ﻻ يوجد ملخص باللغة العربية
The COMPASS Collaboration at CERN has investigated the reaction $pi^- gamma rightarrow pi^-pi^-pi^+$ embedded in the Primakoff reaction of $190~textrm{GeV}$ pions scattering in the Coulomb field of a lead target, $pi^- text{Pb} rightarrow pi^-pi^-pi^+ text{Pb}$. Exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at momentum transfer below $0.001~(text{GeV}/c)^2$. Using a partial-wave analysis the amplitudes and relative phases of the $a_2(1320)$ and $pi_2(1670)$ mesons have been extracted, and the Coulomb and the diffractive contributions have been disentangled. Measuring absolute production cross sections we have determined the radiative width of the $a_2(1320)$ to be $Gamma_0(a_2(1320) rightarrow pigamma) = (358 pm 6_{textrm{stat}} pm 42_{textrm{syst}})~textrm{keV}$. As the first measurement, $Gamma_0(pi_2(1670) rightarrow pigamma) = (181 pm 11_{textrm{stat}} pm 27_{textrm{syst}})~textrm{keV} cdot (textrm{BR}^{textrm{PDG}}_{f_2 pi}/textrm{BR}_{f_2 pi})$ is obtained for the radiative width of the $pi_2(1670)$, where in this analysis the branching ratio $textrm{BR}^{textrm{PDG}}_{f_2 pi}=0.56$ has been used. We compare these values to previous measurements and theoretical predictions.
We studied the radiative muon decay $mu^+ to e^+ ubar{ u}gamma$ by using for the first time an almost fully polarized muon source. We identified a large sample (~13000) of these decays in a total sample of 1.8x10^14 positive muon decays collected in
Using 980 ${rm fb}^{-1}$ of data {collected} with the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider, we report the measurements of the masses, and the first measurements of the instrinsic widths, of the $Sigma_c(2455)^+$ an
We report branching fraction measurements of four decay modes of the $Lambda_{c}^{+}$ baryon, each of which includes an $eta$ meson and a $Lambda$ baryon in the final state, and all of which are measured relative to the $Lambda_{c}^{+} rightarrow p K
It is proposed to use the isomer ionic ground state $^{229m}$Th$^{4+}$ embedded in transparent crystals for precision determination of unknown neutrino parameters. Isolation from solid environment of the proposed nuclear process, along with available
The ratio of the electron and muon widths of the $J/psi$ meson has been measured using direct $J/psi$ decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result $Gamma_{ee}(J/psi)/Gamma_{mumu}(J/psi)=1.0022pm0.0044pm0.0048 (0