2019/10/21 by Gaoqing Cao · 2 citations
Physics and Astronomy · Engineering · #High-Energy Particle Collisions Research #Quantum Chromodynamics and Particle Interactions #Superconducting Materials and Applications
paper · doi:10.1103/physrevd.100.074024
By comparing the two- and three-flavor Nambu--Jona-Lasinio (NJL) models, we demonstrate that the naively expected vacuum superconductivity (VSC) in constant magnetic field B=B\stackrel^z is disfavored due to the splitting magnetic catalysis effect (MCE) to chiral condensates with different quark flavors. Based on the simple two-flavor NJL model, we illuminate, in the lowest Landau-level approximation, the similar origins of \ensuremathπ0 and \ensuremathρ1+ (\ensuremathρ+ meson with spin Sz=1) mass reductions with smaller B and their different features at larger B. With the full Landau levels, the two-flavor NJL model is found to be invalid to study the magnetic field effect on the \ensuremathρ1+ meson with physical vacuum mass 775 MeV. Then, restricted to the \ensuremathρ meson mass below the two-quark threshold in vacuum, that is, m_\ensuremathρv<2mqv, it is found that \ensuremathπ0 mass decreases and then increases with B slowly, and the \ensuremathρ1+ mass vanishing point is delayed to larger B compared to the point particle result. In the more realistic three-flavor NJL model, all the quark masses split in strong magnetic field as a combinatorial result of their different current masses and electric charges. By choosing a vacuum mass closer to the physical one, the \ensuremathρ1+ meson mass is found to be consistent with the lattice QCD results semiquantitatively in the smaller B region but increase in the larger B region. These features are mainly outcomes of the interplay between the Sz\ensuremath-B coupling effect and splitting MCE to the composite u and d quarks, which definitely disfavors VSC when the latter dominates. Furthermore, mesonic flavor mixing is modified by B among the neutral pseudoscalars, \ensuremathπ0, \ensuremathη0 and \ensuremathη8, which is very important to suppress the mass enhancement of the effective mass eigenstates at large B.