Sean Tulin

New GeV-scale dark forces coupling predominantly to quarks offer novel signatures that can be produced directly and searched for at high-luminosity colliders. We compute the photon-proton and electron-proton cross sections for producing a GeV-scale gauge boson arising from a U (1) B gauge symmetry. Our calculation relies on vector meson dominance and a phenomenological model for diffractive scattering used for vector-meson photoproduction. The parameters of our phenomenological model are fixed by performing a Markov Chain Monte Carlo fit to existing exclusive photoproduction data for ω and ϕ mesons. Our approach can be generalized to other GeV-scale dark gauge forces.

Decays of the neutral and long-lived η and η′ mesons provide a unique, flavor-conserving laboratory to test low-energy Quantum Chromodynamics and search for new physics beyond the Standard Model. They have drawn world-wide attention in recent years and have inspired broad experimental programs in different high-intensity-frontier centers. New experimental data will offer critical inputs to precisely determine the light quark mass ratios, η–η′ mixing parameters, and hadronic contributions to the anomalous magnetic moment of the muon. At the same time, it will provide a sensitive probe to test potential new physics. This includes searches for hidden photons, light Higgs scalars, and axion-like particles that are complementary to worldwide efforts to detect new light particles below the GeV mass scale, as well as tests of discrete symmetry violation. In this review, we give an update on theoretical …

We probe the self-interactions of dark matter with relaxed galaxy groups and clusters using observational data from strong and weak lensing and stellar kinematics. Our analysis uses the Jeans formalism and considers a wider range of systematic effects than in previous work, including adiabatic contraction and stellar anisotropy, to robustly constrain the self-interaction cross section. For both groups and clusters, our results show a mild preference for a nonzero cross section compared with cold collisionless dark matter. Our groups result, σ/m= 0.5±0.2 cm 2/g, places the first constraint on self-interacting dark matter (SIDM) at an intermediate scale M 200∼ 10 14 M⊙ between galaxies and massive clusters. For massive clusters with M 200∼ 10 15 M⊙, our result is σ/m= 0.19±0.09 cm 2/g, with an upper limit of σ/m< 0.35 cm 2/g (95% CL). Thus, our results disfavor a velocity-independent cross section of order 1 cm 2/g …

Many particle physics models for dark matter self-interactions—motivated to address long-standing challenges to the collisionless cold dark matter paradigm—fall within the semiclassical regime, with interaction potentials that are long range compared to the de Broglie wavelength for dark matter particles. In this work, we present a quantum-mechanical derivation and new analytic formulas for the semiclassical momentum transfer and viscosity cross sections for self-interactions mediated by a Yukawa potential. Our results include the leading quantum corrections beyond the classical limit and allow for both distinguishable and identical dark matter particles. Our formulas supersede the well-known formulas for the momentum transfer cross section obtained from the classical scattering problem, which are often used in phenomenological studies of self-interacting dark matter. Together with previous approximation …

We present an overview of the opportunities for η, η meson factories to discover new light hidden particles beyond the Standard Model (SM). This is not part the traditional motivation for precision studies of the η, η sector, which historically has been framed in the context of fundamental symmetry tests in and beyond the SM. The latter includes a testing ground for the dynamics of low-energy QCD (guided by chiral symmetries), as well as probes of discrete symmetries C, P, and CP from physics beyond the SM [1, 2]. On top of this, there is a potentially rich physics program to discover new hidden particles at the MeV–GeV mass scale [2, 3]. Possible states include spin-zero or spinone bosons mediating new interactions beyond the Standard Model that can be produced on-shell in meson decays if kinematically allowed [4–6]. From a theoretical standpoint, there is strong motivation for such states in connection with dark …