164 research outputs found
<Research Report> Mapping the housing types from LIDAR data for micro-scale spatial analysis : A case of Tsukuba City
Supersymmetric Grand Unification and Lepton Universality in K-> l \nu Decays
Motivated by the prospects for an improved test of lepton universality in K
-> l \nu decays by the NA62 experiment at CERN, we study predictions for the
possible lepton non-universality in K -> l \nu decays in supersymmetric models.
Violations of \mu-e universality in this process may originate from mixing
effects in the right-handed slepton sector, providing a unique window into this
aspect of supersymmetric flavour physics in the large-\tan\beta region. Minimal
unification scenarios with universal soft supersymmetry-breaking terms at the
GUT scale would predict negligible violation of lepton universality. However,
lepton non-universality may be observable in non-minimal grand unified models
with higher-dimensional terms contributing to fermion masses, in which case
renormalization effects above the GUT scale may enhance the mixing among the
right-handed sleptons. This could leads to observable lepton non-universality
in K -> l \nu decays in specific regions of the parameter space with high \tan
\beta, large A terms and small charged Higgs boson mass. Observable
non-universality in K -> l \nu decays would be correlated with a large value of
BR(\tau -> e \gamma). The experimental upper limit on the electric dipole
moment of the electron could be reconciled with leptogenesis, if the latter
occurs at a relatively low scale, which would also alleviate the cosmological
gravitino problem. Even if lepton non-universality is not seen in the near
future, one may nevertheless obtain significant constraints on the model
parameters and unknown aspects of right-handed fermion and sfermion mixing.Comment: 19 pages, 3 figure
MSSM Higgs sector CP violation at photon colliders: Revisited
We present a comprehensive analysis on the MSSM Higgs sector CP violation at
photon colliders including the chargino contributions as well as the
contributions of other charged particles. The chargino loop contributions can
be important for the would-be CP odd Higgs production at photon colliders.
Polarization asymmetries are indispensable in determining the CP properties of
neutral Higgs bosons.Comment: 24 pages, 40 figure
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
Searching for realistic 4d string models with a Pati-Salam symmetry -- Orbifold grand unified theories from heterotic string compactification on a Z6 orbifold
Motivated by orbifold grand unified theories, we construct a class of
three-family Pati-Salam models in a Z6 abelian symmetric orbifold with two
discrete Wilson lines. These models have marked differences from
previously-constructed three-family models in prime-order orbifolds. In the
limit where one of the six compactified dimensions (which lies in a Z2
sub-orbifold) is large compared to the string length scale, our models
reproduce the supersymmetry and gauge symmetry breaking pattern of 5d orbifold
grand unified theories on an S1/Z2 orbicircle. We find a horizontal 2+1
splitting in the chiral matter spectra -- 2 families of matter are localized on
the Z2 orbifold fixed points, and 1 family propagates in the 5d bulk -- and
identify them as the first-two and third families. Remarkably, the first two
families enjoy a non-abelian dihedral D4 family symmetry, due to the geometric
setup of the compactified space. In all our models there are always some color
triplets, i.e. (6,1,1) representations of the Pati-Salam group, survive
orbifold projections. They could be utilized to spontaneously break the
Pati-Salam symmetry to that of the Standard Model. One model, with a 5d E6
symmetry, may give rise to interesting low energy phenomenology. We study gauge
coupling unification, allowed Yukawa couplings and some of their
phenomenological consequences. The E6 model has a renormalizable Yukawa
coupling only for the third family. It predicts a gauge-Yukawa unification
relation at the 5d compactification scale, and is capable of generating
reasonable quark/lepton masses and mixings. Potential problems are also
addressed, they may point to the direction for refining our models.Comment: 58 pages, 5 figures, 4 tables, revtex4 with ams fonts. Version to
appear in NP
Study of non-minimal SUSY SU(5) model with realistic fermion sectors
We study a supersymmetric SU(5) model with the extra Higgs multiplets of
45+\bar 45. The unification of the gauge couplings, the fermion masses and the
proton lifetime are discussed in details. The dimension-five operators mediated
by different colored Higgs sector can be destructive with each other. This
effect serves a way of solving the longevity of proton. We analytically analyze
this destructive effect in a special limit where the mixing between the 5- and
45-plets is small. Although the theory does not hold in this special limit, it
is a revelatory starting point. We can relax this limit and retain the
destructive effect. In a generalized parameter space, this model is in accord
with experimental results
SUSY GUT Model Building
I discuss an evolution of SUSY GUT model building, starting with the
construction of 4d GUTs, to orbifold GUTs and finally to orbifold GUTs within
the heterotic string. This evolution is an attempt to obtain realistic string
models, perhaps relevant for the LHC. This review is in memory of the sudden
loss of Julius Wess, a leader in the field, who will be sorely missed.Comment: 24 pages, 14 figures, lectures given at PiTP 2008, Institute for
Advanced Study, Princeton, to be published in the European Physical Journal
Presenilin/γ-Secretase Regulates Neurexin Processing at Synapses
Neurexins are a large family of neuronal plasma membrane proteins, which function as trans-synaptic receptors during synaptic differentiation. The binding of presynaptic neurexins to postsynaptic partners, such as neuroligins, has been proposed to participate in a signaling pathway that regulates synapse formation/stabilization. The identification of mutations in neurexin genes associated with autism and mental retardation suggests that dysfunction of neurexins may underlie synaptic defects associated with brain disorders. However, the mechanisms that regulate neurexin function at synapses are still unclear. Here, we show that neurexins are proteolytically processed by presenilins (PS), the catalytic components of the γ-secretase complex that mediates the intramembraneous cleavage of several type I membrane proteins. Inhibition of PS/γ-secretase by using pharmacological and genetic approaches induces a drastic accumulation of neurexin C-terminal fragments (CTFs) in cultured rat hippocampal neurons and mouse brain. Neurexin-CTFs accumulate mainly at the presynaptic terminals of PS conditional double knockout (PS cDKO) mice lacking both PS genes in glutamatergic neurons of the forebrain. The fact that loss of PS function enhances neurexin accumulation at glutamatergic terminals mediated by neuroligin-1 suggests that PS regulate the processing of neurexins at glutamatergic synapses. Interestingly, presenilin 1 (PS1) is recruited to glutamatergic terminals mediated by neuroligin-1, thus concentrating PS1 at terminals containing β-neurexins. Furthermore, familial Alzheimer's disease (FAD)-linked PS1 mutations differentially affect β-neurexin-1 processing. Expression of PS1 M146L and PS1 H163R mutants in PS−/− cells rescues the processing of β-neurexin-1, whereas PS1 C410Y and PS1 ΔE9 fail to rescue the processing defect. These results suggest that PS regulate the synaptic function and processing of neurexins at glutamatergic synapses, and that impaired neurexin processing by PS may play a role in FAD
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