Evidence for a proton halo in \chem{^{27}P} through measurements of reaction cross-sections at intermediate energies

Measurements of reaction cross-sections ($\sigma_{\rm R}$'s) for some proton-rich nuclei (N=11\mbox{--}15 isotones) on carbon target at intermediate energies have been performed on RIBLL of HIRFL. A larger enhancement of the $\sigma_{\rm R}$ 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 $\sigma_{\rm R}$ data for the first time, which conform the long tail in its densities as predicted by RMF calculations