Abstract: Events that started with very similar initial conditions should also evolve similarly and produce similar single-particle distributions of hadrons. This is natural consequence of hydrodynamic description of a collision. We present a novel method for data analysis. It compares the histograms of azimuthal hadron distributions from each event and organizes the events in such a way that those with similar histograms end-up placed close to each other. Those are the ones which underwent similar evolution. Such events can more easily be compared to theoretical simulations where all conditions can be controlled. We illustrate the method on data simulated by the AMPT model. Finally, we speculate about other possible applications of the method.
Posters
Posters presented by our students and researchers at conferences.
D meson production in Au+Au collisions at 200 GeV measured by the STAR experiment
Author: Jakub Kvapil (student - EJČF)
Conference: Quark Matter 2017
53rd Karpacz Winter School of Theoretical Physics
Date and location: 5. 2. - 11. 2. 2017, Chicago, USA
26. 2. - 4. 3. 2017, Karpacz, Poland
Award: Best experimental poster at 53rd Karpacz Winter School of Theoretical Physics
Abstract: Charm quarks are mainly created in hard processes at the beginning of heavy-ion collisions and can be used as a tool to study properties of the Quark-Gluon Plasma (QGP). The modification to D-meson production in heavy-ion collisions is sensitive to the energy loss of charm quarks in the QGP. The Heavy Flavor Tracker was installed at the STAR experiment in 2014 and enables the topological reconstruction of the decay vertices for open charm mesons. It significantly improves precision on charm meson measurements. Besides the measurement of D0, D± provides an additional handle and cross-check to study the interaction between charm quarks and the medium. In this poster, we present measurements of D± production in Au+Au collisions at 200 GeV. D± mesons are reconstructed topologically via the hadronic decay channel D± → K∓ π± π± from the data collected in 2014 with the Heavy Flavor Tracker. The invariant yield of D± mesons in the transverse momentum range of 2 - 10 GeV/c is extracted for 0 - 10% most central Au+Au collisions, and is found to be consistent with the D0 yield.
ALICE Measurements on ρ Photoproduction in Pb-Pb Ultra-peripheral Collisions
Author: David Horák (student - EJČF)
Conference: Quark Matter 2017
53rd Karpacz Winter School of Theoretical Physics
Date and location: 5. 2. - 11. 2. 2017, Chicago, USA
26. 2. - 4. 3. 2017, Karpacz, Poland
Abstract: The powerful photon fluxes of relativistic nuclei provide a possibility to study photonuclear and two-photon interactions in ultra-peripheral collisions where the nuclei do not overlap and no strong nuclear interactions occur. ALICE reports measurements on ρ^0 photoproduction cross sections in Pb-Pb UPC with data taken at √sNN = 2.76 TeV and new measurements with data taken at √sNN = 5.02 TeV. The mid-rapidity cross section of coherent ρ0 photoproduction is measured, and it is compared to theoretical models.
How to select events which evolved similarly?
Author: Boris Tomášik (EJČF), Renata Kopečná (student - EJČF)
Conference: Quark Matter 2017
Date and location: 5. 2. - 11. 2. 2017, Chicago, USA
Performance of the ALICE secondary vertex b-tagging algorithm
Authors: Gyulnara Eyyubova (postdok - EJČF), Lukáš Kramárik (student - EJČF)
Conference: International Conference on New Frontiers in Physics 2015 (ICNFP 2015)
54th International Winter Meeting on Nuclear Physics
Date and location: 24. 8. - 30. 8. 2015, Kolymbari, Creee, Greece
25. 1. - 29. 1. 2016, Bormio, Italy
Award: Best poster at ICNFP 2015 award
Abstract: Jet reconstruction provides access to the kinematics of partons produced in the initial stage of heavy-ion collisions that later suffer energy loss in the medium via gluon radiation and elastic collisions. Reconstructed jets are therefore powerful tools to study the properties of the quark-gluon plasma (QGP). Theoretical models predict a dependence of the energy loss in the QGP on color charge and mass of the parton. Thus, the study of properties of beauty jets in comparison with that of light-flavour jets can reveal important information about the matter formed. b-tagging algorithms rely on the properties of B hadrons, i.e. their long lifetime, large mass and large multiplicity of decay products. In this poster the b-tagging algorithm based on secondary-vertex reconstruction is described. We present Monte Carlo based performance studies of the algorithm for charged jets reconstructed with ALICE tracking system. The tagging efficiency, rejection rate and the correction of the smearing effects of non-ideal detector response are presented. Finally, the performance expected for LHC Run 2 is briefly discussed.