7,791 research outputs found
On the Hadronic Contribution to Light-by-light Scattering in
We comment on the theoretical uncertainties involved in estimating the
hadronic effects on the light-by-light scattering contribution to the anomalous
magnetic moment of the muon, especially based on the analysis and results of T.
Kinoshita, B. Ni\v zi\'c, and Y. Okamoto, Phys.\ Rev.\ D31, 2108 (1985). From
the point of view of an effective field theory and chiral perturbation theory,
we suggest that the charged pion contribution may be better determined than has
been appreciated. However, the neutral pion contribution needs greater
theoretical insight before its magnitude can be reliably estimated.Comment: 9 pages, no figures, U. Michigan UM-TH-93-18. (Input phyzzm to
compile.) Revised version has minor changes in text. To be published in Phys.
Rev. D, Comments sectio
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
Electroweak Fermion-loop Contributions to the Muon Anomalous Magnetic Moment
The two-loop electroweak corrections to the anomalous magnetic moment of the
muon, generated by fermionic loops, are calculated. An interesting role of the
top quark in the anomaly cancellation is observed. New corrections, including
terms of order , are computed and a class of diagrams
previously thought to vanish are found to be important. The total fermionic
correction is which decreases the electroweak
effects on , predicted from one-loop calculations, by 12\%. We give an
updated theoretical prediction for of the muon.Comment: Corrected versio
Everyone Makes Mistakes - Including Feynman
This talk is dedicated to Alberto Sirlin in celebration of his seventieth
birthday. I wish to convey my deep appreciation of his many important
contributions to particle physics over 40 years and look forward to many more
years of productive research.Comment: 16 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
A precise modeling of Phoebe's rotation
Although the rotation of some Saturn's satellites in spin-orbit has already
been studied by several authors, this is not the case of the rotation of
Phoebe, which has the particularity of being non resonant. The purpose of the
paper is to determine for the first time and with precision its
precession-nutation motion. We adopt an Hamiltonian formalism of the motion of
rotation of rigid celestial body set up by Kinoshita (1977) based on Andoyer
variables and canonical equations. First we calculate Phoebe's obliquity at
J2000,0 from available astronomical data as well as the gravitational
perturbation due to Saturn on Phoebe rotational motion. Then we carry out a
numerical integration and we compare our results for the precession rate and
the nutation coefficients with pure analytical model. Our results for Phoebe
obliquity (23{\deg}95) and Phoebe precession rate (5580".65/cy) are very close
to the respective values for the Earth. Moreover the amplitudes of the
nutations (26" peak to peak for the nutaton in longitude and 8" for the
nutation in obliquity) are of the same order as the respective amplitudes for
the Earth. We give complete tables of nutation, obtained from a FFT analysis
starting from the numerical signals. We show that a pure analytical model of
the nutation is not accurate due to the fact that Phoebe orbital elements e, M
and Ls are far from having a simple linear behaviour. The precession and
nutation of Phoebe have been calculated for the first time in this paper. We
should keep on the study in the future by studying the additional gravitational
effects of the Sun, of the large satellites as Titan, as well as Saturn
dynamical ellipticity.Comment: 11 pages,15 figures, accepted for publication in A&
Features of gravitational waves in higher dimensions
There are several fundamental differences between four-dimensional and
higher-dimensional gravitational waves, namely in the so called braneworld
set-up. One of them is their asymptotic behavior within the Cauchy problem.
This study is connected with the so called Hadamard problem, which aims at the
question of Huygens principle validity. We investigate the effect of braneworld
scenarios on the character of propagation of gravitational waves on FRW
background.Comment: to appear in ERE09 proceeding
Radiative corrections to muon decay in leading and next to leading approximation for electron spectrum
We have noted that the electron spectrum of muon decay in the leading
logarithmic approximation calculated in two lowest orders of the perturbation
theory in the paper of Berman (1958), can be reproduced by the parton language.
This fact permits one to generalize the result to all orders of the
perturbation theory using the structure function method.Comment: 4 pages, 1 figur
Double logarithmical corrections to beam asymmetry in polarized electron-proton scattering
The up-down asymmetry in transversally polarized electron proton scattering
is induced by the interference between one and two photon exchange amplitudes.
Inelastic intermediate hadronic states (different from one-proton state) of the
two photon exchange amplitude give rise to contributions containing the square
of "large logarithm" (logarithm of the ratio of the transferred momentum to the
electron mass). We investigate the presence of such contributions in higher
orders of perturbation theory. The relation with the case of zero transfer
momentum is explicitly given. The mechanism of cancellation of infrared
singularities is discussed.Comment: 9 pages, 8 figure
Lattice calculation of the lowest order hadronic contribution to the muon anomalous magnetic moment
We present a quenched lattice calculation of the lowest order (alpha^2)
hadronic contribution to the anomalous magnetic moment of the muon which arises
from the hadronic vacuum polarization. A general method is presented for
computing entirely in Euclidean space, obviating the need for the usual
dispersive treatment which relies on experimental data for e^+e^- annihilation
to hadrons. While the result is not yet of comparable accuracy to those
state-of-the-art calculations, systematic improvement of the quenched lattice
computation to this level of accuracy is straightforward and well within the
reach of present computers. Including the effects of dynamical quarks is
conceptually trivial, the computer resources required are not.Comment: 12 pages, including two figures. Added reference and footnote
Replaced with published version; minor changes asked for by referees and
minor deletions to stay within page limi
Interaction specificity of Arabidopsis 14-3-3 proteins with phototropin receptor kinases
Phototropin receptor kinases play an important roles in optimising plant growth in response to blue light. Much is known regarding their photochemical reactivity, yet little progress has been made to identify downstream signalling components. Here, we isolated several interacting proteins for Arabidopsis phototropin 1 (phot1) by yeast two-hybrid screening. These include members of the NPH3/RPT2 (NRL) protein family, proteins associated with vesicle trafficking, and the 14-3-3 lambda (?) isoform from Arabidopsis . 14-3-3? and phot1 were found to colocalise and interact in vivo. Moreover, 14-3-3 binding to phot1 was limited to non-epsilon 14-3-3 isoforms and was dependent on key sites of receptor autophosphorylation. No 14-3-3 binding was detected for Arabidopsis phot2, suggesting that 14-3-3 proteins represent specific mode of phot1 signalling
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