arXiv subjects

Thomas J. Weiler

Publications and source records attributed to Thomas J. Weiler.

95 records · Page 6Linked to original sources

arXiv1994

The Higgs Mass as the Discriminator of Electroweak Models

In the Minimal Supersymmetric Model (MSSM) and the Next to Minimal Supersymmetric Model [(M+1)SSM], an upper bound on the lightest higgs mass can be calculated. On the other hand, vacuum stability implies a lower limit on the mass of the higgs boson in the Standard Model (SM). We find that a gap exists for $m_t \stackrel{>}{\sim} 165$ GeV between the SM and both the MSSM and the (M+1)SSM bounds. Thus, if the new top quark mass measurement by CDF remains valid, a first measurement of the higgs mass will serve to exclude either the SM or the MSSM/(M+1)SSM higgs sectors. In addition, we discuss Supersymmetric Grand Unified Theories, other extentions of the SM, the discovery potential of the lightest higgs, and the assumptions on which our conclusions are based.

hep-ph↗

arXiv1994

Higgs Mass Bounds Separate Models of Electroweak Symmetry Breaking

Vacuum stability implies a lower limit on the mass of the higgs boson in the Standard Model (SM). In contrast, an upper limit on the lightest higgs mass can be calculated in supersymmetric (susy) models. The main uncertainty in each limit is the value of the top mass, which may now be fixed by the recent CDF result. We study the possibility that these bounds do not overlap, and find that (i) a mass gap emerges at $m_t\sim 160$ GeV between the SM and the Minimal Susy Standard Model (MSSM); and between the SM and the Minimal plus Singlet Susy Model [(M+1)SSM] if the independent scalar self--coupling of the latter is perturbatively small or if the $\tanβ$ parameter is large; this gap widens with increasing $m_t$; (ii) there is no overlap between the SM and the MSSM bounds at even smaller values of $m_t$ for the $\tanβ$ value ($\sim 1$--2) preferred in Supersymmetric Grand Unified Theories. Thus, if the new top mass measurement remains valid, a measurement of the first higgs mass will serve to exclude either the SM or MSSM/(M+1)SSM higgs sectors. In addition, we discuss the upper bound on the lightest higgs mass in susy models with an extended higgs sector, and in models with a strongly interacting higgs sector. Finally, we comment on the discovery potential for the lightest higgses in these models.

hep-ph↗

arXiv1994

Decays of a fermiophobic Higgs

We explore the phenomenology of a fermiophobic Higgs: a Higgs whose couplings to fermions are suppressed. We calculate the branching ratios of a Higgs decaying to $γγ$, $W^*W^*$, $Z^*Z^*$, $Zb\bar b$, $Zγ$, $γb\bar b$, and final states involving vector mesons like $Υ$, $J/Ψ$ and $ρ$. In order to calculate these branching ratios we perform a complete one-loop renormalization of the vertices $HZγ$ and $Hγγ$. The decay mode $H\rightarrow γγ$ is near unity for a Higgs below the $W$ mass, which provides a clean way of discovering a light fermiophobic Higgs. Interesting modes involving the vector mesons $Z$, $γ$, $ρ$, $J/Ψ$, and $Υ$ are carefully analyzed.

hep-ph↗

arXiv1993

Measuring Charm and Bottom Quark Masses

The meaning and the extraction of heavy quark masses are discussed. A simple production model is presented which incorporates the running of the heavy quark mass into perturbative calculations. The model offers the possibilities of (i) understanding the differing charmed mass values extracted from different experiments, (ii) determining the short--distance mass relevent to quark mass matrix and mixing angle studies, and (iii) determining the long--distance charm mass, which determines the charm quark threshold and sensitively affects the extraction of $\sin^2θ_w $. Threshold and forward angle production offer the best possibilities to test the model and extract meaningful charm/bottom masses.

hep-ph↗

arXiv1993

Higgs-Boson Decay to Four Fermions Including a Single Top Quark Below $t \bar t$ Threshold

The rare decay modes Higgs $\rightarrow$ four light fermions, and Higgs $\rightarrow$ single top-quark + three light fermions for $m_t 100\GeV$ makes the second amplitude competitive or dominant for most $M_H,m_t$ values. Thus the Higgs decay rate to single top directly probes the SM universal mechanism generating both gauge boson and fermion masses, and offers a means to infer the Higgs-$t \bar t$ Yukawa coupling when $H\rightarrow t \bar t$ is kinematically disallowed. We find that the modes $pp\rightarrow Xt\bar t(H\rightarrow t\bar b W^{(*)})$ at the SSC, and $e^+ e^-\rightarrow Z\,or\,ν\barν + (H\rightarrow t\bar b W^{(*)})$ at future high energy, high luminosity colliders, may be measureable if $2m_t$ is not too far above $M_H$. We classify non-standard Higgses as gaugeo-phobic, fermio-phobic or fermio-philic, and discuss the Higgs$\rightarrow$ single top rates for these classes.

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