Measurment of e+e- pairs in Au+Au collisions in PHENIX experiment

Visokoenergetski sudari teških iona pružaju mogućnost proučavanja svojstava vruće i guste nuklearne materije. U uvjetima ekstremne temperature i/ili gustoće kvarkovi i gluoni, inače vezani unutar hadrona, postaju slobodni i formiraju stanje materije koje nazovamo kvark-gluon plazmom. Elektronpozitron parovi, dielektroni, nastaju tijekom čitave prostorno-vremenske evolucije sudara, a budući da ne interagiraju jakim silama, nose informaciju o svojstvima materije u vremenu svoga nastavka. Ovaj se rad temelji na analizi e +e − parova iz Au+Au sudara na √ sNN = 62 GeV, prema podacima koji su prikupljeni tijekom 2010. godine u PHENIX eksperimentu na Relativistic Heavy Ion Collideru (RHIC). Za potrebe analize i korištenja informacija o vremenu proleta čestica u identifikaciji elektrona napravljena je kalibracija vremenskog odaziva Elektromagnetskog Kalorimetra. Prethodno analizi su iz PHENIX akceptancije uklonjena neaktivna i nefunkcionalna područja Driftne komore te je napravljena selekcija događaja na temelju kvalitete rekonstrukcije signala. Navedenim je postupkom osiguran konzistentan odaziv detektora koji su korišteni u analizi. Na temelju fizikalnog očekivanja odaziva čestica u detektorima napravljena je selekcija elektronskog uzorka te je procijenjen udio hadronske kontaminacije u uzorku (∼ 15%). Iz elektronskog uzorka su tada formirani e +e − parovi i promatran je spektar nakon oduzimanja pozadine. Diskutirani su opaženi doprinosi spektru invarijantne mase dielektrona te je dan pregled koraka koji bi sljedili kao nastavak analize iznesene u ovom radu.High-energy heavy ion collisions provide an opportunity to study the properties of the hot and dense nuclear matter. In the conditions of extreme temperature and/or density, quarks and gluons, normally confined inside hadronic matter, become deconfined and form a state of matter which we call the quark-gluon plasma. Electron-positron pairs, dielectrons, are created during the whole space-time evolution of the system. Since they don’t interact strongly and leave the medium without final state interactions, dielectrons carry information about the properties of matter at the time of their production. In this thesis the analysis of e+e- pairs from Au+Au collisions at √sNN = 62 GeV was presented, for data collected during 2010 in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). Prior to analysis, the Drift Chamber fiducal cuts were defined and the timing callibration of the Electromagnetic Calorimeter was done. The obtained time-of-flight information was used to define the mass squared variable of the particle, which was then sigmatized as a function of transverse momentum and used in electron identification (eID). After applying eID cuts on the trajectories from runs which have passed the QA (quality assurance) analysis, an electron sample was obtained, with an estimated hadronic background of 15%. Trajectories from the sample were used to form e+e- pairs. After background subtraction, the dielectron invariant mass spectrum was obtained and contributions to the spectrum were discussed. In conclusion, an overlook for the further analysis was given

Measurment of e+e- pairs in Au+Au collisions in PHENIX experiment

Visokoenergetski sudari teških iona pružaju mogućnost proučavanja svojstava vruće i guste nuklearne materije. U uvjetima ekstremne temperature i/ili gustoće kvarkovi i gluoni, inače vezani unutar hadrona, postaju slobodni i formiraju stanje materije koje nazovamo kvark-gluon plazmom. Elektronpozitron parovi, dielektroni, nastaju tijekom čitave prostorno-vremenske evolucije sudara, a budući da ne interagiraju jakim silama, nose informaciju o svojstvima materije u vremenu svoga nastavka. Ovaj se rad temelji na analizi e +e − parova iz Au+Au sudara na √ sNN = 62 GeV, prema podacima koji su prikupljeni tijekom 2010. godine u PHENIX eksperimentu na Relativistic Heavy Ion Collideru (RHIC). Za potrebe analize i korištenja informacija o vremenu proleta čestica u identifikaciji elektrona napravljena je kalibracija vremenskog odaziva Elektromagnetskog Kalorimetra. Prethodno analizi su iz PHENIX akceptancije uklonjena neaktivna i nefunkcionalna područja Driftne komore te je napravljena selekcija događaja na temelju kvalitete rekonstrukcije signala. Navedenim je postupkom osiguran konzistentan odaziv detektora koji su korišteni u analizi. Na temelju fizikalnog očekivanja odaziva čestica u detektorima napravljena je selekcija elektronskog uzorka te je procijenjen udio hadronske kontaminacije u uzorku (∼ 15%). Iz elektronskog uzorka su tada formirani e +e − parovi i promatran je spektar nakon oduzimanja pozadine. Diskutirani su opaženi doprinosi spektru invarijantne mase dielektrona te je dan pregled koraka koji bi sljedili kao nastavak analize iznesene u ovom radu.High-energy heavy ion collisions provide an opportunity to study the properties of the hot and dense nuclear matter. In the conditions of extreme temperature and/or density, quarks and gluons, normally confined inside hadronic matter, become deconfined and form a state of matter which we call the quark-gluon plasma. Electron-positron pairs, dielectrons, are created during the whole space-time evolution of the system. Since they don’t interact strongly and leave the medium without final state interactions, dielectrons carry information about the properties of matter at the time of their production. In this thesis the analysis of e+e- pairs from Au+Au collisions at √sNN = 62 GeV was presented, for data collected during 2010 in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). Prior to analysis, the Drift Chamber fiducal cuts were defined and the timing callibration of the Electromagnetic Calorimeter was done. The obtained time-of-flight information was used to define the mass squared variable of the particle, which was then sigmatized as a function of transverse momentum and used in electron identification (eID). After applying eID cuts on the trajectories from runs which have passed the QA (quality assurance) analysis, an electron sample was obtained, with an estimated hadronic background of 15%. Trajectories from the sample were used to form e+e- pairs. After background subtraction, the dielectron invariant mass spectrum was obtained and contributions to the spectrum were discussed. In conclusion, an overlook for the further analysis was given

Variability of carbon emission factors from lignite of the Kostolac basin in time

This paper presents experimental tests of lignite from the Kostolac open-pit mine, used to operate the boiler of the Kostolac B2 thermal power plant in 2022. Experimental tests were conducted to determine the emission characteristics and carbon emission factor and compare these values with those taken and determined in 2016. A total of 31 samples taken in April 2022 were tested. As with our previous work, the experimental methodology includes proximate analysis, ultimate analysis and determination of calorific value, for the 'as received', 'as determined' and dry basis. Corresponding correlations were established for the tested Kostolac lignite. The emission characteristics of the Kostolac lignite from 2022 were compared with the corresponding values from 2016. Certain changes in the values of the carbon emission factor over time are a regular phenomenon and therefore periodic sampling and experimental determinations are inevitable to follow the changes in the values. For this change in coal properties, new values for the carbon emission factor are proposed, which should be used to calculate the total carbon dioxide emissions in the last period

Determination of the drag coefficient of lattice structures under wind load using porous media approach

The power transmitters, guyed masts and other lattice structures are exposed to wind action. The aerodynamic forces acting on tall tower constructions have crucial importance on the stability of the structure. The lattice structure drag coefficient determination is the subject of the international standards ESDU 81027 and 81028 and Eurocode 3 Part 3.1, but it can also be determined by numerical methods. For that purpose modelling using CFD proved to be both accurate and reliable. In this study the fluid-flow around the segment of a power transmitter was simulated by a 3-D model, where the geometry of the segment is approximated with a porous structure having the appropriate factor of porosity, in order to simplify the geometry. We have used three representative models of turbulence, standard k-? model, RNG k-? model, and Reynolds stress model. Drag coefficient values are extracted from the flow field and compared for all studied cases and with available experimental results from the wind tunnel. Simulations were performed for four wind velocities between 10 m/s and 30 m/s. The results are supplemented by the ones obtained by artificial neural network. The aim of this study is to show how the simple turbulence model coupled with approximated geometry can be used in the analysis of the aerodynamic forces acting on the lattice structure

Multinucleon transfer reactions and proton transfer channels

Transfer reactions have always been of great importance for nuclear structure and reaction mechanism studies. So far, in multinucleon transfer studies, proton pickup channels have been completely identified in atomic and mass numbers at energies close to the Coulomb barrier only in few cases. We measured the multinucleon transfer reactions in the 40Ar+208Pb system near the Coulomb barrier, by employing the PRISMA magnetic spectrometer. By using the most neutron-rich stable 40Ar beam we could populate, besidesneutron pickup and proton stripping channels, also neutron stripping and proton pickup channels. Comparison ofcross sections between different systems with the 208Pb target and with projectiles going from neutron-poor to neutron-rich nuclei, as well as between the data and GRAZING calculations, was carried out.Finally, recent results concerning the measurement of the excitation function from the Coulomb barrier to far below for the 92Mo+54Fe system, where both proton stripping and pickup channels were populated with similar strength, will be discussed

Effects of Non-Zero Spin in Sub-Barrier Fusion Involving Odd Mass Nuclei: The Case of 36S + 50Ti, 51V

International audience; A detailed comparative study of the sub-barrier fusion of the two near-by systems ^36S + ^50Ti, ^51V was performed at the National Laboratories of Legnaro (INFN). We aimed to investigate the possible effect of the non-zero spin of the ground state of the ^51V nucleus on the sub-barrier excitation function, and in particular on the shape of the barrier distribution. The comparison of the exctiation functions and barrier distributions highlighted a very similar behavior, down to the level of 20–30 µb. Coupled-channels calculations have been performed including the low energy excitations of both projectile and targets and the results are in very good agreement with the data. This indicates that the low-lying levels in ^51V can be interpreted in the weak-coupling scheme and that the extra proton in the f_7/2 shell does not have a significant influence on sub-barrier fusion

Klasterska građa neutronski bogatih lakih jezgara proizvedenih u reakcijama snopa 9Li na meti LiF

The results presented in this thesis are based on the analysis of the S1620 experiment performed at TRIUMF, where multi-nucleon and cluster transfer reactions of the 9^Li beam of 74.8 MeV on the ≈ 1 mg/cm2 LiF target were used to populate excited states of neutron-rich light nuclei 10^Be, 12^Be and 13^B. The main motivation behind this work was the need for experimental data to wage on the existence of molecular-like structures in the excited states of these nuclei and to resolve inconsistent observations from the previous measurements. For the latter two nuclei, the use of transfer reactions and resonant particle spectroscopy method to study molecular structures is independent and novel approach to more commonly used resonant elastic scattering and inelastic breakup measurements. Most important results are the first experimental observation of the decays of the 12^Be excited states to the 6^He+6^He* (1.8 MeV, 2^+) channel and the 13^B decays to the 10^Be+3^H and 7^Li+6^He channels. In the 10^Be nucleus, new states were observed in the 8^Be+nn decay channel and past results for the 4^He+6^He* (1.8 MeV, 2^+) channel were confirmed, alongside newly observed states. In both cases only one previous measurement was available. New states were observed in the 4^He+6^He, 4,6^He+8,6^He and 9^Li+4^He decay channels of the 10^Be, 12^Be and 13^B nuclei, respectively. Even though branching ratios were not determined, due to limited resolution of the present data, important spectroscopic information on the cluster structures in these nuclei was obtained, which could be related to the molecular α-Xn- α and α-2n-t-α structure of the 10,12^Be and 13^B nuclei, respectively.Rad ne sadrži sažetak na drugom jeziku

Klasterska građa neutronski bogatih lakih jezgara proizvedenih u reakcijama snopa 9Li na meti LiF

The results presented in this thesis are based on the analysis of the S1620 experiment performed at TRIUMF, where multi-nucleon and cluster transfer reactions of the 9^Li beam of 74.8 MeV on the ≈ 1 mg/cm2 LiF target were used to populate excited states of neutron-rich light nuclei 10^Be, 12^Be and 13^B. The main motivation behind this work was the need for experimental data to wage on the existence of molecular-like structures in the excited states of these nuclei and to resolve inconsistent observations from the previous measurements. For the latter two nuclei, the use of transfer reactions and resonant particle spectroscopy method to study molecular structures is independent and novel approach to more commonly used resonant elastic scattering and inelastic breakup measurements. Most important results are the first experimental observation of the decays of the 12^Be excited states to the 6^He+6^He* (1.8 MeV, 2^+) channel and the 13^B decays to the 10^Be+3^H and 7^Li+6^He channels. In the 10^Be nucleus, new states were observed in the 8^Be+nn decay channel and past results for the 4^He+6^He* (1.8 MeV, 2^+) channel were confirmed, alongside newly observed states. In both cases only one previous measurement was available. New states were observed in the 4^He+6^He, 4,6^He+8,6^He and 9^Li+4^He decay channels of the 10^Be, 12^Be and 13^B nuclei, respectively. Even though branching ratios were not determined, due to limited resolution of the present data, important spectroscopic information on the cluster structures in these nuclei was obtained, which could be related to the molecular α-Xn- α and α-2n-t-α structure of the 10,12^Be and 13^B nuclei, respectively.Rad ne sadrži sažetak na drugom jeziku