Toru Iijima Nagoya University

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

2. Contents • Introduction • Btn • BDtn, Xtn • Bln • Bll (ee, mm, tt) • BK(*)nn, nn n ’s in the final state (missing energy) Technical issues; - Tagging - Background

3. Evidence of Btn Hunting Rare Decays • High luminosity • Good detector (PID, vertex…) • Analysis techniques • qq background suppression • Fully reconstructed tag Observation of bdg FB asymmetry in BK* l+l- Direct CPV in B0K+p- Beginning of B->fK0 saga Observation of BK l+ l- CPV in B decay Success of B factories brought rare B decays in leptonic and neutrino modes on the stage !

4. Full Reconstruction Method • Fully reconstruct one of the B’s to tag • B production • B flavor/charge • B momentum Decays of interests BXu l n, BK n n BDtn, tn B e- (8GeV) e+(3.5GeV) Υ(4S) p full (0.1~0.3%) reconstruction BDp etc. B Single B meson beam in offline ! Powerful tools for B decays w/ neutrinos

5. Bt n (within the SM) • Proceed via W annihilation in the SM. • Branching fraction is given by • Provide information of fB|Vub| • |Vub| from BXu l n fB cf) Lattice (d~10%) • Br(Btn)/Dmd |Vub| / |Vtd| • Expected branching fraction HFAG [hep-ex/0603003] HPQCD [PRL95,212001(2005)]

6. H+/W+ t+ Bt 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. Br(SM) ~ 9 x 10-5

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

8. Results (Br & fB Extraction) • Measured branching fraction; • Product of B meson decay constant fB and CKM matrix element |Vub| • Using |Vub| = (4.39  0.33)×10-3 from HFAG 16% = 14%(exp.) + 8%(Vub) 15% fB = 216  22 MeV [HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ]

9. Constraints on Charged Higgs These regions are excluded. stat. syst. fB |Vub| fB from HPQCD |Vub| from HFAG Much stronger constraint than those from energy frontier exp’s.

10. If D|Vub| = 0 & DfB = 0 5ab-1 50ab-1 Future Prospect: Btn • Br(Bt n) measurement: More luminosity help to reduce both stat. and syst. errors. • Some of the syst. errors limited by statistics of the control sample. • |Vub| measurement: < 5% in future is an realistic goal. • fB from theory: ~10% now  5% ? My assumption DfB(LQCD) = 5% Preliminary

11. Cont’d Charged Higgs Mass Reach (95.5%CL exclusion @ tanb=30) Only exp. error (DVub=0%, DfB=0%) Preliminary DVub=2.5%, DfB=2.5% Mass Reach (GeV) DVub=5%, DfB=5% Luminsoity(ab-1)

12. Constraints at Super-B (cont.) DfB(LQCD) = 5% 5s potential Charged Higgs Mass Reach with 5s 5ab -1 rH 5s 50ab -1 rH 5s

13. Ratio may help ? • Deviation of Br. • Ratio to cancel out fB(G.Isidori&P.Paradisi, hep-ph/0605012) exp. fB |Vub| exp. BBd |Vub|

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

15. LoI • Signal selection efficiency 10.2% 2.6% 26.1% 13.3% • Expectation at 5 / 50 ab-1 for B+ decay 5s observation possible at 1ab-1 • Major background source • Missing charged and g tracks from BD(*) l n X (incl. slow p)

16. Similar to Btn Sensistivity to H± 50ab-1 DFF=5% 5ab-1 DFF=15%

17. Bmn (en) • Bmn is the next milestone decay. When do we see the signal ? Precision at Super-B ? • Precise Bt n/m n data provide lepton universality test. • Higgs effect itself is universal. RHtn = RHmn • Good probe to distinguish NP models. Br(tn)=1.6x10-4 Br(mn)=7.1x10-7 Br(en)=1.7x10-11

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% (mn), 2.39±0.06% (en) • NSM: 2.8±0.2 (mn), (7.3±1.4)x10-5 (ev) 253fb -1 mn en Br(en) < 9.8x10-7 Br(mn) < 1.7x10-6 @90%CL hep-ex/0611045, submitted to Phys. Lett. B

19. Future Prospect: Bmn Preliminary • Extrapolation from the present Belle analysis. K.Ikado at BNM1 (Sep. 2006) Extrapolation from the present Belle analysis (inclusive-recon.) Standard Deviation ~50 events @ 5ab-1 ~500 events @ 50ab-1 3s at 1.3ab-1 5s at 3.7ab-1 • 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)

20. l l l d d l A0,H0, h0 B0l+l- • Proceeds via box or penguin annihilation SM Branching fractions Flavor violating channel (B0e +m –, etc.) are forbidden in SM. • New Physics can enhance the branching fractions by orders of magnitude. ex.) loop-induced FCNC Higgs coupling

21. B0l+l- (e+e-,m+m-,e+m-) Signal regions Events observed m+m– e+e– • B(B0e+e–) < 6.1 × 10-8 (90%CL) • B(B0m+m–) < 8.3 × 10-8 (90%CL) • B(B0e+ m–) < 18 × 10-8 (90%CL) 111 fb-1 Phys. Rev. Lett. 94, 221803 (2005) e-m+ • B(B0e+e–) < 1.9 × 10-7 (90%CL) • B(B0m+m–) < 1.6 × 10-7 (90%CL) • B(B0e+ m–) < 1.7 × 10-7 (90%CL) 78 fb-1 Phys. Rev. D 68, 111101 (2003) B(B0dm+m-) < 2.3×10-8 (90% CL) 780 pb-1

22. B0l+l- at B factories ? Pre-LHC era • Present CDF limit;Br(Bsmm) < 2.3x10-8 (90%CL) is equivalent to Br(Bdmm) < 1x10-9. • Interesting to see results with full Belle/BaBar data. LHC era • Who knows the background at LHC ? • Bsmm from U(5S) runs at Super-B ? • We can study background using the present U(5S) data! • Bdtt is an unique opportunity at B factories. But, how clean are they ? See talk by E. Baracchini

23. B0t+ t- (BaBar @ 210fb-1) • Experimentally very very challenging (2-4 neutrinos in the final state ! ) • High sensitive to NP Bsmm 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 t decays (tlnn, pn, rn) • Kinematics of charged partilce momenta and residual energy are fed into a neutral network to separate signal and BG Data Control sample Nexpect=281±48 Nobs=263±19 @90%C.L. Phys. Rev. Lett. 96, 241802 (2006)

24. Plots to be made… • Region in tanb-mH for 5s evidence. • Bt n + BD t n • LHC direct search for the same 5s effect • Other measurements from B decays • BXsg • Bll • Combine Btn and D(*) tn to show • mH reach at tanb=30 as a function of L. • Significance at tanb=30 and mH=500GeV as a function of L. • Precision for Br(tn), Br(mn) and their ratio as a function of L

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tn search (324x106 BB) Tag by BDlnX Tag B recon. eff.=0.7% Extra energy distribution in Belle’s Btn search

26. Backup

27. H+ tanb t+ A0,H0, h0 MH(GeV) New Physics in large tanb • Leptonic decays (Bln, ll) are theoretically clean, free from hadronic uncertainty. • In particular, they are good probes in large tanb region, together with other measurements; DmBS, Bsmm, BXsg and also t decays (tmh, tmg). Ex.) G.Isidori & P.Paradisi, hep-ph/0605012 Charged Higgs Neutral Higgs See talk by A.Weiler

28. Form factor error Constraint to Charged Higgs • Once branching fraction is measured, we can constrain R. M.Tanaka, Z.Phys. C67 (1995) 321 r can be determined experimentally by B semiletonic decays at 5ab-1

29. Future Prospect: BKnn cf.) K.Ikado @ BNM2006 • Belle @ 250fb-1 (preliminary) Fully reconstructed tag (by modifying the PID criteria used in Btn analysis). Belle preliminary Consistent with BG expected Need Super-B !