Constraining free parameters of a color superconducting nonlocal Nambu–Jona-Lasinio model using Bayesian analysis of neutron stars mass and radius measurements

We provide a systematic study of hybrid neutron star equations state (EOS) consisting relativistic density functional for the hadronic phase and covariant nonlocal Nambu--Jona-Lasinio (nlNJL) model to describe color superconducting quark matter phase. Changing values two free parameters, dimensionless vector diquark coupling strengths ${\ensuremath{\eta}}_{V}$ ${\ensuremath{\eta}}_{D}$ results in set EOS with varying stiffness deconfinement onset. The favorable parameters are obtained from Bayesian analysis which multimessenger constraint on radius at $14{M}_{\ensuremath{\bigodot}}$ combined mass-radius PSR $\mathrm{J}0740+6620$ NICER experiment used as constraints. Additionally, transition deconfined is constrained occur above nuclear saturation density. Hybrid stars modeled these compatible highest known mass star, $\mathrm{J}0740+6620$. Three new observations interesting phenomenology reported: (i) we show that constant sound speed (CSS) provides an excellent fit nlNJL implies squared high densities be about 0.5 optimized parameters; (ii) give simple form mapping between parameter spaces models valid whole range relevant chemical potentials (iii) observe special point property based CSS generalizes lines points when varied instead one. A lower limit maximum function strength obtained.