2,061 research outputs found
Observing Ultra High Energy Cosmic Particles from Space: SEUSO, the Super Extreme Universe Space Observatory Mission
The experimental search for ultra high energy cosmic messengers, from eV to beyond eV, at the very end of the known energy
spectrum, constitutes an extraordinary opportunity to explore a largely unknown
aspect of our universe. Key scientific goals are the identification of the
sources of ultra high energy particles, the measurement of their spectra and
the study of galactic and local intergalactic magnetic fields. Ultra high
energy particles might, also, carry evidence of unknown physics or of exotic
particles relics of the early universe. To meet this challenge a significant
increase in the integrated exposure is required. This implies a new class of
experiments with larger acceptances and good understanding of the systematic
uncertainties. Space based observatories can reach the instantaneous aperture
and the integrated exposure necessary to systematically explore the ultra high
energy universe. In this paper, after briefly summarising the science case of
the mission, we describe the scientific goals and requirements of the SEUSO
concept. We then introduce the SEUSO observational approach and describe the
main instrument and mission features. We conclude discussing the expected
performance of the mission
Effects of Top-quark Compositeness on Higgs Boson Production at the LHC
Motivated by the possibility that the right-handed top-quark (t_R) is
composite, we discuss the effects of dimension-six operators on the Higgs boson
production at the LHC. When t_R is the only composite particle among the
Standard Model (SM) particles, the (V+A)\otimes (V+A) type four-top-quark
contact interaction is expected to have the largest coefficient among the
dimension-six operators, according to the Naive Dimensional Analysis (NDA). We
find that, to lowest order in QCD and other SM interactions, the cross section
of the SM Higgs boson production via gluon fusion does not receive corrections
from one insertion of the new contact interaction vertex. We also discuss the
effects of other dimension-six operators whose coefficients are expected to be
the second and the third largest from NDA. We find that the operator which
consists of two t_R's and two SM Higgs boson doublets can recognizably change
the Higgs boson production cross section from the SM prediction if the cut-off
scale is \sim 1TeV.Comment: 12 pages, 7 figures. v2: explanations improved in Section 3, other
minor changes. Version published in JHE
Development of On-Shore Behavior Among Polar Bears (\u3ci\u3eUrsus maritimus\u3c/i\u3e) in the Southern Beaufort Sea: Inherited or Learned?
Polar bears (Ursus maritimus) are experiencing rapid and substantial changes to their environment due to global climate change. Polar bears of the southern Beaufort Sea (SB) have historically spent most of the year on the sea ice. However, recent reports from Alaska indicate that the proportion of the SB subpopulation observed onâshore during late summer and early fall has increased. Our objective was to investigate whether this onâshore behavior has developed through genetic inheritance, asocial learning, or through social learning. From 2010 to 2013, genetic data were collected from SB polar bears in the fall via hair snags and remote biopsy darting onâshore and in the spring from captures and remote biopsy darting on the sea ice. Bears were categorized as either onâshore or offâshore individuals based on their presence onâshore during the fall. Levels of genetic relatedness, firstâorder relatives, motherâoffspring pairs, and fatherâoffspring pairs were determined and compared within and between the two categories: onâshore versus offâshore. Results suggested transmission of onâshore behavior through either genetic inheritance or social learning as there was a higher than expected number of firstâorder relatives exhibiting onâshore behavior. Genetic relatedness and parentage data analyses were in concurrence with this finding, but further revealed motherâoffspring social learning as the primary mechanism responsible for the development of onâshore behavior. Recognizing that onâshore behavior among polar bears was predominantly transmitted via social learning from mothers to their offspring has implications for future management and conservation as sea ice continues to decline
Single nucleotide polymorphisms (SNPs) in genes related to innate immune response against Salmonella in nursery pigs
The objective of this study was to investigate the association of single nucleotide polymorphisms (SNPs) in innate immune response genes with Salmonella shedding in nursery pigs. One hundred and sixty eight pigs on seven farrow-to- finish farms and one farrow-feeder operation were included in the study. On each farm, 21 pigs were selected from seven sows at weaning. Fecal samples were collected from selected pigs and cultured for Salmonella, and the isolates were serotyped. DNA was extracted from liver samples and used to genotype pigs for single nucleotide polymorphisms (SNPs) in 21 different innate immune response genes. In total, 15 (9.3%) pigs tested positive for Salmonella; the isolates from six pigs from four different litters on one farm were serotyped as Salmonella Infantis and from nine pigs from six different litters on another farm as Salmonella Worthington. SNP analysis showed an association of Salmonella shedding with a SNP in the genes encoding mannan-binding lectin (MBL)-associated serine protease-2 (MASP-2) and Toll-like receptor-1 (TLR-1) (P \u3c 0.05). These findings suggest that Salmonella shedding in pigs is controlled by genetic elements and these genetic variants could possibly be used to breed pigs that are more resistant to Salmonella colonization and Salmonella shedding
Top Compositeness at the Tevatron and LHC
We explore the possibility that the right-handed top quark is composite. We
examine the consequences that compositeness would have on
production at the Tevatron, and derive a weak constraint on the scale of
compositeness of order a few hundred GeV from the inclusive cross
section. More detailed studies of differential properties of
production could potentially improve this limit. We find that a composite top
can result in an enhancement of the production rate at
the LHC (of as much as compared to the Standatd Model four top rate). We
explore observables which allow us to extract the four top rate from the
backgrounds, and show that the LHC can either discover or constrain top
compositeness for wide ranges of parameter space.Comment: 9 pages, 4 figure
Spin properties of dense near-surface ensembles of nitrogen-vacancy centres in diamond
We present a study of the spin properties of dense layers of near-surface
nitrogen-vacancy (NV) centres in diamond created by nitrogen ion implantation.
The optically detected magnetic resonance contrast and linewidth, spin
coherence time, and spin relaxation time, are measured as a function of
implantation energy, dose, annealing temperature and surface treatment. To
track the presence of damage and surface-related spin defects, we perform in
situ electron spin resonance spectroscopy through both double electron-electron
resonance and cross-relaxation spectroscopy on the NV centres. We find that,
for the energy (~keV) and dose (~ions/cm)
ranges considered, the NV spin properties are mainly governed by the dose via
residual implantation-induced paramagnetic defects, but that the resulting
magnetic sensitivity is essentially independent of both dose and energy. We
then show that the magnetic sensitivity is significantly improved by
high-temperature annealing at C. Moreover, the spin properties
are not significantly affected by oxygen annealing, apart from the spin
relaxation time, which is dramatically decreased. Finally, the average NV depth
is determined by nuclear magnetic resonance measurements, giving
-17~nm at 4-6 keV implantation energy. This study sheds light on the
optimal conditions to create dense layers of near-surface NV centres for
high-sensitivity sensing and imaging applications.Comment: 12 pages, 7 figure
Soft-Wall Stabilization
We propose a general class of five-dimensional soft-wall models with AdS
metric near the ultraviolet brane and four-dimensional Poincar\'e invariance,
where the infrared scale is determined dynamically. A large UV/IR hierarchy can
be generated without any fine-tuning, thus solving the electroweak/Planck scale
hierarchy problem. Generically, the spectrum of fluctuations is discrete with a
level spacing (mass gap) provided by the inverse length of the wall, similar to
RS1 models with Standard Model fields propagating in the bulk. Moreover two
particularly interesting cases arise. They can describe: (a) a theory with a
continuous spectrum above the mass gap which can model unparticles
corresponding to operators of a CFT where the conformal symmetry is broken by a
mass gap, and; (b) a theory with a discrete spectrum provided by linear Regge
trajectories as in AdS/QCD models.Comment: 27 pages, 6 figures, 1 table. v2: references added, version to appear
in NJP Focus Issue on Extra Dimension
Spatial mapping of band bending in semiconductor devices using in-situ quantum sensors
Band bending is a central concept in solid-state physics that arises from
local variations in charge distribution especially near semiconductor
interfaces and surfaces. Its precision measurement is vital in a variety of
contexts from the optimisation of field effect transistors to the engineering
of qubit devices with enhanced stability and coherence. Existing methods are
surface sensitive and are unable to probe band bending at depth from surface or
bulk charges related to crystal defects. Here we propose an in-situ method for
probing band bending in a semiconductor device by imaging an array of
atomic-sized quantum sensing defects to report on the local electric field. We
implement the concept using the nitrogen-vacancy centre in diamond, and map the
electric field at different depths under various surface terminations. We then
fabricate a two-terminal device based on the conductive two-dimensional hole
gas formed at a hydrogen-terminated diamond surface, and observe an unexpected
spatial modulation of the electric field attributed to a complex interplay
between charge injection and photo-ionisation effects. Our method opens the way
to three-dimensional mapping of band bending in diamond and other
semiconductors hosting suitable quantum sensors, combined with simultaneous
imaging of charge transport in complex operating devices.Comment: This is a pre-print of an article published in Nature Electronics.
The final authenticated version is available online at
https://dx.doi.org/10.1038/s41928-018-0130-
After the Standard Model: New Resonances at the LHC
Experiments will soon start taking data at CERN's Large Hadron Collider (LHC)
with high expectations for discovery of new physics phenomena. Indeed, the
LHC's unprecedented center-of-mass energy will allow the experiments to probe
an energy regime where the standard model is known to break down. In this
article, the experiments' capability to observe new resonances in various
channels is reviewed.Comment: Preprint version of a Brief Review for Modern Physics Letters A.
Changes w.r.t. the fully corrected version are smal
Probing RS scenarios of flavour at LHC via leptonic channels
We study a purely leptonic signature of the Randall-Sundrum scenario with
Standard Model fields in the bulk at LHC: the contribution from the exchange of
Kaluza-Klein (KK) excitations of gauge bosons to the clear Drell-Yan reaction.
We show that this contribution is detectable (even with the low luminosities of
the LHC initial regime) for KK masses around the TeV scale and for sufficiently
large lepton couplings to KK gauge bosons. Such large couplings can be
compatible with ElectroWeak precision data on the Zff coupling in the framework
of the custodial O(3) symmetry recently proposed, for specific configurations
of lepton localizations (along the extra dimension). These configurations can
simultaneously reproduce the correct lepton masses, while generating acceptably
small Flavour Changing Neutral Current (FCNC) effects. This LHC
phenomenological analysis is realistic in the sense that it is based on fermion
localizations which reproduce all the quark/lepton masses plus mixing angles
and respect FCNC constraints in both the hadron and lepton sectors.Comment: 15 pages, 6 Figures, Latex fil
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