1. for the BaBar and Belle Collaborations CKM 2008: 5 th International Workshop on the CKM Unitarity Triangle Rome, Italy, September 9-13, 2008 Bruce A. Schumm Santa Cruz Institute for Particle Physics University of California, Santa Cruz BaBar

2. CKM 2008: V td /V ts from Radiative Decays2 Bruce Schumm Motivation B →  (ρ,ω)  (“Standard” Approach) B  →  X d (“Semi-Inclusive” Approach) Status of |V td /V ts | and Conclusions

3. BaBar CKM 2008: V td /V ts from Radiative Decays3 Bruce Schumm (d) V t(s,d) Note: In both cases, hadronic uncertainties minimized by comparing to corresponding V ts process (B s mixing, b  s  )  Observable is | V td / V ts | B Mixing Radiative Penguins Two independent diagrams provide sensitivity to CKM parameter V td

4. BaBar CKM 2008: V td /V ts from Radiative Decays4 Bruce Schumm ICHEP ’08 B Mixing Results [Farrington(CDF), Moulik(D0), averaged by DeLodovico(BaBar)]: How do penguins fit into the picture? Mixing: x d =  m B /  B ~ 1   m B ~  B Penguins: Br(b  d  ) ~ 10 -5   d  ~ 10 -5  B “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  X d +  (and its charge conjugate) than in the corresponding CKM-allowed vertices b  s  and b  sg” Furthermore (Ali, Asatrian, Greub, Phys. Lett B 429, 87): With |V td /V ts | precisely constrained by mixing, b  d  is a compelling testbed for new physics. SM effects suppressed by 10 -5 relative to mixing

5. BaBar CKM 2008: V td /V ts from Radiative Decays5 Bruce Schumm “Traditional” Approach: measure exclusive rate Br(B   (  )  ); normalize with Br(B  K *  ) (and  ) 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. Annihilation Diagram

6. BaBar CKM 2008: V td /V ts from Radiative Decays6 Bruce Schumm Belle: New result this Spring 351 fb -1 (2006)  598 fb -1 (April 2008) BaBar: New (preliminary) 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  [particle ID]  B → (      [veto if  found such that M  ~ M ( ,  ) ]

7. BaBar CKM 2008: V td /V ts from Radiative Decays7 Bruce Schumm Remaining separation achieved by two-dimensional fit to the largely independent kinematic variables “Energy-substituted mass”; since E beam ~ M B, largely a measurement of momentum balance * In e + e - CMS frame E B = E beam for properly reconstructed candidate; total energy measurement Example: BaBar B 0   0   “self-calibrating” continuum background subtraction  efficiencies (~5-15%) estimated with control samples Signal Continuum b  s  Feedthrough PRELIMINARY

8. BaBar CKM 2008: V td /V ts from Radiative Decays8 Bruce Schumm ModeBelle ’06 (x10 -7 )Belle ’08 (x10 -7 ) + +  0 0      Increase sample from 351 fb -1 to 598 fb -1  Continuum: Fischer Discriminant with Fox-Wolfram moments, B flight information, vertex information  Include photons from endcap calorimeter Ji Lin, ICHEP ‘08

9. BaBar CKM 2008: V td /V ts from Radiative Decays9 Bruce Schumm  Increase sample from 316 fb -1 to 423 fb -1 (final data set)  Strategy: Focus on unconfirmed B   mode  Continuum suppression: “Bagged Decision Tree” with 60 input event variables  Relatively good signal-to-noise ++

10. BaBar CKM 2008: V td /V ts from Radiative Decays10 Bruce Schumm ModeBaBar ’07 (x10 -7 )BaBar ’08 (x10 -7 ) + +  0 0     00  PRELIMINARY

11. BaBar CKM 2008: V td /V ts from Radiative Decays11 Bruce Schumm Assuming SU 3 (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 |V td /V ts | from

12. BaBar CKM 2008: V td /V ts from Radiative Decays12 Bruce Schumm BELLE: assuming the world-average Combining, for exclusive radiative decay overall: BaBar: yielding PRELIMINARY

13. BaBar CKM 2008: V td /V ts from Radiative Decays13 Bruce Schumm |V td /V ts | 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. M Xd > 1.8 GeV/c 2 ) “New” Approach (BaBar): Reconstruct seven exclusive final states X d  in range 0.6 GeV/c 2 < M Xd < 1.8 GeV/c 2

14. BaBar CKM 2008: V td /V ts from Radiative Decays14 Bruce Schumm ( , ,K * ) 1.0 < M had < 1.81.8 < M had XSXS XdXd MEASURED UNMEASURED  and X d analyses X d analysis only M had (M Xd ) #  0 # bodies

15. BaBar CKM 2008: V td /V ts from Radiative Decays15 Bruce Schumm Fit in high-mass X d  region (first time measured): Yields and partial branching fractions: High-mass b  X d  Continuum background X s , MisID background B A B AR PRELIMINARY

16. BaBar CKM 2008: V td /V ts from Radiative Decays16 Bruce Schumm  Dominant systematic error for 1.0 < M X < 1.8 GeV/c 2  Most difficult for B  X d  (not constrained by data)  Can improve with statistics (internal constraints) Errors: Statistical  Experimental Systematic Try several models: M X 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 Primary experimental result B A B AR PRELIMINARY

17. BaBar CKM 2008: V td /V ts from Radiative Decays17 Bruce Schumm arXiv:0807.4975 [hep-ex]; submitted to PRL Precise (~1%) expression for |Vtd/Vts| [Ali, Asatrian, Greub] is based on ratio of full widths  (b  d  )/  (b  s  ) Measured region 0.6 < M X < 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 m s,m d << 1.8 GeV/c 2 ?) This remains a bit of a caveat… Ali Asatrian Greub Expt. Theory B A B AR PRELIMINARY

18. BaBar CKM 2008: V td /V ts from Radiative Decays18 Bruce Schumm No evidence for non-Standard Model contribution to the decay width. * * PRELIMINARY *

19. BaBar CKM 2008: V td /V ts from Radiative Decays19 Bruce Schumm  Radiative measurements of |V td /V ts | are becoming precise: | V td /V ts | 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?