Related papers: Positron annihilation in the MuPs system

We investigate one-photon annihilation of the electron-positron pair in the field of a central, very heavy and positively charged atomic nucleus. The explicit formula for the annihilation rate of this process $\Gamma^{(b)}_{1 \gamma}$ is…

We report results from the MuLan measurement of the positive muon lifetime. The experiment was conducted at the Paul Scherrer Institute using a time-structured surface muon beam and a segmented plastic scintillator array. Two different…

More than 10^43 positrons annihilate every second in the centre of our Galaxy yet, despite four decades of observations, their origin is still unknown. Many candidates have been proposed, such as supernovae and low mass X-ray binaries.…

The Fermi Constant, G_F, describes the strength of the weak force and is determined most precisely from the mean life of the positive muon, tau_mu. Advances in theory have reduced the theoretical uncertainty on G_F as calculated from tau_mu…

The kinetic energy distribution of ground state muonic hydrogen atoms mu-p(1S) is determined from time-of-flight spectra measured at 4, 16, and 64 hPa H2 room-temperature gas. A 0.9 keV-component is discovered and attributed to…

The 6s-np_j (n=6-9) electric-dipole matrix elements and 6s-nd_j (n=5-7) electric-quadrupole matrix elements in Ba+ are calculated using the relativistic all-order method. The resulting values are used to evaluate ground state dipole and…

The complete contribution to the muonium hyperfine splitting of relative order alpha^3(m_e/m_mu)ln(alpha) is calculated. The result amounts to 0.013 kHZ, much smaller than suggested by a previous estimate, and leads to a 2-sigma shift of…

Para positronium composed by an electron-antielectron pair is an unstable system decaying into two high energetic gamma photons via self annihilation process, due to the conservation of the charge conjugation parity in electromagnetically…

Radiative deexcitation (RD) of the metastable 2S state of muonic protium and deuterium atoms has been observed. In muonic protium, we improve the precision on lifetime and population (formation probability) values for the short-lived…

We present the first measurement of the energy spectrum up to 70 MeV of electrons from the decay of negative muons after they become bound in $^{27}$Al atoms. The data were taken with the TWIST apparatus at TRIUMF. We find a muon lifetime…

The impact of unstable Majorana tau neutrinos on primordial nucleosynthesis is considered. The mass and lifetime of nu_tau are taken in the intervals 0.1-20 MeV and 0.001-400 sec respectively. The studied decay modes are nu_tau -> nu_mu +…

We present a detailed report of the method, setup, analysis and results of a precision measurement of the positive muon lifetime. The experiment was conducted at the Paul Scherrer Institute using a time-structured, nearly 100%-polarized,…

An initial measurement of the lifetime of the positive muon to a precision of 16 parts per million (ppm) has been performed with the FAST detector at the Paul Scherrer Institute. The result is tau_mu = 2.197083 (32) (15) microsec, where the…

The electron-positron annihilation spectrum observed by SPI/INTEGRAL during deep Galactic Center region exposure is reported. The line energy (510.954$\pm$0.075 keV) is consistent with the unshifted annihilation line. The width of the…

We studied the radiative muon decay $\mu^+ \to e^+\nu\bar{\nu}\gamma$ 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…

We revisit the upper bound on the annihilation cross-section, $\langle\sigma v\rangle$ of a stable dark matter (DM) of mass $5\times10^2-10^{14}$ GeV by considering five different channels: $W^+W^-$, $b\bar{b}$, $\mu^+\mu^-$,…

We calculate the lifetime of both the o-Ps and the p-Ps positronium annihilation decay $ Ps\to\gamma\gamma$ in the strong circular polarized laser field. We take a strategy of the factorization to separate the effects caused by the Coulomb…

Studies based on imaging the annihilation of the electron (e$^{-}$) and its antiparticle positron (e$^{+}$) open up several interesting applications in nuclear medicine and fundamental research. The annihilation process involves both the…

The AMS-02 collaboration has recently presented measurements of excellent quality of the cosmic electron and positron fluxes as well as the positron fraction. We use the measurements of the positron flux to derive, for the first time,…

Positronium-based imaging requires realistic modelling of positronium (Ps) decay in matter. We introduce a modular Ps decay model implemented in GATE 9.4 and GATE 10, enabling the definition of an arbitrary number of decay channels…