Constraints on the kinetic mixing parameter ε² for the light dark photons from dilepton production in heavy-ion collisions in the few-GeV energy range

  • The vector U bosons, or so-called “dark photons,” are one of the possible candidates for the dark matter mediators. They are supposed to interact with the standard matter via a “vector portal” due to the Uð1Þ − Uð1Þ0 symmetry group mixing which might make them visible in particle and heavy-ion experiments. While there is no confirmed observation of dark photons, the detailed analysis of different experimental data allows to estimate the upper limit for the kinetic mixing parameter ϵ2 depending on the mass MU of U bosons which is also unknown. In this study we present theoretical constraints on the upper limit of ϵ2ðMUÞ in the mass range MU ≤ 0.6 GeV from the comparison of the calculated dilepton spectra with the experimental data from the HADES collaboration at SIS18 energies where the dark photons are not observed. Our analysis is based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which reproduces well the measured dilepton spectra in p þ p, p þ A and A þ A collisions. Additionally to the different dilepton channels originating from interactions and decays of ordinary matter particles (mesons and baryons), we incorporate the decay of hypothetical U bosons to dileptons, U → eþe−, where the U bosons themselves are produced by the Dalitz decay of pions π0 → γU, η mesons η → γU and Delta resonances Δ → NU. Our analysis can help to estimate the requested accuracy for future experimental searches of “light” dark photons by dilepton experiments.

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Author:Ida SchmidtORCiD, Elena BratkovskayaORCiDGND, Malgorzata Gumberidze, Romain HolzmannORCiD
Parent Title (English):Physical Review D
Publisher:American Physical Society
Place of publication:Woodbury, NY
Document Type:Article
Date of Publication (online):2021/07/06
Date of first Publication:2021/07/06
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2022/10/26
Issue:1, art. 015008
Page Number:11
First Page:1
Last Page:11
Institutes:Physik / Physik
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Licence (German):License LogoCreative Commons - Namensnennung 4.0