arXiv subjects
Publications and source records attributed to J. F. Gunion.
We demonstrate that supersymmetric decay modes of the neutral Higgs bosons of the MSSM could well make their detection extremely difficult when produced singly in $\gam\gam$ collisions at a back-scattered laser beam facility.
I present a brief review of prospects for discovering supersymmetry, focusing primarily on the Tevatron and LEPII, but commenting on the LHC and a next linear $\epem$ collider. Special emphasis is given to expectations in the context of models with GUT boundary conditions motivated by Supergravity and Superstrings. An overview of related conference contributions is given.
The ability of LEP-200, the Tevatron, the Di-Tevatron, the LHC, and a next linear $\epem$ collider (NLC) to probe the Higgs sectors of the minimal Standard Model (SM) and the Minimal Supersymmetric Model (MSSM) is reviewed. Emphasis is placed on newly developed detection modes and on predictions for supersymmetric particle Higgs decay channels when the MSSM is constrained using boundary conditions motivated by supergravity/superstring models.
We explore the ability of the Tevatron to probe Minimal Supersymmetry with high energy scale boundary conditions motivated by supersymmetry breaking in the context of supergravity/superstring theory. A number of boundary condition possibilities are considered: dilaton-like string boundary conditions applied at the standard GUT unification scale or alternatively at the string scale; and extreme (``no-scale'') minimal supergravity boundary conditions imposed at the GUT scale or string scale. For numerous specific cases within each scenario the sparticle spectra are computed and then fed into ISAJET 7.07 so that explicit signatures can be examined in detail. We find that, for some of the boundary condition choices, large regions of parameter space can be explored via same-sign dilepton and isolated trilepton signals. For other choices, the mass reach of Tevatron collider experiments is much more limited. We also compare mass reach of Tevatron experiments with the corresponding reach at LEP 200.
We explore the possibility of a fourth generation in the gauge-coupling-unified, minimal supersymmetric (MSSM) framework. We find that a sequential fourth generation (with a heavy neutrino $ν'$) can still fit, surviving all present experimental constraints, provided $λ_b(M_U)=λ_τ(M_U)$ Yukawa unification is relaxed. For the theory to remain perturbative up to $M_U$, the new leptonic generation must lie within reach of LEP-II and the new $b',t'$ must have masses within the reach of the Tevatron. For example, for $\mt>150\gev$ we find $m_{ν'},m_{τ'}< 86\gev$, $m_{t'}<178$, and $m_{b'}<156\gev$. Experiments at Fermilab are already sensitive to the latter mass regions; we comment on direct $b'$ searches and on the $m_{t'}\simeq \mt$ case in light of new CDF data. Discovery may involve novel decay signatures; however, CDF and LEP-II will confirm or exclude an MSSM fourth generation in the near future.
We determine the optimal laser and $\ep/\em$ energies and polarizations for {\it directly} determining the CP eigenvalue of each of the neutral Higgs bosons of the Minimal Supersymmetric Model via measurement of transverse polarization cross section asymmetry in back-scattered laser photon collisions. Approximate statistical significances are computed for the measurement of the CP eigenvalue as a function of Higgs mass and other parameters of the model.
We demonstrate that the distinctive features of the forward differential cross section of diffractive leptoproduction of a vector meson can be legitimately calculated in perturbative QCD in terms of the light-cone $q \bar q$ wave function of the vector meson and the gluon distribution of the target. In particular, we calculate the $Q^2$ and nuclear dependence of the diffractive leptoproduction of vector mesons and estimate the cross section. The production of longitudinally polarized vector mesons by longitudinally polarized virtual photons is predicted to be the dominant component, yielding a cross section behaving as $Q^{-6}$. The nuclear dependence of the diffractive cross sections, which follows from a factorization theorem in perturbative QCD, provides important tests of color transparency as well as constraints on the shadowing of the gluon structure functions and the longitudinal structure functions of nuclei.
We compute an array of Standard Model Higgs boson ($\hsm$) signals and backgrounds for a possible upgrade of the Tevatron to $E_{\rm cm}=4\tev$. Taking $\mt\geq 140\gev$, and assuming a total accumulated luminosity of $L=30\fbi$, we find that a Standard Model Higgs boson with $\mhsm\lsim 110\gev$ could almost certainly be detected using the $\wpm\hsm\rta lνb\anti b$ mode. A Higgs boson with mass between $\sim 120\gev$ and $\sim 140\gev$ or above $\sim 230-250\gev$ almost certainly would not be seen. A Higgs boson with $\mhsm\sim 150\gev$ or $200\lsim\mhsm\lsim 230-250\gev$ has a decent chance of being detected in the $ZZ\rta 4l$ mode. There would also be some possibility of discovering the $\hsm$ in the $WW\rta lνjj$ mode for $150\lsim\mhsm\lsim 200\gev$. Finally, hints of an event excess in the $WW\rta ll νν$ mode due to the $\hsm$ might emerge for $140\lsim\mhsm\lsim 180\gev$. Given the difficult nature of the Higgs boson signals for $\mhsm$ values beyond the reach of LEP-200, and the discontinuous $\mhsm$ range that could potentially be probed, justification of an upgrade of the Tevatron to $4\tev$ on the basis of its potential for Standard Model Higgs boson discovery would seem inappropriate.
We explore the prospects for detection of sparticles and Higgs bosons at the Tevatron, LEP-200 and the LHC in the allowed parameter space of a `yukawa unified' ($λ_b(M_U)=λ_τ(M_U)$) minimal supergravity (YUMS) model, where the only non-zero unification scale soft-SUSY-breaking terms are a universal gaugino mass and a Higgs mixing term. In a bottom-up approach, just two weak scale parameters, $\tanb$ and $\mha$, (along with the sign of the Higgs mixing parameter $μ$) completely parameterize the model. Many interesting `special' situations regarding sparticle and Higgs discovery arise, such as the importance of the invisible $\hl\rta\cnone\cnone,\snu\snubar$ decay modes.
We demonstrate that detection of a charged Higgs boson decaying via $\hpm\rta t b$ will be possible at the LHC in $gg\rta \hm t \anti b+\hp b\anti t$ events, provided the $\hp\rta t\anti b$ coupling is substantial, $\mt\gsim 110\gev$, and reasonably efficient and pure $b$-tagging can be performed.
We demonstrate that an invisibly decaying Higgs boson with Standard Model coupling strength to top--anti-top can be detected at the LHC for masses up to about 250 GeV.
I review new developments in Higgs physics and electroweak symmetry breaking that have resulted from the Madison--Argonne workshops on SSC physics.
We demonstrate that expected efficiencies and purities for $b$-tagging at SSC/LHC detectors may allow detection of the Standard Model Higgs in $t\anti t \hsm$ production, with $\hsm\rta b\anti b$ decay, for $80\lsim\mhsm\lsim 130\gev$, provided $\mt\gsim 130\gev$.
I briefly review the crucial role an $\emem$ linear collider could play in unravelling the nature of a non-minimal Higgs sector and/or strongly-interacting $WW$ sector.
I review recent developments in the theory and phenomenology of Higgs bosons at an $\epem$ linear collider with $\sqrt s$ of order 500 GeV.
We demonstrate that expected efficiencies and purities for $b$-tagging at SSC/LHC detectors should allow detection of at least one of the Higgs bosons of the Minimal Supersymmetric Model in $t\anti t$~Higgs production, with Higgs$\rta b\anti b$ decay, over a substantial range of supersymmetric parameter space. In particular, with the addition of this mode to those previously considered, there is no region of supersymmetric parameter space for which {\it none} of the Higgs bosons of the model can be seen at the SSC/LHC.
I summarize the abilities of LEP-II, the SSC/LHC hadron colliders, and a future high energy $\epem$ collider (NLC) to detect the Higgs bosons of the Minimal Supersymmetric Model (MSSM). I then review the unique capabilities of a back-scattered laser beam facility (BSLBF) at the NLC for detecting the heavier neutral Higgs bosons (the $\hh$ and $\ha$) of the MSSM. A BSLBF could well allow $\hh$ and $\ha$ discovery via inclusive $\gam\gam\rta \hh,\ha$ production out to masses of order $0.8\sqrt s$, \ie\ roughly $400\gev$, at the NLC. In addition, a BSLBF allows one to check for CP violation in the neutral Higgs sector; such CP violation is predicted to be absent in the MSSM. (Full postscript file available upon request. Macropackage phyzzx.tex required. To appear in Proceedings of 23rd INFN Eloisatron Workshop.)
We demonstrate that the ability to polarize the photons produced by back-scattering laser beams at a TeV scale linear $\epem$ collider could make it possible to determine whether or not a neutral Higgs boson produced in photon-photon collisions is a CP eigenstate. The relative utility of different types of polarization is discussed. Asymmetries that are only non-zero if the Higgs boson is a CP mixture are defined, and their magnitudes illustrated for a two-doublet Higgs model with CP-violating neutral sector.