Probing the exchanged object(s) in diffractive scattering

Abstract

The reaction mechanisms of the following proton diffractive scattering processes are studied and compared with one another: ${\gamma }^{\ast }p\to Vp,{\gamma }^{\ast }p\to Xp,pp\to (\Lambda K^{+})p$ and $pA\to \Lambda K^{+}A$ (Here, ${\gamma }^{\ast }$ stands for the space-like photon in inelastic electron-proton scattering, $V$ for the vector mesons $\rho ,\omega ,\varphi ,J/\psi$, and $A$ for a target nucleus.) It is shown that, by taking parity, and C--parity conservation into account, the existing data for these reactions strongly suggest the following: A considerable part of the objects exchanged between projectile and target in the above-mentioned processes are virtual quark-antiquark pairs in color-singlet states with $J^{PC}=0^{-+}$, $I^G=0^{+}$, where $J$ stands for total angular momentum, $I$ for isospin, $P$, $C$ and $G$ stand for parity, C-parity and G-parity respectively. Such quark-antiquark pairs are created by soft-gluon interactions. New experiments are suggested; and predictions for such experiments are made.

Comments: revised and extended version