Related papers: Improved upper limit on Muonium to Antimuonium Con…
The Mu2e experiment will search for the charged-lepton flavor violating (CLFV) neutrino-less conversion of a negative muon into an electron in the field of a nucleus. The conversion process results in a monochromatic electron with an energy…
A possibility of a verification of CPT-invariance of QED for bound states by example of muonium or antimuonium produced in reactions of scattering of electrons or positrons by nuclei is considered. The number of events of the muonium…
Exploring the leptonic sector in frontier experiments is more of importance nowadays, since the conservation of lepton flavor and total lepton number are not guaranteed anymore in the Standard Model after the discovery of neutrino…
New results of a search for the ultra-rare decay $\mu \to e \gamma$ by the MEG collaboration are reported in this contribution. The data were taken during 2009 and correspond to approximately 6.5 10$^{13}$ muon stopped on target. A maximum…
Using a prompt neutrino beam in which a nu_tau component was identified for the first time, the nu_tau magnetic moment was measured based on a search for an anomalous increase in the number of neutrino-electron interactions. One such event…
Fundamental physics could be described as having a muon problem. Discrepancies between theory and experiment in a number of muonic measurements ($r_P$, $a_\mu$, $H\rightarrow\mu\tau$, $\mathcal{R}_K$, $\mathcal{R}_{D^*}$) have been observed…
The experimental search for coherent neutrinoless conversion of muon to electron in the presence of a nucleus, aims to probe the possibility of charged lepton flavour violation. The COMET experiment at J-PARC is one such setup offering…
We present a new measurement of the positive muon magnetic anomaly, $a_\mu \equiv (g_\mu - 2)/2$, from the Fermilab Muon $g\!-\!2$ Experiment using data collected in 2019 and 2020. We have analyzed more than 4 times the number of positrons…
The 3.6 \sigma discrepancy between the predicted and measured values of the anomalous magnetic moment of positive muons can be explained by the existence of a new dark boson Z_\mu with a mass in the sub-GeV range, which is coupled…
Muon-electron conversion in nuclei is considered in the framework of the Dualized Standard Model. The ratio $B_{\mu-e}$ of the conversion rate to the total muon capture rate is derived, and computed for several nuclei in a parameter-free…
A new search signature for excited leptons is explored. Excited muons are sought in the channel $pp \to \mu\mu^* \to \mu \mu\textrm{ jet jet}$, assuming both the production and decay occur via a contact interaction. The analysis is based on…
The MEG experiment took data at the Paul Scherrer Institute in the years 2009--2013 to test the violation of the lepton flavour conservation law, which originates from an accidental symmetry that the Standard Model of elementary particle…
An electron antineutrino mass has been measured in tritium beta-decay in the "Troitsk nu-mass" experiment. The setup consists of a windowless gaseous tritium source and an electrostatic electron spectrometer. The whole data set acquired…
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…
Inverse muon decay, $\nu_\mu e^-\to\mu^-\nu_e$, is a reaction whose cross-section can be predicted with very small uncertainties. It has a neutrino energy threshold of $\approx 11$ GeV and can be used to constrain the high-energy part of…
Muonium, the atom which consists of a positive muon and an electron, has been discovered by a team led by Vernon W. Hughes in 1960. It is in many respects the most ideal atom available from nature. Due to the close confinement in the bound…
The final results of the search for the lepton flavour violating decay $\mu^{+} \rightarrow {\rm e^{+}} \gamma$ based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009--2013 and totalling…
The MEG II experiment at Paul Scherrer Institute (PSI) in Switzerland aims to achieve a sensitivity of $6\times10^{-14}$ on the charged lepton flavor violating decay $\mu^+\to e^+\gamma$. The current upper limit on this decay is…
Searches for new physics using muons are reviewed. Particular attention is paid to muon number non-conserving processes, like the decay muon-->e+gamma and muon-electron conversion in muonic atoms. Also, experimental determinations and…
We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $\mu^+ \to \mathrm{e}^+\mathrm{X}, \mathrm{X} \to \gamma\gamma$. This search uses a dataset resulting from $7.5\times 10^{14}$…