139 research outputs found
Perturbation of Burkholder's martingale transform and Monge--Amp\`ere equation
Let be a complex martingale difference in
where and \{\e_k\}_{k \geq 0} a sequence in We
obtain the following generalization of Burkholder's famous result. If and then
|\sum_{k=0}^n{(\{c} \e_k \tau) d_k}|_{L^p([0,1], \C^2)} \leq ((p^*-1)^2 +
\tau^2)^{\frac 12}|\sum_{k=0}^n{d_k}|_{L^p([0,1], \C)},
where is sharp and For the result is also true with sharp
constant for Comment: 45 pages, 13 figure
Fragmentation Function and Nucleon Transversity Distribution in a Diquark Model
Based on a simple quark-diquark model, we propose a set of unpolarized,
longitudinally polarized and transversely polarized fragmentation functions for
the by fitting the unpolarized production data in annihilation. It is found that the helicity structure of the obtained
fragmentation functions is supported by the all available
experimental data on the longitudinal polarization. Within the same
framework of the diquark model, the nucleon transversity distributions are
presented and consistent descriptions of the available HERMES data on the
azimuthal spin asymmetries in pion electroproduction are obtained. Furthermore,
the spin transfers to the transversely polarized in the charged
lepton DIS on a transversely polarized nucleon target are predicted for future
experiments.Comment: Talk given in a seminar of U. Santa Mari
Lambda Polarization in Polarized Proton-Proton Collisions at RHIC
We discuss Lambda polarization in semi-inclusive proton-proton collisions,
with one of the protons longitudinally polarized. The hyperfine interaction
responsible for the - and - mass splittings gives
rise to flavor asymmetric fragmentation functions and to sizable polarized
non-strange fragmentation functions. We predict large positive Lambda
polarization in polarized proton-proton collisions at large rapidities of the
produced Lambda, while other models, based on SU(3) flavor symmetric
fragmentation functions, predict zero or negative Lambda polarization. The
effect of and decays is also discussed. Forthcoming
experiments at RHIC will be able to differentiate between these predictions.Comment: 18 pages, 5 figure
- …