Measurement of global polarization of {\Lambda} hyperons in few-GeV heavy-ion collisions

The global polarization of {\Lambda} hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au collisions at \sqrt{s_{NN}} = 2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon transverse momentum (p_T) and rapidity (y_{CM}) for the range of centrality 0--40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20--40%) collisions the polarization magnitudes are (%) = 6.0 \pm 1.3 (stat.) \pm 2.0 (syst.) for Au+Au and (%) = 4.6 \pm 0.4 (stat.) \pm 0.5 (syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D fluid dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.Comment: 8 pages, 4 figure

Inclusive e+^+e−^- production in collisions of pions with protons and nuclei in the second resonance region of baryons

Inclusive e$^+$e$^-$ production has been studied with HADES in $\pi^-$ + p, $\pi^-$ + C and $\pi^- + \mathrm{CH}_2$ reactions, using the GSI pion beam at $\sqrt{s_{\pi p}}$ = 1.49 GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of $\pi^0$, $\eta$ mesons and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical point-like baryon with the production cross section constrained from the inverse $\gamma$ n$\rightarrow \pi^-$ p reaction. The enhancement is attributed to a strong four-momentum squared dependence of the time-like electromagnetic transition form factors as suggested by Vector Meson Dominance (VMD). Two versions of the VMD, that differ in the photon-baryon coupling, have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the $\rho$ meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the $\rho$ meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a time-like baryon transition form factor model where the pion cloud plays the major role.Comment: (HADES collaboration

Wielofunkcjonalność w kompozytach eutektycznych na osnowie multiferroicznej

The present work is dedicated to the functional description of eutectic composites containing rare earth ferrite - REFeO3. Materials that fall under this cathegory exhibit the spontaneous dielectric and magnetic polarization - they behave as ferroelectrics and ferromagnets and can be "tuned" by small additions of other rare earth elements without causing large crystal lattice distortions. Special attention was paid to multifunctionality that, in the majority of cases, comes from the control of the structural refinement with the supercooling of the crystallizing liquid.Niniejsza praca poświęcona jest opisowi funkcjonalności eutektycznych kompozytów na osnowie ferrytów metali ziem rzadkich - REFeO3. Materiały należące do tej grupy wykazują jednocześnie spontaniczną polaryzację dielektryczną (ferroelektryczność) i magnetyczną (ferromagnetyzm) a ponadto dają się "stroić" za pomocą domieszek innych metali ziem rzadkich nie powodując silnych zniekształceń sieci krystalicznej. Szczególną uwagę zwrócono na wielofunkcjonalność wynikającą w dużej mierze z możliwości sterowania rozdrobnieniem struktury za pomocą zmiany przechłodzenia krystalizującej cieczy

The effect of diesel fuel mixture and camelina oil ester on the process of fuel injection in traction engine

This paper presents the results of comparative research on basic physical and chemical properties of pure diesel fuel and two types’ mixtures of Camelina oil ester (Camelina oil ester content of the mixture was 10% and 15%) and diesel fuel. Application of these mixtures has different physicochemical properties to power supply diesel engine, made it possible to detect existing differences in the injection process (pumping and spraying). The analysis of the injection process has been defined through experimental graphs of the fuel pressure in injection line and registered height of the needle injector. With the knowledge of these two fast-changing engine parameters and loadvelocity conditions, there were calculated: fuel flow speed from nozzle, range and fuel spray disintegration time and the average critical diameter of the droplets. In the final part of the article it was shown, that the fuel with different physicochemical properties has a significant impact on the injection process. There were also made a comparative assessment of the suitability test compounds for use in service

Data for: Growth-microstructure relationship in MgO-MgAl2O4 eutectic fabricated by micro-pulling down method with MgAl2O4 seed crystals

Numerical results of the image analysis. Perpendicular cross-sections of directionally solidified MgO-MgAl2O4 eutectic were cut perpendicular to the growth direction and polished. Images, in the form of scannning electron microscopy micrographs were processed using ImageJ 1.52g

Data for: Growth-microstructure relationship in MgO-MgAl2O4 eutectic fabricated by micro-pulling down method with MgAl2O4 seed crystals

Numerical results of the image analysis. Perpendicular cross-sections of directionally solidified MgO-MgAl2O4 eutectic were cut perpendicular to the growth direction and polished. Images, in the form of scannning electron microscopy micrographs were processed using ImageJ 1.52g.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

The effect of alternative fuels injection timing on toxic substances formation in CI engines

The present study describes selected issues associated with the emission level in toxic exhaust gases and fuel injection timing. The study was focused on the following types of fuels: Diesel oil (the base fuel) and the other fuels were the mixture of fatty acid methyl ester with Camelina (L10 – diesel fuel with 10% V/V FAME of Camelina and L20 – diesel fuel with 10% V/V FAME of Camelina) was used. Fuel injection advanced angle was set for three different values – the factory setting – 12° before TDC, later injection – 7° and earlier injection – 17°. The most important conclusion is that in most measurement points registered in the same engine operating conditions, the concentration of fuel NOx in L10 and L20 increased but PM emissions decreased which is caused by active oxygen located in the internal structure of the fuel. This fact contributes to the rise in temperature during the combustion process. At the same time factory settings of the angle makes NOx emissions lower and close to reference fuel

Calculation Method for Assessing the Storage Capacity of Nitrogen Compounds in LNT Reactors

The presented study describes proprietary calculation methods that simulate the process of storing nitrogen dioxide elevation in a catalytic LNT reactor. The first section’s points of reference are the achievements of the article’s authors and the possibility of modeling NO2 adsorption processes in LNT reactors. The rest of the article presents model calculations (proposed by the authors) of the course of the NO2 storage process in LNT reactors. It considers one in its transition period, affecting the improvement and duration of the adsorption process. The conclusion presents selected results of simulation calculations obtained with the help of the equations’ authors and an evaluation of the results. A review of theoretical considerations is consistent with the experimental data, suggesting that the proposed computational solution may be used in future analytical validity assessments of LNT reactor tools under operating conditions