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Neutral Meson Production in Ag+Ag Collisions at 1.58 A GeV with HADES Electromagnetic Calorimeter
Prozorov, Alexandr ; Kugler, Andrej (advisor) ; Bielčík, Jaroslav (referee) ; Závada, Petr (referee)
Title: Neutral Meson Production in Ag+Ag Collisions at 1.58 A GeV with HADES Electromagnetic Calorimeter Author: Alexandr Prozorov Abstract: The Dielectron Spectrometer HADES operating at the SIS18 synchro- tron, FAIR/GSI Darmstadt, recently provided new intriguing results on the pro- duction of electron pairs and strangeness from nucleus-nucleus collisions, as well as from elementary reactions, in the energy region of 1 − 2 A GeV. In 2019 the spectrometer was complemented by an electromagnetic calorimeter based on lead- glass modules, which allows us to measure photons and thus study the production of π0 and η mesons via their two-photon decay. Knowledge of the neutral-meson production is a mandatory prerequisite for the interpretation of dielectron data. In particular, the directed and elliptic flow of neutral mesons with respect to transverse momentum and rapidity will be shown for different centrality classes in Ag + Ag collisions at 1.58 A GeV. The results of the analysis corresponding to the 14 × 109 events will be confronted with the results of other experiments and with the current model calculations. Keywords: baryonic medium, hadrons, relativistic heavy-ion collisions, neutral mesons, pion flow
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Time-dependent CP violation in B0 → ηc KS0 decays at the Belle experiment, Alignment of the Belle II detector
Bilka, Tadeáš ; Doležal, Zdeněk (advisor) ; Bielčík, Jaroslav (referee) ; Glazov, Alexander (referee)
This thesis deals with two independent yet closely related topics. In the first part, a measurement of branching fraction and time-dependent CP violation in B0 → ηcK0 S, ηc → K0 SK± π∓ decays is performed. This decay allows access to sin 2ϕ1, where ϕ1 is an angle of the unitary triangle of the Cabibbo-Kobayashi- Maskawa quark mixing matrix. The measurement is based on the entire dataset of the Belle experiment, which consists of 772 × 106 B meson pairs collected at the KEKB e+ e− collider. The extracted mixing-induced and direct CP- violation parameters read sin 2ϕ1 ≃ S = 0.59 ± 0.17 (stat) ± 0.07 (syst) and A = 0.16 ± 0.12 (stat) ± 0.06 (syst), respectively. The measured product of branching fractions B(B0 → ηcK0 S) × B(ηc → K0 SK± π∓ ) is (9.8 ± 0.6 (stat) ± 0.4 (syst)±2.3 (int))×10−6 , where the last uncertainty accounts for interference with non-resonant background. The second part deals with the alignment of the vertex detector and the central drift chamber of the Belle II experiment at the SuperKEKB collider, which is a next-generation Super-B-Factory. With the new pixel detector and the presented alignment method, Belle II achieves approximately twice better impact parameter resolutions than Belle. The presented alignment procedure involves a simultaneous determination of about sixty thousand...
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Study of CP-violation at the Belle experiment
Červenkov, Daniel ; Doležal, Zdeněk (advisor) ; Bielčík, Jaroslav (referee) ; Scheirich, Daniel (referee)
We present a first measurement of time-dependent CP-violation in B0 → D∗∓ ρ± , where D∗∓ → D0 π. The analysis was performed using the final Belle dataset containing 772 × 106 B ¯B pairs collected at the KEKB e+ e− collider. Three D0 decay modes are analyzed, K∓ π± , K∓ π± π0 , and K∓ π± π∓ π± . Since the studied decay is a scalar → vector vector decay, three helicity configurations are present. Exploiting the helicity configura- tions via angular analysis, the time-dependent CP-violation parameters encoding 2ϕ1 +ϕ3 are obtained from the fit. 1
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