1,042 research outputs found
The He(e, ed)p Reaction in q-constant Kinematics
The cross section for the He(e, ed)p reaction has been measured as a
function of the missing momentum in q -constant kinematics at
beam energies of 370 and 576 MeV for values of the three-momentum transfer
of 412, 504 and 604 \mevc. The L(+TT), T and LT structure functions have been
separated for = 412 and 504 \mevc. The data are compared to three-body
Faddeev calculations, including meson-exchange currents (MEC), and to
calculations based on a covariant diagrammatic expansion. The influence of
final-state interactions and meson-exchange currents is discussed. The
-dependence of the data is reasonably well described by all calculations.
However, the most advanced Faddeev calculations, which employ the AV18
nucleon-nucleon interaction and include MEC, overestimate the measured cross
sections, especially the longitudinal part, and at the larger values of .
The diagrammatic approach gives a fair description of the cross section, but
under(over)estimates the longitudinal (transverse) structure function.Comment: 17 pages, 7 figure
A high-precision polarimeter
We have built a polarimeter in order to measure the electron beam
polarization in hall C at JLAB. Using a superconducting solenoid to drive the
pure-iron target foil into saturation, and a symmetrical setup to detect the
Moller electrons in coincidence, we achieve an accuracy of <1%. This sets a new
standard for Moller polarimeters.Comment: 17 pages, 9 figures, submitted to N.I.
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 6: Accelerator Capabilities
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 6, on Accelerator Capabilities, discusses
the future progress of accelerator technology, including issues for high-energy
hadron and lepton colliders, high-intensity beams, electron-ion colliders, and
necessary R&D for future accelerator technologies.Comment: 26 page
Perturbative QCD Analysis of Local Duality in a fixed W^2 Framework
We study the global Q^2 dependence of large x, F_2 nucleon structure function
data, with the aim of providing a perturbative-QCD based, quantitative analysis
of parton-hadron duality. As opposed to previous analyses at fixed x, we use a
framework in fixed W^2. We uncover a breakdown of the twist-4 approximation
with a renormalon type improvement at O(1/Q^4) which, by affecting the initial
evolution of parton distributions, will have consequences for pQCD analyses
also at large x and very large Q^2.Comment: RevTex4, 8 pages, 3 figure
Measurement of the EMC Effect in the Deuteron
We determined the structure function ratio RdEMC=Fd2/(Fn2+Fp2) from recently published Fn2/Fd2 data taken by the BONuS experiment using CLAS at Jefferson Lab. This ratio deviates from unity, with a slope dRdEMC/dx=−0.10 ± 0.05 in the range of Bjorken x from 0.35 to 0.7, for invariant mass W\u3e1.4 GeV and Q2\u3e1 GeV2 . The observed EMC effect for these kinematics is consistent with conventional nuclear physics models that include off-shell corrections, as well as with empirical analyses that find the EMC effect proportional to the probability of short-range nucleon-nucleon correlations
Future Climate and Land Use Change Impacts on River Flows in the Tapajós Basin in the Brazilian Amazon
Abstract Land conversion and changing climate are expected to significantly alter tropical forest hydrology. We used a land surface model integrated with a river routing scheme to analyze the hydrological alterations expected in the Tapajós River basin, a large portion of the Brazilian Amazon, caused by two environmental drivers: climate and land use. The model was forced with two future climate scenarios (years 2026–2045) from the Earth System Model HadGem2‐ES with moderate (+4.5 W/m2 radiative forcing value in the year 2100 with respect to preindustrial levels) and severe (+8.5 W/m2) representative atmospheric carbon dioxide pathways (Representative Concentration Pathways). We tested the sensitivity of our results to the uncertainty in future climate projections by running simulations with IPSL‐CM5 (wettest scenarios) and GISS‐E2 (driest scenarios). Human land use effects on vegetation were evaluated using a limited and an extreme deforestation scenario. Our analysis indicates that climate change is predicted to reduce river flows across seasons (up to 20%) and bring a considerable shift in flow seasonality toward a later onset (nearly 1.5 months) and increase in interannual variability. While land use change partially counteracts the climate‐driven diminishing trend in river flows, it is expected to contribute to a further increase in interannual and intraannual variability. From a water management perspective, the overall reduction of river flows and their increased variability, combined with the shift and the shortening of the wet season, could potentially affect the productivity of the large hydropower systems planned for the region and the growing demand for agricultural and transport expansion
Moments of the Proton F2 Structure Function at Low Q2
The Q^2 dependence of inclusive electron-proton scattering F_2 structure
function data in both the nucleon resonance region and the deep inelastic
region, at momentum transfers below 5 (GeV/c)^2, is investigated. Moments of
F_2 are constructed, down to momentum transfers of Q^2 ~ 0.1 (GeV/c)^2. The
second moment is only slowly varying with Q^2 down to Q^2 ~ 1 (GeV/c)^2, which
is a reflection of duality. Below Q^2 of 1 (GeV/c)^2, the Q^2 dependence of the
moments is predominantly governed by the elastic contribution, whereas the
inelastic channels still seem governed by local duality.Comment: 11 page paper, 1 LaTeX file, 10 postscript figure file
Quark-hadron duality in a relativistic, confining model
Quark-hadron duality is an interesting and potentially very useful
phenomenon, as it relates the properly averaged hadronic data to a perturbative
QCD result in some kinematic regions. While duality is well established
experimentally, our current theoretical understanding is still incomplete. We
employ a simple model to qualitatively reproduce all the features of
Bloom-Gilman duality as seen in electron scattering. In particular, we address
the role of relativity, give an explicit analytic proof of the equality of the
hadronic and partonic scaling curves, and show how the transition from coherent
to incoherent scattering takes place.Comment: This paper is dedicated to the memory of our collaborator Nathan
Isgur. (34 pages, 13 figures
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