37,483 research outputs found
Parity-Violating Nuclear Force as derived from QCD Sum Rules
Parity-violating nuclear force, as may be accessed from parity violation
studies in nuclear systems, represents an area of nonleptonic weak interactions
which has been the subject of experimental investigations for several decades.
In the simple meson-exchange picture, parity-violating nuclear force may be
parameterized as arising from exchange of \pi, \rho, \omega, or other meson(s)
with strong meson-nucleon coupling at one vertex and weak parity-violating
meson-nucleon coupling at the other vertex. The QCD sum rule method allows for
a fairly complicated, but nevertheless straightforward, leading-order
loop-contribution determination of the various parity-violating MNN couplings
starting from QCD (with the nontrivial vacuum) and Glashow-Salam-Weinberg
electroweak theory. We continue our earlier investigation of parity-violating
\pi NN coupling (by Henley, Hwang, and Kisslinger) to other parity-violating
couplings. Our predictions are in reasonable overall agreement with the results
estimated on phenomenological grounds, such as in the now classic paper of
Desplanques, Donoghue, and Holstein (DDH), in the global experimental fit of
Adelberger and Haxton (AH), or the effective field theory (EFT) thinking of
Ramsey-Musolf and Page (RP).Comment: 17 pages, 5 figure
Heating of Flare Loops With Observationally Constrained Heating Functions
We analyze high cadence high resolution observations of a C3.2 flare obtained
by AIA/SDO on August 1, 2010. The flare is a long duration event with soft
X-ray and EUV radiation lasting for over four hours. Analysis suggests that
magnetic reconnection and formation of new loops continue for more than two
hours. Furthermore, the UV 1600\AA\ observations show that each of the
individual pixels at the feet of flare loops is brightened instantaneously with
a timescale of a few minutes, and decays over a much longer timescale of more
than 30 minutes. We use these spatially resolved UV light curves during the
rise phase to construct empirical heating functions for individual flare loops,
and model heating of coronal plasmas in these loops. The total coronal
radiation of these flare loops are compared with soft X-ray and EUV radiation
fluxes measured by GOES and AIA. This study presents a method to
observationally infer heating functions in numerous flare loops that are formed
and heated sequentially by reconnection throughout the flare, and provides a
very useful constraint to coronal heating models.Comment: This paper is revise
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