Physica B 190 (1993) 259-266 North-Holland Total cross section of lead and contributions from fundamental neutron interactions J.R. Granada and C. Bonetto zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Centro Atomic0 Bariloche and Institute Balseiro, S.C. de Bariloche (RN), Argentina S.A. Hayashi’, K. Kobayashi, S. Yamamoto, Y. Fujita and I. Kimura* Research Reactor Institute. Kyoto University. Osaka, Japan Reccivcd 29 September 1992 The total cross section of natural lead was measured for neutron encrgics between 1 cV and 9(N)eV, in a time-of-flight transmission experiment at the KURRI Electron Linear Accelerator pulsed neutron source. The mcasurcd data were used to determine the neutron electrical polarizability, after a careful analysis of the different contributions to the neutron-atom scattering length. The result obtained, (Y = (2.4 5 1.5) X 10 -’ fm’, is consistent with the most recent and accurate values, while at the same time it emphasizes the need of better statistics and the use of isotopically enriched samples to improve its precision. 1. Introduction The collision process of a neutron with an atom can be described in terms of a scattering length, which involves contributions from differ- ent interactions. Besides the strong nuclear inter- action and that due to the magnetic dipole coup- ling with the magnetic electrons when it exists, there remain the electromagnetic interactions of the neutron with the nucleus and the electrons. The latter ones are a few orders of magnitude smaller than the strong interaction, and they inclulde the spin-orbit interaction, the Foldy in- teraction, the nuclear magnetic dipole inter- action and those interactions related to the elec- t+ potnri7abilitv and the finite intrinsic charge CL._ .r.... ._I_ ““J Correspondence IO: J.K. Granada, Ccntro ktomico Bariloche and Instituto Balseiro, 8400 S.C. de Bariloche (RN). Argentina. ’ Present address: The Institute for Atomic Energy. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Rikkyj (St. Paul’s) University, 2-5-1. Nagasaka. Yokosuka. 23041 Japan. ’ Present address: Nuclear Engineering Department. Faculty of Engineering, Kyoto University, Yoshida Honmachi 1 Sakyo-ku. Kyoto. 606 Japan. radius of the neutron [I]. Present-day neutron sources and experimental techniques allow to explore those very small contributions to the scattering cross section, rendering possible in particular to atte ination of a fun- damental property of the neutron like its electri- cal polarizability CL From a theoretical point of view, this type of information is relevant to the discussion of different quark models, and conse- quently an intense activity in this field has re- cently developed [2,3]. The measurement of neutron total cross sec- tion for heavy elements over an energy range from zero up to several keV, permits a determi- nation of the neutron-electron scattering length the neutron electrical polarizabihty 14,5]. ever, special care is required to evaluate those small corrections if one illtends to diseri nate the effect due to c’ on the cross section. In this work, we present the result of a trans- mission experiment performed on na over epithermal neutron energies, toge a full description of t e different electr interactions and their corresponding 0921~4526/93/$06.0(1 Q 1993 - Elscvicr Sctence Publishers B.V. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGF AlI rights reserved