LHCb status and perspectives Yu Guz IHEP Protvino
LHCb: status and perspectives Yu. Guz, IHEP, Protvino on behalf of the LHCb collaboration 1. LHCb detector status 2. Key measurements 3. LHCb upgrade issues 4. Conclusions 1
LHCb: A Large CMS ATLAS ALICE Hadron Collider experiment for Precision Measurements of CP Violation and Rare Decays >700 physicists, 50 institutes, 15 countries 2
LHCb experiment - LHC: √s=14 Te. V, σinelastic~80 mb, σ(bb)~0. 5 mb The bb production is sharply peaked forwardbackward. b b b PT of B-hadron LHCb is a single arm detector 1. 9<|η|<4. 9 B hadron signature: particles with high PT (few Ge. V); displaced vertex (~1 cm 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 B 0 S oscillations b bb angular distribution 100μb 230μb Pythia η of B-hadron 3
ready to take data ! The LHCb detector : is installation is complete Muon det Calo’s RICH-2 OT+IT Magnet RICH-1 VELO a beam-gas event 10/09/08 5
LHCb detector performance Detailed Geant 4 simulation • proper time resolution ~ 40 fs Bs Ds(KKπ)K • effective mass resolution ~ 20 Me. V • good K/π separation up to ~60 Ge. V proper time resolution ~ 40 fs ε(K K) : 97% ε(π K) : 5% Eff. mass resolution ~ 20 Me. V 6
LHCb operation at LHC Inelastic pp interactions σ ~ 80 mb Bunch crossing frequency: 40 MHz Design LHC luminosity 1034 cm-2 s-1 Nominal LHCb luminosity: 2∙ 1032 cm-2 s-1 (appropriate focusing of the beam) Expect ≥ 2 fb-1 / year 7
LHCb trigger L 0, HLT and L 0×HLT efficiency L 0 Trigger: hardware, 4 μsec latency High ET (h>3. 5 Ge. V; e, γ>2. 5 Ge. V; μ, μμ>1 Ge. V) Pileup VETO Output rate ~1 MHz High Level Trigger: software, two stages: HLT 1 and HLT 2 HLT 1: confirm L 0 objects, with T, VELO, optionally IP cuts … output ~ 30 k. Hz HLT 2: full reconstruction, exclusive and inclusive candidates Output 2 k. Hz storage, event size ~35 k. B HLT rate Event type Physics 200 Hz Exclusive B decay candidates B (core programme) 600 Hz High mass dimuons J/ , b J/ X (lifetime unbiased) 300 Hz D* candidates Charm (mixing & CPV) 900 Hz Inclusive b (e. g. b ) B (data mining) 8
Flavour tagging e- B 0 opposite PV Same side Bs 0 signal K+ D Qvertex , QJet K- K K – Fragmentation K± accompanying Bs – π± from B** → B(*) π± Effective tagging efficiency: �� �� εD 2= ε(1 -2ω)2 ε : tagging efficiency ω: wrong tag fraction Opposite side – High Pt leptons – K± from b → c → s – Vertex charge – Jet charge 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 Same side p/ /K 0. 7 (p ) 3. 5(K) Combined (Neural Net) ~ 5. 1 ~9. 5
LHCb key measurements ► CP-violation ►charm physics ✔ φS ✔Mixing ✔ γ in trees ✔ CP violation ✔ γ in loops ► rare B decays ✔ BS μμ ✔ B K* μμ ►other ✔ τ 3μ (analysis is ongoing) ✔. . . ✔ photon polarization in radiative penguin decays 10
Physics program 2008 (beginning of 2009? ): Lumi ~1031 cm-2 s-1 10 Te. V ~108 sample of minimum bias; L 0+proto-HLT trigger, collect ~ 5 pb -1 Calibration, alignment, minimum bias physics, charmonium production 2009: Lumi 2 1032 cm-2 s-1 14 Te. V L 0 + HLT , collect ~ 0. 5. . 1 fb-1 B Physics: calibration CP (sin 2β, Δms ); key measurements (βs, Bs μμ, …) 2010 -2013: Luminosity 2 -5 1032 cm-2 s-1 collect total of ~10 fb-1 Full physics program Phase I 2013+: Upgrade proposed to run at 2 1033 cm-2 s-1. Collect ~ 100 fb-1 11
CP violation 12
φS measurement Key measurement for 2009 φS is small in SM: φS =-2βS =-2λ 2η ≈ -0. 036 sensitive probe for New Physics: φS = φSSM + φSNP Tevatron results: D 0 2 s= 0. 57 + 0. 24 -0. 30 with 2. 8 fb-1 CDF 2 s = [0. 32, 2. 82] @ 68%CL with 1. 35 fb-1 Measure from time dependent CP asymmetry in b ccs (BS J/ψ φ, BS J/ψ η(η’), BS ηCφ, BS DSDS, …) “golden mode” BS J/ψ φ : high BR (~130 k per 2 fb-1) 13
φS measurement J/ψ φ is not a pure CP eigenstate: angular analysis is necessary to separate CP-odd and CP-even Other b ccs processes (J/ψ η, ηCφ, DSDS) can be added: angular analysis not needed, but smaller statistics The BSM effect in φS can be discovered or excluded with 2008/2009 LHCb data 14
angle γ Measured values 90% CL Fit results 90% CL α 87. 5 +31. 1 -10. 2 90. 7 + 16. 8 - 5. 4 β 21. 5 +2. 0 -1. 9 21. 7 + 2. 0 - 1. 8 γ 76. 8 +52. 7 -50. 4 67. 6 + 5. 3 - 15. 9 Least constrained by direct measurements Key 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 From tree amplitudes : BS DSK Time dependent CP asymmetry From tree amplitudes: B± DK±, B 0 DK* ADS: Use doubly Cabibbo-suppressed D 0 decays, e. g. D 0 K+πGLW: Use CP eigenstates of D(*)0 decay, e. g. D 0 K+K- / π+π–, Ksπ0 Dalitz: Use Dalitz plot analysis of 3 -body D 0 decays, e. g. Ks π+ π- 1 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 Channel Yield 2 fb-1 B/S (90% C. L. ) BS DSK 6. 2 k [0. 08 -0. 4] BS DSp 140 k [0. 08 -0. 3] 17
γ from BS DSK Bs Ds. K, Bs Ds have same topology. Combine samples to fit Δms, ΔΓs and mistag rate together with CP phase γ+φs. 5 years data: Bs→ Ds- + Bs→ Ds-K+ ( ms = 20) Sensitivity at 2 fb-1 s(γ+φs) = 9 o– 12 o 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 (r ~0. 077) B 0 0 ● D , anti-D reconstructed in same final state ●Two interfering tree D-diagrams, one Double Cabibbo-suppressed (r. DKπ�~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
γ from B DK favoured colour suppressed Channel Yield (2 fb-1) B/S B → D(hh) K 7. 8 k 1. 8 B → D(Kp) K , Favoured 56 k 0. 6 B → D(Kp) K , Suppressed 0. 71 k 2 B → D(K 3 p) K, Favoured 62 k 0. 7 B → D(K 3 p) K, Suppressed 0. 8 k 2 Also under study: B± → DK± with D → Ks pp B± → DK± with D → KK pp B 0 → DK*0 with D → KK, Kp, pp B± → D*K± with D → KK, Kp, pp ( ) = 5 o to 13 o depending on strong phases. 80 12 o Dalitz analyses o 18 Overall: expect precision of 6 o 12 o ( ) = 5 o with 2 fb-1 of data (high background) 20
Rare B decays 24
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 ~ tan 6β/MA 4. • Current limits from Tevatron: • CDF BR < 4. 7 10 -8 90 % CL • D 0 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 25
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 Channel Yield B/S AΔ sin 2ψ cos 2β (2 fb-1) tan ψ = |b→sγR| / | b→sγL| Bs→fg 11 k <0. 55 cos 2β 1 Statistical precision after 1 year (2 fb-1) (Adir ) = 0. 11 , (Amix ) = 0. 11 (requires tagging) (A ) = 0. 22 (no tagging required) 26
Afb(s) Bd K*μμ ● Zero crossing point of forward-backward asymmetry AFB in θl angle, as a function of mμμ precisely computed in SM: s 0 SM(C 7, C 9)=4. 39(+0. 38 -0. 35) Ge. V 2 ● sensitive to NP contribution 2 fb-1 s 0 Channel Bs→K* + – (s 0) = 0. 5 Ge. V 2 s = (m )2 [Ge. V 2] Yield (2 fb-1) BG (2 fb-1) 7200+-2200 (BR) 1770+-310 • 2009: 0. 5 fb-1 expect 2000 events • B factories total ~ 1000 events by now 27
Charm & tau 28
Dedicated D* trigger 2 charged tracks from a detached vertex with -700<(mππ-m. D 0)< 50 Me. V; + another charged track matching the hypothesis of D* D 0π decay (vertex, Δm) D 0 s are flavor tagged with π from D* decay Two sources of D 0 s in LHCb: q from B decays Ø favoured by LHCb triggers q prompt production in primary interaction Estimated annual yields (per 2 fb-1) from B decays: D 0 K-π+ (right sign) 12. 4 M D 0 K+π- (wrong sign) 46. 5 k D 0 K+K 1. 6 M D 0 π+π0. 5 M Similar amounts expected from prompt production 29
LHCb prospects for Charm physics studies D 0 mixing q Time-dependent D 0 mixing with wrongsign D 0 K+π- decays § Strong phase δ between DCS and CF amplitudes: (x, y) (x’, y’) q Lifetime ratio: mean lifetime (D K- π+) and CP even decay D K+K-(π+π-) The mixing has been recently observed (Belle, Ba. Bar, CDF) y. CP=y in absence of CP violation (φ=0) 0. 26 LHCb sensitivities with 10 fb-1: σstat(x’ 2) ~ 6. 4·10 -5, σstat(y’) ~ 8. 7·10 -4; σstat(y. CP)~ 4. 9·10 -4 x = 0. 89± 0. 27 % 0. 17 y = 0. 75± 0. 18 % 30
LHCb prospects for Charm physics studies q Direct CP violation can be measured in D 0 KK lifetime asymmetry § ACP<10 -3 in SM, up to 1% with New Physics § current HFAG average Belle, Ba. Bar, CDF): ACP = -0. 16 ± 0. 23 LHCb sensitivity with 10 fb-1: σstat(ACP) ~ 4. 8·10 -4 31
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 (Ba. Bar) Preliminary analysis shows that at 2 fb-1 LHCb can obtain upper limit of ~6·10 -8 The result is not final: background estimate may change, event selection refined. background τ 3μ σ=8. 6 Me. V 32
Upgrade issues 33
10 fb-1 will be collected by 2013 Sensitivities for 100 fb-1 • φS measured to 0. 023 • γ to 2 - 5 o • BS μμ observed at 5σ level • many more excellent physics results next step – collect 100 fb-1 Probe/measure NP at % level • have to work at > 1033 cm-2 s-1 • upgrade is necessary Also studying Lepton Flavour Violation in 34
LHCb at higher luminosity • The L 0 hadron trigger saturates the bandwidth (1 MHz) at 2·1032 cm-2 s-1 • typical L 0 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-2 s-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. 25 m in IP 1 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 35
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-2 s-1 until the Phase 2 shutdown. Reach 20 fb-1. in 2017 upgrade the subdetectors for >2·1033 cm-2 s-1 • fully rebuild vertex detector (pixels or 3 D) • rebuild Outer Tracker, replace central part of EM calorimeter, … • run at highest possible luminosity for 5 years. 36
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 ~5 o with 2 fb-1 • search for New Physics in photon polarization in b sγ • precision measurement of AFB in B K*μμ • Charm physics: D 0 mixing, direct CP violation in D 0 KK(ππ) • and much more… • 2013+: upgrade of the detector, aiming to reach 100 fb -1 at operating luminosity of 1033 cm-2 s-1 (and >2·1033 cm-2 s-1 in 2017+) 37
Backup 38
τ 3μ Event selection cuts per track: ❚ PT ❚ IP( )/ IP ❚ d. LL cuts per 3 vertex: ❚ 2 ❚ |V 3 -Vprim|/ ❚ Z 3 -Zprim ❚ IP( )/ IP > 0. 4 Ge. V > 3. 0 > -3 < > > < 9 3 0 cm 3 Main source of τ: DS decays Background rejection: 4. 9·10 -9 Per 2 fb-1 5. 6·1010 τ produced Per 2 fb-1 ~2200 bg evts expected Signal efficiency: 2. 3% Feldman. Cousins upper limit 78. 5 ev Corresponds to Br limit 6. 1 ·10 -8 39
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