Article

Torsion-balance tests of the weak equivalence principle

Classical and Quantum Gravity (Impact Factor: 3.1). 07/2012; 29(18). DOI: 10.1088/0264-9381/29/18/184002
Source: arXiv

ABSTRACT We briefly summarize motivations for testing the weak equivalence principle
and then review recent torsion-balance results that compare the differential
accelerations of beryllium-aluminum and beryllium-titanium test body pairs with
precisions at the part in $10^{13}$ level. We discuss some implications of
these results for the gravitational properties of antimatter and dark matter,
and speculate about the prospects for further improvements in experimental
sensitivity.

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Available from: Stephan Schlamminger, Mar 19, 2014
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    • "where the sum runs over all SM massive vector bosons V , M V is the standard mass of the boson and V ν are the components of the wavefunction of the corresponding massive vector boson. Λ X is a very large energy scale, which is strongly constrained by equivalence principle tests, including lunar laser ranging [27] [28] and the EötWash experiment [29] [30] (see also [31] for constraints "
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    ABSTRACT: Scalar dark matter can interact with Standard Model (SM) particles, altering the fundamental constants of Nature in the process. Changes in the fundamental constants during and prior to Big Bang nucleosynthesis (BBN) produce changes in the primordial abundances of the light elements. By comparing the measured and calculated (within the SM) primordial abundance of $^{4}$He, which is predominantly determined by the ratio of the neutron-proton mass difference to freeze-out temperature at the time of weak interaction freeze-out prior to BBN, we are able to derive stringent constraints on the mass of a scalar dark matter particle $\phi$ together with its interactions with the photon, light quarks and massive vector bosons via quadratic couplings in $\phi$, as well as its interactions with massive vector bosons via linear couplings in $\phi$. We also derive a stringent constraint on the quadratic interaction of $\phi$ with the photon from recent atomic dysprosium spectroscopy measurements.
  • Source
    • "where the sum runs over all SM massive vector bosons V , M V is the standard mass of the boson and V ν are the components of the wavefunction of the corresponding massive vector boson. Λ X is a very large energy scale, which is strongly constrained by equivalence principle tests, including lunar laser ranging [27] [28] and the EötWash experiment [29] [30] (see also [31] for constraints "
    [Show abstract] [Hide abstract]
    ABSTRACT: Scalar dark matter can interact with Standard Model (SM) particles, altering the fundamental constants of Nature in the process. Changes in the fundamental constants during and prior to Big Bang nucleosynthesis (BBN) produce changes in the primordial abundances of the light elements. By comparing the measured and calculated (within the SM) primordial abundance of $^{4}$He, which is predominantly determined by the ratio of the neutron-proton mass difference to freeze-out temperature at the time of weak interaction freeze-out prior to BBN, we are able to derive stringent constraints on the mass of a scalar dark matter particle $\phi$ together with its interactions with the photon, light quarks and massive vector bosons via quadratic couplings in $\phi$, as well as its interactions with massive vector bosons via linear couplings in $\phi$. We also derive a stringent constraint on the quadratic interaction of $\phi$ with the photon from recent atomic dysprosium spectroscopy measurements.
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    • "The sounding-rocket based principle of equivalence measurement (SR-POEM) [Reasenberg et al. 2012] will determine η, the coefficient of equivalence principle violation, with an uncertainty of 2 × 10 −17 from a single flight. This will provide a four order of magnitude advance over the current best test [Schlamminger 2008, Wagner 2012] and two orders advance over the MICROSCOPE Mission which is now predicted to fly in 2016 [Touboul 2012]. An important spurious force in the SR-POEM experiment is electrostatic attraction between the test masses and their surroundings due to the presence of spatially varying surface potential known as the " patch effect. "
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    ABSTRACT: Experiments that measure extremely small gravitational forces are often hampered by the presence of non-gravitational forces that can neither be calculated nor separately measured. Among these spurious forces is electrostatic attraction between a test mass and its surroundings due to the presence of spatially varying surface potential known as the "patch effect." In order to make surfaces with small surface potential variation, it is necessary to be able to measure it. A Kelvin probe (KP) measures contact potential difference (CPD), using the time-varying capacitance between the sample and a vibrating tip that is biased with a backing potential. Assuming that the tip remains constant, this measures the sample's surface potential variation. We examine the operation of the KP from the perspective of parameter estimation in the presence of noise. We show that, when the CPD is estimated from measurements at two separate backing potentials, the standard deviation of the optimal estimate depends on the total observing time. Further, the observing time may be unevenly divided between the two backing potentials, provided the values of those potentials are correspondingly set. We simulate a two-stage KP data analysis, including a sub-optimal estimator with advantages for real-time operation. Based on the real-time version, we present a novel approach to stabilizing the average distance of the tip from the sample. We also present the results of a series of covariance analyses that validate and bound the applicability of the suboptimal estimator, make a comparison with the results of an optimal estimator and guide the user. We discuss the application of the KP to the LISA and to a test of the weak equivalence principle.
    Classical and Quantum Gravity 06/2013; 30(12). DOI:10.1088/0264-9381/30/12/125016 · 3.10 Impact Factor
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