Dynamical model of J/ψ photoproduction on the nucleon

초록

A dynamical model based on a phenomenological charm quark -nucleon ( c - N ) potential v cN and the Pomeronexchange mechanism is constructed to investigate the J /1' photoproduction on the nucleon from threshold to invariant mass W = 300 GeV. The J /1' - N potential, V J /1' N ( r ), is constructed by folding v cN into the wave function 0 J /1' ( cc <overline>) of J /1' within a constituent quark model (CQM) of Segovia et al. [Int. J. Mod. Phys. E 22 , 1330026 (2013)]. A photoproduction amplitude is also generated by v cN by a cc <overline> -loop integration over the gamma -> cc <overline> vertex function and 0 J /1' ( cc <overline>). No commonly used vector meson dominance assumption is used to define this photoproduction amplitude which is needed to describe the data near the threshold. The c - N potential v c N ( r ) is parameterized in a form such that the predicted V J /1' N ( r ) at large distances has the same Yukawa potential form extracted from a lattice QCD (LQCD) calculation of Kawanai and Sasaki, [Phys. Rev. D 82 , 091501(R) (2010)]. The parameters of v cN are determined by fitting the total cross-section data of Jefferson Laboratory (JLab) by performing calculations that include J /1' - N final -state interactions (FSI). The resulting differential cross sections d cr / dt are found in good agreements with the data. It is shown that the FSI effects dominate the cross section in the very near -threshold region, allowing for sensitive testing of the predicted J /1' - N scattering amplitudes. By imposing the constraints of J /1' - N potential extracted from the LQCD calculation of Kawanai and Sasaki, [Phys. Rev. D 82 , 091501(R) (2010)], we have obtained three J /1' - N potentials which fit the JLab data equally well. The resulting J /1' - N scattering lengths are in the range of a = [ - 0 . 05 , - 0 . 25] fm. With the determined v c N ( r ) and the wave functions generated from the same CQM, the constructed model is used to predict the cross sections of photoproduction of q c (1 S ) and 1' (2 S ) mesons for future experimental tests.

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