Mess Spectra And Decay Of Mesons Under Strong External Magnetic Field

Over the years,studies on the nature and state of strong acting substances under extreme conditions has attracted much attention,where extreme conditions include high temperatures and finite baryon chemical potentials,as well as strong magnetic fields.In this paper we will discuss the effects of finite baryon density and magnetic fields on strong interacting matter.Magnetic field changes are closely related to high-energy nuclear collisions,dense stars and cosmic phase transitions.The maximum magnetic field observed in nature is about 1012--1013 Gauss in pulsars;the maximum magnetic field on the surface of some magnetospheric stars is around 1014--1015 Gauss,and its internal field is estimated to be 1018--1020 Gauss[1].In the early stage of the RHIC[2,3]non-central heavy ion collisions,there is also an evidence of a very strong and transient magnetic fields.Depending on the energy of the collision and impact parameters,magnetic field produced in RHIC is eB which corresponds to 0.03 GeV2,and eB 15m2?/0.3GeV2[4]in LHC.On the other hand,produced in high energy heavy-ion collisions,quark-gluon plasma went through many stages in the process of evolution,a large number of hardrons including ? produce in the final state,until freeze-out in the end[6].Therefore,the existence of the background magnetic field generated in the heavy ion experiment may affect the properties of the early "charged quarks" in the collision.Although this strong magnetic field lasts a very short time and its decay rate is very fast[3,4],it may affect the properties of the hadrons formed by these magnetized" quarks.Even the properties of neutral mesons may be affected by external magnetic fields produced in the early stage of heavy ion collisions.This paper is conducted based on the two flavor NJL model,and the work is mainly divided into two parts:1.With the calculation of self energy and decay triangle diagram in the case of finite temperature and density,we can calculate the coupling constant and triangle diagram factor according to the definition,then we have meson mass spectra and further obtain the ?? ??decay width.We found that in the case of finite density,the coupling constant first decreases and then tends to be stable,and the decay width varies in different ranges under different densities.2.we calculated the energy gap equation in the magnetic field through the random phase approximation.And we tried to use Ritus method to calculate the decay triangle diagram and self energy in the magnetic field(calculated by substituting quark flavor number),therefore we worked out the decay width,coupling constant and so on.Our result shows that as quarks of neutral mesons are magnetized at magnetic field,?' s mass grows and ?'s mass slowly drops,and coupling constant is significantly strengthened compared with which without magnetic field.