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
Violent Preheating in Inflation with Nonminimal Coupling
We study particle production at the preheating era in inflation models with
nonminimal coupling and quartic potential for
several cases: real scalar inflaton, complex scalar inflaton and Abelian Higgs
inflaton. We point out that the preheating proceeds much more violently than
previously thought. If the inflaton is a complex scalar, the phase degree of
freedom is violently produced at the first stage of preheating. If the inflaton
is a Higgs field, the longitudinal gauge boson production is similarly violent.
This is caused by a spike-like feature in the time dependence of the inflaton
field, which may be understood as a consequence of the short time scale during
which the effective potential or kinetic term changes suddenly. The produced
particles typically have very high momenta . The production might be so strong that almost all
the energy of the inflaton is carried away within one oscillation for
. This may partly change the
conventional understandings of the (p)reheating after inflation with the
nonminimal coupling to gravity such as Higgs inflation. We also discuss the
possibility of unitarity violation at the preheating stage.Comment: 43 pages, 15 figure
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