B -> X_d gamma and constraints on new physics

TL;DR

This paper refines the Standard Model prediction for the B->X_d gamma decay rate, compares it with experimental data, and explores how new physics models like MSSM, two Higgs doublet, and right-handed currents are constrained by these measurements.

Contribution

It provides an updated SM prediction for B->X_d gamma decay and analyzes constraints on new physics models using recent measurements and reduced uncertainties.

Findings

Updated SM prediction for B->X_d gamma branching ratio.

Experimental measurement is consistent with the SM prediction.

Constraints on SUSY parameters and right-handed quark mixing are improved.

Abstract

We combine recent progress in measuring the branching ratio of the decay B->X_d gamma$ with the discovery that hadronic uncertainties in the CP-averaged branching ratio drop out to a large extent. Implications of these improvements on the size of possible new physics effects are investigated. We find the updated SM prediction for the CP-averaged branching ratio to be Br[B->X_d gamma]^SM_E_gamma>1.6 GeV = 1.54^+0.26-0.31*10^-5, which should be compared with the experimental value of Br[B->X_d gamma]^exp_E_gamma>1.6GeV = (1.41+-0.57) 10^-5. After performing a model independent analysis, we consider different new physics models: the MSSM with generic sources of flavor violation, the two Higgs doublet model of type III and a model with right-handed charged currents. It is found that the constraints on the SUSY parameters delta^d_13 have improved and that the absolute value of the right-handed quark mixing matrix element |V^R_td| must be smaller than 1.5*10^-4.