Observation of $\chi_{c1}$ decays into vector meson pairs $\phi\phi$, $\omega\omega$, and $\omega\phi$

TL;DR

This paper reports the first observation of $oldsymbol{ ext{chi}_{c1}}$ decays into vector meson pairs, measuring branching fractions and indicating significant violations of the hadron helicity selection rule, with implications for understanding OZI suppression.

Contribution

It provides the first measurements of $oldsymbol{ ext{chi}_{c1}}$ decays into vector mesons and explores violations of the hadron helicity selection rule in these processes.

Findings

First observation of $ ext{chi}_{c1}$ decays into $oldsymbol{ ext{phi} ext{phi}}$, $oldsymbol{ ext{omega} ext{omega}}$, and $oldsymbol{ ext{omega} ext{phi}}$.

Measured branching fractions for these decays with improved precision.

Evidence of significant violation of the hadron helicity selection rule in $ ext{chi}_{cJ}$ decays.

Abstract

Decays of $\chi_{c1}$ to vector meson pairs $\phi\phi$, $\omega\omega$ and $\omega\phi$ are observed for the first time using $(106\pm4)\times 10^6$ $\psip$ events accumulated at the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are measured to be $(4.4\pm 0.3\pm 0.5)\times 10^{-4}$, $(6.0\pm 0.3\pm 0.7)\times 10^{-4}$, and $(2.2\pm 0.6\pm 0.2)\times 10^{-5}$, for $\chi_{c1}\to \phi\phi$, $\omega\omega$, and $\omega\phi$, respectively. The observation of $\chi_{c1}$ decays into a pair of vector mesons $\phi\phi$, $\omega\omega$ and $\omega\phi$ indicates that the hadron helicity selection rule is significantly violated in $\chi_{cJ}$ decays. In addition, the measurement of $\chi_{cJ}\to \omega\phi$ gives the rate of doubly OZI-suppressed decay. Branching fractions for $\chi_{c0}$ and $\chi_{c2}$ decays into other vector meson pairs are also measured with improved precision.