The $\Upsilon\rightarrow X \gamma$ photon spectrum in the soft-energy region

Abstract

The dominant contribution of the next-to-leading order perturbative QCD corrections to the ϒ → Xγ photon energy spectrum for photon energies ω ∼ m b α s can be obtained trivially from the knowledge of the corresponding O(α) correction to the positronium decay spectrum in the same region. The latter can be obtained from the NRQED computation of the orthopositronium photon spectrum, or by applying the threshold expansion to the 1-loop QED amplitude, as it is explained in this talk.International Workshop on Effective Field Theories: from the pion to the upsilon

Precise determination of the eta_c mass and width in the radiative J/Psi -> eta_c gamma decay

“…The function a e (E γ ) has been discussed in Refs. [10,11]; a closed analytical form has been derived in [12].…”

Precise determination of the η[sub c] mass and width in the radiative J∕ψ→η[sub c]γ decay

“…The function a e (E γ ) has been discussed in Refs. [10,11]; a closed analytical form has been derived in [12]. In the weak-coupling regime, the typical momentum transfer in the charmonium is of order m c α s , the binding energy of the ground state is of order m c α 2 s and the hyperfine splitting is of order m c α 4 s .…”