Resonance searches at HERA

TL;DR

This paper reports on resonance searches at HERA, including meson production, glueball candidates, and charm pentaquark investigations, with some signals observed and others not confirmed, providing new measurements and limits.

Contribution

It presents new measurements of meson properties, searches for exotic states like the charm pentaquark, and compares results with previous experiments, expanding understanding of resonance phenomena at HERA.

Findings

Significant production of tensor mesons and f0(1710) observed.

Charm pentaquark candidate not confirmed with higher statistics.

Measured properties of excited charm and charm-strange mesons.

Abstract

Inclusive production of K0S K0S in ep collisions was studied with the ZEUS detector. Significant production of JPC=2++ tensor mesons and of the 0++ glueball candidate f0(1710) was seen. Masses and widths were compared with previous experiments. The H1 Collaboration saw a charm pentaquark candidate in the D*p spectrum at 3.1 GeV, which was not confirmed by a ZEUS higher statistics search. With the full HERA data, H1 did not see a signal in this region. Masses, widths and helicity parameters of excited charm and charm-strange mesons were measured by ZEUS. Rates of c-quarks hadronising into these mesons were determined and a search for a radially excited charm meson was performed.