Related papers: Positronium-ion decay
We study equilibrium statistical mechanics of classical point counter-ions, formulated on 2D Euclidean space with logarithmic Coulomb interactions (infinite number of particles) or on the cylinder surface (finite particle numbers), in the…
It is shown that, in the bound state picture, the $\Lambda_c(2593) \to\Lambda_c\gamma$ and $\Lambda_c(2625)\to\Lambda_c\gamma$ decays are severely suppressed. On the other hand, for their bottom counterparts, which are predicted to have…
The decay $J/\psi \to \omega p \bar p$ is studied using a $5.8 \times 10^7$ $J/\psi$ event sample accumulated with the BES II detector at the Beijing electron-positron collider. The decay branching fraction is measured to be $B(J/\psi \to…
The universal variational expansion for the non-relativistic three-body systems is explicitly constructed. Three-body universal expansion can be used to perform highly accurate numerical computations of the bound state spectra in arbitrary…
Using a sample of $(1310.6\pm7.0)\times10^6$ $J/\psi$ events recorded with the BESIII detector at the symmetric electron positron collider BEPCII, we report the observation of the decay of the $(1^1 S_0)$ charmonium state $\eta_c$ into a…
We have calculated all contributions to the energy levels of parapositronium at order $m \alpha^7$ coming from vacuum polarization corrections to processes involving virtual annihilation to two photons. This work is motivated by ongoing…
We compute the complete O(alpha^2) QED corrections to the electron energy spectrum in unpolarized muon decay, including the full dependence on the electron mass. Our calculation reduces the theoretical uncertainty on the electron energy…
Relative order \alpha(Z\alpha)^3 shift of the energy levels induced by the vacuum polarization is reexamined for a bound system of two particles with masses m and M. Recent results for hydrogen and for positronium are shown to contain an…
The possibility of using neutral and double ionized erbium for atomic clocks of high precision is investigated. In both cases the narrow electric quadrupole clock transition between the ground and first exited state of the same…
We discuss positronium decays with emphasis on tests of fundamental symmetries and the constraints from measurements of other precision observables involving electrons and photons.
We determine the gyromagnetic factor of the positronium ion, a three-body system consisting of two electrons and a positron, including first relativistic corrections. We find that the g-factor is modified by a term -0.51(1)alpha^2,…
We study radiative decay modes of the Z-boson into heavy quark bound states. We find that the widths for these decays are extremely small. We conclude that these decays will not be detectable for the time being unless there is a significant…
We present preliminary results on the $\rho$ meson decay width from $N_f=2+1$ full QCD configurations generated by PACS-CS Collaboration. The decay width is estimated from the $P$-wave scattering phase shift for the isospin $I=1$ two-pion…
We compute the decay rate of the Standard Model Higgs boson to bottom quarks to order $\alpha\alpha_s$. We apply the optical theorem and calculate the imaginary part of three-loop corrections to the Higgs boson propagator using asymptotic…
The first direct search for the double electron capture ($2\epsilon$) and the electron capture with positron emission ($\epsilon\beta^+$) in $^{144}$Sm to the ground state and to the excited levels of $^{144}$Nd was realized by measuring -…
Discrete symmetries play an important role in particle physics with violation of CP connected to the matter-antimatter imbalance in the Universe. We report the most precise test of P, T and CP invariance in decays of ortho-positronium,…
Three photon decay rate of $J/\psi$ is studied using two $N_f=2$ twisted mass gauge ensembles with lattice spacings $a\simeq 0.085$ fm (I) and $0.067$ fm(II). Using a new method, only the correlation functions directly related to the…
The shape of the beta decay energy distribution is sensitive to the mass of the electron neutrino. Attempts to measure the endpoint shape of tritium decay have so far seen no distortion from the zero-mass form, thus placing an upper limit…
We analyse data on pi pi and gamma gamma scattering below 700 MeV within an improved analytic K-matrix model. This model is based on an effective theory with couplings between resonances, hadrons and photons. The two-photon decay of a…
Probabilities of various final states are determined numerically for a number of {\ss}- decaying light atoms. In our evaluations of the final state probabilities we have used the highly accurate atomic wave functions constructed for each…