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

LHCb @ LHC b b √s = 14 TeV LHCb: L=2-5 x 1032 cm-2 s-1 sbb = 500 mb inel / s bb = 160 => 1 “year” = 2 fb-1 b b CERN LHCb ATLAS Lumi is a factor 50 to 20 below peak design lumi of General Purpose Detectors (GPD) – defocussing beams CMS ALICE A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays

Installation of major structures is complete The LHCb Detector VELO Muon det Calo’s RICH-2 Magnet OT+IT RICH-1 Muon det Calo’s RICH-2 OT Magnet RICH-1 VELO Installation of major structures is complete 31-3-2008

A walk through the LHCb spectrometer… Indicate collission point. Acceptance between 15 mrad and 200 mrad. First half serves roughly to reconstruct the trajectories of charged particles in a big dipole magnetic field. The second half are detectors to recognize the particle identity: photon, electron, muon, pion, kaon. 

 B-Vertex Measurement d Example: Bs → Ds K s(t) ~40 fs 144 mm 47 mm  d 47 mm 144 mm 440 mm Primary vertex Decay time resolution = 40 fs s(t) ~40 fs Example: Bs → Ds K The detector built around the interaction point is the Verex locator. It is an array of silicon detetectors that can be moved in to a distance of 8 mm of the beam line. Vertex Locator (Velo) Silicon strip detector with ~ 5 mm hit resolution  30 mm IP resolution Vertexing: Impact parameter trigger Decay distance (time) measurement 31-3-2008

Momentum and Mass measurement Momentum meas.: Mass resolution for background suppression Next there is the magnetic field region. A large dipole magnet is surrounded by tracking stations in fron and behind. The Bfield integral is 4 Tm, which allows for precise momentum measurements up to high momenta. 

Momentum and Mass measurement Momentum meas.: Mass resolution for background suppression bt Bs K K p+, K  Ds Primary vertex Bs→ Ds K Bs →Ds p Mass resolution s ~14 MeV Next there is the magnetic field region. A large dipole magnet is surrounded by tracking stations in fron and behind. The Bfield integral is 4 Tm, which allows for precise momentum measurements up to high momenta. 

Particle Identification RICH: K/p identification using Cherenkov light emission angle The RICH detectors serve mainly to identify pions and kaons. They are not present in Atlas or CMS. The detection mechanism is based on the fact that particles traverse the detectors with velocities higher that the velocity in the detector medium (gas). RICH 1 optimized for low momentum tracks, RICH 2 for high momentum tracks. As charged particle tracks traverse the medium they radiate photons in a cone around their track direction. These photons make ring images around the track as measured in the tracking detectors. The emission angle of the cone depends on the velocity of the particle. If we know the velocity from the RICH and the momentum from the trackers, the particle mass and therefore the identity is known. Again a number of postdocs and grad students is required to make the pattern recognition work. Image of RICH2.  RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014 RICH2: 100 m3 CF4 n=1.0005

Particle Identification RICH: K/p identification; eg. distinguish Dsp and DsK events. Cerenkov light emission angle bt Bs K K ,K  Ds Primary vertex Bs → Ds K KK : 97.29 ± 0.06% pK : 5.15 ± 0.02% The RICH detectors serve mainly to identify pions and kaons. They are not present in Atlas or CMS. The detection mechanism is based on the fact that particles traverse the detectors with velocities higher that the velocity in the detector medium (gas). RICH 1 optimized for low momentum tracks, RICH 2 for high momentum tracks. As charged particle tracks traverse the medium they radiate photons in a cone around their track direction. These photons make ring images around the track as measured in the tracking detectors. The emission angle of the cone depends on the velocity of the particle. If we know the velocity from the RICH and the momentum from the trackers, the particle mass and therefore the identity is known. Again a number of postdocs and grad students is required to make the pattern recognition work. Image of RICH2.  RICH1: 5 cm aerogel n=1.03 4 m3 C4F10 n=1.0014 RICH2: 100 m3 CF4 n=1.0005

 LHCb calorimeters bt e h Calorimeter system : Bs K K  Ds Subsequently the calorimeters identify photons, elctrons, hadrons by stopping the showers. They supply the Et trigger.  bt Bs K K  Ds Primary vertex Calorimeter system : Identify electrons, hadrons, neutrals Level 0 trigger: high ET electron and hadron

 LHCb muon detection btag m Muon system: Bs And finally the muon system identifies muons. Anything else is stopped.  btag Bs K K  Ds Primary vertex Muon system: Level 0 trigger: High Pt muons Flavour tagging: eD2 = e (1-2w)2  6%

LHCb trigger bt L0, HLT and L0×HLT efficiency Detector 40 MHz HLT: high IP, high pT tracks [software] then full reconstruction of event 40 MHz 1 MHz 2 kHz L0: high pT (m, e, g, h) [hardware, 4 ms] Storage (event size ~ 50 kB) Detector HLT rate Event type Physics 200 Hz Exclusive B candidates B (core program) 600 Hz High mass di-muons J/, bJ/X (unbiased) 300 Hz D* candidates Charm (mixing & CPV) 900 Hz Inclusive b (e.g. bm) B (data mining) Efficiency  Note: decay time dependent efficiency: eg. Bs → Ds K L0 confirmation: HLT associate L0 objects with large impactr parameter tracks 2) inclusive and exclusive selctions Efficiency in many decay modes will depend on decay time  control channels bt Bs K K  Ds Primary vertex Proper time [ps]  12

Measuring time dependent decays bt Bs K K   Ds Primary vertex Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) Bs->Ds– p+ (2 fb-1)

Measuring time dependent decays bt Bs K K   Ds Primary vertex Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution Bs->Ds– p+ (2 fb-1)

Measuring time dependent decays bt Bs K K   Ds Primary vertex Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging dilution + Realistic decay time resolution Bs->Ds– p+ (2 fb-1)

Measuring time dependent decays bt Bs K K   Ds Primary vertex Measurement of Bs oscillations: Experimental Situation: Ideal measurement (no dilutions) + Realistic flavour tagging + Realistic decay time resolution + Background events Bs->Ds– p+ (2 fb-1)

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

Expected Performance: GEANT MC simulation Simulation software: Pythia+EvtGen GEANT simulation Detector response We have made full MC simulation studies to optimise the experiment and to test the reconstruction quality. More later. Reconstruction software: Event Reconstruction Decay Selection Trigger/Tagging Physics Fitting Used to optimise the experiment and to test physics sensitivities

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

CP Violation – LHCb Program Bd triangle Bs triangle b q1 d, s q2 W− g d (s) q W − b u,c,t CP Program: Is CKM fully consistent for trees, boxes and penguins? g measurements from trees g measurement from penguins bs from the box: “Bs mixing phase” bs in penguins b q u, c, t W+ W− V*ib Viq

1.a g +fs from trees: Bs→DsK Time dependent CP violation in interference of bc and bu decays: Bs Bs/Bs →Ds–K+ (10 fb-1) Bs Time

Bs→DsK s(g+fs) = 9o–12o Since same topology BsDsK, Bs Dsp combine samples to fit Dms, DGs and Wtag together with CP phase g+fs. 10 fb-1 data: Bs→ Ds-p+ Bs→ Ds-K+ (Dms = 20) Use lifetime difference DGs to resolve some ambiguities (2 remain). s(g+fs) = 9o–12o Depending on the value of the strong phase and background level Yield & B/S : LHCb 2007 – 017 Gamma: LHCb 2007 - 041 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] Decay Time →

B →Dp and Bs→DsK B  D(*)p measures g in similar way as BsDsK More statistics, but smaller asymmetry No lifetime difference: 8 –fold ambiguity for g solutions LHCb-2005-036 Channel Yield (2 fb-1) B/S BsD*(K p) p 206 k <0.3 B->D p 210 k 0.3 Invoking U-spin symmetry (d↔s) can resolve these ambiguities in a combined analysis of DsK and D(*)pi (Fleisher) |lambda_s| ~0.4 |lambda_d|~0.02 Method works because we measure sin(phi_d + gamma) and sin (phi_s + gamma) with same strong phase: LHCb 2005 – 036. Also for event yields. Can make an unambiguous extraction, depending on The value of strong phases: s(g) < 10o (in 2 fb-1) U-spin breaking

1.b g from trees: B→DK D0K– fDK– B– D0K– GLW method: ADS method: Interfere decays bc with bu to final states common to D0 and D0 color suppression GLW method: fD is a CP eigenstate common to D0 and D0: fD= K+K-, p+p-,… Measure: B→D0K, B → D0K, B→ D1K Large event rate; small interference Measurement rB difficult bc favoured Cabibbo supp. D0K– fDK– B– Self tagging modes from kaon charge: B-K-, B+K+, B0K*(K+pi-) Gronau London Wyler – triangle relations difficulty: rB? Semileptonic decay with huge background. Atwood Dunietz Soni D0K– bu suppressed Cabibbo allowed. ADS method: Use common flavour state fD=(K+ p –) Note: decay D0→K+p– is double Cabibbo suppressed Lower event rate; large interference Decay time independent analysis

B→D(*)K(*) g, rB, dB, dDp , dD3p s(g) = 5o with 2 fb-1 of data See talk of Angelo Carbone GLW: D KK (2 rates) ; ADS: D Kp ( 4 rates) ; ADS: D K3p (4 rates) ; 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 Normalization is arbitrary: 7 observables for 5 unknows: g, rB, dB, dDp , dD3p s(g) = 5o to 13o depending on strong phases. GLW: Gronau, London, Wheeler ADS: Atwood, Dunietz, Soni MM: D* difficult to reconstruct – BG!- Mitesh s(g) Also under study: B± → DK± with D → Ks pp 80-12o B± → DK± with D → KK pp 18o 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

2. g from loops: B(s)→hh s ( g ) ~10o See talk of Angelo Carbone Interfere b u tree diagram with penguins: Strong parameters d (d’), q (q’) are strength and phase of penguins to tree. Weak U-spin assumption : d=d’+-20% , q, q’ independent Assume mixing phases known 2 fb-1 Dms=20 BsK+K- BG s ( g ) ~10o Channel Yield (2 fb-1) B/S Bpp 36k 0.5 BsKK 0.15 Time

3. The Bd and Bs Mixing Phase Time dependent CP violation in interference between mixing and decay Bs fCP B fCP s(sin2b ) ~ 0.02 Channel Yield (2 fb-1) B/S BdJ/yKs 216 k 0.8 “Golden mode” “Yesterday’s sensation is today’s calibration and tomorrow’s background” – Val Telegdi

Bs mixing phase 1. Pure CP eigenstates Low yield, high background 2. Admixture of CP eigenstates: Bs→J/y f “Golden mode”: Large yield, nice signature However PS->VV requires angular analysis to disentagle h=+1 (CP-even) ,-1 (CP-odd) Decay Yield (2 fb-1) s (fs) J/y hgg 8.5 k 0.109 J/yhppp 3 k 0.142 J/y h’pph 2.2 k 0.154 J/y h’rg 4.2 k 0.08 hc f 0.108 Ds+ Ds- 4k 0.133 All CP eig - 0.046 J/y f 130 k 0.023 All 0.021 Measure the decay rates….

Full 3D Angular analysis cos y = cosqf cosq f Study possible systematics of LHCb acceptance and reconstruction on distributions.

Bs→ J/y f signal backg sum 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 t resolution  s (fs)=0.02 s(t)= 35 fs time s(M)= 14 MeV See talk of Olivier Leroy mass cosqf cos qtr ftr

4. b & bs from Penguins Compare observed phases in tree decays with those in penguins Gluonic penguins. Roger forty sigma(sym = 0.04)  check. B Phi ks : LHCb 2007 – 013, Bs phi phi : LHCb 2007 - 047 Bs  f f requires time dependent CP asymmetry (PSVV angular analysis a la J/yf ) See talk of Olivier Leroy Channel Yield (2 fb-1) B/S Weak phase precision B f Ks 920 0.3 < B/S < 1.1 s (sin(fdeff)  0.23 Bs  f f 3.1 k < 0.8 s (fseff ) = 0.11

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

Rare Decays – LHCb Program Weak B-decays described by effective Hamiltonian: i=1,2: trees i=3-6,8: g penguin i=7: g penguin i=9,10: EW penguin New physics shows up via new operators Oi or modification of Wilson coefficients Ci compared to SM. Study processes that are suppressed at tree level to look for NP affecting observables: Branching Ratio’s, decay time asymmetries, angular asymmetries, polarizations, … Ci Wilson coefficients at weak scale. Oi non-perturbative (matrix element) operators. At B-mass energy scale: Ci effective. K*mumu : O_9L and O_10L sensitive to right handed currents B s gamma: O_7 gamma and O_7gluon magnetic penguins Bs mumu O_S,_P Vanya: 1. Brho gamma and B W gamma measures |Vtd/Vts| 2. Lambda b Lambda(*) gamma, photon polarization 3. Bs phi gamma allows photon polarization due to Delta Gamma Rk is ratio B+mumu / B+K+ee (sensitive to Higgs couplings) LHCb Program: Look for deviations of the SM picture in the decays: b sl+l- ; Afb(BK*mm) , B+→K+ll (RK), Bs→ fmm b  s g ; Acp(t) Bs fg , B→K*g, Lb→Lγ, Lb→ L*γ,B →r0g, B→wγ Bq l+l- ; BR (Bs mm) LFV Bq l l‘ (not reported here)

1. B0→K*0µ+µ- 3 angles: ql, f ,qK AFB Contributions from electroweak penguins Angular distribution is sensitive to NP 3 angles: ql, f ,qK m2 [GeV2] AFB(m2μμ) theory illustration AFB Observable: Forward-Backward Asymmetry in ql B.R is in agreement with Standard model. Contributions: O_9L and O_10L. AFB in particular sensitive to models with right handed currents (not V-A) Zero crossing point (so) well predicted: hep-ph:0106067v2

B0→K*0µ+µ- s0 Event Selection: Afb(s)  Systematic study: See talk Mitesh Patel Event Selection: Channel Yield (2 fb-1) BG (2 fb-1) Bs→K*m+ m– 7200+-2200 (BR) 1770+-310 AFB(s), fast MC, 2 fb–1 s = (m)2 [GeV2]  2 fb-1 Afb(s)  s0 s(s0) = 0.5 GeV2 Remove resonances BG: Double semileptonic events. AT2 = theoretically clean Systematic study: Selection should not distort m2mm s0 point to first order not affected

2. Bs→fg Probes the exclusive b →s radiative penguin See talk Mitesh Patel Probes the exclusive b →s radiative penguin Measure time dependent CP asymmetry: b   (L) + (ms/mb)  (R) In SM b→s g is predominatly (O(ms/mb)) left handed Observed CP violation depends on the g polarization Event selection: Channel Yield (2 fb-1) B/S Bs→fg 11k <0.55 SM: Adir  0, Amix  sin2y sin2f , AD  cos 2y cosf tan y = |b→s g R| / | b→s g L| , cos f  1 Direct CP asymmetry suppressed in SM. Mixing induced asymmetry. Tan psi is the fraction of “wrong”gamma Polarization. A_delta measures this quantity directly. Statistical precision after 2 fb-1 (1 year) s(Adir ) = 0.11 , s (Amix ) = 0.11 (requires tagging) s (AD) = 0.22 (no tagging required) Measures fraction “wrong” g polarization

3. Bs →m+m- Bs mm is helicity suppressed See talk Mitesh Patel Bs mm is helicity suppressed SM Branching Ratio: (3.35 ± 0.32) x 10 -9 Sensitive to NP with S or P coupling hep-ph/0604057v5 Event Selection: Main Backgrounds: Suppressed by: bm, bm Mass & Vertex resol. B hh Particle Identification Channel SM Yield (2 fb-1) Background Bs mm 30 83 Scalar or Pseudoscalar With 2 fb-1 (1 “year”): Observe BR: 6 x 10-9 with 5 s Assuming SM BR: 3s observation

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

“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, …

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)* g from trees: 5o - 10o g from penguins: 10o Bs mixing phase: 0.023 bseff from penguins: 0.11 Rare Decays: 2 fb-1 (1 year)* BsK*mm s0 : 0.5 GeV2 Bs g Adir , Amix : 0.11 AD : 0.22 Bsmm BR.: 6 x 10-9 at 5s 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 Libby’s talk on Upgrade

Backup

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

Display of LHCb simulated event Hope to see reconstructed events like this soon. 31-3-2008

Flavour Tagging Performance of flavour tagging: Efficiency e Wrong tag w Tagging power Bd ~50% Bs 33% ~6% Tagging power:

Full table of selections Nominal year = 1012 bb pairs produced (107 s at L=21032 cm2s1 with bb=500 b) Yields include factor 2 from CP-conjugated decays Branching ratios from PDG or SM predictions

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

Angle g in Summary