11,051 research outputs found
Limiting fragmentation from scale-invariant merging of fast partons
Exploiting the idea that the fast partons of an energetic projectile can be
treated as sources of color radiation interpreted as wee partons, it is shown
that the recently observed property of extended limiting fragmentation implies
a scaling law for the rapidity distribution of fast partons. This leads to a
picture of a self-similar process where, for fixed total rapidity Y, the
sources merge with probability varying as 1/y.Comment: 10 pages, 1 figure (2 eps files). Final version, also updated w.r.t.
the published version in Phys. Lett. B665/1 (2008) pp. 35-3
Verification-guided modelling of salience and cognitive load
Well-designed interfaces use procedural and sensory cues to increase the cognitive salience of appropriate actions. However, empirical studies suggest that cognitive load can influence the strength of those cues. We formalise the relationship between salience and cognitive load revealed by empirical data. We add these rules to our abstract cognitive architecture, based on higher-order logic and developed for the formal verification of usability properties. The interface of a fire engine dispatch task from the empirical studies is then formally modelled and verified. The outcomes of this verification and their comparison with the empirical data provide a way of assessing our salience and load rules. They also guide further iterative refinements of these rules. Furthermore, the juxtaposition of the outcomes of formal analysis and empirical studies suggests new experimental hypotheses, thus providing input to researchers in cognitive science
Consequences of energy conservation in relativistic heavy-ion collisions
Complete characterization of particle production and emission in relativistic
heavy-ion collisions is in general not feasible experimentally. This work
demonstrates, however, that the availability of essentially complete
pseudorapidity distributions for charged particles allows for a reliable
estimate of the average transverse momenta and energy of emitted particles by
requiring energy conservation in the process. The results of such an analysis
for Au+Au collisions at sqrt{s_{NN}}= 130 and 200 GeV are compared with
measurements of mean-p_T and mean-E_T in regions where such measurements are
available. The mean-p_T dependence on pseudorapidity for Au+Au collisions at
130 and 200 GeV is given for different collision centralities.Comment: 8 pages, 8 figures, Submitted to Phys. Rev.
Geoneutrinos in Borexino
This paper describes the Borexino detector and the high-radiopurity studies
and tests that are integral part of the Borexino technology and development.
The application of Borexino to the detection and studies of geoneutrinos is
discussed.Comment: Conference: Neutrino Geophysics Honolulu, Hawaii December 14-16, 200
Observation of mixed anisotropy in the critical susceptibility of an ultrathin magnetic film
Measurements of the magnetic susceptibility of Fe/W(110) films with thickness
in the range of 1.6 to 2.4 ML Fe, show that in addition to the large response
along the easy axis associated with the Curie transition, there is a much
smaller, paramagnetic hard axis response that is not consistent with the 2D
anisotropic Heisenberg model used to describe homogeneous in-plane ferromagnets
with uniaxial anisotropy. The shape, amplitude, and peak temperature of the
hard axis susceptibility, as well as its dependence upon layer completion close
to 2.0 ML, indicate that inhomogeneities in the films create a system of mixed
anisotropy. A likely candidate for inhomogeneities that are magnetically
relevant in the critical region are the closed lines of step edges associated
with the incomplete layers. According to the Harris criterion, the existence of
magnetically relevant inhomogeneities may alter the critical properties of the
films from those of a 2D Ising model. Experiments in the recent literature are
discussed in this context.Comment: 9 two-column pages, 6 figures. This replacement has a new title and
abstract, and one additional figur
Overview of Solid Target Studies for a Neutrino Factory
The UK programme of high power target developments for a Neutrino Factory is centred on the study of high-Z materials (tungsten, tantalum). A description of lifetime shock tests on candidate materials is given as part of the research into a solid target solution. A fast high current pulse is applied to a thin wire of the sample material and the lifetime measured from the number of pulses before failure. These measurements are made at temperatures up to ~2000 K. The stress on the wire is calculated using the LS-DYNA code and compared to the stress expected in the real Neutrino Factory target. It has been found that tantalum is too weak to sustain prolonged stress at these temperatures but a tungsten wire has reached over 26 million pulses (equivalent to more than ten years of operation at the Neutrino Factory). An account is given of the optimisation of secondary pion production from the target and the issues related to mounting the target in the muon capture solenoid and target station are discussed
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