Semileptonic decays from light to leptons: the extraction of the form factor from data

G. Martinelli; S. Simula; L. Vittorio

doi:10.1140/epjc/s10052-025-13972-x

EPJ

a
b
c
d
e
ap
st
h
plus
ds
pv
ti
qt
am
n

2023 Impact factor 4.2

Particles and Fields

Open Access

Eur. Phys. J. C (2025) 85: 242
https://doi.org/10.1140/epjc/s10052-025-13972-x

Regular Article - Theoretical Physics

Semileptonic $B \to D^{}$ $B \rightarrow D^$ decays from light to $τ$ $\tau$ leptons: the extraction of the form factor $F_{2}$ from data

G. Martinelli¹, S. Simula²^a and L. Vittorio³

¹ Physics Department and INFN Sezione di Roma La Sapienza, Piazzale Aldo Moro 5, 00185, Rome, Italy
² Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Via della Vasca Navale 84, 00146, Rome, Italy
³ LAPTh, Université Savoie Mont-Blanc and CNRS, 74941, Annecy, France

^a simula@roma3.infn.it

Received: 6 November 2024
Accepted: 19 February 2025
Published online: 8 March 2025

Abstract

We extend the Standard Model (SM) analysis of Martinelli et al. (Phys Rev D Ser 111:013005, 2025. https://doi.org/10.1103/PhysRevD.111.013005), which was limited to light leptons in the final state, to the semileptonic $B \to D^{*} τ ν_{τ}$ $B \rightarrow D^* \tau \nu _\tau$ decay. By using quantities that can be analised without the knowledge of $| V_{cb} |$ $\vert V_{cb}\vert$ , we derive important information about the helicity amplitudes and the hadronic form factors that can be compared with the predictions of lattice QCD calculations. In particular, there is a difficulty in reproducing simultaneously the experimental values of $R (D^{*})$ $$R(D^*)$$ and of other quantities relevant for the semitauonic decays within the SM. As a byproduct of our analysis, we also present a determination of $| V_{cb} |$ $\vert V_{cb}\vert$ from the total decay rate.

© The Author(s) 2025

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.