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

✍ Scribed by B. van den Brandt; H. Glättli; H. Grießhammer; P. Hautle; J. Kohlbrecher; J.A. Konter; O. Zimmer

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 201 KB
• Volume: 526
• Category: Article
• ISSN: 0168-9002
• DOI: 10.1016/j.nima.2004.03.156

✦ Synopsis

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 À3 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 nd scattering length, which is known experimentally with an accuracy of 2:4 Â 10 À4 :