Glennys R. Farrar

Phenomenology of the production, decay, and detection of new hadronic states associated with supersymmetry☆

Supersymmetric theories involve spinorial partners for the gluons of QCD. If the symmetry breaking is such that they are massless or light, they probably combine with quarks to form families of new, relatively low-lying hadrinic states, which decay into ordinary hadrons and a new, neutrino-like particle. We discuss how present experiments can put limits on their production.

Bounds on R-hadron production from calorimetry experiments☆

Abstract Supersymmetry suggests that new families of hadrons (R-hadrons) may exist, with masses possibly in the GeV/c2 range. If so, relatively model-independent bounds on their pair-production in proton collisions can be obtained by careful calorimetry experiments. Preliminary results indicate an upper limit ⪅ 100 μb for the pN → RR + X cross section at √s = 27.5 GeV.

Parton distributions in hadrons and the cross sections for lepton pair production

Abstract A number of constraints, several new, are exploited to obtain realistic quark parton distributions for baryons and mesons. These distributions are used to make detailed predictions for NN or π N → l + l − + anything, potentially providing a quantitative test of the quark parton model. Differential cross sections for a single lepton observed in the final state are also given.

The nuclear size dependence of large momentum transfer scattering and quark interaction dynamics

Abstract A simple dynamical picture for hadron interactions is used to discuss the A dependence of large p ⊥ scattering and dilepton production. Observations in large p ⊥ experiments are explained. Important corrections to dilepton production cross sections are found, leading to acceptable agreement between colored-quark theory and experiment.

Neutrino and antineutrino proton scattering data and the ratio of down to up quarks in the proton

Abstract New data on the x-dependence of the ratio of down to up quarks in the proton are presented from neutrino and antineutrino experiments using the Fermilab 15-foot bubble chamber filled with hydrogen. The new data are in good agreement with existing data from electron scattering experiments performed at SLAC but are not accurate enough at large x to discriminate between the QCD prediction and a (1 − x) behavior as x → 1.

Experimental means for distinguishing models of large p⊥ inclusive scattering

Abstract The scaling behavior, and to some extent the magnitude, of the ratio γ π of large p⊥ direct photon and pion inclusive production cross sections are shown to provide an excellent means of determining the fundamental mechanism of large p⊥ scattering.

Widths of narrow mesons made from heavy quarks

Abstract We give predictions for the electronic widths of neutral vector mesons made from heavy quarks. Relying principally on dispersion relations and asymptotic freedom of QCD, these results are quite model-independent. Photonic and total hadronic widths of C -even mesons are also discussed.

High-energy fixed-angle elastic scattering

Abstract The leading behavior of high-energy, fixed-angle, hadron-hadron scattering is obtained in a model in which on-mass-shell colored quarks exchange colored gluons. The resultant differential cross sections are compared with the data, indicating that such a mechanism does not dominate the physical scattering process.

Supersymmetry in Nature

Nature is certainly Poincare invariant. However it is possible that her forces possess a much higher degree of space-time invariance than we have heretofore realized, such as invariance under transformations which relate fermions and bosons, so-called supersymmetry transformations(1). As will be explained below, exact supersymmetry of the forces (i.e., of the Lagrangian) as well as of the physical states requires bosons and fermions to come in mass-degenerate multiplets; evidently, nature does not exhibit such behavior. However it is nonetheless possible that nature is supersymmetric but that this is not manifest through degeneracy between bosons and fermions. Such a state of affairs is called spontaneously broken supersymmetry and occurs when the lowest energy state (the vacuum) is not super-symmetric even though the forces are(2).

e+e− → γ + Hadrons

Abstract We give the spectrum in momentum and angle of directly produced γs in e + e − → γ + hadrons, and show that in QCD if p ⊥ 2 of the recoil hadron jet relative to the photon is large, the leading logarithmic corrections to the lowest order result are absent. This process is therefore of great value in learning whether QCD actually governs quark dynamics.