Presentation on theme: "LHCb Physics Programme"— Presentation transcript:
1LHCb Physics Programme CERN Theory Institute: Flavour as a window to New Physics at the LHC: May 5 –June 13, 2008LHCb Physics ProgrammeMarcel MerkFor the LHCb CollaborationMay 26, 2008Contents:The LHCb ExperimentPhysics Programme:CP ViolationRare Decays
2LHCbb√s = 14 TeVLHCb: L=2-5 x 1032 cm-2 s-1sbb = 500 mbinel / s bb = 160=> 1 “year” = 2 fb-1bbCERNLHCbATLASLumi is a factor 50 to 20 below peak design lumi of General Purpose Detectors (GPD) – defocussing beamsCMSALICEA Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays
3Installation of major structures is complete The LHCb DetectorVELOMuon detCalo’sRICH-2MagnetOT+ITRICH-1Muon detCalo’sRICH-2OTMagnetRICH-1VELOInstallation of major structures is complete
4A 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.
5 B-Vertex Measurement d Example: Bs → Ds K s(t) ~40 fs 144 mm 47 mm d47 mm144 mm440 mmPrimary vertexDecay time resolution = 40 fss(t) ~40 fsExample: Bs → Ds KThe 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 resolutionVertexing:Impact parameter triggerDecay distance (time) measurement
6Momentum and Mass measurement Momentum meas.: Mass resolution for background suppressionNext 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.
7Momentum and Mass measurement Momentum meas.: Mass resolution for background suppressionbtBsKKp+, KDsPrimary vertexBs→ Ds KBs →Ds pMass resolutions ~14 MeVNext 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.
8Particle Identification RICH: K/p identification using Cherenkov light emission angleThe 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=1.034 m3 C4F10 n=1.0014RICH2: m3 CF4 n=1.0005
9Particle Identification RICH: K/p identification; eg. distinguish Dsp and DsK events.Cerenkov light emission anglebtBsKK,KDsPrimary vertexBs → Ds KKK : ± 0.06%pK : 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=1.034 m3 C4F10 n=1.0014RICH2: m3 CF4 n=1.0005
10 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.btBsKKDsPrimary vertexCalorimeter system :Identify electrons, hadrons, neutralsLevel 0 trigger: high ET electron and hadron
11 LHCb muon detection btag m Muon system: Bs And finally the muon system identifies muons. Anything else is stopped.btagBsKKDsPrimary vertexMuon system:Level 0 trigger: High Pt muonsFlavour tagging: eD2 = e (1-2w)2 6%
12LHCb trigger bt L0, HLT and L0×HLT efficiency Detector 40 MHz HLT: high IP, high pT tracks [software] then full reconstruction of event40 MHz1 MHz2 kHzL0: high pT (m, e, g, h) [hardware, 4 ms]Storage (event size ~ 50 kB)DetectorHLT rateEvent typePhysics200 HzExclusive B candidatesB (core program)600 HzHigh mass di-muonsJ/, bJ/X (unbiased)300 HzD* candidatesCharm (mixing & CPV)900 HzInclusive b (e.g. bm)B (data mining)Efficiency Note: decay time dependent efficiency: eg. Bs → Ds KL0 confirmation: HLT associate L0 objects with large impactr parameter tracks 2) inclusive and exclusive selctionsEfficiency in many decay modes will depend on decay time control channelsbtBsKKDsPrimary vertexProper time [ps] 12
13Measuring time dependent decays btBsKKDsPrimary vertexMeasurement of Bs oscillations:Experimental Situation:Ideal measurement (no dilutions)Bs->Ds– p+ (2 fb-1)
14Measuring time dependent decays btBsKKDsPrimary vertexMeasurement of Bs oscillations:Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilutionBs->Ds– p+ (2 fb-1)
15Measuring time dependent decays btBsKKDsPrimary vertexMeasurement of Bs oscillations:Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution+ Realistic decay time resolutionBs->Ds– p+ (2 fb-1)
16Measuring time dependent decays btBsKKDsPrimary vertexMeasurement of Bs oscillations:Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging+ Realistic decay time resolution+ Background eventsBs->Ds– p+ (2 fb-1)
17Measuring time dependent decays btBsKKDsPrimary vertexMeasurement of Bs oscillations:Experimental Situation:Ideal measurement (no dilutions)+ Realistic flavour tagging dilution+ Realistic decay time resolution+ Background events+ Trigger and selection acceptanceBs->Ds– p+ (2 fb-1)Two equally important aims for the experiment:Limit the dilutions: good resolution, tagging etc.Precise knowledge of dilutions
18Expected Performance: GEANT MC simulation Simulation software:Pythia+EvtGenGEANT simulationDetector responseWe have made full MC simulation studies to optimise the experiment and to test the reconstruction quality. More later.Reconstruction software:Event ReconstructionDecay SelectionTrigger/TaggingPhysics FittingUsed to optimise the experiment and to test physics sensitivities
19Physics Programme LHCb is a heavy flavour precision experiment searching for new physicsin CP-Violation and Rare DecaysCP ViolationRare Decays
20CP Violation – LHCb Program Bd triangleBs trianglebq1d, sq2W−gd (s)qW −bu,c,tCP Program: Is CKM fully consistent for trees, boxes and penguins?g measurements from treesg measurement from penguinsbs from the box: “Bs mixing phase”bs in penguinsbqu, c, tW+W−V*ibViq
211.a g +fs from trees: Bs→DsK Time dependent CP violation in interference of bc and bu decays:BsBs/Bs →Ds–K+ (10 fb-1)BsTime
22Bs→DsK s(g+fs) = 9o–12o Since same topology BsDsK, Bs Dsp combine samples to fit Dms, DGsand Wtag together with CP phase g+fs.10 fb-1 data:Bs→ Ds-p+Bs→ Ds-K+(Dms = 20)Use lifetime differenceDGs to resolve someambiguities (2 remain).s(g+fs) = 9o–12oDepending on the value of the strong phase and background levelYield & B/S : LHCb 2007 – 017 Gamma: LHCbChannelYield (2 fb-1)B/S(90% C.L.)BsDsK6.2 k[ ]BsDsp140 k[ ]Decay Time →
23B →Dp and Bs→DsK B D(*)p measures g in similar way as BsDsK More statistics, but smaller asymmetryNo lifetime difference:8 –fold ambiguity for g solutionsLHCbChannelYield (2 fb-1)B/SBsD*(K p) p206 k<0.3B->D p210 k0.3Invoking 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|~0.02Method 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 unambiguousextraction, depending onThe value of strong phases:s(g) < 10o (in 2 fb-1)U-spin breaking
241.b g from trees: B→DK D0K– fDK– B– D0K– GLW method: ADS method: Interfere decays bc with buto final states common to D0 and D0colorsuppressionGLW method:fD is a CP eigenstate common toD0 and D0: fD= K+K-, p+p-,…Measure: B→D0K, B → D0K, B→ D1KLarge event rate; small interferenceMeasurement rB difficultbc favouredCabibbo supp.D0K–fDK–B–Self tagging modes from kaon charge: B-K-, B+K+, B0K*(K+pi-)Gronau London Wyler – triangle relations difficulty: rB? Semileptonic decay with huge background.Atwood Dunietz SoniD0K–bu suppressedCabibbo allowed.ADS method:Use common flavour state fD=(K+ p –) Note: decay D0→K+p– is double Cabibbo suppressedLower event rate; large interferenceDecay time independent analysis
25B→D(*)K(*) g, rB, dB, dDp , dD3p s(g) = 5o with 2 fb-1 of data See talk of Angelo CarboneGLW: D KK (2 rates) ;ADS: D Kp ( 4 rates) ;ADS: D K3p (4 rates) ;ChannelYield (2 fb-1)B/SB → D(hh) K7.8 k1.8B → D(Kp) K , Favoured56 k0.6B → D(Kp) K , Suppressed0.71k2B → D(K3p) K, Favoured62k0.7B → D(K3p) K, Suppressed0.8kNormalization isarbitrary:7 observables for 5 unknows:g, rB, dB, dDp , dD3ps(g) = 5o to 13odepending on strong phases.GLW: Gronau, London, Wheeler ADS: Atwood, Dunietz, SoniMM: D* difficult to reconstruct – BG!- Miteshs(g)Also under study:B± → DK± with D → Ks pp oB± → DK± with D → KK pp oB0 → DK*0 with D → KK, Kp, pp 6o -12oB± → D*K± with D → KK, Kp, pp (high background)Dalitz analysesOverall: expect precision ofs(g) = 5o with 2 fb-1 of data
262. g from loops: B(s)→hh s ( g ) ~10o See talk of Angelo CarboneInterfere b u tree diagram with penguins:Strong parameters d (d’), q (q’) arestrength and phase of penguins to tree.Weak U-spin assumption :d=d’+-20% , q, q’ independentAssume mixing phases known2 fb-1Dms=20BsK+K-BGs ( g ) ~10oChannelYield(2 fb-1)B/SBpp36k0.5BsKK0.15Time
273. The Bd and Bs Mixing Phase Time dependent CP violation in interference between mixing and decayBsfCPBfCPs(sin2b ) ~ 0.02ChannelYield(2 fb-1)B/SBdJ/yKs216 k0.8“Golden mode”“Yesterday’s sensation is today’scalibration and tomorrow’s background”– Val Telegdi
28Bs mixing phase 1. Pure CP eigenstates Low yield, high background 2. Admixture of CP eigenstates: Bs→J/y f“Golden mode”: Large yield, nice signatureHowever PS->VV requires angular analysisto disentagle h=+1 (CP-even) ,-1 (CP-odd)DecayYield(2 fb-1)s (fs)J/y hgg8.5 k0.109J/yhppp3 k0.142J/y h’pph2.2 k0.154J/y h’rg4.2 k0.08hc f0.108Ds+ Ds-4k0.133All CP eig-0.046J/y f130 k0.023All0.021Measure the decay rates….
29Full 3D Angular analysis cos y = cosqfcosqfStudy possible systematics of LHCb acceptance and reconstruction on distributions.
30Bs→ J/y fsignalbackgsumSimultaneous likelihood analysis in time, mass, full 3d-angular distributionInclude mass sidebands to model the time spectrum and angular distribution of the backgroundModel the t resolution s (fs)=0.02s(t)= 35 fstimes(M)= 14 MeVSee talk of Olivier Leroymasscosqfcos qtrftr
314. b & bs from PenguinsCompare observed phases in tree decays with those in penguinsGluonic penguins. Roger forty sigma(sym = 0.04) check. B Phi ks : LHCb 2007 – 013, Bs phi phi : LHCbBs f f requires time dependent CP asymmetry(PSVV angular analysis a la J/yf )See talk of Olivier LeroyChannelYield (2 fb-1)B/SWeak phase precisionB f Ks9200.3 < B/S < 1.1s (sin(fdeff) 0.23Bs f f3.1 k< 0.8s (fseff ) = 0.11
32Physics Programme LHCb is a heavy flavour precision Experiment searching for new physicsin CP-Violation and Rare DecaysCP ViolationRare Decays
33Rare Decays – LHCb Program Weak B-decays described by effective Hamiltonian:i=1,2: treesi=3-6,8: g penguini=7: g penguini=9,10: EW penguinNew physics shows up via new operators Oi or modification of Wilson coefficients Ci compared to SM.Study processes that are suppressed at treelevel 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 currentsB s gamma: O_7 gamma and O_7gluon magnetic penguinsBs mumu O_S,_PVanya:1. Brho gamma and B W gamma measures |Vtd/Vts|2. Lambda b Lambda(*) gamma, photon polarization3. Bs phi gamma allows photon polarization due to Delta GammaRk 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(BK*mm) , B+→K+ll (RK), Bs→ fmmb s g ; Acp(t) Bs fg , B→K*g, Lb→Lγ, Lb→ L*γ,B →r0g, B→wγBq l+l- ; BR (Bs mm)LFV Bq l l‘ (not reported here)
341. B0→K*0µ+µ- 3 angles: ql, f ,qK AFB Contributions from electroweak penguinsAngular distribution is sensitive to NP3 angles:ql, f ,qKm2 [GeV2]AFB(m2μμ) theory illustrationAFBObservable: Forward-Backward Asymmetry in qlB.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: v2
35B0→K*0µ+µ- s0 Event Selection: Afb(s) Systematic study: See talk Mitesh PatelEvent Selection:ChannelYield (2 fb-1)BG (2 fb-1)Bs→K*m+ m–(BR)AFB(s), fast MC, 2 fb–1s = (m)2 [GeV2] 2 fb-1Afb(s) s0s(s0) = 0.5 GeV2RemoveresonancesBG: Double semileptonic events. AT2 = theoretically cleanSystematic study:Selection should not distort m2mms0 point to first order not affected
362. Bs→fg Probes the exclusive b →s radiative penguin See talk Mitesh PatelProbes the exclusive b →s radiative penguinMeasure time dependent CP asymmetry:b (L) + (ms/mb) (R)In SM b→s g is predominatly (O(ms/mb)) left handedObserved CP violation depends on the g polarizationEvent selection:ChannelYield(2 fb-1)B/SBs→fg11k<0.55SM:Adir 0, Amix sin2y sin2f , AD cos 2y cosftan y = |b→s g R| / | b→s g L| , cos f 1Direct CP asymmetry suppressed in SM. Mixing induced asymmetry. Tan psi is the fraction of “wrong”gammaPolarization. A_delta measures this quantity directly.Statistical precision after 2 fb-1 (1 year)s(Adir ) = , s (Amix ) = (requires tagging)s (AD) = (no tagging required)Measures fraction “wrong” g polarization
373. Bs →m+m- Bs mm is helicity suppressed See talk Mitesh PatelBs mm is helicity suppressedSM Branching Ratio: (3.35 ± 0.32) x 10 -9Sensitive to NP with S or P couplinghep-ph/ v5Event Selection:Main Backgrounds: Suppressed by:bm, bm Mass & Vertex resol.B hh Particle IdentificationChannelSM Yield(2 fb-1)BackgroundBs mm3083Scalar or PseudoscalarWith 2 fb-1 (1 “year”):Observe BR: 6 x 10-9 with 5 sAssuming SM BR: 3s observation
38Physics Programme LHCb is a heavy flavour precision Experiment searching for new physicsin CP-Violation and Rare DecaysCP ViolationRare Decays+ “Other” Physics
39“Other” Physics See the following talks for an overview: Raluca Muresan:Charm Physics: Mixing and CP ViolationMichael Schmelling:Non CP Violation Physics:B production, multiparticle production, deep inelastic scattering, …
40ConclusionsLHCb is a heavy flavour precision experiment searching for New Physics in CP Violation and Rare DecaysA 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 - 10og from penguins: 10oBs mixing phase: 0.023bseff from penguins: 0.11Rare Decays: 2 fb-1 (1 year)*BsK*mm s0 : 0.5 GeV2Bs g Adir , Amix : 0.11AD : 0.22Bsmm BR.: 6 x 10-9 at 5sWe 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