Baryon production in the string fragmentation picture

An improved version of the “pop-corn” model for baryon production in quark and gluon jets is presented. With a reduced number of parameters the model reproduces well both production rates for different baryon species and baryon momentum distributions. Predictions are presented for a set of baryon-antibaryon correlations.     

Two-photon collisions in deep inelastic lepton-nucleon and lepton-nucleus scattering

We have calculated the μ-pair production via photon-photon collisions in deep-inelastic charged lepton scattering on proton and nuclei, using the equivalent photon approximation. Specific parametrizations were assumed for the proton and the nuclei form factors and the QED photon structure function. Results are given for lepton energies below 300 GeV and virtual photon massesQ ² less than 50 GeV², as functions of the μ-pair mass, the scaling variablex and the electric chargeZ of the hadron target. Using a photon structure function derived from QPM and VDM we also estimate the contribution of γγ collisions to hadron production in these deep inelastic processes.     

Deep inelastic lepton-nucleon scattering without point-like constituents

Neutrino- and antineutrino-nucleon scattering into hadrons is analyzed and related to electron-nucleon scattering according to a scaling model which has been recently proposed. The electromagnetic and weak structure functions are determined and explicitly given in terms of the πN total cross sections. Predictions are made in good agreement with experiments.     

Simulation of sextet diquark production

We present a method for simulating the production and decay of particles in the sextet representation of SU(3) _C including the simulation of QCD radiation. Results from the Monte Carlo simulation of sextet diquark production at the LHC including both resonant and pair production are presented. We include limits on resonant diquark production from recent ATLAS results and perform the first simulation studies of the less model dependent pair production mechanism.     

Diffractive production of vector mesons in lepton-nucleon reactions

We calculate cross sections for the production of vector mesons V in reactions if ? + N → ?' + V + N, ?, ?' = ν, e, μ, taking into account all presently known information from electroproduction of ?'s. This leads to considerable differences in results from previous calculations, often more than an order of magnitude. The results for the ? are then largely a translation of electroproduction data into ν predictions and they will provide a direct test of the relation of weak and electromagnetic currents. The y or Q² distributions for the ? are instructive. The prediction for the A₁ provides a direct test of the existence of the A₁ and of whether vector and axial vector currents materialize into particles in the same way. The detection of a B meson would provide direct evidence for second-class currents and a measurement of their strength. We estimate all F¹ production will account for at most 2% of the total ν cross section at FNAL energies, which must be multiplied by the muon semi-leptonic branching ratio (and possibly a factor of 2 for an axial vector F¹) to calculate its contribution to the dimuon event rate.     

Light cone constraints and two asymptotic domains in lepton-nucleon and meson-nucleon scattering

Effective bare masses of the “current-quarks” are estimated from some testable inequalities, linking deep inelastic lepton-nucleon structure functions and high energy meson-nucleon total cross-sections, derived on the basis of the light-cone commutators of the pseudoscalar densities of quark-field theory.     

Baryon recoil and the fragmentation regions in ultra-relativistic nuclear collisions

The maximum baryon and energy densities reached in the fragmentation regions of nuclear collisions are estimated with a new hydrodynamical model. Unlike previous models where recoil is included as a source term for the baryon current, in our model the baryon current is strictly conserved. The parameters of the model are furthermore adjusted to take into account the large baryon rapidity shifts observed recently in p + A → p + X. The implications for the production of high baryon density quark-gluon plasmas are discussed.     

Baryon polarization in low-energy unpolarized meson-baryon scattering

We compute the polarization of the final-state baryon, in its rest frame, in low-energy mesonbaryon scattering with unpolarized initial state, in unitarized BChPT. Free parameters are determined by fitting total and differential cross-section data (and spin-asymmetry or polarization data if available) for pK ⁻, pK ⁺ and pπ⁺ scattering. We also compare our results with those of leading-order BChPT.     

Baryon production in QCD jets

Recent data from several sources—Υ decays, high energy deep inelastic scattering,e ⁺ e ^? annihilation at PETRA—reveal substantial baryon production in QCD jets. We discuss the likely mechanisms within the context of QCD, and formulate experimental tests to distinguish amongst them.     

Quark and gluon jets in the breit frame of lepton-nucleon scattering

Gluon bremsstrahlung,q→Gq, and quark pair production from gluons,laggy, in deep inelastic reactions is investigated in the Breit frame (moving alongQ in the laboratory). These QCD effects diminish the overall forward momentum. There are also events with asingle largep _⊥ forward jet. One spectacular class of events is predicted in which no forward going hadrons emerge, in the Breit frame. These effects are not mimicked by nonperturbative (limitedp _⊥) parton jets at large but attainableQ ².     

Multiplicity distributions from quarks and diquarks in deep inelastic lepton-nucleon scattering

We present an analytic prediction for the full hadronic multiplicity distribution in deep-inelastic lepton-nucleon scattering. We obtain a distinctive relationship between the average multiplicity at any W and that in e⁺e^? annihilation.     

The role of nuclear binding in deep inelastic lepton-nucleon scattering

It is shown that the EMC-effect can be explained by the nuclear structure. The binding of nucleons is shown to play an important role. The contributions of mesons to the nuclear structure functions are discussed.