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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

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LHCb: status and perspectives

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  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%

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