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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. b Production in LHCb. bb pair production correlated and sharply peaked forward-backward.

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Prospects for New Physics in CP Violation and Rare Decays at LHCb

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  1. 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

  2. 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 • collect 2fb-1 per nominal year • ~ 1012 bb pairs produced per year • 1 LHCb day = 100 B-factory day pp interactions/crossing LHCb n=0 n=1 Pascal Perret - LPC Clermont

  3. LHCb overview and performance Pascal Perret - LPC Clermont

  4. 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 Pascal Perret - LPC Clermont

  5. 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 Pascal Perret - LPC Clermont

  6. 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. Pascal Perret - LPC Clermont

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

  8. 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 … Pascal Perret - LPC Clermont

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

  10. LHCb trigger system • Two levels: • 1st level: hardware 4 ms latency “moderate” pTm, e, g & hadrons, e.g. pTm >1.3 GeV/c : full custom made • HLT: software ~2000 CPU (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 Storage(event size ~ 35 kB) 2 kHz Pascal Perret - LPC Clermont

  11. 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 Splashy event from lost particles (not all tracks reconstructed...) Top view Muon Calo OT Calo OT Muon Velo Side view Clean event from halo muons Pascal Perret - LPC Clermont

  12. Penguin diagram Box diagram Bd0  J/yKS0 Bd0  DK*0 BS0  DSK Bd0  D* p,3p New Physics in CPV Unitarity Triangles Bd0  p+ p- Bd0  rp BS0  DS p a Bd * * VudVub VtdVtb g b * VcdVcb Bs * VusVub * VtsVtb bs * VcsVcb BS0  J/y f Overconstrain the unitarity triangles (consistency checks) Pascal Perret - LPC Clermont

  13. Penguin diagram Box diagram Bd0  J/yKS0 Bd0  DK*0 BS0  DSK Bd0  D* p,3p New Physics in CPV Unitarity Triangles Bd0  p+ p- Bd0  rp BS0  DS p New particles may show up in loop process a Bd * * VudVub VtdVtb ? g b * VcdVcb ? Bs * VusVub New Physics * VtsVtb bs * VcsVcb BS0  J/y f 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 Pascal Perret - LPC Clermont

  14.  Measurements from Bs Ds K+ • Interference between 2 tree diagrams via Bs mixing: • BsDs K(b  c) andBsDsK(b  u) (+ CP conjugates) • Measure  + sin a clean way (no theoretical uncertainty) from time dependent rates • Use s from Bs J/y f • Include BsDs(20x Br) to determine ΔmsΔΓsand tagging dilution • Simultaneous fit to Bs→Ds andBs→DsKdecay time distributions (tagged and untagged) 10 fb-1 data: Bs→Ds-p+ Bs→ Ds-K+ (Dms = 20) Pascal Perret - LPC Clermont

  15.  Measurements • Differentways to measureatLHCb: • 2 amplitudes, b→c (dominant) & b→u (color suppressed), interfere in decays to a common D0 and D0 modes state: Treedecaysonly Global fit of all the channels: σ(g) = 4.3-6.2° with 2fb-1 • 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 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+, … Pascal Perret - LPC Clermont

  16. fsmeasurements 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 Bsflavour : • Combined = 6.2% • Good mass resolution: 13 MeV • Good particle identification • e(KK)~80% e (pK)~ 3% +NP? Invariant mass of BsJ/() Pascal Perret - LPC Clermont

  17. fsmeasurements 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 Pascal Perret - LPC Clermont

  18. New Physics in rare decays Pascal Perret - LPC Clermont

  19. AFB(s), theory s = (m)2 [GeV2] 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, ? • 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 Pascal Perret - LPC Clermont

  20. 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 AFB An example 0.5fb-1experiment More complex fit methods being evaluated q2(GeV2) Pascal Perret - LPC Clermont

  21. New Physics in Bsm+m- MSSM SM SM • 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 ? ? ~ tan6/MH2 CDF Sensitivity with 8fb-1? Pascal Perret - LPC Clermont

  22. 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 Pascal Perret - LPC Clermont

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