New physics in $ΔΓ_d$

We analyze the possibility of having new physics effects in the decay rate difference, $ΔΓ_d$, of neutral $B_d$ mesons. Three different sources of enhancement are considered, CKM unitarity violations, beyond standard model effects in the tree-level dimension six operators $(\bar{d}p)(\bar{p}'b)$ with $p,p'=u,c$; and large enhancements of the almost unconstrained operators $(\bar{d}b)(\barττ)$. We find that deviations of several hundred per cent from the standard model prediction of $ΔΓ_d$ are not excluded by current experimental data.

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