3 research outputs found
The spin-dependent nd scattering length - a proposed high-accuracy measurement
The understanding of few-nucleon systems at low energies is essential, e.g.
for accurate predictions of element abundances in big-bang and stellar fusion.
Novel effective field theories, taking only nucleons, or nucleons and pions as
explicit degrees of freedom, provide a systematic approach, permitting an
estimate of theoretical uncertainties. Basic constants parameterising the short
range physics are derived from only a handful of experimental values. The
doublet neutron scattering length a_2 of the deuteron is particularly sensitive
to a three-nucleon contact interaction, but experimentally known with only 6%
accuracy. It can be deduced from the two experimentally accessible parameters
of the nd scattering length. We plan to measure the poorly known "incoherent"
nd scattering length a_{i,d} with 10^{-3} accuracy, using a Ramsey apparatus
for pseudomagnetic precession with a cold polarised neutron beam at PSI. A
polarised target containing both deuterons and protons will permit a
measurement relative to the incoherent np scattering length, which is know
experimentally with an accuracy of 2.4\times 10^{-4}.Comment: 5 pages LaTeX2e, 1 .eps figure. To be published in Nucl. Inst.
Methods A as part of the Proceedings of the 9th International Workshop on
Polarized Solid Targets and Techniques in Bad Honnef (Germany), 27th - 29th
October 200