Probing Cold Dense Nuclear Matter Subedi, R; Shneor, R; Monaghan, P ...
Science (American Association for the Advancement of Science),
06/2008, Letnik:
320, Številka:
5882
Journal Article
Recenzirano
Odprti dostop
The protons and neutrons in a nucleus can form strongly correlated nucleon pairs. Scattering experiments, in which a proton is knocked out of the nucleus with high-momentum transfer and high missing ...momentum, show that in carbon-12 the neutron-proton pairs are nearly 20 times as prevalent as proton-proton pairs and, by inference, neutron-neutron pairs. This difference between the types of pairs is due to the nature of the strong force and has implications for understanding cold dense nuclear systems such as neutron stars.
The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron ...and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.
We present the first measurements of the eover -->p-->epgamma cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q(2) dependence (from 1.5 to 2.3 ...GeV(2)) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q(2). The helicity-independent cross section is also measured at Q(2)=2.3 GeV(2). We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation.
The spin-structure functions g1 and g2, and the spin-dependent partial cross-section σTT have been extracted from the polarized cross-sections differences, Δσ∥(ν,Q2) and Δσ⊥(ν,Q2) measured for the ...He3→(e→,e′)X reaction, in the E97-110 experiment at Jefferson Lab. Polarized electrons with energies from 1.147 to 4.404 GeV were scattered at angles of 6∘ and 9∘ from a longitudinally or transversely polarized 3He target. The data cover the kinematic regions of the quasi-elastic, resonance production and beyond. From the extracted spin-structure functions, the first moments Γ1‾(Q2), Γ2(Q2) and ITT(Q2) are evaluated with high precision for the neutron in the Q2 range from 0.035 to 0.24GeV2. The comparison of the data and the chiral effective field theory predictions reveals the importance of proper treatment of the Δ degree of freedom for spin observables.
Measurements of elastic electron scattering data within the past decade have highlighted two-photon exchange contributions as a necessary ingredient in theoretical calculations to precisely evaluate ...hydrogen elastic scattering cross sections. This correction can modify the cross section at the few percent level. In contrast, dispersive effects can cause significantly larger changes from the Born approximation. The purpose of this experiment is to extract the carbon-12 elastic cross section around the first diffraction minimum, where the Born term contributions to the cross section are small to maximize the sensitivity to dispersive effects. The analysis uses the LEDEX data from the high resolution Jefferson Lab Hall A spectrometers to extract the cross sections near the first diffraction minimum of
12
C at beam energies of 362 MeV and 685 MeV. The results are in very good agreement with previous world data, although with less precision. The average deviation from a static nuclear charge distribution expected from linear and quadratic fits indicate a 30.6% contribution of dispersive effects to the cross section at 1 GeV. The magnitude of the dispersive effects near the first diffraction minimum of
12
C has been confirmed to be large with a strong energy dependence and could account for a large fraction of the magnitude for the observed quenching of the longitudinal nuclear response. These effects could also be important for nuclei radii extracted from parity-violating asymmetries measured near a diffraction minimum.
We present measurements of the ep->ep pi^0 cross section extracted at two values of four-momentum transfer Q^2=1.9 GeV^2 and Q^2=2.3 GeV^2 at Jefferson Lab Hall A. The kinematic range allows to study ...the evolution of the extracted hadronic tensor as a function of Q^2 and W. Results will be confronted with Regge inspired calculations and GPD predictions. An intepretation of our data within the framework of semi-inclusive deep inelastic scattering has also been attempted.
We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_{1} of the neutron and 3He using a polarized 3He target in the ...four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c);{2}. Global duality is observed for the spin-structure function g_{1} down to at least Q;{2}=1.8 (GeV/c);{2} in both targets. We have also formed the photon-nucleon asymmetry A1 in the resonance region for 3He and found no strong Q2 dependence above 2.2 (GeV/c);{2}.
"Defines the challenges facing the movement and offers comprehensive prescriptions for its successful transformation."-The George Washington Law Review
A valuable analysis of the rise, fall, ...and--hopefully-the revival of unionism in America. The book distills into readable form a mass of legal and empirical analysis of what has been happening in the workplaces of the United States and other industrial democracies. Most important, Craver has drawn a blueprint of what must be done to save collective bargaining in this century-must reading for scholars, lawmakers, and, especially, union leaders themselves.-Paul C. Weiler, Harvard Law SchoolAuthor of Governing the Workplace: The Future of Labor and Employment Law
"A thoroughly researched, insightful, and readable look at why American unions have declined. . . . This is a very informative analyis of a vital topic, and it will have a multidisciplinary appeal to anyone interested in union- management relations.-Peter Feuille, Institute of Labor and Industrial Relations, University of Illinois
When employees at firms like Greyhound and Eastern Airlines walk out to protest wage and benefit reductions, they are permanently replaced and their representative labor unions destroyed. Every year, the threat or drama of a high-profile strike-in air traffic control towers, at Amtrak, or at Caterpillar-makes national headlines and, every year, several hundred thousand unrepresented American employees are discharged without good cause.
During the past decade, employer opposition to unions has increased. Industrial and demographic changes have eroded traditional blue-collar labor support, and class-based myths have discouraged organization among white-collar workers. As the American labor movement begins its second century, it is confronted by challenges that threaten its very existence. Is the decline of the American labor movement symptomatic of a terminal condition?
In this work, Charles Craver presents an incisive analysis of the current state of the American labor movement and a manifesto for how this crucial institution can be revitalized. Journeying with the reader from the inception of labor unions through their heyday and to the present, Craver examines the roots of their decline, the current factors which contribute to their dismal condition, and the actions that are needed--such as the recruitment of female and minority employees and appeals to white-collar personnel--that are necessary to ensure union viability in the 21st century.
Craver thoughtfully discusses what labor organizations must do to organize new workers, to enhance their economic and political power, and to adapt to modern-day advances and to an increasingly global economy. He also suggests changes that must be made in the National Labor Relations Act. This book is essential reading for lawyers, scholars, and policy-makers, as well as all those concerned with the future of the labor movement.
PDF
