Neutrino emissivities and bulk viscosity in neutral two-flavor quark matter

We study thermodynamic and transport properties for the isotropic color-spin-locking (iso-CSL) phase of two-flavor superconducting quark matter under compact star constraints within a NJL-type chiral quark model. Chiral symmetry breaking and the phase transition to superconducting quark matter leads to a density dependent change of quark masses, chemical potentials and diquark gap. A self-consistent treatment of these physical quantities influences on the microscopic calculations of transport properties. We present results for the iso-CSL direct URCA emissivities and bulk viscosities, which fulfill the constraints on quark matter derived from cooling and rotational evolution of compact stars. We compare our results with the phenomenologically successful, but yet heuristic 2SC+X phase. We show that the microscopically founded iso-CSL phase can replace the purely phenomenological 2SC+X phase in modern simulations of the cooling evolution for compact stars with color superconducting quark matter interior.Comment: 15 pages, 6 figures, references added, text improve

Lepton Phenomenology of Stueckelberg Portal to Dark Sector

We propose an extension of the Standard Model (SM) with a $U_{A'}(1)$ gauge invariant Dark Sector connected to the SM via a new portal arising in the framework of dark photon $A'$ mass generation via Stueckelberg mechanism. This mechanism implies the existence of a scalar field $\sigma$, which is shift-transformed under this group and resembles an axion-like particle (ALP) widely addressed in the literature in different contexts. The effective dim=5 operators constructed of the covariant derivative of the $\sigma$ field generate flavor non-diagonal renormalizable couplings of both $\sigma$ and $A'$ to the SM fermions $\psi$. Contrary to the conventional kinetic mixing portal, in our scenario flavor diagonal $A'$-$\psi$ couplings are not proportional to the fermion charges. These features drastically change the phenomenology of dark photon $A'$ relaxing or avoiding some previously established experimental constraints. We focus on the phenomenology of the described scenario of the Stueckelberg portal in the lepton sector and analyze the contribution of the dark sector fields $A'$ and $\sigma$ to the anomalous magnetic moment of muon $(g-2)_{\mu}$, Lepton Flavor Violating decays $l_{i}\to l_{k}\gamma$ and $\mu-e$ conversion in nuclei. We obtain limits on the model parameters from the existing experimental data on the corresponding observables.Comment: 15 pages, 8 figure