Self-interacting dark matter and muon (g − 2) in a gauged $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$ model

Abstract

We construct a self-interacting dark matter model that could simultaneously explain the observed muon anomalous magnetic moment. It is based on a gauged U(1) Lµ−Lτ extension of the standard model, where we introduce a vector-like pair of fermions as the dark matter candidate and a new Higgs boson to break the symmetry. The new gauge boson has a sizable contribution to muon (g − 2), while being consistent with other experimental constraints. The U(1) Lµ−Lτ Higgs boson acts as a light force carrier, mediating dark matter self-interactions with a velocity-dependent cross section. It is large enough in galaxies to thermalize the inner halo and explain the diverse rotation curves and diminishes towards galaxy clusters. Since the light mediator dominantly decays to the U(1) Lµ−Lτ gauge boson and neutrinos, the astrophysical and cosmological constraints are weak. We study the thermal evolution of the model in the early Universe and derive a lower bound on the gauge boson mass.

Refined bounds on MeV-scale thermal dark sectors from BBN and the CMB

“…The bounds derived for BSM species that annihilate into electrons and neutrinos with different ratios are, for instance, relevant for scenarios involving a gauging of SM global symmetries such as U (1) Lµ−Lτ [32,142,143] or U (1) B−L [144,145]. Finally, these bounds also apply to asymmetric dark matter sectors interacting with SM species [146,147].…”

Search for muon-philic new light gauge boson at Belle II

“…A light X boson coupled to neutrinos can directly enhance the number of relativistic degree of freedom in the BBN era for m X ∼ < O(1) MeV. Even in the heavier case m X ∼ O(1−10) MeV, the presence of muon-philic X boson can affect the effective number of the light neutrino species N eff by providing additional energies to ν µ ,ν µ (and also ν τ ,ν τ in L µ − L τ case) from the decay process X → ν µ(τ )νµ(τ ) after all SM neutrinos are decoupled from SM thermal bath at T ν,dec 1.5 MeV [41][42][43]. The deviation of the effective neutrino number ∆N eff comes from the difference between the tempreature T of the thermal bath of (ν µ ,ν µ , ν τ ,ν τ , X) and the temperature T of the thermal bath of (ν e ,ν e , γ).…”

Dark matter interactions with muons in neutron stars

“…In a different region of parameter space, a heavy L µ − L τ [11] at 2σ (1σ), the cyan region ameliorates the Hubble H0 tension [48], and the yellow region can resolve the b → sµ + µ − anomaly [26] while satisfying Bs-Bs mixing constraints [49]. The other shaded regions are excluded by N eff [50,51], BaBar [52], CMS [53], LEP [23], and neutrino trident production in CCFR [22,54]. The dashed lines show the expected sensitivities of Belle-II [55], DUNE [56,57] and NA62 (in K → µ + inv) [58].…”