The first observation of coherent ϕ(1020) meson photoproduction off heavy nuclei is presented using ultraperipheral lead-lead collisions at a center-of-mass energy per nucleon pair of 5.36 TeV. The data were collected by the CMS experiment and correspond to an integrated luminosity of 1.62 μb−1. The ϕ(1020) meson signals are reconstructed via the K+K− decay channel. The production cross section is presented as a function of the ϕ(1020) meson rapidity in the range 0.3 < |y| < 1.0, probing gluons that carry a fraction of the nucleon momentum (x) around 10−4. The observed cross section exhibits little dependence on rapidity and is significantly suppressed, by a factor of ∼5, compared to a baseline model that treats a nucleus as a collection of free nucleons. Theoretical models that incorporate the nuclear shadowing effect generally provide a better description of the ϕ(1020) data than those incorporating gluon saturation. This study establishes a powerful new tool for exploring nuclear effects and nuclear gluonic structure in the small-x regime at a unique energy scale bridging the perturbative and nonperturbative quantum chromodynamics domains.

Observation of Coherent ϕ(1020) Meson Photoproduction in Ultraperipheral PbPb Collisions at sqrt(s_NN) = 5.36 TeV

Abbrescia, M.;Buonsante, M.;Colaleo, A.;D'Anzi, B.;Elmetenawee, W.;Louka, M.;Mastrapasqua, V.;My, S.;Nuzzo, S.;Pellecchia, A.;Pompili, A.;Radogna, R.;Simone, F.  M.;Stamerra, A.;Troiano, D.;Venditti, R.;Zaza, A.;Tenchini, F.;
2025-01-01

Abstract

The first observation of coherent ϕ(1020) meson photoproduction off heavy nuclei is presented using ultraperipheral lead-lead collisions at a center-of-mass energy per nucleon pair of 5.36 TeV. The data were collected by the CMS experiment and correspond to an integrated luminosity of 1.62 μb−1. The ϕ(1020) meson signals are reconstructed via the K+K− decay channel. The production cross section is presented as a function of the ϕ(1020) meson rapidity in the range 0.3 < |y| < 1.0, probing gluons that carry a fraction of the nucleon momentum (x) around 10−4. The observed cross section exhibits little dependence on rapidity and is significantly suppressed, by a factor of ∼5, compared to a baseline model that treats a nucleus as a collection of free nucleons. Theoretical models that incorporate the nuclear shadowing effect generally provide a better description of the ϕ(1020) data than those incorporating gluon saturation. This study establishes a powerful new tool for exploring nuclear effects and nuclear gluonic structure in the small-x regime at a unique energy scale bridging the perturbative and nonperturbative quantum chromodynamics domains.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11586/581680
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