1. at LHCb William Reece on behalf of the LHCb collaboration Imperial College London Beauty ‘09, Heidelberg, 7 th -11 th September 2009

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

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

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

5. A Possible (Near) Future Page 5 2fb -1 ~ 6400 events 2fb -1 is one nominal year of running SM 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) FBMSSM SM Line from JHEP 0811:032,2008 NLO Model Independent MC Model: A. Bharucha & WR, Preliminary

6. First observed at Belle – Particles in Loop –Both neutral and charged NP (replace W ±, Z 0 / , u/c/t) Sensitive to NP in loops –Use OPE: Model independent Dominated by C 7, C 9, C 10 in SM –Enhance other operators with NP Measure Wilson coefficients –Discover or limit NP in loop William Reece - Imperial College LondonPage 6 O7O7 O 9,10 See G. Hiller’s talk for more info

7. William Reece - Imperial College LondonPage 7 Decay Kinematics Decay described in terms of 3 Angles and 1 Invariant Mass –θ l, θ K,  and q 2, the invariant mass squared of  pair

8. What to Measure? Angular observables –Small theory uncertainties –Experimentally accessible E.g. forward-backward asymmetry of  pair (A FB ) –Sensitive to interference between Plausible NP models – Large deviations Zero-crossing point (q 2 0 ) –Accessible with small integrated luminosities (~0.5fb -1 ) –Form factors cancel at leading order William Reece - Imperial College LondonPage 8 Altmannshofer et al, JHEP 0901:019,2009 ~ 4/3 A FB (CP Ave.)

9. Current Status William Reece - Imperial College London BaBar (2008) ~100 events, Belle (2009) ~ 250 events ~0.1fb -1 data set will give LHCb the same statistics as currently available LHCb (2fb -1 ) ~ 6.4k events Observables only reliably calculable in q 2 region 1-6 GeV 2 /c 4 Up to LHCb to see what is really going on! (SM + Errors from [JHEP 0811:032,2008]) Page 9 Belle 2009 BaBar 2008 Belle (2009) – 0904.0770 BaBar (2008) – PR D79:031102 Change in sign convention q 2 (GeV 2 /c 4 )

10. LHC Challenging Environment –LHCb Optimized for B-physics B d vertex res. ~110  m Track momentum ~0.5% –B d mass res. ~ 14 MeV Good  ID performance key –93% efficient with 1% mis-ID  /K separation from RICHs –Important for selection Selecting Signal at LHCb William Reece - Imperial College LondonPage 10

11. Toy MC Acceptance Effects Geometry & reconstruction biases angular distribution Few events in θ l tails –Large asymmetry –Tend to loose these events at low q 2 as one μ is soft p T cuts make effect worse  must avoid Can bias A FB distribution –Must be careful in selections –σ(10%) on acceptance fn.  ~5% effect on A FB Page 11 Effect of geometry & reconstruction on signal efficiency (full MC)

12. Toy MC Acceptance Effects Geometry & reconstruction biases angular distribution Few events in θ l tails –Large asymmetry –Tend to loose these events at low q 2 as one μ is soft p T cuts make effect worse  must avoid Can bias A FB distribution –Must be careful in selections –σ(10%) on acceptance fn.  ~5% effect on A FB Page 12 Effect of geometry & reconstruction on signal efficiency (full MC) Effect of a 300 MeV μ p T cut on signal efficiency (toy MC)

13. Offline Selection Investigated Fisher –Improves selection efficiency and signal/background over cut-based Important variables: –B d : flight & IP significance, p T –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 William Reece - Imperial College LondonPage 13 Tail of Fisher discriminant Cut at 0.38 S/√(S+B) = 71±11 Signal Background

14. Trigger Selection Offline Selection Acceptance Effects II Trigger & offline selection –No further significant biases introduced Detector effects dominant –Will be source of systematic uncertainty Can use MC Correct with data? –Use B d  J/ψ(  μμ) K* as control channel –Collect with same trigger & selection William Reece - Imperial College LondonPage 14 B d  K*  B d  J/ψ K* Must understand the effect due to different kinematics

15. q 2 (GeV 2 /c 4 ) forward Counting Experiments for A FB Can extract A FB by counting forward and backward  –Relatively simple –Small integrated luminosity Allows zero-crossing extraction –  (q 2 0 ) ~ 0.8 GeV 2 /c 4 (0.5 fb -1 ); 0.5 GeV 2 /c 4 (2 fb -1 ) Also unbinned counting in q 2 with polynomials  (q 2 0 )  A FB gradient Binned in q 2 Simple Counting q 2 (GeV 2 /c 4 ) backward Fit in mass peak & sidebands for background Sig: 3 rd order BG: 1 st order CERN-LHCb-2009-03 Combine to get corrected A FB.  (q 2 0 ) ~ 0.5 for 2 fb -1 q 2 (GeV 2 /c 4 ) Page 15 q2q2

16. Allowed Regions Assumes all NP in C 7 and C 7 ’, and all real SM A FB most sensitive to C 7 & C 9 –Must consider other observables Combine for full discovery power Interested in C 7 ’, C 9 ’, C 10 ’ –NP phases also possible –Must look at CP asymmetries too Focus on C 7 ’ here –Right-handed partner of C 7 –Helicity suppressed by m s /m b in the SM –Current constraints driven by Other Observables William Reece - Imperial College LondonPage 16 JHEP 0807:106, 2008.

17. MSSM: C 7 ’ ≠ 0 SM JHEP 0811:032,2008 Beyond A FB (C 7 ’) Access C 7 ’ in A T (2) –Theoretically clean: FF cancel at LO like A FB 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 or 3D fit to (low q 2 ) –Similar C 7 ’ sensitivity to Also get via S 5 observable –Has a zero-crossing point in SM Altmannshofer et al, JHEP 0901:019,2009 –Component of angular distribution Page 17

18. Counting Expt. for S 5 Good for early data Zero-crossing –Steeper gradient than A FB in SM  smaller uncertainty Must understand acceptance –Complicated (two angles) Sensitive to C 7, C 7 ’, C 9, C 10 ’ –Complementary to A FB William Reece - Imperial College LondonPage 18 A. Bharucha, WR, preliminary Toy MC 2fb -1 SM JHEP 0901:019,2009 MFV MSSM

19. Tagged CP Asymmetries Reconstruct mode  self tagging –Search for direct CP violation  phase in Wilson coefficients William Reece - Imperial College LondonPage 19 GMSSM I : Arg(C 7 ’) ≈ -3π/4 Large phases allowed –Experimental precision good enough to measure Extract CP asymmetries from angular distribution –Best precision using full angular analysis LHCb 10fb -1 SM Egede, Hurth, Matias, Ramon, WR Preliminary 1, 2 

20. Full Angular Analysis Perform fit for spin amplitudes – –Assume polynomial q 2 variation Calculate any observable from amplitudes –New observables A T (3) A T (4) optimized for C 7 ’ 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 William Reece - Imperial College LondonPage 20 CERN-LHCb-2008-041 JHEP 0811:032,2008 SM Theory Distribution Toy fits to SUSY model b (C’ 7 != 0) 1, 2  LHCb 10fb -1

21. Summary Excellent prospects for discovery of NP –Hints from B-factories? Expect 6.4k signal events per year (2fb -1 ) –Whole q 2 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 LondonPage 21

22. BACK UP SLIDES William Reece - Imperial College LondonPage 22

23. Finding New Physics in C 7 William Reece - Imperial College LondonPage 23 A T (3) Theory + LHCb 10fb -1 A T (4) Theory + LHCb 10fb -1 Egede, Hurth, Matias, Ramon, WR. Preliminary (0.083,-0.21) C 7 = C 7 SM + C 7 NP SM After 10fb -1 Analysis?

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

25. Cut Based Selection Updated detector simulation –Inclusive sample used for background Hard cuts: lifetime biased quantities –Compensates for lack of p T 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 LondonPage 25

26. Outside the Theoretically Clean Region B  Vector form factors large source of theoretical uncertainty –Dominated by low energy effects –7 independent functions of q 2 – V, T 1,2,3, A 0,1,2 Use SCET to reduce 7  2 at Leading Order –Only valid in range 1-6 GeV 2 /c 4 –Can not handle resonances or low q 2 region Observables where 2 remaining FF cancel –A FB zero-crossing point and A T (2,3,4) Uncertainties outside this region much greater See Beneke et al, Nucl. Phys. B612 (2001) 26-58 William Reece - Imperial College LondonPage 26

27. Dominated by genuine  from B d –Little  mis-ID in MC dominant contribution –Symmetric in  l, scales A FB observed –Increases error on zero crossing significant –Asymmetric in  l, affects A FB Non-resonant thought to be small –Limits set from –Will measure in data Background at LHCb William Reece - Imperial College LondonPage 27 No. of Events background from: b→μ + c, c→μ background from: b→  No. of Events  l / rad

28. Drell-Yan Backgrounds Not significant background at LHCb Full simulation study: – decays dominant source of  in mass range –Drell-Yan production much lower Reconstruction Efficiency: 1.Fake signal  need a K* from elsewhere 2.Wrongly associate this with  vertex 3.Mis-ID rate should be very low William Reece - Imperial College LondonPage 28

29. SM input + errors Angular projections of  l, ,  K distributions Perform simultaneous fit in q 2 bins Improve precision on A FB by ~2 Measure new observable A T (2) with poor resolution in 1-6 GeV 2 /c 4 region due to (1-F L ) suppression –F L (1 ≤ q 2 ≤ 6) ≈ 0.86 in SM Massless Projection Fits [CERN-LHCb-2007-057] [Lunghi et al, JHEP 0704 (2007) 058] LHCb 2fb -1 BaBar Belle 08 William Reece - Imperial College LondonPage 29

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

31. F L small in SM for q 2 ≤1GeV 2 /c 4 Production rate high at low q 2 (30-1000 MeV) –Massless approx still valid. Dominated by C 7 in SM Yield ~200 per 2fb -1 : Sig./Bg. ~ 1 A T (2) from 2D or 3D q 2 binned fit –Assume acceptance factorizes and ε 1 even. Check with full MC –F old over ϕ and θ l 2fb -1 sensitivity: σ(A T (2) ) ~0.2 –Comparable to for A R /A L William Reece - Imperial College LondonPage 31 LHCb full MC Fast Sim.

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

33. Angular Distribution William Reece - Imperial College LondonPage 33

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

35. Observables William Reece - Imperial College LondonPage 35

36. Experimental Constraints for C 7 Plot William Reece - Imperial College LondonPage 36 Bobeth et al, JHEP 0807:106, 2008.