https://doi.org/10.1140/epjc/s10052-019-6666-y
Regular Article - Theoretical Physics
Spin rotation effects in diffractive electroproduction of heavy quarkonia
1
Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaiso, Chile
2
FNSPE, Czech Technical University in Prague, Břehová 7, 11519, Prague, Czech Republic
3
Department of Astronomy and Theoretical Physics, Lund University, 223 62, Lund, Sweden
4
Nuclear Physics Institute ASCR, 25068, Řež, Czech Republic
5
Departamento de Física, CFM, Universidade Federal de Santa Catarina, C.P. 476, Florianópolis, SC, CEP 88.040-900, Brazil
* e-mail: jan.nemcik@fjfi.cvut.cz
Received:
18
December
2018
Accepted:
8
February
2019
Published online:
20
February
2019
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 
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 
these effects are even stronger leading to an increase of the photoproduction cross section by a factor of 
depending on the photon energy. Even in production of radially excited 
and 
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 
following universality properties in production of different heavy quarkonia as a function of 
.
© The Author(s), 2019
