Status of the LHCb experiment

Transcription

1 Status of the LHCb experiment Elie Aslanides CPPM, IN2P3-CNRS et Université de la Méditerranée, France on behalf of the LHCb Collaboration LISHEP Itacuruçá, Rio de Janeiro, April 4, 2006

2 Introduction LHCb detector status Expected performances Conclusion

3 Introduction LHCb is the dedicated B physics experiment at the LHC devoted to the precision study of CP violation and rare decays. The LHCb Collaboration includes 47 institutes from 15 countries and more than 600 members. Extend B-physics results obtained in B-factories and the Tevatron Search for new physics in a complementary way to ATLAS/CMS LHCb may be the only running Beauty Physics experiment, after the B-factories (if no Super B-factories are approved)!

4 Baseline physics goals of LHCb a second generation experiment With a luminosity <L> cm 2 s 1, 10 7 s/year, 2 fb -1 /year, LHCb should reach in 5 years unprecedented precisions σ(>5 y) SM (expect) φ s (B s ccss) ~0.013 ~ γ (D s K, D 0 K *0 ) ~1 ~60 (tree only) γ (ΚΚ+ππ) ~2 ~60 (tree + penguin) Br(B s µ + µ ) ~ ~ B d K 0 µ + µ A FB (s) sensitive to NP 22k events expected >5y (Super-KEKB similar by 2020!) ±0.04 A FB (s) Belle 357 fb events 1000 fb 1 by ~2009

5 Beauty production at the LHC At s = 14 TeV, pp collisions have large σ bb ~ 500 µb but small compared to the total, σ bb /σ tot ~ interesting B decays have low b.r. ~10-5 Bunch crossing rate at the LHC is 40 MHz LHCb average L ~ cm -2 s -1 2 fb -1 / year (10 7 s) bb produced/year! most events due to single interactions per bunch crossing! Probability pp interactions/crossing Luminosity [cm 2 s 1 ]

6 Beauty production at the LHC Forward peaked, correlated " b anti-b" pair production" LHCb is a forward spectrometer ( mrad) p p pt of B-hadron p T vs η for detected B hadrons ATLAS/CMS 100 µb LHCb 230 µb eta of B-hadron

7 Experimental requirements Efficient and flexible Trigger High quality Event Reconstruction particle identification hadrons,µ s and e s, as well as γ s, π 0 s excellent tracking and vertexing good p, E, Mass and τ resolutions ~10 mm b b Powerful Readout and on line processing (HLT)

8 Spectrometer Dipole magnet Tracking system Calorimeters Muon system 250 mrad Vertex Locator p p 10 mrad RICH detectors

9 LHCb at Point 8 Shielding wall Offset Interaction Point Electronics + CPU farm Detectors can be moved away from beam-line for access

10 Introduction LHCb detector status Expected performances Conclusion

11 November 2005

12 The beam pipe Located in the high rapidity region where particle density is high, it is a major source of secondaries! 3 Beryllium sections Stainless steel section UX85/1 UX85/2 UX85/3 1mm 1-2 mm 3-4 mm UX85/4 VELO window Al flanges and bellows Stainless steel flanges and bellows

13 Production is progressing well VeLo window prototype UX 85/1 (Be) COMPLETED

14 UX 85/2 (Be) tested at IHEP, Protvino Acceptance tests NEG coating UX 85/3 ( Be) under construction by Kompozit, Moscow, All components in production. Installation early summer 06, fits in general planning.

15 Warm dipole magnet B dl = 4 Tm Iron yoke 15 ton; Power 4.2 MW Nominal field reached on Nov. 04 The magnet

16 Magnetic field measurements Dec. 04; June 05 including RICH1 shield and all iron Dec. 05 [final and Polarity ±] TT VeLo magnet B dl in VELO-TT region needed for fast online p T 60 3D Hall probes B inside RICH is ok for the HPD operation!

17 Vertex Locator Key element around the IP 8cm ~1m 8cm 21 stations of Silicon 300µ-strip detectors r-φ geometry variable pitch [ r (40-102µ);φ (36-97µ) ] 172 k channels

18 VELO detector vacuum box 300µ AlMg3 RF shield for sensors + electronics guides the beams mirror charge suppresses dynamic vacuum phenomena suppresses electron multipacting RF box corrugations

19 To give precise vertex reconstruction VELO approaches to 8 mm from beam Radiation ~ n eq./cm2/y Expected lifetime ~3 years; Si to be replaced Detector stations in 2 retractable halves Complex mechanics to allow retraction during beam injection (~completed) VELO uses vacuum like a «roman pot» VELO operated at 5 C (CO2 cooling)

20 Sensors characteristics: n+n type, double metal layers 300 µ, laser cut FE electronics (Beetle chip) mounted on thin kapton, connected to the sensors via Pitch Adapters Modules production started! should be completed ~end summer 06 RF boxes installed September 06 Vacuum tests October 06 VELO modules installed in RF boxes >January 07

21 Tracking Trigger Tracker Si µ-strip detector 144 k channels TT Outer Tracker Straw Tubes 56 k channels T1 T2 T3 Inner Tracker Si µ-strip detector around the beam pipe 130 k channels

22 Trigger Tracker Four Si µ-strip detection layers, ~ 8 m 2 of silicon, covering the nominal LHCb acceptance. Arranged in two double layers (0,+5 ) and (-5,0 ) 30 cm apart. Together with VELO, the TT measures the p T of the high IP tracks for use in the trigger. Offline: decay tracks of long-lived neutral particles decaying outside the VELO fiducial volume. 500 µ silicon, CMS OB2-type sensors Strips: pitch 198 µ; length 11, 22, 33 cm Radiation: n eq /cm²/10 year Operated at 5 C

23 Almost all sensors and components in hand TT support structure will be installed in April TT installation in UX85 between June and October 06.

24 3 Tracking stations Outer Tracker Inner Tracker

25 T stations: Outer Tracker 3 stations, each made up of Kapton/Al straws glued together to form modules 5 mm 4 double-layers (0,+5 ) and (-5,0 ) Ar/CF 4 /CO 2 modules 64-cells wide modules only ~0.7% of 1 X 0 : light panel (Rohacell core with carbon skins) light straws Installation in UX85 November 06 Commissioning starting December 06

26 T stations: Inner Tracker Silicon strip detectors close to beam pipe, in region of high occupancy only 2% of area, but 20% of tracks 410 µm thick for two-sensor ladders arranged in boxes around beam pipe 0.4 m 1.2 m 320 µm thick for single sensors Same sensors as Trigger Tracker Strip length 11, 22 cm, pitch 198 µ Four layers (0, +5, -5, 0 ) Cooled -5 C Radiation n eq /cm²/10 years Installation in UX85 in June 06

27 Ring Imaging CHerenkov RICH1 Three radiators in two detectors to give π-k separation from GeV Aerogel + C 4 F 10 CF4 RICH2 Θ 25 to 250 mrad p 2 to 60 GeV/c 200k channels Θ 15 to 100 mrad V 120 mrad H p 17 to 100 GeV/c 295k channels

28 Novel photon detectors: Hybrid Photon Detectors ~500 tubes, each with a 32x32 pixel sensor array Pixels size (500x500 µm 2 ) Operated at 20 kv Test beam image Pixels ~150 HPD s already in hand! 10 Production at a rate ~30 HPD /month Pixels

29 RICH1 combines the use of aerogel n=1.03 and C 4 F 10 n= radiators for low momentum particles 7 x 14 HPD array High clarity aerogel Light weight spherical mirrors Glass plane mirrors outside the acceptance Quartz windows to HPD material budget ~7.5% X 0 Switched from Be to C spherical mirrors, quite recently! New design tested April 06; production expected < end 06. RICH-1 installation completed ~ March 2007.

30 High clarity aerogel was developed with a Novosibirsk grou now in production!

31 Magnetic shielding of RICH1 now installed Magnetic measurements in the HPD plan show residual field of less than 25 Gauss

32 RICH2 uses CF4 gas radiator for high p particles (n=1.0005) Flat mirror Spherical Mirror Support Structure 7 m Central pipe Gas vessel: 100 m 3 Photon funnel Shielding

33 In position Mirrors alignment ~150 µrad mirror movement ~100 µrad cf. RICH-2 Cherenkov angle resolution ~ 700 µrad! RICH-2 completed end 2006

34 Calorimeter system SPD/PS HCAL ECAL SPD/PS 2 planes of Scintillating Pads + 2 X 0 Pb (1.5 cm); 0.1λ I ECAL Pb scintillator Shashlik calorimeter, 25 X 0 ; 1.1 λ I HCAL Fe scintillator tile calorimeter, 5.6 λ I 19k channels, R/O by WLS fibres to PM or MaPMT s

35 Pre-shower SPD / PS 2 scintillator pad planes on either side of a Pb absorber Inner Middle Outer Modules Moving cable trays support structure 4x4 cm 2 6x6 cm 2 12x12cm 2 4 super modules per half detector R/O cables MAPMT+ VFE VFE + MAPMT MAPMT Clear fibers ECAL 16 Super modules x (2 x 13 modules) SPD SPD PS PS 2 x 5952 channels particles

36 PS/SPD installation has started the Pb modules are in place! Detector installation April to ~September 06

37 Electromagnetic (shashlik) calorimeter Two retrievable halves 3312 modules, 25X 0 Pb σ E /E = 10% / E 1% Electron. platform Beam plug modules Chariot stacked: ~ 6 m high positioning agrees to specifications to <1mm!

38 In place since June 05 Commissioning 6000 ch.with LED monitoring going on!

39 Hadronic Calorimeter HCAL: σ E /E = 80% / E 10% Tile calorimeter of 52 HCAL modules Electron. platform scintillators particles modules Beam plug fibers light-guide PMT 8 blocks of Sc/Fe Chariot HCAL module

40 HCAL in place since September 05 ±1.5 mm HCAL 1500 ch. commissioning using LED monitoring going on!

41 2005 was the year of detector assembly and installation HCAL ECAL 2006 is the year of R/O electronics installation and detector commissionin

42 M1 M2 The Muon system M3 M4 M5 provides muon identification and contributes to the Trigger

43 The muon detector is composed of 5 stations MWPC s are used everywhere except in the highest rate (>100 khz/cm 2 ) inner part of M1 where triple-gem s are used. ~500 khz/cm 2 < 184 khz/cm 2 > Efficiency > 96% in 20ns Ar(45)/CO2(15)/CF4(40) The muon system has a projective (x,y) geometry pointing to the IP to facilitate the search of µ candidates in the L0 trigger processor. 20 types of chambers: 1368 MWPC s and 24 «triple-gem s». 125k physical channels; 26k logical channels.

44 Status of the Muon detector MWPC s and 3-GEM s are under construction 1053 chambers have been produced (~tested) so far (March 31) M1R4 Expected end of production M2, M3. M5 summer 06; M4 October 06; M1 end 06. M1R1

45 Muon detector installation and commissioning Muon towers assembled with electronics and gas racks M2, M3, M4, M5 Jan 2007; M1 Jan. March 2007 MUON commissioning Feb March 07

46 The LHCb trigger 40 MHz Pile up system Calorimeters Muons Level 0 p T µ, e, h, γ Custom Electronics 4 µs latency Full detector information 1 MHz HLT Confirms L0 Associates p T /IP Explores µ, e, h, γ Selects event types Processor farm 2 khz Event size ~35kB storage

47 Event selection L0 efficiencies E T >3.6 GeV p T >1.1 GeV E T >2.8 GeV E T >2.6 GeV A current thought for the band width at the HLT output HLT rate Event type Calibration Physics 200 Hz Exclusive B candidates Tagging B (core program) 600 Hz High mass di-muons Tracking J/ψ, b J/ψX (unbiased) 300 Hz D* candidates PID Charm (mixing & CPV) 900 Hz Inclusive b (e.g. b m) Trigger B (data mining)

48 Trigger status L0 components production started L0µ Processor card 9U 220 mm 18 layers, Class optical links at 1.6 Gb/s 5 StratixGX FPGAs 96 copper serial links at 1.6 Gb/s L0 commissioning: components in autumn 06 trigger early 07 HLT software ready June 06 Event Filter Farm installed early 07

49 Computing A Filter Farm of ~2000 CPU nodes at pit 8 and Extensive use of LCG for offlin Real Time Trigger Challenge in 2005 ( test-bed with 44 CPU nodes) implemented and tested DAQ architecture run the trigger algorithms, test and control of the EB and the data tranfer by the ECS R/O of complete detector at 1 MHz Fully assembled demo-rack used in the RTTC 05 All components finalized; many ordered. Installation: ECS and DAQ hardware 06 Event Filter Farm 2007

50 Introduction LHCb detector status Expected performances Conclusion

51 Expected performances Studied using fully-simulated events Pythia tunned on CDF, UA5 GEANT4 Multi-particle interactions Spill-over effects full pattern recognition Interactive analysis display PANORAMIX [See talk of Leandro de Paula for the Physics Expectations]

52 Tracking Reconstruction of tracks passing through full spectrometer: efficiency ~ 95%, with a few percent of ghost tracks Momentum resolution p/p ~ 0.4% Impact parameter resolution σ IP ~ 20 µm for high-p T tracks From VELO vertex detection the proper time resolution ~40 fs

53 Particle Identification RICH system provides excellent hadron identification GeV K tagging and clean separation of two-body B decays Efficiency (%) Κ Κ π K separation π Κ Events / 20 MeV/c B d ππ B d πk B s πk B s KK Λ b pk Λ b pπ No RICH With RICH Momentum (GeV/c) Lepton ID: for e (µ) in ECAL (Muon) efficiency ~ 90% for π misid rate of < 1% Invariant mass [ GeV/c 2 ]

54 Neutrals reconstruction Reasonable efficiency for π 0 has been achieved for B 0 π + π π 0 study, using both resolved (separate clusters) and merged cluster shapes in the calorimeter (unassociated to charged tracks) Merged Resolved π + π π 0 mass (GeV) Recent study of η π + π π 0 gave a mass resolution ~ 12 MeV (resolved) K S π + π efficiency ~ 75% if decay in VELO, lower otherwise. Modes with multiple neutrals will be challenging

55 Flavour tagging e, µ from semi-leptonic decays K ± from the b c s jet/vertex charge Q VTX tagging B same side π/k SV signal B Tagging power εd 2 = ε(1 2w) 2 (in %) Tag LHCb CMS ATLAS Muon Electron Kaon Jet/vertex charge Same side Combined tagging power for B S in LHCb is ~ 6% Note ~2% at the Tevatron ~30% at B-Factories Tagging power for B 0 ~ 4% (reduced same side tagging) Recent Neural Network based study achieved 9% for B S tagging!

56 Illustration of B physics sensitivity observation of B s B s oscillation Use mode B s D s π + ; 1 year of data (80k selected events) for m s = 20 ps -1 (SM preferred) + Dilution by flavour tagging: εd 2 ~ 6% for B s decays + Proper time resolution ~ 40 fs + Signal/Background ~ 3 (from 10 7 inclusive bb events) + Effect of acceptance Events Perfect reconstruction Oscillations still clearly seen! Proper time (ps)

57 Illustration of B physics sensitivity observation of B s B s oscillation Use mode B s D s π + ; 1 year of data (80k selected events) for m s = 20 ps -1 (SM preferred) + Dilution by flavour tagging: εd 2 ~ 6% for B s decays + Proper time resolution ~ 40 fs + Signal/Background ~ 3 (from 10 7 inclusive bb events) + Effect of acceptance Events Perfect reconstruction + flavour tagging Oscillations still clearly seen! Proper time (ps)

58 Illustration of B physics sensitivity observation of B s B s oscillation Use mode B s D s π + ; 1 year of data (80k selected events) for m s = 20 ps -1 (SM preferred) + Dilution by flavour tagging: εd 2 ~ 6% for B s decays + Proper time resolution ~ 40 fs + Signal/Background ~ 3 (from 10 7 inclusive bb events) + Effect of acceptance Events Perfect reconstruction + flavour tagging + proper time resolution Oscillations still clearly seen! Proper time (ps)

59 Illustration of B physics sensitivity observation of B s B s oscillation Use mode B s D s π + ; 1 year of data (80k selected events) for m s = 20 ps -1 (SM preferred) + Dilution by flavour tagging: εd 2 ~ 6% for B s decays + Proper time resolution ~ 40 fs + Signal/Background ~ 3 (from 10 7 inclusive bb events) + Effect of acceptance Events Perfect reconstruction + flavour tagging + proper time resolution + background Oscillations still clearly seen! Proper time (ps) 5

60 Illustration of B physics sensitivity observation of the B s B s oscillation Use mode B s D s π + ; 1 year of data (80k selected events) for m s = 20 ps -1 (SM preferred) + Dilution by flavour tagging: εd 2 ~ 6% for B s decays + Proper time resolution ~ 40 fs + Signal/Background ~ 3 (from 10 7 inclusive bb events) + Effect of acceptance Events Perfect reconstruction + flavour tagging + proper time resolution + background + acceptance Oscillations still clearly seen! Proper time (ps)

61 Illustration of B physics sensitivity the B s B s oscillation frequency Plot of the uncertainty σ A on the fitted oscillation amplitude vs m S σ Α 0.9 = 1.0 ± 0.1 τ/ τ simulated LHCb LHCb could exclude the full SM range in one year! If observed, σ stat ( m S )~0.01 ps -1 could make a 5σ observation of m S up to 40 ps -1 well beyond the SM, in 5 weeks! σ observation of B s oscillations for m s < 68 ps 1 with 2 fb m s [ps 1 ]

62 Conclusion The LHCb detector combines all qualities required for the study of B-physics at the LHC: powerful trigger, precision vertexing and tracking, excellent particle id and proper time resolution. The expected performance of LHCb, and the high b production rate at the LHC, should allow to extend the results of the B- factories, to overconstrain the unitarity triangle and to search for new physics in a complementary way to ATLAS and CMS. Construction and installation of all detector components is progressing well. LHCb is on schedule to be ready for global commissioning by end 2006 and the first collisions in 2007!