Title: Analysis of J/Psi + photon production in proton-proton collisions on ATLAS at LHC Author: Bc. Zuzana Vidláková Department: Institute of particle and nuclear physics Supervisor: prom. fyz. Václav Vrba, CSc. (Academy of Sciences of the Czech Republic) Abstract: The subject of this thesis is physics connected to quarkonia and their studies at the ATLAS detector situated at LHC in CERN, Geneva. In this thesis, following topics are cov- ered: ATLAS detector, history of physics connected to quarkonia, production mechanisms of quarkonia, software used at CERN for data analysis and cross-section measurement of J/Psi + photon continuum. The analysis was done on behalf of the B-physics working group at ATLAS. Keywords: CERN, LHC, ATLAS, B-fyzika, quarkonia

In the presented diploma thesis we study the reconstruction of the top antitop system in proton-proton colisions with central mass energy 7 TeV de- livered by LHC accelerator at CERN to the ATLAS experiment. ALPGEN and MC@NLO generators are described as two main method of top antitop pairs simulations. We compare events simulated by generators to data from LHC. The background and selection criteria are summarized. Next we de- scribed various methods of the top antitop reconstruction. Finally the Z particle was also studied. 1

This thesis presents the measurement of the differential cross section of the top-antitop pair production in proton-proton collisions at center-of-mass energy of 8 TeV at the ATLAS experiment. The measurement is performed for top-antitop events in the single lepton decay channel in the boosted topol- ogy. The measured differential cross section is expressed as a function of the top quark transverse momentum at particle level and at parton level. The mea- sured distributions are compatible with the theoretical predictions of the Standard Model. The experimental techniques used in this measurement are discussed with emphasis on the jet reconstruction and on the identification of jets originating from b-quark fragmentation. The jet reconstruction is influenced by simultane- ous proton-proton collisions (pileup), and the mitigation of these pileup effects is studied. A novel pileup subtraction technique for jets is proposed using an ex- tension of the methods currently being employed by the LHC experiments. The new method has a good performance in removing the pileup contributions at the level of jet constituents. 1

Title: Measurement of the top quark properties Author: Mgr. Jaroslava Schovancová Department: Institute of Physics, Academy of Sciences of the Czech Re- public Supervisor: RNDr. Jiří Chudoba, Ph.D., Institute of Physics, Academy of Sciences of the Czech Republic Abstract: This Thesis presents the ATLAS experiment measurement of the top quark differential cross-section as a function of pT, mass and rapidity of the t¯t system. A sample of approx. 4.7 fb−1 of the 2011 pp collision data at the center-of-mass energy of 7 TeV was analyzed. The differential spectra shapes in the t¯t system are consistent with the Standard Model and reason- ably described by the event generators. Several activities in the scope of ATLAS Distributed Computing are pre- sented, particularly in the area of operations, monitoring, automation, and development of the PanDA Workload Management System. Such activities aim to improve efficiency and facilitate the use of distributed computing re- sources and therefore contribute in supporting the ATLAS Physics Program. Keywords: ATLAS, top quark, differential cross-section, missing transverse energy, ATLAS Distributed Computing

Only a small part of particle physics is mentioned in the physics courses for Swedish high school students, despite the fact that particle physics is a field where a lot of research and progress are being done today. The first two physics courses in Swedish high schools include an overview of the standard model and the particles and interactions within the model. By designing an experiment where students get to use data from the ATLAS experiment in CERN they not only get to learn more about particle physics, they also get the opportunity to learn how to work similar to how researchers work in this field. This project was inspired by the Hands-on-CERN project which is focusing on increasing high school students interest and understanding of particle physics. By imitating Hands-on-CERN’s way of working, an experiment for high school students has been designed. In the experiment students get to discover the existence of quarks, even though they can not be observed as free particles but only in bounded states; so called hadrons. By analyzing data from the ATLAS experiment of the decay of the Z boson, you get to the conclusion that the Z boson more often decay to hadrons than to leptons with a proportion of about 14:71. This proportion depends on the various possibilities of hadrons that the Z boson can decay to, depending on the inner structure of hadrons consisting of quarks, dissimilar to the leptons which have no inner structure. / I fysikkurserna på gymnasiet ingår endast en liten del av partikelfysiken, trots att det är ett område som är väldigt aktuell inom forskning. I Fysik 1 och 2 ingår en översiktlig orientering om standardmodellen och de partiklar och interaktioner som ingår i modellen. Genom att utforma en laboration där eleverna får använda sig av data från ATLAS-experimentet på CERN får de både möjligheten att lära sig mer om partikelfysik och prova att arbeta på ett sätt som liknar forskarnas arbetssätt. Inspiration till arbetet har hämtats från projektet Hands-on-CERN som inriktar sig på att öka gymnasieelevers intresse och kunskaper inom partikelfysik. Genom att efterlikna Hands-on-CERNs sätt att arbeta har en laboration lämplig för gymnasieelever utformats. I laborationen får eleverna möjlighet att upptäcka att kvarkar finns trots att de inte går att observera i fria tillstånd, utan endast i bundna tillstånd; så kallade hadroner. Data från Z-bosonens sönderfall hämtas från ATLAS-experimentet i CERN analyseras, från vilken man kan dra slutsatsen att Z-bosonen sönderfaller oftare till hadroner än till leptoner, ett förhållande på ungefär 14:71. Förhållandet beror på att det finns fler möjliga hadroner som Z- bosonen kan sönderfalla till, vilket i sin tur beror på hadronernas inre struktur bestående av kvarkar, till skillnad från leptonerna som saknar inre struktur.