We discuss the determination of polarized parton distributions from a NLO analysis of recent experimental data. We extract the first moment of the polarized quark and gluon distribution and assess the corresponding uncertainties, with special regard to those related to scheme dependence. Talk given at DIS96, Rome, April 1996 to be published in the proceedings

Two broad charmed mesons, the D∗ 0 and D ′ 1, have recently been observed. We examine the quark model predictions for the D∗ 0 and D ′ 1 properties and discuss experimental measurements that can shed light on them. We find that these states are well described as the broad, j = 1/2 non-strange charmed P -wave mesons. Understanding the D∗ 0 and D ′ 1 states can provide important insights into the...

Leptoquarks arise naturally in models attempting the unification of the quark and lepton sectors of the standard model of particle physics. Such particles could be produced in the interaction of high energy quasi-horizontal cosmic neutrinos with the atmosphere, via their direct coupling to a quark and a neutrino. The hadronic decay products of the leptoquark, and possibly its leptonic decay pro...

A heavy quark effective field lagrangian keeping particle and antiparticle mixed sectors * Abstract We examine the applicability of the heavy-quark effective field theory (HQEFT) to heavy quark-antiquark pair annihilation or creation processes. To this end, we keep the particle-antiparticle sector in the inverse heavy-quark mass expansion of the HQEFT Lagrangian. We show that by removing the la...

We reconsider the massless up quark solution of the strong CP problem. We show that an anomaly free horizontal symmetry can naturally lead to a massless up quark and to a corresponding accidental anomalous symmetry. Reviewing the controversy about the phenomenological viability of m u = 0 we conclude that this possiblity is still open and can solve the strong CP problem.

We show that solutions for the masses and mixings of the quarks and leptons based on a U (1)×Z 2 horizontal symmetry are possible. The seesaw mechanism is shown to work consistently in the presence of the discrete symmetry. The discrete symmetry results in the phenomenologically useful suppressions of elements of the Yukawa matrices. The quark and lepton masses, the CKM mixing angles, and the n...

We review some recent results on heavy quark production in high energy hadronic collisions. We will discuss in particular the status of production cross sections for bottom quarks and charmonium states and will present some studies on the production of bottom and charm jets, at the inclusive level and in association with electroweak gauge bosons.

It is shown that the quark–gluon interaction induced by instan-tons leads to the quark anomalous chromomagnetic moment. In the instanton-liquid model for the QCD vacuum, the chromomagnetic moment is µ a = − πf 2αs , where f is the packing fraction of instantons in the vacuum.

This paper presents an overview of the physics program of the 15-30 GeV continuous beam electron facility proposed by the European community of nuclear physicists to study the quark and gluon structure of hadrons. The goal of this new facility is to explore the quark structure of matter by exclusive and semi-inclusive electron scattering from nuclear targets.