Speaker
Description
The study of exotic hadrons has long been a topic of great interest for the understanding of Quantum Chromodynamics (QCD). As one of the light exotic hadrons, the structure and constituent quark content of $f_0(980)$ have been debated for decades, with theories suggesting it could be a tetraquark state ($s\bar sq\bar q$) or a hadronic molecule ($K\bar K$). Recently, the CMS experiment has measured the elliptic flow anisotropy $v_2$ of $f_0(980)$ in p-Pb collisions and concluded that $f_0(980)$ is an ordinary $s\bar s$ meson, based on the number-of-constituent-quarks (NCQ) scaling of elliptic flow [1]. Assuming that loosely bound light exotic hadrons can only survive at the kinetic freeze-out of the expanding hadronic matter, we have implemented the first $K\bar K$ coalescence model to a hybrid viscous hydrodynamic and hadronic transport model to calculate the $p_T$-spectra and elliptic flow of $f_0(980)$ in p-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. Using the well tuned phase-space distributions of kaons in this collision, our coalescence model results agree well with the CMS flow measurements, providing thus a strong evidence for the $K\bar K$ molecular nature of $f_0(980)$. Our study also indicates that the CMS Collaboration may have unjustifiably ruled out the $K\bar K$ molecular state of $f_0(980)$ by not considering the different $v_2$ scalings in the coalescence of hadrons and the coalescence of quarks[2].
References
[1] A. Hayrapetyan et al. (CMS), arXiv:2312.17092, 2023.
[2] Y. Wang, W. Zhao, C. M. Ko, F. Guo, J. Xie, H. Song, in preparation.
