arXiv subjects

J. S. McCarthy

Publications and source records attributed to J. S. McCarthy.

3 recordsLinked to original sources

arXiv1997

Nucleon spin-flavor structure in SU(3) breaking chiral quark model

The SU(3) symmetric chiral quark model, which describes interactions between quarks, gluons and the Goldstone bosons, explains reasonably well many aspects of the flavor and spin structure of the proton, except for the values of $f_3/f_8$ and $Δ_3/Δ_8$. Introducing the SU(3)-breaking effect suggested by the mass difference between the strange and nonstrange quarks, we find that this discrepancy can be removed and better overall agreement obtained.

hep-ph↗

arXiv1996

F/D Ratios in Hyperon Beta Decays and Spin Distribution in the Nucleon

It is shown that hyperon beta decay data can be well accommodated within the framework of Cabbibo's SU(3) symmetric description if one allows for a small SU(3) symmetry breaking proportional to the mass difference between strange and nonstrange quarks. The F/D ratio does not depend sensitively on the exact form of the symmetry-breaking, and the best fits are close to the value previously used in the analysis of deep inelastic scattering of electrons or muons on polarized nucleons. The total quark helicity and strange quark polarization in the nucleon are discussed.

hep-ph↗

arXiv1994

Model Calculation of Nucleon Structure Functions

Deep inelastic polarized and unpolarized structure functions for a free nucleon are obtained in a modified Center-of-Mass bag model, which includes the symmetry breaking effects from spin-dependent interactions. The quark distribution functions, calculated at $Q_0^2\simeq$ (0.9GeV/c)$^2$, are evolved to higher $Q^2$ region and compared with the data and other models. The model gives a reasonable description for the valence part of the structure functions at $x>0.3$. For small-$x$ region, the contributions from the sea are necessary. The spin-dependent effects are important in describing the existing data.

hep-ph↗