1,552 research outputs found
Precise mass-dependent QED contributions to leptonic g-2 at order alpha^2 and alpha^3
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
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
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
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
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
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 Term of the Muon Anomalous Magnetic Moment
We have completed the evaluation of all mass-dependent QED
contributions to the muon , or , in two or more different
formulations. Their numerical values have been greatly improved by an extensive
computer calculation. The new value of the dominant term is 132.6823 (72), which supersedes the old value 127.50 (41).
The new value of the three-mass term
is 0.0376 (1). The term is crudely estimated to
be about 0.005 and may be ignored for now. The total QED contribution to
is , where 0.02 and
1.15 are uncertainties in the and terms and 0.85 is from
the uncertainty in measured by atom interferometry. This raises the
Standard Model prediction by , or about 1/5 of the
measurement uncertainty of . It is within the noise of current
uncertainty () in the estimated hadronic
contributions to .Comment: Appendix A has been rewritten extensively. It includes the 4th-order
calculation for illustration. Version accepted by PR
Improved Term of the Electron Anomalous Magnetic Moment
We report a new value of electron , or , from 891 Feynman diagrams
of order . 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 term by
the integration routine VEGAS gives , where the
uncertainty is obtained by careful examination of error estimates by VEGAS.
This leads to ,
where the uncertainties come from the term, the estimated
uncertainty of term, and the inverse fine structure constant,
, measured by atom interferometry combined
with a frequency comb technique, respectively. The inverse fine structure
constant derived from the theory and the Seattle
measurement of is .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
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
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.
- …