The forward-backward asymmetry and differences of partial moments in inclusive semileptonic B decays

TL;DR

This paper explores the use of forward-backward asymmetry and differences of partial moments in inclusive semileptonic B decays to improve the extraction of non-perturbative parameters and the CKM matrix element |V_{cb}|.

Contribution

It introduces the study of differences of partial moments and their potential to provide additional information beyond existing moments and asymmetries in B decay analyses.

Findings

Differences of partial moments can offer new insights into non-perturbative parameters.

Experimental cuts on four-momentum transfer preserve angular distribution shapes.

Impact of final-state radiation and lepton ID on asymmetry measurements is discussed.

Abstract

Global fits to moments of kinematic distributions measured in inclusive semileptonic $B\rightarrow X_c l \nu_l$ enable the determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ together with non-perturbative matrix elements of the heavy quark expansion. In current fits, only two distinct kinematic distributions are employed and, as a consequence, higher moments of these distributions need to be taken into account to extract the relevant non-perturbative matrix elements. The moments of a given distribution are highly correlated and experimental uncertainties increase for higher moments. To address these issues, Turczyk suggested the inclusion of the charged lepton forward-backward asymmetry $\mathcal{A}_{FB}$ in global fits, since it provides information on non-perturbative parameters beyond the commonly used moments. It is possible to construct differences of partial moments of kinematic distributions, which can provide additional information on the non-perturbative parameters beyond $\mathcal{A}_{FB}$ and are studied in this work for the first time. Further, experimental cuts on the four-momentum transfer square are studied and are shown to preserve the shape of the angular distribution, in contrast to commonly used cuts on the lepton energy. Finally, the impact of final-state radiation and experimental lepton identification requirements on measurements of $\mathcal{A}_{FB}$ and differences of partial moments are discussed.