MAGNETIC EFFECTS: A NEW ISSUE ON CONSTRAINT OF SYMMETRY ENERGY

The magnetic effects on π⁻/π⁺ ratio as a function of rapidity are investigated. It is found that the π⁻/π⁺ ratio as a function of rapidity significantly altered by the magnetic field created in heavy ion collisions. At beam energies above about 1 GeV/nucleon, while the integrated ratio of total π⁻ to π⁺ multiplicities is not, the differential π⁻/π⁺ ratio is sensitive to the density dependence of nuclear symmetry energy E_sym(ρ). Our findings suggest that magnetic effects should be carefully considered in future studies of using the differential π⁻/π⁺ ratio as a probe of the E_sym(ρ) at supra-saturation densities.