Evidence for a proton halo in 27 P through measurements of reaction cross-sections at intermediate energies

: Measurements of reaction cross-sections ( σ R 's) for some proton-rich nuclei ( N = 11–15 isotones) on carbon target at intermediate energies have been performed on RIBLL of HIRFL. A larger enhancement of the σ R for 27 P has been observed than for its neighboring nuclei. A large difference between the proton and neutron density distributions (proton halo) is necessary to explain the enhanced cross-section for 27 P within the framework of the Glauber model. Density distributions with HO-type core plus Yukawa-square tail and rms radii for 27 P have been deduced from the measured σ R data for the first time, which conform the long tail in its densities as predicted by RMF calculations.