Does the enhancement observed in $\gamma\gamma\to D\bar{D}$ contain two $P$-wave higher charmonia?

TL;DR

This paper suggests that the observed enhancement Z(3930) in gamma-gamma to D D-bar may actually contain two P-wave higher charmonia states, providing new insights into charmonium spectroscopy.

Contribution

The study proposes that Z(3930) includes both chi_c0(2P) and chi_c2(2P) states, supported by analysis of invariant mass spectrum and angular distribution data.

Findings

Support for the two-state hypothesis in Z(3930) enhancement

Analysis of D D-bar spectrum consistent with two P-wave charmonia

Provides testable predictions for future experiments at BelleII and SuperB

Abstract

Solved is a new puzzle raised by the observation of an enhancement structure Z(3930) in $\gamma\gamma\to D\bar{D}$. If categorizing Z(3930) as $\chi_{c2}(2P)$ suggested by Belle and BaBar, we must explain why $\chi_{c0}(2P)$ dominantly decaying into $D\bar{D}$ is missing in the $D\bar{D}$ invariant mass spectrum. In this work, we propose that the Z(3930) enhancement structure may contain two $P$-wave higher charmonia {$\chi_{c0}(2P)$} and $\chi_{c2}(2P)$. We show that this assumption is supported by our analysis of the $D\bar{D}$ invariant mass spectrum and $\cos\theta^\ast$ distribution of $\gamma\gamma\to D\bar{D}$. This observation would not only provide valuable information of two P-wave higher charmonia $\chi_{c0}(2P)$ and $\chi_{c2}(2P)$, but also serve as the crucial test of our novel proposal to the observed enhancement structure Z(3930), especially at the forthcoming BelleII and the approved SuperB.