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Published June 1, 1994 | Published
Journal Article Open

Measurement of kinematic and nuclear dependence of R = σ_L/σ_T in deep inelastic electron scattering


We report results on a precision measurement of the ratio R=σ_L/σ_T in deep inelastic electron-nucleon scattering in the kinematic range 0.2≤x≤0.5 and 1≤Q^2≤10 (GeV/c)^2. Our results show, for the first time, a clear falloff of R with increasing Q^2. Our R results are in agreement with QCD predictions only when corrections for target mass effects and some additional higher twist effects are included. At small x, the data on R favor structure functions with a large gluon contribution. We also report results on the differences R_A-R_D and the cross section ratio σ^A/σ^D between Fe and Au nuclei and the deuteron. Our results for R_A-R_D are consistent with zero for all x, Q^2 indicating that possible contributions to R from nuclear higher twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The ratios σ^A/σ^D from all recent experiments, at all x, Q^2 values, are now in agreement.

Additional Information

© 1994 The American Physical Society. Received 4 November 1993; published in the issue dated 1 June 1994. We would like to thank the SLAC management and staff, in particular, R. Eisele, C. Hudspeth, G. Davis, J. Mark, M. Starek, and J. Nicol, for their able assistance during the running of this experiment. This research was supported by National Science Foundation Grant Nos. PHY85-05682 and PHY84-10549 and Department of Energy Contract Nos. DE-AC02-76ER13065, DE-AC02-76ER02853, DE-AC03-76SF00515, W-7405-ENG-48, and the US-Israel Binational Science Foundation.

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August 20, 2023
August 20, 2023