Preferredframe and CPviolation tests with polarized electrons
Abstract
We used a torsion pendulum containing ≈10^{23} polarized electrons to search new interactions that couple to electron spin. We limit CPviolating interactions between the pendulum’s electrons and unpolarized matter in the Earth or the Sun, test for rotation and boostdependent preferredframe effects using the Earth’s rotation and velocity with respect to the entire cosmos, and search for exotic velocitydependent potentials between polarized electrons and unpolarized matter in the Sun and Moon. We find CPviolating parameters g_{P}^{e}g_{S}^{N}/(ℏc)<9.4×10^{37} and g_{A}^{e}g_{V}^{N}/(ℏc)<1.2×10^{56} for λ>1AU. We test for preferredframe interactions of the form V=σ^{e}·A, V=Bσ^{e}·v/c, or V=∑σ_{i}^{e}C_{ij}v_{j}/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 A_{X,Y}≤1.5×10^{22}eV and A_{Z}≤4.4×10^{21}eV that may be compared to the benchmark value m_{e}^{2}/M_{Planck}=2×10^{17}eV. Interpreting our constraint on A in terms of noncommutative geometry, we obtain an upper bound of (355l_{GUT})^{2} on the minimum observable area, where l_{GUT}=ℏc/(10^{16}GeV) is the grand unification length. We find that B≤1.2×10^{19}eV. All 9 components of C are constrained at the 10^{17} to 10^{18}eV level. We determine 9 linear combinations of parameters of the standard model extension; rotationalnoninvariant and boostnoninvariant terms are limited at roughly the 10^{31}GeV and 10^{27}GeV 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 10^{21} from an electron spinning in the opposite direction. As a byproduct of this work, the density of polarized electrons in SmCo_{5} was measured to be (4.19±0.19)×10^{22}cm^{3} at a field of 9.6 kG.
 Publication:

Physical Review D
 Pub Date:
 November 2008
 DOI:
 10.1103/PhysRevD.78.092006
 arXiv:
 arXiv:0808.2673
 Bibcode:
 2008PhRvD..78i2006H
 Keywords:

 11.30.Cp;
 12.20.Fv;
 Lorentz and Poincare invariance;
 Experimental tests;
 High Energy Physics  Experiment
 EPrint:
 54 pages, 18 figures, Submitted to PRD