98 research outputs found
Hyperbolic calorons, monopoles, and instantons
We construct families of SO(3)-symmetric charge 1 instantons and calorons on
the space H^3 x R. We show how the calorons include instantons and hyperbolic
monopoles as limiting cases. We show how Euclidean calorons are the flat space
limit of this family.Comment: 11 pages, no figures 1 reference added Published version available
at: http://www.springerlink.com/content/k0j4815u54303450
First Order Vortex Dynamics
A non-dissipative model for vortex motion in thin superconductors is
considered. The Lagrangian is a Galilean invariant version of the
Ginzburg--Landau model for time-dependent fields, with kinetic terms linear in
the first time derivatives of the fields. It is shown how, for certain values
of the coupling constants, the field dynamics can be reduced to first order
differential equations for the vortex positions. Two vortices circle around one
another at constant speed and separation in this model.Comment: 22pages, no figures, tex fil
Probing gluon helicity distribution and quark transversity through hyperon polarization in singly polarized pp collisions
We study the polarization of hyperon in different processes in singly
polarized collisions, in particular its relation to the polarized parton
distributions. We show that by measuring hyperon polarization in particularly
chosen processes, one can extract useful information on these parton
distributions. We show in particular that, by measuring the
polarization in high direct photon production process, one can extract
information on the gluon helicity distribution; and by measuring the transverse
polarization of hyeprons with high in singly polarized reactions, one can
obtain useful information on the transversity distribution. We present the
numerical results obtained for those hyperon polarizations using different
models for parton distribution function and those for the spin transfer in
fragmentation processes.Comment: 25 pages, 8 figures, to appear in Phys. Rev.
Polarized inclusive leptoproduction, , and the hadron helicity density matrix, : possible measurements and predictions
We discuss the production of hadrons in polarized lepton nucleon interactions
and in the current jet fragmentation region; using the QCD hard scattering
formalism we compute the helicity density matrix of the hadron and show how its
elements, when measurable, can give information on the spin structure of the
nucleon and the spin dependence of the quark fragmentation process. The cases
of vector mesons and baryons are considered in more details
and, within simplifying assumptions, some estimates are given.Comment: 17 pages + 4 figures, plain LATeX, figures appended as uuencoded,
compressed postscript fil
Transverse spin effects in hadron-pair production from semi-inclusive deep inelastic scattering
First measurements of azimuthal asymmetries in hadron-pair production in
deep-inelastic scattering of muons on transversely polarised ^6LiD (deuteron)
and NH_3 (proton) targets are presented. The data were taken in the years
2002-2004 and 2007 with the COMPASS spectrometer using a muon beam of 160 GeV/c
at the CERN SPS. The asymmetries provide access to the transversity
distribution functions, without involving the Collins effect as in single
hadron production. The sizeable asymmetries measured on the NH_ target indicate
non-vanishing u-quark transversity and two-hadron interference fragmentation
functions. The small asymmetries measured on the ^6LiD target can be
interpreted as indication for a cancellation of u- and d-quark transversities.Comment: 13 pages, 4 figures, updated to the published versio
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