93 research outputs found
Nambu-Goldstone Dark Matter and Cosmic Ray Electron and Positron Excess
We propose a model of dark matter identified with a pseudo-Nambu-Goldstone
boson in the dynamical supersymmetry breaking sector in a gauge mediation
scenario. The dark matter particles annihilate via a below-threshold narrow
resonance into a pair of R-axions each of which subsequently decays into a pair
of light leptons. The Breit-Wigner enhancement explains the excess electron and
positron fluxes reported in the recent cosmic ray experiments PAMELA, ATIC and
PPB-BETS without postulating an overdensity in halo, and the limit on
anti-proton flux from PAMELA is naturally evaded.Comment: 3 figure
Leptogenesis from -dominated early universe
We investigate in detail the leptogenesis by the decay of coherent
right-handed sneutrino having dominated the energy density of
the early universe, which was originally proposed by HM and TY. Once the
dominant universe is realized, the amount of the generated
lepton asymmetry (and hence baryon asymmetry) is determined only by the
properties of the right-handed neutrino, regardless of the history before it
dominates the universe. Moreover, thanks to the entropy production by the decay
of the right-handed sneutrino, thermally produced relics are sufficiently
diluted. In particular, the cosmological gravitino problem can be avoided even
when the reheating temperature of the inflation is higher than 10^{10}\GeV,
in a wide range of the gravitino mass m_{3/2}\simeq 10\MeV--100\TeV. If the
gravitino mass is in the range m_{3/2}\simeq 10\MeV--1\GeV as in the some
gauge-mediated supersymmetry breaking models, the dark matter in our universe
can be dominantly composed of the gravitino. Quantum fluctuation of the
during inflation causes an isocurvature fluctuation which may
be detectable in the future.Comment: 16 page
Flipping SU(5) Towards Five Dimensional Unification
It is shown that embedding of flipped SU(5) in a five-dimensional SO(10)
enables exact unification of the gauge coupling constants. The demand for the
unification uniquely determines both the compactification scale and the cutoff
scale. These are found to be 5.5 \times 10^{14} GeV and 1.0 \times 10^{17} GeV
respectively. The theory explains the absence of d=5 proton-decay operators
through the implementation of the missing partner mechanism. On the other hand,
the presence of d=6 proton-decay operators points towards the bulk localization
of the first and the second family of matter fields.Comment: 21 pages, references added, 3 Postscript figures, ReVTeX
Proton Decay in Supersymmetric GUT Models
The instability of protons is a crucial prediction of supersymmetric GUTs. We
review the decay in minimal supersymmetric SU(5), which is dominated by
dimension-five operators, and discuss the implications of the failure of Yukawa
unification for the decay rate. In a consistent SU(5) model, where SU(5)
relations among Yukawa couplings hold, the proton decay rate can be several
orders of magnitude smaller than the present experimental bound. Finally, we
discuss orbifold GUTs, where proton decay via dimension-five operators is
absent. The branching ratios of dimension-six decay can significantly differ
from those in four dimensions.Comment: DESY report number correcte
Long-lived neutral-kaon flux measurement for the KOTO experiment
The KOTO ( at Tokai) experiment aims to observe the CP-violating rare
decay by using a long-lived neutral-kaon
beam produced by the 30 GeV proton beam at the Japan Proton Accelerator
Research Complex. The flux is an essential parameter for the measurement
of the branching fraction. Three neutral decay modes, , , and were used to
measure the flux in the beam line in the 2013 KOTO engineering run. A
Monte Carlo simulation was used to estimate the detector acceptance for these
decays. Agreement was found between the simulation model and the experimental
data, and the remaining systematic uncertainty was estimated at the 1.4\%
level. The flux was measured as per protons on a
66-mm-long Au target.Comment: 27 pages, 16 figures. To be appeared in Progress of Theoretical and
Experimental Physic
On the Relationship Between Complex Potentials and Strings of Projection Operators
It is of interest in a variety of contexts, and in particular in the arrival
time problem, to consider the quantum state obtained through unitary evolution
of an initial state regularly interspersed with periodic projections onto the
positive -axis (pulsed measurements). Echanobe, del Campo and Muga have
given a compelling but heuristic argument that the state thus obtained is
approximately equivalent to the state obtained by evolving in the presence of a
certain complex potential of step-function form. In this paper, with the help
of the path decomposition expansion of the associated propagators, we give a
detailed derivation of this approximate equivalence. The propagator for the
complex potential is known so the bulk of the derivation consists of an
approximate evaluation of the propagator for the free particle interspersed
with periodic position projections. This approximate equivalence may be used to
show that to produce significant reflection, the projections must act at time
spacing less than 1/E, where E is the energy scale of the initial state.Comment: 29 pages, LaTex, 4 figures. Substantial revision
A Complete Theory of Grand Unification in Five Dimensions
A fully realistic unified theory is constructed, with SU(5) gauge symmetry
and supersymmetry both broken by boundary conditions in a fifth dimension.
Despite the local explicit breaking of SU(5) at a boundary of the dimension,
the large size of the extra dimension allows precise predictions for gauge
coupling unification, alpha_s(M_Z) = 0.118 \pm 0.003, and for Yukawa coupling
unification, m_b(M_Z) = 3.3 \pm 0.2 GeV. A complete understanding of the MSSM
Higgs sector is given; with explanations for why the Higgs triplets are heavy,
why the Higgs doublets are protected from a large tree-level mass, and why the
mu and B parameters are naturally generated to be of order the SUSY breaking
scale. All sources of d=4,5 proton decay are forbidden, while a new origin for
d=6 proton decay is found to be important. Several aspects of flavor follow
from an essentially unique choice of matter location in the fifth dimension:
only the third generation has an SU(5) mass relation, and the lighter two
generations have small mixings with the heaviest generation. The entire
superpartner spectrum is predicted in terms of only two free parameters. The
squark and slepton masses are determined by their location in the fifth
dimension, allowing a significant experimental test of the detailed structure
of the extra dimension. Lepton flavor violation is found to be generically
large in higher dimensional unified theories with high mediation scales of SUSY
breaking. In our theory this forces a common location for all three neutrinos,
predicting large neutrino mixing angles. Rates for mu -> e gamma, mu -> e e e,
mu -> e conversion and tau -> mu gamma are larger in our theory than in
conventional 4D supersymmetric GUTs. Proposed experiments probing mu -> e
transitions will probe the entire interesting parameter space of our theory.Comment: 51 pages, late
Cosmological Moduli Problem in Gauge-mediated Supersymmetry Breaking Theories
A generic class of string theories predicts the existence of light moduli
fields, and they are expected to have masses comparable to the
gravitino mass which is in a range of keV--1GeV in
gauge-mediated supersymmetry breaking theories. Such light fields with weak
interactions suppressed by the Planck scale can not avoid some stringent
cosmological constraints, that is, they suffer from `cosmological moduli
problems'. We show that all the gravitino mass region keV 1GeV is excluded by the constraints even if we incorporate a
late-time mini-inflation (thermal inflation). However, a modification of the
original thermal inflation model enables the region keV 500keV to survive the constraints. It is also stressed that
the moduli can be dark matter in our universe for the mass region keV
100keV.Comment: A few changes in section IV and
Why is TeV-scale a geometric mean of neutrino mass and GUT-scale?
Among three typical energy scales, a neutrino mass scale ( 0.1
eV), a GUT scale ( GeV), and a TeV-scale (
TeV), there is a fascinating relation of . The TeV-scale, , is a new physics scale beyond the standard
model which is regarded as supersymmetry in this letter. We suggest a simple
supersymmetric neutrinophilic Higgs doublet model, which realizes the above
relation dynamically as well as the suitable through a tiny vacuum
expectation value of neutrinophilic Higgs without additional scales other than
and . A gauge coupling unification, which is an excellent
feature in the supersymmetric standard model, is preserved automatically in
this setup.Comment: 7 page
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