3,341 research outputs found
Particle identification for Higgs physics in the ATLAS experiment
ATLAS is a general purpose experiment which will operate at the LHC. In the main focus of ATLAS is the investigation of the nature of the electroweak symmetry breaking, and therefore the search for the Higgs boson. Electrons, photons, muons, tau and b-jets are important components of the possible physics signatures expected. Thus the particle-ID impose strong requirements upon the performance of the detector, it has to be sensitive to Higgs boson over the full range of allowed masses. In this paper, the detector performance in terms of particle identification is presented
Application of TauSpinner for studies on tau-lepton polarization and spin correlations in Z, W and H decays at LHC
The tau-lepton plays an important role in the physics program at LHC. Its
spin can be used for separation of signal from background or in measuring
properties of New Particles decaying to tau leptons.
The TauSpinner package represents a tool to modify tau spin effects in any
sample containing tau leptons. Generated events, featuring taus produced from
intermediate state W, Z, H bosons can be used as an input. The information on
the polarization and spin correlations is reconstructed from the kinematics of
the tau lepton(s) (nutau in case of W-mediated processes) and tau decay
products. By weights, attributed on the event-by-event basis, it enables
numerical evaluation and/or modification of the spin effects.
We review distributions to monitor spin effects in leptonic and hadronic tau
decays with up to three pions, to provide benchmarks for validation of spin
content of the event sample and to visualize the tau lepton spin polarization
and correlation effects. The demonstration examples for use of TauSpinner
libraries, are documented. New validation methods of such an approach are
provided. Other topics, like TauSpinner systematic errors or sensitivity of
experimental distributions to spin, are addressed in part only.
This approach is of interest for implementation of spin effects in embedded
tau lepton samples, where Z to mu mu events from data of muons are replaced by
simulated tau leptons. Embedding is used at LHC for estimating Z to tau tau
background to H to tau tau signatures.Comment: 1+41 pages, 5 figures in main text, multitude of figures in
appendice
Turbulent Mixing in Bottom Boundary Layer of the Coastal Ocean
This paper analyses the evolution of the bottom boundary layer observed over a flood tide in
the Plymouth Sound in June 2006. The overview of the energy budget associated with
turbulence is presented in which an estimation of turbulent energy dissipation and production
in the boundary layer is performed. Turbulent characteristics are calculated from data
collected by two Acoustic Doppler Velocimeters (ADV) located at 69 cm and 52 cm above
the sea bed. The same turbulent characteristics are calculated, but applying different
methods, using the velocity measured by a downlooking 1200 kHz Acoustics Doppler
Current Profiler (ADCP) installed at a height 1.36m above the bed. The study compares
turbulent characteristics calculated from data collected by two different types of instruments.
Additionally, the currents in the whole water column are examined by analysing profiles of
velocity collected by 600 kHz ADCP. The study checks whether the velocities measured by
the two ADCPs are consistent with each other and examines the possible effects of density
stratification on turbulence in the bottom boundary layer.
It was found that the flow was an effect of semidiurnal tide with the maximum velocities of
22cm/s observed two hours after Low Water 4m above the bed. Velocity profiles, measured
by the two ADCP, did not overlap each other but the results are consistent with each other.
Measurements performed by both ADVs showed the same magnitudes and trends in the
mean velocity as the 1.2MHz ADCP. The results indicated weak stratification in the water
column. Velocities measured by 1.2MHz ADCP had logarithmic profiles from which the
friction velocity (u*) and bed stress (τb) were calculated. The characteristics had similar
values (u*<1cm/s, τb<0.09Pa) as reported previously for similar conditions (flat bed, tidal
channel, unstratified water column). Dissipation rate (ε) calculated from the two ADVs
provided inaccurate results which were three orders of a magnitude higher than that obtained
from the higher frequency ADCP (10-8-10-6 W/kg). That difference was found to be
associated with the assumptions of the first method, which were not fulfilled. The production
of TKE (P), from ADVs and the 1.2MHz ADCP, had the same magnitude than ε and the
average ε/P ratio, over the whole time of deployment, was found to be 1.45 +/- 1.07.
However, the ratio was biased by the high ε during run 2. After rejecting that run the ratio
was closer to the expected value of unity: 0.78 +/- 0.36
Tau leptons as a probe for new physics at LHC
The tau leptons identification with ATLAS experiment will be possible already at the early start of the data taking. The copius production of W and Z bosons decaying to the tau leptons will provide unique possibility to calibrate and undertand identification of hadronically decaying tau's above the QCD background already with few hundreds of pb-1. With integrated luminosity of tens of fb-1, tau leptons will become an excellent probe for searching for the SM and MSSM Higgs boson, SUSY or extra dimensions. In the talk we review prospect for early physics and searches scenarios involving tau leptons
Kinetics of gas emission from aluminosilicates used as a relaxing additive for moulding and core sands
The article presents the results of gas emissions generated during heating of mineral additives – aluminosilicates (perlite ore and vermiculite). The test on a laboratory stand for a 1 g sample at 1 000 °C was carried out. It has been shown, that there is a correlation between the degree of fragmentation and the amount of gas generated. The finest fraction of perlite ore caused a similar quantitative gas emission as ground vermiculite. The presence of additives in molding sands, regardless of the size of fraction, should not affect the formation of casting defects. The addition of perlite ore and vermiculite does not effect the ecological properties of moulding sand
Metamagnetism in the XXZ model with next-to-nearest-neighbor coupling
We investigate groundstate energies and magnetization curves in the one
dimensional XXZ-model with next to nearest neighbour coupling and
anisotropy () at T=0. In between the familiar
ferro- and antiferromagnetic phase we find a transition region -- called
metamagnetic phase -- where the magnetization curve is discontinuous at a
critical field .Comment: LaTeX file (text) + 5 PS files (5 figures
The influence of pollen viability on seed set and fruit mass in strawberry (fragaria x ananassa duch.)
This research was conducted in 2006 in the Experimental Station of the Department of Genetics and Horticultural Plant Breeding in Felin near Lublin. It included 7 cultivars of strawberry ('Pastel', 'Salut', 'Teresa', 'Jota', 'Paula', 'Senga Sengana', 'Plena') and two selected clones: 2395 and 3995 that belonged to the Department. Analysis of pollen fertility was carried out on the basis of materials collected on five occasions: on May 17 (at the beginning of florescence), May 20 and May 24 (the peak of florescence) and on June 2 and June 13 (the end of florescence). Smear preparations stained with 2% acetocarmin and glycerin solution (1:1) were used to test pollen viability. The highest percent of viable pollen in 2006 was in cultivar 'Jota' (70.88%). The lowest viability had pollen of 'Teresa' cultivar (33.83%). The average content of viable pollen grains was the lowest on May 20 (36.79%). The highest pollen fertility was noted on June 2 (62.15%), the percent of fertile pollen on a similar level was observed on May 17 and 24 and June13. The cultivar 'Jota' was characterized by an increased level of pollen fertility that was quite high during the whole period of florescence. The number of seeds has a great influence on the proper development of spurious strawberry fruit. The mass of seeds from a single fruit has a great influence on the mass of fruits in both large and small fruit categories. Pollen viability affected the mass of seeds on big fruits (r = 0.444), but there is no clear direct relationship between pollen fertility and mass of strawberry fruit(r = -0.193 and r = -0.052)
A doubly stochastic rainfall model with exponentially decaying pulses
We develop a doubly stochastic point process model with exponentially decaying pulses to describe the statistical properties of the rainfall intensity process. Mathematical formulation of the point process model is described along with second-order moment characteristics of the rainfall depth and aggregated processes. The derived second-order properties of the accumulated rainfall at different aggregation levels are used in model assessment. A data analysis using 15 years of sub-hourly rainfall data from England is presented. Models with fixed and variable pulse lifetime are explored. The performance of the model is compared with that of a doubly stochastic rectangular pulse model. The proposed model fits most of the empirical rainfall properties well at sub-hourly, hourly and daily aggregation levels
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