11,051 research outputs found
Raman gain against a background of non-thermal ion fluctuations in a plasma
A complex stimulated Raman scattering event against a background of non-thermal ion acoustic waves in an inhomogeneous plasma is described. We obtain analytic forms for the Raman gain due to a five-wave interaction consisting of conventional three-wave Raman scattering followed by the decay of the Raman Langmuir wave into a second Langmuir wave (or a second scattered light wave) and an ion acoustic wave. Very modest levels of ion waves produce a. significant effect on Raman convective gain. A combination of plasma inhomogeneity and suprathermal ion fluctuations may offer a means for the control of Raman gain
Soil moisture detection by Skylab's microwave sensors
The author has identified the following significant results. Terrain microwave backscatter and emission response to soil moisture variations were investigated using Skylab's 13.9 GHz RADSCAT (radiometer/scatterometer) system. Data acquired on June 5, 1973, over a test site in west-central Texas indicated a fair degree of correlation with composite rainfall. The scan made was cross-track contiguous (CTC) with a pitch of 29.4 deg and no roll effect. Vertical polarization was employed with both radiometer and scatterometer. The composite rainfall was computed according to the flood prediction technique using rainfall data supplied by weather reporting stations
The Chandra Large Area Synoptic X-ray Survey (CLASXS) of the Lockman Hole-Northwest: The X-ray Catalog
We present the X-ray catalog and basic results from our Chandra Large Area
Synoptic X-ray Survey (CLASXS) of the Lockman Hole-Northwest field. Our 9
ACIS-I fields cover a contiguous solid angle of ~0.4 sq. deg. and reach fluxes
of 5E-16 cgs (0.4-2 keV) and 3E-15 cgs (2-8keV). Our survey bridges the gap
between ultradeep pencil-beam surveys, such as the Chandra Deep Fields (CDFs),
and shallower, large area surveys, allowing a better probe of the X-ray sources
that contribute most of the 2-10 keV cosmic X-ray background (CXB). We find a
total of 525 X-ray point sources and 4 extended sources. At ~10E-14 cgs 2-8
keV, our number counts are significantly higher than those of several
non-contiguous, large area surveys. On the other hand, the integrated flux from
the CLASXS field, combined with ASCA and Chandra ultradeep surveys, is
consistent with results from other large area surveys, within the variance of
the CXB. Spectral evolution is seen in the hardening of the sources at fluxes
below 1E-14 cgs Above 4E1-14 cgs(0.4-8 keV), ~60 of the sources are variable.
Four extended sources in CLASXS is consistent with the previously measured
LogN-LogS of galaxy clusters. We report the discovery of a gravitational
lensing arc associated with one of these sources. (Abridged)Comment: 67 pages, 26 figures, accepted for publication in the Astronomical
Journa
A year in review:Real world evidence, functional monitoring and emerging therapeutics in 2021
Discovery and Measurement of Sleptons, Binos, and Winos with a Z'
Extensions of the MSSM could significantly alter its phenomenology at the
LHC. We study the case in which the MSSM is extended by an additional U(1)
gauge symmetry, which is spontaneously broken at a few TeV. The production
cross-section of sleptons is enhanced over that of the MSSM by the process
, so the discovery potential for
sleptons is greatly increased. The flavor and charge information in the
resulting decay, , provides a useful handle on
the identity of the LSP. With the help of the additional kinematical constraint
of an on-shell Z', we implement a novel method to measure all of the
superpartner masses involved in this channel. For certain final states with two
invisible particles, one can construct kinematic observables bounded above by
parent particle masses. We demonstrate how output from one such observable,
m_T2, can become input to a second, increasing the number of measurements one
can make with a single decay chain. The method presented here represents a new
class of observables which could have a much wider range of applicability.Comment: 20 pages, 15 figures; v2 references added and minor change
General analysis of signals with two leptons and missing energy at the Large Hadron Collider
A signal of two leptons and missing energy is challenging to analyze at the
Large Hadron Collider (LHC) since it offers only few kinematical handles. This
signature generally arises from pair production of heavy charged particles
which each decay into a lepton and a weakly interacting stable particle. Here
this class of processes is analyzed with minimal model assumptions by
considering all possible combinations of spin 0, 1/2 or 1, and of weak
iso-singlets, -doublets or -triplets for the new particles. Adding to existing
work on mass and spin measurements, two new variables for spin determination
and an asymmetry for the determination of the couplings of the new particles
are introduced. It is shown that these observables allow one to independently
determine the spin and the couplings of the new particles, except for a few
cases that turn out to be indistinguishable at the LHC. These findings are
corroborated by results of an alternative analysis strategy based on an
automated likelihood test.Comment: 18 pages, 3 figures, LaTe
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