Spin density matrix elements in exclusive ρ meson muoproduction

COMPASS Collaboration

doi:10.1140/epjc/s10052-023-11359-4

Spin density matrix elements in exclusive ρ meson muoproduction

COMPASS Collaboration

Department of Physics

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ρ 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<pT2< 0.5 (GeV/c) ² . Here, W denotes the mass of the final hadronic system, Q² the virtuality of the exchanged photon, and p_T the transverse momentum of the ρ 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 (γT∗→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 ρ production.

Original language	English
Article number	924
Journal	European Physical Journal C
Volume	83
Issue number	10
DOIs	https://doi.org/10.1140/epjc/s10052-023-11359-4
State	Published - Oct 2023

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@article{320f4d3120e64d41a3f1c47f80090aa8,

title = "Spin density matrix elements in exclusive ρ meson muoproduction",

abstract = "We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ρ 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) 22 . Here, W denotes the mass of the final hadronic system, Q2 the virtuality of the exchanged photon, and pT the transverse momentum of the ρ 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 (γT∗→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 ρ production.",

author = "COMPASS Collaboration and Alexeev, {G. D.} and Alexeev, {M. G.} and C. Alice and A. Amoroso and V. Andrieux and V. Anosov and K. Augsten and W. Augustyniak and Azevedo, {C. D.R.} and B. Badelek and J. Barth and R. Beck and Y. Bedfer and J. Bernhard and M. Bodlak and F. Bradamante and A. Bressan and Burtsev, {V. E.} and Chang, {W. C.} and C. Chatterjee and M. Chiosso and Chumakov, {A. G.} and Chung, {S. U.} and A. Cicuttin and Correia, {P. M.M.} and Crespo, {M. L.} and D. D{\textquoteright}Ago and Torre, {S. Dalla} and Dasgupta, {S. S.} and S. Dasgupta and Carro, {F. Del} and I. Denisenko and Denisov, {O. Yu} and Donskov, {S. V.} and N. Doshita and Ch Dreisbach and W. D{\"u}nnweber and Dusaev, {R. R.} and D. Ecker and A. Efremov and D. Eremeev and P. Faccioli and M. Faessler and M. Finger and jr, {M. Finger} and H. Fischer and Fl{\"o}thner, {K. J.} and W. Florian and Friedrich, {J. M.} and Lin, {P. J.}",

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doi = "10.1140/epjc/s10052-023-11359-4",

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volume = "83",

journal = "European Physical Journal C",

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TY - JOUR

T1 - Spin density matrix elements in exclusive ρ meson muoproduction

AU - COMPASS Collaboration

AU - Alexeev, G. D.

AU - Alexeev, M. G.

AU - Alice, C.

AU - Amoroso, A.

AU - Andrieux, V.

AU - Anosov, V.

AU - Augsten, K.

AU - Augustyniak, W.

AU - Azevedo, C. D.R.

AU - Badelek, B.

AU - Barth, J.

AU - Beck, R.

AU - Bedfer, Y.

AU - Bernhard, J.

AU - Bodlak, M.

AU - Bradamante, F.

AU - Bressan, A.

AU - Burtsev, V. E.

AU - Chang, W. C.

AU - Chatterjee, C.

AU - Chiosso, M.

AU - Chumakov, A. G.

AU - Chung, S. U.

AU - Cicuttin, A.

AU - Correia, P. M.M.

AU - Crespo, M. L.

AU - D’Ago, D.

AU - Torre, S. Dalla

AU - Dasgupta, S. S.

AU - Dasgupta, S.

AU - Carro, F. Del

AU - Denisenko, I.

AU - Denisov, O. Yu

AU - Donskov, S. V.

AU - Doshita, N.

AU - Dreisbach, Ch

AU - Dünnweber, W.

AU - Dusaev, R. R.

AU - Ecker, D.

AU - Efremov, A.

AU - Eremeev, D.

AU - Faccioli, P.

AU - Faessler, M.

AU - Finger, M.

AU - jr, M. Finger

AU - Fischer, H.

AU - Flöthner, K. J.

AU - Florian, W.

AU - Friedrich, J. M.

AU - Lin, P. J.

PY - 2023/10

Y1 - 2023/10

N2 - We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ρ 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) 22 . Here, W denotes the mass of the final hadronic system, Q2 the virtuality of the exchanged photon, and pT the transverse momentum of the ρ 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 (γT∗→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 ρ production.

AB - We report on a measurement of Spin Density Matrix Elements (SDMEs) in hard exclusive ρ 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) 22 . Here, W denotes the mass of the final hadronic system, Q2 the virtuality of the exchanged photon, and pT the transverse momentum of the ρ 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 (γT∗→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 ρ production.

UR - http://www.scopus.com/inward/record.url?scp=85174592149&partnerID=8YFLogxK

U2 - 10.1140/epjc/s10052-023-11359-4

DO - 10.1140/epjc/s10052-023-11359-4

M3 - 期刊論文

AN - SCOPUS:85174592149

SN - 1434-6044

VL - 83

JO - European Physical Journal C

JF - European Physical Journal C

IS - 10

M1 - 924

ER -

Spin density matrix elements in exclusive ρ meson muoproduction

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