Speaker
Dr
Karin Schoenning
(Dept. of Physics and Astronomy, Uppsala University, and CERN)
Description
The Okubo-Zweig-Iizuka (OZI) rule states that processes with disconnected quark lines are suppressed. The production of phi mesons from non-strange hadrons is predicted to be suppressed w.r.t. omega by a factor 4.2•10^-3. Violations are often interpreted as gluonic intermediate states or as evidence for hidden strangeness in the nucleon. The reaction pp->pVp (V= omega, phi) has been studied with the COMPASS spectrometer in 2008 and 2009, using a 190 GeV/c proton beam impinging on a liquid hydrogen target.
The cross section ratio was measured and a significant OZI violation factor of ~4 was found. Its kinematic dependence of the Feynman x_F and the M(p V) mass is discussed in terms of diffractive production of baryon resonances in competition with central production.
The M(p omega) spectrum has a rich structure, indicating the importance of baryon resonances decaying into p omega, in sharp contrast to the structureless M(p phi) spectrum.
The spin density matrix element rho_00 of the vector mesons in selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on x_F and M(p V) are found.
Outside the resonant region, the OZI violation factor is ~8, independently of x_F.
Primary author
Dr
Karin Schoenning
(Dept. of Physics and Astronomy, Uppsala University, and CERN)
Co-author
Johannes Bernhard
(Johannes Gutenberg Universität, Mainz)
