$s$-wave scattering lengths for $^7$Be+p system from $R$-matrix analysis*

The astrophysical S factor near zero energy for the $^7$Be+p radiative capture reaction depends on the $s$-wave scattering lengths. The $s$-wave scattering lengths can be determined via $R$-matrix analysis of the scattering data. We report the measurement of elastic and inelastic scattering cross section for the $^7$Be+p system in the center-of-mass energy range of 0.474-2.740 MeV. The radioactive $^7$Be beam produced at Oak Ridge National Laboratory's Holifield Radioactive Ion Beam Facility was accelerated and bombarded a 100-$\mu$g/cm$^2$ polypropylene target. The scattered particles were detected in a segmented silicon setector array. The $R$-matrix code AZURE2 has been used for the simultaneous fitting of the elastic and inelastic scattering data from this measurement and other available data. The $s$-wave scattering lengths were determined using the best fit $R$-matrix parameters and will be presented. The preliminary results from the $R$-matrix analysis of the data will be presented and the level structure of $^8$B will be discussed. The prospects for a new measurement of $^7$Be+p elastic scattering at the DRAGON facility of TRIUMF using gas target will also be discussed.