北京今印联印刷器材有限公司材料安

1、Status of the LHCb Experiment 高原宁清华大学高能物理研究中心Introduction & physics motivationsStatus of the detector constructionTopics on physics potentialsConclusions高能物理学会第七界学术年会 2006年10月29日 桂林LHCb is a dedicated B physics experiment at the LHCForward spectrometer (running in pp collider mode)Great potential fo

2、r B physics!Pythia100b230b of B-hadronPT of B-hadronPhysics motivations The Standard model CP violation is described by the single complex phase in the CKM matrix, two unitarity triangles relevant to B physics at LHCb stat.Current SM fit of the Unitarity Triangles (including CDF result on Dms)a = 94

3、.6 4.6b = 23.9 1.0 = 61.3 4.5fs= 2.1 0.2 high statistics Bd and Bs samples are essential robust and efficient trigger, even for non-leptonic decays good decay vertex resolution; good tracking; good particle identification Many final states need to be reconstructed HIGH STATISTICSNews from the experi

4、mentr- and measuring sensors rather than x,y fast and easy impact parameters for use in the triggerVErtex LOcator “VELO21 stations (pile-up vetodetector)RF foilbeam-spot z=5.3cm-measuring sensorr-measuring sensor-sensor:radial strips (inner and outer)2048 stripsstereo angle(-20, +10)3798 m pitchr-se

5、nsor:concentric strips2048 strips4 sectors (45)40-103 mm pitchharsh radiation environment: n-n sensors: keep good resolution if undepleted sensor cooling to -5C with CO2 cooling system good impact parameters detectors as close as 8mm to LHC beam sensors placed in secondary vacuum (10-9 mbar) separat

6、ed from beam-vacuum just by an 300mm Al “RF-foilmove sensors out during filling (3cm) re-positioning accuracy: 1520 V 98% 200 mOuter Tracker InstallationSupport bridge installedwith modules1/4 of the stations are already equipped with modulesnow: testing, cabling, survey selection of specific B-deca

7、y channels for CP measurements without particle ID, the bkg-dilutes/overwhelms the signalRICH Particle IDBs DsBs Ds K2 RICH Detectors with 3 Cherenkov RadiatorsRICH1: 5cm silica aerogel (2-10GeV/c) 85cm C4F10 gas (50GeV/c) spherical (CF) and planar (glass) mirrorsRICH2: 170cm CF4 gas (100GeV/c)spher

8、ical and planar glass mirrorsbefore and behind the magnetq c(mrad)Expected photons detectedAerogel 7C4F10 30CF4 23RICH Photon DetectorHybrid Photon Detectors (HPDs):photo tubes with silicon pixel chip2.5x2.5mm2 resolution for single photonslow noise excellent single photon detection efficiency (200n

9、m600nm)85% detection efficiency (after photon conversion 25%)about 50% of HPDs are produced and tested only 3% failuresnumber of pixel hits/eventdatasimulation10GeV pions, 1.1m N2 RICH InstallationRICH2 cabling ongoingRICH1 magnetic shield, gas enclosure and seal to VELORICH2: installed end 2005 56

10、spherical mirrors aligned to 50 radCalorimeter System SPD/PS/ECAL/HCALthey all use similar cost efficient technology: scintillating tiles in between lead/steel absorbers read out via wavelength shifting fibresSPD: scintillating pads/tiles distinguish e and gPS: PreShower after 2.5cm of lead identifi

11、es electromagnetic particlesECAL: shashlik type measure energy of electromagnetic shower HCAL: iron interleaved with scintillating tiles energy of hadrons SPD-scintillating padECAL/HCAL PerformanceEEE (0.83 0.02)% (145 13) MeV)/E(9.40.2)%Ebeam GeVEEEbeam GeVECALHCALCalorimeter InstallationECAL in pl

12、ace since June 2005Activity now focuses on cabling / commissioning using calibration LEDsHCAL in place since Sept. 2005SPD/PS modules have been installed this summerMuonMulti-Wire-Proportional-Chambers (MWPC) & GEMs (at center at 1st station) 4ns time resolution use in the trigger (20% PT resolution

13、)muon filters are in place1380 MWP-Chambers production completed 24 GEM production is ongoingMWPCsTriple GEMsMWPC supportmuon filtertestbeam:anode efficiencyEfficiency %HV (kV) Two Trigger Levels:e,KL0: hardware trigger 10MHz (interaction rate) 1MHzcalorimeter: (SPD multiplicity, # ET clusters)muon:

14、 (two high pT muons)pile-up system (indentify multiple interactions)L0 Decision Unit Latency: 4msHLT: software trigger 1MHz2kHzall sub-detectors readingsL0 confirmation dedicated physics channel triggers depending on type of L0 triggertrigger on impact parametersMany different custom electronics, al

15、l close to final productionTrigger commissioning will start 2007L0 efficiencies: for channels withmuons: 90%leptons: 70%hadrons: 50%HLT efficiencies: . no final numbers: still in transitions from former L1+HLT scheme (it was 50-80%)OnlineEventFilterFarmReadout NetworkFront-end ElectronicsTFCSystemSt

16、orageSystemPCPCPCPCPCPCPCPCPCPCPCPC1800computer nodesFEFEFEFEFEFESwitchSwitchSwitchSwitchVELO TT IT OT RICH CALO MUON L01 MHz2 kHzFull detector info available for HLTLHCb common readout board (TELL1)commercial network switch MagnetMagnet has long been installedBdl : 4 Tm, warm coils4.2MWatt, 15 tons

17、 fully operationalmagnetic field map to precision: 3x10-4 , symmetry . polarity: DB/ 3x10-4 stray B stray field between VELO and TT fast PT info in Trigger - calculationo measurementVELOTTMagnetz cmBy TBeam Pipesupport wires25mrad Be section + Velo exit window1st and 2nd 10 mrad Be sectionstainless

18、steel sectionAll beam-pipe pieces are at hand, 1st section installed and sealed to the VELO vessel Selected topics on physics potentials1. Measurement of the angle from Bs Ds K+ CP asymmetry arises from interference between two tree diagrams via Bs mixing: Bs Ds+K- and Bs Ds-K+ Measures g - 2c extra

19、ct g ( c is determined using Bs J/y f decay, s(sin 2c) 0.06 for one year) Background from Bs Ds p is suppressed using PID information from RICH1 & RICH2 remaining contamination 10% Reconstruct using Ds- K-K+p- 5400 signal events/year The strong phase difference of the two diagrams can be resolved by

20、 fit two time-dependent asymmetries: Phase of Ds+K- asymmetry is D - (g - 2c) Phase of Ds-K+ asymmetry is D + (g - 2c) can extract both D and (g - 2c)s(g) 14 in one yearAsymmetries for 5 years of simulated dataTheoretically clean; insensitive to new physics Selected topics on physics potentials2. Me

21、asurement of the angle from B0 + , Bs K+ K bu processes with possible large b d(s) penguin contributions Measure time-dependent CP asymmetries for B0 p+p- and Bs K+K-ACP(t) = Adir cos(Dm t) + Amix sin(Dm t) extract four asymmetries Adir(B0 p+p-) = f1(d, q, g) deiq = ratio of penguin and tree Amix(B0

22、 p+p-) = f2(d, q, g, b) amplitudes in B0 p+p- Adir(Bs K+K-) = f3(d, q, g) deiq = ratio of penguin and tree Amix(Bs K+K-) = f4(d, q, g, c) amplitudes in Bs K+K- Assume U-spin flavour symmetry (under interchange of d and s quarks)d = d and q = q R. Fleischer, PLB 459 (1999) 306 Taking b and c from oth

23、er channels can solve for gblue bands from Bs KK (95% CL)red bands from B (95% CL)ellipses are 68% and 95% CL regions (input = 65)d- plot“fake” solutionTheoretical uncertainty from U-spin assumption (can be tested);Sensitive to new physics in the penguin loopss(g) 5 in one year Selected topics on ph

24、ysics potentials3. Measurement of the angle from B0 D0K*0 , D0K*0 CP asymmetry arises from interference between two tree diagrams via D0-mixing Measure six rates ( following 3 + CP-conjugates ) can be extracted from triangles Gronau and Wyler, PLB 265 (1991) 172, Dunietz, PLB 270(1991) 75 3.4K, 0.5K and 0.6K events respectively for one year data takings(g) 7-8 in one yearNo theoretical uncertainties; sensitive to new physics in DCP Selected topics on physics potentials4. Charm physics at LHCb Selected topics on physics potentials5. Bc Studies at TsinghuaBcGen (B