1. Toru Iijima Nagoya University December 19, 2006 BNM-II Workshop, Nara-WU Tauonic and Leptonic Decays

2. 2 Contents Introduction B   B  D , X  B  l B  ll (ee, ,  ) B  K (*)  Technical issues; - Tagging - Background ’s in the final state (missing energy)

3. 3 Hunting Rare Decays Observation of B  K l + l - CPV in B decay Beginning of B->  K 0 saga Direct CPV in B 0  K +   FB asymmetry in B  K* l + l - Evidence of B   Observation of b  d  High luminosity Good detector (PID, vertex…) Analysis techniques –qq background suppression –Fully reconstructed tag Success of B factories brought rare B decays in leptonic and neutrino modes on the stage ! Success of B factories brought rare B decays in leptonic and neutrino modes on the stage !

4. 4 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

5. 5 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)]

6. 2006/05/15 6 B   X as a Probe to Charged Higgs Charged Higgs contribution to B decays In two Higgs doublets model, charged Higgs exchange interferes with the helicity suppressed W-exchange. H/WH/W  Br(SM) ~ 9 x 10 -5

7. 7 The final results are deduced by unbinned likelihood fit to the obtained E ECL distributions. The First B   Evidence Signal shape : Gauss + exponential Background shape : second-order polynomial + Gauss (peaking component) Signal + background Background B   Signal Observe 17.2 events in the signal region. Significance decreased to 3.5  after including systematics +5.3 - 4.7  : Statistical Significance To appear in Phys. Rev. Lett. hep-ex/0604018v3

8. 8 Results (Br & f B Extraction) Measured branching fraction; 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 [HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ] 15% 16% = 14%(exp.) + 8%(V ub )

9. 9 Constraints on Charged Higgs f B from HPQCD These regions are excluded. Much stronger constraint than those from energy frontier exp’s. |V ub | stat.syst. fBfB |V ub | from HFAG

10. 10 Future Prospect: B   Br(B   ) measurement: More luminosity help to reduce both stat. and syst. errors. –Some of the syst. errors limited by 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% My assumption  f B (LQCD) = 5% 5ab -1 50ab -1 If  |V ub | = 0 &  f B = 0

11. 11 Cont’d Charged Higgs Mass Reach (95.5%CL exclusion @ 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% Mass Reach (GeV) Luminsoity(ab -1 )

12. Constraints at Super-B (cont.)  f B (LQCD) = 5% rHrH 55 rHrH 5ab -1 50ab -1 5  potential 55 Charged Higgs Mass Reach with 5 

13. 13 Ratio may help ? Ratio to cancel out f B (G.Isidori&P.Paradisi, hep-ph/0605012) Deviation of Br. exp. |V ub | fBfB exp. |V ub | B Bd

14. 14 B  D (*)  Semileptonic tauonic decays c b  H/WH/W  Br(SM) ~ 8 x 10 -3 –Ratio (  /  ) is modified by the charged Higgs effect. –Provide good cross check to B   –Y.Okada H-b-u vertex by B   H-b-c vertex by B  D  H-b-t vertex by LHC direct search.

15. 15 LoI 5ab -1 50ab -1 ModeNsigNbkg  dB/BNsigNbkg  dB/B 280550 12.77.9% 28005500 40.32.5% 62036006200 36000 Expectation at 5 / 50 ab -1 for B + decay 5  observation possible at 1ab -1 Signal selection efficiency 10.2% 2.6% 26.1% 13.3% Major background source Missing charged and  tracks from B  D (*) l X (incl. slow  )

16. 16 Sensistivity to H ± Similar to B   5ab -1  FF =15% 50ab -1  FF =5%

17. 17 B   e  B   is the next milestone decay. When do we see the signal ? Precision at Super-B ? Precise B   /  data provide lepton universality test. –Higgs effect itself is universal. R H  = R H  –Good probe to distinguish NP models. Br(  )=1.6x10 -4 Br(  )=7.1x10 -7 Br(e )=1.7x10 -11

18. 18 Belle Results Inclusive reconstruction –Reconstruct the accompanying B via a 4-vector sum of everything else in the event. –Efficiency: 2.18±0.06% (  ), 2.39±0.06% (e ) –N SM : 2.8±0.2 (  ), (7.3±1.4)x10 -5 (ev) hep-ex/0611045, submitted to Phys. Lett. B  e Br(  ) < 1.7x10 -6 @90%CL Br(e ) < 9.8x10 -7 253fb -1

19. 19 Future Prospect: B   Method? S.Robertson at CERN WS (May 2006) –Inclusive-recon method has high efficiency but poor S/N. –Hadronic tag will provide very clean and ambiguous signals, but very low efficiency. Luminosity (ab -1 ) Standard Deviation 3  at 1.3ab -1 5  at 3.7ab -1 Extrapolation from the present Belle analysis (inclusive-recon.) Extrapolation from the present Belle analysis. K.Ikado at BNM1 (Sep. 2006) ~50 events @ 5ab-1 ~500 events @ 50ab-1

20. 20 d l l Proceeds via box or penguin annihilation SM Branching fractions Flavor violating channel (B 0  e +  –, etc.) are forbidden in SM. B0l+l-B0l+l- d l l New Physics can enhance the branching fractions by orders of magnitude. ex.) loop-induced FCNC Higgs coupling A 0,H   h 0

21. 21 B 0  l + l - (e + e -,  +  -,e +  - ) B(B 0  e + e – ) < 6.1 × 10 -8 (90%CL) B(B 0   +  – ) < 8.3 × 10 -8 (90%CL) B(B 0  e +  – ) < 18 × 10 -8 (90%CL) e+e–e+e– +–+– e-+e-+ Signal regions Events observed Phys. Rev. Lett. 94, 221803 (2005) B(B 0  e + e – ) < 1.9 × 10 -7 (90%CL) B(B 0   +  – ) < 1.6 × 10 -7 (90%CL) B(B 0  e +  – ) < 1.7 × 10 -7 (90%CL) B(B 0 d      ) < 2.3×10 -8 (90% CL) Phys. Rev. D 68, 111101 (2003) 78 fb -1 780 pb -1 111 fb -1

22. 22 B 0  l + l - at B factories ? Pre-LHC era Present CDF limit;Br(B s   ) < 2.3x10 -8 (90%CL) is equivalent to Br(B d   ) < 1x10 -9. Interesting to see results with full Belle/BaBar data. LHC era Who knows the background at LHC ? B s   from  (5S) runs at Super-B ? –We can study background using the present  (5S) data! B d   is an unique opportunity at B factories. But, how clean are they ? See talk by E. Baracchini

23. 23 B 0   +  - (BaBar @ 210fb -1 ) Experimentally very very challenging (2-4 neutrinos in the final state ! ) High sensitive to NPBs   at hadron machines Analysis Reconstruct one B in a fully hadronic final state B  D (*) X =>280k events In the event remainder, look for two  decays (   l, ,  ) Kinematics of charged partilce momenta and residual energy are fed into a neutral network to separate signal and BG DataControl sample Nobs=263±19 Nexpect=281±48 Phys. Rev. Lett. 96, 241802 (2006) @90%C.L.

24. 24 Plots to be made… Region in tan  -m H for 5  evidence. –B   + B  D  –LHC direct search for the same 5  effect –Other measurements from B decays B  Xs  B  ll Combine B   and D (*)  to show –m H reach at tan  =30 as a function of L. –Significance at tan  =30 and m H =500GeV as a function of L. Precision for Br(  ), Br(  ) and their ratio as a function of L

25. 25 Need to study… Tagging strategy for neutrino modes –Inclusive recon. –Semileptonic tag. –Hadronic tag. Data quality in large L environment –Tagging efficiency –Beam background –Neutrino reconstruction BaBar’s B   search (324x10 6 BB) Tag by B  Dl X Tag B recon. eff.=0.7% Extra energy distribution in Belle’s B   search

26. 26 Backup

27. 27 New Physics in large tan  Leptonic decays (B  l, ll) are theoretically clean, free from hadronic uncertainty. In particular, they are good probes in large tan  region, together with other measurements;  m BS, B s  , B  X s  and also  decays (   ,    ). Ex.) G.Isidori & P.Paradisi, hep-ph/0605012 HH  A 0,H   h 0 Charged Higgs Neutral Higgs tan  M H (GeV) See talk by A.Weiler

28. 28 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

29. 29 Future Prospect: B  K Belle @ 250fb -1 (preliminary) Fully reconstructed tag (by modifying the PID criteria used in B   analysis). Consistent with BG expected Belle preliminary Signif.Lum (ab -1 ) 33 12 55 33 Need Super-B ! cf.) K.Ikado @ BNM2006