# A Virtual Tribute to Quark Confinement and the Hadron Spectrum 2021

Aug 2 – 6, 2021
online
Europe/Brussels timezone

## Light meson spectroscopy and exotics

Aug 6, 2021, 2:30 PM
20m
online

#### online

Parallel contribution B: Light quarks

### Speaker

Mikhail Mikhasenko (CERN)

### Description

High statistics samples from modern experiments triggered an essential work on revisiting theoretical models and tools applied to analyze the resonance phenomena of QCD.

In this talk, I will discuss two exotic-resonance candidates, $a_1(1420)$ and $\pi_1(1600)$ cleared up over the last few years using data of the COMPASS experiment.

With our recent analysis [hep-ph:2006.05342], the $a_1(1420)$ candidate is concluded to be consistent with the manifestation of the Triangle Singularity (TS) in the coupled system of 3pi and KKpi. The TS mechanism, claimed to be responsible for the appearance of the several XYZ states in the charmonium spectrum,
is usually difficult to test due to unknown couplings and production rates. In contrast, the description of the $a_1(1420)$ is nearly-model independent due to the known pair-wise interaction of the light hadrons. It makes the $a_1(1420)$ the best test ground for our understanding of the TS, the fundamental field-theory phenomenon.

The pole of the $\pi_1(1600)$ resonance was established recently by the JPAC group in the analysis of $\eta^{(\prime)}\pi$. I will present new work on relating the appearance of this exotic state to the exchange dynamics in $\eta^{(\prime)}\pi$ system showing the particle-force duality for the exotic state [hep-ph:2104.10646].