995 research outputs found
The light Higgs in supersymmetric models with Higgs triplets
In supersymmetric models the presence of Higgs triplets introduce new quartic
interactions for the doublets that may raise the mass of the lightest CP-even
field up to 205 GeV. We show that the complete effect of the triplets can be
understood by decoupling them from the minimal sector and then analyzing the
vacuum and the spectrum of the two-Higgs doublet model that results. We find
that the maximum value of m_h is only achieved in a very definite region of the
parameter space. In this region, however, radiative corrections decrease the
bound to 190 GeV.Comment: 10 pages, 1 figur
Black hole gas in the early universe
We consider the early universe at temperatures close to the fundamental scale
of gravity (M_D << M_Planck) in models with extra dimensions. At such
temperatures a small fraction of particles will experience transplanckian
collisions that may result in microscopic black holes (BHs). BHs colder than
the environment will gain mass, and as they grow their temperature drops
further. We study the dynamics of a system (a black hole gas) defined by
radiation at a given temperature coupled to a distribution of BHs of different
mass. Our analysis includes the production of BHs in photon-photon collisions,
BH evaporation, the absorption of radiation, collisions of two BHs to give a
larger one, and the effects of the expansion. We show that the system may
follow two different generic paths depending on the initial temperature of the
plasma.Comment: 17 pages, version to appear in JCA
Higgsino dark matter in partly supersymmetric models
Models where supersymmetry (SUSY) is manifest only in a sector of the
low-energy spectrum have been recently proposed as an alternative to the MSSM.
In these models the electroweak scale is explained by a fine-tuning between
different Higgs mass contributions (split-SUSY models), or by the localization
of the Higgs sector in a point of an extra dimension where all the mass
parameters are suppressed by the metric (partly-SUSY models). Therefore, the
presence of a good dark matter candidate becomes the main motivation for
(partial) low-energy SUSY. We study this issue in minimal frameworks where the
higgsinos are the only light supersymmetric particles. Whereas in split-SUSY
models the higgsino should have a mass around 1 TeV, we show that in
partly-SUSY models the lightest higgsino could also be found below MW.Comment: 12 pages, 3 figures, version to appear in Phys. Rev.
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