Eur. Phys. J. C (2026) 86: 103
https://doi.org/10.1140/epjc/s10052-026-15295-x

Regular Article - Theoretical Physics

The ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }$ transition form factors in perturbative QCD approach

¹ Centre for Theoretical Physics, Henan Normal University, 453007, Xinxiang, China
² Frontiers Science Center for Rare Isotopes, and School of Nuclear Science and Technology, Lanzhou University, 730000, Lanzhou, China
³ Center for High Energy Physics, Henan Academy of Sciences, 455004, Zhengzhou, China

^a This email address is being protected from spambots. You need JavaScript enabled to view it.
^b This email address is being protected from spambots. You need JavaScript enabled to view it.
^c This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 26 August 2025
Accepted: 29 December 2025
Published online: 2 February 2026

Abstract

We perform a systematic analysis of the ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }$ transition form factors using the perturbative QCD (PQCD) approach, taking into account contributions from higher-twist light-cone distribution amplitudes (LCDAs). Using inputs from lattice QCD, we show that the baryon higher-twist LCDAs give numerically dominant contributions to the form factors. By combining our PQCD results at low-$q^2$ region with lattice QCD predictions at high $q^2,$ we carry out z-series expansion fits to obtain a unified description of the form factors over the full physical kinematic range. We also provide predictions for physical observables in the rare decay ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\mu }^{+}{\mu }^{-},$ such as the differential branching fraction, the longitudinal polarization fraction of the dimuon system, and the forward–backward asymmetries.