Two-flavor color superconductivity at finite temperature, chemical potential and in the presence of strong magnetic fields

Utilizing an extended two-flavor Nambu-Jona Lasinio (NJL) model, we review some of the effects of external magnetic fields on two-flavor color superconducting phase (2SC) at moderate baryon densities in the QCD phase diagram. The effective action of the extended NJL model consists of two mass gaps as functions of three intensive quantities, the temperature, the quark chemical potential and the external magnetic field. The nonzero values of the mass gaps, chiral and diquark condensates, induce spontaneous chiral and color symmetry breaking, respectively, and as a result two different phases of quark matter appear. We find the transition curves between these phases as well as the critical points in the QCD phase diagram in terms of the intensive quantities. Imposing a constant strong magnetic field on these two phases, we show that the mass gaps increase with the magnetic field and the symmetry breaking region in the QCD phase diagram expands even to the larger values of temperature and quark chemical potential. This phenomenon is a consequence of the magnetic catalysis of dynamical symmetry breaking, which is proven before

Properties of neutral mesons in a hot and magnetized quark matter

The properties of non-interacting $\sigma$ and $\pi^{0}$ mesons are studied at finite temperature, chemical potential and in the presence of a constant magnetic field. To do this, the energy dispersion relations of these particles, including nontrivial form factors, are derived using a derivative expansion of the effective action of a two-flavor, hot and magnetized Nambu--Jona-Lasinio (NJL) model up to second order. The temperature dependence of the pole and screening masses as well as the directional refraction indices of magnetized neutral mesons are explored for fixed magnetic fields and chemical potentials. It is shown that, because of the explicit breaking of the Lorentz invariance by the magnetic field, the refraction index and the screening mass of neutral mesons exhibit a certain anisotropy in the transverse and longitudinal directions with respect to the direction of the external magnetic field. In contrast to their longitudinal refraction indices, the transverse indices of the neutral mesons are larger than unity.Comment: V1: 26 pages, 15 figures; V2: Discussions improved, references added. Version accepted for publication in PR

Phase diagram of hot magnetized two-flavor color superconducting quark matter

A two-flavor color superconducting (2SC) Nambu--Jona-Lasinio (NJL) model is introduced at finite temperature T, chemical potential mu and in the presence of a constant magnetic field eB. The effect of (T,mu,eB) on the formation of chiral and color symmetry breaking condensates is studied. The complete phase portrait of the model in T-mu, mu-eB, and T-eB phase spaces for various fixed eB, T, and mu is explored. A threshold magnetic field eB_t~ 0.5 GeV^2 is found above which the dynamics of the system is solely dominated by the lowest Landau level (LLL) and the effects of T and mu are partly compensated by eB.Comment: V1: 29 pages, 15 figures, 3 tables. V2: Discussions improved. Version accepted for publication in PR

Exploring anomalous HZγ couplings in γ-proton collisions at the LHC

The HZγ coupling, which is highly sensitive to the new physics beyond the standard model, is studied through the process pp→pγp→pHX at the LHC. To this purpose, an effective Lagrangian, in a model independent approach, with dimension six operators is considered in this paper. New interaction terms regarding beyond the standard model physics include the Higgs boson anomalous vertices in both CP-even and CP-odd structures. A detailed numerical analysis is performed to scrutinize the accurate constraints on the effective HZγ couplings and to discuss how far the corresponding bounds can be improved. This is achieved by testing all the efficient Higgs decay channels and increasing the integrated luminosity at three different forward detector acceptance regions. The numerical results propose that the Higgs photoproduction at the LHC, as a complementary channel, has a great potential of exploring the HZγ couplings