Lattice calculation of $χ_{c0} \rightarrow 2γ$ decay width

Abstract

We perform a lattice QCD calculation of the χc0 → 2γ 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 Γγγ(χc0) = 3.71(0.84)stat(0.70)syst keV. Albeit this large statistical error, our result is compatible with the experimental results within 1.4σ. Potential improvements of the lattice calculation in the future are also discussed.

Two-photon transitions of charmonia on the light front

“…The TFF at Q 2 = 0 is accessed from the two-photon decay width Γ S→γγ from various processes as compiled by PDG [27]. Our predictions using the LFWFs (15) as well as using the LCDA (17) are both in agreement with the experimental data despite the low statistics. The BLFQ/DA prediction is scaled by F Sγ (0) obtained from BLFQ.…”

“…Lattice computation of the two-photon transition with off-shell photons is particularly challenging, as demonstrated by the large discrepancy between theoretical predictions and the PDG value, since the energetic virtual photon is not an eigenstate of the QCD Hamiltonian [11]. Nevertheless, strides have been made to access the twophoton width [10,[12][13][14][15], and transition form factors [10,12]. Calculations from other relativistic approaches, notably DSE/BSE, have also been reported in the literature and appear successful [16].…”