Evolution of Baryon-Free Matter Produced in Relativistic Heavy-Ion Collisions

A 3-fluid hydrodynamic model is introduced for simulating heavy-ion collisions at incident energies between few and about 200 AGeV. In addition to the two baryon-rich fluids of 2-fluid models, the new model incorporates a third, baryon-free (i.e. with zero net baryonic charge) fluid which is created in the mid-rapidity region. Its evolution is delayed due to a formation time $\tau$, during which the baryon-free fluid neither thermalizes nor interacts with the baryon-rich fluids. After formation it thermalizes and starts to interact with the baryon-rich fluids. It is found that for $\tau$=0 the interaction strongly affects the baryon-free fluid. However, at reasonable finite formation time, $\tau$=1 fm/c, the effect of this interaction turns out to be substantially reduced although still noticeable. Baryonic observables are only slightly affected by the interaction with the baryon-free fluid.Comment: 17 pages, 3 figures, submitted to the issue of Phys. of Atomic Nuclei dedicated to S.T. Belyaev on the occasion of his 80th birthday, typos correcte

Chemical Freeze-out of Strange Particles and Possible Root of Strangeness Suppression

Two approaches to treat the chemical freeze-out of strange particles in hadron resonance gas model are analyzed. The first one employs their non-equillibration via the usual \gamma_s factor and such a model describes the hadron multiplicities measured in nucleus-nucleus collisions at AGS, SPS and RHIC energies with \chi^2/dof = 1.15. Surprisingly, at low energies we find not the strangeness suppression, but its enhancement. Also we suggest an alternative approach to treat the strange particle freeze-out separately, but with the full chemical equilibration. This approach is based on the conservation laws which allow us to connect the freeze-outs of strange and non-strange hadrons. Within the suggested approach the same set of hadron multiplicities can be described better than within the conventional approach with \chi^2/dof = 1.06. Remarkably, the fully equilibrated approach describes the strange hyperons and antihyperons much better than the conventional one.Comment: 6 pages, 5 figure

Quark Model and Neutral Strange Secondary Production by Neutrino and Antineutrino Beams

The experimental data on $K^0$ and $\Lambda$ production by $\nu$ and $\bar{\nu}$ beams are compared with the predictions of quark model assuming that the direct production of secondaries dominates. Disagreement of these predictions with the data allows one to suppose that there exists considerable resonance decay contribution to the multiplicities of produced secondaries.Comment: 6 pages, no figures, 2 table

[Ways to improve the productivity of chickens using a feed additives based on shungite as an example] Пути повышения продуктивных показателей кур (на примере использования кормовой добавки на основе шунгита)

To increase the efficiency of poultry production, new technologies for keeping and feeding are being developed. At the same time, it is urgent to search for new types of feed and feed additives that stimulate the functional state of young animals and adults. The experiment evaluated efficacy of the Sirtila® and Mustala® mineral additives based on shungite and neutralizing mycotoxins in feeding layers. The potential of the feed additives to maintain and increase productivity, improve feed conversion, in the absence of a negative effect on metabolism, has been shown. Для увеличения эффективности птицеводства разрабатываются новые технологии содержания и кормления. При этом актуальным является поиск новых видов кормов и кормовых добавок, стимулирующих функциональное состояние молодняка и взрослого поголовья. В опыте оценивалась эффективность минеральных добавок «Сиртила®» и «Мустала®» на основе шунгита в качестве нейтрализаторов микотоксинов в кормлении яичных кур. Показан потенциал кормовых добавок к поддержанию и повышению продуктивности, улучшению конверсии корма, при отсутствии отрицательного влияния на метаболизм

Properties of the jet in M87 revealed by its helical structure imaged with the VLBA at 8 and 15 GHz

We present full-track high-resolution radio observations of the jet of the galaxy M87 at 8 and 15 GHz. These observations were taken over three consecutive days in May 2009 using the Very Long Baseline Array (VLBA), one antenna of the Very Large Array (VLA), and the Effelsberg 100 m telescope. Our produced images have dynamic ranges exceeding 20,000:1 and resolve linear scales down to approximately 100 Schwarzschild radii, revealing a limb-brightened jet and a faint, steep spectrum counter-jet. We performed jet-to-counter-jet analysis, which helped estimate the physical parameters of the flow. The rich internal structure of the jet is dominated by three helical threads, likely produced by the Kelvin-Helmholtz (KH) instability developing in a supersonic flow with a Mach number of approximately 20 and an enthalpy ratio of around 0.3. We produce a CLEAN imaging bias-corrected 8-15GHz spectral index image, which shows spectrum flattening in regions of helical thread intersections. This further supports the KH origin of the observed internal structure of the jet. We detect polarised emission in the jet at distances of approximately 20 milliarcseconds from the core and find Faraday rotation which follows a transverse gradient across the jet. We apply Faraday rotation correction to the polarisation position angle and find that the position angle changes as a function of distance from the jet axis, which suggests the presence of a helical magnetic field.Comment: 15 pages, 10 figures, 1 table, Submitted to MNRAS on 25th March 202

Radiative decays of quarkonium states, momentum operator expansion and nilpotent operators

We present the method of calculation of radiative decays of composite quark-antiquark systems with different J^{PC}: (Q\bar Q)_{in} -> gamma (Q\bar Q)_{out}. The method is relativistic invariant, it is based on the double dispersion relation integrals over the masses of composite mesons, it can be used for the high spin particles and provides us with the gauge invariant transition amplitudes. We apply this method to the case when the photon is emitted by a constituent in the intermediate state (additive quark model). We perform the momentum operator expansion of the spin amplitudes for the decay processes. The problem of nilpotent spin operators is discussed.Comment: 21 pages, 1 figur

The study of the proton-proton collisions at the beam momentum 1628 MeV/c

The detailed investigation of the single pion production reactions $pp\to pn\pi^{+}$ and $pp\to pp\pi^{o}$ at the incident proton momentum 1628 MeV/c has been carried out. The data are analyzed in the framework of the event-by-event maximum likelihood method together with the $pp\to pp\pi^{0}$ data measured earlier in the energy region below 1 GeV. At 1628 MeV/c the largest contributions stem from the $^{3}P_{2}$, $^{3}P_{1}$, $^{3}P_{0}$, $^{1}D_{2}$ and $^{3}F_{2}$ initial partial waves.Comment: 7 pages, 9 figure