R. Michael Barnett

Ultra-heavy particle production from heavy partons at hadron colliders

Abstract The existence of heavy partons in the proton can have important consequences for hard scattering processes at high-energy hadron colliders. Nevertheless, by naively using heavy-parton distribution functions, one may be double-counting, since the origin of the heavy partons is due to pair production from gluons inside the proton. Using perturbative QCD, we develop a technique by which heavy-parton distribution functions may be used in a consistent manner. We illustrate the technique with two examples of the production of ultra-heavy particles: heavy squark production due to gluino-quark fusion and heavy charged Higgs production via t b fusion.

DISCOVERING SUPERSYMMETRY WITH LIKE-SIGN DILEPTONS

Abstract Supersymmetry may be discovered at hadron colliders by searching for events similar to the quark signal of two isolated leptons. In the case of gluino production, the most distinguishing feature is that in half the events the two leading leptons have the same sign. We demonstrate the remarkable sensitivity of this gluino signature at both the Fermilab Tevatron Collider and at the Superconducting Siper Collider. Techniques for approximately determining the gluino mass are discussed.

The effect of 1Q2 and αs corrections on tests of QCD

We discuss in detail the use of the structure function F/sub 3/(x,Q/sup 2/) of deep-inelastic neutrino scattering for testing quantum chromodynamics. QCD is entirely consistent with all data. However, we show that higher-twist (order 1/Q/sup 2/) contributions, which are commonly neglected, can have a dramatic impact on interpretation of this result. At present the data are not accurate enough to determine the magnitudes of these 1/Q/sup 2/ contributions within the context of QCD. Furthermore, the possible presence of higher-twist terms makes it impossible to unambiguously detect the logarithmic Q/sup 2/ dependence and anomalous dimensions which distinguish QCD from hypothetical alternative theories. As a result, more precise data with higher Q/sup 2/ are needed to provide definitive tests of QCD. The corrections of second-order in ..cap alpha../sub s/ introduce fewer complications for testing QCD, and provide a useful context for understanding critical ambiguities in the definitions of ..cap alpha../sub s/ and ..lambda...

Implications of a light Higgs scalar

Phenomenological consequences of a light neutral Higgs scalar S (mass < 3.7 GeV) are explored in various two-Higgs-doublet models where some of the couplings are strongly enhanced. In one class of models the two-gluon decay mode is predominant, and decays into two muons are quite suppressed. A detailed analysis of the decay b → s + S is given. The consequences a light scalar for supersymmetric models are discussed.

The decay of the scalar neutrino

Abstract One major problem for supersymmetry has been the lack of any experimental motivation. Although scalar neutrinos are usually predicted to be among the lighter new particles, their presence has been expected to be hidden because of their decay into unobserved neutrals. We calculate the decays of the scalar neutrino and show that there may be a substantial rate into charged particles. These decay modes lead to very distinctive signatures for supersymmetry in e+e− physics and in W±, Z0 decays.

The source of trimuon events in neutrino scattering

Abstract A comprehensive study indicates that equally likely sources for trimuon events neutrino scattering are (a) charged heavy lepton production (with decay to three muons) and (b) simultaneous production of a neutral lepton (with decay to two muons) and a heavy quark (with decay to one muon). The sequential decay of a heavy quark to two muons is less likely. An intriguing model yielding simultaneous M0 and b quark production is proposed.

The Education and Outreach project of ATLAS : a new participant in physics education

The ATLAS experiment at the Large Hadron Collider at CERN has a substantial collaborative Education and Outreach project. This article describes its activities and how it promotes physics to students around the world.

Calculation and Phenomenology of Two Body Decays of Neutralinos and Charginos to W, Z, and Higgs Bosons

We give explicit formulas for the decays of the neutralinos and charginos of the minimal model of supersymmetry into other neutralinos and charginos plus a W, Z, or Higgs boson. The important features of these decays are illustrated and their phenomenological implications discussed. In general, this class of two-body decays is dominant for the heaviest charginos and neutralinos.

Is the strong-coupling constant small?☆

Abstract It is important to examine the strong-coupling parameter Λ in deep-inelastic scattering, since (e.g.) the proton lifetime in grand-unified theories is quite sensitive to Λ. We show that Λ is not as small in μN scattering as previously reported. Furthermore, Λ extracted from F2(x, Q2) os highly correlated with the parameterization of the gluon distribution. Other problems arise from σL/σT assumptions.

GLUINO DECAYS TO W AND Z BOSONS AT THE SSC

It is shown that, for a wide range of parameters, the dominant decays of gluinos with mass ≳500 GeV contain gauge bosons, W± and Z, among their decay products. The pair production of heavy gluinos at the SSC is thus characterized by events with 3–4 hard jets and pairs of gauge bosons. The cleanest signature comes from the case where both gluinos decay into Z followed by which leads to ~50–100 4-lepton + multijet events annually at the SSC. In addition, 1600 trilepton + multijet and about 6000 dilepton + multijet events may be expected from WZ and WW sources. The backgrounds to these signals are estimated to be small.