24,083 research outputs found
Collective and fractal properties of pion jets in the four-velocity space at intermediate energies
Experimental results are presented for study of collective and fractal
properties of soft pion jets in the space of relative four-dimensional
velocities. Significant decreasing is obtained for mean square of second
particle distances from jet axis for pion-proton interactions at initial
energies GeV in comparison with hadron-nuclear collisions at close
energies. The decreasing results in power dependence of distance variable on
collision energy for range GeV. The observation allows us to
estimate the low boundary of manifestation of color degree of freedom in pion
jet production. Cluster dimension values were deduced for pion jets in various
reactions. Fractional values of this dimension indicate on the manifestation of
fractal-like properties by pion jets. Changing of mean kinetic energy of jet
particles and fractal dimension with initial energy increasing is consistent
with suggestion for presence of color degrees of freedom in pion jet production
at intermediate energies.Comment: The conference "Physics of fundamental interactions". ITEP, Moscow,
Russia. November 23 - 27, 200
Mechanism of single-spin asymmetries generation in the inclusive hadron processes
We discuss a nonperturbative mechanism for generation of the single-spin
asymmetries in hadron interactions. It is based on the chiral quark model
combined with unitarity and impact parameter picture and provides explanation
for the experimental regularities observed under the measurements of the spin
asymmetries.Comment: 20 pages, 7 figure
Thermodynamics and kinetics of solids fragmentation at severe plastic deformation
The approach of nonequilibrium evolution thermodynamics earlier offered is
developed. It helps to describe the processes of defect formation within the
adiabatic approximation. The basic equations system depends on the initial
defects distribution (dislocations and grain boundaries). The phase diagram is
determined with the domains of the realization of different limiting structure
types. The interaction effect of several defect types on the formation of a
limiting structure is investigated in terms of the internal energy. The
conditions of the formation of two limiting structures are found. The kinetics
of the steady-state values establishment of the defects density is investigated
within the scope of the adiabatic approximation. The dislocations density
change follows the evolution of the grain boundaries density in this approach.
It is shown that grain sizes, in limiting structures, decrease with an increase
of the elastic strains.Comment: 14 pages, 6 figure
Enhanced flux pinning isotropy by tuned nanosized defect network in superconducting YBa2Cu3O6+x films
Striving to improve the critical current density Jc of superconductingYBa(2)Cu(3)O(6+x) (YBCO) thin films via enhanced vortex pinning, the interplay between film growth mechanisms and the formation of nanosized defects, both natural and artificial, is systematically studied in undoped and BaZrO3 (BZO)-doped YBCO thin films. The films were grown via pulsed laser deposition (PLD), varying the crystal grain size of the targets in addition to the dopant content. The microstructure of the PLD target has been observed to have a great impact on that of the deposited thin films, including the formation of vortex pinning centers, which has direct implications on the superconducting performance, especially on the isotropy of flux pinning properties. Based on experimentally measured angular dependencies of Jc, coupled with a molecular dynamics (MD) simulation of flux pinning in the YBCO films, we present a quantitative model of how the splay and fragmentation of BZO nanorods artifically introduced into the YBCO film matrix explain the majority of the observed critical current anisotropy
Chiral-odd distribution functions in the chiral quark soliton model
The recent measurements of azimuthal single spin asymmetries by the HERMES
collaboration has opened up new possibility to measure chiral-odd distribution
functions through semi-inclusive deep-inelastic scatterings. Here, predictions
are given for the twist-2 and twist-3 chiral-odd distribution functions of the
nucleon within the framework of the chiral quark soliton model, with full
inclusion of the vacuum polarization effects as well as the subleading
corrections. The importance of the vacuum polarization effects is demonstrated
by showing that the so-called Soffer inequality holds not only for the quark
distributions but also for the antiquark ones.Comment: 12 pages, latex, 5 eps_fi
Fragmentation pathways of nanofractal structures on surface
We present a detailed systematical theoretical analysis of the post-growth
processes occurring in nanofractals grown on surface. For this study we
developed a method which accounts for the internal dynamics of particles in a
fractal. We demonstrate that particle diffusion and detachment controls the
shape of the emerging stable islands on surface. We consider different
scenarios of fractal post-growth relaxation and analyze the time evolution of
the island's morphology. The results of our calculations are compared with
available experimental observations, and experiments in which the post-growth
relaxation of deposited nanostructures can be probed are suggested.Comment: 34 pages, 11 figure
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