Measurement of $R = \sigma_L/\sigma_T$ in deep inelastic muon-proton scattering

Abstract The ratio R = σ L σ T of the longitudinal to the tranverse photon absorption cross section has been determined from deep inelastic muon-proton scattering at incident energies of 120, 200 and 280 GeV. The results are given as a function of the variables x , Q 2 and ν of the interaction. In the kinematic range 60 ⩽ ν ⩽ 160 GeV at 〈 Q 2 〉 = 22.5 GeV 2 an average value of R = 0.00 ± 0.10 has been obtained.