475 research outputs found
The polarized EMC effect
Conference details: Quark confinement and the hadron spectrum VII : 7th Conference on Quark Confinement and the Hadron Spectrum, QCHS7, Ponta Delgada, Açores, Portugal, 2-7 September 2006 / José Emílio F. T. Ribeiro (ed.): pp. 248-250We calculate both the spin independent and spin dependent nuclear structure functions in an effective quark theory. The nucleon is described as a composite quark-diquark state, and the nucleus is treated in the mean field approximation. We predict a sizable polarized EMC effect, which could be confirmed in future experiments.W. Bentz, I. C. Cloet, and A. W. Thoma
Covariance, Dynamics and Symmetries, and Hadron Form Factors
We summarise applications of Dyson-Schwinger equations to the theory and
phenomenology of hadrons. Some exact results for pseudoscalar mesons are
highlighted with details relating to the U_A(1) problem. We describe inferences
from the gap equation relating to the radius of convergence for expansions of
observables in the current-quark mass. We recapitulate upon studies of nucleon
electromagnetic form factors, providing a comparison of the ln-weighted ratios
of Pauli and Dirac form factors for the neutron and proton.Comment: 9 pages, 2 figures. Contribution to proceedings of Workshop on
Exclusive Reactions at High Momentum Transfer, May 21-24, 2007, Jefferson
Lab, Newport News, V
Spin-dependent structure functions in nuclear matter and the polarized EMC effect
An excellent description of both spin-independent and spin-dependent quark
distributions and structure functions has been obtained with a modified
Nambu-Jona-Lasinio model, which is free of unphysical thresholds for nucleon
decay into quarks - hence incorporating an important aspect of confinement. We
utilize this model to investigate nuclear medium modifications to structure
functions and find that we are readily able to reproduce both nuclear matter
saturation and the experimental F^A_2N / F_2N ratio, that is, the EMC effect.
Applying this framework to determine g^A_1p, we find that the ratio g^A_1p /
g_1p differs significantly from 1, with the quenching caused by the nuclear
medium being about twice that of the spin-independent case. This represents an
exciting result, which if confirmed experimentally, will reveal much about the
quark structure of nuclear matter.Comment: 4 pages, 4 figure
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