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A Possible (Near) Future

at LHCb William Reece on behalf of the LHCb collaboration Imperial College London Beauty ‘09, Heidelberg, 7 th -11 th September 2009. 2fb -1 is one nominal year of running. A Possible (Near) Future. 0.1fb -1 ~ 320 events. SM. Generator Events - Signal only.

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A Possible (Near) Future

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  1. at LHCbWilliam Reece on behalf of the LHCb collaborationImperial College LondonBeauty ‘09, Heidelberg, 7th-11th September 2009

  2. 2fb-1 is one nominal year of running A Possible (Near) Future 0.1fb-1 ~ 320 events SM Generator Events - Signal only William Reece - Imperial College London

  3. 2fb-1 is one nominal year of running A Possible (Near) Future 0.5fb-1 ~ 1600 events SM Generator Events - Signal only William Reece - Imperial College London

  4. 2fb-1 is one nominal year of running A Possible (Near) Future 1fb-1 ~ 3200 events SM Generator Events - Signal only William Reece - Imperial College London

  5. 2fb-1 is one nominal year of running A Possible (Near) Future 2fb-1 ~ 6400 events SM Line from JHEP 0811:032,2008 NLO Model Independent MC Model: A. Bharucha & WR, Preliminary SM FBMSSM Generator Events - Signal only Generated with FBMSSM [Altmannshofer, Ball, Bharucha, Buras, Straub, Wick, (JHEP 0901:019,2009)] (LHCb would observe with ~0.1fb-1 in this scenario)

  6. First observed at Belle • Particles in Loop • Both neutral and charged NP(replace W±, Z0/g, u/c/t) • Sensitive to NP in loops • Use OPE: Model independent • Dominated by C7, C9, C10 in SM • Enhance other operators with NP • Measure Wilson coefficients • Discover or limit NP in loop O7g O9,10 See G. Hiller’s talk for more info William Reece - Imperial College London

  7. Decay Kinematics • Decay described in terms of 3 Angles and 1 Invariant Mass • θl, θK, f and q2, the invariant mass squared of m pair William Reece - Imperial College London

  8. What to Measure? ~ 4/3 AFB (CP Ave.) • Angular observables • Small theory uncertainties • Experimentally accessible • E.g. forward-backward asymmetry of mpair (AFB) • Sensitive to interferencebetween • Plausible NP models • Large deviations • Zero-crossing point (q20) • Accessible with small integrated luminosities (~0.5fb-1) • Form factors cancelat leading order Altmannshoferet al, JHEP 0901:019,2009 William Reece - Imperial College London

  9. Current Status Belle 2009 Change in sign convention Belle (2009) – 0904.0770 BaBar (2008) – PR D79:031102 BaBar 2008 q2(GeV2/c4) BaBar (2008) ~100 events, Belle (2009) ~ 250 events ~0.1fb-1 data set will give LHCb the same statistics as currently availableLHCb (2fb-1) ~ 6.4k events Observables only reliably calculable in q2 region 1-6 GeV2/c4 Up to LHCb to see what is really going on! (SM + Errors from [JHEP 0811:032,2008]) William Reece - Imperial College London

  10. Selecting Signal at LHCb • LHC Challenging Environment • LHCb Optimized for B-physics • Bd vertex res. ~110mm • Track momentum ~0.5% • Bd mass res. ~ 14 MeV • Goodm ID performance key • 93% efficient with 1% mis-ID • p/K separation from RICHs • Important for selection William Reece - Imperial College London

  11. Acceptance Effects • Geometry & reconstructionbiases angular distribution • Few events in θl tails • Large asymmetry • Tend to loose these eventsat low q2 as one μ is soft • pT cuts make effect worse must avoid • Can bias AFB distribution • Must be careful in selections • σ(10%) on acceptance fn. ~5% effect on AFB Effect of geometry & reconstruction on signal efficiency (full MC) Toy MC

  12. Acceptance Effects • Geometry & reconstructionbiases angular distribution • Few events in θl tails • Large asymmetry • Tend to loose these eventsat low q2 as one μ is soft • pT cuts make effect worse must avoid • Can bias AFB distribution • Must be careful in selections • σ(10%) on acceptance fn. ~5% effect on AFB Effect of a 300 MeVμpTcut on signal efficiency (toy MC) Effect of geometry & reconstruction on signal efficiency (full MC) Toy MC

  13. Offline Selection Background Signal • Investigated Fisher • Improves selection efficiency and signal/background over cut-based • Important variables: • Bd: flight & IP significance, pT • K & π: PID, IP significance • 2fb-1 yield estimate • Sig. 6400±1600, Bg. 1590±320 • S/√(S+B) = 71±11 • Total ε: 1.08±0.01 % in 4π Tail of Fisherdiscriminant Cut at 0.38 S/√(S+B) = 71±11 William Reece - Imperial College London

  14. BdK*mm BdJ/ψ K* Acceptance Effects II Trigger Selection Offline Selection • Trigger & offline selection • No further significantbiases introduced • Detector effects dominant • Will be source of systematic uncertainty • Can use MC • Correct with data? • Use BdJ/ψ(μμ) K*as control channel • Collect with sametrigger & selection Must understand the effect dueto different kinematics William Reece - Imperial College London

  15. Counting Experiments for AFB Binned in q2 Simple Counting • Can extract AFB by countingforward and backward m • Relatively simple • Small integrated luminosity • Allows zero-crossing extraction • s(q20) ~ 0.8 GeV2/c4 (0.5 fb-1); 0.5 GeV2/c4 (2 fb-1) • Also unbinned counting in q2 with polynomials s(q20) a AFB gradient q2 • Fit in mass peak & sidebandsfor backgroundSig: 3rd orderBG: 1st order Combine to get corrected AFB. s(q20) ~ 0.5 for 2 fb-1 forward backward CERN-LHCb-2009-03 q2 (GeV2/c4) q2 (GeV2/c4) q2 (GeV2/c4)

  16. Assumes all NP in C7 and C7’, and all real JHEP 0807:106, 2008. Other Observables AllowedRegions • AFB most sensitive to C7 & C9 • Must consider other observables • Combine for full discovery power • Interested in C7’, C9’, C10’ • NP phases also possible • Must look at CP asymmetries too • Focus on C7’ here • Right-handed partner of C7 • Helicity suppressed by ms/mbin the SM • Current constraints driven by SM William Reece - Imperial College London

  17. MSSM: C7’ ≠ 0 Beyond AFB (C7’) • Access C7’ in AT(2) • Theoretically clean:FF cancel at LO like AFB zero • Access in ϕ angle oscillation • Kruger & Matias, Phys.Rev.D71:094009, 2005. • CERN-LHCb-2008-057, CERN-LHCb-PUB-2009-08 • Study in projection fits or3D fit to (low q2) • Similar C7’ sensitivity to • Also get via S5 observable • Has a zero-crossing point in SM • Altmannshoferet al, JHEP 0901:019,2009 • Component of angular distribution SM JHEP 0811:032,2008

  18. Counting Expt. for S5 Toy MC 2fb-1 SM • Good for early data • Zero-crossing • Steeper gradientthan AFB in SM smaller uncertainty • Must understand acceptance • Complicated (two angles) • Sensitive to C7, C7’, C9, C10’ • Complementary to AFB A. Bharucha, WR, preliminary MFV MSSM JHEP 0901:019,2009 William Reece - Imperial College London

  19. Tagged CP Asymmetries GMSSMI:Arg(C7’) ≈ -3π/4 • Reconstruct mode  self tagging • Search for direct CP violation  phase in Wilson coefficients • Large phases allowed • Experimental precisiongood enough to measure • Extract CP asymmetriesfrom angular distribution • Best precision usingfull angular analysis LHCb 10fb-1 SM 1, 2s Egede, Hurth, Matias, Ramon, WRPreliminary William Reece - Imperial College London

  20. SM Theory Distribution Toy fits to SUSY model b (C’7 != 0) 1, 2s Full Angular Analysis CERN-LHCb-2008-041JHEP 0811:032,2008 • Perform fit for spin amplitudes • Assume polynomial q2 variation • Calculate any observable from amplitudes • New observables AT(3) AT(4)optimized for C7’ sensitivity • 10fb-1 sensitivities for SUSY input • JHEP 0704 (2007) 058 – model ‘b’ • Allowed by experimental constraints • MC Fits converge with 2fb-1 • 3D acceptance a challenge • Hope to extract from data LHCb 10fb-1 William Reece - Imperial College London

  21. Summary • Excellent prospects for discovery of NP • Hints from B-factories? • Expect 6.4k signal events per year (2fb-1) • Whole q2 range • 0.1fb-1 gives ~350 eventsSame as all current experiments combined • Exciting Physics program • Many observables to study • CP conserving and violating • Real discriminating power for NP William Reece - Imperial College London

  22. Back UP Slides William Reece - Imperial College London

  23. Finding New Physics in C7 AT(3) Theory + LHCb 10fb-1 C7 = C7SM + C7NP Egede, Hurth,Matias, Ramon,WR. Preliminary After 10fb-1Analysis? SM AT(4) Theory + LHCb 10fb-1 (0.083,-0.21) William Reece - Imperial College London

  24. Hardware Trigger Strategy • Current L0 Trigger selects~93% of offline events • Three lines: • Single μ: pT > 1.3 GeV (90%) • Di-μ: ∑pT > 1.5 GeV, pT > 100 MeV (63%) • Hadron: Calo ET > 3.5 GeV (20%) • (Di-μ) pT cuts bias AFB shape • Avoid further cuts in HLT and offline selection • HLT: Lifetime biased (IP, Vertex displacement) • Selects ~90% of offline and L0 events Software William Reece - Imperial College London

  25. Cut Based Selection • Updated detector simulation • Inclusive sampleused for background • Hard cuts: lifetimebiased quantities • Compensates for lack of pT cuts • Optimized to be robust • Still get signal in early data • 2fb-1 yield • Sig. 4300±1100, Bg. 200±140 • S/√(S+B) = 64±9 William Reece - Imperial College London

  26. Outside the Theoretically Clean Region • B  Vector form factors large source of theoretical uncertainty • Dominated by low energy effects • 7 independent functions of q2 – V, T1,2,3, A0,1,2 • Use SCET to reduce 7 2 at Leading Order • Only valid in range 1-6 GeV2/c4 • Can not handle resonances or low q2 region • Observables where 2 remaining FF cancel • AFB zero-crossing point and AT(2,3,4) • Uncertainties outside this region much greater • See Beneke et al, Nucl. Phys. B612 (2001) 26-58 William Reece - Imperial College London

  27. Background at LHCb background from: b→mb→m No. of Events • Dominated by genuine m from Bd • Little mmis-ID in MC • dominant contribution • Symmetric in ql, scales AFB observed • Increases error on zero crossing • significant • Asymmetric in ql, affects AFB • Non-resonant thought to be small • Limits set from • Will measure in data ql / rad background from: b→μ + c, c→μ No. of Events ql / rad William Reece - Imperial College London

  28. Drell-Yan Backgrounds • Not significant background at LHCb • Full simulation study: • decays dominant source of mm in mass range • Drell-Yan production much lower • Reconstruction Efficiency: • Fake signal  need a K* from elsewhere • Wrongly associate this with mm vertex • Mis-ID rate should be very low William Reece - Imperial College London

  29. Massless Projection Fits • Angular projectionsof ql, f, qK distributions • Perform simultaneous fit in q2 bins • Improve precision on AFB by ~2 • Measure new observable AT(2)with poor resolution in 1-6 GeV2/c4region due to (1-FL) suppression • FL(1 ≤ q2 ≤ 6) ≈ 0.86 in SM SM input+ errors LHCb 2fb-1BaBarBelle 08 [CERN-LHCb-2007-057] [Lunghi et al, JHEP 0704 (2007) 058] William Reece - Imperial College London

  30. Projection Fit Resolutions • Results from CERN-LHCb-2007-057 William Reece - Imperial College London

  31. FL small in SM for q2 ≤1GeV2/c4 • Production rate high at low q2 (30-1000 MeV) • Massless approx still valid. Dominated by C7 in SM • Yield ~200 per 2fb-1: Sig./Bg. ~ 1 • AT(2) from 2D or 3D q2 binned fit • Assume acceptance factorizesand ε1 even. Check with full MC • Fold over ϕ and θl • 2fb-1 sensitivity: σ(AT(2)) ~0.2 • Comparable to for AR/AL LHCb full MCFast Sim. William Reece - Imperial College London

  32. Proposed cuts in offline selection William Reece - Imperial College London

  33. Angular Distribution William Reece - Imperial College London

  34. Physics Sensitivity to K* Spin Amplitudes William Reece - Imperial College London

  35. Observables William Reece - Imperial College London

  36. Experimental Constraints for C7 Plot Bobethet al, JHEP 0807:106, 2008. William Reece - Imperial College London

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