Whether new data on $D_s\to f_0(980) e^+ \nu_e$ can be understood if $f_0(980)$ consists of only the conventional $q\bar{q}$ structure

TL;DR

This paper investigates whether the scalar meson $f_0(980)$ can be explained as a conventional quark-antiquark state using recent decay data, challenging the common assumption of its dominant $sar s$ component.

Contribution

The study calculates $D_s o f_0(980)$ form factors in the light-front quark model and fits experimental data to determine the meson's quark composition.

Findings

The mixing angle suggests $f_0(980)$ may not be predominantly $sar s$.

The calculated branching ratio aligns with experimental measurements.

The analysis questions the conventional quark model interpretation of $f_0(980)$.

Abstract

Only two isospin-singlet scalar mesons $f_0(600)$ ($\sigma$) and $f_0(980)$ exist below 1 GeV, so that it is natural to suppose that they are two energy eigenstates which are mixtures of ${1\over\sqrt 2}(u\bar u+d\bar d)$ and $s\bar s$. Is this picture right? Generally, it is considered that $f_0(600)$ mainly consists of ${1\over\sqrt 2}(u\bar u+d\bar d)$, if so, the dominant component of $f_0(980)$ should be $s\bar s$. The recent measurement of the CLEO collaboration on the branching ratio of $D_s\to f_0(980) e^+ \nu_e$ provides an excellent opportunity to testify the structure of $f_0(980)$, namely whether the data can be understood as long as it consists of mainly the conventional $q\bar q$ structure. We calculate the form factors of $D_s\to f_0(980)$ in the light-front quark model (LFQM) and the corresponding branching ratio of the semileptonic decay. By fitting the data, we obtain the mixing angle $\phi$. The obtained mixing angle shows that the $s\bar s$ component in $f_0(980)$ may not be dominant.