Flavor physics in the standard model and beyond

This thesis is focused on the flavor anomalies in semi-leptonic b quark decays and on calculations of higher order QCD effects in radiative rare B meson decays. The introduction covers topics and concepts relevant for this thesis and is followed by several papers in which Leptoquarks are introduced as possible extensions of the Standard Model. We analyze several models regarding their potential of resolving one or several of the flavor anomalies. Explanations to the individual anomalies are correlated through loop effects, which we calculate and show their phenomenological importance. Effects arising through Leptoquark interactions with the Standard Model Higgs boson are independent of fermionic couplings needed to explain the flavor anomalies. Due to this independence, such effects can serve as a complementary window to distinguish among different Leptoquark representations in future precision experiments. Additionally, Leptoquarks affect purely leptonic transitions through loop-effects, which we calculate in detail. Future experiments are expected to reach very high precisions in these transitions and will therefore be able to strengthen the case for certain models or put stringent constraints on others. The final part of this thesis consists of two ongoing projects in single and double radiative rare B meson decays. We calculate three-loop contributions of the current-current operator to b → sγ while retaining full analytic dependence on the charm quark mass. Furthermore, gluon bremsstrahlung corrections to the double differential decay spectrum of b → sγγ are considered.

2021

dissertation

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