Time variation of the fine structure constant $\alpha$ from realistic models of Oklo reactors.

ORAL

Abstract

The topic of whether the fundamental constants of nature vary with time has been a subject of great interest since Dirac originally proposed the possibility that $G_N \sim 1/t_{universe}$. Recent observations of absorption spectra lines from distant quasars appeared to indicate a possible increase in the fine structure constant $\alpha$ over ten billion years. Contrarily, analyses of the time evolution of $\alpha$ from Oklo natural nuclear reactor data have yielded inconsistent results, some indicating a decrease over two billion years while others indicated no change. We have used known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Reactors RZ2 and RZ10 were modeled with MCNP and the resulting neutron spectra were used to calculate the change in the $^{149}$Sm capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. Our study resolves the contradictory situation with previous Oklo $\alpha$-results. Our suggested $2 \sigma$ bound on a possible time variation of $\alpha$ over two billion years is stringent: $ -0.11 \le \frac{\Delta \alpha}{\alpha} \le 0.24$, in units of $10^{-7}$, but model dependent in that it assumes only $\alpha$ has varied over time.

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Authors

  • C.R. Gould

    NC State U and TUNL

  • J. Deng

    US Naval Observatory, University of Virginia, Thomas Jefferson National Accelerator Facility, College of William and Mary, US Army Research Office, Brimrose Corporation of America, Hampton University, Department of Physics, University of Rajshahi, Rajshahi, Bangladesh, Department of Physics, Old Dominion University, Norfolk, VA 23529, University of North Carolina at Chapel Hill, Department of Physics, Old Dominion University, Norfolk, Virginia, Department of Physics, Korea University, Seoul, Korea, Department of Physics, University of Virginia, Charlottesville, VA, Department of Physics, Old Dominion University, Norfolk, VA, North Carolina State University and WebAssign, Raleigh, NC, North Carolina State University, Raleigh, NC, Broughton High School, Raleigh, NC, University of Wisconsin at Whitewater, Whitewater, WI, University of North Carolina-Chapel Hill Department of Physics, University of West Virginia - Chemistry Dept., ORNL, Old Dominion University, University of West Virginia Department of Chemistry, Clemson University, South Carolina Governor’s School for Science and Mathematics, College of Charleston, Rice University, Korea Research Institute of Standards and Science, Ohio State University, Wright State University, Yale U, JINR, Dubna, Univ. Fed. do Rio de Janeiro, Vanderbilt Univ./JIHIR(ORNL)/Tsinghua Univ., NSCL(MSU), LLNL, LBNL, Vanderbilt Univ./LBNL/JIHIR(ORNL), Vanderbilt Univ., Jagellonian University, University of Bonn, North Carolina A{\&T} State University, North Carolina Central University, Duke University and TUNL

  • J. Deng

    US Naval Observatory, University of Virginia, Thomas Jefferson National Accelerator Facility, College of William and Mary, US Army Research Office, Brimrose Corporation of America, Hampton University, Department of Physics, University of Rajshahi, Rajshahi, Bangladesh, Department of Physics, Old Dominion University, Norfolk, VA 23529, University of North Carolina at Chapel Hill, Department of Physics, Old Dominion University, Norfolk, Virginia, Department of Physics, Korea University, Seoul, Korea, Department of Physics, University of Virginia, Charlottesville, VA, Department of Physics, Old Dominion University, Norfolk, VA, North Carolina State University and WebAssign, Raleigh, NC, North Carolina State University, Raleigh, NC, Broughton High School, Raleigh, NC, University of Wisconsin at Whitewater, Whitewater, WI, University of North Carolina-Chapel Hill Department of Physics, University of West Virginia - Chemistry Dept., ORNL, Old Dominion University, University of West Virginia Department of Chemistry, Clemson University, South Carolina Governor’s School for Science and Mathematics, College of Charleston, Rice University, Korea Research Institute of Standards and Science, Ohio State University, Wright State University, Yale U, JINR, Dubna, Univ. Fed. do Rio de Janeiro, Vanderbilt Univ./JIHIR(ORNL)/Tsinghua Univ., NSCL(MSU), LLNL, LBNL, Vanderbilt Univ./LBNL/JIHIR(ORNL), Vanderbilt Univ., Jagellonian University, University of Bonn, North Carolina A{\&T} State University, North Carolina Central University, Duke University and TUNL