Observation of new resonant structures in $\gamma \gamma \to \omega \phi$, $\phi \phi$ and $\omega \omega$

TL;DR

This paper reports the observation of new resonant structures in gamma-gamma collisions producing vector meson pairs, revealing previously unseen states and providing detailed measurements of their properties.

Contribution

It presents the first observation of new resonant structures below charmonium threshold in gamma-gamma to vector meson pairs, with spin-parity analysis and decay width measurements.

Findings

Discovery of new resonant structures below charmonium threshold.

Measurement of cross sections for gamma-gamma to vector meson pairs.

Determination of decay widths and branching fractions for observed states.

Abstract

The processes $\gamma \gamma \to \omega \phi$, $\phi \phi$, and $\omega \omega$ are measured using an 870 fb$^{-1}$ data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Production of vector meson pairs is clearly observed and their cross sections are measured for masses that range from threshold to 4.0 GeV. In addition to signals from well established spin zero and spin two charmonium states, there are clear resonant structures below charmonium threshold, which have not been previously observed. We report a spin-parity analysis for the new structures and determine the products of the $\etac$, $\chi_{c0}$, and $\chi_{c2}$ two-photon decay widths and branching fractions.