Experimental study on the electric polarizability of the neutron

Abstract

Neutron transmission cross sections of lead and bismuth were measured for 143 keV and with high precision for 1970 eV neutrons which were selected from the reactor neutron spectrum by means of a novel dual combination of resonance scatterers. These data and highly accurate values of the coherent scattering lengths at zero energy and of transmission cross sections at 1.26, 5.19, 18.8 and 132 eV were the basis to determine the potential scattering radii, the neutron electron and the electric polarization scattering lengths as well as to test the used resonance corrections by which the influence of nuclear reactions on the results is eliminated. We obtained for the electric polarizability of the neutron: ~,=(0.8+1.0) 10-3fm 3 and for the neutron electron scattering length:b,e =(-1.32+ 0.04)i0-3 fm. In conclusion we have shown that these results favour the cloudy bag model for the description of the neutron's charge structure.

Cross sections for neutrons of 1970 eV and contributions to fundamental neutron interactions

“…For the determination of the neutron's polarizability we performed high precision measurements of the neutron cross sections of lead by means of the 186W and 59C0 double resonance scattering [5]. However, to achieve a markedly better accuracy of the result, Pb cross section values at energies of about 2 keV would be favourable as shown in [6]. Since the 2850 eV of the 2aNa resonance is unfavourable due to poor selectivity and nearby resonances in Pb and Bi, we looked for a combination of scatterers with resonance energies at 2000 eV which are different just by the mean energy loss AE.…”

“…b'(0) is the coherent scattering length be, which has been already measured with high precision for Pb and Bi [12,6]. The terms b,eZf(E) and g(E), and also the small difference bN(E1)-bN(E2), for measurement at E1 and E2, can be calculated as reported in [6].…”

“…The terms b,eZf(E) and g(E), and also the small difference bN(E1)-bN(E2), for measurement at E1 and E2, can be calculated as reported in [6]. Scattering amplitudes b' (E) are obtained from precision values of the transmission cross section according to (1) and (2).…”

Nucleon Knockout by Intermediate Energy Electrons

“…3.5. The form factors deduced using the Paris or RSC potentials give slopes at in good agreement with the data of Koester et al (97,98) for the scattering of low-energy neutrons by atomic electrons, but the form factors deduced using the Argonne V14 or Nijmegen potentials give slopes which are about 50% larger. However, the Platchkov data themselves do not determine this slope very well -the value deduced for the slope is determined by the parameter a in Eq.…”

“…(88) Models: solid line, dispersiontheoretical fit long dashes and dash-dot curves, VMD-PQCD models 1 and by about 20% even though the data themselves are consistent. Koester et al (97,98) obtain f m, while Alexandrov et al (99) obtain f m . Leeb and Teichtmeister (100) have analyzed the methods employed by both groups and trace the discrepancy to the treatment of resonance corrections.…”