Measurement of the longitudinal spin-dependent neutron-proton total cross-section difference ΔσL(np) between 500 and 800 MeV

A measurement of Δ${\mathrm{\sigma }}_{\mathit{L}}$(np), the difference between neutron-proton total cross sections for pure longitudinal spin states, is described. Data were taken at LAMPF for five neutron beam kinetic energies: 484, 568, 634, 720, and 788 MeV. The statistical errors are in the range of 0.64–1.35 mb. Various sources of systematic effects were investigated and are described. Overall systematic errors are estimated to be on the order of 0.5 mb and include an estimate for the uncertainty in the neutron beam polarization. The Δ${\mathrm{\sigma }}_{\mathit{L}}$ results are consistent with previous results from PSI and Saclay. These data, when combined with other results and fitted to a Breit-Wigner curve, are consistent with an elastic I=0 resonance with mass 2214±15 (stat) ±6 (syst) MeV and width 75±21±12 MeV. Because of a lack of Δ${\mathrm{\sigma }}_{\mathit{T}}$(np) data between 500 and 800 MeV, it is not possible to differentiate between a singlet or coupled-triplet partial wave being responsible.