A partial wave analysis of proton-antiproton annihilation above threshold for &phis;&phis; production in the JETSET experiment

Date of Completion

January 2006


Physics, Nuclear




The JETSET experiment (PS202) conducted at CERN was designed to search for gluonic resonances in the mass range between 2.14 and 2.43 GeV/ c2 using the channel. pp¯ → &phis;&phis; → 4K±. This channel is OZI suppressed, thus any observed enhancement of the cross section above a level consistent with the OZI rule could indicate possible resonating gluonic degrees of freedom. In fact, the measured cross section is two orders of magnitude larger than the OZI prediction and shows an enhancement centered near 2.2 GeV/ c2 of width 50-100 MeV/c2 . A partial wave analysis (PWA) has been conducted in order to search for the dominant partial waves. The formalism and methods of this PWA will be fully developed. This analysis has revealed the dominance of Jpc = 2++ together with a significant Jpc = 4++ component. Because the &phis; resonance is only 4 MeV wide, the PWA is relatively insensitive to the presence of competing channels coupling to the 4K± final state. The partial wave analysis was carried out including a non-resonant 4K± phase-space component added incoherently to the &phis;&phis; intensity to account for the background beneath the &phis;&phis; peak observed in the Dalitz plot. As a test of the sensitivity of the PWA results to this background treatment, the analysis was repeated including a contribution from the f0f 0 → 4K± intermediate state added coherently to the &phis;&phis; waves, in addition to the incoherent phase-space background. The addition of the f0 f0 channel improves the overall quality of the fit, but the &phis;&phis; results are mostly unaffected. In the 2.2 GeV/c 2 region, the cross section is dominated by 2++ &phis;&phis; waves, but no clear evidence of a narrow resonance is observed. ^