We have constrained possible new interactions which produce nonrelativistic potentials between polarized neutrons and unpolarized matter proportional to α σ · v where σ is the neutron spin and v is the relative velocity. We use existing data from laboratory measurements on the very long T1 and T2 spin relaxation times of polarized 3 He gas in glass cells. Using the best available measured T2 of polarized 3 He gas atoms as the polarized source and the earth as an unpolarized source, we obtain constraints on two new interactions. We present a new experimental upper bound on possible vector-axial-vector(VV A) type interactions for ranges between 1 ∼ 10 8 m. In combination with previous results, we set the most stringent experiment limits on gV gA ranging from ∼ µm to ∼ 10 8 m. We also report what is to our knowledge the first experimental upper limit on the possible torsion fields induced by the earth on its surface. Dedicated experiments could further improve these bounds by a factor of ∼ 100. Our method of analysis also makes it possible to probe many velocity dependent interactions which depend on the spins of both neutrons and other particles which have never been searched for before experimentally.PACS numbers: 13.88.+e, 13.75. Cs, 14.20.Dh, 14.70.Pw In recent years, various models of new physics beyond the Standard Model have been studied in which new massive particles such as the axion, familon and majoron, etc. were theoretically introduced [1]. New macroscopic interactions meditated by WISPs (weakly-interacting sub-eV particles) have also been theoretically proposed. The interaction ranges of these new forces range from nanometers to astronomical distance scales. The fact that the dark energy density is on the order of (1 meV) 4 corresponding to a length scale of 100 µm also encourages people to search for new physical phenomena around this scale [2]. Various experiments have been performed or proposed recently to search for a subset of these new interactions which could couple to the spin of the neutron/electron. Polarized neutron beams were used in the experiments presented in Refs. [3,4]. Polarized noble gases were used in Refs. [5][6][7][8]. Atomic magnetometers were applied in Refs. [9,10]. Experimental schemes using polarized atom beams have been recently proposed in Ref. [11].The idea that exotic new interactions might be spin/velocity dependent is quite fascinating. For example, the theoretically proposed photinos interact with nuclei only through spin-dependent forces [12]. Ref. [13] analyzed the possible nonrelativistic potentials between spin-1/2 fermions from spin 0 and spin 1 boson exchange and found 16 possible new interactions, 10 of which depend both on the spin states and the relative velocity be- * Corresponding author: hyan@caep.cn tween particles. Torsion, a twisting of spacetime coupled to intrinsic spin, which has been included in many models which extend general relativity [14,15], can also induce spin-velocity dependent interactions between an unpolarized source and the spin. Har...

Many experiments have been performed to search for the exotic spin-dependent interactions in ranges from ∼ µm to astrophysical range which corresponds to the energy scale of less than ∼10 eV. At present, nearly all known experiments searching for these new interactions at the macroscopic range are for protons, neutrons, and electrons. Constraints at this range for other fermions such as muons are scarce, though muons might be the most suspicious particles which might take part in new interactions, considering their involvement of several well-known puzzles of modern physics. We use the anomalous magnetic moment and electric dipole moment (EDM) to study the exotic spin-dependent interactions for muons and electrons. The muon's magnetic moment might indicate existing of the pseudo-scalar-pseudo-scalar (PP) type interaction. We set up a constraint for the scalarpseudo-scalar (SP) type interaction at the interested range for muons. For the PP type interaction of electrons, we obtained a new constraint at the range of ∼ nm to ∼ 1 mm. Since all the present experiments searching for the new forces give zero results, it is reasonable to consider that these new interactions might only couple to muons. We propose to further search for the new interactions using the muon spin rotation techniques.

The small-angle neutron scattering spectrometer, SANS-Suanni, of the 20 MW China Mianyang Research Reactor (CMRR), was upgraded recently to improve its performance and anti-risk capability. The major modifications include: (i) installing a new mechanical velocity selector consisting of a rotor with helical slots; (ii) a replacement of the front of the detector tank to decrease the minimum sample-to-detector distance; (iii) installing a laser locator and a set of fixed lenses in collimator chamber. After the modifications, firstly, a higher maximum-q (qmax) can be achieved up to 6.3 nm−1. With the help of rotating the detector tank, qmax can be further increased to 10.5 nm−1. Secondly, a higher neutron flux at sample position up to 1.18 ×107 cm−2s−1 (at neutron wavelength of 0.53 nm) is obtained. Thirdly, a convenient and user-friendly beam center finding operation for environmental devices is available. The actual performance after the modifications is demonstrated with the measurements of standard samples.

Experiments using polarized 3 He atom beams to search for short range spin dependent forces are proposed. High intensity, high polarization, small beam size 3 He atom beams have been successfully produced and used in surface science researches. By incorporating background reduction designs as combination shielding by µ-metal and superconductor and double beam paths, the precision of spin rotation angle per unit length could be improved by a factor of ∼ 10 4 . By this precision, in combination with a high density and low magnetic susceptibility sample source mass, and reversing one beam path if necessary, sensitivities on three different types of spin dependent interactions could be improved by as much as ∼10 2 to ∼10 8 over the current experiments at the millimeter range.

A: A longitudinal neutron resonance spin echo (L-NRSE) spectrometer combined with a MIEZE (modulated intensity with zero effort) configuration will be constructed at the C33 beam port at China Mianyang Research Reactor (CMRR). In the MIEZE mode, the analyzer is placed in front of the sample, and between the sample and the detector there is no other optical device. The MIEZE signal is sensitive to the neutron path length differences from the sample to the detector. In this work, we have analytically studied the effects of sample geometry, detector thickness, and experimental setup on the resolution function.