Search for exclusive photoproduction of Z$_c^{\pm}$(3900) at COMPASS

TL;DR

This paper reports a search for the exclusive production of the Zc(3900) hadron via virtual photons in high-energy muon-nucleon collisions, setting an upper limit on its production cross-section relative to J/psi production.

Contribution

The study provides the first experimental upper limit on the exclusive photoproduction cross-section of Zc(3900) at COMPASS energies, using a comprehensive dataset collected over nearly a decade.

Findings

No significant signal observed for Zc(3900) production.

Established an upper limit of 3.7×10^{-3} for the production ratio.

Results constrain models of Zc(3900) production mechanisms.

Abstract

A search for the exclusive production of the $Z_c^{\pm}(3900)$ hadron by virtual photons has been performed in the channel $Z_c^{\pm}(3900)\rightarrow J/\psi \pi^{\pm}$. The data cover the range from 7 GeV to 19 GeV in the centre-of-mass energy of the photon-nucleon system. The full set of the COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio $BR(Z_c^{\pm}(3900)\rightarrow J/\psi \pi^{\pm} )\times \sigma_{ \gamma~N \rightarrow Z_c^{\pm}(3900)~ N} /\sigma_{\gamma~N \rightarrow J/\psi~ N}$ of $3.7\times10^{-3}$ has been established at the confidence level of 90%.