Spin density matrix elements in exclusive ω meson muoproduction

Abstract: We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive meson muoproduction on the proton at COMPASS using 160 GeV/c polarised and beams impinging on a liquid hydrogen target. The measurement covers the range 5.0 GeV/ 17.0 GeV/, with the average kinematics 2.1 (GeV/c), GeV/, and (GeV/c). Here, denotes the virtuality of the exchanged photon, W the mass of the final hadronic system and the transverse momentum of the meson with respect to the virtual-photon direction. The measured non-zero SDMEs for the transitions of transversely polarised virtual photons to longitudinally polarised vector mesons () indicate a violation of s-channel helicity conservation. Additionally, we observe a sizeable contribution of unnatural-parity-exchange (UPE) transitions that decreases with increasing W. The results provide important input for modelling Generalised Parton Distributions (GPDs). In particular, they may allow to evaluate in a model-dependent way the contribution of UPE transitions and assess the role of parton helicity-flip GPDs in exclusive production

Standort
Deutsche Nationalbibliothek Frankfurt am Main
Umfang
Online-Ressource
Sprache
Englisch
Anmerkungen
The European physical journal. C. - 81, 2 (2021) , 126, ISSN: 1434-6052

Ereignis
Veröffentlichung
(wo)
Freiburg
(wer)
Universität
(wann)
2024
Urheber

DOI
10.1140/epjc/s10052-020-08740-y
URN
urn:nbn:de:bsz:25-freidok-2475540
Rechteinformation
Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
Letzte Aktualisierung
14.08.2025, 10:58 MESZ

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