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Fundamental Physics with Cold and Ultracold Neutrons


Physical Measurement Laboratory, Radiation Physics Division

RO# Location
50.68.21.B4084 Gaithersburg, MD

Please note: This Agency only participates in the February and August reviews.


Name E-mail Phone
Dewey, Maynard S. 301.975.4843
Hoogerheide, Shannon 301.975.8582
Mumm, Hans Pieter 301.975.8355
Nico, Jeffrey Scott 301.975.4663


Neutron beta-decay is an excellent “laboratory” for studying the weak interaction. Through measurements of its lifetime and beta-decay correlation coefficients, one can extract parameters that completely characterize the weak force. Measurement of the lifetime also provides information on the abundances of the light elements produced during the Big Bang. Neutrons are used in searches for time-reversal (T) violation through a non-zero electric dipole moment or through a non-zero T-violating asymmetry coefficient in the decay process.

We are working to measure the neutron lifetime using magnetically trapped ultracold neutrons. The technique is complementary to existing measurements and offers the promise of a significant improvement in accuracy. In addition, we are measuring the energy spectrum of photons that are emitted along with the proton, electron, and antineutrino roughly once in every hundred decays of the neutron; the beta-decay asymmetry parameters (such as spin-proton asymmetry); and the T-violating decay coefficient. Another experiment measures the parity nonconserving spin rotation of polarized neutrons as they pass through a liquid helium target. In conjunction with these experiments, we are improving the accuracy with which cold neutron fluence and polarization can be measured.


Cold neutrons; Cosmology; Ultracold neutrons;


Citizenship:  Open to U.S. citizens
Level:  Open to Postdoctoral applicants


Base Stipend Travel Allotment Supplementation
$74,750.00 $3,000.00
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