Related papers: Michel parameters in radiative muon decay
Precise measurements of the lepton properties provide stringent tests of the Standard Model and accurate determinations of its parameters. We overview the present status of tau physics, highlighting the most recent developments, and discuss…
In this work we study the radiative leptonic decays of $B^-$, $D^-$ and $D_s^-\to \gamma l \bar{\nu}$, including both the short-distance and long-distance contributions. The short-distance contribution is calculated by using the…
We study the radiative leptonic $D$ meson decays of $D^+_{(s)}\to \l^+\nu_{\l}\gamma$ ($\l=e,\mu,\tau$), $D^0\to \nu\bar{\nu}\gamma$ and $D^0\to \l^+\l^-\gamma$ ($l=e,\mu$) within the light front quark model. In the standard model, we find…
We reconsider decays of pseudoscalar mesons (P) to neutrino pairs and possibly additional photons in presence of (light) Majorana neutrinos. For this purpose we derive a model-independent general parametrization of neutrino mass matrices…
One of the key assumptions of the Standard Model of fundamental particles is that the interactions of the charged leptons, namely electrons, muons, and taus, differ only because of their different masses. While precision tests comparing…
We analyze the tauonic semileptonic baryon decays $\Lambda^0_b \to \Lambda^+_c + \tau^{-} +\bar \nu_{\tau}$ with particular emphasis on the lepton helicity flip contributions which vanish for zero lepton masses. We calculate the total rate,…
We consider $K_{l2}$ decays to the order $O(\alpha)$. We perform a matching calculation, using a specific model with vector meson dominance in the long distance part and the parton model in the short distance part. By considering the…
We derive the decay widths for the leptonic decays of heavy charged pseudoscalars to massive sterile neutrinos, $M^{\pm} \to \ell^{\pm} + N$, within the frameworks involving the Standard Model and two-Higgs doublets (type II). We then apply…
Using LEP1, SLD and LEP2 data, for tau lepton production, and data from CDF, D0 and LEP2, for W decays into tau leptons, we set model independent limits on non-standard electromagnetic and weak magnetic moments of the tau lepton. The most…
We discuss predictions for the lepton-flavour changing decays Z --> e mu, mu tau, e tau which may be searched for at the Giga-Z option of the Tesla Linear Collider project with Z resonance production rates as high as 10^9. We try to be as…
We analyze the possibility of experimental investigation of new low-energy relations between the values of resonance masses in the meson form factors and the differential rate of radiative kaon decay $K^+\to \pi^+ e^+e^-(\mu^+\mu^- )$ at…
Decays of B mesons to states involving tau leptons can be used as a tool to search for the effects of new physics, such as those involving a charged Higgs boson. The experimental status of the decays B -> tau nu and B -> D^(*) tau nu is…
We present a non-perturbative calculation of the form factors which contribute to the amplitudes for the radiative decays $P\to \ell \bar \nu_\ell \gamma$, where $P$ is a pseudoscalar meson and $\ell$ is a charged lepton. Together with the…
The leptons are viewed as composite objects, exhibiting anomalous magnetic moments and anomalous flavor-changing transition moments. The decay $\mu \to e \gamma$ is expected to occur with a branching ratio of the same order as the present…
The leptonic decays of the tau lepton provide relevant tests on the structure of the weak currents and the universality of their couplings to the gauge bosons. The hadronic tau decay modes constitute an ideal tool for studying low--energy…
We present a novel method for the reconstruction of events containing pairs of hadronically decaying tau leptons at collider experiments. This method relies on accurate knowledge of the tau production vertex and precise measurement of its…
Motivated by the recent investigation of neutrinoless $\tau$-lepton decays by the CLEO collaboration, we perform a systematic analysis of such decays in a possible new-physics scenario with heavy Dirac/Majorana neutrinos, including…
We study the impact of recent B-factories measurements and upper limit of radiative and semileptonic rare B-decays. We present model independent constraints on the relevant Wilson coefficients and show the impact on the parameter space of…
We report the first measurement of the Michel parameter $\xi^\prime$ in the $\tau^-\to\mu^-\bar{\nu}_\mu\nu_\tau$ decay with a new method proposed just recently. The measurement is based on the reconstruction of the…
We present the differential rates and branching ratios of the radiative decays $\tau \to l \bar{\nu} \nu \gamma$, with $l=e$ or $\mu$, and $\mu \to e \bar{\nu} \nu \gamma$ in the Standard Model at next-to-leading order. Radiative…