Improved tests of Local Position Invariance using 87Rb and 133Cs fountains

We report tests of local position invariance based on measurements of the ratio of the ground state hyperfine frequencies of 133Cs and 87Rb in laser-cooled atomic fountain clocks. Measurements extending over 14 years set a stringent limit to a possible variation with time of this ratio: d ln(nu_Rb/nu_Cs)/dt=(-1.39 +/- 0.91)x 10-16 yr-1. This improves by a factor of 7.7 over our previous report (H. Marion et al., Phys. Rev. Lett. 90, 150801 (2003)). Our measurements also set the first limit to a fractional variation of the Rb/Cs ratio with gravitational potential at the level of c^2 d ln(nu_Rb/nu_Cs)/dU=(0.11 +/- 1.04)x 10^-6, providing a new stringent differential redshift test. The above limits equivalently apply to the fractional variation of the quantity alpha^{-0.49}x(g_Rb/g_Cs), which involves the fine structure constant alpha and the ratio of the nuclear g-factors of the two alkalis. The link with variations of the light quark mass is also presented together with a global analysis combining with other available highly accurate clock comparisons.Comment: 5 pages, 3 figures, 3 tables, 34 reference

AC Stark shift of the Cs microwave atomic clock transitions

We analyze the AC Stark shift of the Cs microwave atomic clock transition theoretically and experimentally. Theoretical and experimental data are in a good agreement with each other. Results indicate the absence of a magic wavelength at which there would be no differential shift of the clock states having zero projections of the total angular momentum

Progress in Atomic Fountains at LNE-SYRTE

We give an overview of the work done with the Laboratoire National de M\'etrologie et d'Essais-Syst\`emes de R\'ef\'erence Temps-Espace (LNE-SYRTE) fountain ensemble during the last five years. After a description of the clock ensemble, comprising three fountains, FO1, FO2, and FOM, and the newest developments, we review recent studies of several systematic frequency shifts. This includes the distributed cavity phase shift, which we evaluate for the FO1 and FOM fountains, applying the techniques of our recent work on FO2. We also report calculations of the microwave lensing frequency shift for the three fountains, review the status of the blackbody radiation shift, and summarize recent experimental work to control microwave leakage and spurious phase perturbations. We give current accuracy budgets. We also describe several applications in time and frequency metrology: fountain comparisons, calibrations of the international atomic time, secondary representation of the SI second based on the 87Rb hyperfine frequency, absolute measurements of optical frequencies, tests of the T2L2 satellite laser link, and review fundamental physics applications of the LNE-SYRTE fountain ensemble. Finally, we give a summary of the tests of the PHARAO cold atom space clock performed using the FOM transportable fountain.Comment: 19 pages, 12 figures, 5 tables, 126 reference

Atomic fountains and optical clocks at SYRTE: status and perspectives

In this article, we report on the work done with the LNE-SYRTE atomic clock ensemble during the last 10 years. We cover progress made in atomic fountains and in their application to timekeeping. We also cover the development of optical lattice clocks based on strontium and on mercury. We report on tests of fundamental physical laws made with these highly accurate atomic clocks. We also report on work relevant to a future possible redefinition of the SI second

Social Ball: An immersive research paradigm to study social ostracism

We introduce “Social Ball,” a new research paradigm to study ostracism via an online ball tossing game based on Cyberball (Williams & Jarvis, 2006) designed with both researchers and participants in mind. For researchers, the game incorporates a variety of features which are easily accessible from the software’s interface. Some of these features have already been studied with Cyberball (e.g., tossing different objects) but some are novel (e.g., end-game communication or hand-waving during the game). From the participants’ perspective, the game was designed to be more visually and socially immersive to create a more video-game- like online environment. We discuss two previous implementations. Study 1 showed that Social Ball successfully induced need threat and negative affect among ostracized (vs included) participants (n = 247). Study 2 empirically demonstrated how a new feature of the game (i.e., hand-waving) can be used to answer various questions. The results suggested that people waved their hands to varying degrees yet the frequency of which was not associated with post game need satisfaction (n = 2578). Besides describing the features of the game, we also provide a configuration manual and an annotated R code (both as online supplementary materials) to make the paradigm and associated analyses more accessible, and in turn, to stimulate further research. In our discussion, we elaborate on the various ways in which Social Ball can contribute to the understanding of belonging and ostracism

Q-Value and Half-Lives for the Double-Beta-Decay Nuclide 110Pd

The 110Pd double-beta decay Q-value was measured with the Penning-trap mass spectrometer ISOLTRAP to be Q = 2017.85(64) keV. This value shifted by 14 keV compared to the literature value and is 17 times more precise, resulting in new phase-space factors for the two-neutrino and neutrinoless decay modes. In addition a new set of the relevant matrix elements has been calculated. The expected half-life of the two-neutrino mode was reevaluated as 1.5(6) E20 yr. With its high natural abundance, the new results reveal 110Pd to be an excellent candidate for double-beta decay studies

Precision Mass Measurements of 129-131Cd and Their Impact on Stellar Nucleosynthesis via the Rapid Neutron Capture Process

Masses adjacent to the classical waiting-point nuclide 130Cd have been measured by using the Penning- trap spectrometer ISOLTRAP at ISOLDE/CERN. We find a significant deviation of over 400 keV from earlier values evaluated by using nuclear beta-decay data. The new measurements show the reduction of the N = 82 shell gap below the doubly magic 132Sn. The nucleosynthesis associated with the ejected wind from type-II supernovae as well as from compact object binary mergers is studied, by using state-of-the-art hydrodynamic simulations. We find a consistent and direct impact of the newly measured masses on the calculated abundances in the A = 128 - 132 region and a reduction of the uncertainties from the precision mass input data

Three-dimensional vortex configurations in a rotating Bose Einstein condensate

We consider a rotating Bose-Einstein condensate in a harmonic trap and investigate numerically the behavior of the wave function which solves the Gross Pitaevskii equation. Following recent experiments [Rosenbuch et al, Phys. Rev. Lett., 89, 200403 (2002)], we study in detail the line of a single quantized vortex, which has a U or S shape. We find that a single vortex can lie only in the x-z or y-z plane. S type vortices exist for all values of the angular velocity Omega while U vortices exist for Omega sufficiently large. We compute the energy of the various configurations with several vortices and study the three-dimensional structure of vortices

Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K

The recently confirmed neutron-shell closure at N = 32 has been investigated for the first time below the magic proton number Z = 20 with mass measurements of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide investigated at the online mass spectrometer ISOLTRAP. The resulting two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly lower than for 52Ca, highlighting the doubly-magic nature of this nuclide. Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations are challenged by the new measurements but reproduce qualitatively the observed shell effect.Comment: 5 pages, 5 figure