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We investigate the sensitivities of searches for exotic spin-dependent interactions between the polarized nuclear spins of $^3$He and the particles of unpolarized or polarized solid-state masses using the frequency method and the resonance method. In the frequency method, the spin-dependent interactions act as an effective static magnetic field, causing the frequency shift to the spin precession of $^{3}$He. In the resonance method, proposed by Arvanitaki and Geraci [Phys. Rev. Lett. 113, 161801 (2014)] for the significant improvement of the experimental sensitivities on the spin-dependent interactions, the mass movement is modulated at the Larmor frequency of $^3$He. This results in the modulating spin-dependent interactions inducing an effective oscillatory magnetic field, which can tilt the $^3$He spins, similarly as an oscillatory magnetic field in nuclear magnetic resonance. We estimate the sensitivities of the searches using a room-temperature $^3$He target for its extremely long relaxation time. New limits on the coupling strengths of the spin-dependent interactions can be set in the interaction length range below $10^{-1}$ m.
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We report an experimental search for an exotic spin-spin-velocity-dependent interaction between polarized electrons of Rb atoms and polarized electrons of a solid-state mass, violating both the time-reversal and parity symmetries. This search targets a minute effective magnetic field induced by the interaction. A spin-exchange relaxation-free (SERF) magnetometer based on an optically polarized Rb vapor is the key element for both a source of polarized electrons and a high-sensitivity detector. A dysprosium iron garnet (DyIG) serves as the polarized mass, with an extremely small magnetization at the critical temperature around 240 K and a high spin density. To reduce the magnetization, one of major systematic effects, a home-built cooling system controls the mass temperature. To our knowledge, this is the first search for an exotic spin-dependent interaction using the compensated ferrimagnet DyIG as a polarized mass. The experiment set the most stringent limit on the electron-electron coupling strength in the centimeter interaction range, in particular $g_V^e g_V^e <10^{4}$ at $lambda=2$ cm.
We propose a new method to detect short-range textit{P-} and textit{T-} violating interactions between nucleons, based on measuring the precession frequency shift of polarized $^3$He nuclei in the presence of an unpolarized mass. To maximize the sensitivity, a high-pressure $^3$He cell with thin glass windows (250 $rmmu m$) is used to minimize the distance between the mass and $^3$He. The magnetic field fluctuation is suppressed by using the $^3$He gas in a different region of the cell as a magnetometer. Systematic uncertainties from the magnetic properties of the mass are suppressed by flipping both the magnetic field and spin directions. Without any magnetic shielding, our result has already reached the sensitivity of the current best limit. With improvement in uniformity and stability of the field, we can further improve the sensitivity by two orders of magnitude over the force range from $10^{-4}-10^{-2}$ m.
Measuring the depolarization rate of a $^3$He hyperpolarized gas is a sensitive method to probe hypothetical short-range spin-dependent forces. A dedicated experiment is being set up at the Institute Laue Langevin in Grenoble to improve the sensitivity. We presented the status of the experiment at the 10th PATRAS Workshop on Axions, WIMPs and WISPs.
We present a search for possible spin dependent interactions of the neutron with matter through exchange of spin 1 bosons with axial vector couplings as envisioned in possible extensions of the Standard Model. This was sought using a slow neutron polarimeter that passed transversely polarized slow neutrons by unpolarized slabs of material arranged so that this interaction would tilt the plane of polarization and develop a component along the neutron momentum. The result for the rotation angle, $phi_{V_5} = [2.8pm,4.6(stat.)pm,4.0(sys.)]times 10^{-5}~mbox{rad/m}$ is consistent with zero. This result improves the upper bounds on the neutron-matter coupling $g_{A}^{2}$ from such an interaction by about three orders of magnitude for force ranges in the mm-$mu$m regime.
Development of new techniques to search for particles beyond the standard model is crucial for understanding the ultraviolet completion of particle physics. Several hypothetical particles are predicted to mediate exotic spin-dependent interactions between particles of the standard model that may be accessible to laboratory experiments. However, laboratory searches are mostly conducted for static spin-dependent interactions, with only a few experiments so far addressing spin- and velocity-dependent interactions. Here, we demonstrate a search for exotic spin- and velocity-dependent interactions with a spin-based amplifier. Our technique makes use of hyperpolarized nuclear spins as a pre-amplifier to enhance the effect of pseudo-magnetic field produced by exotic interactions by an amplification factor of > 100. Using such a spin-based amplifier, we establish constraints on the spin- and velocity-dependent interactions between polarized and unpolarized nucleons in the force range of 0.03-100 m. Our limits represent at least two orders of magnitude improvement compared to previous experiments. The established technique can be further extended to investigate other exotic spin-dependent interactions.
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