1,078 research outputs found
Non-vanishing boundary effects and quasi-first order phase transitions in high dimensional Ising models
In order to gain a better understanding of the Ising model in higher
dimensions we have made a comparative study of how the boundary, open versus
cyclic, of a d-dimensional simple lattice, for d=1,...,5, affects the behaviour
of the specific heat C and its microcanonical relative, the entropy derivative
-dS/dU. In dimensions 4 and 5 the boundary has a strong effect on the critical
region of the model and for cyclic boundaries in dimension 5 we find that the
model displays a quasi first order phase transition with a bimodal energy
distribution. The latent heat decreases with increasing systems size but for
all system sizes used in earlier papers the effect is clearly visible once a
wide enough range of values for K is considered. Relations to recent rigorous
results for high dimensional percolation and previous debates on simulation of
Ising models and gauge fields are discussed.Comment: 12 pages, 27 figure
Limits on Production of Magnetic Monopoles Utilizing Samples from the DO and CDF Detectors at the Tevatron
We present 90% confidence level limits on magnetic monopole production at the
Fermilab Tevatron from three sets of samples obtained from the D0 and CDF
detectors each exposed to a proton-antiproton luminosity of
(experiment E-882). Limits are obtained for the production cross-sections and
masses for low-mass accelerator-produced pointlike Dirac monopoles trapped and
bound in material surrounding the D0 and CDF collision regions. In the absence
of a complete quantum field theory of magnetic charge, we estimate these limits
on the basis of a Drell-Yan model. These results (for magnetic charge values of
1, 2, 3, and 6 times the minimum Dirac charge) extend and improve previously
published bounds.Comment: 18 pages, 17 figures, REVTeX
MSSM Higgs-Boson Production at Hadron Colliders with Explicit CP Violation
Gluon fusion is the main production mechanism for Higgs bosons with masses up
to several hundred GeV in collisions at the CERN Large Hadron Collider. We
investigate the effects of the CP-violating phases on the fusion process
including both the sfermion-loop contributions and the one-loop induced
CP-violating scalar-pseudoscalar mixing in the minimal supersymmetric standard
model. With a universal trilinear parameter assumed, every physical observable
involves only the sum of the phases of the universal trilinear parameter
and the higgsino mass parameter . The phase affects the lightest
Higgs-boson production rate significantly through the neutral Higgs-boson
mixing and, for the masses around the lightest stop-pair threshold, it also
changes the production rate of the heavy Higgs bosons significantly through
both the stop and sbottom loops and the neutral Higgs-boson mixing.Comment: 28 pages, 8 figures. Some references and comments added. Typos
corrected. To appear in Phys. Rev.
Focus Point SUSY at the LHC Revisited
The estimation of the backgrounds for gluino signals in focus point
supersymmetry is extended by including the backgrounds from the production of
four third generation quarks in the analysis. We find that these backgrounds
are negligible if one uses the strong selection criteria proposed in the
literature (including this analysis) for heavy gluino searches. Softer
selection criteria often recommended for lighter gluino searches yield
backgrounds which are small but numerically significant. We have also repeated
the more conventional background calculations and compared our results with the
other groups. We find that the size of the total residual background estimated
by different groups using different event generators and hard kinematical cuts
agree approximately. In view of the theoretical uncertainties in the leading
order signal and background cross sections mainly due to the choice of the QCD
scale, the gluino mass reach at the LHC cannot be pinpointed. However,
requiring a signal with tagged b-jets (instead of the standard
choice of ) it is shown that gluino masses close to 2 TeV can be
probed at the LHC for a range of reasonable choices of the QCD scale for an
integrated luminosity of 300 fb.Comment: 17 pages, 4 figures, minor typos correctio
Top-squark searches at the Tevatron in models of low-energy supersymmetry breaking
We study the production and decays of top squarks (stops) at the Tevatron
collider in models of low-energy supersymmetry breaking. We consider the case
where the lightest Standard Model (SM) superpartner is a light neutralino that
predominantly decays into a photon and a light gravitino. Considering the
lighter stop to be the next-to-lightest Standard Model superpartner, we analyze
stop signatures associated with jets, photons and missing energy, which lead to
signals naturally larger than the associated SM backgrounds. We consider both
2-body and 3-body decays of the top squarks and show that the reach of the
Tevatron can be significantly larger than that expected within either the
standard supergravity models or models of low-energy supersymmetry breaking in
which the stop is the lightest SM superpartner. For a modest projection of the
final Tevatron luminosity, L = 4 fb-1, stop masses of order 300 GeV are
accessible at the Tevatron collider in both 2-body and 3-body decay modes. We
also consider the production and decay of ten degenerate squarks that are the
supersymmetric partners of the five light quarks. In this case we find that
common squark masses up to 360 GeV are easily accessible at the Tevatron
collider, and that the reach increases further if the gluino is light.Comment: 32 pages, 9 figures; references adde
Atmospheric deposition and precipitation are important predictors of inorganic nitrogen export to streams from forest and grassland watersheds: a large-scale data synthesis
Previous studies have evaluated how changes in atmospheric nitrogen (N) inputs and climate affect stream N concentrations and fluxes, but none have synthesized data from sites around the globe. We identified variables controlling stream inorganic N concentrations and fluxes, and how they have changed, by synthesizing 20 time series ranging from 5 to 51 years of data collected from forest and grassland dominated watersheds across Europe, North America, and East Asia and across four climate types (tropical, temperate, Mediterranean, and boreal) using the International Long-Term Ecological Research Network. We hypothesized that sites with greater atmospheric N deposition have greater stream N export rates, but that climate has taken a stronger role as atmospheric deposition declines in many regions of the globe. We found declining trends in bulk ammonium and nitrate deposition, especially in the longest time-series, with ammonium contributing relatively more to atmospheric N deposition over time. Among sites, there were statistically significant positive relationships between (1) annual rates of precipitation and stream ammonium and nitrate fluxes and (2) annual rates of atmospheric N inputs and stream nitrate concentrations and fluxes. There were no significant relationships between air temperature and stream N export. Our long-term data shows that although N deposition is declining over time, atmospheric N inputs and precipitation remain important predictors for inorganic N exported from forested and grassland watersheds. Overall, we also demonstrate that long-term monitoring provides understanding of ecosystems and biogeochemical cycling that would not be possible with short-term studies alone.publishedVersio
Susceptibility-Weighted Imaging in Patients with Pyogenic Brain Abscesses at 1.5T: Characteristics of the Abscess Capsule
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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