S. K. Lamoreaux

Neutron electric-dipole moment, ultracold neutrons and polarized 3He

Abstract A brief review of the history of the experimental search for the neutron electric-dipole moment (EDM) is presented, followed by a discussion of the “state of the art” experimental techniques based on the storage of ultracold neutrons. Also discussed is the recent work on the construction of an improved experiment incorporating a 199 Hg magnetometer within the ultracold neutron storage volume. We then review a number of well-known experimental and theoretical results and propose an entirely new experimental technique to search for the neutron EDM based on storing together, in superfluid 4 He, polarized ultracold neutrons and a polarized gas of 3 He atoms; this forms a unique system of two spins interacting by means of a spin-dependent mutual absorption. Such a system appears to be ideally suited for use in a neutron EDM search. Following a brief description of the method, we present an analysis of the dynamics of such a system and calculate the statistical uncertainties to be expected in an EDM search. We show that, in principle, improvement by a factor of over 1000 in the experimental limit is possible. This limit would be more than sufficient to determine whether the known CP violation leads to the observed cosmological baryon asymmetry and, in addition, would set very strict limits on the supersymmetric, multi-Higgs, and left-right-symmetric models of CP violation. We conclude with a discussion of some technical questions related to the proposed experimental technique.

Apparatus for measurement of the electric dipole moment of the neutron using a cohabiting atomic-mercury magnetometer

A description is presented of apparatus used to carry out an experimental search for an electric dipole moment of the neutron, at the Institut Laue-Langevin (ILL), Grenoble. The experiment incorporated a cohabiting atomic-mercury magnetometer in order to reduce spurious signals from magnetic field fluctuations. The result has been published in an earlier letter [1]; here, the methods and equipment used are discussed in detail.

The electric dipole moments of atoms: Limits on P, T violating interactions within the atom

Abstract Violation of time reversal symmetry has been observed only in K 0 decay, and remains one of the great unsolved problems in elementary particle physics. The existence of a permanent electric dipole moment (EDM) of some “simple” system such as the neutron or an atom would also be evidence of T violation. Experimental limits of the EDM of 199 Hg set limits on possible T violating interactions which are comparable to those set by the experimental limit of the neutron EDM. In addition, atoms are sensitive to other T violating effects such as an intrinsic EDM of the electron or electron-nucleon interactions.

Conflict between Nulls: Mutual Exclusiveness of the Search for n-bar n Oscillations and Searches for an Antimatter-Matter Dependence of the Gravitational Interaction

In this note we call attention to the fact that a successful result in either the search for n- oscillations or the search for a difference in the gravitational interaction of matter and antimatter will rule out the possibility of success in the other.

Demonstrations of Berry's phase using polarised neutrons

Abstract Experiments with spin polarized neutrons in both spatially and time varying magnetic fields demonstrating manifestations of Berrys topological phase are reported. Several properties of Berrys phase have been verified; these include its solid angle dependency and additivity for multiple excursions along the same path in parameter space.

Practical positron catching in a Penning trap

Abstract An improved simple and robust scheme for efficiently catching and thermalizing at 4 K in a Penning trap positrons in vacuum is proposed. Positrons from a small-diameter commercial 22 Na source are utilized that incorporates a 14 mg cm −2 transmission moderator window of monocrystalline Ni or W. Catching efficiency may be optimized even in the presence of surface contamination by picking positrons with moderated energies from anywhere in a 0–5 keV range for catching.