Untagged (B)over-bar→Xs+dγ CP asymmetry as a probe for new physics

The direct CP asymmetry in the untagged inclusive channel (B) over bar --> X(s+d)gamma provides a strict test of the standard model. It has been shown beyond the partonic level that this asymmetry is negligibly small thanks to U-spin relations and to the unitarity of the CKM matrix. In the present paper we investigate this relation beyond the SM; in particular, we analyse to which extent deviations from this prediction are possible in supersymmetric scenarios. We analyse the minimal flavour violation scenario, including tan beta-enhanced terms and using the complete two-loop renormalization group running. Our analysis fully takes into account also the EDM constraints on the supersymmetric phases. We also investigate possible correlations between the tagged and the untagged CP asymmetries and the indirect sensitivity of the latter to the (B) over bar --> X(d)gamma CP asymmetry. Furthermore, we derive general model-independent formulae for the branching ratios and CP asymmetries for the inclusive (B) over bar --> X(s)gamma and (B) over bar --> X(s)gamma modes, and update the corresponding SM predictions. We obtain for a photon energy cut-off E-0 = 1.6 GeV: B[(B) over bar --> X(s)gamma] = (3.61(-0.40)(0.24)\(mc/mb) +/- 0.02(CKM) +/- 0.24(param.) +/- 0.14(scale)) x 10(-4), A(CP)[(B) over bar --> X(s)gamma] = (0.42(-0.08)(+0.08)\(mc/mb) +/- 0.03(CKM-0.08)(0.15)\(scale))%. (C) 2004 Elsevier B.V. All rights reserved.