title: Limits on anomalous spin-spin couplings between neutrons.
abstract: We report experimental limits on new spin-dependent macroscopic forces between neutrons. We measured the nuclear Zeeman frequencies of a 3He/129Xe maser while modulating the nuclear spin polarization of a nearby 3He ensemble in a separate glass cell. We place limits on the coupling strength of neutron spin-spin interactions mediated by light pseudoscalar particles like the axion [g(p)g(p)/(4pihc)] at the 3 x 10(-7) level for interaction ranges longer than about 40 cm. This limit is about 10(-5) the size of the magnetic dipole-dipole interaction between neutrons.
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Glenday
authors.forename: Claire E
authors.initials: CE
authors.lastname: Cramer
authors.forename: David F
authors.initials: DF
authors.lastname: Phillips
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Walsworth