2,078 research outputs found
Search for displaced vertexes arising from decays of new, heavy particles in 7 TeV pp collisions in ATLAS
We present the results of a search for neutralinos decaying at a significant
distance from their production point into charged hadrons and a high momentum
muon, forming displaced vertexes. The analysis was performed with 33 pb^-1 of
pp collision data collected by the ATLAS experiment at the LHC in 2010 at
sqrt{s}= 7 TeV. The poster will show some highlights of the analysis.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 9 figure
Considerations on Xi- reconstruction in LHCb
This paper describes an alternative method of charged hyperon reconstruction
applicable to the LHCb experiment. It extends the seminal work of the FOCUS
collaboration to the specific detector layout of LHCb and addresses the
reconstruction ambiguities reported in their earlier work, leading to
improvements in the reconstruction efficiency for the specific cases of Xi- and
Omega- baryon decays to a charged meson and a Lambda baryon.Comment: 5 pages, 4 figure
Spectra of Field Fluctuations in Braneworld Models with Broken Bulk Lorentz Invariance
We investigate five-dimensional braneworld setups with broken Lorentz
invariance continuing the developments of our previous paper (arXiv:0712.1136),
where a family of static self-tuning braneworld solutions was found. We show
that several known braneworld models can be embedded into this family. Then we
give a qualitative analysis of spectra of field fluctuations in backgrounds
with broken Lorentz invariance. We also elaborate on one particular model and
study spectra of scalar and spinor fields in it. It turns out that the spectra
we have found possess very peculiar and unexpected properties.Comment: 30 pages, 8 figures, minor corrections, references added, note adde
31 GEANT4 simulation of dose deposition in patients from TomoTherapy Hi-Art Megavoltage computed tomography (MVCT) imaging
Report of the GDR working group on the R-parity violation
This report summarizes the work of the "R-parity violation group" of the
French Research Network (GDR) in Supersymmetry, concerning the physics of
supersymmetric models without conservation of R-parity at HERA, LEP, Tevatron
and LHC and limits on R-parity violating couplings from various processes. The
report includes a discussion of the recent searches at the HERA experiment,
prospects for new experiments, a review of the existing limits, and also
theoretically motivated alternatives to R-parity and a brief discussion on the
implications of R-parity violation on the neutrino masses.Comment: 60 pages, LaTeX, 22 figures, 2 table
High leptin/adiponectin ratio and serum triglycerides are associated with an "at-risk" phenotype in young severely obese patients.
New type of microengine using internal combustion of hydrogen and oxygen
Microsystems become part of everyday life but their application is restricted
by lack of strong and fast motors (actuators) converting energy into motion.
For example, widespread internal combustion engines cannot be scaled down
because combustion reactions are quenched in a small space. Here we present an
actuator with the dimensions 100x100x5 um^3 that is using internal combustion
of hydrogen and oxygen as part of its working cycle. Water electrolysis driven
by short voltage pulses creates an extra pressure of 0.5-4 bar for a time of
100-400 us in a chamber closed by a flexible membrane. When the pulses are
switched off this pressure is released even faster allowing production of
mechanical work in short cycles. We provide arguments that this unexpectedly
fast pressure decrease is due to spontaneous combustion of the gases in the
chamber. This actuator is the first step to truly microscopic combustion
engines.Comment: Paper and Supplementary Information (to appear in Scientific Reports
ScotGrid: Providing an Effective Distributed Tier-2 in the LHC Era
ScotGrid is a distributed Tier-2 centre in the UK with sites in Durham,
Edinburgh and Glasgow. ScotGrid has undergone a huge expansion in hardware in
anticipation of the LHC and now provides more than 4MSI2K and 500TB to the LHC
VOs. Scaling up to this level of provision has brought many challenges to the
Tier-2 and we show in this paper how we have adopted new methods of organising
the centres, from fabric management and monitoring to remote management of
sites to management and operational procedures, to meet these challenges. We
describe how we have coped with different operational models at the sites,
where Glagsow and Durham sites are managed "in house" but resources at
Edinburgh are managed as a central university resource. This required the
adoption of a different fabric management model at Edinburgh and a special
engagement with the cluster managers. Challenges arose from the different job
models of local and grid submission that required special attention to resolve.
We show how ScotGrid has successfully provided an infrastructure for ATLAS and
LHCb Monte Carlo production. Special attention has been paid to ensuring that
user analysis functions efficiently, which has required optimisation of local
storage and networking to cope with the demands of user analysis. Finally,
although these Tier-2 resources are pledged to the whole VO, we have
established close links with our local physics user communities as being the
best way to ensure that the Tier-2 functions effectively as a part of the LHC
grid computing framework..Comment: Preprint for 17th International Conference on Computing in High
Energy and Nuclear Physics, 7 pages, 1 figur
A New Eusuchian Crocodyliform with Novel Cranial Integument and Its Significance for the Origin and Evolution of Crocodylia
Crocodyliforms were one of the most successful groups of Mesozoic tetrapods, radiating into terrestrial, semiaquatic and marine environments, while occupying numerous trophic niches, including carnivorous, insectivorous, herbivorous, and piscivorous species. Among these taxa were the enigmatic, poorly represented flat-headed crocodyliforms from the late Cretaceous of northern Africa. Here we report a new, giant crocodyliform from the early Late Cretaceous (Cenomanian) Kem Kem Formation of Morocco. Represented by a partial braincase, the taxon has an extremely long, flat skull with large jaw and craniocervical muscles. The skull roof is ridged and ornamented with a broad, rough boss surrounded by significant vascular impressions, likely forming an integumentary structure unique among crocodyliforms. Size estimates using endocranial volume indicate the specimen was very large. The taxon possesses robust laterosphenoids with laterally oriented capitate processes and isolated epipterygoids, features allying it with derived eusuchians. Phylogenetic analysis finds the taxon to be a derived eusuchian and sister taxon to Aegyptosuchus, a poorly understood, early Late Cretaceous taxon from the Bahariya formation. This clade forms the sister clade of crown-group Crocodylia, making these taxa the earliest eusuchian crocodyliforms known from Africa. These results shift phylogenetic and biogeographical hypotheses on the origin of modern crocodylians towards the circum-Tethyean region and provide important new data on eusuchian morphology and evolution
A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania
BACKGROUND: The fossil record reveals surprising crocodile diversity in the Neogene of Africa, but relationships with their living relatives and the biogeographic origins of the modern African crocodylian fauna are poorly understood. A Plio-Pleistocene crocodile from Olduvai Gorge, Tanzania, represents a new extinct species and shows that high crocodylian diversity in Africa persisted after the Miocene. It had prominent triangular "horns" over the ears and a relatively deep snout, these resemble those of the recently extinct Malagasy crocodile Voay robustus, but the new species lacks features found among osteolaemines and shares derived similarities with living species of Crocodylus. METHODOLOGY/PRINCIPAL FINDINGS: The holotype consists of a partial skull and skeleton and was collected on the surface between two tuffs dated to approximately 1.84 million years (Ma), in the same interval near the type localities for the hominids Homo habilis and Australopithecus boisei. It was compared with previously-collected material from Olduvai Gorge referable to the same species. Phylogenetic analysis places the new form within or adjacent to crown Crocodylus. CONCLUSIONS/SIGNIFICANCE: The new crocodile species was the largest predator encountered by our ancestors at Olduvai Gorge, as indicated by hominid specimens preserving crocodile bite marks from these sites. The new species also reinforces the emerging view of high crocodylian diversity throughout the Neogene, and it represents one of the few extinct species referable to crown genus Crocodylus
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