3,207 research outputs found
Kaon photoproduction on the nucleon with constrained parameters
The new experimental data of kaon photoproduction on the nucleon, gamma p ->
K+ Lambda, have been analyzed by means of a multipoles model. Different from
the previous models, in this analysis the resonance decay widths are
constrained to the values given by the Particle Data Group (PDG). The result
indicates that constraining these parameters to the PDG values could
dramatically change the conclusion of the important resonances in this reaction
found in the previous studies.Comment: 4 pages, 3 figures, talk given by Ryky Nelson at Fourth Asia-Pacific
Conference on Few-Body Problems in Physics 2008 (APFB08), Depok, Indonesia,
August 19-23, 200
Gerasimov-Drell-Hearn Sum Rule and the Discrepancy between the New CLAS and SAPHIR Data
Contribution of the K^+\Lambda channel to the Gerasimov-Drell-Hearn (GDH) sum
rule has been calculated by using the models that fit the recent SAPHIR or CLAS
differential cross section data. It is shown that the two data sets yield quite
different contributions. Contribution of this channel to the forward spin
polarizability of the proton has been also calculated. It is also shown that
the inclusion of the recent CLAS C_x and C_z data in the fitting data base does
not significantly change the result of the present calculation. Results of the
fit, however, reveal the role of the S_{11}(1650), P_{11}(1710), P_{13}(1720),
and P_{13}(1900) resonances for the description of the C_x and C_z data. A
brief discussion on the importance of these resonances is given. Measurements
of the polarized total cross section \sigma_{TT'} by the CLAS, LEPS, and MAMI
collaborations are expected to verify this finding.Comment: 15 pages, 8 figure
Role of the meson in photoproduction off the deuteron
Neutral kaon photoproduction off the nucleon and deuteron has been
reinvestigated by utilizing the new experimental data on both targets. An
isobar model for elementary operator and impulse approximation for the reaction
on the deuteron have been used. The available free parameters in the elementary
model have been extracted from both elementary and deuteron data. In contrast
to the elementary reaction, fitting the deuteron data requires an inclusion of
weighting factor. The result indicates that the angular distribution of the
elementary process does not show backward peaking behavior.Comment: 4 pages, 4 figures, prepared for the Fifth Asia-Pacific Conference on
Few-Body Problems in Physics 2011 (APFB2011), Seoul, Korea, August 22-26,
201
Long-Term Load Forecasting Considering Volatility Using Multiplicative Error Model
Long-term load forecasting plays a vital role for utilities and planners in
terms of grid development and expansion planning. An overestimate of long-term
electricity load will result in substantial wasted investment in the
construction of excess power facilities, while an underestimate of future load
will result in insufficient generation and unmet demand. This paper presents
first-of-its-kind approach to use multiplicative error model (MEM) in
forecasting load for long-term horizon. MEM originates from the structure of
autoregressive conditional heteroscedasticity (ARCH) model where conditional
variance is dynamically parameterized and it multiplicatively interacts with an
innovation term of time-series. Historical load data, accessed from a U.S.
regional transmission operator, and recession data for years 1993-2016 is used
in this study. The superiority of considering volatility is proven by
out-of-sample forecast results as well as directional accuracy during the great
economic recession of 2008. To incorporate future volatility, backtesting of
MEM model is performed. Two performance indicators used to assess the proposed
model are mean absolute percentage error (for both in-sample model fit and
out-of-sample forecasts) and directional accuracy.Comment: 19 pages, 11 figures, 3 table
Extinction by Miscalculation:
Species at Risk Act, Sakinaw sockeye, Cultus sockeye, fisheries management, extinction.
Gauge-invariant tree-level photoproduction amplitudes with form factors
We show how the gauge-invariance formulation given by Haberzettl is
implemented in practice for photoproduction amplitudes at the tree level with
form factors describing composite nucleons. We demonstrate that, in contrast to
Ohta's gauge-invariance prescription, this formalism allows electric current
contributions to be multiplied by a form factor, i.e., it does not require that
they be treated like bare currents. While different in detail, this
nevertheless lends support to previous ad hoc approaches which multiply the
Born amplitudes by an overall form factor. Numerical results for kaon
photoproduction off the nucleon are given. They show that the gauge procedure
by Haberzettl leads to much improved values as compared to Ohta's
prescription.Comment: 5 pages, RevTeX, two eps figure
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