Spin structure of exclusive ω muoproduction at COMPASS

Bohdan Mariański

doi:10.1088/1742-6596/1435/1/012040

Abstract

Spin Density Matrix Elements (SDMEs) are determined for exclusive ω meson production on unpolarized protons, in the COMPASS kinematic region of 1.0 (GeV/c)2 < Q2 < 10.0 (GeV/c)2, 5.0 GeV/c2 < W < 17.0 GeV/c2 and . Using extracted the preliminary SDMEs values the hypothesis of S-Channel Helicity Conservation (SCHC) is studied. Certain matrix elements that correspond to the transition indicate violation of SCHC in exclusive ω production. A sizable contribution of unnatural parity exchange amplitudes is found for exclusive ω meson muoproduction, and there is a clear indication of its decrease with increasing W. The extracted longitudinal-to-transverse cross section ratio is 0.553 ± 0.044 ± 0.020.

Highlights

Spin Density Matrix Elements (SDMEs) are determined for exclusive ω meson production on unpolarized protons, in the COMPASS kinematic region of 1.0 (GeV/c)2 < Q2 < 10.0 (GeV/c)2, 5.0 GeV/c2 < W < 17.0 GeV/c2 and 0.01 (GeV/c)2 < p2T < 0.5 (GeV/c
Hard Exclusive Meson Production (HEMP) allows to study various quark-flavor combinatios of Generalized Parton Distributions (GPDs) and reaction mechanism. Most of this information we get from Spin Density Matrix Elements (SDMEs), wchich determine angular distributions of the particles from the decay of the vector meson
In case when contributions of transverse and longitudinal photons cannot be separated, the SDMEs are customarily defined as rλ04V λV = (ρ0λV λV + Rρ4λV λV )(1 + R)−1, rλαV λV =

Summary

Introduction

Spin Density Matrix Elements (SDMEs) are determined for exclusive ω meson production on unpolarized protons, in the COMPASS kinematic region of 1.0 (GeV/c)2 < Q2 < 10.0 (GeV/c)2, 5.0 GeV/c2 < W < 17.0 GeV/c2 and 0.01 (GeV/c)2 < p2T < 0.5 (GeV/c)2. The study of Hard Exclusive Meson Production (HEMP) allows to constrain models of Generalized Parton Distributions (GPDs).

Results

Conclusion