3,231 research outputs found
Average formation length in string model
The space-time scales of the hadronization process in the framework of string
model are investigated. It is shown that the average formation lengths of
pseudoscalar mesons, produced in semi-inclusive deep inelastic scattering (DIS)
of leptons on different targets, depend from their electrical charges. In
particular the average formation lengths of positively charged hadrons are
larger than of negatively charged ones. This statement is fulfiled for all
using scaling functions, for (the fraction of the virtual photon energy
transferred to the detected hadron) larger than 0.15, for all nuclear targets
and any value of the Bjorken scaling variable . In all cases, the main
mechanism is direct production of pseudoscalar mesons. Including in
consideration additional mechanism of production in result of decay of
resonances, leads to decrease of average formation lengths. It is shown that
the average formation lengths of positively (negatively) charged mesons are
slowly rising (decreasing) functions of . The obtained results can be
important, in particular, for the understanding of the hadronization process in
nuclear environment
Average formation lengths of baryons and antibaryons in string model
In this work it is continued the investigation of the space-time scales of
the hadronization process in the framework of string model. The average
formation lengths of several widely using species of baryons (antibaryons) such
as (), (), (),
() and () are studied. It is shown that
they depend from electrical charges or, more precise, from quark contents of
the hadrons. In particular, the average formation lengths of positively charged
hadrons, for example protons, are considerably larger than of their negatively
charged antiparticles, antiprotons. This statement is fulfilled for all nuclear
targets and any value of the Bjorken scaling variable . The main
mechanism is direct production. Additional production mechanism in result of
decay of resonances gives small contribution. It is shown that the average
formation lengths of protons (antiprotons) are slowly rising (decreasing)
functions of , the ones of neutrons and antineutrons are slowly
decreasing functions of . The shape and behavior of average formation
lengths for baryons qualitatively coincide with the ones for pseudoscalar
mesons obtained earlier.Comment: 7 pages, 6 figure
Dynamical spin-spin coupling of quantum dots
We carried out a nested Schrieffer-Wolff transformation of an Anderson
two-impurity Hamiltonian to study the spin-spin coupling between two dynamical
quantum dots under the influence of rotating transverse magnetic field. As a
result of the rotating field, we predict a novel Ising type spin-spin coupling
mechanism between quantum dots, whose strength is tunable via the magnitude of
the rotating field. The strength of the new coupling could be comparable to the
strength of the RKKY coupling. The dynamical coupling with the intristic RKKY
coupling enables to construct a four level system of maximally entangled Bell
states in a controllable manner
Nuclear attenuation of high energy multi-hadron systems in the string model
Nuclear attenuation of the multi-hadron systems in the string model is
considered. The improved two-scale model with set of parameters obtained
recently for the single hadron attenuation is used for calculation of the
multiplicity ratios of the one-, two- and three-hadron systems electroproduced
on nuclear and deuterium targets. The comparison of the features of the one-,
two- and three-hadron systems is performed. The predictions of the model for
multiplicity ratios of multi-hadron systems as functions of different
convenient variables are presented.Comment: 7 pages, 6 figure
Simple parameterization of nuclear attenuation data
Based on the nuclear attenuation data obtained by the HERMES experiment on
nitrogen and krypton nuclei, it is shown that the nuclear attenuation
can be parametrised in a form of a linear polynomial + , where is the formation time, which depends on the energy of the
virtual photon and fraction of that energy carried by the final
hadron. Three widely known parameterizations for were used for the
performed fit. The fit parameters and do not depend on
and
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