2008/08/20 by B. R. Heckel, E. G. Adelberger, Claire Cramer +6 · 6 citations
Physics and Astronomy · #Neutrino Physics Research #Noncommutative and Quantum Gravity Theories #Particle physics theoretical and experimental studies #hep-ex
paper · pdf · doi:10.1103/physrevd.78.092006
published as Phys.Rev.D78:092006,2008 · 54 pages, 18 figures, Submitted to PRD
arxiv created 2008/08/20 · openalex publication_date 2008/11/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We used a torsion pendulum containing \ensuremath≈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|/(\ensuremathℏc)<9.4\ifmmode×\else\texttimes\fi10^\ensuremath-37 and |gAegVN|/(\ensuremathℏc)<1.2\ifmmode×\else\texttimes\fi10^\ensuremath-56 for \ensuremathλ>1 AU. We test for preferred-frame interactions of the form V=\ensuremath-\mathbit\ensuremathσe\ifmmode⋅\else\textperiodcentered\fi\mathbitA, V=\ensuremath-B\mathbit\ensuremathσe\ifmmode⋅\else\textperiodcentered\fi\mathbitv/c, or V=\ensuremath-\ensuremath∑\ensuremathσieCijvj/c, where \mathbitv 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 1\ensuremathσ upper limits |\mathbitAX,Y|\ensuremath≤1.5\ifmmode×\else\texttimes\fi10^\ensuremath-22 eV and |\mathbitAZ|\ensuremath≤4.4\ifmmode×\else\texttimes\fi10^\ensuremath-21 eV that may be compared to the benchmark value me2/MPlanck=2\ifmmode×\else\texttimes\fi10^\ensuremath-17 eV. Interpreting our constraint on \mathbitA in terms of noncommutative geometry, we obtain an upper bound of (355lGUT)2 on the minimum observable area, where lGUT=\ensuremathℏc/(1016 GeV) is the grand unification length. We find that |B|\ensuremath≤1.2\ifmmode×\else\texttimes\fi10^\ensuremath-19 eV. All 9 components of \mathbitC are constrained at the 10^\ensuremath-17 to 10^\ensuremath-18 eV 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^\ensuremath-31 GeV and 10^\ensuremath-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 1021 from an electron spinning in the opposite direction. As a byproduct of this work, the density of polarized electrons in Sm Co5 was measured to be (4.19\ifmmode±\else\textpm\fi0.19)\ifmmode×\else\texttimes\fi1022 cm^\ensuremath-3 at a field of 9.6 kG.