Rare radiative charm decays in and beyond the standard model
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Date
2022
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Abstract
This thesis comprises a study of rare radiative |Δc| = |Δu| = 1 transitions within
and beyond the standard model of particle physics. For the 18 three-body decays
D → P1 P2 ɣ with 𝑃 = π, K decay amplitudes are derived using Low’s theorem, QCD
factorization and heavy hadron chiral perturbation theory. Standard model predictions for
branching ratios, CP asymmetries as well as forward-backward asymmetries are determined.
Moreover, the effects of new physics in the coefficients of the electromagnetic dipole
operators are investigated respecting the current constraints. The photon polarization in
Ds→ K1(→ Kπ π) ɣ decays is studied with respect to new physics effects in the dipole
coefficients. Within the standard model, the polarization parameter agrees with the SM-
like partner decay 𝐷+ → 𝐾1 (→ 𝐾π π)) ɣ up to U-spin breaking corrections. The existence
of partner decays allows to construct a null test which does not require precise knowledge
of the hadronic K1 → Kπ π decay. Finally, different ways to test the standard model with
rare radiative decays of charm baryons are discussed. Based on the approximate SU(3)𝐹
symmetry of QCD as well as its subgroups, relations between partner decays are worked
out. Branching ratios, CP asymmetries as well as the photon polarizations are considered
as observables and the potential of new physics effects is estimated. Methods for the
extraction of the photon polarization from two-body decays Bc → B ɣ of polarized charm
baryons as well as from decay chains Bc → B(→ B′ 𝑃 ) ɣ with self-analyzing hyperons 𝐵
are presented.
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Keywords
Rare charm decays, Radiative decays, Beyond standard model physics, SU(3)_F relations