1207.3561 (Dian-Yong Chen et al.)

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

Dian-Yong Chen, Jun He, Xiang Liu, Takayuki Matsuki

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 letter, 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 $\gamma\gamma\to D\bar{D}$. In addition, we also extract the resonance parameters of $\chi_{c0}(2P)$ and $\chi_{c2}(2P)$ which show that these are two narrow resonances with masses very close to each other, i.e., $M_{\chi_{c0}(2P)}=3.92$ GeV with $\Gamma_{\chi_{c0}(2P)}=8.07$ MeV and $M_{\chi_{c2}(2P)}=3.94$ GeV with $\Gamma_{\chi_{c2}(2P)}=11.98$ MeV. These results 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 SupreB.

View original: http://arxiv.org/abs/1207.3561