arXiv subjects
Publications and source records attributed to J. F. Gunion.
We compute the predictions of intrinsic charm for deep-inelastic scattering at high-Q^2 and compare to HERA data. With the inclusion of constraints from low-energy data, enhancements beyond the predictions of standard structure functions are very modest, but peaking in the leptoquark mass variable is present near 200 GeV. Ultimately, the ability of HERA to probe the intrinsic charm hypothesis could be very substantial.
I review the ability of the LHC (large hadron collider), NLC (next linear lepton collider) and FMC (first muon collider) to detect and study Higgs bosons, with emphasis on the Higgs bosons of extended Higgs sectors, especially those of the minimal supersymmetric standard model (MSSM). Particular attention is given to means for distinguishing the lightest neutral CP-even Higgs boson of the MSSM from the single Higgs boson of the minimal Standard Model (SM).
We derive a sum rule which shows how to extend LEP limits on the masses of the lightest CP-even and CP-odd Higgs bosons of a CP-conserving two-Higgs-doublet model to any two Higgs bosons of a general CP-violating two-Higgs-doublet model. We generalize the analysis to a Higgs sector consisting of an arbitrary number of Higgs doublets and singlets, giving explicit limits for the CP-conserving and CP-violating two-doublet plus one-singlet Higgs sectors.
I give an overview of the motivations for and theory/phenomenology of supersymmetry.
We outline issues examined and progress made by the Light Higgs Snowmass 1996 working group regarding discovering Higgs bosons and measuring their detailed properties. We focused primarily on what could be learned at LEP2, the Tevatron (after upgrade), the LHC, a next linear $\epem$ collider and a $\mupmum$ collider.
We summarize the potential of muon colliders to probe fundamental physics. $W^+W^-$, \bar tt, and $Zh$ threshold measurements could determine masses to precisions $ΔM_W = 6$ MeV, $Δm_t = 70$ MeV, and $Δm_h = 45$ MeV, to test electroweak radiative corrections. With $s$-channel Higgs production, unique to a muon collider, the Higgs mass could be pinpointed ($Δm_h < 1$ MeV) and its width measured. The other Higgs bosons of supersymmetry can be produced and studied by three methods. If instead the $WW$ sector turns out to be strongly interacting, a 4 TeV muon collider is ideally suited to its study.
We evaluate the prospects for measuring $BR(h\toγγ)$ for a Standard-Model-like Higgs boson at the Next Linear $e^+e^-$ Collider in the $e^+e^-\to Z^*\to Z h$ and $e^+e^-\toν_e\antiν_e h$ production modes. Relative merits of different machine energy/luminosity strategies and different electromagnetic calorimeter designs are evaluated. We emphasize the importance of measuring $BR(h\toγγ)$ in order to obtain the total width of a light Higgs boson and thereby the $b\anti b$ partial width that will be critical in discriminating between the SM Higgs and the Higgs bosons of an extended model.
A brief review of muon-collider $s$-channel Higgs physics in the Standard Model and its minimal supersymmetric extension is presented.
Precise determinations of the masses of the $W$ boson and of the top quark could stringently test the radiative structure of the Standard Model (SM) or provide evidence for new physics. We analyze the excellent prospects at a muon collider for measuring $M_W$ and $m_t$ in the $W^+W^-$ and $t\bar t$ threshold regions. With an integrated luminosity of 10 (100) fb$^{-1}$, the $W$-boson mass could be measured to a precision of 20 (6) MeV, and the top-quark mass to a precision of 200 (70) MeV, provided that theoretical and experimental systematics are understood. A measurement of $Δm_t=200$ MeV for fixed $M_W$ would constrain a 100 GeV SM Higgs mass within about $\pm 2$ GeV, while $ΔM_W=6$ MeV for fixed $m_t$ would constrain $m_h$ to about $\pm 10$ GeV.
We provide a mini-guide to some of the possible manifestations of weak scale supersymmetry. For each of six scenarios we provide a brief description of the theoretical underpinnings, the adjustable parameters, a qualitative description of the associated phenomenology at future colliders, comments on how to simulate each scenario with existing event generators.
We demonstrate that a measurement of the Bjorken process $e^+e^-, μ^+μ^-\to ZH$ in the threshold region can yield a precise determination of the Higgs boson mass. With an integrated luminosity of $100 fb^{-1}$, it is possible to measure the Higgs mass to within 60 MeV (100 MeV) for m_H=100 GeV (150 GeV).
We demonstrate that supersymmetric decays, as typified by the predictions of several GUT-scale boundary condition choices, do not prevent detection of $Z^* \to H^0A^0,H^+H^-$, at a $1-4$ TeV $e^+e^-$ or $μ^+μ^-$ collider operating at anticipated luminosity. For much of parameter space the relative branching ratios for various SUSY and non-SUSY decays can be measured with sufficient accuracy that different GUT-scale boundary condition choices can be distinguished from one another at a very high confidence level.
We delineate the techniques and prospects for using Higgs pair production in $e^+e^-$ or $μ^+μ^-$ collisions to probe GUT-scale boundary conditions in the minimal supersymmetric standard model.
Minijet production in $\sqrt{s} = 5.5$ TeV Pb+Pb collisions at the LHC is expected to produce a gluon-dominated plasma with large initial temperatures and energy densities. We discuss the implications of the high initial temperatures on the screening mass and on the relative suppression of members of the $Υ$ family. We demonstrate that $p_T$-dependence of the $Υ'/Υ$ ratio is only expected if a quark-gluon plasma with significant energy density is present, and that the precise dependence of this ratio will strongly constrain the QGP models. We also propose that the $p_T$ spectra of the $Υ$ resonances themselves will provide valuable information by comparing these spectra to that of the $Z$ boson, which should not be influenced by plasma production.
We examine the prospects for measuring the photon-photon branching ratio of a Standard-Model-like Higgs boson ($h$) at the Next Linear $e^+e^-$ Collider when the Higgs boson is produced via $W^+W^-$--fusion: $e^+e^-\toν_e \barν_e h$. In particular, we study the accuracy of such a measurement and the statistical significance of the associated signal as a function of the electromagnetic calorimeter resolution and the Higgs boson mass. We compare results for the $W^+W^-$--fusion production/measurement mode with the results obtained for the $e^+e^-\rightarrow Z^*\rightarrow Z h$ production/measurement mode in a parallel earlier study.
We demonstrate that there are regions of parameter space in the next-to-minimal (i.e. two-Higgs-doublet, one-Higgs-singlet superfield) supersymmetric extension of the SM for which none of the Higgs bosons are observable either at LEP2 with $\sqrt{s}=192 GeV$ and an integrated luminosity of $L=1000 inverse pb$ or at the LHC with $L=600 inverse fb$.
Doubly-charged Higgs bosons ($Δ^{--}/Δ^{++}$) appear in several extensions to the Standard Model and can be relatively light. We review the theoretical motivation for these states and present a study of the discovery reach in future runs of the Fermilab Tevatron for pair-produced doubly-charged Higgs bosons decaying to like-sign lepton pairs. We also comment on the discovery potential at other future colliders.
We demonstrate that the process $e^+e^-\to t\anti t h$ at the NLC provides a powerful tool for extracting the $t\anti t$ (Yukawa) couplings of the $\h$. In combination with the $\epem\to Z\h$ process, an accurate determination of the $ZZ$ coupling of the $\h$ is also possible. The resulting ability to distinguish different models of the Higgs sector is illustrated by detailed studies for two-Higgs-doublet models.