Prospects and Issues for Joint B-Factory Analysis of B → sll Final States

1. Prospects and Issues for Joint B-Factory Analysis of B→sll Final States Kevin Flood University of Wisconsin

2. Benefits of Joint B→sll Analyses • B→sl+l- are relatively rare B decays • Inclusive BF ~5x10-6 ; K*ll BF ~ 1x10-6; Kll BF ~ 0.5x10-6 • Many clean observables, but best non-SM sensitivity requires precision measurements as a function of di-lepton mass [q2≡m(ll)2] • Joint data analysis provides both qualitative and quantitative benefits • Qualitative benefits require analysis of combined datasets using simultaneous fits to physical observable(s) • Finer q2 binning for all analyses allows resolution of detailed structure of observables as function of q2 • New angular observables requiring relatively large signal yields possible • Angular analyses become possible for the higher K* resonances • BFs similar to K*(892) but much broader mass distributions • Clean theory predictions for angular analyses • Quantitative benefits from increase in raw statistics, event-by-event accounting for correlations in simultaneous fits

3. How Far to Go? • Fundamental question is degree of dataset co-mingling • No shared data: Purely statistical combination of disjoint analysis results reported in agreed-upon format (q2 bins, hadronic system mass cuts, etc.) a la e.g. Heavy Flavor Averaging Group • Shared fit methodology: Each collaboration keeps data separate but adopts common ntuple data structure and fitting strategies • Each analyst group produces, validates and analyses their own data • At the end of the process do a simultaneous fit to the disjoint datasets using the pdfs, normalizations, etc. from the individual collaboration fits along with a shared physical observable(s) • Shared data and fits: Common ntuple data structure, fit strategies and methodologies driven by statistical optimization assuming a completely co-mingled dataset • Each group produces PDFs, normalizations, etc. reflecting details of reconstruction with their detector, but many more shared components in fits such as random combinatoric backgrounds, signal mES/mBC, etc. in addition to shared physical observable

4. Prerequisites for Joint Analysis • Optimize joint K*ll analysis to demonstrate benefits • Pure toy studies assuming 1.3/ab dataset • Embedded MC signal events + toy random combinatoric bkgds • Observables beyond AFB, FL, Df • How many q2 bins? boundaries? • Get the “easy” things correct in joint analysis • J/psi, psi(2S) branching fractions, K* longitudinal polarization • Common control samples • K+, pi+, pion-as-muon misid efficiencies from D*+ -> D0(Kpi) pi+ • Lepton PID efficiencies from QED samples • If results all OK, J/psi then provides • Signal mES/mBC PDFs • Calibration of efficiency/bias of multivariate event selection

5. Extrapolation from Recent K*ll FL, AFB • Assume final Babar+Belle dataset yields ~2x current Belle • Best SM exclusion: 1 q2 bin for most negative-going part of SM AFB • 1.0<q2<3.0, SM AFB ~ -0.13, 60-80 signal, exclude SM at >99% CL • Best limit on AFB zero: two q2 bins either side of q2 ~ 4.3, below J/psi • 30-40 signal per bin, use toys to set CL on any (or any particular) AFB zero • Adjust upper bound on q2 bin adjacent to J/psi low edge • J/psi backgrounds 7.84 < q2 not well modeled in Babar MC Babar Belle

6. Two Flavors of Inclusive Analysis • Sum of exclusive modes (previously done by Belle and Babar using relatively small datasets) • 1.3/ab signal yield ~ 1000 each for ee and mumu • Measurement of partial rates and helicities in q2 bins can fully characterize Wilson coeffs(PRD 75, 034016 [2007]) • Need agreement on maximum Xs mass and multiplicity • Fully inclusive analysis of lepton pairs with hadronic and semileptonic B tags • Is existing Breco info similar between experiments? • Published similar Breco analyses (B->tau nu, K(*)nunubar) • 1.3/ab signal yield ~ 50 for ~2% tag efficiency • Background models available directly from data • No model dependence in extracting inclusive rates

7. Additional Opportunities • Higher K* resonances? • Based on K*gamma, signal yields should be same order of magnitude as K*(892)l+l- • Widths 100-300 MeV, compared to K*(892) width ~ 50 MeV • If enough signal events can do angular analysis • Clean theory predictions for K2*(1430), K1(1270)/K1(1400) • Lepton flavor violation: Xs (e, e , t) final states? • Maybe even K(*) ... • Exclusive (p+,p0) l+l-: SM N(signal) ~ 100 events • |Vtd| / |Vts| statistical error competitive with current (d,s)g • Good sensitivity to non-SM contributions in rate and d/s ratio • Photon polarization in TDCPV b->sg exclusive final states • Toy studies of 1.3/ab sensitivity interesting • TDCPV joint analyses likely much more difficult