Helicity amplitudes in the decay with V-A breaking in the quark sector

L. R. Dai; E. Oset

doi:10.1140/epja/s10050-020-00160-6

EPJ

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

2024 Impact factor 2.8

Hadrons and Nuclei

Eur. Phys. J. A (2020) 56: 154
https://doi.org/10.1140/epja/s10050-020-00160-6

Regular Article - Theoretical Physics

Helicity amplitudes in the ${\bar{B}} \rightarrow D^{*} {\bar{\nu }}_\tau \tau$ decay with V-A breaking in the quark sector

L. R. Dai¹^,2^* and E. Oset³

¹ School of Science, Huzhou University, Huzhou, 313000, Zhejiang, China
² Department of Physics, Liaoning Normal University, Dalian, 116029, China
³ Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigacíon de Paterna, Aptdo. 22085, 46071, Valencia, Spain

^* e-mail: dailianrong68@126.com

Received: 2 March 2020
Accepted: 5 May 2020
Published online: 28 May 2020

Abstract

In view of the recent measurement of the $F_L^{D^*}$ magnitude in the ${\bar{B}} \rightarrow D^{*} {\bar{\nu }}_\tau \tau$ reaction we evaluate this magnitude within the standard model and for a family of models with the $\gamma ^\mu -\alpha \gamma ^\mu \gamma _5$ current structure for the quarks for different values of $\alpha$ . At the same time we evaluate also the transverse contributions, $$M=-1$$ , $$M=+1$$ , and find that the difference between the and contributions is far more sensitive to changes in $\alpha$ than the longitudinal component. These findings should be looked as an incentive to measure the transverse helicities which are bound to be a far more sensitive magnitude to possible new physics than $F_L^{D^*}$ .