Speaker
Description
We investigate a dark sector coupled to the Standard Model (SM) through a kinetically mixed dark photon
associated with a new
gauge symmetry. Kinetic mixing, parametrized by
, induces an effective coupling to the electromagnetic current, while the dark photon interacts with a stable dark matter (DM) particle
through a dark gauge coupling
, defining a four-dimensional parameter space
. Our analysis is based on the parton--hadron--string dynamics (PHSD) transport approach, extended to include dark photon production and decay into dileptons (
). In PHSD, dark photons are produced in high-energy collisions through Dalitz decays of light mesons (
), Delta-resonances (
), direct vector meson decays (
), kaon decays (
), and
annihilation. Building on previous PHSD benchmarks against dilepton data, we extract upper limits on
in both the visible regime (
), where
dominates, and the invisible regime (
), where
is kinematically open and suppresses the dilepton branching fraction. Cosmological and astrophysical constraints are incorporated in two
complementary ways. First, we compute the velocity-dependent self-interaction cross section
for Yukawa-mediated SIDM and confront it with bounds from dwarf galaxies, galaxy groups, and clusters. Second, we determine thermal relic target curves by computing the relic abundance and requiring
, consistent with \textit{Planck} measurements of the cosmic microwave background. Combining PHSD limits on
with relic density and self-interaction requirements, we exclude regions of the
plane for each DM realization (Dirac fermion, Majorana fermion, or complex scalar) and identify benchmark scenarios in which heavy-ion, cosmological, and astrophysical constraints are simultaneously satisfied.