magistrsko delo
Blaž Bortolato (Author), Jernej Kamenik (Mentor)

Abstract

V magistrskem delu preučujemo razpad $B \rightarrow \nu \nu (\gamma)$, pri katerem mezon $B \in \{B_s, B_d\}$ razpade v dva nevtrina in morebiten nizkoenergijski foton (foton je neopazljiv), in razpad $B \rightarrow \nu \nu \gamma$, pri katerem je foton opazljiv, v okviru razširjenega standardnega modela z $n=3$ dodatnimi desnoročnimi nevtrini. V tem modelu so nevtrini v masni bazi Majoranovi fermioni. Matrične elemente matrik nevtrinskega sektorja izrazimo z na novo izpeljano parametrizacijo, ki je naravna posplošitev parametrizacije Casas-Ibara. Diferencialni razpadni širini razpadov $B \rightarrow \nu_C \nu_D$ in $B \rightarrow \nu_C \nu_D \gamma$ pa analitično izpeljemo v razširjenemu standardnemu modelu za splošen $n$. Pri obravnavi odvisnosti razvejitvenih razmerij razpadov $B \rightarrow \nu \nu (\gamma)$ in $B \rightarrow \nu \nu \gamma$ predpostavimo, da detektor pokriva celotni prostorski kot glede na točko razpada mezona $B$. Na koncu pa komentiramo še primer, ko ta ne pokriva celotnega prostorskega kota. V slednjem se izkaže, da je prispevek razpada $B \rightarrow \nu \nu (\gamma)$ k pogostosti razpadov mezona $B$ v neopazljive končne produkte lahko popolnoma zanemarljiv. Predstavljene ugotovitve veljajo kvalitativno tudi za razpade drugih okusnih nevtralnih mezonov v osnovnem stanju v dva nevtrina in morebiten (nizkoenergijski) foton.

Keywords

fizika osnovnih delcev;razpadi mezonov;nevtrini;Majoranovi fermioni;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL FMF - Faculty of Mathematics and Physics
Publisher: [B. Bortolato]
UDC: 539.12
COBISS: 3349092 Link will open in a new window
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Downloads: 167
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Other data

Secondary language: English
Secondary title: Rare $B \rightarrow \nu \nu (\gamma)$ decay in the framework of the Standard Model with additional chiral right-handed neutrinos.
Secondary abstract: In this master thesis, we study the $B \rightarrow \nu \nu (\gamma)$ decay, where $B \in \{B_s, B_d\}$ meson decays into two neutrinos and a potential soft photon, and the $B \rightarrow \nu \nu \gamma$ decay with an observable photon in the framework of the Standard Model with $n=3$ additional chiral right-handed neutrinos. In this model neutrinos in the mass basis are Majorana fermions. We parametrize the mass matrices in the neutrino sector with a newly derived parametrization which naturally generalizes the well known Casas-Ibara parametrization. The differential decay widths of the $B \rightarrow \nu_C \nu_D$ and $B \rightarrow \nu_C \nu_D \gamma$ decay modes are derived for the general case (with $n$ additional neutrinos). The branching ratios of the $B \rightarrow \nu \nu (\gamma)$ and $B \rightarrow \nu \nu \gamma$ decays are investigated within the assumption that the photon detectors cover the full solid angle around the decay point of the $B$ meson. The more general case is commented on at the end of the thesis: we find that the contribution of the $B \rightarrow \nu \nu (\gamma)$ decay to $B$ meson decays with non-observable decay products can be completely negligible. The results presented in this work qualitatively apply also to other decays of pseudoscalar neutral flavored mesons to two neutrinos and a potential (soft) photon.
Secondary keywords: physics of elementary particles;meson decays;neutrinos;Majorana fermions;
Type (COBISS): Master's thesis/paper
Study programme: 0
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages: 67 str.
ID: 11212350