Measurement of the cross-section ratio σψ (2S)/σ J/ψ (1S) in exclusive photoproduction at HERA



Abt, I, Adamus, M, Aggarwal, R, Aushev, V, Behnke, O, Bertolin, A, Bloch, I, Brock, I, Brook, NH, Brugnera, R
et al (show 72 more authors) (2022) Measurement of the cross-section ratio σψ (2S)/σ J/ψ (1S) in exclusive photoproduction at HERA. JOURNAL OF HIGH ENERGY PHYSICS, 2022 (12).

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Abstract

<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>The exclusive photoproduction reactions <jats:italic>γp</jats:italic> → <jats:italic>J/ψ</jats:italic>(1<jats:italic>S</jats:italic>)<jats:italic>p</jats:italic> and <jats:italic>γp</jats:italic> → <jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>)<jats:italic>p</jats:italic> have been measured at an <jats:italic>ep</jats:italic> centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373 pb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. The measurement was made in the kinematic range 30 <jats:italic>&lt; W &lt;</jats:italic> 180 GeV, <jats:italic>Q</jats:italic><jats:sup>2</jats:sup><jats:italic>&lt;</jats:italic> 1 GeV<jats:sup>2</jats:sup> and |<jats:italic>t</jats:italic>| <jats:italic>&lt;</jats:italic> 1 GeV<jats:sup>2</jats:sup>, where <jats:italic>W</jats:italic> is the photon-proton centre-of-mass energy, <jats:italic>Q</jats:italic><jats:sup>2</jats:sup> is the photon virtuality and <jats:italic>t</jats:italic> is the squared four-momentum transfer at the proton vertex. The decay channels used were <jats:italic>J/ψ</jats:italic>(1<jats:italic>S</jats:italic>) <jats:italic>→ μ</jats:italic><jats:sup>+</jats:sup><jats:italic>μ</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup>, <jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>) <jats:italic>→ μ</jats:italic><jats:sup>+</jats:sup><jats:italic>μ</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup> and <jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>) <jats:italic>→ J/ψ</jats:italic>(1<jats:italic>S</jats:italic>)<jats:italic>π</jats:italic><jats:sup>+</jats:sup><jats:italic>π</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup> with subsequent decay <jats:italic>J/ψ</jats:italic>(1<jats:italic>S</jats:italic>) <jats:italic>→ μ</jats:italic><jats:sup>+</jats:sup><jats:italic>μ</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup>. The ratio of the production cross sections, <jats:italic>R</jats:italic> = <jats:italic>σ</jats:italic><jats:sub><jats:italic>ψ</jats:italic>(2<jats:italic>S</jats:italic>)</jats:sub><jats:italic>/σ</jats:italic><jats:sub><jats:italic>J/ψ</jats:italic>(1<jats:italic>S</jats:italic>)</jats:sub>, has been measured as a function of <jats:italic>W</jats:italic> and |<jats:italic>t</jats:italic>| and compared to previous data in photoproduction and deep inelastic scattering and with predictions of QCD-inspired models of exclusive vector-meson production, which are in reasonable agreement with the data.</jats:p>

Item Type: Article
Uncontrolled Keywords: Diffraction, Heavy Quark Production, Lepton-Nucleon Scattering, Quarkonium
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 14 Mar 2023 14:56
Last Modified: 19 Oct 2023 09:26
DOI: 10.1007/JHEP12(2022)164
Open Access URL: https://doi.org/10.1007/JHEP12(2022)164
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3169057