Status and prospects of the LHCb experiment

Transcription

1 Status and prospects of the LHCb experiment Overview Spectrometer Vertex Detector RICH Physics Program Trigger Strategy Status and Outlook U. Straumann, Uni Zuerich Geneva, 13. April 2005

2 pt vs for detected B hadrons Pythia: B meson production at a 14 TeV pp collider => need forward detector 100 b 230 b Momentum distribution of B decay products in LHCb: example B s D s K high average p = 30 GeV/c => small multiple scattering allows excellent resolutions (momentum, livetime, mass)

3 Luminosity is adjustable by tuning the beam size (maximal reduction of factor 100 seems possible) What is the optimal luminosity for LHCb? Operate with several vertices per bunch crossing (trigger, reconstruction)? Probability for n interactions vs luminosity: Also detector occupancy and radiation damage is an issue => choose L ~ cm 2s 1 to start with 1

4 LHCb: a magnetic dipole spectrometer + vertex detector + Calo + particle ID fitted in existing pit at IP8

5 Spectrometer features: Length: 10 m Max. Field (on axis): 1.1 T B dl = 4 Tm Detector hit position resolution µm Amount of dead material: ca. 15% X % from vertex det. + RICH1 Momentum resolution 0.4% magnet TT: silicon strips T1, T2, T3: inner part: silicon strips outer part: straw tubes

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7 Contributions to momentum resolution: hit position resolution: ~ p multiple scattering: constant average momentum Detailed Geant simulation:

8 Production outer tracker ongoing: Warsaw, Heidelberg, NIKHEF Gain uniformity measurements with Fe 55 source: Fe 55 Test P h, mv

9 Outer Tracker Electronics max. drifttime 3 BX TDC ASD GOL L0 Buffer L1 Buffer DAQ ~100m 200 fc bias L0 BX L1 FE Electronics on the detector HV LV TFC ECS Electronics Service Box Cooling counting room Power / Control

10 Silicon tracker: inner part of T1, T2, T3 and TT Zurich, Lausanne, MPI HD, Santiago, Kiev Silicon sensors (HPK): single-sided p-on-n 300 µm / 400 µm thick 108 mm long strips 384 readout strips 198 µm pitch 50 µm wide implants T1, T2, T3: Lausanne front-end hybrid cooling balcony pitch adaptor carbon-fibre support silicon sensors (2 sensor not shown) nd

11 TT station (Zurich) Level-1 trigger / tracking upstream of magnet: 4 detection layers 14-sensor ladders left/right of beam pipe 7-sensor ladders above/below beam pipe each ladder several readout sectors all hybrids outside of acceptance CMS-OB2 sensors (HPK): p-on-n, 500 µm thick mm long strips 512 readout strips 183 m pitch 46 m wide implants front-end hybrids cooling balcony silicon sensors Kapton interconnects carbon-fibre support rails

12 2nd final ladder produced in Zurich

13 Beetle 1.2 block diagram ASIC laboratory Heidelberg 0.25 μm CM OS proc es s (IB M), radi atio n ha rd

14 Digital optical readout system: 8 bit resolution

15 Silicon strip detector R&D Test beam at CERN X7: 120 GeV πlaser setup in Zurich

16 ST R&D results (from Matthew Needham): Observations 1 BX

17 ST R&D results: Dip size

18 ST R&D results: Noise and reminder in next BX

19 Why do we not see the noise from the resistance of the long strips? Beetle Ladder Cicuit analysis: input FET of amplifier: white noise corresponds to 68 Ω total strip resistance is 160 Ω SPICE simulation to determine spectrum of total noise use test pulse shape and Laplace transform to determine bandwidth of beetle. => Ladder noise < 20% of FET noise (suppresion factor >10) [nv2/hz] log (f)

20 Vertex detector (VELO): r geometry 21 stations approaching 8 mm to beam proper time resolution ~ 40 fs

21 Simulation of ms using Bs Ds + decays => 5 observation of Bs oscillation for ms < 68 ps 1 (in 107sec)

22 RICH: 2 detectors with 3 radiators to cover full momentum range. novel photodetectors: HPD photocathode, Si pixel det. 500 vacuum tubes 1024 pixels mm2

23 What to measure? A wealth of interesting B meson decay channels! Precise measurement of B0s-B0s mixing: ms, s and phase s. Bs Ds, Bs J Bs J ( ) Precise determinations, including from processes at tree-level, in order to disentangle possible NP contributions Bs DsK, B0 D0K*0, B0 Bs KK, Several other measurements of CP phases in different channels for over-constraining the Unitarity Triangles B0 Ks,Bs B0 B Search for effects of NP appearing in rare exclusive and inclusive B decays B0 K* B0 K*0l+l-, b sl+l-, Bs... Observables: decay rates, CP violation parameters, angular distributions

24 We might get measurable contributions from physics beyond standard model e.g. as contributions to SM penguin and box diagrams! What does LHCb add to B factories? Bs decays Bc decays Bd more statistics and different systematics b baryons What does LHCb add to CMS and Atlas? better proper time resolution 2* better invariant mass resolution (10 MeV on B mass in J Pion/Kaon particle id. program extends over whole LHC era s

25 Results of Monte Carlo simulation studies: Det. eff. (%) 12.2 B Bs K K 5.4 B s D s Bs Ds K 5.3 B0 D~0 (K )K*0 6.5 B0 J/ ( ) K0S 5.8 B0 J/ (ee) K0S 7.6 Bs J/ ( ) 6.7 Bs J/ (ee) 6.0 B0 9.5 B0 K* 9.7 Bs + few more channels in TDR Rec. eff. (%) Sel. eff. (%) Trig. eff. (%) Tot. eff. (%) Vis. Annual BR signal 6 (10 ) yield k k k k k k k k k k k k B/S from bb bkg. < < 1.0 < < < 7.1 < 0.7 < 2.4 S=L i n t b b 2 f B BR tot L i n t = cm 2 s s b b=500 b f B =0.4 B d, B f B=0.1 B s f B 10 3 B c

26 = arg Vub from Bs Ds K and Bs Ds K (+ c.c.) both tree decays, which interfere via Bs mixing (time dependant) CP asymmetry measures s Very little theoretical uncertainty, insensitive to new physics s will be determined using Bs J/ decays extract Bs Ds gives background to Ds K (BR ~ 12 higher) Suppress using RICH residual contamination only ~ 10% 5400 signal events/year S/B (from bb) > 1 (at 90% CL) ) = 150 per year. B0s b W+ s c s u D +s K-

27 Latency: Event rate Trigger 40 MHz Level 0: high pt (,e,,h) + pile up veto FPGA based, data stored on detector 4 s 1 MHz Level 1: high IP, high pt tracks (Vtx, TT) processor farm, data stored in local buffers 1 ms 40 khz HLT: use complete event data processor farm 10 ms HCAL trigger dominates 200 Hz khz HLT rate Event type 200 Hz Exclusive B candidates 600 Hz High mass di-muons 300 Hz D* candidates 900 Hz Inclusive b (e.g. b ) Physics B (core program) MUON trigger dominates J/, b J/ X (unbiased) Charm (mixing&cpv) B (data mining) ECAL trigger dominates

28 LHCb installation status Muon filter Calorimeter frame Dipole magnet (completed) Installation will be completed in 2006