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