Evidence for a new resonance and search for the Y(4140) in $\gamma \gamma \to \phi J/\psi$

TL;DR

This study reports the observation of a new resonance, X(4350), in gamma-gamma collisions producing phi J/psi, and sets limits on the Y(4140) production, challenging its interpretation as a D_s* D_s* molecule.

Contribution

First evidence of the X(4350) resonance in gamma-gamma to phi J/psi, with measurements of its properties and constraints on the Y(4140) production, providing insights into exotic meson states.

Findings

Observation of X(4350) with 3.2 sigma significance.

Measured mass and width of X(4350).

No evidence for Y(4140) in gamma-gamma collisions.

Abstract

The process $\gamma \gamma \to \phi \jpsi$ is measured for $\phi \jpsi$ masses between threshold and 5 GeV/${\it c}^2$, using a data sample of 825 fb$^{-1}$ collected with the Belle detector. A narrow peak of $8.8^{+4.2}_{-3.2}$ events, with a significance of 3.2 standard deviations including systematic uncertainty, is observed. The mass and natural width of the structure (named X(4350)) are measured to be $(4350.6^{+4.6}_{-5.1}(\rm{stat})\pm 0.7(\rm{syst})) \hbox{MeV}/{\it c}^2$ and $(13^{+18}_{-9}(\rm{stat})\pm 4(\rm{syst})) \hbox{MeV}$, respectively. The product of its two-photon decay width and branching fraction to $\phi\jpsi$ is $(6.7^{+3.2}_{-2.4}(\rm{stat}) \pm 1.1(\rm{syst})) \hbox{eV}$ for $J^P=0^+$, or $(1.5^{+0.7}_{-0.6}(\rm{stat}) \pm 0.3(\rm{syst})) \hbox{eV}$ for $J^P=2^+$. No signal for the $Y(4140)\to \phi \jpsi$ structure reported by the CDF Collaboration in $B\to K^+ \phi \jpsi$ decays is observed, and limits of $\Gamma_{\gamma \gamma}(Y(4140)) \BR(Y(4140)\to\phi \jpsi)<41 \hbox{eV}$ for $J^P=0^+$ or $<6.0 \hbox{eV}$ for $J^P=2^+$ are determined at the 90% C.L. This disfavors the scenario in which the Y(4140) is a $D_{s}^{\ast+} {D}_{s}^{\ast-}$ molecule.