Measurement of the Parity-Violating Neutron Spin Rotation in (4) He.
In the meson exchange model of weak nucleon-nucleon (NN) interactions, the exchange of virtual mesons between the nucleons is parameterized by a set of weak meson exchange amplitudes. The strengths of these amplitudes from theoretical calculations are not well known, and experimental measurements of parity-violating (PV) observables in different nuclear systems have not constrained their values. Transversely polarized cold neutrons traveling through liquid helium experience a PV spin rotation due to the weak interaction with an angle proportional to a linear combination of these weak meson exchange amplitudes. A measurement of the PV neutron spin rotation in helium (φ PV ( n ,α)) would provide information about the relative strengths of the weak meson exchange amplitudes, and with the longitudinal analyzing power measurement in the p + α system, allow the first comparison between isospin mirror systems in weak NN interaction. An earlier experiment performed at NIST obtained a result consistent with zero: φ PV ( n ,α) = (8.0 ±14(stat) ±2.2(syst)) ×10(-7) rad / m[1]. We describe a modified apparatus using a superfluid helium target to increase statistics and reduce systematic effects in an effort to reach a sensitivity goal of 10(-7) rad/m.
Indiana University/IUCF, Department, Department.
C D
CD
Bass
Indiana University/IUCF, Department, Department.
J M
JM
Dawkins
Indiana University/IUCF, Department, Department.
D
D
Luo
Indiana University/IUCF, Department, Department.
A
A
Micherdzinska
Indiana University/IUCF, Department, Department.
M
M
Sarsour
Indiana University/IUCF, Department, Department.
W M
WM
Snow
National Institute of Standards and Technology, Gaithersburg, MD 20890.
H P
HP
Mumm
National Institute of Standards and Technology, Gaithersburg, MD 20890.
J S
JS
Nico
North Carolina State University/TUNL Department.
P R
PR
Huffman
North Carolina State University/TUNL Department.
D M
DM
Markoff
University of Washington, Department, Department.
B R
BR
Heckel
University of Washington, Department, Department.
H E
HE
Swanson
cold neutrons; liquid helium; nucleon-nucleon interaction; parity non-conservation; parity violation; spin rotation; superfluid helium; weak interaction; weak meson exchange amplitude