Factorization in Semi-Inclusive Polarized Deep Inelastic Scattering

We calculate and analize the ${\cal{O}}(\alpha_s)$ one-particle inclusive cross section in polarized deep inelastic lepton-hadron scattering, using dimensional regularization and the HVBM prescription for $\gamma_5$. We discuss the factorization of all the collinear singularities related to the process, particularly those which are absorbed in the redefinition of the spin dependent analogue of the recently introduced fracture functions. This is done in the usual $\overline{MS}$ scheme and in another one, called $\overline{MS_p}$, which factorizes soft contributions and guarantees the axial current (non)conservation properties.Comment: 16 pages, figures included using FEYNMAN macr

Next to Leading Order Semi-inclusive Spin Asymmetries

We have computed semi-inclusive spin asymmetries for proton and deuteron targets including next to leading order (NLO) QCD corrections and contributions coming from the target fragmentation region. These corrections have been estimated using NLO fragmentation functions, parton distributions and also a model for spin dependent fracture functions which is proposed here. We have found that NLO corrections are small but non-negligible in a scheme where gluons are polarised and that our estimate for target fragmentation effects does not modify significantly charged asymmetries but affects the so called difference asymmetries.Comment: Latex, 14 pages, 6 figures in 4 Postcript file

On Charge Quantization and Abelian Gauge Horizontal Symmetries

Under the assumption that there exists a local gauge horizontal symmetry $G_H$ wich allows only for a top quark mass at tree level, we look for the constraints that charge quatization and the family structure of the standard model imposes on that symmetry.Comment: 13 pages, LaTeX, Acepted in Physics Letters

A Method to Determine the Tau Neutrino Helicity Using Polarized Taus

A method is presented to extract the tau neutrino helicity, or equivalently, the chirality parameter $\gamma_{\mathrm{VA}}$, independent of any tau polarization which may be present. The method is thus well-suited to measurements using taus produced from the $Z^0$ and is complementary to analyses using tau correlations since it provides the sign of the chirality parameter which is otherwise unavailable without recourse to lower energy experiments where taus are unpolarized. Results of Monte Carlo studies and comments regarding the use of the technique in experiments are also included.Comment: 13 pages, uuencoded postscript fil

Nuclear parton distributions at next to leading order

We perform a next to leading order QCD global analysis of nuclear deep inelastic scattering and Drell-Yan data using the convolution approach to parameterize nuclear parton densities. We find both a significant improvement in the agreement with data compared to previous extractions, and substantial differences in the scale dependence of nuclear effects compared to leading order analyses.Comment: 9 pages, 10 figure

Monopolium: the key to monopoles

Dirac showed that the existence of one magnetic pole in the universe could offer an explanation for the discrete nature of the electric charge. Magnetic poles appear naturally in most Grand Unified Theories. Their discovery would be of greatest importance for particle physics and cosmology. The intense experimental search carried thus far has not met with success. Moreover, if the monopoles are very massive their production is outside the range of present day facilities. A way out of this impasse would be if the monopoles bind to form monopolium, a monopole- antimonopole bound state, which is so strongly bound, that it has a relatively small mass. Under these circumstances it could be produced with present day facilities and the existence of monopoles could be indirectly proven. We study the feasibility of detecting monopolium in present and future accelerators

Order-

We analyze the order-α s 2 gluon initiated QCD corrections to semi-inclusive deep inelastic scattering. We focus in the most singular pieces of these corrections and discuss the prescription of overlapping singularities in more than one variable and their factorization. PACS: 12.38.BxPerturbative calculations – 13.85.NiInclusive production with identified hadron