Heavy quark expansion of $\Lambda_b\to\Lambda^*(1520)$ form factors beyond leading order

TL;DR

This paper extends the Heavy Quark Expansion analysis of $ ext{Lambda}_b o ext{Lambda}^*(1520)$ form factors by including next-to-leading-order and power corrections, fitting to lattice QCD data, and examining their compatibility.

Contribution

It introduces the first inclusion of next-to-leading-power $ ext{O}(1/m_b)$ corrections in the form factor parametrization and assesses the consistency with lattice QCD results.

Findings

Identifies tension between Heavy Quark Expansion and lattice QCD data for tensor form factors.

Highlights potential underestimation of lattice QCD uncertainties.

Suggests higher order terms may be needed for better agreement.

Abstract

I review the parametrisation of the full set of $\Lambda_b\to\Lambda^* (1520)$ form factors in the framework of Heavy Quark Expansion, including next-to-leading-order $\mathcal{O}(\alpha_s)$ and, for the first time, next-to-leading-power $\mathcal{O}(1/m_b)$ corrections. The unknown hadronic parameters are obtained by performing a fit to recent lattice QCD calculations. I investigate the compatibility of the Heavy Quark Expansion and the current lattice data, finding tension between these two approaches in the case of tensor and pseudo-tensor form factors, whose origin could come from an underestimation of the current lattice QCD uncertainties and higher order terms in the Heavy Quark Expansion.