Radiative B decays at the BaBar Experiment Minliang Zhao (For the BaBar Collaboration) Massachusetts Institute of Technology Pheno 2008 Introduction b->(s,d) g are flavor changing neutral currents (FCNC) at the loop level
(For the BaBar Collaboration)
Massachusetts Institute of Technology
could be enhanced overthe Standard Model rate by newheavy particles.
Standard Model predicts <1%, an enhancement is a sign of new physics.
reveals the QCD effect inside the B meson, in light of the underlying 2-body decay.
Measured number of B (B-bkg subtracted signal yield) vs Eg
arXiv:0711.4889 Accepted in PRD
Moments of the photon spectrum:
Sensitive to heavy quark parameters
b quark mass: mb
Fermi motion: mp2
important input for |Vub|and |Vcb|
BaBar new result uses 383M BB samples accumulated through 2007, will reduce a large amount of the statistical error of BaBar '05 result;
are all statistics limited!
BaBar '08 result
BaBar '05 result
Sum of 16 exclusive modes (383M BB pairs)
50% of the B->Xsg Br
Hadronic mass (MXs) range: [0.6,2.8] GeV/c2
Good efficiency but huge background:
High energy photons that form good p0 and h are vetoed
A Boosted DecisionTree with 17 input variables
Primary interest: Branching fractions:
|Vtb/Vts| also obtained from the ratio of Bd and Bs mixing frequencies, but new physics affects them in different ways!
PRL 98, 151802 (2007) (347M BB pairs)
Used lepton tagging information to suppress the non-B decay background for the first time
4 dimensional (5 for wg) fit to extract the yields
Preliminary result presented at LP '07 (arXiv:0708.1652)
First evidence for non-resonant hadronic b->dg transitions!