16 research outputs found
Spontaneous CP Violation in the Minimal Supersymmetric Standard Model at Finite Temperature
We show that in the Minimal Supersymmetric Standard Model one--loop effects
at finite temperature may lead to a spontaneous breaking of CP invariance in
the scalar sector. Requiring that the breaking takes place at the critical
temperature for the electroweak phase transition, we find that the parameters
space is compatible with a mass of the Higgs pseudoscalar in agreement with the
present experimental lower bounds. Possible implications for baryogenesis are
discussed.Comment: 13 pages, DFPD 93/TH/06 and UTS/DFT/93/
A realistic heat bath: theory and application to kink-antikink dynamics
We propose a new method of studying a real-time canonical evolution of
field-theoretic systems with boundary coupling to a realistic heat bath. In the
free-field case the method is equivalent to an infinite extension of the system
beyond the boundary, while in the interacting case the extension of the system
is done in linear approximation. We use this technique to study kink-antikink
dynamics in field theory in 1+1 dimensions.Comment: 21 pages including 7 figures (the shar file includes the tex file + 7
postscript files for figures). IUHET-241, IPS-92-29, UALG-PHYS-1
Baryogenesis, Domain Walls and the Role of Gravity
It has been recently speculated that global symmetries are broken by gravity.
We propose a scenario for the generation of the baryon asymmetry in the early
Universe in which the domain walls predicted by theories with discrete
symmetries become unstable due to these Planck scale effects. The relative
motion of the decaying walls can provide a mechanism for the departure from
thermal equilibrium necessary to have a nonvanishing baryon asymmetry. In
particular, we implement this idea within the frameworks of the Left-Right and
Quark-Lepton symmetric models.Comment: 15 pages (LaTeX), PURD-TH-93-06, SISSA-/93/49-
Model Independent Higgs Boson Mass Limits at LEP
We derive model-independent constraints on Higgs mass and couplings from
associated signals for higher masses, accessible at LEP2. This work is
motivated by the fact that, in many extensions of the standard model, the Higgs
boson can have substantial "invisible" decay modes, for example, into light or
massless weakly interacting Goldstone bosons associated to the spontaneous
violation of lepton number below the weak scale.Comment: FTUV/93-19, 13 pag + 2 figures(not included but available upon
request), Late
On the Spontaneous CP Breaking at Finite Temperature in a Nonminimal Supersymmetric Standard Model
We study the spontaneous CP breaking at finite temperature in the Higgs
sector in the Minimal Supersymmetric Standard Model with a gauge singlet. We
consider the contribution of the standard model particles and that of stops,
charginos, neutralinos, charged and neutral Higgs boson to the one-loop
effective potential. Plasma effects for all bosons are also included. Assuming
CP conservation at zero temperature, so that experimental constraints coming
from, {\it e.g.}, the electric dipole moment of the neutron are avoided, and
the electroweak phase transition to be of the first order and proceeding via
bubble nucleation, we show that spontaneous CP breaking cannot occur inside the
bubble mainly due to large effects coming from the Higgs sector. However,
spontaneous CP breaking can be present in the region of interest for the
generation of the baryon asymmetry, namely inside the bubble wall. The
important presence of very tiny explicit CP violating phases is also commented.Comment: 28 pages, 4 figures available upon request, DFPD 94/TH/38 and SISSA
94/81-A preprint
Searching for an Invisibly Decaying Higgs Boson in E^+E^-, E-Gamma, and Gamma-Gamma Collisions
Higgs bosons can have a substantial ``invisible'' branching ratio in many
extensions of the Standard Model, such as models where the Higgs bosons decay
predominantly into light or massless weakly interacting Goldstone bosons. In
this work, we examine the production mechanisms and backgrounds for invisibly
decaying Higgs bosons at the Next Linear Collider operating in the
modes , , and . We demonstrate that such machine
is much more efficient to survey for invisibly decaying Higgs bosons than the
Large Hadron Collider at CERN.Comment: (LaTex file, 9 figures in postcript available upon request.
MAD/PH/81
Reconciling dark matter, solar and atmospheric neutrinos
We present models that can reconcile the solar and atmospheric neutrino data with the existence of a hot dark matter component in the universe. This dark matter is a quasi-Dirac neutrino whose mass mDM arises at the one-loop level. The solar neutrino deficit is explained via nonadiabatic conversions of electron neutrino to a sterile neutrino and the atmospheric neutrino data via maximal muon neutrino to tau neutrino oscillations generated by higher order loop diagrams. For mDM∼30 eV the radiative neutrino decay can lead to photons that can ionize interstellar hydrogen. In one of the models one can have observable νe to ντ oscillation rates, with no appreciable muon neutrino oscillations at accelerator experiments. In addition, there can be observable rates for tau number violating processes such as τ→3e and τ→e+γ. In the other model one can have sizeable νe to νμ oscillation rates, as well as sizeable rates for muon number violating processes such as μ→e+γ, μ→e+majoron and μ→3e
Low Temperature Dominance of Pion-like Excitations in the Massive Gross-Neveu Model at Order 1/N
We perform a 1/N-expansion of the partition function of the massive
Gross-Neveu model in 1+1 dimensions. The procedure allows for the inclusion of
the contribution of scalar and pseudoscalar composites (of order 1/N) to the
equation of state. The naive expectation that the bosonic fluctuations correct
significantly the mean field approximation at low temperatures is confirmed by
our calculations. Actually the relevant degrees of freedom of hadronic matter
at low temperatures are found to be pion-like excitations, rather than the
fundamental constituents.Comment: LaTex, 19 pages + 3 figure.p
Massive neutrinos and electroweak baryogenesis
We show that certain models for neutrino masses that lead to the MSW
explanation of the solar neutrino data and/or the hot dark matter component in
the universe can also naturally allow for the successful generation of the
cosmological baryon asymmetry at the electroweak scale. This follows either
because the experimental Higgs boson mass limit is weakened due to the smaller
production rate and the presence of sizeable invisible decays involving majoron
emission, or due to the effect of additional electrically charged scalar bosons
which substantially modify the condition for succesful baryogenesis.Comment: 10 pages, LaTeX, FTUV/92-60 and IFIC/92-6