 11

12 RICH Required momentum range and angular coverage. 12

13 RICH1: 5cm aerogel, n = 1.03, 2 11 GeV RICH2: 100 m 3 CF 4 n = GeV 4 m 3 C 4 F 10, n = , GeV Baseline option: Pixel HPD prototype chip avail. backup: MAPMT 1024 pixel (500µm 500µm) detector and bump bonded pixel readout electronics. 13

14 RICH Performance Realistic simulation: tested by the test beam data engineering design measured HPD performance all the background photons pattern recognition (some can still improve) No. of detected photons 6,6:RICH 1 aerogel 32.7: RICH 1 C4F : RICH 2 CF4 14

15 B π + π 15

16 The Spectrometer Number of the tracking stations is being optimized (reducing X 0 and λ) TP time: 11, Now 9. Still good pattern recognition. reduce further? 16

17 Dipolmagnet: warm Al conductors gap adjusted to spectrometer acceptance 4 Tm integrated field all contracts are placed and signed B (Tesla) B y -0.4 and B z B x θ x =θ y = z (cm)

18 Outer Tracker (TDR September 2001) straw chambers split anode and wire spacer 18

19 Evolution of the beam pipe design Al pipe + Stainless steel flanges and bellows Al pipe + Al flanges and bellows Al Be alloy pipe + Al flanges and bellows (LHCb favoured solution) 19

20 outer tracking station design 20

21 Inner Tracker (high occupancy region) Shape adjusted to particle flux Silicon strips ladder length 22 cm (two six inch wafers) pitch 0.24 mm total area about 12 m²

22 Inner tracking ladder prototype: Testbeam studies (not yet final electronics): S/N sensor 3 Signal to noise for two different shaping times of the preamp strip number 22

23 VEertex LOcator (VELO) Vacuum Vessel ~1 m Number of silicon sensors: 100 Area of silicon: 0.32m2 Number of channels: 204,800 23

24 Small r φ strip Si detector: 300µm n on n double metal layer 24

25 25

26 Muon System The LHCb Trigger System Calorimeter System pile up vertex detector 40 MHz high PT muons 26 k 20 k 3.6 k high P T electrons high P T hadrons high P T photons pile up veto 1 MHz VELO ~200 k Level 0 decision unit Level 1 trigger unit 40 KHz All the detector Processor farm for Level 2 and Level 3 26

27 LHCb Trigger Efficiency for reconstructed and correctly tagged events L0(%) L1(%) L2(%) Total(%) m e h all B d J/ψ(ee)K S + tag B d J/ψ(µµ)K S + tag B s D sk + tag B d DK* B d π+ π + tag trigger efficiencies are ~ 30% hadron trigger is important for hadronic final states lepton trigger is important for final states with leptons 27

28 Summary LHCb is well under way. TDR s are being produced according to schedule LHCb will be operational at start of LHC As a second generation B experiment it will provide high precision and large statistics 28

29 Some LHCb Physics Performance CP asymmetries in B d J/ψ K S B s J/ψ φ (>40k tagged /10 7 sec) σsin2φ 1 = 0.02 /10 7 sec excellent σ t σ 2δφ = /10 7 sec (x s = 20 40) B s oscillations: hadron trigger, excellent σ t Bs Ds π measurable up to xs 80 (54 ps 1 ) with 5σ CP violation in radiative decays B d K *0 µ + µ s = 4.5k/ 10 7 sec (Br= ), s/b = 16 error on forward backward asymmetry 0.03/10 7 sec B d K *0 γ single photon trigger s = 26k/ 10 7 sec (Br= ), s/b = 1 error on CP asymmetry 0.01/10 7 sec 29

30 CP asymmetries in B d D ± π hadron trigger 260 k tagged /10 7 sec σφ 3 10 B s D s K ± particle ID, hadron trigger, excellent σ t 2.4 k tagged /10 7 sec σφ 3 10 Time dependent Dalitz plot study: hadron trigger Bs π + π π 0 σφ 1 +φ 3 5 to 10 /10 7 sec CP asymmetries in B d π + π and Bs K + K particle ID, hadron trigger 4.9 k tagged /10 7 sec (Br = ) particle ID, hadron trigger, excellent σt σφ /10 7 sec for m s = 20 ps k tagged /10 7 sec (Br = ) Rare decays B s µ + µ s = 10 /10 7 sec (Br = ), s/b = 3 30