Recently, the researchers in Institute of Modern Physics, Chinese Academy of Sciences (IMP) have investigated the nuclear collision in strong magnetic field. It is found that neutrons and protons can be separated from a nucleus in strong magnetic field and neutron-rich high density nuclear matter and low density proton collectivity matter can be formed during nucleus–nucleus collisions.

The condition of strong magnetic field may exist in the universe, such as white dwarfs, neutron stars, and accretion disks around black holes, and the maximum value of magnetic fields in the universe may reach 1020–1042 G. And with the rapid development of laser technology, obtaining strong magnetic field artificially in terrestrial laboratory also may be possible.

Based on a transport model coupled with the Lorentz force equation, scientists in IMP studied nucleus–nucleus collision in strong magnetic field. The separation of neutrons and protons while nucleus-nucleus collision in magnetic field causes the formation of high density neutron-rich matter with high asymmetry and relatively low density proton matter. The electric field produced by proton collectivity can accelerate proton and charged meson up to very high energies. Besides the studies of isospin physics such as symmetry energy, these results may help us to understand the acceleration mechanisms of high energy charged particles in the cosmic rays. Figure 1 shows neutrons and protons separation from a nucleus in strong magnetic field. Figure 2 shows highly asymmetric neutron-rich matter formed in strong magnetic field comparing with the general case.

The work has been published in Physics Letters B700 (2011) 249–253.The article can be linked as follows: http://www.sciencedirect.com/science/article/pii/S0370269311004850

Figure 1 Nuclear collision with or without strong magnetic field, red points denote protons, blues are neutrons (Imaged by IMP

Figure 2 Asymmetric nuclear matter formed in strong magnetic field. Red line denotes the formed high density matter’s n/p with magnetic field, blue line denotes the case without magnetic field (Imaged by IMP).