7,917 research outputs found
Colored Spin Systems, BKP Evolution and finite N_c effects
Even within the framework of the leading logarithmic approximation the
eigenvalues of the BKP kernel for states of more than three reggeized gluons
are unknown in general, contrary to the planar limit case where the problem
becomes integrable. We consider a 4-gluon kernel for a finite number of colors
and define some simple toy models for the configuration space dynamics, which
are directly solvable with group theoretical methods. Then we study the
dependence of the spectrum of these models with respect to the number of colors
and make comparisons with the large limit case.Comment: 17 pages, 4 figures, references update, to appear on EPJ
Silicon solar cell development for low temperature and low illumination intensity operation, volume 1 Analysis report, 30 Jun. 1969 - 30 Apr. 1970
Operational performance of solar cell at low temperatures and under low illumination intensit
Helicity Parton Distributions at a Future Electron-Ion Collider: A Quantitative Appraisal
We present a quantitative assessment of the impact a future electron-ion
collider will have on determinations of helicity quark and gluon densities and
their contributions to the proton spin. Our results are obtained by performing
a series of global QCD analyses at next-to-leading order accuracy based on
realistic sets of pseudo-data for the inclusive and semi-inclusive
deep-inelastic scattering of longitudinally polarized electrons and protons at
different, conceivable center-of-mass system energies.Comment: 11 pages, 8 figure
First Report of the Alfalfa Blotch Leafminer (Diptera: Agromyzidae), and Selected Parasites (Hymenoptera: Eulophidae) in Minnesota and Wisconsin, USA
Alfalfa blotch leafminer, Agromyza frontella, has been a serious pest of alfalfa, Medicago sativa, in the northeastern U.S. and in eastern Ontario, Canada. Until recently, the western edge of the A. frontella distribution in the U.S. was limited to eastern Ohio. We document for the first time, the occurrence of A. frontella in Minnesota and Wisconsin. Alfalfa stems damaged by A. frontella, based on adult feeding punctures, obvious blotched leafmining or the presence of larvae, were first found in 3 northern Minnesota counties during October, 1994. Infested counties included Lake of the Woods, Cook and Lake, all bordering western Ontario, Canada. In 1995, A. frontella was again found in Cook and Lake counties, where 99-100% of the stems, and 18-35% of the trifoliates/stem, contained larvae or exhibited obvious feeding damage. In 1996, following a more expanded survey, a total of 11 and 5 counties, in Minnesota and Wisconsin, respectively, showed some level of A. frontella feeding damage (stem samples ranged from \u3c5 to 100% infested). Based on additional counties surveyed 11 October, 1996, where A. frontella was not found, we now have a reasonable estimate of the southern edge of the distribution in Minnesota and Wisconsin. A total of 2 and 6 A. frontella adults were identified from sweep-net samples taken from fields with obvious feeding damage during 1995 (Lake Co.) and 1996 (Cook Co,), respectively. Three eulophid (Hymenoptera) parasites were reared from A. frontella-infested alfalfa stems collected during October, 1994 in Cook Co., Minn., including: Diglyphus begini, D. pulchripes, and Diglyphus sp., prob. isaea, all of which are new records. Our hypothesis is that A. frontella moved into Minnesota from Ontario Canada, via alfalfa hay purchased by northern Minnesota growers
Geometric Scaling in Inclusive Charm Production
We show that the cross section for inclusive charm production exhibits
geometric scaling in a large range of photon virtualities. In the HERA
kinematic domain the saturation momentum stays below the hard
scale , implying charm production probing mostly the color
transparency regime and unitarization effects being almost negligible. We
derive our results considering two saturation models which are able to describe
the DESY ep collider HERA data for the proton structure function at small
values of the Bjorken variable . A striking feature is the scaling on
above saturation limit, corroborating recent
theoretical studies.Comment: 4 pages, 2 figures. Version to be published in Physical Review
Letter
Spatial distribution of ions in a linear octopole radio-frequency ion trap in the space-charge limit
We have explored the spatial distribution of an ion cloud trapped in a linear
octopole radio-frequency (rf) ion trap. The two-dimensional distribution of the
column density of stored silver dimer cations was measured via
photofragment-ion yields as a function of the position of the incident laser
beam over the transverse cross section of the trap. The profile of the ion
distribution was found to be dependent on the number of loaded ions. Under high
ion-loading conditions with a significant space-charge effect, ions form a ring
profile with a maximum at the outer region of the trap, whereas they are
localized near the center axis region at low loading of the ions. These results
are explained quantitatively by a model calculation based on equilibrium
between the space-charge-induced potential and the effective potential of the
multipole rf field. The maximum adiabaticity parameter \eta_max is estimated to
be about 0.13 for the high ion-density condition in the present octopole ion
trap, which is lower than typical values reported for low ion densities; this
is probably due to additional instability caused by the space charge.Comment: 8 pages, 5 figure
Exclusive diffractive processes at HERA within the dipole picture
We present a simultaneous analysis, within an impact parameter dependent
saturated dipole model, of exclusive diffractive vector meson (J/psi, phi and
rho) production, deeply virtual Compton scattering and the total gamma* p cross
section data measured at HERA. Various cross sections measured as a function of
the kinematic variables Q^2, W and t are well described, with little
sensitivity to the details of the vector meson wave functions. We determine the
properties of the gluon density in the proton in both longitudinal and
transverse dimensions, including the impact parameter dependent saturation
scale. The overall success of the description indicates universality of the
emerging gluon distribution and proton shape.Comment: 48 pages, 28 figures, the final version to appear in Physical Review
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