New Test of the Gravitational 1/r

We tested the gravitational 1/r^{2} law using a stationary torsion-balance detector and a rotating attractor containing test bodies with both 18-fold and 120-fold azimuthal symmetries that simultaneously tests the 1/r^{2} law at two different length scales. We took data at detector-attractor separations between 52 µm and 3.0 mm. Newtonian gravity gave an excellent fit to our data, limiting with 95% confidence any gravitational-strength Yukawa interactions to ranges <38.6 µm.

Constraints on Axionlike Dark Matter with Masses Down to 10

We analyzed a 6.7-yr span of data from a rotating torsion-pendulum containing ≈10^{23} polarized electrons to search for the "wind" arising from ultralight, axionlike dark matter with masses between 10^{-23} and 10^{-18} eV/c^{2}. Over much of this range we set a 95% confidence limit F_{a}/C_{e}>2×10^{15} eV on the axionlike decay constant.

Short-Range, Spin-Dependent Interactions of Electrons: A Probe for Exotic Pseudo-Goldstone Bosons.

We used a torsion pendulum and rotating attractor with 20-pole electron-spin distributions to probe dipole-dipole interactions mediated by exotic pseudo-Goldstone bosons with m(b)c(2)≤500 µeV and coupling strengths up to 14 orders of magnitude weaker than electromagnetism. This corresponds to symmetry-breaking scales F≤70 TeV, the highest reached in any laboratory experiment. We used an attractor with a 20-pole unpolarized mass distribution to improve laboratory bounds on CP-violating monopole-dipole forces with 1.5 µeV

Limits on exotic long-range spin-spin interactions of electrons.

We surrounded a rotating torsion pendulum containing 9.8×10(22) polarized electrons by 2 or 4 stationary sources, each with a net spin of 6.0×10(24) polarized electrons. Multiple source configurations gave sensitivity to hypothetical dipole-dipole, spin-dot-spin, and spin-cross-spin exchange interactions mediated by bosons with masses up to 20 µeV. For bosons with masses ≤0.1 µeV our null results for the dipole-dipole, spin-dot-spin, and spin-cross-spin forces imply 1σ upper limits on (g(P)(e))(2)/(hc), (g(A)(e))(2)/(hc) and (g(V)(e)g(A)(e))/(hc) of 2.2×10(-16), 3.8×10(-40), and 1.2×10(-28), respectively. We also constrain, for the first time, any possible linear combination of static spin-spin interactions. In this case our upper limits relax to 5.6×10(-16), 9.8×10(-40), and 1.2×10(-28), respectively.

Improved constraints on an axion-mediated force.

Low mass pseudoscalars, such as the axion, can mediate macroscopic parity and time-reversal symmetry-violating forces. We searched for such a force between polarized electrons and unpolarized atoms using a novel, magnetically unshielded torsion pendulum. We improved the laboratory bounds on this force by more than 10 orders of magnitude for pseudoscalars heavier than 1 meV and have constrained this force over a broad range of astrophysically interesting masses (10 µeV to 10 meV).

Test of the equivalence principle using a rotating torsion balance.

We used a continuously rotating torsion balance instrument to measure the acceleration difference of beryllium and titanium test bodies towards sources at a variety of distances. Our result Deltaa(N),(Be-Ti)=(0.6+/-3.1)x10(-15) m/s2 improves limits on equivalence-principle violations with ranges from 1 m to infinity by an order of magnitude. The Eötvös parameter is eta(Earth,Be-Ti)=(0.3+/-1.8)x10(-13). By analyzing our data for accelerations towards the center of the Milky Way we find equal attractions of Be and Ti towards galactic dark matter, yielding eta(DM,Be-Ti)=(-4+/-7)x10(-5). Space-fixed differential accelerations in any direction are limited to less than 8.8x10(-15) m/s2 with 95% confidence.

Particle-physics implications of a recent test of the gravitational inverse-square law.

We use data from our recent search for violations of the gravitational inverse-square law to constrain dilaton, radion, and chameleon exchange forces as well as arbitrary vector or scalar Yukawa interactions. We test the interpretation of the PVLAS Collaboration effect and a conjectured "fat-graviton" scenario and constrain the gamma_{5} couplings of pseuodscalar bosons and arbitrary power-law interactions.

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|

New CP-violation and preferred-frame tests with polarized electrons.

We used a torsion pendulum containing approximately 9 x 10(22) polarized electrons to search for CP-violating interactions between the pendulum's electrons and unpolarized matter in the laboratory's surroundings or the Sun, and to test for preferred-frame effects that would precess the electrons about a direction fixed in inertial space. We find, /g(P)(e)g(S)(N)//(Planck's constant x c) < 1.7 x 10(-36), and /g(A)(e)g(V)(N)//(Planck's constant x c) < 4.8 x 10(-56) for lambda > 1 AU. Our preferred-frame constraints, interpreted in the Kostelecký framework, set an upper limit on the parameter /b(e)/

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.

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.