The Structure of the Pion and Nucleon, and Leading Neutron Production at HERA

Attention is paid to recent results from the ZEUS Collaboration on the photo- and electro- production of leading neutrons in e^+ p collisions at HERA. Some implications for the structure of the pion and the nucleon are discussed.Comment: 10 pages with no figures, Latex, to be published in Nucl. Phys. B, available at http://www.physics.utoronto.ca/~levma

Leading Baryon Production At Hera

ribution indicative of the dominance of pion exchange. The leading baryon data exhibit a strong factorization behavior, consistent with both limiting fragmentation and particle exchanges. Simple particle exchange models of leading baryon production are in good agreement with the data. 1 Introduction The ZEUS and H1 collaborations have observed events with protons and neutrons carrying a large fraction xL of the proton beam energy 1;2 , but with small transverse momentum p T . The data come from samples where the the photon 's virtuality Q 2 spans a large range: from the transition region between photoproduction and deep inelastic scattering (0:1 ! Q 2 ! 0:8 GeV 2 ) to deep inelastic scattering Q 2 ? 2 GeV 2 . Leading baryon data

Considerations regarding the duality rotation.

Maxwel l's equations for the vacuum are invariant under the duality rotation; however, the significance of this invariance is not well understood. The purpose of this thesis is to consider the duality rotation in greater detail than has been done previously. The duality invariance of Maxwell's equations is discussed, and it is shown that the only duality invariants bilinear in the electric and magnetic fields are arbitrary linear combinations of the components of the stress-energy-momentum tensor. It is also shown that the most general linear field transformation which leaves Maxwell's vacuum equations invariant is the duality rotation. The usual Lagrangian density for the electromagnetic field does not exhibit duality invariance. It is shown, however, that if one takes the components of the electromagnetic field tensor as field variables, then the most general Lorentz invariant Lagrangian density bilinear in the electomagnetic fields and their first derivatives is determined uniquely by the requirement of duality invariance. The ensuing field equations are identical with the iterated Maxwell equations. It is further shown that in neutrino theory the Pauli transformation of the second kind corresponds to the duality rotation.Science, Faculty ofPhysics and Astronomy, Department ofGraduat