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Tauonic, Radiative & Electroweak B Decays at Super-B

This workshop at CERN discusses the flavor physics potential of the Super-B factory, focusing on tauonic B decays and their sensitivity to new physics. Results and studies by Belle are also presented.

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Tauonic, Radiative & Electroweak B Decays at Super-B

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  1. Tauonic, Radiative & Electroweak B Decays at Super-B November 9, 2005 “Flavour in the era of the LHC” workshop @ CERN Toru Iijima Nagoya University Based on results and studies by Belle Letter of Intent for KEK Super B Factory ( KEK Report 2004-4 ) Physics at Super B Factory ( hep-ex/0406071 ) cf) SLAC-R-709, “The Discovery Potential of a Super B Factory” Proceedings of the 2003 SLAC Workshops

  2. Physics Targets at Super-B Search for new origin of flavor mixing and CPV. • CP violation • Precise CKM • Rare decays FCNC decays Tauonic decays • t decays Lepton flavor violation Figure by Dr.Hayasaka (Nagoya Univ.) This talk Using O(1010) B and t (~100 x now)

  3. H+/W+ t+ c b H+/W+ t+ nt Tauonic B Decays Charged Higgs contribution to B decays • Leptonic: Bt n • Semileptonic: BD t n Br(SM) ~ 9 x 10-5 Br(SM) ~ 8 x 10-3 Decay amplitude Tauonic decay is the most sensitive !

  4. 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~16%) • Br(Btn)/Dmd |Vub| / |Vtd| • Expected branching fraction

  5. 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

  6. Fully Reconstructed Sample • Belle (253fb-1): 275M BB  2.5x105 B0B0 + 4.2x105 B+B-

  7. Bt n Status (Belle LP05/EPS05) • NBB (produced) = 275M • NB+B- (full recon.) = 4.0 x 105 (purity 0.55) • Searched t decay modes • Cover 81% of the t decay • Event selection • Residual ECL energy • Total net charge etc. Obtained Eresidual See K.Ikado’s talk at EPS05 and hep-ex/0507034

  8. Cont’d • Overall • Signal efficiency = 33.7 % • Expected signal = 13.5 (SM) • Background est. = 31.4 • N observed = 39 Upper limit calculated by M.L. fit. tp-nmode has the best S/N ~1.

  9. Prospect • Will soon reach the SM. • 3s evidence at ~700 fb-1 • 5s discovery at ~2 ab-1 • Expected precision at Super-B • 13% at 5 ab-1 • 7% at 50 ab-1 • Search with D(*) l n tag will help. (BaBar 232M BB, hep-ex/0507069) • Tag eff ~ 1.75 x 10-3 • Signal selection eff. ~31% • Similar S/N to Belle

  10. rH tanb/mH Impact to Charged Higgs • effects to branching fraction 90%CL excluded region at present 95% CL excluded region at 5ab-1 (if Bobs = BSM)

  11. BD t n (MC studies) • Use fully reconstructed samples. • T decay modes • Analysis cuts; • Reject events w/ p, KL • Reject D(*)t n contamination • No remaining charged or p0 tracks • ECL residual energy • Angle between two n’s • Missing mass Signal BG

  12. Cont’d • 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)

  13. 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

  14. Cont’d Constraint From bsg D(Form-factor) ~5% D(Form-factor) ~15% Present limit From Bt n

  15. bsg/sl+l- • Possible to search for NP in theoretically clean way. • Many observables; • Branching fractions • Mixing indcued CPV • Direct CPV • Forward-backward asym. • Ratio of exclusive modes Effective Hamiltonian for bs |C7| by BXsg, Sign of C7, C9, C10 by BXsll M(H+) > 350 GeV already in TYPE II 2HDM

  16. Measurement of B(BXsl+l-) M. Iwasaki et al. submitted to PRD, hep-ex/0503044 • Semi-inclusive technique • Xs is reconstructed from K+ or Ks + 0-4p (at most one p0 is allowed) • MXs < 2.0 GeV • Electron or muon pair • Mll>0.2GeV • Charmonium veto 140/fb data Wrong flavor MXs q2 Theoretical prediction by Ali et al.

  17. C7 = -C7SM C7SM Constraints on Ci from B(BXsl+l-) P.Gambino, U.Haisch and M.Misiak PRL 94 061803 (2005) • Clean prediction for B(BXsll) with 1<q2<6GeV2is available. • Combine Belle and Babar results • Sign of C7 flipped case with SM C9 and C10 value is unlikely. C10NP C10NP Donut : 90% CL allowed region SM C9NP

  18. l- l+ B B q q K* K* l- l+ BK*ll FB Asymmetry • Good electroweak probe for bs loop. • q2 distribution has different pattern depending on sign(C7). Forward Backward q0(the point w/ AFB=0) is sensitive for New Physics SM; q02=(4.2±0.6)GeV2

  19. A10/A7 A9/A7 A10/A7 ＳＭ A9/A7 AFB: Belle Summer ‘05 • 357fb-1 (386M BB) • N(K*ll)=114+-14 (purity 44%) • Unbinned M.L. fit to dG2/dsd(cosq) • 8 event categories • Signal + 3 cross-feed + 4 bkg. • Ali et al’s form factor • Fix |A7| to SM • Float A9/A7 and A10/A7 • Results; w/negative A7 (SM like) w/positive A7 Sign of A9A10 is negative ! See Hep-ex/0508009 & A.Ishikawa’s talk at EPS05

  20. Prospect at Super-B 1000 pseudo experiments w/ SM input values Expected precision @ 5ab-1 dC9 ~ 11% dC10 ~14% d q02/q02 ~11% 5% at 50ab-1

  21. Radiative Decays • Inclusive Br(bsg) |C7|, SF for |Vub| • BK*g isospin asymmetry (D+-) sign of C7 • Mixing induced CPV • Direct CPV in BXsg • BXdg Summary by M.Nakao 1st Super-B workshop at Hawaii

  22. mb C7 ms ms mb p+ p- Ks trajectory B vertex IP profile g g BXsg CP Asymmetry • Sensitive to NP. • Theoretically clean. • Standard Model “~Zero”. • Gamma is polarized, and the final state is almost flavor specific. • Helicity flip of g suppressed by ~ms/mb • Time dependent CPV requires vertex reconstruction with Ks p+p- Vertex recon. Eff. 51% (SVD2) 40% (SVD1) Possible at e+e- B-factory

  23. B0KSp0g tCPV: Belle Summer ‘05 • 386MBB • M(Ksp0) < 1.8GeV/c2 • NP effect is independent of the resonance structure. • Two M(Ksp0) regions(MR1:0.8-1.0GeV/c2 / MR2: <1.8GeV/c2) • 70+-11 (45+-11) events in MR1(2). • Atwood, Gershon, Hazumi, Soni, • PRD71, 076003 (2005) Result S= +0.08 ±0.41 ±0.10 A= +0.12±0.27±0.10 Good tag (0.5<r<1.0) Present Belle (stat./syst.) 5ab-1 50ab-1 Acpmix(BK*g, K*Ksp0) 0.41 / 0.10 0.14 0.04 Acpdir(BXsg) 0.051 / 0.038 0.011 0.005

  24. Acp(BXsg) vs SUSY models 5ab-1 50ab-1 Mixing CPV Direct CPV U(2) tanb=30 mSUGURA tanb=30 U(2) tanb=30 mSUGURA tanb=30 Acpdir Acpmix SU(5)+nR tanb=30 non-degenerate SU(5)+nR tanb=30 degenerate SU(5)+nR tanb=30 non-degenerate SU(5)+nR tanb=30 degenerate T. Goto, Y.Okada, Y.Shimizu,T.Shindou, M.Tanaka hep-ph/0306093, also in SuperKEKB LoI

  25. Summary • Tauonic, Radiative and Electroweak B decays are of great importance to probe new physics. • We are starting to measure Btn, Dtn, AFB(K*ll), ACP(Kp0g) etc. at the current B factories. Hot topics in the coming years ! • For precise measurements, we need Super-B ! Expected precision (5ab-150ab-1); • Br(tv): 13%7% • Br(Dtn): 7.9%2.5% • q02 of AFB(K*ll): 11%5% • ACP(Kp0g) tCPV: 0.140.04

  26. Backup Slides

  27. CPV in bs and SUSY Scenario • Different SUSY breaking scenario can be distinguished in Acpmix(fKs) - Acpmix(K*0g) correlation. Expected precision at 5ab-1 Correlation of other ovservables are also useful. Acpdir(Xsg), AFB(Xsll), Br(tmg), CKM

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