1,668 research outputs found
S-particles at their naturalness limits
We draw attention on a particular configuration of supersymmetric particle
masses, motivated by naturalness and flavour considerations. All its relevant
phenomenological properties for the LHC are described in terms of a few
physical parameters, irrespective of the underlying theoretical model. This
allows a simple characterization of its main features, useful to define a
strategy for its discovery.Comment: 13 pages, 8 figures, added reference
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
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
Some thoughts on the monitoring and preservation of waterlogged archaeological sites in eastern England
This study reviews five hydrological monitoring projects used on archeological sites in the waterlogged landscapes of fenland East Anglia and east Yorkshire in England. The project design, recorded variables, and implications of each are discussed. In particular, the importance of understanding the landscape context is paramount, and retrieving an appropriate dataset over a sufficiently lengthy period of time to obtain reliable results and predictability. Some of the lessons learnt and outstanding problems are explored. As former wetlands are fast disappearing around the world through dewatering and a host of wider development threats such as urbanization and gravel extraction, the low intrusion suite of methods described here for measuring the degree and certainty of organic preservation is doubly important for establishing the viability of preservation in situ schemes for waterlogged archeological sites. This is crucial to get right, as wetland archeological records are an irreplaceable resource which offer extraordinarily full and diverse datasets of human lifeways which are all too often either poorly preserved or erroneously interpreted because of the skewed datasets recovered from dryland sites.English Heritage, Huntings Technical Services (for Over), ARC (Central) Ltd. (for Etton), Hanson Building Products and SLR Consulting Ltd. (for Must Farm), the Society of Antiquaries and Fenland Archaeological Trust (for Etton), Cambridge Archaeological Unit (for Over and Must Farm), the McBurney Laboratory and the McDonald Institute for Archaeological Research, University of Cambridge (for Over and Must Farm), the Department of Archaeology, University of York and the European Research Council (for Star Carr), and the Meteorological Office (for Etton and Over
Manifestations of Top Compositeness at Colliders
We explore the possibility that the right-handed top quark is composite,
identifying possible signatures of compositeness and how they might manifest
themselves at the LHC and Tevatron. We perform a complete analysis of the
dimension six modifications of the top coupling to gluons and find that
cancellations among operators in the t\bar{t} rate allow for very low
compositeness scales, but this can be drastically improved by looking at
kinematic distributions. Turning to the LHC, we examine four top production
from a dimension six four-top operator and estimate the LHC with 100 {\rm
fb}^{-1} collected luminosity to be sensitive to compositeness scales as high
as 5 TeV.Comment: 8 pages, 6 figures, updated figure 6, updated references, final
version published in JHE
Heavy-light decay topologies as a new strategy to discover a heavy gluon
We study the collider phenomenology of the lightest Kaluza-Klein excitation
of the gluon, G*, in theories with a warped extra dimension. We do so by means
of a two-site effective lagrangian which includes only the lowest-lying spin-1
and spin-1/2 resonances. We point out the importance of the decays of G* to one
SM plus one heavy fermion, that were overlooked in the previous literature. It
turns out that, when kinematically allowed, such heavy-light decays are
powerful channels for discovering the G*. In particular, we present a
parton-level Montecarlo analysis of the final state Wtb that follows from the
decay of G* to one SM top or bottom quark plus its heavy partner. We find that
at \sqrt{s} = 7 TeV and with 10 fb^{-1} of integrated luminosity, the LHC can
discover a KK gluon with mass in the range M_{G*} = (1.8 - 2.2) TeV if its
coupling to a pair of light quarks is g_{G*qqbar} = (0.2-0.5) g_3. The same
process is also competitive for the discovery of the top and bottom partners as
well. We find, for example, that the LHC at \sqrt{s} = 7 TeV can discover a 1
TeV KK bottom quark with an integrated luminosity of (5.3 - 0.61) fb^{-1} for
g_{G*qqbar} = (0.2-0.5) g_3.Comment: 36 pages, 13 figures. v2: a few typos corrected, comments added,
version published in JHE
New Higgs Production Mechanism in Composite Higgs Models
Composite Higgs models are only now starting to be probed at the Large Hadron
Collider by Higgs searches. We point out that new resonances, abundant in these
models, can mediate new production mechanisms for the composite Higgs. The new
channels involve the exchange of a massive color octet and single production of
new fermion resonances with subsequent decays into the Higgs and a Standard
Model quark. The sizable cross section and very distinctive kinematics allow
for a very clean extraction of the signal over the background with high
statistical significance. Heavy gluon masses up to 2.8 TeV can be probed with
data collected during 2012 and up to 5 TeV after the energy upgrade to
TeV.Comment: 27 pages, 22 figures. V2: typos corrected, matches published versio
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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