Four-pion production in tau decays and e+e- annihilation: an update

An improved description of four-pion production in electron-positron annihilation and in tau lepton decays is presented. The model amplitude is fitted to recent data from BaBar which cover a wide energy range and which were obtained exploiting the radiative return. Predicting tau decay distributions from e+e- data and comparing these predictions with ALEPH and CLEO results, the validity of isospin symmetry is confirmed within the present experimental errors. A good description of two- and three-pion sub-distributions is obtained. Special emphasis is put on the predictions for omega pi (-> pi+pi-pi0) in e+e- annihilation and in tau decay. The model amplitude is implemented in the Monte Carlo generator PHOKHARA.Comment: a few typos correcte

How to Measure Chromo-magnetic Vacuum Background Field in e+e−→jetse^{+}e^{-}\to jets, Hadron-Hadron and Nucleus-Nucleus Collisions

We propose a new type of the measurement which is sensitive to the QCD vacuum color-magnetic fluctuations: A measure of the axial assymetry of the hadronic final states produced in the high energy $e^{+}e^{-}$ collisions is related to the chromomagnetic vacuum field strength.Comment: 11 pages,latex,no figures,replaced,final version which takes into account criticisms of referees of Phys.Rev. Title of the paper was changed. The formula (14) was corrected, notation in formulae (12) and (13) changed. Also we added forgotten vectorial notations,corrected misspellings and improved the style and gramma

Coherent particle production in collisions of relativistic nuclei

Here we give the results of our study of features of dense groups, or spikes, of particles produced in Mg-Mg and C-Cu collisions at, respectively, 4.3 and 4.5 GeV/c/nucleon aimed to search for a coherent, Cerenkov-like, mechanism of hadroproduction. We investigate the distributions of spike centers and, for Mg-Mg interactions, the energy spectra of negatively charged particles in spikes. The spike-center distributions are obtained to exhibit the structure expected from coherent gluon-jet emission dynamics. This structure is similar in both cases considered, namely for all charged and negatively charged particles, and is also similar to that observed recently for all-charged-particle spikes in hadronic interactions. The energy distribution within spikes is found to have a significant peak over the inclusive background, while the inclusive spectrum shows exponential decrease with two characteristic values of average kinetic energy. The value of the peak energy and its width are in a good agreement with those expected for pions produced in a nuclear medium in the framework of the Cerenkov quantum approach. The peak energy obtained is consistent with the value of the cross-section maximum observed in coincidence nucleon-nucleus interaction experiments.Comment: 8 pages, 5 figures. Invited talk presented by E.S. at the 9th International Workshop on Multiparticle Production: New Frontiers in Soft Physics and Correlations on the Threshold of the Third Millenium, Turin, Italy, June 12 - 17, 200

Superscaling in dilute Fermi gas and its relation to general properties of the nucleon momentum distribution in nuclei

The superscaling observed in inclusive electron scattering is described within the dilute Fermi gas model with interaction between the particles. The comparison with the relativistic Fermi gas (RFG) model without interaction shows an improvement in the explanation of the scaling function $f(\psi ')$ in the region $\psi ' < -1$, where the RFG result is $f(\psi ') = 0$. It is found that the behavior of $f(\psi ')$ for $\psi ' < -1$ depends on the particular form of the general power-law asymptotics of the momentum distribution $n(k)\sim 1/ k^{4+m}$ at large $k$. The best agreement with the empirical scaling function is found for $m\simeq 4.5$ in agreement with the asymptotics of $n(k)$ in the coherent density fluctuation model where $m = 4$. Thus, superscaling gives information about the asymptotics of $n(k)$ and the NN forces.Comment: 6 pages, 5 figures, accepted for publication in Physical Review

The influence of zinc-methionine bioplex supplementation to pregnant and lactating sheep on selected wool parameters

The most important nutrients affecting wool production include sulfur amino acids, such as methionine, and minerals, such as zinc, and their deficiency may cause wool production decrease. The aim of this study was to evaluate an effect of zinc and methionine chelate addition on the qualitative characteristics of Merino ewes wool and zinc content in wool fibers and on their surface. Histological evaluation of fibers was also performed. The study included 22 Polish Merino ewes divided into two groups: control and experimental (0.4&thinsp;g chelates daily per head). The experiment lasted for 4 months (3.5 months of pregnancy and 2 weeks of early lactation). The length, thickness and breaking force of wool fibers were higher in the experimental group compared to the control group. Higher content of zinc in wool of sheep from the experimental group was also demonstrated. The histological structure of fibers from both groups did not differ, as the content of zinc on their surface. It can be concluded on the basis of the obtained results that the addition of chelates favorably influenced the thickness compensation of wool fibers and amount of wool obtained from sheep during pregnancy and early lactation, as well as mechanical features of wool.</p

Calculations of 6^{6}He+p elastic scattering cross sections using folding approach and high-energy approximation for the optical potential

Calculations of microscopic optical potentials (OP's) (their real and imaginary parts) are performed to analyze the $^6$He+p elastic scattering data at a few tens of MeV/nucleon (MeV/N). The OP's and the cross sections are calculated using three model densities of $^6$He. Effects of the regularization of the NN forces and their dependence on nuclear density are investigated. Also, the role of the spin-orbit terms and of the non-linearity in the calculations of the OP's, as well as effects of their renormalization are studied. The sensitivity of the cross sections to the nuclear densities was tested and one of them that gives a better agreement with the data was chosen.Comment: 13 pages, 11 figures, to be published in Eur. Phys. J.

Determination of Matter Surface Distribution of Neutron-rich Nuclei

We demonstrate that the matter density distribution in the surface region is determined well by the use of the relatively low-intensity beams that become available at the upcoming radioactive beam facilities. Following the method used in the analyses of electron scattering, we examine how well the density distribution is determined in a model-independent way by generating pseudo data and by carefully applying statistical and systematic error analyses. We also study how the determination becomes deteriorated in the central region of the density, as the quality of data decreases. Determination of the density distributions of neutron-rich nuclei is performed by fixing parameters in the basis functions to the neighboring stable nuclei. The procedure allows that the knowledge of the density distributions of stable nuclei assists to strengthen the determination of their unstable isotopes.Comment: 41 pages, latex, 27 figure