17 research outputs found
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 and 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
Inverse magnetic catalysis in field theory and gauge-gravity duality
We investigate the surface of the chiral phase transition in the
three-dimensional parameter space of temperature, baryon chemical potential and
magnetic field in two different approaches, the field-theoretical
Nambu-Jona-Lasinio (NJL) model and the holographic Sakai-Sugimoto model. The
latter is a top-down approach to a gravity dual of QCD with an asymptotically
large number of colors and becomes, in a certain limit, dual to an NJL-like
model. Our main observation is that, at nonzero chemical potential, a magnetic
field can restore chiral symmetry, in apparent contrast to the phenomenon of
magnetic catalysis. This "inverse magnetic catalysis" occurs in the
Sakai-Sugimoto model and, for sufficiently large coupling, in the NJL model and
is related to the physics of the lowest Landau level. While in most parts our
discussion is a pedagogical review of previously published results, we include
new analytical results for the NJL approach and a thorough comparison of
inverse magnetic catalysis in the two approaches.Comment: 37 pages, 11 figures, to appear in Lect. Notes Phys. "Strongly
interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K.
Landsteiner, A. Schmitt, H.-U. Ye
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