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1 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.

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Presentation on theme: "1 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."— Presentation transcript:

1 1 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

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

3 3 LHCb experiment Pythia 100μb 230μb η of B-hadron P T of B-hadron bb angular distribution - b b b b B hadron signature: particles with high P T (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 B 0 S oscillations LHC: √s=14 TeV, σ inelastic ~80mb, σ(bb)~0.5mb The bb production is sharply peaked forward- backward. LHCb is a single arm detector 1.9<|η|<4.9

4 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 5 is ready to take data ! VELO Muon det Calo’s RICH-2Magnet OT+ITRICH-1 The LHCb detector : installation is complete a beam-gas event 10/09/08

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

7 7 LHCb operation at LHC Bunch crossing frequency: 40 MHz Design LHC luminosity cm -2 s -1 Nominal LHCb luminosity: 2∙10 32 cm -2 s -1 (appropriate focusing of the beam) Expect ≥2 fb -1 / year Inelastic pp interactions σ ~ 80 mb

8 8 LHCb trigger L0, HLT and L0×HLT efficiency HLT rate Event typePhysics 200 HzExclusive B decay candidates B (core programme) 600 HzHigh mass dimuons J/ , b  J/  X (lifetime unbiased) 300 HzD* candidatesCharm (mixing & CPV) 900 HzInclusive b (e.g. b  ) B (data mining) L0 Trigger: hardware, 4 μsec latency High E T (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

9 K+K+ Q vertex,Q Jet PV e -   - B s 0 signal D K  KK K-K- B 0 opposite Opposite side –High Pt leptons –K ± from b → c → s –Vertex charge –Jet charge Same side –Fragmentation K ± accompanying B s – π ± from B ** → B (*) π ± ~ (K) B s % ~ (p  ) B d % Same side p/  /K Combined (Neural Net) Jet/ Vertex Charge Kaon opp.side Electron Muon Tag Effective tagging efficiency:   εD 2 = ε(1-2ω) 2 ε : tagging efficiency ω: wrong tag fraction Flavour tagging

10 10 LHCb key measurements ► CP-violation ✔ φ S ✔ γ in trees ✔ γ in loops ► rare B decays ✔ B S  μμ ✔ B  K * μμ ✔ photon polarization in radiative penguin decays ► charm physics ✔ Mixing ✔ CP violation ► other ✔ τ  3μ (analysis is ongoing) ✔...

11 (beginning of 2009?): Lumi ~10 31 cm -2 s TeV ~10 8 sample of minimum bias; L0+proto-HLT trigger, collect ~ 5 pb -1 Calibration, alignment, minimum bias physics, charmonium production 2009: Lumi 2  cm -2 s TeV L0 + HLT, collect ~ fb -1 B Physics: calibration CP (sin2β, Δm s ); key measurements (β s, B s  μμ, …) : Luminosity 2-5  cm -2 s -1 collect total of ~10 fb -1 Full physics program Phase I 2013+: Upgrade proposed to run at 2  cm -2 s -1. Collect ~ 100 fb -1 Physics program

12 12 CP violation

13 13 Key measurement for 2009 φ S is small in SM: φ S =-2β S =-2λ 2 η ≈ sensitive probe for New Physics: φ S = φ S SM + φ S NP Measure from time dependent CP asymmetry in b  ccs (B S  J/ψ φ, B S  J/ψ η(η’), B S  η C φ, B S  D S D S, …) “golden mode” B S  J/ψ φ : high BR (~130k per 2 fb -1 ) φ S measurement Tevatron results: D0  s =  with with 2.8 fb -1 CDF  s = 68%CL with 1.35 fb -1

14 14 φ S measurement The BSM effect in φ S can be discovered or excluded with 2008/2009 LHCb data 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, η C φ, D S D S ) can be added: angular analysis not needed, but smaller statistics

15 15 angle γ Measured values 90% CL Fit results 90% CL 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 From tree amplitudes : B S  D S K 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 + π - GLW: Use CP eigenstates of D (*)0 decay, e.g. D 0  K + K - / π + π –, K s π 0 Dalitz: Use Dalitz plot analysis of 3-body D 0 decays, e.g. K s π + π - From penguins : B  h h Sensitive to New Physics  compare “effective” γ with tree measurements angle γ

17 17 interference between tree level decays via mixing insensitive to New Physics Measures  + 2  s (  s from B s  J/  ) Main background B s  D s  10 times higher branching ratio suppressed using PID by RICH ChannelYield 2 fb -1 B/S (90% C.L.) BSDSKBSDSK6.2 k[ ] BSDSBSDS 140 k[ ] γ from B S  D S K

18 18 5 years data: B s → D s -   B s → D s - K +  m s = 20) B s  D s K, B s  D s have same topology. Combine samples to fit Δm s, ΔΓ s and mistag rate together with CP phase γ+φ s. Sensitivity at 2 fb -1 s(γ+φ s ) = 9 o –12 o s(  m s ) = ps -1 γ from B S  D S K

19 19 ADS method: Measure relative rates of B  → D(Kπ) K  and B  → D(Kπ) K  ● Two interfering tree B-diagrams, one colour-suppressed (r B ~0.077) ● D 0, anti-D 0 reconstructed in same final state ● Two interfering tree D-diagrams, one Double Cabibbo-suppressed (r D Kπ  ~0.06) Colour allowed Double Cabbibo suppressed Colour suppressed Cabbibo favoured Reversed suppression of the D decays relative to the B decays results in more equal amplitudes : large interference effects γ from B  DK

20 20 favoured colour suppressed ChannelYield (2 fb -1 )B/S B → D(hh) K 7.8 k1.8 B → D(K  ) K, Favoured56 k0.6 B → D(K  ) K, Suppressed0.71k2 B → D(K3  ) K, Favoured62k0.7 B → D(K3  ) K, Suppressed0.8k2  (  ) = 5 o to 13 o depending on strong phases. Also under study: B ± → DK ± with D → K s     B ± → DK ± with D → KK   B 0 → DK* 0 with D → KK, K     B ± → D*K ± with D → KK, K  (high background) Overall: expect precision of  (  ) = 5 o with 2 fb -1 of data Dalitz analyses  (  ) γ from B  DK

21 21 B d/s  /K B d/s Assume U-spin flavour symmetry (d  s) d = d’ and  =  ’ Take  d  from B d  J/  K s and  s from B S  J/   solve for   observables, 3 unknowns Measure time-dependent CP asymmetries for B 0      and B s      A CP (t) = A dir cos(  m t) + A mix sin(  m t) Extract four asymmetries: A dir (B 0      ) = f 1 (d, ,  ) de i  = ratio of penguin and tree A mix (B 0      ) = f 2 (d, ,  ) amplitudes in B 0      A dir (B s      ) = f 3 (d’,  ’,  ) d’e i  ’ = ratio of penguin and tree A mix (B s      ) = f 4 (d’,  ’,  s ) amplitudes in B s      γ from B  hh

22 22   ~ 10 o with 2 fb -1   ~ 5 o with 10 fb -1 ChannelYield (2 fb -1 ) B/S B   36k0.5 B s  KK36k0.15 WITH RICH PID NO PID γ from B  hh

23 23 angle γ

24 24 Rare B decays

25 25 B S  μμ Strongly suppressed in SM by helicity: Br= (3.35 ± 0.32) x Sensitive to NP models with S or P coupling MSSM: Br ~ tan 6 β/M A 4. Current limits from Tevatron: CDF BR < % CL D0 BR < % CL LHCb sensitivity (SM branching ratio) : 0.1 fb -1 BR < fb -1 BR < SM expectation 2 fb –1 : 3  evidence 10 fb –1 : 5  observation

26 26 B s  φγ b   (L) + (m s /m b )   (R) 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 In SM: A dir  0, A mix  sin 2ψ sin 2β A Δ  sin 2ψ cos 2β tan ψ = |b → sγ R | / | b → sγ L | cos 2β  1 ChannelYield (2 fb -1 ) B/S Bs →  11k<0.55 Statistical precision after 1 year (2 fb -1 )  (A dir ) = 0.11,  (A mix ) = 0.11  (requires tagging)  (A  ) = 0.22 (no tagging required)

27 27 B d  K * μμ 2009: 0.5 fb-1 expect 2000 events B factories total ~ 1000 events by now ChannelYield (2 fb -1 )BG (2 fb -1 ) Bs → K*  +  – (BR) ● Zero crossing point of forward-backward asymmetry A FB in θ l angle, as a function of m μμ precisely computed in SM: s 0 SM (C 7,C 9 )=4.39( ) GeV 2 ● sensitive to NP contribution s = (m  ) 2 [GeV 2 ]  2 fb -1 A fb (s)  s0s0  (s 0 ) = 0.5 GeV 2

28 28 Charm & tau

29 29 2 charged tracks from a detached vertex with -700<(m ππ -m D0 )< 50 MeV; + another charged track matching the hypothesis of D*  D 0 π decay (vertex, Δm) D 0 s are flavor tagged with π from D * decay Two sources of D 0 s in LHCb:  from B decays  favoured by LHCb triggers  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 D0  K+K- 1.6 M D0  π + π M Similar amounts expected from prompt production Dedicated D* trigger

30 30 LHCb prospects for Charm physics studies D 0 mixing  Time-dependent D 0 mixing with wrong- sign D 0  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 - ) y CP =y in absence of CP violation (φ=0) The mixing has been recently observed (Belle, BaBar, CDF) x = 0.89± % y = 0.75± % LHCb sensitivities with 10 fb -1 : σ stat (x’ 2 ) ~ 6.4·10 -5, σ stat (y’) ~ 8.7·10 -4 ; σ stat (y CP )~ 4.9·10 -4

31 31 LHCb prospects for Charm physics studies  Direct CP violation can be measured in D 0  KK lifetime asymmetry  A CP <10 -3 in SM, up to 1% with New Physics  current HFAG average Belle, BaBar, CDF): A CP = ± 0.23 LHCb sensitivity with 10 fb -1 : σ stat (A CP ) ~ 4.8·10 -4

32 32 Present upper limit: Br(τ  3μ) < 3.2·10 (Belle) Br(τ  3μ) < 5.3·10 (BaBar) σ=8.6 MeV τ3μτ3μ background 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. τ  3μ (preliminary)

33 33 Upgrade issues

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

35 35 The L0 hadron trigger saturates the bandwidth (1 MHz) at 2·10 32 cm -2 s -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 cm -2 s -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 LHCb at higher luminosity

36 36 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 cm -2 s -1 until the Phase 2 shutdown. Reach 20 fb -1. in 2017 upgrade the subdetectors for >2·10 33 cm -2 s -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. LHCb upgrade strategy

37 37 Conclusions The LHCb detector at LHC is commissioned and ready to take data key measurements with 2009 data: β S : precision ~0.04 B S  μμ : sensitivity ~ SM expectations Full physics program in 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 A FB 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 cm -2 s -1 (and >2·10 33 cm -2 s -1 in 2017+)

38 38 Backup

39 39 τ  3μ Event selection cuts per track: ❚ P T > 0.4 GeV ❚ IP(  )/  IP > 3.0 ❚ dLL  > -3 cuts per 3  vertex: ❚  2< 9 ❚ |V 3  -V prim |/  > 3 ❚ Z 3  -Z prim > 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: D S decays Per 2 fb ·10 10 τ produced Signal efficiency: 2.3%


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