We used a torsion pendulum containing ≈1023 polarized electrons to search new interactions that couple to electron spin. We limit CP-violating interactions between the pendulum’s electrons and unpolarized matter in the Earth or the Sun, test for rotation and boost-dependent preferred-frame effects using the Earth’s rotation and velocity with respect to the entire cosmos, and search for exotic velocity-dependent potentials between polarized electrons and unpolarized matter in the Sun and Moon. We find CP-violating parameters |gPegSN|/(ℏc)<9.4×10-37 and |gAegVN|/(ℏc)<1.2×10-56 for λ>1AU. We test for preferred-frame interactions of the form V=-σe·A, V=-Bσe·v/c, or V=-∑σieCijvj/c, where v is the velocity of the Earth with respect to the cosmic microwave background restframe and i, j represent the equatorial inertial coordinates X, Y, and Z. We constrain all 3 components of A, obtaining 1σ upper limits |AX,Y|≤1.5×10-22eV and |AZ|≤4.4×10-21eV that may be compared to the benchmark value me2/MPlanck=2×10-17eV. Interpreting our constraint on A in terms of noncommutative geometry, we obtain an upper bound of (355lGUT)2 on the minimum observable area, where lGUT=ℏc/(1016GeV) is the grand unification length. We find that |B|≤1.2×10-19eV. All 9 components of C are constrained at the 10-17 to 10-18eV level. We determine 9 linear combinations of parameters of the standard model extension; rotational-noninvariant and boost-noninvariant terms are limited at roughly the 10-31GeV and 10-27GeV levels, respectively. Finally, we find that the gravitational mass of an electron spinning toward the galactic center differs by less than about 1 part in 1021 from an electron spinning in the opposite direction. As a byproduct of this work, the density of polarized electrons in SmCo5 was measured to be (4.19±0.19)×1022cm-3 at a field of 9.6 kG.
Physical Review D
- Pub Date:
- November 2008
- Lorentz and Poincare invariance;
- Experimental tests;
- High Energy Physics - Experiment
- 54 pages, 18 figures, Submitted to PRD