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Abstract
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.
Highlights
Contributions proportional to the decay rate differences ∆Γd and ∆Γs
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 Bd-meson system, we investigate the possible size of new-physics contributions to ∆Γd
We perform model-independent studies of non-standard effects associated to the dimension-six current-current operators(pb) with p, p = u, c as well as(ττ ). In both cases we find that for certain flavour or Lorentz structures of the operators sizeable deviations of ∆Γd away from the Standard Model expectation cannot be excluded in a model-independent fashion
Summary
In the effective field theory approach the two types of operators are independent of one another Motivated by this observation we will study the case where new physics manifests itself to first approximation only in terms of ∆B = 1 interactions of the form b → f1f2d, which change Γd12 A generic new-physics model will give rise to different contributions to each non-leptonic decay channel and one must consider carefully the constraints on the (complex) coefficients Cipp individually. It is straightforward to calculate the ratio ∆Γd/∆ΓSdM using (2.3) While it is the coefficients ∆C1p,p2 (mb) which appear in low-energy observables such as (4.4), it is important to keep in mind that these are obtained from the matching coefficients at the new-physics scale ΛNP through renormalisation-group (RG) evolution. We postpone a more detailed discussion of these contributions to section 4.3
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