Constraining weak annihilation using semileptonic D decays

TL;DR

This paper uses recent semileptonic D_s decay measurements to better constrain weak annihilation effects in D and B meson decays, reducing uncertainties in key CKM matrix element extractions.

Contribution

It provides a new analysis of inclusive semileptonic D_{(s)} decays, showing WA effects are smaller than previously assumed and refining the understanding of their role in CKM measurements.

Findings

Weak annihilation is smaller than commonly assumed.

No dominant octet contribution to weak annihilation.

Results reduce uncertainty in |Vub| extraction from B decays.

Abstract

The recently measured semileptonic D_s decay rate can be used to constrain weak annihilation (WA) effects in semileptonic D and B decays. We revisit the theoretical predictions for inclusive semileptonic D_{(s)} decays using a variety of quark mass schemes. The most reliable results are obtained if the fits to B decay distributions are used to eliminate the charm quark mass dependence, without using any specific charm mass scheme. Our fit to the available data shows that WA is smaller than commonly assumed. There is no indication that the WA octet contribution (which is better constrained than the singlet contribution) dominates. The results constrain an important source of uncertainty in the extraction of |Vub| from inclusive semileptonic B decays.