Prospects for New Physics in CP Violation and Rare Decays at LHCb 10 November 2008 Prospects for New Physics in CP Violation and Rare Decays at LHCb Pascal Perret LPC Clermont On behalf of the LHCb Collaboration

Pascal Perret - LPC Clermont b Production in LHCb bb pair production correlated and sharply peaked forward-backward Single-arm forward spectrometer : θ~15-300 mrad (rapidity range: 4.9>η>1.9) Cross section of bb production in LHCb acceptance: σbb ~ 230 µb B+ (40%), B0 (40%), Bs (10%), b-baryons (10%), Bc (< 0.1%) LHCb limits luminosity to few 1032 cm-2s-1 instead of 1034 cm-2s-1 by not focusing the beam as much as ATLAS and CMS maximizes probability of a single interaction per crossing design luminosity soon after start-up pp interactions/crossing LHCb n=0 n=1 collect 2fb-1 per nominal year ~ 1012 bb pairs produced per year 1 LHCb day = 100 B-factory day 10/11/2008 Pascal Perret - LPC Clermont

LHCb overview and performance 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont LHCb: vertex locator VELO Vertex Locator (Velo) Silicon strip detector 8 mm from beam with ~ 5 mm hit resolution 30 mm IP resolution Decay time resolution ~ 40 fs 10/11/2008 Pascal Perret - LPC Clermont

LHCb: momentum & mass measurement Track reconstruction efficiency: 95% for tracks with p>5 GeV Magnet OT IT TT Drift time tube Momentum measurement (s(p)/p ~ (0.4 + 1.5 p/TeV)%) and Mass resolution s ~14 MeV 10/11/2008 Pascal Perret - LPC Clermont

LHCb: particle identification HPD RICH2: 100 m3 CF4 n=1.0005 16-~100 GeV RICH1: 5 cm aerogel n=1.03 : 2-~10 GeV 4 m3 C4F10 n=1.0014 : 10-~60 GeV RICH: K/p identification (KK: ~96.8%, pK: ~3.9%) ; eg. distinguish Dsp and DsK events. 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont LHCb: calorimeter ECAL HCAL Inner Outer Middle region ECAL (inner modules): σ(E)/E ~ 8.2% /√E + 0.9% PS SPD Calorimeter system : Detection of electrons, π0, γ, hadrons Level 0 trigger: high ET electron and hadron, photon 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont LHCb: muon system Muon system: Level 0 trigger: High Pt muons Muon ID: ~ 95% for 5% hadron misID Muons Multi Wire Proportional Chamber Triple-GEM for M1-R1 M1 under installation … 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont LHCb: beam pipe Magnet TT Beam pipe: Under vacuum June – Oct. Detector closed SPD Pb M2 HCAL ECAL PS Be inox RICH2 10/11/2008 Pascal Perret - LPC Clermont

LHCb trigger system Two levels: High pT : m, e, h, g 4 µs 1st level: hardware 4 ms latency “moderate” pT m, e, g & hadrons, e.g. pT m >1.3 GeV/c : full custom made HLT: software ~2000 CPU 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) (Interaction rate ~ 10 MHz b hadron inside LHCb ~50 kHz) 40 MHz Pile-up Calorimeter Muon + L0DU Level 0: High pT : m, e, h, g 4 µs 1 MHz HLT: L0 confirmation m, e, h, g alleys inclusive/exclusive Selection Full reconstruction of event 2 kHz Storage(event size ~ 35 kB) 10/11/2008 Pascal Perret - LPC Clermont

Events with LHC beam induced particles Status of LHCb LHCb detector fully installed and commissioned, including L0 trigger All sub-detectors have undergone the first readout synchronisation and alignment with cosmics & LHC beam induced particles Events with LHC beam induced particles F. Dettori poster Top view Splashy event from lost particles (not all tracks reconstructed...) Muon Calo OT Calo OT Muon Velo Side view Clean event from halo muons 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont New Physics in CPV Unitarity Triangles Bs Bd0  p+ p- Bd0  r p BS0  DS p Bd0  J/y KS0 Bd a b g VudVub VtdVtb VcdVcb * Bd0  DK*0 BS0  DSK Bd0  D* p,3p BS0  J/y f bs VtsVtb VcsVcb VusVub Box diagram Penguin diagram Overconstrain the unitarity triangles (consistency checks) 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont New Physics in CPV Unitarity Triangles New particles may show up in loop process Bs Bd0  p+ p- Bd0  r p BS0  DS p Bd0  J/y KS0 Bd a b g VudVub VtdVtb VcdVcb * Bd0  DK*0 BS0  DSK Bd0  D* p,3p BS0  J/y f bs VtsVtb VcsVcb VusVub Box diagram New Physics ? Penguin diagram Overconstrain the unitarity triangles (consistency checks) will allow to understand the nature and flavour structure of possible New Physics ones b-physics measurements probe New Physics and are complementary to direct searches 10/11/2008 Pascal Perret - LPC Clermont

 Measurements from Bs  Ds K+ Interference between 2 tree diagrams via Bs mixing: BsDs K (b  c) and BsDsK (b  u) (+ CP conjugates) Measure  + s in a clean way (no theoretical uncertainty) from time dependent rates Use s from Bs  J/y f Include Bs Ds (20x Br) to determine Δms ΔΓs and tagging dilution Simultaneous fit to Bs→Ds and Bs→DsK decay time distributions (tagged and untagged) 10 fb-1 data: Bs→ Ds-p+ Bs→ Ds-K+ (Dms = 20) Mode Sig. yield B/S Bs→DsK 6.2k 0.7 Bs→Ds 140k 0.2 Sensitivity 2 fb-1 10 fb-1  stat()° 10.3 4.6 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont  Measurements Different ways to measure  at LHCb: 2 amplitudes, b→c (dominant) & b→u (color suppressed), interfere in decays to a common D0 and D0 modes state: B mode D mode Method s(g) 2fb-1 Bs→DsK KKp Tagged, A(t) 10º B+→D K+ Kp+ K3p +KK/pp counting, ADS+GLW 5º - 13º Kspp Dalitz, GGSZ 7-12º KKpp 4 body Dalitz 18º B0→D K*0 Kp + KK + pp 9º B→pp,KK - Tagged, A(t) Tree decays only Global fit of all the channels: σ(g) = 4.3-6.2° with 2fb-1 Penguin amplitudes: Interference of b→u tree & b→d(s) penguin diagrams Other modes under study: B+→D*(D → Kp/KK/pp) K+, B+→D(→ Kppp)K+, … Compare angle  measured from interfering tree decays (which should always take the value from the CKM matrix) to angle measured from penguin diagrams: Any difference is a sign of New Physics 10/11/2008 Pascal Perret - LPC Clermont

fs measurements from Bs  J/y f The measure of Bs-Bs mixing phase s in BsJ/(µµ) is sensitive to New Physics effects in mixing: s = s(SM) + s(NP) in SM: s = – 2βs = arg(Vts2) ~ –0.04 Tevatron: s ~2.2 away from SM (central experimental value -0.77) It is not a pure CP eigenstate (VV decay). 2 CP even, 1 CP odd amplitude need to fit angular distributions of decay final states as function of proper time Good proper-time resolution is essential: ~39fs Good tagging of initial Bs flavour : Combined = 6.2% Good mass resolution: 13 MeV Good particle identification e(KK)~80% e (pK)~ 3% +NP? e(1-2w)2 Muon 0.8 Electron 0.4 K (OS) 1.5 K (SS) 2.1 Q vertex 1.1 Invariant mass of BsJ/() 10/11/2008 Pascal Perret - LPC Clermont

fs measurements from Bs  J/y f BRvis[BsJ/(µµ)(K+K-)]= (3.1±1.1)x10-5 With 2 fb-1 (1 nominal year): 114k reconstructed events (before tagging) S/B ~2  stat(s) ~0.03 5σ NP discovery, if s >0.1! Low systematic uncertainties: Proper time acceptance: no bias from selection Angular resolution: very good & negligible Mistag and proper time are crucial… Already at the start-up with 0.5 fb-1: 28.5k reconstructed events  stat(s) ~0.06 LHCb should rapidly pin down whether really sign of new physics … ηf = +, - 1 CP eigenstates 10/11/2008 Pascal Perret - LPC Clermont

New Physics in rare decays 10/11/2008 Pascal Perret - LPC Clermont

New Physics in BdK*0m+m- Flavour Changing Neutral Current Decay in SM: b  s electroweak penguin NP diagrams could contribute at same level Sensitive to magnetic and vector and axial semi-leptonic penguin operators Decay described by three angles (θl, φ, θK) and di-μ invariant mass q2 gluino, chargino, neutralino, ? Higgs, ? s = (m)2 [GeV2] AFB(s), theory Forward-backward asymmetry AFB(s) in the mm rest-frame is sensitive NP probe Uncertainties from Bd→K* transition form-factors cancel zero of AFB(s) depends on Wilson coefficients C7eff/C9eff 10/11/2008 Pascal Perret - LPC Clermont

New Physics in BdK*0m+m- NB: Opposite sign convention w.r.t. LHCb Current Measurements: BR measured at B-factories, in agreement with SM: 1.1 ±0.3x10-6 AFB also: Belle has ~230 K*ll events LHCb sensitivity: Expected yields: 7.2k events/2fb–1 Background: dominated by b→ m, b→ m, symmetric distribution in θl observed b→ m, b→ c → m significant contribution, asymmetric θl distribution … B/S ~0.2 Acceptance correction … Simple linear fit suggests precision: 657 MBB q2(GeV2) An example 0.5fb-1 experiment AFB 0.5 fb-1 2 fb-1 6 fb-1 (s0) 0.8 GeV2 0.5 GeV2 0.3 GeV2 More complex fit methods being evaluated 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont New Physics in Bsm+m- SM SM MSSM ? ? ~ tan6/MH2 Helicity suppressed and in SM: BR(Bs → m+m-) = (3.4 ± 0.5) 10-9 sensitive to New Physics; could be strongly enhanced in SUSY Current limit from CDF: BR(Bs → m+m-) < 4.7 10-8 Event selection Main issue is background rejection: dominated by B → m+X, B → m- X decays good mass resolution and PID essential SM Yield (2 fb-1): Signal: 23 – Bkg: 150 Statistical method applied to separate signal from background using PID, vertexing, mass CDF Sensitivity with 8fb-1? Sensitivity 0.1 fb-1 0.5 fb-1 2 fb-1 6 fb-1 BR SM BR < 10-8 (CDF limit) Excluded <SM 3  evidence 5  observation 10/11/2008 Pascal Perret - LPC Clermont

Pascal Perret - LPC Clermont Summary Few hints of deviation from SM in b-physics are observed … Flavour physics at the LHC will play a central role in the understanding of any new physics signals LHCb offers exciting prospects for precision measurement and search for new physics in CP violation & rare decays: with 10fb-1 g measurements: with trees: a combined sensitivity of sg~2-3o is expected with loops: g with a sensitivity of sg~5o is expected s measurements:  (s) ~0.01 Rare decays: BdK*0m+m- : (s0) =0.3 GeV2 Bsm+m- :5  observation of SM value Ready and waiting for the first collisions! With fraction of a 1 year nominal data set LHCb can already perform important key measurements probing New Physics Many topics not addressed in this talk: ,  measurements, charm physics, radiative decays … (Many channels still to be investigated …) F. Dettori poster 10/11/2008 Pascal Perret - LPC Clermont