1 / 35

LHCb: status and perspectives

LHCb: status and perspectives. Yu. Guz, IHEP, Protvino on behalf of the LHCb collaboration. LHCb detector status Key measurements LHCb upgrade issues Conclusions. LHCb: A Large Hadron Collider experiment for Precision Measurements of CP Violation and Rare Decays

toviel
Download Presentation

LHCb: status and perspectives

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LHCb: status and perspectives Yu. Guz, IHEP, Protvino on behalf of the LHCb collaboration LHCb detector status Key measurements LHCb upgrade issues Conclusions

  2. LHCb: A Large Hadron Collider experiment for Precision Measurements of CP Violation and Rare Decays >700 physicists, 50 institutes, 15 countries ATLAS CMS ALICE

  3. - b b bb angular distribution PT of B-hadron 100μb 230μb Pythia η of B-hadron LHCb experiment b LHC: √s=14 TeV, σinelastic~80mb, σ(bb)~0.5mbThe bb production is sharply peaked forward-backward. LHCb is a single arm detector 1.9<|η|<4.9 b • B hadron signature: particles with high PT (few GeV); displaced vertex (~1cm from primary vertex) • Reconstruction of B decays is based on: • good mass resolution • excellent particle id to reject background • good proper time resolution to resolve B0S oscillations

  4. a beam-gas event 10/09/08 is ready to take data ! The LHCb detector : installation is complete Muon det Calo’s RICH-2 Magnet OT+IT RICH-1 VELO

  5. BsDs(KKπ)K ε(KK) : 97% ε(πK) : 5% proper time resolution ~ 40 fs Eff. mass resolution ~ 20 MeV LHCb detector performance • Detailed Geant4 simulation • proper time resolution ~ 40 fs • effective mass resolution ~ 20 MeV • good K/π separation up to ~60 GeV

  6. LHCb operation at LHC Inelastic pp interactions σ~ 80 mb Bunch crossing frequency: 40 MHz Design LHC luminosity 1034 cm-2s-1 Nominal LHCb luminosity: 2∙1032 cm-2s-1 (appropriate focusing of the beam) Expect ≥2 fb-1 / year

  7. LHCb trigger L0, HLT and L0×HLT efficiency L0 Trigger: hardware, 4 μsec latency High ET (h>3.5 GeV; e, γ>2.5 GeV; μ, μμ>1GeV) Pileup VETO Output rate ~1 MHz High Level Trigger: software, two stages: HLT1 and HLT2 HLT1: confirm L0 objects, with T, VELO, optionally IP cuts …output ~ 30 kHz HLT2: full reconstruction, exclusive and inclusive candidates Output 2 kHz  storage, event size ~35 kB

  8. Tag Bd % Bs % Muon 1.1 1.5 Electron 0.4 0.7 Kaon opp.side 2.1 2.3 Jet/ Vertex Charge 1.0 1.0 Same side p/p/K 0.7 (pp) 3.5(K) Combined (Neural Net) ~ 5.1 ~9.5 Flavour tagging e-- Qvertex ,QJet Opposite side • High Pt leptons • K± from b → c → s • Vertex charge • Jet charge K- B0opposite D PV Bs0signal K K K+ Same side • Fragmentation K± accompanying Bs • π± from B** → B(*) π± Effective tagging efficiency:  εD2= ε(1-2ω)2 ε: tagging efficiency ω: wrong tag fraction

  9. LHCb key measurements • CP-violation • φS • γ in trees • γ in loops • rare B decays • BS μμ • B  K*μμ • photon polarization in radiative penguin decays • charm physics • Mixing • CP violation • other • τ 3μ (analysis is ongoing) • ...

  10. Physics program 2008 (beginning of 2009?): Lumi ~1031 cm-2s-1 10 TeV ~108 sample of minimum bias; L0+proto-HLT trigger, collect ~ 5 pb-1 Calibration, alignment, minimum bias physics, charmonium production 2009: Lumi 2 1032 cm-2s-1 14 TeV L0 + HLT , collect ~ 0.5..1 fb-1 B Physics: calibration CP (sin2β, Δms ); key measurements (βs, Bsμμ, …) 2010-2013: Luminosity 2-5 1032 cm-2s-1 collect total of ~10 fb-1 Full physics program Phase I 2013+: Upgrade proposed to run at 2 1033 cm-2s-1. Collect ~ 100 fb-1

  11. CP violation

  12. φS measurement Key measurement for 2009 φS is small in SM: φS =-2βS =-2λ2η≈ -0.036 sensitive probe for New Physics: φS = φSSM + φSNP Measure from time dependent CP asymmetry in bccs (BS  J/ψφ, BS  J/ψη(η’), BS  ηCφ, BS  DSDS, …) “golden mode” BS  J/ψφ : high BR (~130k per 2 fb-1) Tevatron results: D0 2bs= - 0.57 + 0.24-0.30 with with 2.8 fb-1 CDF 2bs = [0.32,2.82] @ 68%CL with 1.35 fb-1

  13. φS measurement J/ψφ is not a pure CP eigenstate: angular analysis is necessary to separate CP-odd and CP-even The BSM effect in φS can be discovered or excluded with 2008/2009 LHCb data Other bccs processes (J/ψη, ηCφ, DSDS) can be added: angular analysis not needed, but smaller statistics

  14. angle γ Least constrained by direct measurementsKey measurement of LHCb Comparison of γ measurement in trees with fitted values, as well as with measurement in loops, is a sensitive probe of New Physics

  15. angle γ 1 From tree amplitudes :BS DSK Time dependent CP asymmetry From tree amplitudes:B±DK±, B0DK* ADS: Use doubly Cabibbo-suppressed D0 decays, e.g. D0  K+π- GLW: Use CP eigenstates of D(*)0 decay, e.g. D0  K+K- /π+π–, Ksπ0 Dalitz: Use Dalitz plot analysis of 3-body D0 decays, e.g. Ks π+ π- 2 3 From penguins :B  h h Sensitive to New Physics  compare “effective” γ with tree measurements

  16. γ from BSDSK • interference between tree level decays via mixing • insensitive to New Physics • Measures  + 2s (s from Bs  J/) • Main background Bs  Ds • 10 times higher branching ratio • suppressed using PID by RICH

  17. γ from BSDSK BsDsK, Bs Dshave same topology.Combine samples to fitΔms, ΔΓs and mistag rate together with CP phaseγ+φs. 5 years data: Bs→Ds-p+ Bs→ Ds-K+ (Dms = 20) Sensitivity at 2 fb-1 s(γ+φs) = 9o–12o s(ms) = 0.007 ps-1

  18. γ from BDK ADS method: Measure relative rates of B→ D(Kπ) K and B→ D(Kπ) K • Two interfering tree B-diagrams, one colour-suppressed (rB ~0.077) • D0, anti-D0 reconstructed in same final state • Two interfering tree D-diagrams, one Double Cabibbo-suppressed (rDKπ~0.06) Colour allowed Colour suppressed Double Cabbibo suppressed Cabbibo favoured Reversed suppression of the D decays relative to the B decays results in more equal amplitudes : large interference effects

  19. favoured colour suppressed γ from BDK s(g) = 5o to 13o depending on strong phases. s(g) Also under study: B± → DK±with D → Kspp 80-12o B± → DK±with D → KK pp 18o B0 → DK*0with D → KK, Kp, pp 6o -12o B± → D*K±with D → KK, Kp, pp (high background) Dalitz analyses Overall: expect precision of s(g) = 5owith 2 fb-1 of data

  20. Rare B decays

  21. BSμμ Strongly suppressed in SM by helicity: Br= (3.35 ± 0.32) x 10-9 Sensitive to NP models with S or P coupling MSSM: Br ~ tan6β/MA4 . • Current limits from Tevatron: • CDF BR < 4.7 10-8 90 % CL • D0 BR < 7.5 10-8 90 % CL LHCb sensitivity (SM branching ratio) : • 0.1 fb-1 BR < 10-8 • 0.5 fb-1 BR < SM expectation • 2 fb–1: 3 evidence • 10 fb–1: 5 observation

  22. Bsφγ In SM photon from bsγ is left-handed, from bsγ right-handed  φγ final states in B and B do not interfere  CP asymmetry in mixing cannot occur Measuring time-dependent CP asymmetry is a probe for NP b   (L) + (ms/mb)  (R) In SM: Adir 0, Amix  sin 2ψ sin 2β AΔ  sin 2ψcos 2β tan ψ = |b→sγR| / | b→sγL| cos 2β 1 Statistical precision after 1 year (2 fb-1) s(Adir ) = 0.11 , s (Amix ) = 0.11(requires tagging) s (AD) = 0.22(no tagging required)

  23. Zero crossing point of forward-backward asymmetry AFB in θl angle, as a function of mμμ precisely computed in SM: s0SM(C7,C9)=4.39(+0.38-0.35) GeV2 • sensitive to NP contribution 2 fb-1 Afb(s)  s0 s(s0) = 0.5 GeV2 s = (m)2 [GeV2]  BdK*μμ • 2009: 0.5 fb-1 expect 2000 events • B factories total ~ 1000 events by now

  24. Charm & tau

  25. Dedicated D* trigger 2 charged tracks from a detached vertex with -700<(mππ-mD0)< 50 MeV; + another charged track matching the hypothesis of D*D0π decay (vertex, Δm) D0s are flavor tagged with π from D* decay • Two sources of D0s in LHCb: • from B decays • favoured by LHCb triggers • prompt production in primary interaction Estimated annual yields (per 2 fb-1) from B decays: D0K-π+ (right sign) 12.4 M D0K+π- (wrong sign) 46.5 k D0K+K- 1.6 M D0π+π- 0.5 M Similar amounts expected from prompt production

  26. LHCb prospects for Charm physics studies D0 mixing • Time-dependent D0 mixing with wrong-sign D0K+π- decays • Strong phase δ between DCS and CF amplitudes: (x,y)(x’,y’) • Lifetime ratio: mean lifetime (DK- π+) and CP even decay DK+K-(π+π-)yCP=y in absence of CP violation (φ=0) The mixing has been recently observed (Belle, BaBar, CDF) 0.26 0.27 x = 0.89± % LHCb sensitivities with 10 fb-1: σstat(x’2) ~ 6.4·10-5, σstat(y’) ~ 8.7·10-4;σstat(yCP)~ 4.9·10-4 0.17 0.18 y = 0.75± %

  27. Direct CP violation can be measured in D0KK lifetime asymmetry • ACP<10-3 in SM, up to 1% with New Physics • current HFAG average Belle, BaBar, CDF): ACP = -0.16 ± 0.23 LHCb prospects for Charm physics studies LHCb sensitivity with 10 fb-1: σstat(ACP) ~ 4.8·10-4

  28. background τ3μ σ=8.6 MeV τ3μ (preliminary) Present upper limit: Br(τ3μ) < 3.2·10-8 @90%CL (Belle) Br(τ3μ) < 5.3·10-8 @90%CL (BaBar) Preliminary analysis shows that at 2fb-1 LHCb can obtain upper limit of ~6·10-8 The result is not final: background estimate may change, event selection refined.

  29. Upgrade issues

  30. Sensitivities for 100 fb-1 Also studying Lepton Flavour Violation in  • 10 fb-1 will be collected by 2013 • φS measured to 0.023 • γ to 2 - 5o • BSμμobserved at 5σ level • many more excellent physics results • next step – collect 100fb-1 • Probe/measure NP at % level • have to work at > 1033cm-2s-1 • upgrade is necessary

  31. LHCb at higher luminosity • The L0 hadron trigger saturates the bandwidth (1 MHz) at 2·1032 cm-2s-1 • typical L0 efficiency for purely hadronic final states ~ 50% will drop with luminosity • apart from the trigger, the LHCb performance does not deteriorate significantly up to 1033 cm-2s-1 • A 40 MHz readout of all the detectors is the only way to achieve 1033. Introduce first level trigger on detached vertex on a CPU farm • LHC schedule • Phase 1: IR upgrade. Install new triplets β*=0.25m in IP1 and 5. Requires 8 month shutdown in 2012-2013 • Phase 2: inner detectors of ATLAS and CMS need to be replaced. 18 month shutdown in ~2017

  32. LHCb upgrade strategy • the main effort is to upgrade by 2014 all Frontend Electronics to 40 MHz readout. • perform also necessary upgrade of subdetectors • replace readout chips in the vertex detector (VELO) • RICHs: the readout chips are encapsulated inside photodetectors  replace all photodetectors ! • Tracking system: replace all Si sensors, as readout chips are bonded on hybrids • run from 2014 at 1033 cm-2s-1 until the Phase 2 shutdown. Reach 20 fb-1. • in 2017 upgrade the subdetectors for >2·1033 cm-2s-1 • fully rebuild vertex detector (pixels or 3D) • rebuild Outer Tracker, replace central part of EM calorimeter, … • run at highest possible luminosity for 5 years.

  33. Conclusions • The LHCb detector at LHC is commissioned and ready to take data • key measurements with 2009 data: • βS: precision ~0.04 • BSμμ : sensitivity ~ SM expectations • Full physics program in 2010-2013 at 10 fb-1: • Angle γ precision of ~5o with 2 fb-1 • search for New Physics in photon polarization in bsγ • precision measurement of AFB in BK*μμ • Charm physics: D0 mixing, direct CP violation in D0KK(ππ) • and much more… • 2013+: upgrade of the detector, aiming to reach 100 fb-1 at operating luminosity of 1033cm-2s-1 (and >2·1033 cm-2s-1 in 2017+)

  34. Backup

  35. τ3μ Event selection cuts per track: PT > 0.4 GeV IP()/IP > 3.0 dLL > -3 cuts per 3 vertex: 2 < 9 |V3-Vprim|/  > 3 Z3-Zprim > 0 cm IP()/IP < 3 Background rejection: 4.9·10-9 Per 2 fb-1 ~2200 bg evts expected FeldmanCousins upper limit 78.5 ev Corresponds to Br limit 6.1 ·10-8 Main source of τ: DS decays Per 2 fb-1 5.6·1010τ produced Signal efficiency: 2.3%

More Related