1,733 research outputs found
RG running in a minimal UED model in light of recent LHC Higgs mass bounds
We study how the recent ATLAS and CMS Higgs mass bounds affect the
renormalization group running of the physical parameters in universal extra
dimensions. Using the running of the Higgs self-coupling constant, we derive
bounds on the cutoff scale of the extra-dimensional theory itself. We show that
the running of physical parameters, such as the fermion masses and the CKM
mixing matrix, is significantly restricted by these bounds. In particular, we
find that the running of the gauge couplings cannot be sufficient to allow
gauge unification at the cutoff scale.Comment: 16 pages, 6 figures, RevTeX4. Final version published in Phys. Lett.
Exploring the singlet scalar dark matter from direct detections and neutrino signals via its annihilation in the Sun
We explore the singlet scalar dark matter (DM) from direct detections and
high energy neutrino signals generated by the solar DM annihilation. Two
singlet scalar DM models are discussed, one is the real singlet scalar DM model
as the simple extension of the standard model (SSDM-SM) with a discrete Z_2
symmetry, and another is the complex singlet scalar DM model as the simple
extension of the left-right symmetric two Higgs bidoublet model (SSDM-2HBDM)
with and CP symmetries. To derive the Sun capture rate, we consider the
uncertainties in the hadronic matrix elements and calculate the
spin-independent DM-nucleon elastic scattering cross section. We find that the
predicted neutrino induced upgoing muon fluxes in the region 3.7 GeV < m_D <
4.2 GeV slightly exceed the Super-Kamiokande limit in the SSDM-SM. However,
this exceeded region can be excluded by the current DM direct detection
experiments. For the SSDM-2HBDM, one may adjust the Yukawa couplings to avoid
the direct detection limits and enhance the predicted muon fluxes. For the
allowed parameter space of the SSDM-SM and SSDM-2HBDM, the produced muon fluxes
in the Super-Kamiokande and muon event rates in the IceCube are less than the
experiment upper bound and atmosphere background, respectively.Comment: 21 pages, 5 figures, 1 table. Accepted for publication in Nuclear
Physics
Rare B Decays with a HyperCP Particle of Spin One
In light of recent experimental information from the CLEO, BaBar, KTeV, and
Belle collaborations, we investigate some consequences of the possibility that
a light spin-one particle is responsible for the three Sigma^+ -> p mu^+ mu^-
events observed by the HyperCP experiment. In particular, allowing the new
particle to have both vector and axial-vector couplings to ordinary fermions,
we systematically study its contributions to various processes involving
b-flavored mesons, including B-Bbar mixing as well as leptonic, inclusive, and
exclusive B decays. Using the latest experimental data, we extract bounds on
its couplings and subsequently estimate upper limits for the branching ratios
of a number of B decays with the new particle. This can serve to guide
experimental searches for the particle in order to help confirm or refute its
existence.Comment: 17 pages, 3 figures; discussion on spin-0 case modified, few errors
corrected, main conclusions unchange
A Brief Review on Dark Matter Annihilation Explanation for Excesses in Cosmic Ray
Recently data from PAMELA, ATIC, FERMI-LAT and HESS show that there are
excesses in the cosmic ray energy spectrum. PAMELA observed excesses
only in , but not in anti-proton spectrum. ATIC, FERMI-LAT and HESS
observed excesses in spectrum, but the detailed shapes are different
which requires future experimental observations to pin down the correct data
set. Nevertheless a lot of efforts have been made to explain the observed
excesses, and also why PAMELA only observed excesses in but not
in anti-proton. In this brief review we discuss one of the most popular
mechanisms to explain the data, the dark matter annihilation. It has long been
known that about 23% of our universe is made of relic dark matter. If the relic
dark matter was thermally produced, the annihilation rate is constrained
resulting in the need of a large boost factor to explain the data. We will
discuss in detail how a large boost factor can be obtained by the Sommerfeld
and Briet-Wigner enhancement mechanisms. Some implications for particle physics
model buildings will also be discussed.Comment: 22 pages, 6 figures. Several typoes corrected and some references
added. Published in Mod. Phys. Lett. A, Vol. 24, No. 27 (2009) pp. 2139-216
Invisible Higgs and Scalar Dark Matter
In this proceeding, we show that when we combined WMAP and the most recent
results of XENON100, the invisible width of the Higgs to scalar dark matter is
negligible(<10%), except in a small region with very light dark matter (< 10
GeV) not yet excluded by XENON100 or around 60 GeV where the ratio can reach
50% to 60%. The new results released by the Higgs searches of ATLAS and CMS set
very strong limits on the elastic scattering cross section.Comment: 4 pages, 2 figures, proceeding TAUP2011 References adde
Astrophysical models for the origin of the positron "excess"
Over the last three years, several satellite and balloon observatories have
suggested intriguing features in the cosmic ray lepton spectra. Most notably,
the PAMELA satellite has suggested an "anomalous" rise with energy of the
cosmic ray positron fraction. In this article, we summarize the global picture
emerging from the data and recapitulate the main features of different types of
explanations proposed. The perspectives in testing different scenarios as well
as inferring some astrophysical diagnostics from current/near future
experiments are also discussed.Comment: 15 pages (150 references), 2 figures: review article for a Topical
Issue on Cosmic Rays, matches version appearing in Astroparticle Physic
Impaired perceptual learning in a mouse model of Fragile X syndrome is mediated by parvalbumin neuron dysfunction and is reversible.
To uncover the circuit-level alterations that underlie atypical sensory processing associated with autism, we adopted a symptom-to-circuit approach in the Fmr1-knockout (Fmr1-/-) mouse model of Fragile X syndrome. Using a go/no-go task and in vivo two-photon calcium imaging, we find that impaired visual discrimination in Fmr1-/- mice correlates with marked deficits in orientation tuning of principal neurons and with a decrease in the activity of parvalbumin interneurons in primary visual cortex. Restoring visually evoked activity in parvalbumin cells in Fmr1-/- mice with a chemogenetic strategy using designer receptors exclusively activated by designer drugs was sufficient to rescue their behavioral performance. Strikingly, human subjects with Fragile X syndrome exhibit impairments in visual discrimination similar to those in Fmr1-/- mice. These results suggest that manipulating inhibition may help sensory processing in Fragile X syndrome
Characterisation of Bombyx mori odorant-binding proteins reveals that a general odorant-binding protein discriminates between sex pheromone components
In many insect species, odorant-binding proteins (OBPs) are thought to be responsible for the transport of pheromones and other semiochemicals across the sensillum lymph to the olfactory receptors (ORs) within the antennal sensilla. In the silkworm Bombyx mori, the OBPs are subdivided into three main subfamilies; pheromone-binding proteins (PBPs), general odorant-binding proteins (GOBPs) and antennal-binding proteins (ABPs). We used the MotifSearch algorithm to search for genes encoding putative OBPs in B. mori and found 13, many fewer than are found in the genomes of fruit flies and mosquitoes. The 13 genes include seven new ABP-like OBPs as well as the previously identified PBPs (three), GOBPs (two) and ABPx. Quantitative examination of transcript levels showed that BmorPBP1, BmorGOBP1, BmorGOBP2 and BmorABPx are expressed at very high levels in the antennae and so could be involved in olfaction. A new two-phase binding assay, along with other established assays, showed that BmorPBP1, BmorPBP2, BmorGOBP2 and BmorABPx all bind to the B. mori sex pheromone component (10E,12Z)-hexadecadien-1-ol (bombykol). BmorPBP1, BmorPBP2 and BmorABPx also bind the pheromone component (10E,12Z)-hexadecadienal (bombykal) equally well, whereas BmorGOBP2 can discriminate between bombykol and bombykal. X-ray structures show that when bombykol is bound to BmorGOBP2 it adopts a different conformation from that found when it binds to BmorPBP1. Binding to BmorGOBP2 involves hydrogen bonding to Arg110 rather than to Ser56 as found for BmorPBP1
Presence of virus neutralizing antibodies in cerebral spinal fluid correlates with non-lethal rabies in dogs.
BACKGROUND: Rabies is traditionally considered a uniformly fatal disease after onset of clinical manifestations. However, increasing evidence indicates that non-lethal infection as well as recovery from flaccid paralysis and encephalitis occurs in laboratory animals as well as humans.
METHODOLOGY/PRINCIPAL FINDINGS: Non-lethal rabies infection in dogs experimentally infected with wild type dog rabies virus (RABV, wt DRV-Mexico) correlates with the presence of high level of virus neutralizing antibodies (VNA) in the cerebral spinal fluid (CSF) and mild immune cell accumulation in the central nervous system (CNS). By contrast, dogs that succumbed to rabies showed only little or no VNA in the serum or in the CSF and severe inflammation in the CNS. Dogs vaccinated with a rabies vaccine showed no clinical signs of rabies and survived challenge with a lethal dose of wild-type DRV. VNA was detected in the serum, but not in the CSF of immunized dogs. Thus the presence of VNA is critical for inhibiting virus spread within the CNS and eventually clearing the virus from the CNS.
CONCLUSIONS/SIGNIFICANCE: Non-lethal infection with wt RABV correlates with the presence of VNA in the CNS. Therefore production of VNA within the CNS or invasion of VNA from the periphery into the CNS via compromised blood-brain barrier is important for clearing the virus infection from CNS, thereby preventing an otherwise lethal rabies virus infection
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