1. Toru Iijima & Koji Ikado (Talk presented by T.I.) Nagoya University May 15, 2006 “Flavour in the LHC era” @ CERN The First Evidence of B   from Belle & Future Prospect As a contribution to WG2 (neutrino modes) Ref: K.Ikado’s talk at FPCP06 hep-ex/0604018

2. 2006/05/15Toru Iijima @ Flavour in the LHC era 2 B   (within the SM) Proceed via W annihilation in the SM. Branching fraction is given by Provide information of f B |V ub | –|V ub | from B  X u l f B cf) Lattice (  ~10%) –Br(B   )/  m d |V ub | / |V td | Expected branching fraction HFAG [hep-ex/0603003] HPQCD [PRL95,212001(2005)]

3. 2006/05/15 3 B   X as a Probe to Charged Higgs Charged Higgs contribution to B decays Leptonic: B   Semileptonic: B  D  c b  H/WH/W  H/WH/W  Br(SM) ~ 9 x 10 -5 Decay amplitude Tauonic decay is the most sensitive ! Br(SM) ~ 8 x 10 -3

4. 2006/05/15Toru Iijima @ Flavour in the LHC era 4 Search for B   B   is important for both SM and BSM. Purely leptonic  Theoretically very clean More than two ’s  Experimentally very challenging. Its detection is a milestone of B physics. B factories LEP First Evidence ! April 2006

5. 2006/05/15Toru Iijima @ Flavour in the LHC era 5 B   Analysis Concepts B decays with missing neutrinos lack the kinematic constraints which are used to separate signal events from backgrounds (M bc and  E). Reconstruct the decay of the non-signal B (tagging), then look for the signal decay in whatever is left over Y(4S) B-B- B+B+ ++ More than 2 neutrinos appear in B   decay Tagging side : Fully reconstruct hadronic modes Signal side : Reconstruct particles from  decay

6. 2006/05/15Toru Iijima @ Flavour in the LHC era 6 Features with Fully Reconstructed B Tag Pros: Offline B meson Beam –B momentum is known.  Resolution of M miss 2 can be significantly improved. –B-flavor/charge is known.  We can treat charged & neutral B separately  Large background reduction Cons: Low statistics –Tagging efficiency : 0.2 - 0.3% w/o B momentum with B momentum M miss 2 for B -  D 0    (MC)  Large lum. required !

7. 2006/05/15Toru Iijima @ Flavour in the LHC era 7 Fully Reconstructed Tag at Belle (447M BB) 7 modes 6 modes 2 modes Beam constrained mass Signal region : -0.08 5.27 GeV/c 2 ~10% for feed-across between B + and B 0 m ~ 5.28 GeV/c 2  ~ 3 MeV/c 2 due to  (E beam ) ~ 180 channels used N= 680k eff.= 0.29% purity = 57% N= 680k eff.= 0.29% purity = 57% N = 412 k eff.= 0.19% purity = 52% N = 412 k eff.= 0.19% purity = 52% Charged B Neutral B

8. 2006/05/15Toru Iijima @ Flavour in the LHC era 8 Signal Selection (1)  lepton is identified in the 5 decay modes. Signal selection criteria. Signal-side efficiency including  decay br.) All selection criteria were optimized before examining the signal region (blind analysis). 81% of all  decay modes 32.92  0.12%

9. 2006/05/15Toru Iijima @ Flavour in the LHC era 9 Signal Selection (2) Extra neutral energy in calorimeter E ECL –Most powerful variable for separating signal and background –Total calorimeter energy from the neutral clusters which are not associated with the tag B Minimum energy threshold  Barrel : 50 MeV  For(Back)ward endcap : 100(150) MeV Zero or small value of E ECL arising only from beam background Higher E ECL due to additional neutral clusters MC includes overlay of random trigger data to reproduce beam backgrounds.

10. 2006/05/15Toru Iijima @ Flavour in the LHC era 10 Signal Selection (3) Extra neutral energy E ECL Validation by double tagged sample (control sample); –B tag is fully reconstructed –B sig is semileptonic decays B +  D (*)0 X + (fully reconstruction) B -  D *0 B -  D *0 l - D 0  D 0  0 K -  + K -  + K -  +  -  + K -  +  -  + B+B-B+B- 494  18 B0B0B0B0 7.9  2.2 Total502  18 Data458 Purity ~ 90%

11. 2006/05/15Toru Iijima @ Flavour in the LHC era 11 Background Estimation MC : 23.3  4.7 Data : 21 MC : 94.2  8.0 Data : 96 Large MC samples for e + e -  BB, qq, X u l, X u ,    , and rare B decays are used (including beam-background). Majority come from B  D (*) X l (~90%) + Xu l /rare (~10%). Sideband Total MC : 267  14 Data : 274 MC : 89.6  8.0 Data : 93 MC : 41.3  6.2 Data : 43 MC : 18.5  4.1 Data : 21

12. 2006/05/15Toru Iijima @ Flavour in the LHC era 12 Result: Opening the Box ! The signal regions are examined after finalizing all of the selection criteria. Observe excess in signal region ! 414 fb -1 # estimated background and observed events in the signal region

13. 2006/05/15Toru Iijima @ Flavour in the LHC era 13 B   Candidate Event B +  D 0  + K +  -  +  - K +  -  +  - B -   -  e - e -

14. 2006/05/15Toru Iijima @ Flavour in the LHC era 14 Verification of the Signal (1) For events in the E ECL signal region, distribution of event selection variables other than E ECL are verified. They are consistent with MC expectation for B   signal + background. M bc P miss B   signal Background

15. 2006/05/15Toru Iijima @ Flavour in the LHC era 15 Verification of the Signal(2) About 30% of background have neutral cluster in the KLM detector (K L candidates). The excess remains after requiring K L veto. We do not use this cut in the result, to avoid introducing large systematic error due to K L detection efficiency uncertainty. K L in coincidence. K L in veto E ECL

16. 2006/05/15Toru Iijima @ Flavour in the LHC era 16 The final results are deduced by unbinned likelihood fit to the obtained E ECL distributions. Fit Results Signal shape : Gauss + exponential Background shape : second-order polynomial Signal + background Background B   Signal  : Significance with systematics Observe 21.2 events with a significance of 4.2  +6.7 - 5.7

17. 2006/05/15Toru Iijima @ Flavour in the LHC era 17 Systematic Uncertainty Signal selection efficiencies Tag reconstruction efficiency : 10.5% B -  D *0 l Difference of yields between data and MC in the B -  D *0 l - control sample Number of BB : 1% Signal yield : –signal shape ambiguity estimated by varying the signal PDF parameters –BG shape : changing PDF Total systematic uncertainty +12% -10% +17% -15%

18. 2006/05/15Toru Iijima @ Flavour in the LHC era 18 B   Branching Fraction Branching fractions are calculated by All  decay modes combined Result is consistent with SM prediction within error Extracted branching fraction for each  decay mode SM : B(B   )=(1.59  0.40)×10 -4

19. 2006/05/15 19 f B Extraction Product of B meson decay constant f B and CKM matrix element |V ub | Using |V ub | = (4.39  0.33)×10 -3 from HFAG f B = 0.216  0.022 GeV [HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ] 14% 11% = 8%(exp.) + 8%(V ub )

20. 2006/05/15Toru Iijima @ Flavour in the LHC era 20 Constraints on |V ub |/|V td | Constraint in the ( ,  ) plane from the    branching fraction and  m d Constraint for Improved measurement will help.

21. 2006/05/15Toru Iijima @ Flavour in the LHC era 21 Constraints on Charged Higgs 22 rHrH A 95.5%C.L. exclusion boundaries B A B

22. 2006/05/15Toru Iijima @ Flavour in the LHC era 22 Future Prospect (1) Br(B   ) measurement: Further accumulation of luminosity help to reduce both statistical and systematic errors errors. –Some of the major systematic errors come from limited statistics of the control sample. |V ub | measurement: < 5% in future is an realistic goal. f B from theory ~10% now  5% ? Lum.  B(B   ) exp  |V ub | 414 fb -1 36%7.5% 5 ab -1 10%5.8% 50 ab -1 3%4.4% Assumption in the following plots Note:

23. 2006/05/15 23 Future Prospect (2)  f B (LQCD) = 5% 95.5%C.L. exclusion boundaries rHrH 22 rHrH 5ab -1 50ab -1 If  |V ub | = 0 &  f B = 0

24. 2006/05/15Toru Iijima @ Flavour in the LHC era 24 Future Prospect (3) Charged Higgs Mass Reach (95%CL @ tan  =30) Only exp. error (  V ub =0%,  f B =0%)  V ub =5%,  f B =5%  V ub =2.5%,  f B =2.5% 51020304050 Luminsoity(ab -1 ) Mass Reach (GeV) 1TeV

25. 2006/05/15Toru Iijima @ Flavour in the LHC era 25 f D measurements

26. 2006/05/15Toru Iijima @ Flavour in the LHC era 26 Summary We have seen the evidence of B   with 414fb -1 data at Belle. –The first evidence of purely leptonic B decays. –Branching fraction –B decay constant –Constraint on charged Higgs. O(ab -1 ) data, together with improved f B and |V ub |, will allow us to probe large tanb-mass space of charged Higgs. Probe up to ~200GeV at tan  =30

27. 2006/05/15Toru Iijima @ Flavour in the LHC era 27 Backup Slides

28. 2006/05/15Toru Iijima @ Flavour in the LHC era 28 Fit Result (2) Likelihood fit results for each  decay mode. Signal Background Signal + background

29. 2006/05/15Toru Iijima @ Flavour in the LHC era 29 Fit Results (3) Likelihood distributions for each  decay mode.

30. 2006/05/15Toru Iijima @ Flavour in the LHC era 30 Future Prospect (5ab -1 )  f B (LQCD) = 5%  f B (LQCD) = 10% 95.5%C.L. exclusion boundaries 22 rHrH 22 rHrH

31. 2006/05/15Toru Iijima @ Flavour in the LHC era 31 Full Reconstruction Method Fully reconstruct one of the B’s to tag –B production –B flavor/charge –B momentum Υ(4S) e  (8GeV) e+(3.5GeV) B B  full (0.1~0.3%) reconstruction B  D  etc. Single B meson beam in offline ! Decays of interests B  Xu l, B  K  B  D ,  Powerful tools for B decays w/ neutrinos

32. 2006/05/15Toru Iijima @ Flavour in the LHC era 32 Search for Charged Higgs B  D  (semileptonic decay) c b  H/WH/W  Band width from form-factor uncertainty Full reconstruction tag Signal  large missing mass Expected at 5ab -1 ModeNsigNbkgdB/B 2805507.9% 6203600

33. 2006/05/15Toru Iijima @ Flavour in the LHC era 33 Constraint to Charged Higgs Once branching fraction is measured, we can constrain R. Form factor error M.Tanaka, Z.Phys. C67 (1995) 321 at 5ab -1  can be determined experimentally by B semiletonic decays

34. 2006/05/15Toru Iijima @ Flavour in the LHC era 34 Sensitivity for Charged Higgs  (Form-factor) ~5%  (Form-factor) ~15% BDBD B   (present) Constraint from B  Xs  LHC 100fb -1  (form-factor) can be reduced with the present B  D  data.