3,117 research outputs found
Shedding light on the asymmetry: the photon handle
We investigate a charge asymmetry in production at the LHC
that provides complementary information to the measured asymmetries in production. We estimate the experimental uncertainty in its measurement at
the LHC with 8 and 14 TeV. For new physics models that simultaneously reproduce
the asymmetry excess in at the Tevatron and the SM-like asymmetry at
the LHC, the measurement in at the LHC could exhibit
significant deviations with respect to the SM prediction.Comment: LaTeX 15 page
Physiological-enzymatic characteristics and inoculation of mycelial strains of Descolea antarctica Sing. in Nothofagus seedlings
At present, reforestation has focused on native forests with
anthropogenic intervention and eroded soils. There is interest in
producing Nothofagus seedlings which can overcome adverse conditions
encountered on reforestation sites. It is necessary to find new fungi
that can be utilized as mycorrhizal inoculants and that enable the
seedlings to increase their tolerance to adverse conditions. Two
ectomycorrhizal strains of the fungus Descolea antarctica (D1 and D2)
were cultured at different temperatures, pH levels and the activities
of amylases, cellulases, and phosphatases were determined. In
greenhouse and nursery trials, the growth responses of inoculated
Nothofagus obliqua seedlings were evaluated. D1 and D2 exhibited the
highest growth rates at 23\ubaC. Both strains grew at pH levels from
4 to 11. The highest enzymatic activities were registered for amylase
(57.2 mg glucose/ml * g of mycelium * hr) and acid phosphatases (58.1
mg p-nitrophenol/ml * g of mycelium * hr) at 37\ubaC, and acid
phospatases (1.720 mg p-nitrophenol/ml * g of mycelium * hr) and
alkaline phosphatases (1.360 mg p-nitrophenol/ml * g of mycelium * hr)
at pH 4 and pH 11, respectively. We conclude that suitable N. obliqua
seedlings for use in reforestation were obtained using D2 as inoculant
Snf2h Primes UL Neuron Production
Alterations in the homeostasis of either cortical progenitor pool, namely the apically located radial glial (RG) cells or the basal intermediate progenitors (IPCs) can severely impair cortical neuron production. Such changes are reflected by microcephaly and are often associated with cognitive defects. Genes encoding epigenetic regulators are a frequent cause of intellectual disability and many have been shown to regulate progenitor cell growth, including our inactivation of the Smarca1 gene encoding Snf2l, which is one of two ISWI mammalian orthologs. Loss of the Snf2l protein resulted in dysregulation of Foxg1 and IPC proliferation leading to macrocephaly. Here we show that inactivation of the closely related Smarca5 gene encoding the Snf2h chromatin remodeler is necessary for embryonic IPC expansion and subsequent specification of callosal projection neurons. Telencephalon-specific Smarca5 cKO embryos have impaired cell cycle kinetics and increased cell death, resulting in fewer Tbr2+ and FoxG1+ IPCs by mid-neurogenesis. These deficits give rise to adult mice with a dramatic reduction in Satb2C upper layer neurons, and partial agenesis of the corpus callosum. Mice survive into adulthood but molecularly display reduced expression of the clustered protocadherin genes that may further contribute to altered dendritic arborization and a hyperactive behavioral phenotype. Our studies provide novel insight into the developmental function of Snf2h-dependent chromatin remodeling processes during brain development
The Large Aperture GRB Observatory
The Large Aperture GRB Observatory (LAGO) is aiming at the detection of the
high energy (around 100 GeV) component of Gamma Ray Bursts, using the single
particle technique in arrays of Water Cherenkov Detectors (WCD) in high
mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela,
4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). WCD at high altitude offer
a unique possibility of detecting low gamma fluxes in the 10 GeV - 1 TeV range.
The status of the Observatory and data collected from 2007 to date will be
presented.Comment: 4 pages, proceeding of 31st ICRC 200
Water Cherenkov Detectors response to a Gamma Ray Burst in the Large Aperture GRB Observatory
In order to characterise the behaviour of Water Cherenkov Detectors (WCD)
under a sudden increase of 1 GeV - 1 TeV background photons from a Gamma Ray
Burst (GRB), simulations were conducted and compared to data acquired by the
WCD of the Large Aperture GRB Observatory (LAGO). The LAGO operates arrays of
WCD at high altitude to detect GRBs using the single particle technique. The
LAGO sensitivity to GRBs is derived from the reported simulations of the gamma
initiated particle showers in the atmosphere and the WCD response to
secondaries.Comment: 5 pages, proceeding of the 31st ICRC 200
Simple models for the top asymmetry: constraints and predictions
We perform a comprehensive study of the allowed range for the Tevatron t tbar
forward-backward asymmetries in six representative new physics models: a
flavour-changing Z' boson, a scalar isodoublet, a W' boson, a heavy axigluon, a
colour-triplet and a colour-sextet scalar. We devote special attention to the
constraints from the t tbar tail at LHC on the parameter space, which will be
dramatic if the measurements agree with the SM prediction, specially for Z' and
W' bosons. We also study the predictions for the charge asymmetries at LHC and
compare several proposed definitions.Comment: LaTeX 27 pages. Version to appear in JHE
Z' signals in polarised top-antitop final states
We study the sensitivity of top-antitop samples produced at all energy stages
of the Large Hadron Collider (LHC) to the nature of an underlying Z' boson, in
presence of full tree level standard model (SM) background effects and relative
interferences. We concentrate on differential mass spectra as well as both
spatial and spin asymmetries thereby demonstrating that exploiting combinations
of these observables will enable one to distinguish between sequential Z's and
those pertaining to Left-Right symmetric models as well as E6 inspired ones,
assuming realistic final state reconstruction efficiencies and error estimates.Comment: 21 pages, 6 colour figures, 10 table
Top quark forward-backward asymmetry in R-parity violating supersymmetry
The interaction of bottom squark-mediated top quark pair production,
occurring in the R-parity violating minimal supersymmetric standard model
(MSSM), is proposed as an explanation of the anomalously large
forward-backward asymmetry (FBA) observed at the Tevatron. We find that this
model can give a good fit to top quark data, both the inclusive and invariant
mass-dependent asymmetries, while remaining consistent (at the 2-
level) with the total and differential production cross-sections. The scenario
is challenged by strong constraints from atomic parity violation (APV), but we
point out an extra diagram for the effective down quark-Z vertex, involving the
same coupling constant as required for the FBA, which tends to weaken the APV
constraint, and which can nullify it for reasonable values of the top squark
masses and mixing angle. Large contributions to flavor-changing neutral
currents can be avoided if only the third generation of sparticles is light.Comment: 24 pages, 7 figures. v3: included LHC top production cross section
data; model still consistent at 2 sigma leve
Complementarity of the CERN Large Hadron Collider and the International Linear Collider
The next-generation high-energy facilities, the CERN Large Hadron Collider
(LHC) and the prospective International Linear Collider (ILC), are
expected to unravel new structures of matter and forces from the electroweak
scale to the TeV scale. In this report we review the complementary role of LHC
and ILC in drawing a comprehensive and high-precision picture of the mechanism
breaking the electroweak symmetries and generating mass, and the unification of
forces in the frame of supersymmetry.Comment: 14 pages, 17 figures, to be published in "Supersymmetry on the Eve of
the LHC", a special volume of European Physical Journal C, Particles and
Fields (EPJC) in memory of Julius Wes
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