Dark photon production via inelastic proton bremsstrahlung with Pauli form factor

We study the production of vector portal mediators, dark photons, with masses in the range 0.4--1.8\,GeV in proton-proton collisions via the process of inelastic proton bremsstrahlung. In contrast to previous studies, we take into account the contribution of Pauli electromagnetic form factor to differential cross section and introduce two new splitting functions of the proton. We show that their contributions can become leading in the mass region 0.9--1.8\,GeV and present the updated estimate for the sensitivity of the future SHiP experiment to visible decays of dark photons.
Comment: 10 pages, 3 figures, contribution to the Scientific Session of the Physical Sciences Division Nuclear Physics Section of the Russian Academy of Sciences, 1-5 April 2024, Dubna, Russia, accepted for publication in Phys.Part.Nucl. 56 (2025)