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arXiv · 2110.05219

A new method for a lattice calculation of $\eta_c \rightarrow 2\gamma$

Yu Meng
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Abstract

We propose a direct method to calculate the decay width of a hadron decaying to two photons, which is conventionally obtained by an extrapolation for various off-shell form factors. The new method provides an simple way to examine the finite-volune effects. As an example, we apply the method to $\eta_c\rightarrow 2\gamma$. Using three $N_f=2$ twisted-mass gauge ensembles with different lattice spacings, we obtain the final decay width $\Gamma_{\eta_c\gamma\gamma}=6.57(15)_{\textrm{stat}}(8)_{\textrm{syst}}$ keV, where the systematic error accounts for the fine-tuning of the charm quark mass. This method can also be applied for other processes which involve the leptonic or radiative particles in the final states.

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BibTeXRIS

Yu Meng. 2021-10-11. A new method for a lattice calculation of $\eta_c \rightarrow 2\gamma$. https://doi.org/10.22323/1.396.0618

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