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

Motivated by the recent measurement of the dimuon asymmetry by the D{\O} 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 $\mathrm{\Delta }{\mathrm{\Gamma }}_d$. In particular, we perform model-independent studies of non-standard effects associated to the dimension-six current-current operators $(\bar{d} p)(\bar p^{\hspace{0.25mm}\prime} b)$with$p,p^\prime= u,c$aswellas$(\bar{d}b) (\bar\tau\tau)$. In both cases we find that for certain flavour or Lorentz structures of the operators sizable deviations of $\mathrm{\Delta }{\mathrm{\Gamma }}_d$ away from the Standard Model expectation cannot be excluded in a model-independent fashion.