Rakshya Khatiwada

Laboratory search for spin-dependent short-range force from axionlike particles using optically polarized 3He gas

The possible existence of short-range forces between unpolarized and polarized spin-1/2 particles has attracted the attention of physicists for decades. These forces are predicted in various theories and provide a possible new source for parity (P) and time reversal (T) symmetry violation. We use an ensemble of polarized 3He gas in a cell with a 250 um thickness glass window to search for a force from scalar boson exchange over a sub-millimeter ranges. This interaction would produce a NMR frequency shift as an unpolarized mass is moved near and far from the polarized ensemble. We report a new upper bound on the product g_{s}g_{p}^{n} of the scalar couplings to the fermions in the unpolarized mass, and the pseudoscalar coupling of the polarized neutron in the 3He nucleus for force ranges from 1e-4 to 1e-2 m, which corresponds to a mass range of 2e-3 to 2e-5 eV for the scalar boson.

Prospects for electron spin-dependent short-range force experiments with rare earth iron garnet test masses

A study of the possible interactions between fermions assuming only rotational invariance has revealed 15 forms for the potential involving the fermion spins. We review the experimental constraints on unobserved macroscopic, spin-dependent interactions between electrons in the range below 1 cm. An existing experiment, using 1 kHz mechanical oscillators as test masses, has been used to constrain mass-coupled forces in this range. With suitable modifications, including spin-polarized test masses, this experiment can be used to explore all 15 possible spin-dependent interactions between electrons in this range with unprecedented sensitivity. Samples of ferrimagnetic dysprosium iron garnet have been fabricated in the suitable test mass geometry and shown to have high spin density with very low intrinsic magnetism.

A Frequency Determination Method for Digitized NMR Signals

We present a high precision frequency determination method for digitized NMR FID signals. The method employs high precision numerical integration rather than simple summation as in many other techniques. With no independent knowledge of the other parameters of a NMR FID signal (phase

Recent progress on the Axion Dark Matter eXperiment (ADMX)

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Quantum limited amplifiers for the Axion Dark Matter eXperiment (ADMX)

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Development of Gallium-Indium Alloys, Nonmagnetic Test Masses for Exotic Spin-Dependent Force Searches

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Progress of spin-dependent mesoscopic force experiments with rare-earth garnet test masses

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Development of Nonmagnetic Materials for Spin-Dependent Fifth Force Searches

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Searches for possible T-odd and P-odd interactions of mesoscopic range using polarized nuclei and nonmagnetic masses

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High-frequency search for mass-coupled mesoscopic forces

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