Constraining Hadron-quark Phase Transition Parameters within the Quark-mean-field Model Using Multimessenger Observations of Neutron Stars

We extend the quark mean-field (QMF) model for nuclear matter and study the possible presence of quark matter inside the cores of neutron stars. A sharp first-order hadron-quark phase transition is implemented combining the QMF for the hadronic phase with "constant-speed-of-sound" parameterization for the high-density quark phase. The interplay of the nuclear symmetry energy slope parameter, L, and the dimensionless phase transition parameters (the transition density n_trans/n₀, the transition strength Δɛ/ɛ_trans, and the sound speed squared in quark matter ${c}_{\mathrm{QM}}^{2}$ ) are then systematically explored for the hybrid star properties, especially the maximum mass M_max and the radius and the tidal deformability of a typical 1.4 M_⊙ star. We show the strong correlation between the symmetry energy slope L and the typical stellar radius R_1.4, similar to that previously found for neutron stars without a phase transition. With the inclusion of phase transition, we obtain robust limits on the maximum mass (M_max < 3.6 M_⊙) and the radius of 1.4 M_⊙ stars (R_1.4 ≳ 9.6 km), and we find that a phase transition that is too weak (Δɛ/ɛ_trans ≲ 0.2) taking place at low densities ≲1.3-1.5 n₀ is strongly disfavored. We also demonstrate that future measurements of the radius and tidal deformability of ∼1.4 M_⊙ stars, as well as the mass measurement of very massive pulsars, can help reveal the presence and amount of quark matter in compact objects.