On new physics in $\Delta {\Gamma }_d$

Abstract

Motivated by the recent measurement of the dimuon asymmetry by the DØ collaboration, which could be interpreted as an enhanced decay rate difference in the neutral $B_d$-meson system, we investigate the possible size of new-physics contributions to $\Delta {\Gamma }_d$. In particular, we perform model-independent studies of non-standard effects associated to the dimension-six current-current operators $(\bar{d}p)({\bar{p}}^{\prime }b)$ with $p,p^{\prime }=u,c$ as well as $(\bar{d}b)(\bar{\tau }\tau )$. In both cases we find that for certain flavour or Lorentz structures of the operators sizable deviations of $\Delta {\Gamma }_d$ away from the Standard Model expectation cannot be excluded in a model-independent fashion.

Comments: 35 pages, 14 figures. Equation (5.10) corrected, references added. Conclusions remain unchanged