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The spin-dependent nd scattering length - a proposed high-accuracy measurement

B. van den Brandt·H. W. Griesshammer·P. Hautle·J. Kohlbrecher·J. A. Konter·O. Zimmer
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Abstract

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}.

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B. van den Brandt, H. W. Griesshammer, P. Hautle, J. Kohlbrecher, J. A. Konter, O. Zimmer. 2004-01-23. The spin-dependent nd scattering length - a proposed high-accuracy measurement. https://doi.org/10.1016/j.nima.2004.03.156

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