First Observation of Cyclotron Radiation from MeV-Scale e

We present an apparatus for detection of cyclotron radiation yielding a frequency-based ß^{±} kinetic energy determination in the 5 keV to 2.1 MeV range, characteristic of nuclear ß decays. The cyclotron frequency of the radiating ß particles in a magnetic field is used to determine the ß energy precisely. Our work establishes the foundation to apply the cyclotron radiation emission spectroscopy (CRES) technique, developed by the Project 8 Collaboration, far beyond the 18-keV tritium endpoint region. We report initial measurements of ß^{-}'s from ^{6}He and ß^{+}'s from ^{19}Ne decays to demonstrate the broadband response of our detection system and assess potential systematic uncertainties for ß spectroscopy over the full (MeV) energy range. To our knowledge, this is the first direct observation of cyclotron radiation from individual highly relativistic ß's in a waveguide. This work establishes the application of CRES to a variety of nuclei, opening its reach to searches for new physics beyond the TeV scale via precision ß-decay measurements.

ß-Nuclear-Recoil Correlation from

We report the first precise measurement of a ß-recoil correlation from a radioactive noble gas (^{6}He) confined via a magneto-optical trap. The measurement is motivated by the search for exotic tensor-type contributions to the charged weak current. Interpreted as tensor currents with right-handed neutrinos, the measurements yield |C_{T}/C_{A}|^{2}≤0.022 (90% confidence limit, C.L.). On the other hand, for left-handed neutrinos the limits are 0.007

Precision measurement of the 6He half-life and the weak axial current in nuclei.

Studies of 6He beta decay along with tritium can play an important role in testing ab initio nuclear wave-function calculations and may allow for fixing low-energy constants in effective-field theories. Here, we present an improved determination of the 6He half-life to a relative precision of 3×10(-4). Our value of 806.89±0.11(stat)(-0.19syst)(+0.23) ms resolves a major discrepancy between previous measurements. Calculating the statistical rate function we determined the ft value to be 803.04(-0.23)(+0.26) s. The extracted Gamow-Teller matrix element agrees within a few percent with ab initio calculations.

Experimental upper bound and theoretical expectations for parity-violating neutron spin rotation in 4He.

Neutron spin rotation is expected from quark-quark weak interactions in the standard model, which induce weak interactions among nucleons that violate parity. We present the results from an experiment searching for the effect of parity violation via the spin rotation of polarized neutrons in a liquid 4He medium. The value for the neutron spin rotation angle per unit length in 4He, d ϕ / d z = [ + 2.1 ± 8.3 (stat.) - 0.2 + 2.9 (sys.) ] × 10 - 7 rad/m, is consistent with zero. The result agrees with the best current theoretical estimates of the size of nucleon-nucleon weak amplitudes from other experiments and with the expectations from recent theoretical approaches to weak nucleon-nucleon interactions. In this paper we review the theoretical status of parity violation in the n → + 4He system and discuss details of the data analysis leading to the quoted result. Analysis tools are presented that quantify systematic uncertainties in this measurement and that are expected to be essential for future measurements.

Measurement of the Parity-Violating Neutron Spin Rotation in (4) He.

In the meson exchange model of weak nucleon-nucleon (NN) interactions, the exchange of virtual mesons between the nucleons is parameterized by a set of weak meson exchange amplitudes. The strengths of these amplitudes from theoretical calculations are not well known, and experimental measurements of parity-violating (PV) observables in different nuclear systems have not constrained their values. Transversely polarized cold neutrons traveling through liquid helium experience a PV spin rotation due to the weak interaction with an angle proportional to a linear combination of these weak meson exchange amplitudes. A measurement of the PV neutron spin rotation in helium (φ PV ( n ,α)) would provide information about the relative strengths of the weak meson exchange amplitudes, and with the longitudinal analyzing power measurement in the p + α system, allow the first comparison between isospin mirror systems in weak NN interaction. An earlier experiment performed at NIST obtained a result consistent with zero: φ PV ( n ,α) = (8.0 ±14(stat) ±2.2(syst)) ×10(-7) rad / m[1]. We describe a modified apparatus using a superfluid helium target to increase statistics and reduce systematic effects in an effort to reach a sensitivity goal of 10(-7) rad/m.

A slow neutron polarimeter for the measurement of parity-odd neutron rotary power.

We present the design, description, calibration procedure, and an analysis of systematic effects for an apparatus designed to measure the rotation of the plane of polarization of a transversely polarized slow neutron beam as it passes through unpolarized matter. This device is the neutron optical equivalent of a crossed polarizer/analyzer pair familiar from light optics. This apparatus has been used to search for parity violation in the interaction of polarized slow neutrons in matter. Given the brightness of existing slow neutron sources, this apparatus is capable of measuring a neutron rotary power of dϕ/dz = 1 × 10(-7) rad/m.

Tests of the gravitational inverse-square law below the dark-energy length scale.

We conducted three torsion-balance experiments to test the gravitational inverse-square law at separations between 9.53 mm and 55 microm, probing distances less than the dark-energy length scale lambda(d)=[4 -root](variant Planck's over 2pic/rho(d) approximately 85 microm. We find with 95% confidence that the inverse-square law holds (|alpha|

Crystallography of Some Double Sulfates and Chromates.

New information is given on cell parameters, density and methods of preparation of 50 compounds of the langbeinite and Tutton salt groups. The langbeinites have the general formula (A+)2(B2+)2(XO4)3 and the Tutton salts the general formula (A+)2(B2+)(XO4)2 · 6H2O, where A is K, Rb, (NH4), Tl or Cs; B is Mg, Ni, Cu, Co, or Zn; and X is S or Cr. A comprehensive list of references on the crystallography of the compounds is included.

Crystallography and Preparation of Some ABCl3 Compounds.

Compounds of the composition ABCl3, in which A is K, Rb, NH4, or Cs and where B is a divalent element, have been reviewed. Ten new compounds were prepared on which there was little or no previous crystallographic information. Refined unit cell parameters were obtained on these and on fifteen other compounds in this group. A general review of the structural information on this group is presented in tables, and a comprehensive list of references is included.

Submillimeter test of the gravitational inverse-square law: a search for "large" extra dimensions.

Motivated by higher-dimensional theories that predict new effects, we tested the gravitational 1/r(2) law at separations ranging down to 218 microm using a 10-fold symmetric torsion pendulum and a rotating 10-fold symmetric attractor. We improved previous short-range constraints by up to a factor of 1000 and find no deviations from Newtonian physics.

7Be(p,gamma)8B astrophysical S factor from precision cross section measurements.

We measured the 7Be(p,gamma)8B cross section from E(c.m.) = 186 to 1200 keV, with a statistical-plus-systematic precision per point of better than +/-5%. All important systematic errors were measured including 8B backscattering losses. We obtain S17(0) = 22.3+/-0.7(expt)+/-0.5(theor) eV b from our data at E(c.m.)< or =300 keV and the theory of Descouvemont and Baye.