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 $z$ (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 $x_{Bj}$. 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 $x_{Bj}$. 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 $p$ ($\bar{p}$), $n$ ($\bar{n}$), $\Delta$ ($\bar{\Delta}$), $\Lambda$ ($\bar{\Lambda}$) and $\Sigma$ ($\bar{\Sigma}$) 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 $x_{Bj}$. 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 $x_{Bj}$, the ones of neutrons and antineutrons are slowly decreasing functions of $x_{Bj}$. 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 $R_M^{h}$ can be parametrised in a form of a linear polynomial $P_1=a_{11}$ + $\tau a_{12}$, where $\tau$ is the formation time, which depends on the energy of the virtual photon $\nu$ and fraction of that energy $z$ carried by the final hadron. Three widely known parameterizations for $\tau$ were used for the performed fit. The fit parameters $a_{11}$ and $a_{12}$ do not depend on $\nu$ and $z$