Abstract
We compute the hadronic matrix element relevant to the physical radiative decay η c (2S) → J/ψγ by means of lattice QCD. We use the (maximally) twisted mass QCD action with N f = 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 ηc (2S)/m ηc(1S) we obtain is consistent with the experimental value, and our prediction for the form factor is V ηc(2S)→J/ψΥ (0) ≡ V 12(0) = 0.32(6)(2), leading to Γ(η c (2S) → J/ψγ) = (15.7 ± 5.7) keV, which is much larger than Γ(ψ(2S) → η c γ) and within reach of modern experiments.
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ArXiv ePrint: 1411.6426
Laboratoire de Physique Théorique est une unité mixte de recherche du CNRS, UMR 8627.
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Bečirević, D., Kruse, M. & Sanfilippo, F. Lattice QCD estimate of the η c (2S) → J/ψγ decay rate. J. High Energ. Phys. 2015, 14 (2015). https://doi.org/10.1007/JHEP05(2015)014
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DOI: https://doi.org/10.1007/JHEP05(2015)014