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Register a new userDiquark and nucleons under strong magnetic fields in the NJL model
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We study the description of nucleons and diquarks in the presence of a uniform strong magnetic field within the framework of the two-flavor Nambu-Jona--Lasinio (NJL) model. Diquarks are constructed through the resummation of quark loop chains using the random phase approximation, while nucleons are treated as bound quark-diquark states described by a relativistic Fadeev equation, using the static approximation for quark exchange interactions. For charged particles, analytical calculations are performed using the Ritus eigenfunction method, which properly takes into account the breakdown of translation invariance that arises from the presence of Schwinger phases. Within this scheme, for definite model parametrizations we obtain numerical predictions for diquark and nucleon masses, which are compared with Chiral Perturbation Theory and Lattice QCD results. In addition, numerical estimations for nucleon magnetic moments are obtained.
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The behavior of charged pion masses in the presence of a static uniform magnetic field is studied in the framework of the two-flavor NJL model, using a magnetic field-independent regularization scheme. Analytical calculations are carried out employing the Ritus eigenfunction method, which allows us to properly take into account the presence of Schwinger phases in the quark propagators. Numerical results are obtained for definite model parameters, comparing the predictions of the model with present lattice QCD results.
In the framework of the Nambu--Jona-Lasino (NJL) model, we study the effect of an intense external uniform magnetic field on neutral and charged pion masses and decay form factors. In particular, the treatment of charged pions is carried out on the basis of the Ritus eigenfunction approach to magnetized relativistic systems. Our analysis shows that in the presence of the magnetic field three and four nonvanishing pion-to-vacuum hadronic form factors can be obtained for the case of the neutral and charged pions, respectively. As expected, it is seen that for nonzero magnetic field the $pi^0$ meson can still be treated as a pseudo Nambu-Goldstone boson, and consequently the corresponding form factors are shown to satisfy various chiral relations. For definite parametrizations of the model, numerical results for $pi^0$ and $pi^pm$ masses and decay constants are obtained and compared with previous calculations given in the literature.
The behavior of charged and neutral pion masses in the presence of a static uniform magnetic field is studied in the framework of the two-flavor Nambu-Jona-Lasinio (NJL) model. Analytical calculations are carried out employing the Ritus eigenfunction method. Numerical results are obtained for definite model parameters, comparing the predictions of the model with present lattice QCD (LQCD) results.
In this thesis is studied three of the fundamental properties of clusters of matter made of quarks u, d and s called strangelets: the energy per baryon, the radius and the electric charge, all in the presence of intense magnetic fields and finite temperature. Two cases will take our attention: unpaired phase strangelets, where there is no restriction to the number of flavors of quarks, and a particular case of the color superconducting phase, where exists a restriction to the quark numbers and an additional energy gap. We study the stability of strangelets, measured by the energy per baryon, to compare later with that of the 56Fe : the most stable isotope known in nature. We employ the Liquid Drop formalism of the Bag Model MIT to describe the interaction between quarks. We conclude that the field effects tend to decrease the energy per baryon of strangelets and temperature produces the opposite effect. It is also shown that strangelets in the color superconducting phase are more stable than those in the unpaired phase for an energy gap of about 100MeV. The radius of strangelets shows an analogous behavior with the baryon number, as that of the nuclei, and shows small variations with the magnetic field and temperature. It is obtained that the presence of magnetic fields modify the values of the electric charge regarding the non-magnetized case, being these higher (lower) for strangelets in the unpaired phase (superconducting).
We present a path-integral hadronization for doubly heavy baryons. The two heavy quarks in the baryon are approximated as a scalar or axial-vector diquark described by a heavy diquark effective theory. The gluon dynamics are represented by a NJL-Model interaction for the heavy diquarks and light quarks, which leads to an effective action of the baryon fields after the quark and diquark fields are integrated out. This effective action for doubly heavy baryon includes the electromagnetic and electroweak interactions, as well as the interaction with light mesons. We also verify the Ward-Takahashi identity at the baryon level, obtain the Isgur-Wise function for weak transitions, and calculate the strong coupling constant of the doubly heavy baryon and pion. Numerical studies are also performed.
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