465 research outputs found

    Limit on the Temporal Variation of the Fine-Structure Constant Using Atomic Dysprosium

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    Over a period of eight months, we have monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These transition frequencies are highly sensitive to temporal variation of the fine-structure constant (α\alpha) due to relativistic corrections of large and opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a radio-frequency (rf) electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in 163^{163}Dy and the 235-MHz transition in 162^{162}Dy are 9.0±\pm6.7 Hz/yr and -0.6±\pm6.5 Hz/yr, respectively. These results provide a value for the rate of fractional variation of α\alpha of (−2.7±2.6)×10−15(-2.7\pm2.6)\times 10^{-15} yr−1^{-1} (1 σ\sigma) without any assumptions on the constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity.Comment: 4 pages, 2 figure

    New constraints for non-Newtonian gravity in nanometer range from the improved precision measurement of the Casimir force

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    We obtain constraints on non-Newtonian gravity following from the improved precision measurement of the Casimir force by means of atomic force microscope. The hypothetical force is calculated in experimental configuration (a sphere above a disk both covered by two metallic layers). The strengthenings of constraints up to 4 times comparing the previous experiment and up to 560 times comparing the Casimir force measurements between dielectrics are obtained in the interaction range 5.9 nm≀λ≀115\leq\lambda\leq 115 nm. Recent speculations about the presence of some unexplained attractive force in the considered experiment are shown to be unjustified.Comment: 5 pages, 1 figur

    Stiction, Adhesion Energy and the Casimir Effect in Micromechanical Systems

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    We measure the adhesion energy of gold using a micromachined doubly-clamped beam. The stress and stiffness of the beam are characterized by measuring the spectrum of mechanical vibrations and the deflection due to an external force. To determine the adhesion energy we induce stiction between the beam and a nearby surface by capillary forces. Subsequent analysis yields a value Îł=0.06\gamma =0.06 J/m2^{2} that is a factor of approximately six smaller than predicted by idealized theory. This discrepancy may be resolved with revised models that include surface roughness and the effect of adsorbed monolayers intervening between the contacting surfaces in these mesoscopic structures.Comment: RevTex, 4 pages, 4 eps figure

    Neutron-Electron EDM Correlations in Supersymmetry and Prospects for EDM Searches

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    Motivated by recent progress in experimental techniques of electric dipole moment (EDM) measurements, we study correlations between the neutron and electron EDMs in common supersymmetric models. These include minimal supergravity (mSUGRA) with small CP phases, mSUGRA with a heavy SUSY spectrum, the decoupling scenario and split SUSY. In most cases, the electron and neutron EDMs are found to be observable in the next round of EDM experiments. They exhibit certain correlation patterns. For example, if d_n ~ 10^{-27} e cm is found, d_e is predicted to lie in the range 10^{-28}-10^{-29} e cm.Comment: 16 pages,12 figures. To appear in JHEP. A note on stability of the correlations added in Conclusions; refs. and footnotes adde

    New Experimental Limit on the Electric Dipole Moment of the Electron in a Paramagnetic Insulator

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    We report results of an experimental search for the intrinsic Electric Dipole Moment (EDM) of the electron using a solid-state technique. The experiment employs a paramagnetic, insulating gadolinium gallium garnet (GGG) that has a large magnetic response at low temperatures. The presence of the eEDM would lead to a small but non-zero magnetization as the GGG sample is subject to a strong electric field. We search for the resulting Stark-induced magnetization with a sensitive magnetometer. Recent progress on the suppression of several sources of background allows the experiment to run free of spurious signals at the level of the statistical uncertainties. We report our first limit on the eEDM of (−5.57±7.98±0.12)×(-5.57 \pm 7.98 \pm 0.12)\times10−25^{-25}e⋅\cdotcm with 5 days of data averaging.Comment: 9 pages, 9 figures, Revtex 4.

    Variation of the Fine-Structure Constant and Laser Cooling of Atomic Dysprosium

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    Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, α\alpha. The data provide a rate of fractional temporal variation of α\alpha of (−2.4±2.3)×10−15(-2.4\pm2.3)\times10^{-15} yr−1^{-1} or a value of (−7.8±5.9)×10−6(-7.8 \pm 5.9) \times 10^{-6} for kαk_\alpha, the variation coefficient for α\alpha in a changing gravitational potential. All results indicate the absence of significant variation at the present level of sensitivity. We also present initial results on laser cooling of an atomic beam of dysprosium.Comment: 10 pages, 6 figures, fixed typos in section 5, updated result

    Investigation of the Gravitational Potential Dependence of the Fine-Structure Constant Using Atomic Dysprosium

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    Radio-frequency E1 transitions between nearly degenerate, opposite parity levels of atomic dysprosium were monitored over an eight month period to search for a variation in the fine-structure constant. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of (−8.7±6.6)×10−6(-8.7 \pm 6.6) \times 10^{-6} for the fit parameter kαk_\alpha. This value gives the current best laboratory limit. In addition, our value of kαk_{\alpha} combined with other experimental constraints is used to extract the first limits on k_e and k_q. These coefficients characterize the variation of m_e/m_p and m_q/m_p in a changing gravitational potential, where m_e, m_p, and m_q are electron, proton, and quark masses. The results are ke=(4.9±3.9)×10−5k_e = (4.9 \pm 3.9) \times 10^{-5} and kq=(6.6±5.2)×10−5k_q = (6.6 \pm 5.2) \times 10^{-5}.Comment: 6 pages, 3 figure

    CP violation in 5D Split Fermions Scenario

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    We give a new configuration of split fermion positions in one extra dimension with two different Yukawa coupling strengths for up-type, huh_u, and down-type, hdh_d, quarks at huhd=36.0\frac{h_u}{h_d}=36.0. The new configurations can give enough CP violating (CPV) phase for accommodating all currently observed CPV processes. Therefore, a 5D standard model with split fermions is viable. In addition to the standard CKM phase, new CPV sources involving Kaluza-Klein(KK) gauge bosons coupling which arise from the fact that unitary rotation which transforms weak eigenstates into their mass eigenstates only holds for the zero modes which are the SM fields and not for the KK excitations. We have examined the physics of kaon, neutron, and B/DB/D mesons and found the most stringent bound on the size RR of the extra dimension comes from âˆŁÏ”K∣|\epsilon_K|. Moreover, it depends sensitively on the width, σ\sigma, of the Gaussian wavefunction in the extra dimension used to describe of the fermions. When σ/Râ‰Ș1\sigma/R \ll 1, the constraint will be lifted due to GIM suppression on the flavor changing neutral current(FCNC) and CPV couplings.Comment: 24 pages, 8 figure
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