Properties of strange quark matter and strange quark stars

A Polyakov chiral $$\text {SU(3)}$$ SU(3) quark mean-field (PCQMF) model is applied to study the properties of strange quark matter (SQM) and strange quark star (SQS) in $$\beta $$ β -equilibrium. The effect of increasing the strength of vector interactions on the effective constituent quark mass, particle fractions, and the thermodynamical properties such as pressure, energy density, and the speed of sound is investigated. We investigate the above properties for the SQM relevant for various stages of star evolution, i.e., considering with/without trapped neutrinos and zero/finite entropy. The finite lepton fraction and the entropy of the medium is observed to cause the stiffness in the equation of state (EoS). Finally, we calculate the mass-radius relation and the dimensionless tidal deformability within the present model calculations and compare the results to the recent studies.

A Multiquark Approach to Excited Hadrons and Regge Trajectories

We propose a novel approach to construction of hadron spectroscopy. The case of light nonstrange mesons is considered. By assumption, all such mesons above 1 GeV appear due to creation of constituent quark-antiquark pairs inside π or ρ(ω) mesons. These spin-singlet or triplet pairs dictate the quantum numbers of formed resonance. The resulting classification of light mesons turns out to be in a better agreement with the experimental observations than the standard quark model classification. It is argued that the total energy of quark components should be proportional to the hadron mass squared rather than the linear mass. As a byproduct a certain relation expressing the constituent quark mass via the gluon and quark condensate is put forward. We show that our approach leads to an effective mass counting scheme for meson spectrum and results in the linear Regge and radial Regge trajectories by construction. An experimental observation of these trajectories might thus serve as evidence not for string but for multiquark structure of highly excited hadrons.

NJL INTERACTION DERIVED FROM QCD

We apply Bogolubov approach to QCD with two light quarks to demonstrate a spontaneous generation of an effective interaction, leading to the Nambu–Jona-Lasinio model. The resulting theory contains two parameters: average low-energy value of αs and current light quark mass m0. All other low-energy parameters: the pion decay constant, mass of the π-meson, mass of the σ-meson and its width, the constituent quark mass, and the quark condensate are expressed in terms of the two input parameters in satisfactory correspondence to experimental data and chiral phenomenology. For example, in the approximation being used we have for αs = 0.67 and m0 = 20 MeV : fπ = 93 MeV , mπ = 135 MeV , mσ = 492 MeV , Γσ = 574 MeV , mq = 295 MeV , [Formula: see text].

CP CONSERVED NONLEPTONIC K → πππ DECAYS IN THE CHIRAL QUARK MODEL

The CP conserved nonleptonic K → πππ decays are discussed within the chiral quark model, including chiral perturbation theory corrections. For the chiral loop correction, they are presented in a way to be more manageable and easier for use. Furthermore a new identity for the imaginary part of the chiral loop corrections is derived. All amplitudes are parametrized in terms of quark and gluon condensate and the constituent quark mass. The same values for these parameters that can be obtained by a fit of the ΔI = 1/2 rule in K → 2π give a reasonably good fit in the K → 3π case. We compare with the work of other groups.

ON THE COMPLEXION OF PSEUDOSCALAR MESONS

A strongly momentum-dependent dressed-quark mass function is basic to QCD. It is central to the appearance of a constituent-quark mass-scale and an existential prerequisite for Goldstone modes. Dyson-Schwinger equation (DSEs) studies have long emphasised this importance, and have proved that QCD's Goldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken, while the decay constants of their radial excitations vanish. Such features are readily illustrated using a rainbow-ladder truncation of the DSEs. In this connection we find (in GeV): fηc(1S)=0.233, mηc(2S)=3.42; and support for interpreting η(1295), η(1470) as the first radial excitations of η(548), η′(958), respectively, and K(1460) as the first radial excitation of the kaon. Moreover, such radial excitations have electromagnetic diameters greater than 2 fm. This exceeds the spatial length of lattices used typically in contemporary lattice-QCD.