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Status of the LHCb Experiment. Introduction & physics motivations Status of the detector construction Topics on physics potentials Conclusions. 高原宁 清华大学高能物理研究中心. 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 LHC. P T of B-hadron. 100 μ b.

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Status of the LHCb Experiment


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    1. Status of the LHCb Experiment • Introduction & physics motivations • Status of the detector construction • Topics on physics potentials • Conclusions 高原宁 清华大学高能物理研究中心 高能物理学会第七界学术年会 2006年10月29日 桂林

    2. LHCb is a dedicated B physics experiment at the LHC

    3. PT of B-hadron 100μb 230μb Pythia η of B-hadron Forward spectrometer (running in pp collider mode) Great potential for B physics!

    4. Physics motivations • TheStandard model CP violation is described by the single complex phase in • the CKM matrix, two unitarity triangles relevant to B physics at LHCb stat.

    5. Current SM fit of the Unitarity Triangles (including CDF result on Dms) • a = 94.6°± 4.6° • b = 23.9° ± 1.0° • = 61.3° ± 4.5° fs= 2.1° ± 0.2°

    6. — high statistics Bdand Bs samples are essential — robust and efficient trigger, even for non-leptonic decays — good decay vertex resolution; good tracking; good particle identification

    7. Many final states need to be reconstructed … HIGH STATISTICS

    8. News from the experiment

    9. r-measuring sensor -measuring sensor RF foil beam-spot z=5.3cm 21 stations (pile-up veto detector) VErtex LOcator “VELO” r- and  measuring sensors rather than x,y  fast and easy impact parameters for use in the trigger • -sensor: • radial strips • (inner and outer) • 2048 strips • stereo angle(-20, +10) • 37–98 µm pitch • r-sensor: • concentric strips • 2048 strips • 4 sectors (45) • 40-103 mm pitch harsh radiation environment:  n-n sensors: keep good resolution if undepleted  sensor cooling to -5°C with CO2 cooling system

    10. Vertex Locator Mechanics • good impact parameters •  detectors as close as 8mm to LHC beam • sensors placed in secondary vacuum (10-9 mbar) separated from beam-vacuum just by an 300mm Al “RF-foil” • move sensors out during filling (3cm) • re-positioning accuracy: <10mm RF-foils vacuum vessel installed and surveyed (0.2mm accuracy)

    11. VELO Modules Production and Commissioning Test 9 out of 42 final detector modules are ready  awaiting “burn-in” Testbeam: Alignment and Commissioning challenge using (almost) final HARD and LHCb SOFTware real life detector modules real “LHCb visualisation tool” • successfully operated: • important experience for commissioning online/offline software • lots of test-beam data to be analysed now

    12. _ bb vertex resolution: Expected VELO Performance use all tracks that include VELO: core x = y = 8 m impact parameter sIP= 14mm + 35mm/pT core z= 44 m average:40mm dominated by material before 1st measurement average B flight path = ~1cm !!

    13. Other Tracking Detectors magnet: Outer Tracker: straw tubes • TT-station • silicon strips: • PT info for the trigger • Inner Tracker: • silicon strips • 1.3% of the station surface • 20% of accepted tracks

    14. TT-Station • 4 layers: (2 with ±5º stereo angle) • silicon strips: 143k channels, 7.9m2 • up to 39cm readout strips • inner sectors connected via Kapton interconnect cables • operation at ~5°C, liquid C6F14 cooling Good quality modules with low leakage currents Station assembly for testing in the lab upper hybrid lower hybrid ~ 60% of modules finished

    15. Inner Tracker • silicon strips: 129k channels, 4.3m2 • 336 modules • 11 and 22cm long modules/strips • 4 individual boxes per station • 4 layers per station:(2 stereo layers) • operation at ~5°C, liquid C6F14 cooling ~ 60% of modules produced and tested

    16. Inner Tracker Installation First Inner Tracker box has been assembled and partially tested • support frames have been brought to the pit • will be cabled soon

    17. Track 5mm cells e- e- e- pitch 5.25 mm Outer Tracker • Straw tube tracker: • ArC02 drift gas • resolution: 200mm • 4 layers / station • 2 stereo layers ±5º HV > 1520 V • ε 98% • σ 200 µm Module production finished December 2005 !

    18. Outer Tracker Installation …with modules Support bridge… … installed • 1/4 of the stations are already equipped with modules • now: testing, cabling, survey

    19. RICH – Particle ID • selection of specific B-decay channels for CP measurements • without particle ID, the bkg-dilutes/overwhelms the signal Bs Ds K Bs Ds

    20. 2 RICH Detectors with 3 Cherenkov Radiators • RICH1: • 5cm silica aerogel (2-10GeV/c) • 85cm C4F10 gas (<50GeV/c) • spherical (CF) and planar (glass) mirrors • RICH2: • 170cm CF4 gas (<100GeV/c) • spherical and planar glass mirrors before and behind the magnet q c(mrad) Expected photons detected • Aerogel 7 • C4F10 30 • CF4 23

    21. number of pixel hits/event data simulation RICH – Photon Detector • Hybrid Photon Detectors (HPDs): • photo tubes with silicon pixel chip • 2.5x2.5mm2 resolution for single photons • low noise  excellent single photon detection efficiency (200nm–600nm) • 85% detection efficiency (after photon conversion ~25%) 10GeV pions, 1.1m N2 about 50% of HPDs are produced and tested  only 3% failures

    22. RICH Installation RICH1 magnetic shield, gas enclosure and seal to VELO RICH2: installed end 2005 56 spherical mirrors aligned to σθ~ 50 μrad RICH2 cabling ongoing

    23. SPD-scintillating pad Calorimeter System SPD/PS/ECAL/HCAL they all use similar cost efficient technology: scintillating tiles in between lead/steel absorbers read out via wavelength shifting fibres SPD: scintillating pads/tiles  distinguish e± and g PS: PreShower after 2.5cm of lead identifies electromagnetic particles ECAL: shashlik type  measure energy of electromagnetic shower HCAL: iron interleaved with scintillating tiles  energy of hadrons

    24.  E E E E (9.40.2)%  (0.83  0.02)%   ((145  13) MeV)/E E Ebeam GeV Ebeam GeV ECAL/HCAL Performance ECAL HCAL

    25. Calorimeter Installation SPD/PS modules have been installed this summer HCAL in place since Sept. 2005 ECAL in place since June 2005 • Activity now focuses on cabling / commissioning using calibration LEDs

    26. Muon Multi-Wire-Proportional-Chambers (MWPC) & GEMs (at center at 1st station) 4ns time resolution  use in the trigger (20% PT resolution) muon filter MWPC support MWPCs Triple GEMs testbeam:anode efficiency Efficiency [%] • muon filters are in place • 1380 MWP-Chambers production completed • 24 GEM production is ongoing HV (kV)

    27. e, ,K Two Trigger Levels: • L0: hardware trigger 10MHz (interaction rate) 1MHz • calorimeter: (SPD multiplicity, # ET clusters) • muon: (two high pT muons) • pile-up system (indentify multiple interactions) • L0 Decision Unit • Latency: 4ms • HLT: software trigger 1MHz2kHz • all sub-detectors readings • L0 confirmation • dedicated physics channel triggers depending on type of L0 trigger • trigger on impact parameters L0 efficiencies: for channels with muons: ~90% leptons: ~70% hadrons: ~50% HLT efficiencies: .. no final numbers: still in transitions from former L1+HLT scheme (it was 50-80%) Many different custom electronics, all close to final production Trigger commissioning will start 2007

    28. PC PC PC PC PC PC PC PC PC PC PC PC Online LHCb common readout board (TELL1) Front-end Electronics VELO TT IT OT RICH CALO MUON L0 TFCSystem FE FE FE FE FE FE Readout Network 1 MHz commercial network switch Event FilterFarm Switch Switch Switch Switch ~1800 computer nodes 2 kHz Full detector info available for HLT StorageSystem

    29. ∫Bdl : 4 Tm, warm coils 4.2MWatt, 15 tons - calculation o measurement By [T] fully operational TT VELO Magnet z [cm] Magnet • Magnet has long been installed stray B stray field between VELO and TT  fast PT info in Trigger • magnetic field map to precision: 3x10-4 , • symmetry w.r.t. polarity: • DB/<B> ~ 3x10-4

    30. Beam Pipe • 25mrad Be section + Velo exit window • 1st and 2nd 10 mrad Be section • stainless steel section support wires All beam-pipe pieces are at hand, 1st section installed and sealed to the VELO vessel

    31. 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  extract g ( c is determined using Bs J/yf decay, s(sin 2c) ~ 0.06 for one year)

    32. The strong phase difference of the two diagrams can be resolvedby fit two time-dependent asymmetries:Phase of Ds+K- asymmetry is D - (g - 2c)Phase ofDs-K+ asymmetry is D + (g - 2c)can extract both D and(g - 2c) • Background from Bs Dsp is • suppressed using PID information • from RICH1 & RICH2 •  remaining contamination ~ 10% • Reconstruct using Ds- K-K+p- • 5400 signal events/year s(g) ~ 14 in one year Asymmetries for 5 years of simulated data Theoretically clean;insensitive to new physics

    33. Selected topics on physics potentials2. Measurement of the angle from B0 +– , Bs K+ K– • bu 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(Dmt) + Amix sin(Dmt)  extract four asymmetries Adir(B0 p+p-) = f1(d, q, g) deiq = ratio of penguin and tree Amix(B0 p+p-) = f2(d, q, g, b) amplitudes in B0 p+p-Adir(Bs K+K-) = f3(d’, q’, g) d’eiq’ = ratio of penguin and tree Amix(Bs K+K-) = f4(d’, q’, g, c) amplitudes in Bs K+K-

    34. “fake” solution d- plot • 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 other channels can solve for g blue bands from Bs  KK (95% CL) red bands from B   (95% CL) ellipses are 68% and 95% CL regions(input = 65) s(g) ~ 5 in one year Theoretical uncertainty from U-spin assumption (can be tested);Sensitive to new physics in the penguin loops

    35. Selected topics on physics potentials3. Measurement of the angle from B0 D0K*0 , D0K*0 – • CP asymmetry arises from interference between two tree diagrams • via D0-mixing

    36. 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 taking s(g) ~ 7-8 in one year No theoretical uncertainties; sensitive to new physics in DCP

    37. Selected topics on physics potentials4. Charm physics at LHCb –

    38. Selected topics on physics potentials5. Bc Studies at Tsinghua – BcGen (BcVGPY) is now LHCb standard Physics + Manual > LHCb note

    39. Bc mass & lifetime Refinements due to Trigger change > LHCb note soon

    40. Selected topics on physics potentialOutlook • A possible scenario after the LHCb measurement of g: new physics? • Many other interesting topics not covered by this talk •  TDR, LHCb notes, …

    41. Conclusions • LHCb is dedicated to the study of B physics, with a devoted trigger,excellent vertex and momentum resolution, and particle identification • Construction of the experiment is progressing wellIt will be ready for first LHC collisions in 2007 (TELL1s from Tsinghua group are delivered to the experiment) • LHCb will give unprecedented statistics for B decays, including access to the Bs meson, unavailable to the B factories • Our Beauty is also Charming • Physics preparations for Bc physics from Tsinghua group is well underway.