Complementary Observables for the Determination of |Vub| in Inclusive Semileptonic B Decays

TL;DR

This paper introduces a novel method to determine |Vub| in inclusive semileptonic B decays by constraining shape function parameters directly from decay data, reducing uncertainties in the measurement.

Contribution

The paper proposes a new approach that uses combined measurements of lepton and neutrino momenta to better constrain shape function parameters, improving |Vub| accuracy.

Findings

Reduced uncertainties in |Vub| measurement.

Effective discrimination between b->ulnu and background.

Enhanced shape function parameter constraints.

Abstract

The determination of |Vub| from inclusive semileptonic B decays is limited by uncertainties in modelling the decay distributions in b->ulnu transitions. The largest uncertainties arise from the limited knowledge of the appropriate b quark mass and Fermi momentum to use in the parameterization of the shape function. This paper presents a new method in which these shape function parameters are constrained by the same data used to measure |Vub|. The method requires measurements of the momenta of both the charged lepton and the neutrino in semileptonic B decays. From these quantities two complementary observables can be constructed, one for discriminating between b->ulnu transitions and background and the other for constraining the shape function. Using this technique the uncertainties in |Vub| from the shape function may be significantly reduced.