The onset of spin rotation effects in electroproduction of heavy quarkonia

• We discuss the Melosh spin rotation effects in diffractive photo- and electroproduction of heavy quarkonia off a nucleon target in the dipole picture. The quarkonium light-front wave functions are obtained in the Schroedinger equation based formalism using the realistic interquark interaction potentials. A strong onset of spin rotation effects predicted in the case of J/ψ(1S) photoproduction enables us to reach a reasonable agreement with the available data. In the case of radially excited 2S and 3S states these effects are even stronger as a direct manifestation of the nodal structure of their wave functions. In particular, the spin effects enhance the Ψ0(2S) cross section by a factor of 2 − 3 and therefore cause a substantial increase of the Ψ0(2S)-to-J/Ψ(1S) ratio improving the description of experimental data.

Subject headings

NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

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