Article

# Search for a new weakly interacting particle

Fachbereich Physik, Universität Siegen, W-5900 Siegen, FRG

Physics Letters B 06/1991; 262(1):139-147. DOI: 10.1016/0370-2693(91)90657-C Get notified about updates to this publication Follow publication |

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**ABSTRACT:**The electroweak vacuum need not be absolutely stable. For certain top-quark and Higgs-boson masses in the minimal standard model, it is instead metastable with a lifetime exceeding the present age of the Universe. The decay of our vacuum may be nucleated at low temperature by quantum tunneling or at high temperature by thermal excitation. We show that the requirement that the vacuum survive the high temperatures of the early Universe places the strongest constraints from vacuum stability on the top-quark and Higgs-boson masses in the minimal standard model. If a single Higgs boson is found experimentally, these constraints may place an upper bound on the scale of new physics beyond the minimal standard model. In contrast with other work, we examine temperatures very large compared to the scale of weak symmetry restoration and find much stronger bounds. We also present a simple analytic approximation that directly relates the bounds to the running coupling constants of the minimal standard model. - [Show abstract] [Hide abstract]

**ABSTRACT:**We study the possibility that CP is spontaneously broken in the minimal supersymmetric model when radiative corrections to the Higgs potential are included. We show that this can only occur if a light Higgs boson exists. Considering the recent ALEPH Higgs search, we exclude most of the parameter space of the model. The possibility of explicit CP violation in the model is also briefly discussed. -
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