1,551 research outputs found

    Precise mass-dependent QED contributions to leptonic g-2 at order alpha^2 and alpha^3

    Full text link
    Improved values for the two- and three-loop mass-dependent QED contributions to the anomalous magnetic moments of the electron, muon, and tau lepton are presented. The Standard Model prediction for the electron (g-2) is compared with its most precise recent measurement, providing a value of the fine-structure constant in agreement with a recently published determination. For the tau lepton, differences with previously published results are found and discussed. An updated value of the fine-structure constant is presented in "Note added after publication."Comment: 6 pages, 1 figure. v2: New determination of alpha presented (based on the recent electron g-2 measurement). v3: New formulae added in Sec.IIB. v4: Updated value of alpha presente

    Radiative penguin Bs decays at Belle

    Full text link
    We report searches for the radiative penguin decays Bs to phi gamma and Bs to gamma gamma based on a 23.6 fb-1 data sample collected with the Belle detector at the KEKB e+e- energy-asymmetric collider operating at the Upsilon(5S) resonance.Comment: On behalf of the Belle Collaboration. To appear in the proceedings of the International Europhysics Conference on High Energy Physics (EPS-HEP2007), Manchester, England, 19-25 July 2007. 3 pages, 2 figure

    Atom-wave diffraction between the Raman-Nath and the Bragg regime: Effective Rabi frequency, losses, and phase shifts

    Full text link
    We present an analytic theory of the diffraction of (matter) waves by a lattice in the "quasi-Bragg" regime, by which we mean the transition region between the long-interaction Bragg and "channelling" regimes and the short-interaction Raman-Nath regime. The Schroedinger equation is solved by adiabatic expansion, using the conventional adiabatic approximation as a starting point, and re-inserting the result into the Schroedinger equation to yield a second order correction. Closed expressions for arbitrary pulse shapes and diffraction orders are obtained and the losses of the population to output states otherwise forbidden by the Bragg condition are derived. We consider the phase shift due to couplings of the desired output to these states that depends on the interaction strength and duration and show how these can be kept negligible by a choice of smooth (e.g., Gaussian) envelope functions even in situations that substantially violate the adiabaticity condition. We also give an efficient method for calculating the effective Rabi frequency (which is related to the eigenvalues of Mathieu functions) in the quasi-Bragg regime.Comment: Minor additions, more concise text. To appear in Phys. Rev. A. 20 pages, 10 figure

    Frail aged persons residing in South African homes for the aged who require hospitalisation Part I. Urban areas

    Get PDF
    The numbers and characteristics of white residents identified by medical and nursing staff as requiring more staff time and/or expertise and/or medical equipment than is available in homes for the aged were assessed. Only 27 out of 2447 (1 1%) extremely infirm aged persons resident in 93 homes for the aged would, in the opinion of institutional staff, benefit by admission to a long-term care hospital catering for chronically ill. The conditions affecting these residents are described and recommendations relating to their management made

    Frail aged persons residing in South African' homes for the aged who require hospitalisation Part 11. Rural areas

    Get PDF
    The numbers and characteristics of white residents identified by medical and nursing staff to require more staff time and/or expertise and/or medical equipment than was available in rural homes for the aged in the Orange Free State were assessed. In the opinion of institution staff, 12,6% of extremely infirm aged persons would benefit by admission to a hospital catering for the chronically ill. The conditions affecting these residents are described and recommendations relating to their management are made

    A simple scheme for precise relative frequency stabilization of lasers

    Get PDF
    We present a simple scheme for tuneable relative frequency stabilization of lasers. A highly sensitive and accurate frequency-to-voltage converter is used to derive an error signal from the beat note between two lasers. We analyze in detail detector noise and drift, modulation detection bandwidth, and cross-talk from power modulation. The results indicate that sub-kHz relative linewidth and a locking point drift on the order of 100 Hz for times scales of 1 h are achievable. The scheme can, therefore, be applied to situations where up to now only optical PLLs could provide sufficient accuracy and precision. To demonstrate its potential for high-resolution, high-precision spectroscopy we lock a diode laser to a fs-frequency comb and find a relative linear drift of 314 Hz during a 2.8 h period

    Improved α4\alpha^4 Term of the Muon Anomalous Magnetic Moment

    Full text link
    We have completed the evaluation of all mass-dependent α4\alpha^4 QED contributions to the muon g2g-2, or aμa_\mu, in two or more different formulations. Their numerical values have been greatly improved by an extensive computer calculation. The new value of the dominant α4\alpha^4 term A2(8)(mμ/me)A_2^{(8)} (m_\mu / m_e) is 132.6823 (72), which supersedes the old value 127.50 (41). The new value of the three-mass term A3(8)(mμ/me,mμ/mτ)A_3^{(8)} (m_\mu / m_e, m_\mu / m_\tau) is 0.0376 (1). The term A2(8)(mμ/mτ)A_2^{(8)} (m_\mu / m_\tau) is crudely estimated to be about 0.005 and may be ignored for now. The total QED contribution to aμa_\mu is 116584719.58(0.02)(1.15)(0.85)×1011116 584 719.58 (0.02)(1.15)(0.85) \times 10^{-11}, where 0.02 and 1.15 are uncertainties in the α4\alpha^4 and α5\alpha^5 terms and 0.85 is from the uncertainty in α\alpha measured by atom interferometry. This raises the Standard Model prediction by 13.9×101113.9 \times 10^{-11}, or about 1/5 of the measurement uncertainty of aμa_\mu. It is within the noise of current uncertainty (100×1011\sim 100 \times 10^{-11}) in the estimated hadronic contributions to aμa_\mu.Comment: Appendix A has been rewritten extensively. It includes the 4th-order calculation for illustration. Version accepted by PR

    Improved α4\alpha^4 Term of the Electron Anomalous Magnetic Moment

    Full text link
    We report a new value of electron g2g-2, or aea_e, from 891 Feynman diagrams of order α4\alpha^4. The FORTRAN codes of 373 diagrams containing closed electron loops have been verified by at least two independent formulations. For the remaining 518 diagrams, which have no closed lepton loop, verification by a second formulation is not yet attempted because of the enormous amount of additional work required. However, these integrals have structures that allow extensive cross-checking as well as detailed comparison with lower-order diagrams through the renormalization procedure. No algebraic error has been uncovered for them. The numerical evaluation of the entire α4\alpha^4 term by the integration routine VEGAS gives 1.7283(35)(α/π)4-1.7283 (35) (\alpha/\pi)^4, where the uncertainty is obtained by careful examination of error estimates by VEGAS. This leads to ae=1159652175.86(0.10)(0.26)(8.48)×1012a_e = 1 159 652 175.86 (0.10) (0.26) (8.48) \times 10^{-12}, where the uncertainties come from the α4\alpha^4 term, the estimated uncertainty of α5\alpha^5 term, and the inverse fine structure constant, α1=137.0360003(10)\alpha^{-1} = 137.036 000 3 (10), measured by atom interferometry combined with a frequency comb technique, respectively. The inverse fine structure constant α1(ae)\alpha^{-1} (a_e) derived from the theory and the Seattle measurement of aea_e is 137.03599883(51)137.035 998 83 (51).Comment: 64 pages and 10 figures. Eq.(16) is corrected. Comments are added after Eq.(40

    High-accuracy Penning trap mass measurements with stored and cooled exotic ions

    Full text link
    The technique of Penning trap mass spectrometry is briefly reviewed particularly in view of precision experiments on unstable nuclei, performed at different facilities worldwide. Selected examples of recent results emphasize the importance of high-precision mass measurements in various fields of physics

    Optical Clocks in Space

    Get PDF
    The performance of optical clocks has strongly progressed in recent years, and accuracies and instabilities of 1 part in 10^18 are expected in the near future. The operation of optical clocks in space provides new scientific and technological opportunities. In particular, an earth-orbiting satellite containing an ensemble of optical clocks would allow a precision measurement of the gravitational redshift, navigation with improved precision, mapping of the earth's gravitational potential by relativistic geodesy, and comparisons between ground clocks.Comment: Proc. III International Conference on Particle and Fundamental Physics in Space (SpacePart06), Beijing 19 - 21 April 2006, to appear in Nucl. Phys.
    corecore