Speaker: Pinghan Chu
Title: The Neutron EDM and the Dressed Spin
Abstract: The search of the neutron electric dipole moment provides a very sensitive test of physics beyond the Standard Model(SM). The SM prediction for the nEDM is at the 10^â31 e cm level, below current experimental limit by five orders of magnitude. However, many theoretical models beyond the SM can accommodate a larger value of the nEDM by several orders of magnitude. If a new source of T violation presents in nature, it could be relevant to this hadronic system. The SNS nEDM experiment invokes new techniques to search for the neutron EDM. It proposes to produce high density of ultra-cold neutrons in superfluid 4He. Polarized 3He will be used as a spin-analyzer and a comagnetometer. The rate of neutron absorption on 3He which can be detected from the emitted scintillation light, depends sensitively on the relative spin orientation of the two particles. The different frequencies of the signals in different electric field directions will determine the neutron EDM. The âdressed spin techniqueâ? is introduced to eliminate or greatly reduce the systematic error caused by the the drift of the magnetic field. The idea is to apply a non-resonance RF field to modify the Larmor frequency of neutron and 3He so that they can precess together. We report a measurement of the modiï¬?cation of the effective precession frequency of polarized 3He atoms in response to a dressing ï¬?eld in a room temperature cell. The 3He atoms were polarized using the metastability spin-exchange method. An oscillating dressing ï¬?eld is then applied perpendicular to the constant magnetic ï¬?eld. Modiï¬?cation of the 3He effective precession frequency was observed over a broad range of the amplitude and frequency of the dressing ï¬?eld. Many other issues related to the dressed spin technique in the proposed nEDM experiment have been studied, including the feedback scheme and the ultimate sensitivity of the experiment.
Location: Jadwin 233
Date/Time: 02/25/11 at 12:00 pm - 02/25/11 at 1:00 pm
Category: Atomic Physics Seminar