P.M. Zerwas

Production and decay properties of ultra-heavy quarks☆

Abstract The widths of ultra-heavy quarks that can be decay into W, Z or Higgs bosons are discussed. If the lifetimes become much shorter than the typical strong interaction time scale Λ −1 QCD ∼ 10 −23 s, then open-flavor hadrons and quarkonium bound states cannot be formed any more. Consequences for the jet evolution are investigated. On the other hand, if such quarks can decay only through tiny mixing angles - as it could happen for sequential down-type quarks and for SU(2) singlet quarks in E 6 models - then these bound states do form. Production rates for quarkonia in e + e - annihilation and in hadronic collisions are estimated and their decay signatures are discussed.

Deep inelastic electron-proton scattering

We study deep inelastic scattering of an electron or positron on an almost real photon target in the reaction e+e− → e+e− + hadrons with C = +, where one e+ or e− is scattered at small or zero angle, yielding a virtual photon γ(k), k2 ∼ O(−me2). The other e− or e+ scatters on this virtual photon, emerging at large angle. We emphasize particularly: (i) the pointlike QCD contribution to the structure functions of the photon; (ii) the measurability of the structure functions under realistic experimental conditions; (iii) the background from the inelastic Compton process e+e− → e+e− + hadrons with C = −, which we find is controllable.

QCD Corrected Forward Backward Asymmetry of Quark Jets in e+ e- Annihilation

Abstract The first order QCD corrections to the forward-backward asymmetry of quark jets produced in e+e− annihilation via γ and Z exchange are calculated. The quarks from which the jets develop are assumed to be heavy. The difference between the forward and backward scattering cross section is shown to be of order μαS, μ being the quark mass in units of the beam energy.

The interquark potential: SU(2) colour gauge theory with fermions

Abstract Including dynamical fermions in the Monte Carlo simulation of the SU(2) gauge theory, the potential between static quarks is investigated on a 16×83 lattice. The Coulomb part of the force is stronger as compared with the pure gauge field theory. At large distances indications are found for a deviation from the linear rise of the potential, expected from a break-up of the flux tube between the heavy quarks through spontaneous creation of light quark pairs.

A model for dileptons in neutrino reactions

Abstract We have constructed a detailed parton model for dileptons originating in the production and decay of “charmed” particles in high-energy neutrino interactions. Distributions are calculated for the primary and secondary lepton, and for the hadronic shower accompanying them. The model is able to account successfully for all prominent features of the dimuon data obtained so far, and yields significant clues to the structure of the charm-changing current underlying this phenomenon.

Angular Asymmetries in Hadron Distributions of Neutrino - Nucleon Reactions in Quantum Chromodynamics

Abstract Gluon corrections to the quark-parton model of deep-inelastic lepton-nucleon scattering induce angular asymmetries in the distributions of the final-state hadrons. We determine these asymmetries for semi-inclusive pion production in high-energy neutrino- and antineutrino-nucleon scattering.

Neutrino-excitation of C+0(2260) and tests of the charmed current structure

Abstract The production and decay of the charmed baryon state C 0 + , via the reactions v μ + N → μ − + C 0 + , C 0 + → Λ 0 e + v e , produces a final state that is uniquely identifiable by its μ − e + Λ 0 signature. The polarization of the C 0 + will depend sensitively on the chiral and SU(4) structure of the charmed current, and will produce a characteristic asymmetry in the distribution of the decay products. We calculate in this paper the polarization expected in the Glashow-Iliopoulos-Maiani theory, and the resulting asymmetry in the angular distribution of the Λ 0 .

The three-gluon vertex of QCD

Abstract We show how the Q2 evolution of gluon jets can be used to provide indirect but strong evidence for the three-gluon vertex of QCD. We propose looking for this evolution in the Q Q ¯ → 3 G → hadrons decay of successive 1 3S1 quarkonium states. The results apply to other processes if G-jets can be isolated.

The interquark potential

Abstract We report on a measurement of the potential between static quarks in full lattice QCD at small quark masses. The calculation is carried out on a 24 × 163 lattice at β = 5.35 and 5.15 with a quark mass am = 0.010 employing the hybrid Monte Carlo method for NF = 4 dynamical fermions. The results are compared to the potential calculated in the quenched approximation on the same size lattice in a β range from 5.7 to 6.0. Screening effects and the ambiguities in β-shifts for observables such as hadron masses, the quark condensate and the string tension will be discussed.

ϱ, π Masses and chiral symmetry breaking: SU(2) colour gauge theory with dynamical fermions☆

Abstract The masses of ϱ, π mesons and the quark condensate 〈 q q〉 are investigated in a Monte Carlo simulation of the SU(2) colour gauge theory including dynamical Kogut-Susskind fermions on a 16×83 lattice. When extrapolated to zero quark mass, we find a finite ϱ mass value, but a π mass compatible with zero, and a non-zero value of the quark condensate, signalling spontaneous breaking of chiral symmetry in non-abelian gauge theories.