34,288 research outputs found
Strangeness contributions to nucleon form factors
We review a recent theoretical determination of the strange quark content of
the electromagnetic form factors of the nucleon. These are compared with a
global analysis of current experimental measurements in parity-violating
electron scattering.Comment: 5 pages, 6 figures; Talk presented at the International Workshop
"From Parity Violation to Hadronic Structure and more...", Milos, Greece, May
16-20, 200
Active geothermal systems with entrained seawater as analogues for low-sulphidation epithermal mineralization
The paradigm for low-sulphidation (LS) volcanic-arc associated mineralization is the active geothermal systems located along the Taupo Volcanic Zone (e.g. Broadlands). However, this analogue is inapt where fluid salinities are consistently in excess of 3.5 wt % NaCl. LS mineralization on Milos (Aegean arc) records high paleofluid-salinities. The δD and δ18O data do not exemplify 18O-shifted meteoric waters—typical of terrestrial geothermal systems. Nor is a submarine origin indicated—stable isotope data show mixing between meteoric, seawater and volcanic-arc gases. Strontium isotope data are comparable to a nearby active seawater-entrained geothermal system. These are features seen in hydrothermal systems associated with emergent volcanoes. For the Milos LS mineralization, high-salinity fluids show it cannot be explained by a Broadlands-type model. The absence of saliferous sequences and significant intrusive rocks preclude these as salinity sources. The similarities between paleo and active systems in terms of salinity, δD–δ18O and strontium isotope systematics strongly suggest that seawater is the main source for Na and Cl. We suggest geothermal systems, containing seawater, associated with emergent volcanoes are an alternative analogue for LS epithermal mineralization. Furthermore, they bridge the gap between submarine, and large-scale terrestrial geothermal systems—the modern analogues for VHMS and epithermal mineralisation in the scheme of intrusion-centered hydrothermal mineralization
Nucleon Form Factors of the Isovector Axial-Vector Current: Situation of Experiments and Theory
The theoretical and experimental status of the isovector axial-vector current
form factors G_A(q^2) and G_P(q^2) of the nucleon is reviewed. We also describe
a new calculation of these form factors in manifestly Lorentz-invariant chiral
perturbation theory (ChPT) with the inclusion of axial-vector mesons as
explicit degrees of freedom.Comment: 5 pages, 3 figures. Talk given by M. R. Schindler at the
International Workshop "From Parity Violation to Hadronic Structure and
more...", Milos, Greece, May 16-20, 200
Future Directions in Parity Violation: From Quarks to the Cosmos
I discuss the prospects for future studies of parity-violating (PV)
interactions at low energies and the insights they might provide about open
questions in the Standard Model as well as physics that lies beyond it. I cover
four types of parity-violating observables: PV electron scattering; PV hadronic
interactions; PV correlations in weak decays; and searches for the permanent
electric dipole moments of quantum systems.Comment: Talk given at PAVI 06 workshop on parity-violating interactions,
Milos, Greece (May, 2006); 10 page
Manifestation of the JLab proton polarization data on the behaviour of strange nucleon form factors
Special eight-resonance unitary and analytic model of nucleon electromagnetic
structure is used to analyze, first the classical proton form factor data
obtained by the Rosenbluth technique and then also the contradicting JLab
proton polarization data on the ratio with the
aim to investigate a manifestation of the latter on the strange nucleon form
factors behaviour.Comment: Latex, 9 pages, 3 figures. Talk given at the PAVI06 International
Workshop, 16-20 May, 2006, Milos, Greec
Comparison of different non-linear equations and corresponding unitarization schemes
Different forms of non-linear equations which mimic parton saturation in the
non-perturbative regime are examined. These equations lead to corresponding
unitarization schemes in the impact parameter representation of the hadron
scattering amplitude. It is shown how specific properties of the non-linear
equations reflect different features of the diffraction processes.Comment: 7 pages, 5 figures, needs PoS.cls and PoSlogo, contribution to the
proceedings of the International Workshop on Diffraction in High-Energy
Physics "DIFFRACTION 2006", Adamantas, Milos island, Greece, September 5 -
10, 200
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