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LHCb: status and perspectives

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Presentation on theme: "LHCb: status and perspectives"— 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 LHCb experiment - b bb angular distribution
LHC: √s=14 TeV, σinelastic~80mb, σ(bb)~0.5mb The bb production is sharply peaked forward-backward. LHCb is a single arm detector 1.9<|η|<4.9 b b b Pythia 100μb 230μb η of B-hadron PT of B-hadron 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 The LHCb detector Main components: silicon strip vertex detector
magnet tracker stations (inner area: silicon; outer: straw tubes) two RICH detectors EM calorimeter with preshower muon system

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

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

7 Nominal LHCb luminosity: 2∙1032 cm-2s-1
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

8 J/, bJ/X (lifetime unbiased)
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 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m) B (data mining)

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

10 LHCb key measurements CP-violation charm physics φS Mixing 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) ...

11 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 ~ fb-1 B Physics: calibration CP (sin2β, Δms ); key measurements (βs, Bsμμ, …) : 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

12 CP violation

13 φS measurement Key measurement for 2009
φS is small in SM: φS =-2βS =-2λ2η ≈ sensitive probe for New Physics: φS = φSSM + φSNP 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 (~130k per 2 fb-1) Tevatron results: D bs= with with 2.8 fb-1 CDF 2bs = 68%CL with 1.35 fb-1

14 φS measurement J/ψ φ 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/ψ η, ηCφ, DSDS) can be added: angular analysis not needed, but smaller statistics

15 angle γ Measured values 90% CL Fit results α β γ 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

16 angle γ From tree amplitudes : BS  DSK Time dependent CP asymmetry
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

17 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 [ ] BSDSp 140 k [ ]

18 γ from BSDSK BsDsK, 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-p+ Bs→ Ds-K+ (Dms = 20) Sensitivity at 2 fb-1 s(γ+φs) = 9o–12o s(ms) = ps-1

19 γ from BDK Colour allowed Colour suppressed Double Cabbibo suppressed
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

20 γ from BDK s(g) = 5o with 2 fb-1 of data Channel Yield (2 fb-1) B/S
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 0.71k 2 B → D(K3p) K, Favoured 62k 0.7 B → D(K3p) K, Suppressed 0.8k s(g) = 5o to 13o depending on strong phases. s(g) Also under study: B± → DK± with D → Ks pp o B± → DK± with D → KK pp o B0 → DK*0 with D → KK, Kp, pp 6o -12o B± → D*K± with D → KK, Kp, pp (high background) Dalitz analyses Overall: expect precision of s(g) = 5o with 2 fb-1 of data

21 γ from Bhh Bd/s /K /K Bd/s Measure time-dependent CP asymmetries for B0   and Bs   ACP(t) = Adir cos(m t) + Amix sin(m t) Extract four asymmetries: Adir(B0  ) = f1(d, , ) dei = ratio of penguin and tree Amix(B0  ) = f2(d, , ) amplitudes in B0   Adir(Bs  ) = f3(d’, ’, ) d’ei’ = ratio of penguin and tree Amix(Bs  ) = f4(d’, ’, s) amplitudes in Bs   Assume U-spin flavour symmetry (d  s) d = d’ and  = ’ Take fd from BdJ/ Ks and fs from BSJ/  solve for g  observables , 3 unknowns

22 γ from Bhh s(g) ~ 10o with 2 fb-1 s(g) ~ 5o with 10 fb-1 Channel
NO PID WITH RICH PID s(g) ~ 10o with 2 fb-1 s(g) ~ 5o with 10 fb-1 Channel Yield (2 fb-1) B/S Bpp 36k 0.5 BsKK 0.15

23 angle γ

24 Rare B decays

25 BSμμ LHCb sensitivity (SM branching ratio) : 0.1 fb-1 BR < 10-8
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 < % CL D0 BR < % 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

26 Bsφγ In SM: Adir  0, Amix  sin 2ψ sin 2β AΔ  sin 2ψ cos 2β
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 2ψ cos 2β tan ψ = |b→sγR| / | b→sγL| cos 2β  1 Channel Yield (2 fb-1) B/S Bs→fg 11k <0.55 Statistical precision after 1 year (2 fb-1) s(Adir ) = , s (Amix ) = (requires tagging) s (AD) = (no tagging required)

27 BdK*μμ s0 2009: 0.5 fb-1 expect 2000 events
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( ) GeV2 sensitive to NP contribution BdK*μμ s = (m)2 [GeV2]  2 fb-1 Afb(s)  s0 s(s0) = 0.5 GeV2 Channel Yield (2 fb-1) BG (2 fb-1) Bs→K*m+ m– (BR) 2009: 0.5 fb-1 expect 2000 events B factories total ~ 1000 events by now

28 Charm & tau

29 Dedicated D* trigger D0s are flavor tagged with π from D* decay
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) M D0K+π- (wrong sign) k D0K+K M D0π+π M Similar amounts expected from prompt production

30 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) x = 0.89± % 0.26 0.27 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± %

31 LHCb prospects for Charm physics studies
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 = ± 0.23 LHCb sensitivity with 10 fb-1: σstat(ACP) ~ 4.8·10-4

32 τ3μ (preliminary) Present upper limit:
Br(τ3μ) < (Belle) Br(τ3μ) < (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. σ=8.6 MeV τ3μ background

33 Upgrade issues

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

35 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 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 Phase 2: inner detectors of ATLAS and CMS need to be replaced. 18 month shutdown in ~2017

36 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.

37 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 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+)

38 Backup

39 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 5.6·1010 τ produced Signal efficiency: 2.3%

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