198 research outputs found
The E358 High Resolution Neutron Detector
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Study of Dipole Resonance Strength in 12-C via the Reactions 12-C(pol.p,p'c)
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Isospin Response of the 4-He Continuum
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Measurements of ep → e′π+π-p′ Cross Sections with CLAS at 1.40 GeV \u3c W \u3c 2.0 GeV and 2.0 GeV² \u3c Q² \u3c 5.0 GeV²
This paper reports new exclusive cross sections for ep → e′π+π-p′ using the CLAS detector at Jefferson Laboratory. These results are presented for the first time at photon virtualities 2.0GeV2 2 \u3c 5.0GeV2 in the center-of-mass energy range 1.4 GeV \u3c W \u3c 2.0 GeV, which covers a large part of the nucleon resonance region. Using a model developed for the phenomenological analysis of electroproduction data, we see strong indications that the relative contributions from the resonant cross sections at W \u3c 1.74 GeV increase with Q2. These data considerably extend the kinematic reach of previous measurements. Exclusive ep → e′π+π-p′ cross section measurements are of particular importance for the extraction of resonance electrocouplings in the mass range above 1.6 GeV
Today's View on Strangeness
There are several different experimental indications, such as the
pion-nucleon sigma term and polarized deep-inelastic scattering, which suggest
that the nucleon wave function contains a hidden s bar s component. This is
expected in chiral soliton models, which also predicted the existence of new
exotic baryons that may recently have been observed. Another hint of hidden
strangeness in the nucleon is provided by copious phi production in various N
bar N annihilation channels, which may be due to evasions of the
Okubo-Zweig-Iizuka rule. One way to probe the possible polarization of hidden s
bar s pairs in the nucleon may be via Lambda polarization in deep-inelastic
scattering.Comment: 8 pages LaTeX, 10 figures, to appear in the Proceedings of the
International Conference on Parity Violation and Hadronic Structure,
Grenoble, June 200
The response of nematodes to deep-sea CO2 sequestration : a quantile regression approach
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 57 (2010): 696-707, doi:10.1016/j.dsr.2010.03.003.One proposed approach to ameliorate the effects of global warming is sequestration of
the greenhouse gas CO2 in the deep sea. To evaluate the environmental impact of this
approach, we exposed the sediment-dwelling fauna at the mouth of the Monterey
Submarine Canyon (3262 m) and a site on the nearby continental rise (3607 m) to CO2-
rich water. We measured meiobenthic nematode population and community metrics
after ~30-day exposures along a distance gradient from the CO2 source and with
sediment depth to infer the patterns of mortality. We also compared the nematode
response with that of harpacticoid copepods. Nematode abundance, average sediment
depth, tail-group composition, and length: width ratio did not vary with distance from
the CO2 source. However, quantile regression showed that nematode length and
diameter increased in close proximity to the CO2 source in both experiments. Further,
the effects of CO2 exposure and sediment depth (nematodes became more slender at
one site, but larger at the other, with increasing depth in the sediment) varied with body
size. For example, the response of the longest nematodes differed from those of
average length. We propose that nematode body length and diameter increases were
induced by lethal exposure to CO2-rich water and that nematodes experienced a high
rate of mortality in both experiments. In contrast, copepods experienced high mortality
rates in only one experiment suggesting that CO2 sequestration effects are taxon
specific.The Department of Energy
Office of Biological and Environmental Research supported this research under award
numbers DE‐FG02‐05ER64070 and DE‐FG03‐01ER63065 and the U.S. Department of
Energy, Fossil Energy Group (award DE‐FC26‐00NT40929). We also appreciate
significant support provided by the Monterey Bay Aquarium Research Institute (project
200002)
A purely algebraic construction of a gauge and renormalization group invariant scalar glueball operator
This paper presents a complete algebraic proof of the renormalizability of
the gauge invariant operator to all orders of
perturbation theory in pure Yang-Mills gauge theory, whereby working in the
Landau gauge. This renormalization is far from being trivial as mixing occurs
with other gauge variant operators, which we identify explicitly. We
determine the mixing matrix to all orders in perturbation theory by using
only algebraic arguments and consequently we can uncover a renormalization
group invariant by using the anomalous dimension matrix derived from
. We also present a future plan for calculating the mass of the lightest
scalar glueball with the help of the framework we have set up.Comment: 17 page
Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2
Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0
electroproduction reactions have been performed at the Mainz Microtron MAMI in
the A1 spectrometer facility using for the first time the Kaos spectrometer for
kaon detection. These processes were studied in a kinematical region not
covered by any previous experiment. The nucleon was probed in its third
resonance region with virtual photons of low four-momenta, Q^2= 0.030-0.055
(GeV/c)^2. The MAMI data indicate a smooth transition in Q^2 from
photoproduction to electroproduction cross sections. Comparison with
predictions of effective Lagrangian models based on the isobar approach reveal
that strong longitudinal couplings of the virtual photon to the N* resonances
can be excluded from these models.Comment: 16 pages, 7 figure
The CLAS12 software framework and event reconstruction
We describe offline event reconstruction for the CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12), including an overview of the offline reconstruction framework and software tools, a description of the algorithms developed for the individual detector subsystems, and the overall approach for charged and neutral particle identification. We also present the scheme for data processing and the code management procedures
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