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arXiv · 1411.6426

Lattice QCD estimate of the $η_{c}(2S)\to J/ψγ$ decay rate

Damir Becirevic·Michael Kruse·Francesco Sanfilippo
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Abstract

We compute the hadronic matrix element relevant to the physical radiative decay $η_{c}(2S)\to J/ψγ$ by means of lattice QCD. We use the (maximally) twisted mass QCD action with Nf=2 light dynamical quarks and from the computations made at four lattice spacings we were able to take the continuum limit. The value of the mass ratio $m_{η_c(2S)}/m_{η_c(1S)}$ we obtain is consistent with the experimental value, and our prediction for the form factor is $V^{η_{c}(2S)\to J/ψγ}(0)\equiv V_{12}(0)=0.32(6)(2)$, leading to $Γ(η_c (2S) \to J/ψγ) = (15.7\pm 5.7)$ keV, which is much larger than $Γ(ψ(2S) \to η_cγ)$ and within reach of modern experiments.

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Damir Becirevic, Michael Kruse, Francesco Sanfilippo. 2014-11-24. Lattice QCD estimate of the $η_{c}(2S)\to J/ψγ$ decay rate. https://doi.org/10.1007/jhep05(2015)014

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