56,423 research outputs found
Low Energy Precision Test of Supersymmetry
Supersymmetry (SUSY) remains one of the leading candidates for physics beyond
the Standard Model, and the search for SUSY will be a central focus of future
collider experiments. Complementary information on the viability and character
of SUSY can be obtained via the analysis of precision electroweak measurements.
In this review, we discuss the prospective implications for SUSY of present and
future precision studies at low energy.Comment: 118 pages, review pape
Parity-Violating Electron Scattering as a Probe of Supersymmetry
We compute the one-loop supersymmetric (SUSY) contributions to the weak
charges of the electron () and proton () using the Minimal
Supersymmetric Standard Model (MSSM). These vector couplings of the
-boson to fermions will be determined in two fixed-target,
parity-violating electron scattering experiments. The SUSY loop contributions
to and can be substantial, leading to several percent
corrections to the Standard Model values for these quantities. We show that the
relative signs of the SUSY loop effects on and are correlated
and positive over nearly all of the MSSM parameter space, whereas inclusion of
R-parity nonconserving interactions can lead to opposite sign relative shifts
in the weak charges. Thus, a comparison of and measurements
could help distinguish between different SUSY scenarios.Comment: 4 pages, 2 figure
Probing Supersymmetry with Neutral Current Scattering Experiments
We compute the supersymmetric contributions to the weak charges of the
electron and proton in the framework of Minimal Supersymmetric Standard Model.
We also consider the ratio of neutral current to charged current cross
sections, R_nu and R_nubar at nu (nubar)-nucleus deep inelastic scattering, and
compare the supersymmetric corrections with the deviations of these quantities
from the Standard Model predictions implied by the recent NuTeV measurement.Comment: 4 pages, contribution to the proceedings of CIPANP 2003 (May, 2003),
New York Cit
Pre-flare coronal dimmings
In this paper, we focus on the pre-flare coronal dimmings. We report our
multiwavelength observations of the GOES X1.6 solar flare and the accompanying
halo CME produced by the eruption of a sigmoidal magnetic flux rope (MFR) in
NOAA active region (AR) 12158 on 2014 September 10. The eruption was observed
by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamic Observatory
(SDO). The photospheric line-of-sight magnetograms were observed by the
Helioseismic and Magnetic Imager (HMI) aboard SDO. The soft X-ray (SXR) fluxes
were recorded by the GOES spacecraft. The halo CME was observed by the white
light coronagraphs of the Large Angle Spectroscopic Coronagraph (LASCO) aboard
SOHO.} {About 96 minutes before the onset of flare/CME, narrow pre-flare
coronal dimmings appeared at the two ends of the twisted MFR. They extended
very slowly with their intensities decreasing with time, while their apparent
widths (89 Mm) nearly kept constant. During the impulsive and decay phases
of flare, typical fanlike twin dimmings appeared and expanded with much larger
extent and lower intensities than the pre-flare dimmings. The percentage of 171
{\AA} intensity decrease reaches 40\%. The pre-flare dimmings are most striking
in 171, 193, and 211 {\AA} with formation temperatures of 0.62.5 MK. The
northern part of the pre-flare dimmings could also be recognized in 131 and 335
{\AA}.} To our knowledge, this is the first detailed study of pre-flare coronal
dimmings, which can be explained by the density depletion as a result of the
gradual expansion of the coronal loop system surrounding the MFR during the
slow rise of the MFR.Comment: 6 pages, 8 figures, to be accepted for publication by A&
Dirac-Schr\"odinger equation for quark-antiquark bound states and derivation of its interaction kerne
The four-dimensional Dirac-Schr\"odinger equation satisfied by
quark-antiquark bound states is derived from Quantum Chromodynamics. Different
from the Bethe-Salpeter equation, the equation derived is a kind of first-order
differential equations of Schr\"odinger-type in the position space. Especially,
the interaction kernel in the equation is given by two different closed
expressions. One expression which contains only a few types of Green's
functions is derived with the aid of the equations of motion satisfied by some
kinds of Green's functions. Another expression which is represented in terms of
the quark, antiquark and gluon propagators and some kinds of proper vertices is
derived by means of the technique of irreducible decomposition of Green's
functions. The kernel derived not only can easily be calculated by the
perturbation method, but also provides a suitable basis for nonperturbative
investigations. Furthermore, it is shown that the four-dimensinal
Dirac-Schr\"odinger equation and its kernel can directly be reduced to rigorous
three-dimensional forms in the equal-time Lorentz frame and the
Dirac-Schr\"odinger equation can be reduced to an equivalent
Pauli-Schr\"odinger equation which is represented in the Pauli spinor space. To
show the applicability of the closed expressions derived and to demonstrate the
equivalence between the two different expressions of the kernel, the t-channel
and s-channel one gluon exchange kernels are chosen as an example to show how
they are derived from the closed expressions. In addition, the connection of
the Dirac-Schr\"odinger equation with the Bethe-Salpeter equation is discussed
Detection of a new methanol maser line with ALMA
Aims. We aimed at investigating the structure and kinematics of the gaseous
disk and outflows around the massive YSO S255 NIRS3 in the S255IR-SMA1 dense
clump. Methods. Observations of the S255IR region were carried out with ALMA at
two epochs in the compact and extended configurations. Results. We
serendipitously detected a new, never predicted, bright maser line at about
349.1 GHz, which most probably represents the CHOH A transition. The emission covers most of the 6.7 GHz methanol maser emission
area of almost 1 in size and shows a velocity gradient in the
same sense as the disk rotation. No variability was found on the time interval
of several months. It is classified as Class II maser and probably originates
in a ring at a distance of several hundreds AU from the central star.Comment: 4 pages, 4 figures, accepted by Astronomy and Astrophysic
Voltage-controlled wavelength conversion by terahertz electro-optic modulation in double quantum wells
An undoped double quantum well (DQW) was driven with a terahertz (THz)
electric field of frequency \omega_{THz} polarized in the growth direction,
while simultaneously illuminated with a near-infrared (NIR) laser at frequency
\omega_{NIR}. The intensity of NIR upconverted sidebands
\omega_{sideband}=\omega_{NIR} + \omega_{THz} was maximized when a dc voltage
applied in the growth direction tuned the excitonic states into resonance with
both the THz and NIR fields. There was no detectable upconversion far from
resonance. The results demonstrate the possibility of using gated DQW devices
for all-optical wavelength shifting between optical communication channels
separated by up to a few THz.Comment: 3 pages, 6 figures. Figures 5 and 6 are JPEG files, figures/fig5.jpg
and fig6.jp
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