6,108 research outputs found
Where are the missing members of the baryon antidecuplet?
We analyze what consequences has the observation of exotic pentaquark baryons
on the location of the non-exotic baryons belonging to the antidecuplet. We
suggest that there must be a new nucleon state at 1650-1690 MeV and a new Sigma
baryon at 1760-1810 MeV.Comment: 5 pages, 1 figure. Missing reference adde
The energies and residues of the nucleon resonances N(1535) and N(1650)
We extract pole positions for the N(1535) and N(1650) resonances using two
different models. The positions are determined from fits to different subsets
of the existing , and data
and found to be 1515(10)--i85(15)MeV and 1660(10)--i65(10)MeV, when the data is
described in terms of two poles. Sensitivity to the choice of fitted data is
explored. The corresponding and residues of these poles
are also extracted.Comment: 9 page
Multipole Amplitudes of Pion Photoproduction on Nucleons up to 2GeV within Dispersion Relations and Unitary Isobar Model
Two approaches for analysis of pion photo- and electroproduction on nucleons
in the resonance energy region are checked at using the results of
GWU(VPI) partial-wave analysis of photoproduction data. The approaches are
based on dispersion relations and unitary isobar model. Within dispersion
relations good description of photoproduction multipoles is obtained up to
. Within unitary isobar model, modified with increasing energy by
incorporation of Regge poles, and with unified Breit-Wigner parametrization of
resonance contributions, good description of photoproduction multipoles is
obtained up to .Comment: 23 pages, LaTe
Satellite power system: Concept development and evaluation program. Volume 3: Power transmission and reception. Technical summary and assessment
Efforts in the DOE/NASA concept development and evaluation program are discussed for the solar power satellite power transmission and reception system. A technical summary is provided together with a summary of system assessment activities. System options and system definition drivers are described. Major system assessment activities were in support of the reference system definition, solid state system studies, critical technology supporting investigations, and various system and subsystem tradeoffs. These activities are described together with reference system updates and alternative concepts for each of the subsystem areas. Conclusions reached as a result of the numerous analytical and experimental evaluations are presented. Remaining issues for a possible follow-on program are identified
Model dependence of single-energy fits to pion photoproduction data
Model dependence of multipole analysis has been explored through
energy-dependent and single-energy fits to pion photoproduction data. The MAID
energy-dependent solution has been used as input for an event generator
producing realistic pseudo data. These were fitted using the SAID
parametrization approach to determine single-energy and energy-dependent
solutions over a range of lab photon energies from 200 to 1200 MeV. The
resulting solutions were found to be consistent with the input amplitudes from
MAID. Fits with a -squared per datum of unity or less were generally
achieved. We discuss energy regions where consistent results are expected, and
explore the sensitivity of fits to the number of included single- and
double-polarization observables. The influence of Watson's theorem is examined
in detail.Comment: 12 pages, 8 figure
Vegetation Dynamics at the Upper Reaches of a Tropical Montane Forest are Driven by Disturbance Over the Past 7300 Years
We assessed tropical montane cloud forest (TMCF) sensitivity to natural disturbance by drought, fire, and dieback with a 7300-year-long paleorecord. We analyzed pollen assemblages, charcoal accumulation rates, and higher plant biomarker compounds (average chain length [ACL] of n-alkanes) in sediments from Wai'ānapanapa, a small lake near the upper forest limit and the mean trade wind inversion (TWI) in Hawai‘i. The paleorecord of ACL suggests increased drought frequency and a lower TWI elevation from 2555–1323 cal yr B.P. and 606–334 cal yr B.P. Charcoal began to accumulate and a novel fire regime was initiated ca. 880 cal yr B.P., followed by a decreased fire return interval at ca. 550 cal yr B.P. Diebacks occurred at 2931, 2161, 1162, and 306 cal yr B.P., and two of these were independent of drought or fire. Pollen assemblages indicate that on average species composition changed only 2.8% per decade. These dynamics, though slight, were significantly associated with disturbance. The direction of species composition change varied with disturbance type. Drought was associated with significantly more vines and lianas; fire was associated with an increase in the tree fern Sadleria and indicators of open, disturbed landscapes at the expense of epiphytic ferns; whereas stand-scale dieback was associated with an increase in the tree fern Cibotium. Though this cloud forest was dynamic in response to past disturbance, it has recovered, suggesting a resilient TMCF with no evidence of state change in vegetation type (e.g., grassland or shrubland)
Universality of Long-Range Correlations in Expansion-Randomization Systems
We study the stochastic dynamics of sequences evolving by single site
mutations, segmental duplications, deletions, and random insertions. These
processes are relevant for the evolution of genomic DNA. They define a
universality class of non-equilibrium 1D expansion-randomization systems with
generic stationary long-range correlations in a regime of growing sequence
length. We obtain explicitly the two-point correlation function of the sequence
composition and the distribution function of the composition bias in sequences
of finite length. The characteristic exponent of these quantities is
determined by the ratio of two effective rates, which are explicitly calculated
for several specific sequence evolution dynamics of the universality class.
Depending on the value of , we find two different scaling regimes, which
are distinguished by the detectability of the initial composition bias. All
analytic results are accurately verified by numerical simulations. We also
discuss the non-stationary build-up and decay of correlations, as well as more
complex evolutionary scenarios, where the rates of the processes vary in time.
Our findings provide a possible example for the emergence of universality in
molecular biology.Comment: 23 pages, 15 figure
Electroexcitation of the Roper resonance from CLAS data
The helicity amplitudes of the electroexcitation of the Roper resonance on
proton are extracted at 1.7 < Q2 < 4.2 GeV2 from recent high precision
JLab-CLAS cross sections data and longitudinally polarized beam asymmetry for
pi+ electroproduction on protons. The analysis is made using two approaches,
dispersion relations and unitary isobar model, which give consistent results.
It is found that the transverse helicity amplitude for the gamma* p -->
P11(1440) transition, which is large and negative at Q2=0, becomes large and
positive at Q2 ~ 2 GeV2, and then drops slowly with Q2. Longitudinal helicity
amplitude, that was previously found from CLAS data as large and positive at
Q2=0.4,0.65 GeV2, drops with Q2. These results rule out the presentation of
P11(1440) as a 3qG hybrid state, and provide strong evidence in favor of this
resonance as a first radial excitation of the 3q ground state.Comment: 3 pages, 2 figures, Talk on the Workshop on "The Physics of Excited
Nucleons", Bonn, Germany, October 200
Tornadic Behavior Related to Land-Falling Tropical Cyclones in the United States
The 2004 and 2005 North Atlantic hurricane seasons were among the most active and economically devastating for the United States, during which 18 tropical cyclones (TCs) made landfall. These TCs were analyzed using the International Best Tracks Archive for Climate Stewardship (IBTrACS) and Local Storm Reports (LSR) datasets to determine whether they produced tornadoes within a preferred quadrant and distance from the center of circulation of the TC. The land-falling TCs were tracked and analyzed through their weakening stages with tornado reports being classified based on the strength of the TC at the time of occurrence. Tornado reports were not included after the TC was classified as extratropical in the IBTrACS dataset. Over half of all tornado reports occurred when the TCs were rated at or below tropical storm strength. As expected, the northeast quadrant was the most dominate area where tornadic activity occurred. In addition, there were three distinct peaks in tornadic activity at distances of 75-100nm, 175-200nm, and 325-375nm from the center of the circulation. Another emphasis of this work used NEXRAD data to determine the best method of identifying potential tornadic storms within land-falling TCS. The most reliable radar product for the three TCs investigated was velocity couplets
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