[en] A light neutral Higgs boson in the framework of the general two Higgs doublet model (2HDM) is not excluded by existing data. We point out that it can be looked for at the proposed low energy γγ collider. Failure to detect one may lead to important limits on the parameters of the general 2HDM. copyright 1997 The American Physical Society

[en] For an intermediate mass Higgs boson with SM-like couplings the CERN LHC allows observation of a variety of decay channels in production by gluon fusion and weak boson fusion. Cross section ratios provide measurements of various ratios of Higgs couplings, with accuracies of order 15% for 100 fb^-1 of data in each of the two LHC experiments. For Higgs boson masses above 120 GeV, minimal assumptions on the Higgs sector allow for an indirect measurement of the total Higgs boson width with an accuracy of 10 to 20 %, and of the H→WW partial width with an accuracy of about 10%. (c) 2000 The American Physical Society

[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

[en] We consider a general effective Lagrangian for couplings of a Higgs boson to the top quark to dimension-six operators including CP violation effects. Constraints on some of them are derived from the Z→bb(bar sign) data. We study the process e⁺e^-→tt(bar sign)H to probe the nonstandard couplings. We find that at a linear collider with a c.m. energy √(s)∼0.5-1.5 TeV and a high luminosity of 10-1000 fb^-1, these non-standard couplings may be sensitively probed. (c) 1999 The American Physical Society

[en] The t W^- mode of single top quark production is proposed as an important means to study the weak interactions of the top quark. While the rate of this mode is most likely too small to be observed at run II of the Fermilab Tevatron, it is expected to be considerably larger at the CERN LHC. In this article the inclusive t W^- rate is computed, including O(1/log m_t²/m_b²) corrections, and when combined with detailed Monte Carlo simulations, including the top quark and W decay products, indicates that the t W^- single top quark process may be extracted from the considerable t t(bar sign) and W⁺ W^- j backgrounds at low luminosity runs of the LHC. (c) 1999 The American Physical Society

[en] We calculate the O(α_ewm_t(b)²/m_W²) and O(α_ewm_t(b)⁴/m_W⁴) supersymmetric electroweak corrections to the cross section for charged Higgs boson production in association with a top quark at the Fermilab Tevatron and the CERN large hadron collider (LHC). These corrections arise from the quantum effects which are induced by potentially large Yukawa couplings from the Higgs sector and the chargino-top-quark- (bottom-quark-) bottom-squark (top-squark) couplings, neutralino-top-quark- (bottom-quark-) top-squark (bottom-squark) couplings and charged Higgs-boson-top-squark-bottom-squark couplings. They can decrease or increase the cross section depending on tan β but are not very sensitive to the mass of the charged Higgs boson for high tan β. At low tan β(=2) the corrections decrease the total cross sections significantly, exceeding -12% for m_H^± below 300 GeV at both the Tevatron and the LHC, but for m_H^±>300 GeV the corrections become very small at the LHC. For high tan β(=10,30) these corrections can decrease or increase the total cross sections, and the magnitude of the corrections are at most a few percent at both the Tevatron and the LHC. (c) 2000 The American Physical Society

[en] We present a measurement of the differential cross section as a function of transverse momentum of the Z boson in pp(bar sign) collisions at √(s)=1.8 TeV using data collected by the DOe experiment at the Fermilab Tevatron Collider during 1994-1996. We find good agreement between our data and the next-to-next-to-next-leading-logarithmic resummation prediction and extract values of the non-perturbative parameters for the resummed prediction from a fit to the differential cross section. (c) 2000 The American Physical Society

[en] We evaluate the prospects for detecting a non-standard light Higgs boson with a significant branching ratio to two photons, in run II of the Fermilab Tevatron. We derive the reach for several channels: 2γ inclusive, 2γ+1 jet, and 2γ+2 jets. We present the expected run II limits on the branching ratio of h→γγ as a function of the Higgs boson mass, for the case of ''bosonic,'' as well as ''top-color'' Higgs bosons. (c) 2000 The American Physical Society

[en] We have made a detailed study of the signals expected at CERN LEP 2 from charged scalar bosons whose dominant decay channels are into four fermions. The event rates as well as kinematics of the final states are discussed when such scalars are either pair produced or are generated through a tree-level interaction involving a charged scalar, the W, and the Z. The backgrounds in both cases are discussed. We also suggest the possibility of reconstructing the mass of such a scalar at LEP 2. copyright 1997 The American Physical Society

[en] We describe a method to help the search for a light top squark (M_t+M_LSPt) at the Fermilab Tevatron. Traditional search methods rely upon a series of stringent background-reducing cuts which, unfortunately, leave very few signal events given the present data set. To avoid this difficulty, we instead suggest using a milder set of cuts, combined with a open-quotes superweight,close-quote close-quote whose purpose is to discriminate between signal and background events. The superweight consists of a sum of terms, each of which are either zero or one. The terms are assigned event-by-event depending upon the values of various observables. We suggest a method for choosing the observables as well as the criteria used to assign the values such that the superweight is open-quotes large close-quote close-quote for the supersymmetric signal and open-quotes small close-quote close-quote for the standard model background. For illustration, we mainly consider the detection of tops squarks coming from top quark decay, making our analysis especially relevant to the W+2 jets top quark sample. copyright 1997 The American Physical Society