96 research outputs found
Early Decay of Peccei-Quinn Fermion and the IceCube Neutrino Events
IceCube observed high-energy neutrino flux in the energy region from TeV to
PeV. The decay of a massive long-lived particle in the early universe can be
the origin of the IceCube neutrino events, which we call an "early decay
scenario." In this paper, we construct a particle physics model that contains
such a massive long-lived particle based on the Peccei-Quinn model. We
calculate the present neutrino flux, taking account of realistic initial energy
distributions of particles produced by the decay of the massive long-lived
particle. We show that the early decay scenario naturally fits into the
Peccei-Quinn model, and that the neutrino flux observed by IceCube can be
explained in such a framework. We also see that, based on that model, a
consistent cosmological history that explains the abundance of the massive
long-lived particle is realized.Comment: 20 pages, 2 figures; v2: references added; v3: version accepted for
publication in PL
Explosive Axion Production from Saxion
The dynamics of saxion in a supersymmetric axion model and its effect on the
axion production is studied in detail. We find that the axion production is
very efficient when the saxion oscillation amplitude is much larger than the
Peccei-Quinn scale, due to a spike-like behavior of the effective axion mass.
We also consider the axino production and several cosmological consequences.
The possibility of detection of gravitational waves from the non-linear
dynamics of the saxion and axion is discussed.Comment: 17 pages, 3 figure
Unitarity constraint on the K\"ahler curvature
In supersymmetric theories, the signs of quartic terms in the K\"ahler
potential control the stability of non-supersymmetric field configurations. In
particular, in supersymmetric inflation models, the signs are important for the
stability of an inflationary trajectory as well as for the prediction of the
spectral index. In this paper, we clarify what properties of a UV theory
determine the sign from unitarity arguments of scattering amplitudes. As
non-trivial examples, we discuss the sign of a four-meson term in large
supersymmetric gauge theories and also those of the quartic terms obtained in
the intersecting D-brane models in superstring theory. The UV origins of
inflationary models and supersymmetry breaking models are constrained by this
discussion.Comment: 20 pages, 2 figures; published version, minor changes, references
adde
Electroweak Vacuum Stabilized by Moduli during/after Inflation
It is known that the present electroweak vacuum is likely to be metastable
and it may lead to a serious instability during/after inflation. We propose a
simple solution to the problem of vacuum instability during/after inflation. If
there is a moduli field which has Planck-suppressed interactions with the
standard model fields, the Higgs quartic coupling in the early universe
naturally takes a different value from the present one. A slight change of the
quartic coupling in the early universe makes the Higgs potential absolutely
stable and hence we are free from the vacuum instability during/after
inflation.Comment: 6 pages, 2 figures; v2: references adde
Indirect Studies of Electroweakly Interacting Particles at 100 TeV Hadron Colliders
There are many extensions of the standard model that predict the existence of
electroweakly interacting massive particles (EWIMPs), in particular in the
context of the dark matter. In this paper, we provide a way for indirectly
studying EWIMPs through the precise study of the pair production processes of
charged leptons or that of a charged lepton and a neutrino at future 100 TeV
collider experiments. It is revealed that this search method is suitable in
particular for Higgsino, providing us the discovery reach of Higgsino
in supersymmetric model with mass up to 850 GeV. We also discuss how accurately
one can extract the mass, gauge charge, and spin of EWIMPs in our method.Comment: 20 pages, 7 figures, 5 table
Chiral Anomaly and Schwinger Effect in Non-Abelian Gauge Theories
We study the production of chiral fermions in a background of a strong
non-abelian gauge field with a non-vanishing Chern-Pontryagin density. We
discuss both pair production analogous to the Schwinger effect as well as
asymmetric production through the chiral anomaly, sourced by the
Chern-Pontryagin density. In abelian gauge theories one may nicely understand
these processes by considering that the fermion dispersion relation forms
discrete Landau levels. Here we extend this analysis to a non-abelian gauge
theory, considering an intrinsically non-abelian isotropic and homogeneous
SU(2) gauge field background with a non-vanishing Chern-Pontryagin density. We
show that the asymmetric fermion production, together with a non-trivial vacuum
contribution, correctly reproduces the chiral anomaly. This indicates that the
usual vacuum subtraction scheme, imposing normal ordering, fails in this case.
As a concrete example of this gauge field background, we consider
chromo-natural inflation. Applying our analysis to this particular model, we
compute the backreaction of the generated fermions on the gauge field
background. This backreaction receives contributions both from the vacuum
through a Coleman-Weinberg-type correction and from the fermion excitations
through an induced current.Comment: 27 pages + appendices, 2 figures; v2: published versio
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