Title : Positron-helium scattering at medium energies using close-coupling approximation Authors : Puspitapallab Chaudhuri and Sadhan K adhikari Affiliations : Instituto de F\'isica Te\'orica, UNESP, 01405-900, s\~ao Paulo, S\~ao Paulo, Brazil Summary : Elastic, excitation and positronium formation processes in positron-helium scattering have been investigated using the close-coupling approximation with realistic wave functions employing the following states : He(1s1s), He(1s2s), He(1s2p), He(1s3s), He(1s3p), Ps(1s), Ps(2s) and Ps(2p). Results are compared with other theoretical and experimental studies. The present cross sections are in good agreement with experimental results.