Spin density matrix elements in exclusive ω meson muoproduction
| Parent link: | European Physical Journal C Vol. 81, iss. 2.— 2021.— [126, 22 p.] |
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| Autor corporatiu: | , |
| Altres autors: | , , , , , , , , |
| Sumari: | Title screen We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ωω meson muoproduction on the proton at COMPASS using 160 GeV/c polarised μ+ and μ− beams impinging on a liquid hydrogen target. The measurement covers the range 5.0 GeV/c2 <W< 17.0 GeV/c2, with the average kinematics ⟨Q2⟩= 2.1 (GeV/c)2, ⟨W⟩=7.6⟨W⟩=7.6 GeV/c2, and ⟨p2T⟩=0.16 (GeV/c)2. Here, Q2 denotes the virtuality of the exchanged photon, W the mass of the final hadronic system and pT the transverse momentum of the ωω 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 (γ∗T→VL) 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 ω production. |
| Idioma: | anglès |
| Publicat: |
2021
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| Matèries: | |
| Accés en línia: | https://doi.org/10.1140/epjc/s10052-020-08740-y |
| Format: | Electrònic Capítol de llibre |
| KOHA link: | https://koha.lib.tpu.ru/cgi-bin/koha/opac-detail.pl?biblionumber=668070 |
| Sumari: | Title screen We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ωω meson muoproduction on the proton at COMPASS using 160 GeV/c polarised μ+ and μ− beams impinging on a liquid hydrogen target. The measurement covers the range 5.0 GeV/c2 <W< 17.0 GeV/c2, with the average kinematics ⟨Q2⟩= 2.1 (GeV/c)2, ⟨W⟩=7.6⟨W⟩=7.6 GeV/c2, and ⟨p2T⟩=0.16 (GeV/c)2. Here, Q2 denotes the virtuality of the exchanged photon, W the mass of the final hadronic system and pT the transverse momentum of the ωω 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 (γ∗T→VL) 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 ω production. |
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| DOI: | 10.1140/epjc/s10052-020-08740-y |