Dark Photon Searches via Higgs Boson Production at the LHC and Beyond

Abstract

Many scenarios beyond the standard model, aiming to solve long-standing cosmological and particle physics problems, suggest that dark matter might experience long-distance interactions mediated by an unbroken dark U(1) gauge symmetry, hence foreseeing the existence of a massless dark photon. Contrary to the massive dark photon, a massless dark photon can only couple to the standard model sector by means of effective higher dimensional operators. Massless dark photon production at colliders will then in general be suppressed at low energy by a UV energy scale, which is of the order of the masses of portal (messenger) fields connecting the dark and the observable sectors. A violation of this expectation is provided by dark photon production mediated by the Higgs boson, thanks to the non-decoupling Higgs properties. Higgs boson production at colliders, followed by the Higgs decay into a photon and a dark photon, provides then a very promising production mechanism for the dark photon discovery, being insensitive in particular regimes to the UV scale of the new physics. This decay channel gives rise to a peculiar signature characterized by a monochromatic photon with energy half the Higgs mass (in the Higgs rest frame) plus missing energy. We show how such resonant photon-plus-missing-energy signature can uniquely be connected to a dark photon production. Higgs boson production and decay into a photon and a dark photon as a source of dark photons is reviewed at the Large Hadron Collider, in light of the present bounds on the corresponding signature by the CMS and ATLAS collaborations. Perspectives for the dark photon production in Higgs-mediated processes at future e+e− colliders are also discussed.

Fermion Proca Stars: Vector-Dark-Matter-Admixed Neutron Stars

“…These similarities also hint towards a possibility to also use the effective EOS by Colpi et al [103] for (fermion) Proca stars. We note, however, that great care is needed since Proca stars do not exist in the limit of large self-interactions (see the analytical bound on vector field amplitude Equation (24)). The similarities between FBSs and FPSs might also be useful for numerical applications.…”

“…The right panel of Figure 2 shows an FPS in the zeroth mode with a vector boson mass of m = 1.34 • 10 −10 eV and a self-interaction strength of Λ int = 50. The maximal amplitude is roughly E 0,crit ≈ 0.0282 due to the analytical bound on E 0 ; see Equation (24). The limited field amplitude strongly limits the possible effect on the fermionic component and thus on the fermionic radius, especially in the limit of large Λ int .…”

“…There exist numerous candidates for DM particles. A possible DM candidate is an additional bosonic field (scalar field or vector field), as was studied in [22][23][24][25][26].…”

“…This process could allow for NSs with a large range of possible DM fractions. The DM particles most interesting for FBSs are generally (self-interacting) ultralight DM particles, weakly interacting massive particles, dark photons [24,25] (as a candidate for vector DM), and axions [15,35,[62][63][64][65][66][67][68][69][70].…”

“…The pressure has been re-scaled by a factor of 3 for convenience. Due to the analytical bound on E 0 Equation(24), the maximal amplitude is roughly E 0,crit ≈ 0.0282. The limited field amplitude strongly limits the effect on the fermionic component.…”