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Article
Report number arXiv:1405.6376 ; CERN-PH-EP-2014-096 ; CERN-PH-EP-2014-096
Title Spin alignment and violation of the OZI rule in exclusive ω and ϕ production in pp collisions
Author(s) COMPASS collaboration  Mostrar todos los 209 autores
Publication 2014-09
Imprint 16 May 2014
Number of pages 24
Note 23 pages, 13 figures and 5 tables
In: Nucl. Phys. B 886 (2014) 1078-1101
DOI 10.1016/j.nuclphysb.2014.07.020
Subject category Particle Physics - Experiment
Accelerator/Facility, Experiment CERN SPS ; COMPASS NA58
Free keywords QCD ; branching fraction ; particle and resonance production ; experimental results ; OZI rule ; vector meson production ; tensor polarisation
Abstract Exclusive production of the isoscalar vector mesons ω and ϕ is measured with a 190 GeV/c proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable xF of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on xF and on the invariant mass MpV of the system formed by fast proton pfast and vector meson V is discussed in terms of diffractive production of pfastV resonances in competition with central production. The measurement of the spin density matrix element ρ00 of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on xF and on MpV are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to ω production which are absent in the case of the ϕ meson. Removing the low-mass MpV resonant region, the OZI rule is found to be violated by a factor of eight, independently of xF.
Copyright/License publication: © 2014-2025 The Author(s) (License: CC-BY-3.0), sponsored by SCOAP³
preprint: © 2014-2025 CERN (License: CC-BY-4.0)



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Email contact: andrea.bressan@cern.ch


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