23,312 research outputs found
Strange Form Factors of Octet and Decuplet Baryons
The strange form factors of baryon octet are evaluated, in the chiral models
with the general chiral SU(3) group structure, to yield the theoretical
predictions comparable to the recent experimental data of SAMPLE Collaboration
and to study the spin symmetries. Other model predictions are also briefly
reviewed to compare with our results and then the strange form factors of
baryon octet and decuplet are predicted.Comment: 5 pages, Talk given at the 12th Nuclear Physics Summer School and
Symposium and the 11th International Light-Cone Workshop "New Directions in
QCD," 21-25 June 1999, Kyungju, Kore
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
Nucleon sigma term and strange quark content from lattice QCD with exact chiral symmetry
We calculate the nucleon sigma term in two-flavor lattice QCD utilizing the
Feynman-Hellman theorem. Both sea and valence quarks are described by the
overlap fermion formulation, which preserves exact chiral and flavor symmetries
on the lattice. We analyse the lattice data for the nucleon mass using the
analytical formulae derived from the baryon chiral perturbation theory. From
the data at valence quark mass set different from sea quark mass, we may
extract the sea quark contribution to the sigma term, which corresponds to the
strange quark content. We find that the strange quark content is much smaller
than the previous lattice calculations and phenomenological estimates.Comment: 27 page
Bundles of generalized theta functions over abelian surfaces
We study the bundles of generalized theta functions constructed from moduli
spaces of sheaves over abelian surfaces. In degree 0, the splitting type of
these bundles is expressed in terms of indecomposable semihomogeneous factors.
Furthermore, Fourier-Mukai symmetries of the Verlinde bundles are found,
consistently with strange duality. Along the way, a transformation formula for
the theta bundles is derived, extending a theorem of Drezet-Narasimhan from
curves to abelian surfaces
Isospin breaking in the vector current of the nucleon
Extraction of the nucleon's strange form factors from experimental data
requires a quantitative understanding of the unavoidable contamination from
isospin violation. A number of authors have addressed this issue during the
past decade, and their work is reviewed here. The predictions from early models
are largely consistent with recent results that rely as much as possible on
input from QCD symmetries and related experimental data. The resulting bounds
on isospin violation are sufficiently precise to be of value to on-going
experimental and theoretical studies of the nucleon's strange form factors.Comment: 5 pages, 3 figures. Presented at the International Workshop "From
Parity Violation to Hadronic Structure and more...", Milos, Greece, 16-20 May
2006. Version 2 is only to update Refs. [21] and [25
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