2,153 research outputs found
Strangeness in the Meson Cloud Model
I review progress in calculating strange quark and antiquark distributions of
the nucleon using the meson cloud model. This progress parallels that of the
meson cloud model, which is now a useful theoretical basis for understanding
symmetry breaking in nucleon parton distribution functions. I examine the
breaking of symmetries involving strange quarks and antiquarks, including quark
- antiquark symmetry in the sea, SU(3) flavour symmetry and SU(6) spin-flavour
symmetry.Comment: 6 pages, 4 figures. Talk given at workshop "Achievements and New
Directions in Subatomic Physics: Workshop in honour of Tony Thomas' 60th
birthday," CSSM, Adelaide, South Australia, 15 - 19 February 2010
g1(x) and g2(x) in the Meson Cloud Model
We calculate the spin dependent structure functions g1(x) and g2(x) of the
proton and neutron. Our calculation uses the meson cloud model of nucleon
structure and includes the effects of kinematic terms which mix transverse and
longitudinal spin components. We find small corrections to the nucleon
structure functions, however these are significant for the neutron.Comment: 4 pages, contribution to DIS 05, Madison, Wisconsi
Mapping properties for the Bargmann transform on modulation spaces
We investigate mapping properties for the Bargmann transform and prove that
this transform is isometric and bijective from modulation spaces to convenient
Banach spaces of analytic functions.Comment: Pre-version, 21 page
The flavour asymmetry of polarized anti-quarks in the nucleon
We present a study of the flavour asymmetry of polarized anti-quarks in the
nucleon using the meson cloud model. We include contributions both from the
vector mesons and the interference terms of pseudoscalar and vector mesons.
Employing the bag model, we first give the polarized valence quark distribution
of the meson and the interference distributions. Our calculations show
that the interference effect mildly increases the prediction for \Delta
\dbar(x)-\Delta \ubar(x) at intermediate region. We also discuss the
contribution of `Pauli blocking' to the asymmetry.Comment: 22 pages, LaTex, 5 PS figures. Version to appear in Eur. Phys. J. C.
An appendix is added for expressions for the helicity dependent fluctuation
functions. An error in the programme for fluctuation function
f_{(\pi\rho)\Delta /N} is corrected, which increases numerical results by
about 10%. Unchanged conclusion
The quark - antiquark asymmetry of the strange sea of the nucleon
The strange sea of the proton is generally assumed to have quark - antiquark
symmetry. However it has been known for some time that non-perturbative
processes involving the meson cloud of the proton may break this symmetry.
Recently this has been of interest as it affects the analysis of the so-called
`NuTeV anomaly', and could explain the large discrepancy between the NuTeV
measurement of and the currently accepted value. In this
paper we re-examine strange - anti-strange asymmetry using the meson cloud
model. We calculate contributions to the strange sea arising from fluctuations
in the proton wavefunction to states containing either Lambda or Sigma hyperons
together with either Kaons or pseudovector mesons. We find that we
should not ignore fluctuations involving mesons in this picture. The
strange sea asymmetry is found to be small, and is unlikely to affect the
analysis of the Llewellyn-Smith cross section ratios or the Paschos-Wolfenstein
relationship.Comment: 12 pages, 3 figure
When the client is not the abuser, but one of the abused
The question of client confidentiality and reporting animal abuse is complicated when the client is not the abuser, and when the abuse (of both people and animals) may escalate precisely because it has been (or may be) reported
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