In the framework of two-flavor extended linear sigma model with mixing between scalar quarkonium and tetraquark, we investigate the role of the tetraquark in the chiral phase transition. We explore various scenarios depending on the value of various parameters in our model. The physical mass spectrum of mesons put a tight constraint on the parameter set of our model. We find a sufficiently strong cubic self interaction of the tetraquark field can drive the chiral phase transition to first order even at zero quark chemical potential. Weak or absence of the cubic self interaction term of the tetraquark field make the chiral phase transition crossover at vanishing density.
We consider a system composed of two identical light quarks ($qq$) and two identical antiquarks ($bar Qbar Q$) that can be linked either as two mesons or as a tetraquark, incorporating quantum correlations between identical particles and an effective many-body potential between particles. We perform a 3-D Monte Carlo simulation of the system, considering the configurations allowed to form: i) Only two mesons, ii) Only tetraquark and iii) two mesons and tetraquark . We characterize each case and determine whether it is energetically more favorable to form a tetraquark or two mesons, as a function of the interparticle separation distance which, for a fixed number of particles, can be identified as a particle density. We determine how the two mesons, which dominate the low density regime, mixes with a tetraquark state as the density increases. Properties like the mean square radius and the two-particle correlation function are found to reflect such transition, and we provide a parameterization of the diquark correlation function in the isolated case. We track the dynamical flipping among configurations to determine the recombination probability, exhibiting the importance of the tetraquark state. We analize the four-body potential evolution and show that its linear behavior is preserved, although the slope can reflect the presence of a mixed state. Results are shown for several light-quarks to heavy-antiquarks mass ratios whenever they are found to be relevant.
We study the dressing of four-quark interaction by the ring diagram in an effective chiral quark model. Implementing such an in-medium coupling naturally reduces the chiral transition temperature in a class of chiral models, and is capable of generating the inverse magnetic catalysis at finite temperatures. We also demonstrate the important role of confining forces, via the Polyakov loop, in a positive feedback mechanism which reinforces the inverse magnetic catalysis.
In this article, we study the masses and pole residues of the pseudoscalar-diquark-pseudoscalar-antidiquark type and vector-diquark-vector-antidiquark type scalar hidden-charm $cubar{c}bar{d}$ ($cubar{c}bar{s}$) tetraquark states with QCD sum rules by taking into account the contributions of the vacuum condensates up to dimension-10 in the operator product expansion. The predicted masses can be confronted with the experimental data in the future. Possible decays of those tetraquark states are also discussed.
We extend the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model by introducing an effective four-quark vertex depending on Polyakov loop. The effective vertex generates entanglement interactions between Polyakov loop and chiral condensate. The new model is consistent with lattice QCD data at imaginary quark-number chemical potential and real and imaginary isospin chemical potentials, particularly on strong correlation between the chiral and deconfinement transitions and also on the quark-mass dependence of the order of the Roberge-Weiss endpoint predicted by lattice QCD very lately. We investigate an influence of the entanglement interactions on a location of the tricritical point at real isospin chemical potential and a location of the critical endpoint at real quark-number chemical potential.
The Abelian decomposition of QCD which decomposes the gluons to the color neutral binding gluons (the neurons) and the colored valence gluons (the chromons) gauge independently naturally generalizes the quark model to the quark and chromon model which could play the central role in hadron spectroscopy. We discuss the color reflection symmetry, the fundamental symmetry of the quark and chromon model, and explain how it describes the glueballs and the glueball-quarkonium mixing in QCD. We present the numerical analysis of glueball-quarkonium mixing in $0^{++}$, $2^{++}$, and $0^{-+}$ sectors below 2 GeV, and show that in the $0^{++}$ sector $f_0(500)$ and $f_0(1500)$, in the $2^{++}$ sector $f_2(1950)$, and in the $0^{-+}$ sector $eta(1405)$ and $eta(1475)$ could be identified as predominantly the glueball states. We discuss the physical implications of our result.