Nuclear spin content and constraints on exotic spin-dependent couplings

Abstract

There are numerous recent and ongoing experiments employing a variety of atomic species to search for couplings of atomic spins to exotic fields. In order to meaningfully compare these experimental results, the coupling of the exotic field to the atomic spin must be interpreted in terms of the coupling to electron, proton, and neutron spins. Traditionally, constraints from atomic experiments on exotic couplings to neutron and proton spins have been derived using the single-particle Schmidt model for nuclear spin. In this model, particular atomic species are sensitive to either neutron or proton spin couplings, but not both. More recently, semi-empirical models employing nuclear magnetic moment data have been used to derive new constraints for non-valence nucleons. However, comparison of such semi-empirical models to detailed large-scale nuclear shell model calculations and analysis of known physical effects in nuclei show that existing semi-empirical models cannot reliably be used to predict the spin polarization of non-valence nucleons. The results of our re-analysis of nuclear spin content are applied to searches for exotic long-range monopole-dipole and dipole-dipole couplings of nuclei leading to significant revisions of some published constraints. OPEN ACCESS RECEIVED

Search for Axionlike Dark Matter with a Liquid-State Nuclear Spin Comagnetometer

“…where γ h,c are the gyromagnetic ratios for 1 H and 13 C, respectively, B z is the magnitude of the bias magnetic field, g app and g ann are the coupling strengths of protons (from 1 H) and neutrons (from 13 C) with axions, respectively [48][49][50], ± refers to reversing the magnetic field direction, and v z is the z component of the expected average velocity of the axion wind in laboratory coordinates.…”

Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)

“…To interpret data from the GNOME, we employ a relatively simple framework for modeling the response of magnetometers to exotic spin-dependent interactions (reviewed in Refs. [2] and [47]), valid to first-order for electrons and valence nucleons, based on the Russell-Saunders approximation for the atomic structure and the Schmidt model for the nuclear structure. Table II shows the relevant intrinsic factors related to the magnetometers' sensitivities to exotic fields: the Landé g-factors, projection of the electron spin polarization along the total atomic angular momentum direction normalized to the total atomic angular momentum σ e = S e · F F (F + 1)…”

Searching for axion stars and Q -balls with a terrestrial magnetometer network

“…The magnetometric sensitivity of existing GNOME sensors is δB ≈ 100 fT= ffiffiffiffiffiffi Hz p over a bandwidth of ≈100 Hz. The GNOME is primarily sensitive to exotic interactions of electrons and protons [62]. A nextgeneration Advanced GNOME is under development that will use alkali-3 He comagnetometers [63][64][65][66] and will be primarily sensitive to neutron interactions [62].…”

“…The GNOME is primarily sensitive to exotic interactions of electrons and protons [62]. A nextgeneration Advanced GNOME is under development that will use alkali-3 He comagnetometers [63][64][65][66] and will be primarily sensitive to neutron interactions [62]. Advanced GNOME sensors will have effective sensitivities of δB ≈ 1 fT= ffiffiffiffiffiffi Hz p to "pseudomagnetic fields" caused by ALP interactions over a similar bandwidth [63,64].…”

“…2. Estimated parameter space probed by the existing GNOME (dashed line, purple fill) and by the Advanced GNOME (dotted line, light blue fill) for the quadratic interaction of electron/proton spins or neutron spins, respectively, with an ALP star [62]. We assume that L ¼ 10 −3 ly, and for m a >4×10 −15 eV, R ¼ R min ¼ 10R E , and for m a < 4×10 −15 eV, R ¼ λ a .…”