Related papers: Revisiting $K\rightarrow \pi a$ decays
As is known from previous studies the lepton number violating decays $K^+\to \pi^- + l^{+}_1 + l^{+}_2$ have good prospects to probe new physics beyond the Standard Model and provide valuable information on neutrino masses and mixing. We…
We suggest that the decay modes of kaons with a pion and a pionium ($\pi^+\pi^-$ atom) in the final state can constitute a not yet considered background to the very rare decay $K\to\pi\nu\bar\nu$. In fact, a part of pioniums may escape the…
We present a comprehensive study of axion-like particles (ALPs) in meson decays, combining effective field theory and ultraviolet models within the open-source tool ALPaca. The analysis accounts for running and matching effects across…
The $\tau$ lepton decays $\tau \to [K^- K^0 \pi^0, K^- K^+ \pi^-, K ^0 \bar{K^0} \pi^-] \nu_{\tau}$ are described in the $U(3) \times U(3)$ NJL quark model. The contact channel and intermediate channels with axial-vector, vector and…
The amplitudes of the $K^{\pm} \to 3\pi$ and $K \to 2\pi$ decays are expressed in terms of different combinations of one and the same set of CP-conserving and CP-odd parameters. Extracting the magnitudes of these parameters from the data on…
In addition to giving rise to spectacular new physics signals in the final states of meson decays, Axion-like-particles also induce modifications in the standard model decays of mesons. These `indirect' signatures can be parametrized as the…
In this article we analyze the contribution from intermediate spin-0 and spin-2 resonances to the $\tau\to\nu \pi\pi\pi$ decay by means of a chiral invariant Lagrangian incorporating these mesons. In particular, we study the corresponding…
This PhD thesis studies some hadronic and radiative decays of the tau lepton using a Chiral Lagrangian including resonance fields. After a theoretical introduction, the decays to the $(\pi \pi \pi)^-$, $(KK\pi)^-$ and $\eta^{(\prime)} \pi^-…
The recent observation of B_d -> pi^0 pi^0 at the B factories with a surprisingly large branching ratio represents a challenge for theory, and complements the amazingly small B_d -> pi^+ pi^- rate. We point out that all puzzling B -> pi pi…
The decays K_{L,S} -> \pi^o \pi^o \nu \bar{\nu} and K_{L,S} -> \pi^+ \pi^- \nu \bar{\nu} involve the weak transition from a strange to a non-strange quark. Although they have considerably smaller branching ratios than those for the…
We investigate the rare decay processes of the K mesons, K_{L,S} -> \pi^0 \nu \bar{\nu} and K^{+} -> \pi^+ \nu \bar{\nu} in LR model with lepton family number being well conserved. In these processes, scalar operators…
Rare $K \to \pi \nu \bar \nu$ decays, being dominated by short distance contributions within the Standard Model (SM), open a window for New Physics (NP) searches at low energies. The $ K \to \pi \nu \bar\nu $ branching ratios are expected…
In this paper we use one-loop chiral perturbation theory in order to compare lattice computations of the K+ to pi+ pi0 decay amplitude with the experimental value. This makes it possible to investigate three systematic effects that plague…
Tree-level $b$ decays play a critical role in characterising the quark flavour sector, and exposing possible effects of physics beyond the Standard Model. These proceedings cover recent results from the LHCb experiment on semileptonic $b$…
We present a consistent implementation of weak decays involving an axion or axion-like particle in the context of an effective chiral Lagrangian. We argue that previous treatments of such processes have used an incorrect representation of…
The processes of $K^-p \to \pi^0 \pi^0 \Sigma^0$ and $K^- p \to \pi^0 \Lambda(1405)$ are studied within the effective Lagrangian approach. In addition to the ``background" contribution from the $u$-channel nucleon pole term, contribution…
We study the decays $K\to\pi\pi$ in one-loop two-flavour Chiral Perturbation Theory. We provide arguments why the calculation of the coefficient of the pionic chiral logarithm $\logm = M^2\log M^2$ is unique and then perform the…
Because quarks in hadronic states are subjected to strong QCD forces, it is not straight-forward to apply calculation obtained at the quark level to physical processes involving hadrons. In this paper we present a new approach to treat the…
The $B\to\pi K$ decays with significant electroweak penguin contributions show a puzzling pattern. We explore this "$B\to\pi K$ puzzle" through a systematic strategy. The starting point, which is essentially unaffected by electroweak…
We study hadronic decays of mesons and baryons in the context of the Dyson-Schwinger equations of QCD. Starting from a well-established effective interaction in rainbow-ladder truncation, we consistently calculate all ingredients of the…