The Experts below are selected from a list of 160542 Experts worldwide ranked by ideXlab platform
Tara M Fortier - One of the best experts on this subject based on the ideXlab platform.
-
precision Atomic Spectroscopy for improved limits on variation of the fine structure constant and local position invariance
Physical Review Letters, 2007Co-Authors: Tara M Fortier, Neil Ashby, J C Bergquist, M J Delaney, Scott A Diddams, T P Heavner, L Hollberg, W M Itano, S R JeffertsAbstract:We report tests of local position invariance and the variation of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground state hyperfine splitting in 133Cs. Analysis of the frequency ratio of the two clocks, extending over 6 yr at NIST, is used to place a limit on its fractional variation of <5.8x10(-6) per change in normalized solar gravitational potential. The same frequency ratio is also used to obtain 20-fold improvement over previous limits on the fractional variation of the fine structure constant of |alpha/alpha|<1.3x10(-16) yr-1, assuming invariance of other fundamental constants. Comparisons of our results with those previously reported for the absolute optical frequency measurements in H and 171Yb+ vs other 133Cs standards yield a coupled constraint of -1.5x10(-15)
-
precision Atomic Spectroscopy for improved limits on variation of the fine structure constant and local position invariance
Physical Review Letters, 2007Co-Authors: Tara M Fortier, Neil Ashby, J C Bergquist, M J Delaney, Scott A Diddams, T P Heavner, L Hollberg, W M Itano, S R Jefferts, Kyoungsik KimAbstract:Measurements comparing the relative rates of two Atomic clocks that are based on very narrow transitions between well-resolved and relatively unperturbed Atomic energy levels currently report among the highest precision attained for any fundamental quantity. Such measurements, which can yield greater than 15 digits of frequency accuracy, permit tests of fundamental postulates of physics, including searches for variations of fundamental constants. In this Letter, we analyze measurements of the frequency
Julian J Krauth - One of the best experts on this subject based on the ideXlab platform.
-
Measuring the α-particle charge radius with muonic helium-4 ions
Nature, 2021Co-Authors: Julian J Krauth, Karsten Schuhmann, Marwan Abdou Ahmed, Pedro Amaro, Francois Biraben, Tzuling Chen, Fernando Amaro, Daniel Covita, Andreas Dax, Marc DiepoldAbstract:The energy levels of hydrogen-like Atomic systems can be calculated with great precision. Starting from their quantum mechanical solution, they have been refined over the years to include the electron spin, the relativistic and quantum field effects, and tiny energy shifts related to the complex structure of the nucleus. These energy shifts caused by the nuclear structure are vastly magnified in hydrogen-like systems formed by a negative muon and a nucleus, so Spectroscopy of these muonic ions can be used to investigate the nuclear structure with high precision. Here we present the measurement of two 2S–2P transitions in the muonic helium-4 ion that yields a precise determination of the root-mean-square charge radius of the α particle of 1.67824(83) femtometres. This determination from Atomic Spectroscopy is in excellent agreement with the value from electron scattering, but a factor of 4.8 more precise, providing a benchmark for few-nucleon theories, lattice quantum chromodynamics and electron scattering. This agreement also constrains several beyond-standard-model theories proposed to explain the proton-radius puzzle, in line with recent determinations of the proton charge radius, and establishes Spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties.
-
measuring the α particle charge radius with muonic helium 4 ions
Nature, 2021Co-Authors: Julian J Krauth, Karsten Schuhmann, Marwan Abdou Ahmed, F D Amaro, Pedro Amaro, Francois Biraben, Tzuling ChenAbstract:The energy levels of hydrogen-like Atomic systems can be calculated with great precision. Starting from their quantum mechanical solution, they have been refined over the years to include the electron spin, the relativistic and quantum field effects, and tiny energy shifts related to the complex structure of the nucleus. These energy shifts caused by the nuclear structure are vastly magnified in hydrogen-like systems formed by a negative muon and a nucleus, so Spectroscopy of these muonic ions can be used to investigate the nuclear structure with high precision. Here we present the measurement of two 2S–2P transitions in the muonic helium-4 ion that yields a precise determination of the root-mean-square charge radius of the α particle of 1.67824(83) femtometres. This determination from Atomic Spectroscopy is in excellent agreement with the value from electron scattering1, but a factor of 4.8 more precise, providing a benchmark for few-nucleon theories, lattice quantum chromodynamics and electron scattering. This agreement also constrains several beyond-standard-model theories proposed to explain the proton-radius puzzle2–5, in line with recent determinations of the proton charge radius6–9, and establishes Spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties. The 2S–2P transitions in muonic helium-4 ions are measured using laser Spectroscopy and used to obtain an α-particle charge-radius value five times more precise than that from electron scattering.
S R Jefferts - One of the best experts on this subject based on the ideXlab platform.
-
precision Atomic Spectroscopy for improved limits on variation of the fine structure constant and local position invariance
Physical Review Letters, 2007Co-Authors: Tara M Fortier, Neil Ashby, J C Bergquist, M J Delaney, Scott A Diddams, T P Heavner, L Hollberg, W M Itano, S R JeffertsAbstract:We report tests of local position invariance and the variation of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground state hyperfine splitting in 133Cs. Analysis of the frequency ratio of the two clocks, extending over 6 yr at NIST, is used to place a limit on its fractional variation of <5.8x10(-6) per change in normalized solar gravitational potential. The same frequency ratio is also used to obtain 20-fold improvement over previous limits on the fractional variation of the fine structure constant of |alpha/alpha|<1.3x10(-16) yr-1, assuming invariance of other fundamental constants. Comparisons of our results with those previously reported for the absolute optical frequency measurements in H and 171Yb+ vs other 133Cs standards yield a coupled constraint of -1.5x10(-15)
-
precision Atomic Spectroscopy for improved limits on variation of the fine structure constant and local position invariance
Physical Review Letters, 2007Co-Authors: Tara M Fortier, Neil Ashby, J C Bergquist, M J Delaney, Scott A Diddams, T P Heavner, L Hollberg, W M Itano, S R Jefferts, Kyoungsik KimAbstract:Measurements comparing the relative rates of two Atomic clocks that are based on very narrow transitions between well-resolved and relatively unperturbed Atomic energy levels currently report among the highest precision attained for any fundamental quantity. Such measurements, which can yield greater than 15 digits of frequency accuracy, permit tests of fundamental postulates of physics, including searches for variations of fundamental constants. In this Letter, we analyze measurements of the frequency
Pascalutsa Vladimir - One of the best experts on this subject based on the ideXlab platform.
-
Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: II. Spin polarizabilities and moments of polarized structure functions
'American Physical Society (APS)', 2021Co-Authors: Alarcón, Jose Manuel, Hagelstein Franziska, Lensky Vadim, Pascalutsa VladimirAbstract:We examine the polarized doubly-virtual Compton scattering (VVCS) off the nucleon using chiral perturbation theory ($\chi$PT). The polarized VVCS contains a wealth of information on the spin structure of the nucleon which is relevant to the calculation of the two-photon-exchange effects in Atomic Spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of the polarized VVCS amplitudes $S_1(\nu, Q^2)$ and $S_2(\nu, Q^2)$, and the corresponding polarized spin structure functions $g_1(x, Q^2)$ and $g_2(x,Q^2)$. Our results for the moments of polarized structure functions, partially related to different spin polarizabilities, are compared to other theoretical predictions and "data-driven" evaluations, as well as to the recent Jefferson Lab measurements. By expanding the results in powers of the inverse nucleon mass, we reproduce the known "heavy-baryon" expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant baryon $\chi$PT (B$\chi$PT) and heavy-baryon (HB$\chi$PT) frameworks.Comment: 47 pages, 11 figures, 2 tables. Includes Mathematica notebook with the spin polarizabilities and moments of polarized structure functions as supplemental material. Replaced to match the published versio
-
Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: The subtraction function and moments of unpolarized structure functions
'American Physical Society (APS)', 2020Co-Authors: Alarcón, Jose Manuel, Hagelstein Franziska, Lensky Vadim, Pascalutsa VladimirAbstract:The forward doubly-virtual Compton scattering (VVCS) off the nucleon contains a wealth of information on nucleon structure, relevant to the calculation of the two-photon-exchange effects in Atomic Spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of low-energy VVCS in chiral perturbation theory (χPT). Here we focus on the unpolarized VVCS amplitudes T1ðν;Q2Þ and T2ðν;Q2Þ, and the corresponding structure functions F1ðx;Q2Þ and F2ðx;Q2Þ. Our results are confronted, where possible, with “data-driven” dispersive evaluations of low- energy structure quantities, such as nucleon polarizabilities. We find significant disagreements with dispersive evaluations at very low momentum-transfer Q; for example, in the slope of polarizabilities at zero momentum transfer. By expanding the results in powers of the inverse nucleon mass, we reproduce the known “heavy-baryon” expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant (BχPT) and heavy-baryon (HBχPT) frameworks
-
Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: II. Spin polarizabilities and moments of polarized structure functions
2020Co-Authors: Alarcón, Jose Manuel, Hagelstein Franziska, Lensky Vadim, Pascalutsa VladimirAbstract:We examine the polarized doubly-virtual Compton scattering (VVCS) off the nucleon using chiral perturbation theory ($\chi$PT). The polarized VVCS contains a wealth of information on the spin structure of the nucleon which is relevant to the calculation of the two-photon-exchange effects in Atomic Spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of the polarized VVCS amplitudes $S_1(\nu, Q^2)$ and $S_2(\nu, Q^2)$, and the corresponding polarized spin structure functions $g_1(x, Q^2)$ and $g_2(x,Q^2)$. Our results for the moments of polarized structure functions, partially related to different spin polarizabilities, are compared to other theoretical predictions and "data-driven" evaluations, as well as to the recent Jefferson Lab measurements. By expanding the results in powers of the inverse nucleon mass, we reproduce the known "heavy-baryon" expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant baryon $\chi$PT (B$\chi$PT) and heavy-baryon (HB$\chi$PT) frameworks.Comment: 47 pages, 11 figures, 2 tables. Includes Mathematica notebook with the spin polarizabilities and moments of polarized structure functions as supplemental materia
-
Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: the subtraction function and moments of unpolarized structure functions
'American Physical Society (APS)', 2020Co-Authors: Alarcón, Jose Manuel, Hagelstein Franziska, Lensky Vadim, Pascalutsa VladimirAbstract:The forward doubly-virtual Compton scattering (VVCS) off the nucleon contains a wealth of information on nucleon structure, relevant to the calculation of the two-photon-exchange effects in Atomic Spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of low-energy VVCS in chiral perturbation theory ($\chi$PT). Here we focus on the unpolarized VVCS amplitudes $T_1(\nu, Q^2)$ and $T_2(\nu, Q^2)$, and the corresponding structure functions $F_1(x, Q^2)$ and $F_2(x,Q^2)$. Our results are confronted, where possible, with "data-driven" dispersive evaluations of low-energy structure quantities, such as nucleon polarizabilities. We find significant disagreements with dispersive evaluations at very low momentum-transfer $Q$; for example, in the slope of polarizabilities at zero momentum-transfer. By expanding the results in powers of the inverse nucleon mass, we reproduce the known "heavy-baryon" expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant (B$\chi$PT) and heavy-baryon (HB$\chi$PT) frameworks.Comment: 31 pages, 11 figures, 1 table; supplemented material: 1 Mathematica notebook; minor modifications, published versio
Dmitry Budker - One of the best experts on this subject based on the ideXlab platform.
-
scalar dark matter in the radio frequency band Atomic Spectroscopy search results
Physical Review Letters, 2019Co-Authors: Dionysios Antypas, Oleg Tretiak, Antoine Garcon, Roee Ozeri, Gilad Perez, Dmitry BudkerAbstract:Among the prominent candidates for dark matter are bosonic fields with small scalar couplings to the standard-model particles. Several techniques are employed to search for such couplings, and the current best constraints are derived from tests of gravity or Atomic probes. In experiments employing atoms, observables would arise from expected dark-matter-induced oscillations in the fundamental constants of nature. These studies are primarily sensitive to underlying particle masses below ${10}^{\ensuremath{-}14}\text{ }\text{ }\mathrm{eV}$. We present a method to search for fast oscillations of fundamental constants using Atomic Spectroscopy in cesium vapor. We demonstrate sensitivity to scalar interactions of dark matter associated with a particle mass in the range $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ to $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\text{ }\text{ }\mathrm{eV}$. In this range our experiment yields constraints on such interactions, which within the framework of an astronomical-size dark matter structure are comparable with, or better than, those provided by experiments probing deviations from the law of gravity.
-
search for ultralight scalar dark matter with Atomic Spectroscopy
Physical Review Letters, 2015Co-Authors: Ken Van Tilburg, Nathan Leefer, Dmitry Budker, Lykourgos BougasAbstract:We report new limits on ultralight scalar dark matter (DM) with dilatonlike couplings to photons that can induce oscillations in the fine-structure constant α. Atomic dysprosium exhibits an electronic structure with two nearly degenerate levels whose energy splitting is sensitive to changes in α. Spectroscopy data for two isotopes of dysprosium over a two-year span are analyzed for coherent oscillations with angular frequencies below 1 rad s-1. No signal consistent with a DM coupling is identified, leading to new constraints on dilatonlike photon couplings over a wide mass range. Under the assumption that the scalar field comprises all of the DM, our limits on the coupling exceed those from equivalence-principle tests by up to 4 orders of magnitude for masses below 3×10(-18) eV. Excess oscillatory power, inconsistent with fine-structure variation, is detected in a control channel, and is likely due to a systematic effect. Our Atomic Spectroscopy limits on DM are the first of their kind, and leave substantial room for improvement with state-of-the-art Atomic clocks.