https://doi.org/10.1140/epjc/s2004-01987-9
experimental physics
Measurement of the np total cross section difference 
at 1.39, 1.69, 1.89 and 1.99 GeV
1
Veksler and Baldin Laboratory of High Energies, Joint Institute for Nuclear Research, 141980, Dubna, Russia
2
Russian Scientific Center “Kurchatov Institute”, 123182, Moscow, Russia
3
Dzhelepov Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, 141980, Dubna, Russia
4
High Energy Physics Division, Peterburg Nuclear Physics Institute, 188350, Gatchina, Russia
5
Kharkov Institute of Physics and Technology, 310108, Kharkov, Ukraine
6
Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980, Dubna, Russia
7
Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00, Praha 8, Czech Republic
8
Institute for Nuclear Research, Russian Academy of Sciences, 117312, Moscow, Russia
9
DAPNIA, CEA/Saclay, 91191, Gif-sur-Yvette Cedex, France
10
Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Tsarigradsko shaussee boulevard 72, 1784, Sofia, Bulgaria
11
Laboratory of Particle Physics, Joint Institute for Nuclear Research, 141980, Dubna, Russia
* e-mail: sharov@sunhe.jinr.ru
New accurate results of the neutron-proton spin-dependent total cross section difference at the neutron beam kinetic energies 1.39, 1.69, 1.89 and 1.99 GeV are presented. Measurements were carried out in 2001 at the Synchrophasotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research. A quasi-monochromatic neutron beam was produced by break-up of extracted polarized deuterons. The deuteron (and hence neutron) polarization direction was flipped every accelerator burst. The vertical neutron polarization direction was rotated onto the neutron beam direction and longitudinally (L) polarized neutrons were transmitted through a large proton L-polarized target. The target polarization vector was inverted after 1-2 days of measurements. The data were recorded for four different combinations of the beam and target parallel and antiparallel polarization directions at each energy. A fast decrease of with increasing energy above 1.1 GeV was confirmed. The structure in the energy dependence around 1.8 GeV, first observed from our previous data, seems to be well pronounced. The new results are also compared with model predictions and with phase shift analysis fits. The 
quantities for isosinglet state I = 0, deduced from the measured values and the known 
data, are also given. The results were completed by the measurements of unpolarized total cross sections 
at 1.3, 1.4 and 1.5 GeV and 
C) at 1.4 and 1.5 GeV. These data were obtained using the same apparatus and high intensity unpolarized deuteron beams were extracted either from the Synchrophasotron, or from the Nuclotron.
© Springer-Verlag, 2004
