  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 $\Delta \Gamma_d$. In particular, we perform
model-independent studies of non-standard effects associated to the
dimension-six current-current operators $(\bar{d} p)(\bar
p^{\hspace{0.25mm}\prime} b)$ 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.
