1. Rare B Decays with “Missing Energy” Tom Browder (University of Hawaii) Will discuss experimental results from Belle on B   ν (BELLE-CONF-0671) and B  K * νν (BELLE-CONF-0627) Representing the Belle Collaboration All results discussed here are preliminary.

2.  decay constant Motivation for B +  + ν BF(B +   + ν) < 2.6 x 10 -4 (BaBar) B. Aubert et al., PRD 73, 057101 (2006) Most stringent published limit: Sensitivity to new physics from charged Higgs if the B decay constant is known

3. Why measuring    ν  is non-trivial  (4S) B-B- B+B+  e+e+  e B +  + ,  +  e + e  B-XB-X The experimental signature is rather difficult: B decays to a single charged track + nothing Most of the sensitivity is from tau modes with 1- prong

4. Belle’s sample of B tags (447 x 10 6 BB) 7 modes 6 modes 2 modes Beam constrained mass distn’s Signal region : -0.08 5.27 GeV/c 2 ~10% feed-across between B + and B 0 m ~ 5.28 GeV/c 2  ~ 3 MeV/c 2 from  (E beam ) ~ 180 channels reconstructed Charged B ’ s Neutral B ’ s N=680 K Eff=0.29% Purity =57% N=412 K Eff=0.19% Purity =52%

5. Reconstruct one B (B tag ) in a charged hadronic b  c mode (remove tag’s decay products from consideration.) Little or no extra electromagnetic calorimeter energy (E ECL ). Beam-related backgrounds modeled in MC using random trigger data runs. · For B  X n known E B, m B, small p B –  narrow missing mass distn. (m n ~0) · Two missing neutrinos, large missing p (cut depends on  decay mode 0.2 GeV-1.8 GeV) Outline of B   νexperimental analysis

6. Outline of experimental analysis (cont’d) The  lepton is identified in the 5 decay modes: Signal-side efficiency including  decay BFs) All selection criteria were optimized before examining the signal region (a.k.a. blind analysis) Fit the extra energy distribution (E ECL ), the signal peaks near zero 81% of all  decays 15.81  0.05%

7. Consistency Check with B  D * l ν Extra neutral energy E ECL Validation with double tagged sample (control sample); –B tag is fully reconstructed –B sig is a semileptonic decay 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% Extra energy in the calorimeter Calibration data

8. Example of a B   ν candidate Tag: B  D 0 , D 0  K 

9. Evidence for B +   ν (Belle) Find signal events from a fit to a sample of 54 events. 4.6  stat. significance w/o systematics, 447  10 6 B pairs B tag  D (*) [ ,a 1,D s (*) ] 680k tags, 55% pure. 5  decay modes MC studies show there is a small peaking bkg in the    0 and    0 modes. After including systematics (dominated by bkg), the significance decreases to 3.5σ Extra Calorimeter Energy

10. B   yields broken down by  decay mode For the first 3 modes, the background is fitted with a 2 nd order polynomial plus a small Gaussian peaking component. (stat sig only)

11. Error in the efficiency calculation Due to a coding error, the efficiency quoted in the 1 st Belle preliminary result was incorrect. The data plots and event sample are unchanged. However, f B and the branching fraction must be changed. This mistake was not detected when checking the B  D* l control sample or in the internal review process. Previous value New value (Preliminary)

12. Direct experimental determination of f B 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 = 216  22 MeV (an unquenched lattice calc.) [HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ] 15%14% = 12%(exp.) + 8%(V ub ) ( Belle)

13. Constraints on the charged Higgs mass r H =1.13  0.51 Assume f B and |V ub | are known, take the ratio to the SM BF.

14. Motivation for B  K * (b  s with 2 neutrinos) SM: BF(B  K * ) ~1.3 x 10 -5 (Buchalla, Hiller, Isidori) BSM: New particles in the loop c.f. SM: BF(B  K - ) ~4 x 10 -6 PRD 63, 014015 [Belle preliminary (275 x 10 6 B Bbar) : BF(B  K - ) <3.6 x 10 -5 ] to be updated soon Other weakly coupled particles: light dark matter

15. B  K (*) νν are particularly interesting and challenging modes (B   ν is even a small background) The experimental signature is B  K + Nothing The “nothing” can also be light dark matter (mass of order (1 GeV)) (see papers by M. Pospelov et al.) (But need to optimize p K cut) DAMA NaI 3  Region CDMS 04 CDMS 05 Direct dark-matter searches cannot see M<10 GeV region C. Bird et al PRL 93 201803.(T. Adams et al. PRL 87 041801;A. Dedes et al., PRD 65 015001)

16. Search for B  K * (532 x 10 6 B Bbar pairs) (at 90% C.L) Extra Calorimeter Energy (GeV) (1.7σ stat. significance) Sideband = 19 MC expectation = 18.7  3.3 SM (Buchalla, Hiller, Isidori) 1.3 x 10 -5 BELLE-CONF- 0627 Result from a blind analysis.

17. Search for B  K * (properties of candidates) KπInv. mass b  c background rare B background (x 15 data) udsc background Data combined background Signal x 20

18. P*_K* b  c background rare B background (x 15 data set) udsc background Data combined background Signal shape Search for B  K * (properties of candidates) K * momentum distribution Need more b  c MC (only 2 x data)

19. π+π+ K- γ Tag Side B  D + a1 - D +  K - π + π + a1 -  ρ 0 π -, ρ 0  π + π - Event display for a B  K * candidate due to an identified background (B  K * γ) (Hard photon is lost in the barrel-endcap calorimeter gap) Missing mass ~ 0 MC: Expected bkg from this source ~0.3 evts.

20. 20 Future Prospects: B    f B (LQCD) = 5% 95.5%C.L. exclusion boundaries rHrH 50ab -1 If  |V ub | = 0 &  f B = 0 Lum.  B(B   ) exp  |V ub | 414 fb -1 36%7.5% 5 ab -1 10%5.8% 50 ab -1 3%4.4% Extrapolations (T.Iijima)

21. 21 Future Prospects: Other probes of charged Higgs c b  H/WH/W  Decay amplitude Expected BF(SM)~ 8 x 10 -3 Semileptonic: B  D (*)  Multiple neutrinos, low momentum lepton (use e’s), large bkg but still might be possible with enough data.

22. Some modes are very difficult at hadron colliders MC extrapolation to 50 ab  1 Observation of B ±  K ±  55 Super B LoI Fig.4.18 (compare to K +   + νν and K L   0 Extra EM calorimeter energy Belle result on B   ν shows that B to one prong decays can be measured. MC SM pred: G. Buchalla, G. Hiller, G. Isidori (PRD 63 014015 )

23. Conclusions on “Missing Energy Decays” Evidence for B   νand experimental determination of f B (preliminary result has been updated) Search for B  K * (UL is still a factor of 10 above the SM range) Further dramatic progress (e.g. signals for B  K (*) νν) will require Super B Factory class luminosity.

24. Backup Slides

25. Contributions to systematic error for B  

26. Peaking Backgrounds in B   Tau tagging mode

27. Fits to individual B   decay modes (updated for ICHEP06)

28. Requirements in B   ν analysis The  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 15.81  0.05%

29. 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

30. 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 a large systematic error due to the uncertainty in K L detection efficiency. K L in coincidence. K L in veto E ECL

31. Selection Requirements for B  K * MC signal and bkg distributions,

32. γ K- π+π+ tagB Tag Side B  D + a1 - D +  K - π + π + a1 -  ρ 0 π -, ρ 0  π + π -