Lattice calculation of ${\chi }_{c0}\to 2\gamma$ decay width

Abstract

We perform a lattice QCD calculation of the ${\chi }_{c0}\to 2\gamma$ decay width using a model-independent method which does not require a momentum extrapolation of the corresponding off-shell form factors. The simulation is performed on ensembles of $N_f=2$ twisted mass lattice QCD gauge configurations with three different lattice spacings. After a continuum extrapolation, the decay width is obtained to be ${\Gamma }_{\gamma \gamma }({\chi }_{c0})=3.65(83{)}_{\mathrm{stat}}(21{)}_{lat.syst}(66{)}_{\mathrm{syst}}\text{keV}$. Albeit this large statistical error, our result is compatible with the experimental results within 1.3$\sigma$. Potential improvements of the lattice calculation in the future are also discussed.

Comments: 9 pages, 3 figures