Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDilepton production from magnetized quark matter with an anomalous magnetic moment of the quarks using a three-flavor PNJL model
82
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Dilepton production from hot, dense and magnetized quark matter is studied using the three-flavor Polyakov loop extended Nambu--Jona-Lasinio (PNJL) model in which the anomalous magnetic moment (AMM) of the quarks is also taken into consideration. This is done by first evaluating the thermo-magnetic spectral function of the vector current correlator employing the real time formalism of finite temperature field theory and the Schwinger proper time formalism. The constituent quark mass which goes as an input in the expression of the dilepton production rate (DPR), has been calculated using the three-flavor PNJL model employing Pauli-Villiars (PV) regularization. The obtained constituent quark mass being strongly dependent on the temperature, density, magnetic field and AMM of the quarks, captures the effect of `strong interactions specifically around the (pseudo) chiral and confinement-deconfinement phase transition regions. The analytic structure of the spectral function in the complex energy plane has been analyzed in detail and a non-trivial Landau cut is found in the physical kinematic domains resulting from the scattering of the Landau quantized quark/antiquark with the photon which is purely a finite magnetic field effect. Due to the emergence of the Landau cut along with the usual unitary cut, the DPR is found to be largely enhanced in the low invariant mass region. Owing to the magnetic field and AMM dependence of the thresholds of these cuts, we find that the kinematically forbidden gap between the Unitary and Landau cuts vanishes at sufficiently high temperature, density and magnetic field leading to the generation of a continuous spectrum of dilepton emission over the whole invariant mass region. In order to see the effects of strangeness and confinement-deconfinement, the rates are compared with the three-flavor NJL and the two-flavor NJL and PNJL models.
rate research
Read More
Dilepton production rate (DPR) from hot and dense quark matter is studied in the presence of an arbitrary external magnetic field using the 2-flavour Nambu--Jona-Lasinio (NJL) model. The anomalous magnetic moment (AMM) of the quarks is taken into consideration while calculating the constituent quark mass as well as the DPR from the thermo-magnetic medium. An infinite number of quark Landau levels is incorporated so that no approximations are made on the strength of the background magnetic field. The analytic structure of the two point vector current correlation function in the complex energy plane reveals that, in addition to the usual Unitary cut, a non-trival Landau cut appears in the physical kinematic domains solely due to the external magnetic field. Moreover, these kinematic domains of the Unitary and Landau cuts are found to be significantly modified due to the AMM of the quarks. With finite AMM of the quarks, for certain values of the external magnetic field, the kinematically forbidden gap between the Unitary and Landau cuts are shown to vanish leading to the generation of a continuous spectrum of dilepton emission over the whole invariant mass region not observed earlier.
The effective photon-quark-antiquark ($gamma q overline{q}$) vertex function is evaluated at finite temperature in the presence of an arbitrary external magnetic field using the two-flavor gauged Nambu--Jona-Lasinio (NJL) model in the mean field approximation. The lowest order diagram contributing to the magnetic form factor and the anomalous magnetic moment (AMM) of the quarks is calculated at finite temperature and external magnetic field using the imaginary time formalism of finite temperature field theory and the Schwinger proper time formalism. The Schwinger propagator including all the Landau levels with non-zero AMM of the dressed quarks is considered while calculating the loop diagram. Using sharp as well as smooth three momentum cutoff, we regularize the UV divergences arising from the vertex function and the parameters of our model are chosen to reproduce the well known phenomenological quantities at zero temperature and zero magnetic field, such as pion-decay constant ($f_pi$), vacuum quark condensate, vacuum pion mass ($m_pi$) as well as the magnetic moments of proton and neutron. We then study the temperature and magnetic field dependence of the AMM and constituent mass of the quark. We found that, the AMM as well as the constituent quark mass are large at the chiral symmetry broken phase in the low temperature region. Around the pseudo-chiral phase transition they decrease rapidly and at high temperatures both of them approach vanishingly small values in the symmetry restored phase.
We extend our previous study of the quark-hadron phase transition at finite temperatures with zero net baryon density by two flavor Nambu-Jona-Lasinio model with Polyakov loop to the three flavor case in a scheme which incorporates flavor nonet pseudo scalar and scalar mesonic correlations on equal footing. The role of the axial U(1) breaking Kobayashi-Maskawa-t Hooft interaction on the low-lying thermal excitations is examined. At low temperatures, only mesonic correlations, mainly due to low mass mesonic collective excitations, pions and kaons, dominate the pressure while thermal excitations of quarks are suppressed by the Polyakov loop. As temperature increases, kaons and pions melt into the continuum of quark and anti-quark excitations successively so that hadronic phase changes continuously to the quark phase where quark excitations dominate pressure together with gluon pressure coming from the effective potential for the Polyakov loop. Since we introduce mesons as not elementary fields but auxiliary fields made from quarks, we can describe the phase transition between hadronic phase and quark phase in a unified fashion.
We study quark-hadron phase transition at finite temperature with zero net baryon density by the Nambu-Jona-Lasinio model for interacting quarks in uniform background temporal color gauge fields. At low temperatures, unphysical thermal quark-antiquark excitations which would appear in the mean field approximation, are eliminated by en- forcing vanishing expectation value of the Polyakov-loop of the background gauge field, while at high temperatures this expectation value is taken as unity allowing thermal excitations of free quarks and antiquarks. Mesonic excitations in the low temperature phase appear in the correlation energy as contributions of collective excitations. We describe them in terms of thermal fluctuations of auxiliary fields in one-loop (Gaus- sian) approximation, where pions appear as Nambu-Goldstone modes associated with dynamical symmetry breaking of the chiral symmetry in the limit of vanishing bare quark masses. We show that at low temperatures the equations of state reduces to that of free meson gas with small corrections arising from the composite nature of mesons. At high temperatures, all these collective mesonic excitations melt into continuum of quark anti-quark excitations and mesonic correlations gives only small contributions the pressure of the system.
We have computed the hard dilepton production rate from a weakly magnetized deconfined QCD medium within one-loop photon self-energy by considering one hard and one thermomagnetic resummed quark propagator in the loop. In the presence of the magnetic field, the resummed propagator leads to four quasiparticle modes. The production of hard dileptons consists of rates when all four quasiquarks originating from the poles of the propagator individually annihilate with a hard quark coming from a bare propagator in the loop. Besides these, there are also contributions from a mixture of pole and Landau cut part. In weak field approximation, the magnetic field appears as a perturbative correction to the thermal contribution. Since the calculation is very involved, for a first effort as well as for simplicity, we obtained the rate up to first order in the magnetic field, i.e., ${cal O}[(eB)]$, which causes a marginal improvement over that in the absence of magnetic field.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
