|
|
Study of production of jets and dijets in Xe+Xe and Pb+Pb collisions at the ATLAS experiment
Krivoš, Martin ; Spousta, Martin (advisor) ; Contreras Nuňo, Jesús Guillermo (referee) ; Křížek, Filip (referee)
A hot and dense medium is created during the heavy-ion collisions, affecting the strongly interacting particles forming jets. This typically leads to a suppression of jet production in heavy-ion collisions compared to jet production in proton-proton collisions. A study of this suppression in a dijet system, i.e., in a system of two back-to-back jets, can shed light on the details of the parton energy loss process responsible for this suppression. This thesis presents a measurement of dijet momentum balance in Xe+Xe collisions at √ sNN = 5.44 TeV as measured by the ATLAS experiment at the LHC. Results were compared with the previous measurement of dijet momentum balance in Pb+Pb collisions at √ sNN = 5.02 TeV. A significant momentum imbalance was observed in the most central Xe+Xe collisions, and this imbalance was decreasing with decreasing nuclear overlap. The ratio of a pair nuclear-modification factor further quantifies the differences between the dijet suppression in Xe+Xe and Pb+Pb collisions. The results are consistent with those measured in Pb+Pb data when compared in classes of the same event activity and when taking into account a difference between the center-of-mass energy of the initial parton scattering process in Xe+Xe and Pb+Pb collisions. These results provide new input for the understanding...
|
|
|
Study of charmonia production in proton-proton and heavy-ion collisions at the LHC
Krivoš, Martin ; Spousta, Martin (advisor) ; Řezníček, Pavel (referee)
In this thesis a production of J/ψ meson in pp and heavy-ion collisions was investigated. A comparison between Monte Carlo generator and data by ATLAS experiment at CERN was done. PYTHIA version 8.2 was chosen for the Monte Carlo generator. In the first part, comparisons of several configurations of PYTHIA were used to establish the best matching of the Monte Carlo to the data using collisions with centre-of-mass energy of 7 TeV. Choice of parton distribution functions was found not to be important, while presence or absence of initial and final state radiation were proven to have an important impact on the result. In the second part, correlation of J/ψ meson and the jet production was quantified. Anti-kt algorithm with R = 0.4 was used to reconstruct jets. Pairs of muons were used to identify J/ψ meson candidates. Only less than 10% of J/ψ mesons were found to be associated with jets. 1
|
|
|
Numerické modelování proudění vody v nitru ledových těles
Krivoš, Martin ; Čadek, Ondřej (advisor) ; Hanyk, Ladislav (referee)
Title: Numerical modeling of liquid water flows in ice bodies' interiors Author: Martin Krivoš Department: Department of Geophysics Supervisor: prof. RNDr. Ondřej Čadek, CSc., Department of Geophysics Abstract: We studied the flow induced by water jets in the subsurface oceans on the Solar system moons - Europa and Enceladus. In water plumes of Enceladus Cassini spacecraft detected small silica particles with radii ≈ 6 − 9 nm. As shown by experiments, these particles grow in size with time spent in the ocean. The small size of particles suggests that the material transport from the the jets on the oceanic floor to the source of the plume at the moon's surface is highly efficient. In the thesis we investigate the characteristic transport time by solving the Navier-Stokes equation for incompressible fluid. For this purpose we have developed a Fortran program in two-dimensional Cartesian geometry based on the finite-difference staggered-grid method. Another program, using the second order Runge-Kutta method, was written to reconstruct the trajectories of the particles in the ocean. Using these tools we estimated the effectiveness of material transport under different conditions, namely presence of global lateral flow, width of the water jet, the Reynolds number and the number of jets. Keywords: Navier-Stokes equation,...
|
guest ::
