相关论文: PIONEER: Studies of Rare Pion Decays
The physics motivation and the conceptual design of the PIONEER experiment, a next-generation rare pion decay experiment testing lepton flavor universality and CKM unitarity, are described. Phase I of the PIONEER experiment, which was…
PIONEER is a rapidly developing effort aimed to perform a pristine test of lepton flavour universality (LFU) and of the unitarity of the first row of the CKM matrix by significantly improving the measurements of rare decays of the charged…
Allowed charged $\pi$ meson decays are characterized by simple dynamics, few available decay channels, mainly into leptons, and extremely well controlled radiative and loop corrections. In that sense, pion decays represent a veritable…
PIONEER is a next-generation experiment to measure the charged pion branching ratios to electrons vs muons $R_e/\mu = \frac{\Gamma\left(\pi^+ \rightarrow e^+ \nu (\gamma) \right)}{\Gamma\left(\pi^+ \rightarrow \mu^+ \nu (\gamma)\right)}$…
We present an overview of searches fo violation of lepton flavor universality with focus on low energy precision probes using pions, kaons, tau leptons, and nuclear beta decays. The current experimental results are reviewed, the theoretical…
Pion $\beta$ decay, $\pi^+ \to\pi^0 e^+ \nu_e$, offers a pristine way to measure the CKM matrix element $V_{ud}$ in a purely mesonic system, with excellent control over the hadronic matrix elements. We review the physics goals and current…
Building on the rare pion and muon decay results of the PIBETA experiment, the PEN collaboration has undertaken a precise measurement of B_{\pi e2} = R^\pi_{e/\mu}, the \pi^+ -> e^+\nu(\gamma) decay branching ratio, at the Paul Scherrer…
With few open channels and uncomplicated theoretical description, charged pion decays are uniquely sensitive to certain standard model (SM) symmetries, the universality of weak fermion couplings, and to aspects of pion structure and chiral…
The PIENU experiment at TRIUMF aims to measure the pion decay branching ratio $R={\Gamma}({\pi}^+{\rightarrow}e^+{\nu}_e({\gamma}))/{\Gamma}({\pi}^+{\rightarrow}{\mu}^+{\nu}_{\mu}({\gamma}))$ with precision $<0.1$% to provide a sensitive…
The combination of simple dynamics, small number of available decay channels, and extremely well controlled radiative and loop corrections, make charged pion decays a sensitive means for testing the underlying symmetries and the…
Simple dynamics, few available decay channels, and extremely well controlled radiative and loop corrections, make pion and muon decays a sensitive means for testing the underlying symmetries, the universality of weak fermion couplings, as…
Two results from the PIENU Experiment are presented reporting a test of lepton universality in pion decay and improved limits on heavy neutrinos coupling to positrons. The status of the full analysis for the $\pi^+ \rightarrow \mbox{e}^+…
The upcoming Mu3e experiment aims to search for the lepton flavour violating decay $\mu^+ \to e^+ e^- e^+$ with an unprecedented final sensitivity of one signal decay in $10^{16}$ observed muon decays by making use of an innovative…
The present report of the RF2 Topical Group to Snowmass 2021 describes the physics case for the studies of weak decays of strange and light quarks. Ongoing and proposed precision measurements of kaon, hyperon, pion and $\eta^{(\prime)}$…
We study the processes $\nu_\tau n \to \Lambda_c \tau^- (\pi^- \nu_\tau)$ and $\bar\nu_\tau p \to \Lambda \tau^+ (\pi^+ \bar\nu_\tau)$, with particular emphasis on the pion energy and angular distributions, as a possible signal for lepton…
In the Standard Model, lepton universality refers to the identical electroweak gauge interactions among charged leptons. The measurement of the branching ratio $R_{e / \mu} = \frac{\Gamma(\pi\rightarrow\ e…
The Mu3e experiment aims to search for the lepton-flavour violating decay $\mu^+\rightarrow\ \text{e}^+ \text{e}^+ \text{e}^-$ with a sensitivity to one signal decay in $10^{16}$ muon decays at a muon stopping rate of $2\times 10^9…
The PIBETA collaboration has used a non-magnetic pure CsI calorimeter operating at the Paul Scherrer Institute to collect the world's largest sample of rare pion and muon decays. We have extracted the absolute pi+ -> pi0 e+ nu decay…
After a decade of no measurements of pion and muon rare decays, PIBETA, a new experimental program is producing its first results. We report on a new experimental study of the pion beta decay, Pi(+) -> Pi(0) e(+) Nu, the Pi(e2 gamma)…
The muon is playing a unique role in sub-atomic physics. Studies of muon decay both determine the overall strength and establish the chiral structure of weak interactions, as well as setting extraordinary limits on…