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LHCb Physics Programme Marcel Merk For the LHCb Collaboration May 26, 2008 Contents: The LHCb Experiment Physics Programme: CP Violation Rare Decays CERN.

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Presentation on theme: "LHCb Physics Programme Marcel Merk For the LHCb Collaboration May 26, 2008 Contents: The LHCb Experiment Physics Programme: CP Violation Rare Decays CERN."— Presentation transcript:

1 LHCb Physics Programme Marcel Merk For the LHCb Collaboration May 26, 2008 Contents: The LHCb Experiment Physics Programme: CP Violation Rare Decays CERN Theory Institute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008

2 LHC A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays CMS ALICE ATLAS LHCb CERN s = 14 TeV LHCb: L =2-5 x cm -2 s -1 bb = 500 b inel / bb = 160 => 1 year = 2 fb -1 b b b b

3 The LHCb Detector VELO Muon det Calos RICH-2Magnet OTRICH-1 VELO Muon det Calos RICH-2Magnet OT+ITRICH-1 Installation of major structures is complete

4 4 A walk through the LHCb spectrometer…

5 B-Vertex Measurement Vertex Locator (Velo) Silicon strip detector with ~ 5 m hit resolution 30 m IP resolution Vertexing: Impact parameter trigger Decay distance (time) measurement DsDs BsBs K K K d 47 m 144 m 440 m Primary vertex Decay time resolution = 40 fs ) ~40 fs Example: Bs Ds K

6 6 Momentum and Mass measurement Momentum meas.: Mass resolution for background suppression

7 7 Momentum and Mass measurement Momentum meas.: Mass resolution for background suppression btbt BsBs K K K DsDs Primary vertex Bs Ds K Bs Ds Mass resolution ~14 MeV

8 8 Particle Identification RICH2: 100 m3 CF4 n= RICH: K/ identification using Cherenkov light emission angle RICH1: 5 cm aerogel n= m 3 C 4 F 10 n=1.0014

9 9 Particle Identification RICH2: 100 m3 CF4 n= RICH: K/ identification; eg. distinguish D s and D s K events. RICH1: 5 cm aerogel n= m 3 C 4 F 10 n= Cerenkov light emission angle btbt BsBs K K,K DsDs Primary vertex K K : ± 0.06% K : 5.15 ± 0.02% Bs Ds K

10 10 LHCb calorimeters e h Calorimeter system : Identify electrons, hadrons, neutrals Level 0 trigger: high E T electron and hadron btbt BsBs K K K DsDs Primary vertex

11 11 LHCb muon detection Muon system: Level 0 trigger: High Pt muons Flavour tagging: D 2 = (1-2w) 2 6% b tag BsBs K K K DsDs Primary vertex

12 12 LHCb trigger HLT rate Event typePhysics 200 HzExclusive B candidates B (core program) 600 HzHigh mass di- muons J/, b J/ X (unbiased) 300 HzD* candidatesCharm (mixing & CPV) 900 HzInclusive b (e.g. b ) B (data mining) HLT: high IP, high p T tracks [software] then full reconstruction of event 40 MHz 1 MHz 2 kHz L0: high p T (, e,, h) [hardware, 4 s] Storage (event size ~ 50 kB) Detector L0, HLT and L0×HLT efficiency Note: decay time dependent efficiency: eg. Bs Ds K Proper time [ps] Efficiency btbt BsBs K K K DsDs Primary vertex 12

13 13 Measuring time dependent decays btbt BsBs K K DsDs Primary vertex Measurement of Bs oscillations: B s ->D s – (2 fb -1 ) Experimental Situation: Ideal measurement (no dilutions)

14 14 Measuring time dependent decays btbt BsBs K K DsDs Primary vertex B s ->D s – (2 fb -1 ) Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution

15 15 Measuring time dependent decays btbt BsBs K K DsDs Primary vertex B s ->D s – (2 fb -1 ) Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution + Realistic decay time resolution

16 16 Measuring time dependent decays btbt BsBs K K DsDs Primary vertex B s ->D s – (2 fb -1 ) Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging + Realistic decay time resolution + Background events

17 17 Measuring time dependent decays btbt BsBs K K DsDs Primary vertex Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution + Realistic decay time resolution + Background events + Trigger and selection acceptance Two equally important aims for the experiment: Limit the dilutions: good resolution, tagging etc. Precise knowledge of dilutions B s ->D s – (2 fb -1 ) Measurement of Bs oscillations:

18 18 Expected Performance: GEANT MC simulation Used to optimise the experiment and to test physics sensitivities Simulation software: Pythia+EvtGen GEANT simulation Detector response Reconstruction software: Event Reconstruction Decay Selection Trigger/Tagging Physics Fitting

19 Physics Programme LHCb is a heavy flavour precision experiment searching for new physics in CP-Violation and Rare Decays CP Violation Rare Decays 19

20 CP Violation – LHCb Program Bd triangle Bs triangle CP Program: Is CKM fully consistent for trees, boxes and penguins? measurements from trees measurement from penguins 3. s from the box: Bs mixing phase 4. s in penguins b q1q1 d, s q2q2 W g d (s) q q W bu,c,t b q q b W+W+ W V* ib V iq V* ib 20

21 1.a + s from trees: B s D s K Time dependent CP violation in interference of b c and b u decays: BsBs BsBs BsBs BsBs Time 21 B s /B s D s – K + (10 fb -1 )

22 10 fb -1 data: B s D s - B s D s - K + m s = 20) Since same topology B s D s K, B s D s combine samples to fit ms, s and Wtag together with CP phase s. ChannelYield (2 fb-1) B/S (90% C.L.) Bs DsK6.2 k[ ] Bs Ds 140 k[ ] Use lifetime difference s to resolve some ambiguities (2 remain). BsDsKBsDsK s ) = 9 o –12 o Decay Time 22

23 B D and B sD s K ChannelYield (2 fb-1)B/S Bs D*(K ) 206 k<0.3 B->D 210 k0.3 B D(*) measures in similar way as Bs DsK More statistics, but smaller asymmetry No lifetime difference: 8 –fold ambiguity for solutions Invoking U-spin symmetry (ds) can resolve these ambiguities in a combined analysis of DsK and D(*)pi (Fleisher) Can make an unambiguous extraction, depending on The value of strong phases: < 10 o (in 2 fb -1 ) U-spin breaking 23 LHCb

24 1. b from trees: BDK GLW method: f D is a CP eigenstate common to D 0 and D 0 : f D = K + K -, + -,… Measure: BD 0 K, B D 0 K, B D 1 K Large event rate; small interference Measurement r B difficult B–B– D0K–D0K– D0K–D0K– fDK–fDK– b c favoured b u suppressed Decay time independent analysis Cabibbo supp. Cabibbo allowed. Interfere decays b c with b u to final states common to D 0 and D 0 color suppression ADS method: Use common flavour state f D =(K + – Note: decay D 0K + – is double Cabibbo suppressed Lower event rate; large interference 24

25 BD ( * ) K ( * ) GLW: D KK (2 rates) ; ADS: D K ( 4 rates) ; ChannelYield (2 fb -1 )B/S B D(hh) K 7.8 k1.8 B D(K ) K, Favoured 56 k0.6 B D(K ) K, Suppressed 0.71k2 B D(K3 ) K, Favoured 62k0.7 B D(K3 ) K, Suppressed 0.8k2 ( ) = 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) Normalization is arbitrary: 7 observables for 5 unknows:, r B, B, D, D 3 Overall: expect precision of ( ) = 5 o with 2 fb -1 of data ADS: D (4 rates) ; Dalitz analyses ( ) See talk of Angelo Carbone 25

26 2. from loops: B (s) hh Interfere b u tree diagram with penguins: Strong parameters d (d), ( ) are strength and phase of penguins to tree. Weak U-spin assumption : d=d+-20%,, independent Assume mixing phases known ChannelYield (2 fb -1 ) B/S B 36k0.5 B s KK36k0.15 Bs K+K- BG ( See talk of Angelo Carbone 2 fb -1 ms=20 Time 26

27 (sin2 ) ~ The B d and B s Mixing Phase Time dependent CP violation in interference between mixing and decay Yesterdays sensation is todays calibration and tomorrows background – Val Telegdi B B f CP Golden mode BsBs BsBs f CP ChannelYield (2 fb -1 ) B/S Bd J/ Ks 216 k0.8 27

28 B s mixing phase DecayYield (2 fb -1 ) s ) J 8.5 k0.109 J/ 3 k0.142 J/ 2.2 k0.154 J/ 4.2 k0.08 c 3 k0.108 D s + D s - 4k0.133 All CP eig J/ 130 k0.023 All Pure CP eigenstates Low yield, high background 2. Admixture of CP eigenstates: B s J/ Golden mode: Large yield, nice signature However PS->VV requires angular analysis to disentagle =+1 (CP-even),-1 (CP-odd) 28

29 Full 3D Angular analysis cos cos cos Study possible systematics of LHCb acceptance and reconstruction on distributions. 29

30 B s J/ time mass signal backg sum cos tr cos tr (M)= 14 MeV )= 35 fs Simultaneous likelihood analysis in time, mass, full 3d-angular distribution Include mass sidebands to model the time spectrum and angular distribution of the background Model the resolution s )=0.02 See talk of Olivier Leroy 30

31 4. s from Penguins Compare observed phases in tree decays with those in penguins ChannelYield (2 fb -1 )B/SWeak phase precision B K s < B/S < 1.1 (sin( d eff ) 0.23 B s 3.1 k< 0.8 ( s eff ) = 0.11 Bs requires time dependent CP asymmetry (PS VV angular analysis a la J/ ) 31 See talk of Olivier Leroy

32 Physics Programme LHCb is a heavy flavour precision Experiment searching for new physics in CP-Violation and Rare Decays CP Violation Rare Decays 32

33 Rare Decays – LHCb Program i=1,2: trees i=3-6,8: g penguin i=7: penguin i=9,10: EW penguin Study processes that are suppressed at tree level to look for NP affecting observables: Branching Ratios, decay time asymmetries, angular asymmetries, polarizations, … Weak B-decays described by effective Hamiltonian: New physics shows up via new operators O i or modification of Wilson coefficients C i compared to SM. LHCb Program: Look for deviations of the SM picture in the decays: 1.b sl+l- ; A fb (B K* ), B +K + ll (R K ), B s 2.b s ; A cp (t) B s BK*, b γ, b * γ,B 0, B γ 3.B q l+l- ; BR (B s ) 4.LFV B q l l (not reported here) 33

34 1. B 0 K *0 µ + µ - Contributions from electroweak penguins Angular distribution is sensitive to NP m 2 [GeV 2 ] A FB (m 2 μμ ) theory illustration Observable: Forward-Backward Asymmetry in l Zero crossing point (s o ) well predicted: 3 angles: l,, K A FB 34 hep-ph: v2

35 B 0 K *0 µ + µ - ChannelYield (2 fb -1 )BG (2 fb -1 ) BsK* + – (BR) Event Selection: Systematic study: Selection should not distort m 2 s 0 point to first order not affected A FB (s), fast MC, 2 fb –1 s = (m ) 2 [GeV 2 ] 2 fb -1 A fb (s) Remove resonances s0s0 See talk Mitesh Patel (s 0 ) = 0.5 GeV 2 35

36 2. B s Probes the exclusive b s radiative penguin Measure time dependent CP asymmetry: ChannelYield (2 fb -1 ) B/S Bs 11k<0.55 Statistical precision after 2 fb -1 (1 year) (A dir ) = 0.11, (A mix ) = 0.11 (requires tagging) (A ) = 0.22 (no tagging required) In SM bs is predominatly (O(m s /m b )) left handed Observed CP violation depends on the polarization See talk Mitesh Patel Event selection: b (L) + (m s /m b ) (R) A dir 0, A mix sin2 sin2, A cos 2 cos tan = |bs R | / | bs L |, cos 1 SM: Measures fraction wrong polarization 36

37 3. B s B s is helicity suppressed SM Branching Ratio: (3.35 ± 0.32) x Sensitive to NP with S or P coupling ChannelSM Yield (2 fb -1 ) Background Bs Event Selection: Main Backgrounds: Suppressed by: b, b Mass & Vertex resol. B hh Particle Identification With 2 fb -1 (1 year): Observe BR: 6 x with 5 Assuming SM BR: 3 observation 37 See talk Mitesh Patel hep-ph/ v5

38 Physics Programme LHCb is a heavy flavour precision Experiment searching for new physics in CP-Violation and Rare Decays CP Violation Rare Decays + Other Physics 38

39 Other Physics See the following talks for an overview: Raluca Muresan: Charm Physics: Mixing and CP Violation Michael Schmelling: Non CP Violation Physics: – B production, multiparticle production, deep inelastic scattering, … 39

40 Conclusions LHCb is a heavy flavour precision experiment searching for New Physics in CP Violation and Rare Decays A program to do this has been developed and the methods, including calibrations and systematic studies, are being worked out.. CP Violation: 2 fb -1 (1 year)* from trees: 5 o - 10 o from penguins: 10 o B s mixing phase: s eff from penguins: 0.11 Rare Decays: 2 fb -1 (1 year)* Bs K* s 0 : 0.5 GeV 2 B s A dir, A mix : 0.11 A : 0.22 B s BR.: 6 x at 5 We appreciate the collaboration with the theory community to continue developing new strategies. We are excitingly looking forward to the data from the LHC. * Expect uncertainty to scale statistically to 10 fb -1. Beyond: see Jim Libbys talk on Upgrade 40

41 Backup

42 LHCb Detector MUON RICH-2 PID RICH-1 PID Tracking (momentum) vertexing HCAL ECAL

43 Display of LHCb simulated event

44 Flavour Tagging Performance of flavour tagging: Efficiency Wrong tag wTagging power BdBd ~50% BsBs 33%~6% Tagging power:

45 Full table of selections Nominal year = bb pairs produced (10 7 s at L= cm 2 s 1 with bb =500 b) Yields include factor 2 from CP-conjugated decays Branching ratios from PDG or SM predictions

46 Bs DsK 5 years data Bs Ds-K+Bs Ds+K- Bsb Ds-K+ Bsb Ds+K-

47 Angle in Summary


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