6,407 research outputs found
Local‐Regional Similarity in Drylands Increases During Multiyear Wet and Dry Periods and in Response to Extreme Events
Climate change is predicted to impact ecosystems through altered precipitation (PPT) regimes. In the Chihuahuan Desert, multiyear wet and dry periods and extreme PPT pulses are the most influential climatic events for vegetation. Vegetation responses are most frequently studied locally, and regional responses are often unclear. We present an approach to quantify correlation of PPT and vegetation responses (as Normalized Difference Vegetation Index [NDVI]) at the Jornada ARS‐LTER site (JRN; 550 km2 area) and the surrounding dryland region (from 0 to 500 km distance; 400,000 km2 study area) as a way to understand regional similarity to locally observed patterns. We focused on fluctuating wet and dry years, multiyear wet or dry periods of 3–4 yr, and multiyear wet periods that contained one or more extreme high PPT pulses or extreme low rainfall. In all but extreme high PPT years, JRN PPT was highly correlated... (See article for full abstract)
Minimal Scenarios for Leptogenesis and CP Violation
The relation between leptogenesis and CP violation at low energies is
analyzed in detail in the framework of the minimal seesaw mechanism. Working,
without loss of generality, in a weak basis where both the charged lepton and
the right-handed Majorana mass matrices are diagonal and real, we consider a
convenient generic parametrization of the Dirac neutrino Yukawa coupling matrix
and identify the necessary condition which has to be satisfied in order to
establish a direct link between leptogenesis and CP violation at low energies.
In the context of the LMA solution of the solar neutrino problem, we present
minimal scenarios which allow for the full determination of the cosmological
baryon asymmetry and the strength of CP violation in neutrino oscillations.
Some specific realizations of these minimal scenarios are considered. The
question of the relative sign between the baryon asymmetry and CP violation at
low energies is also discussed.Comment: 36 pages, 5 figures; minor corrections and references updated. Final
version to appear in Phys. Rev.
A CMOS 130nm Evaluation digitzer chip for silicon strips readout
A CMOS 130nm evaluation chip intended to read Silicon strip detectors at the ILC has been designed and successfully tested. Optimized for a detector capacitance of 10 pF, it includes four channels of charge integration, pulse shaping, a 16-deep analogue sampler triggered on input analogue sums, and parallel analogue to digital conversion. Tests results of the full chain are reported, demonstrating the behaviour and performance of the full sampling process and analogue to digital conversion. Each channel dissipates less than one milli-Watt static power
ISS-flation
Inflation may occur while rolling into the metastable supersymmetry-breaking
vacuum of massive supersymmetric QCD. We explore the range of parameters in
which slow-roll inflation and long-lived metastable supersymmetry breaking may
be simultaneously realized. The end of slow-roll inflation in this context
coincides with the spontaneous breaking of a global symmetry, which may give
rise to significant curvature perturbations via inhomogenous preheating. Such
spontaneous symmetry breaking at the end of inflation may give rise to
observable non-gaussianities, distinguishing this scenario from more
conventional models of supersymmetric hybrid inflation.Comment: 26 page
Recommended from our members
Insertion devices for the Advanced Light Source at LBL
The Advanced Light Source (ALS) at the Lawrence Berkeley Laboratory will be the first of the new generation of dedicated synchrotron light sources to be put into operation. Specially designed insertion devices will be required to realize the high brightness photon beams made possible by the low emittance of the electron beam. The complement of insertion devices on the ALS will include undulators with periods as short as 3.9 cm and one or more high field wigglers. The first device to be designed is a 5 m long, 5 cm period, hybrid undulator. The goal of very high brightness and high harmonic output imposes unusually tight tolerances on the magnetic field quality and thus on the mechanical structure. The design process, using a generic structure for all undulators, is described. 5 refs., 4 figs., 1 tab
Infrastructure for Detector Research and Development towards the International Linear Collider
The EUDET-project was launched to create an infrastructure for developing and
testing new and advanced detector technologies to be used at a future linear
collider. The aim was to make possible experimentation and analysis of data for
institutes, which otherwise could not be realized due to lack of resources. The
infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture
Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV
We report on a search for anomalous production of events with at least two
charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1
sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a
signal region containing low background from Standard Model processes. To avoid
bias, we fix the final cuts before examining the event yield in the signal
region using control regions to test the Monte Carlo predictions. We observe no
events in the signal region, consistent with an expectation of
0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new
physics processes in both a signature-based context as well as within a
representative minimal supergravity (tanbeta = 3) model.Comment: 15 pages, 4 figures. Minor textual changes, cosmetic improvements to
figures and updated and expanded reference
Surface Nano-structured Coating for Improved Performance of Axial Piston Pumps
The work starts from the consideration that most of the power losses in a hydraulic pump is due to frictional losses made by the relative motion between moving parts. This fact is particularly true at low operating velocities, when the hydraulic lift effect must be able to maintain a minimum clearance in meatus to limit the volumetric losses. The potential of structured coatings at nanoscale, with super-hydrophobic and oleophobic characteristics, has never been exploited before in an industrial application. The work studies the potential application of nano-coating on piston slippers surface in a real industrial case. The aim is to develop a new industrial solution to increase the energetic efficiency of hydraulic pump used in earthmoving machines. The proposed solution is investigated using a dedicated test bench, designed to reproduce real working conditions of the pump. The results showa reduction of friction coefficient while changing working pressure and rotation velocity
Evidence for an Excess of Soft Photons in Hadronic Decays of Z^0
Soft photons inside hadronic jets converted in front of the DELPHI main
tracker (TPC) in events of qqbar disintegrations of the Z^0 were studied in the
kinematic range 0.2 < E_gamma < 1 GeV and transverse momentum with respect to
the closest jet direction p_T < 80 MeV/c. A clear excess of photons in the
experimental data as compared to the Monte Carlo predictions is observed. This
excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/-
0.27) x 10^{-3} gamma/jet in the specified kinematic region, while the expected
level of the inner hadronic bremsstrahlung (which is not included in the Monte
Carlo) is (0.340 +/- 0.001 +/- 0.038) x 10^{-3} gamma/jet. The ratio of the
excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8),
which is similar in strength to the anomalous soft photon signal observed in
fixed target experiments with hadronic beams.Comment: 37 pages, 9 figures, Accepted by Eur. Phys. J.
Search for Long-lived Charged Massive Particles in anti-p p Collisions at s**1/2 = 1.8 TeV
We report a search for production of long-lived charged massive particles in
a data sample of 90 pb^{-1} of \sqrt{s} = 1.8 TeV p anti-p collisions recorded
by the Collider Detector at Fermilab (CDF). The search uses the muon-like
penetration and anomalously high ionization energy loss signature expected for
such a particle to discriminate it from backgrounds. The data is found to agree
with background expectations, and cross section limits of \cal{O} (1) pb are
derived using two reference models, a stable quark and a stable scalar lepton.Comment: 14 pages, 3 figure
- …