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Miami 2008: b -> s(d) γ Transition Rates - Effective Neutral Currents and Radiative Penguins

This paper discusses the effective neutral currents and radiative penguins in the b -> s(d) γ transition rates, including SUSY parameter space implications and various approaches. It also explores the impact of b -> s(d) γ on the tanβ-mA plane and presents measurements from the BaBar and Belle collaborations.

jamesross
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Miami 2008: b -> s(d) γ Transition Rates - Effective Neutral Currents and Radiative Penguins

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  1. Miami 2008 Topical Conference on Elementary Physics, Astrophysics, and Cosmology Fort Lauderdale, FL, Dec 16-21, 2008 BaBar B Factory Measurements of the b s(d)  “Radiative Penguin” Transition Rates for the BaBar and Belle Collaborations Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz

  2. Outline • Effective Neutral Currents: General Motivation • b  s Penguins • SUSY parameter space implications • b  s “Inclusive” approach • B  XS “Semi-Inclusive” approach • b  d Penguins and |Vtd/Vts| • Motivation • B →(ρ,ω)g “Exclusive” approach • B→Xd “Semi-Inclusive” approach • Status of |Vtd/Vts| • Conclusions Miami 2008: b  s(d) Transition Rates

  3. Effective Neutral Currents and Radiative Penguins The SM b  s(d)  transition is high order (two weak plus one EM vertex) … Vtb Vt(s,d) so new physics can enter at leading order: + photon off any charged leg Although rare (~ 5x10-4 for s and ~10-5 for d), the isolated high-energy photon is a powerful signature. Miami 2008: b  s(d) Transition Rates

  4. Outline • Effective Neutral Currents: General Motivation • b  s • SUSY parameter space implications • Inclusive approach • Other approaches • b  d and |Vtd/Vts| • Motivation • B →(ρ,ω)g (“Standard” Approach) • B→Xd (“Semi-Inclusive” Approach) • Status of |Vtd/Vts| • Conclusions Miami 2008: b  s(d) Transition Rates

  5. Direct searches (LEP) B  s and SUSY Parameter Space B  s constraints MSSM Constraints bs has a significant impact on the tan-mA plane… Miami 2008: b  s(d) Transition Rates

  6. B  s and SUSY Parameter Space (cont’d) … on some of our favorite scenarios … Fate of “Snowmass” MSSM study points Miami 2008: b  s(d) Transition Rates

  7. B  s and SUSY Parameter Space (cont’d) … and just in general. C.F. Berger, J.S. Gainer, J.L. Hewett, T.G. Rizzo, “Supersymmetry Without Prejudice”, arXiv:0812.0980v1 [hep-ph] Explore 107 points over 19-dimensional parameter space of CP-conserving MSSM b  s most effective constraint (72% of models surviving prior constraints are eliminated; better than direct searches for SUSY partners) Miami 2008: b  s(d) Transition Rates

  8. The e+e- Cross Section in the Upsilon Region The (4S) resonance is the lightest resonance that decays into “open Beauty” ( or ) Off-Peak Data (~10% of Sample) On-Peak Data (4S) resonance is ~1 nb at peak, competing with a “continuum” background of ~3 nb Miami 2008: b  s(d) Transition Rates

  9. B Factory Data Sets 440 fb-1 700 fb-1 Miami 2008: b  s(d) Transition Rates

  10. qq + ττ BB XSγ Inclusive Measurement of b  s: Introduction Most exacting approach (“Inclusive”) is aggressive: Use only high-energy  as signature Suppress continuum with event shapes, requirement of a high-energy lepton. Estimate remaining contribution by scaling off-peak data. Challenge: background from 0()   decays (plus some fakes) in B decays Miami 2008: b  s(d) Transition Rates

  11. Inclusive Measurement of b  s: Practicalities • To remove 0() background: • Veto event if you find the 2nd photon (~45% efficient for 0() fakes) • Estimate and subtract out cases for which 2nd photon is missed (S/B ~ 1/1) • Requires knowledge of second photon efficiency to < 1%; measure using, e.g., 0s from e+e-  ;   +-0 • Becoming limiting experimental uncertainty No s signal here; provides test of 0 subtraction BELLE: (3.370.43)x10-4arXiv:0804.1580 605 fb-1 BaBar: (3.920.56)x10-4PRL97,171803 82 fb-1 NOTE: Measurements scaled to Ecms = 1.6 GeV Miami 2008: b  s(d) Transition Rates

  12. b  s  Via a Sum of Exclusive Final States (BaBar) Reconstruct a total of 38 exclusive b  s final states that comprise about 55% of the total width Fit to reconstructed mass of exclusive final state to determine signal yield This “Semi-Inclusive” approaches employs a fit to the mass distribution, for which backgrounds tend to be self-calibrating… Miami 2008: b  s(d) Transition Rates

  13. BaBar Semi-Inclusive Analysis (continued) But need to rely on models to correct for the 45% of states that are not measured (depends on mass M(Xs) that photon recoils against). • RESULT • BF(B  s) = (3.49  0.57)x10-4 • PRD72:052004 • 82 fb-1 analyzed is less than 10% of world sample • Has systematics independent of those of inclusive approach Mass Recoiling Against  Miami 2008: b  s(d) Transition Rates

  14. Inclusive Semi-Inclusive Inclusive Inclusive Inclusive Summary of Measurements of the b  s Rate Experimental accuracy commensurate with theoretical control, but work continue on both ends A. Limosani, Melbourne Most of BaBar data set still unanalyzed Miami 2008: b  s(d) Transition Rates

  15. Outline • Effective Neutral Currents: General Motivation • b  s • SUSY parameter space implications • Inclusive approach • Other approaches • b  d and |Vtd/Vts| • Motivation • B →(ρ,ω)g (“Standard” Approach) • B→Xd (“Semi-Inclusive” Approach) • Status of |Vtd/Vts| • Conclusions Miami 2008: b  s(d) Transition Rates

  16. (d) (d) (d) (d) Vt(s,d) (d) (d) Measuring |Vtd/Vts| Two independent diagrams provide sensitivity to CKM parameter Vtd B Mixing Note: In both cases, hadronic uncertainties minimized by comparing to corresponding Vts process (Bs mixing, b  s)  Observable is | Vtd / Vts | Radiative Penguins Miami 2008: b  s(d) Transition Rates

  17. |Vtd/Vts| from Penguins: Motivation ICHEP ’08 B Mixing Results [Farrington(CDF), Moulik(D0), averaged by DeLodovico(BaBar)]: How do penguins fit into the picture? SM effects suppressed by 10-5 relative to mixing Mixing: xd = mB/B ~ 1  mB ~ B Penguins: Br(bd) ~ 10-5 d~ 10-5B Furthermore (Ali, Asatrian, Greub, Phys. Lett B 429, 87): “These [b  d] vertices are CKM-suppressed in the standard model, but new physics contributions may not follow the CKM pattern in flavor-changing-neutral-current transitions and hence new physics effects may become more easily discernible in B  Xd +  (and its charge conjugate) than in the corresponding CKM-allowed vertices b  s and b  sg” With |Vtd/Vts| precisely constrained by mixing, b  d is a compelling testbed for new physics. Miami 2008: b  s(d) Transition Rates

  18. (and ) Exclusive Approach: B  ()  “Traditional” Approach: measure exclusive rate Br(B  () ); normalize with Br(B  K* ) Annihilation Diagram Values of 2 and R are state (+,0,) dependent and are available from Ali, Parkhomenko, arXiv:hep-ph/0610149 Ball, Zwicky, J. High. Energy Phys. 0604, 046 (2006); Ball, Jones, Zwicky, Phys. Rev. D 75 054004 (2007) at approximately 8% overall accuracy. Miami 2008: b  s(d) Transition Rates

  19. Measurement of B(B  ()  ) Belle: New result this Spring 351 fb-1 (2006)  598 fb-1 (April 2008) BaBar: New result this Summer 316 fb-1 (April 2007)  423 fb-1 (July 2008) • Challenge: BRs are small (<10-6); backgrounds are high • continuum Neural Net with event shape, B tagging information, … • B → K*; K* K Require excellent particle ID • B → (Veto if  found such that M~ M(,) Miami 2008: b  s(d) Transition Rates

  20. Measurement of B(B  () ) (continued) Remaining separation achieved by two-dimensional fit to the largely independent kinematic variables “Energy-substituted mass”; since Ebeam ~ MB, largely a measurement of momentum balance EB = Ebeam for properly reconstructed candidate; total energy measurement *In e+e- CMS frame Example: BaBar B0 0  • “self-calibrating” continuum background subtraction • efficiencies (~5-15%) estimated with control samples Continuum Signal bs Feedthrough Miami 2008: b  s(d) Transition Rates

  21. Recent Updates of B  ()  Phys.Rev.Lett.101:111801,2008, Erratum-ibid.101:129904,2008 BELLE:  598 fb-1 BaBar:  423 fb-1 Phys.Rev.D78:112001,2008 Miami 2008: b  s(d) Transition Rates

  22. |Vtd/Vts| from Exclusive (,) Decays Assuming startic quark model, SU(3)F symmetry, can combine to get “isospin-averaged” BF, and then |Vtd/Vts|: BELLE: yielding BaBar: yielding assuming the world-average Combining, for exclusive radiative decay overall: Miami 2008: b  s(d) Transition Rates

  23. Semi-Inclusive Approach: B  Xd  (Preliminary) “New” Approach (BaBar): Reconstruct seven exclusive final states Xd in range 0.6 GeV/c2 < MXd < 1.8 GeV/c2 • |Vtd/Vts|2 related to (bd)/(bs) with ~1% theoretical uncertainty [Ali, Asatrian, Greub, Phys. Lett. B 429, 87 (1998)] • However, must correct for unmeasured regions: • Higher-multiplicity final states • Higher-mass hadronic component (i.e. MXd > 1.8 GeV/c2) Miami 2008: b  s(d) Transition Rates

  24. # bodies # 0 Measured Regions for B  Xd(s)  UNMEASURED XS MEASURED (,,K*) 1.0 < Mhad < 1.8 1.8 < Mhad Xd Xd analysis only  and Xd analyses Mhad (MXd) Miami 2008: b  s(d) Transition Rates

  25. Continuum background Xs, MisID background B  X(s,d)  Partial Branching Fraction Results Fit in high-mass Xd region (first time measured): BABAR BABAR Yields and partial branching fractions: PRELIMINARY High-mass b  Xd  Miami 2008: b  s(d) Transition Rates

  26. Errors: Statistical  Experimental Systematic Correction for Missing Modes • Dominant systematic error for 1.0 < MX < 1.8 GeV/c2 • Most difficult for B  Xd  (not constrained by data) • Can improve with statistics (internal constraints) • Try several models: • MX given by “KN Model” Kagan & Neubert, Phys. Rev. D 58, 094012 (1998), with phase-space fragmentation • As above, but with 50% replaced by mix of resonances • Fix to measured b  s fragmentation BABAR Primary experimental result PRELIMINARY Miami 2008: b  s(d) Transition Rates

  27. Ratio of Total Widths and |Vtd/Vts| Precise (~1%) expression for |Vtd/Vts|[Ali, Asatrian, Greub] is based on ratio of full widths(bd)/(bs) Measured region 0.6 < MX < 1.8 is ~50% of width Extrapolate to full mass region via “KN Model”; KN calculation suggests negligible difference and uncertainty in extrapolation of the ratio (because ms,md << 1.8 GeV/c2?) BABAR BABAR PRELIMINARY Ali Asatrian Greub PRELIMINARY Expt. Theory arXiv:0807.4975 [hep-ex]; submitted to PRL Miami 2008: b  s(d) Transition Rates

  28. * PRELIMINARY Global Status of |Vtd/Vts| * No evidence for non-Standard Model contribution to the decay width. Miami 2008: b  s(d) Transition Rates

  29. Radiative measurements of |Vtd/Vts| are becoming precise: | Vtd/Vts|rad = 0.203  0.020 • Semi-inclusive approach works, and is independent of exclusive approach, with small theoretical uncertainty • Agreement with SM (as constrained by B mixing) is good In principle, the severe SM suppression of this radiative process (x10-6 of B mixing) should make it very sensitive to new physics contributions. Have we fully thought through the meaning of this constraint? Concluding Remarks • B  s continues to be leading constraint on MSSM parameter space • More data exists (~80% of BaBar sample) to improve measurement, but “inclusive” approach starting to be limited by difficult systematics • “Semi-inclusive” approach has systematics independent of inclusive approach; very little of existing sample has been analyzed in this way. Miami 2008: b  s(d) Transition Rates

  30. Backup Slides Miami 2008: b  s(d) Transition Rates

  31. Isopsin-Averaged Branching Fractions Assuming SU3(F) symmetry [B(B0) ~ B(B)] and (approximately true by static quark model) we can write from which it follows  Can combine +, 0,  results to derive |Vtd/Vts| from Miami 2008: b  s(d) Transition Rates

  32. Miami 2008: b  s(d) Transition Rates

  33. Miami 2008: b  s(d) Transition Rates

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