4,095 research outputs found
Mass bounds for baryogenesis from particle decays and the inert doublet model
In models for thermal baryogenesis from particle decays, the mass of the
decaying particle is typically many orders of magnitude above the TeV scale. We
will discuss different ways to lower the energy scale of baryogenesis and
present the corresponding lower bounds on the particle's mass. This is done
specifically for the inert doublet model with heavy Majorana neutrinos and then
we indicate how to extrapolate the results to other scenarios. We also revisit
the question of whether or not dark matter, neutrino masses, and the cosmic
baryon asymmetry can be explained simultaneously at low energies in the inert
doublet model.Comment: 25 pages - 5 figures - typos corrected and references added -
accepted for publication in JCA
On different approaches to freeze-in and freeze-out leptogenesis with quasi-degenerate neutrinos
We compare two approaches for determining the generation of lepton asymmetry
during production and decay of quasi-degenerate neutrinos, namely the density
matrix formalism and a recent proposal which does not involve any counting of
neutrino number densities and is based on plugging the resummed propagator in a
quantum field theory model for neutrino oscillations. We show numerically and
analytically that they are almost equivalent except in the limit of very large
mass splittings. The comparison, performed in a simple scalar toy model, helps
to understand several issues that have been discussed in the literature.Comment: 14 pages, 1 figur
Washout processes in post-sphaleron baryogenesis from way-out-of-equilibrium decays
We study washout processes in post-sphaleron baryogenesis, a mechanism where
the matter-antimatter asymmetry is generated in the decay of exotic particles
after the electroweak phase transition. In particular we focus, in a quite
model independent way, on those scattering processes that have an amplitude
proportional to the CP asymmetry. We find that when the scatterings involve
only massless particles, the washouts are very severe for light decaying
particles (with masses below a few hundred of GeV) and successful baryogenesis
is only possible in a small portion of parameter space. Instead, if even a very
light particle participates in these processes, the allowed region of parameter
space opens considerably, although the final amount of baryon asymmetry may
differ significantly from the expression which is typically used and neglects
washouts. Furthermore, we analyze washouts from the non-thermal spectrum of
energetic particles produced in cascade decays and indicate in which models
they can be relevant.Comment: 10 pages, 3 figure
Review of Pike\u27s Peak Vision: The Broadmoor Art Academy , 1919-1945
Pike\u27s Peak Vision: The Broadmoor Art Academy, 1919-1945 is a catalog for a 1989/90 exhibition organized by the Colorado Springs Fine Arts Center. Co-curators and authors Stanley L. Cuba and Elizabeth Cunningham state that the exhibition was the first survey of the collections of the Broadmoor Art Academy and its successor, the Colorado Springs Fine Arts Center
Review of Pike\u27s Peak Vision: The Broadmoor Art Academy , 1919-1945
Pike\u27s Peak Vision: The Broadmoor Art Academy, 1919-1945 is a catalog for a 1989/90 exhibition organized by the Colorado Springs Fine Arts Center. Co-curators and authors Stanley L. Cuba and Elizabeth Cunningham state that the exhibition was the first survey of the collections of the Broadmoor Art Academy and its successor, the Colorado Springs Fine Arts Center
CP violation in mixing and oscillations for leptogenesis: Part II. The highly degenerate case
We extend to the highly degenerate case a recent approach for analyzing the sources of CP violation in baryogenesis models with quasi-degenerate neutrinos. In this approach an expansion of the resummed propagator around the poles is plugged into a quantum field theory model of neutrino oscillations and a source term for the time evolution of the lepton asymmetry is built directly from the probabilities of lepton number violating processes involving only stable particles. This allows for a transparent consideration of unitarity requirements. The source term has contributions that can be identified with CP violation from mixing, oscillations and interference between both. For the highly degenerate case, i.e. when the mass difference between two neutrinos is similar or smaller than their decay widths, we find that in general the mixing and oscillation terms contribute with opposite signs to the generation of lepton asymmetry and the contribution of the interference term is typically very relevant and crucial to ensure unitarity is satisfied. Moreover, the expressions we obtain are finite in the double degenerate limit of equal masses and couplings. The calculations are done in a simple scalar toy model.Fil: Racker, Juan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentin
On baryogenesis from dark matter annihilation
We study in detail the conditions to generate the baryon asymmetry of the
universe from the annihilation of dark matter. This scenario requires a low
energy mechanism for thermal baryogenesis, hence we first discuss some of these
mechanisms together with the specific constraints due to the connection with
the dark matter sector. Then we show that, contrary to what stated in previous
studies, it is possible to generate the cosmological asymmetry without adding a
light sterile dark sector, both in models with violation and with conservation
of B-L. In addition, one of the models we propose yields some connection to
neutrino masses.Comment: 30 pages, 9 artistic figures. V2 minor changes, matches published
version in JCA
On Higgs and sphaleron effects during the leptogenesis era
We discuss the effects of various processes that can be active during the
leptogenesis era, and present the Boltzmann equations that take them into
account appropriately. A non-vanishing Higgs number asymmetry is always
present, enhancing the washout of the lepton asymmetry. This is the main new
effect when leptogenesis takes place at GeV, reducing the final
baryon asymmetry and tightening the leptogenesis bound on the neutrino masses.
If leptogenesis occurs at lower temperatures, electroweak sphalerons partially
transfer the lepton asymmetry to a baryonic one, while Yukawa interactions and
QCD sphalerons partially transfer the asymmetries of the left-handed fields to
the right-handed ones, suppressing the washout processes. Depending on the
specific temperature range in which leptogenesis occurs, the final baryon
asymmetry can be enhanced or suppressed by factors of order 20%--40% with
respect to the case when these effects are altogether ignored.Comment: one reference adde
- …