[en] Experimental evidence indicates that the top quark exists and has a mass between 50 and 200 GeV/c². The decays of a top quark with a mass in this range are studied with emphasis placed on the mass region near the threshold for production of real W bosons. Topics discussed are: (1) possible enhancement of strange quark production when M_W + m_s < m_t < M_W + m_b; (2) exclusive decays of T mesons to B and B* mesons using the non-relativistic quark model; (3) polarization of intermediate W's in top quark decay as a source of information on the top quark mass. The production of heavy top quarks in an e⁺e^- collider with a center-of-mass energy of 2 TeV is studied. The effective-boson approximation for photons, Z⁰'s and W's is reviewed and an analogous approximation for interfaces between photons and Z⁰'s is developed. The cross sections for top quark pair production from photon-photon, photon-Z⁰, Z⁰Z⁰, and W⁺W^- fusion are calculated using the effective-boson approximation. Production of top quarks along with anti-bottom quarks via γW⁺ and Z⁰W⁺ fusion is studied. An exact calculation of γe⁺ → bar νt bar b is made and compared with the effective-W approximation. 31 refs., 46 figs

[en] Models of electroweak symmetry breaking with more than a single doublet of Higgs scalars contain a neutral pseudoscalar boson. The production of such a pseudoscalar in hadron collisions proceeds primarily via gluon fusion through a top-quark loop (except for those models in which the pseudoscalar coupling to bottom quarks is strongly enhanced). The authors compute the QCD corrections to this process in the heavy-quark limit, using an effective Lagrangian derived from the axial anomaly

[en] The transverse-momentum distribution of Higgs bosons produced via gluon fusion is calculated. The calculation matches multiple-gluon resummation at small p_T with the lowest-order calculation at high p_T. The full dependence on the top-quark mass is retained and the shape of the distribution at small p_T is shown to be independent of m_t

[en] The production of top quarks at an e⁺e^- collider with a center-of-mass energy of 2 TeV is discussed. Production cross sections for vector-boson fusion processes are calculated using the effective-boson approximation. Included are γγ, WW, γZ, and ZZ fusion production of top-quark pairs and production of t-bar b pairs by γW and ZW fusion. The cross sections for top-quark production from the interactions of beamstrahlung photons are presented

[en] CDF is just completing its analysis of the transverse momentum distribution of singly produced W's or Z's. It is important to have the best possible theoretical predictions to compare against experiment across the entire range of transverse momentum q_T. Previously, theoretical predictions to next-to-leading order in α_s have been restricted to the low-q_T and high-q_T limits. We take the O(α_s²) result at large q_T, the corresponding soft gluon resummation at low q_T, and consistently match them to obtain a result valid to next-to-leading order at all q_T. We present numerical results for W and Z production at √s=630 GeV and 1.8 TeV. Our analysis also provides a new and independent theoretical test of the formalism of resummation in Drell-Yan processes. (orig.)

[en] Higher-order corrections to the transverse-momentum distribution of Higgs bosons produced via gluon fusion are calculated. The calculation produces a spectrum including multiple-gluon effects normalized to next-to-leading order in α_s

[en] We compute analytic results for the QCD corrections to Higgs boson production via gluon fusion in hadronic collisions in the limit in which the top quark is much heavier than the Higgs boson. The first nonleading corrections of O(α_s³M_H²/m_t²) are given and numerical results presented for both CERN LHC and SSC energies. We confirm earlier numerical results showing that the dominant corrections have the same mass dependence as the Born cross section

[en] At the Superconducting Supercollider W-boson pairs coming from t bar t→b bar bW⁺W^- provide a serious background to the detection of the Higgs boson through the decay H→W⁺W^-→lν+2 jets, a mode crucial to the study of longitudinal W's in the TeV region. Considering a Higgs-boson mass of 1 TeV and a top-quark mass of 175 GeV we develop a set of cuts which yield a final signal-to-background ratio of approximately 3:1 and about 300 signal events. Most effective are the requirements of lepton isolation and high transverse momentum for the lepton and jets

[en] Models of electroweak symmetry breaking with more than a single doublet of Higgs scalars contain a neutral pseudoscalar boson. The production of such a pseudoscalar in hadron collisions proceeds primarily via gluon fusion through a top-quark loop (except for those models in which the pseudoscalar coupling to bottom quarks is strongly enhanced). We compute the QCD corrections to this process in the heavy-quark limit, using an effective Lagrangian derived from the axial anomaly

[en] We consider the production of a standard model Higgs boson accompanied by two jets in hadronic collisions. We work in the limit that the top quark is much heavier than the Higgs boson and use an effective Lagrangian for the interactions of gluons with the Higgs boson. In addition to the previously computed four-gluon process, we compute the amplitudes involving two quarks, two gluons, and the Higgs boson and those involving four quarks and the Higgs boson. We exhibit the form of our results in the small-p_H and factorization limits. We present numerical results for √(S)=14 TeV and √(S)=2 TeV. We find that the dominant processes are gg→ggH and qg→qgH with the former (latter) contributing about 60% (40%) of the cross section at √(S)=14 TeV and the two processes each contributing about half the cross section at √(S)=2 TeV. All other processes are negligible at both energies. copyright 1997 The American Physical Society