Test of the OZI rule in vector meson production with the COMPASS experiment

Abstract

The COMPASS experiment at CERN collected a large set of data with hadron beams (p, π K) and different targets (H2, Pb, Ni, W) in the years 2008 and 2009. The main goal is the search for exotic bound states of quarks and gluons (glueballs, hybrids) and several preliminary results from the ongoing analysis have already emerged.The production of exotic states is known to be favoured in glue-rich environments, e.g. so-called OZI-forbidden processes. The Okubo-Zweig-Iizuka (OZI) rule states that processes with disconnected quark line diagrams are suppressed. As a consequence, states with an ss̄ component should be suppressed with respect to states containing mainly u and d quarks. The numerous reported violations of the OZI rule show that the underlying physics is more complicated. By studying the degree of OZI violation a lot can learned about the production mechanism and possibly also about the nucleon structure itself. The uniquely large COMPASS data sample allows for detailed studies with respect to kinematic variables (e.g. xF). Results from the ongoing analysis on the comparison of ω and ϕ vector mesons production in pp → pp (ω/ϕ) are presented and an outlook on the prospect of spin alignment measurements with COMPASS is given.