Abstract
In this work we present for the first time the comprehensive study of the Melosh spin rotation effects in diffractive electroproduction of S-wave heavy quarkonia off a nucleon target. Such a study has been performed within the color dipole approach using, as an example and a reference point, two popular parametrizations of the dipole cross section and two potentials describing the interaction between Q and Q¯ and entering in the Schrödinger equation based formalism for determination of the quarkonia wave functions. We find a strong onset of spin rotation effects in 1S charmonium photoproduction which is obviously neglected in present calculations of corresponding cross sections. For photoproduction of radially excited ψ ′ (2 S) these effects are even stronger leading to an increase of the photoproduction cross section by a factor of 2 ÷ 3 depending on the photon energy. Even in production of radially excited Υ ′ (2 S) and Υ ′ ′ (3 S) they can not be neglected and cause the 20–30% enhancement of the photoproduction cross section. Finally, we predict that the spin effects vanish gradually with photon virtuality Q 2 following universality properties in production of different heavy quarkonia as a function of Q2+MV2.
Original language | English |
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Article number | 154 |
Journal | European Physical Journal C |
Volume | 79 |
Issue number | 2 |
Early online date | 2019 Feb 20 |
DOIs | |
Publication status | Published - 2019 |
Subject classification (UKÄ)
- Subatomic Physics