Spin density matrix elements in exclusive ρ.sup.0./sup. meson muoproduction

0579249 - ÚPT 2024 RIV DE eng J - Journal Article
Alexeev, G. D. - Alexeev, M. G. - Alice, C. - Amoroso, A. - Andrieux, V. - Anosov, V. - Augsten, K. - Augustyniak, W. - Azevedo, C. D. R. - Badelek, B. - Barth, J. - Beck, R. - Bedfer, Y. - Bernhard, J. - Bodlák, M. - Bradamante, F. - Bressan, A. - Burtsev, V. E. - Chang, W.-C. - Chatterjee, C. - Chiosso, M. - Chumakov, A. G. - Chung, S. U. - Cicuttin, A. - Correia, P. M. M. - Crespo, M. L. - D'Ago, D. - Dalla Torre, S. - Dasgupta, S. S. - Dasgupta, S. - Srnka, Aleš … Total 190 authors
Spin density matrix elements in exclusive ρ⁰ meson muoproduction.
European Physical Journal C. Roč. 83, č. 10 (2023), č. článku 924. ISSN 1434-6044. E-ISSN 1434-6052
Institutional support: RVO:68081731
Keywords : COMPASS * spin density matrix elements * meson muoproduction * liquid hydrogen target
OECD category: Particles and field physics
Impact factor: 4.4, year: 2022
Method of publishing: Open access
https://link.springer.com/article/10.1140/epjc/s10052-023-11359-4

We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ρ0 meson muoproduction at COMPASS using 160~GeV/c polarised μ+ and μ− beams impinging on a liquid hydrogen target. The measurement covers the kinematic range 5.0~GeV/c2 <W< 17.0~GeV/c2, 1.0 (GeV/c)2 <Q2< 10.0 (GeV/c)2 and 0.01 (GeV/c)2 <p2T< 0.5 (GeV/c)2. Here, W denotes the mass of the final hadronic system, Q2 the virtuality of the exchanged photon, and pT the transverse momentum of the ρ0 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 dominant contribution of natural-parity-exchange transitions and a very small contribution of unnatural-parity-exchange transitions, which is compatible with zero within experimental uncertainties. The results provide important input for modelling Generalised Parton Distributions (GPDs). In particular, they may allow one to evaluate in a model-dependent way the role of parton helicity-flip GPDs in exclusive ρ0 production.
Permanent Link: https://hdl.handle.net/11104/0348129