The life-time of the four-body atomic system MuPs ($μ^{+} e^{-}_2 e^{+}$ or muonium-positronium) against positron annihilation has been evaluated as $τ= \frac{1}Γ \approx 4.076453 \cdot 10^{-10}$ $sec$. Various annihilation rates for MuPs are determined to a good numerical accuracy, e.g., $Γ_{2 γ} \approx$ 2.446485$\cdot 10^{9}$ $sec^{-1}$, $Γ_{3 γ} \approx$ 6.62798$\cdot 10^{6}$ $sec^{-1}$, $Γ_{4 γ} \approx$ 3.61680$\cdot 10^{3}$ $sec^{-1}$, $Γ_{5 γ} \approx$ 6.32973 $sec^{-1}$. The hyperfine structure splitting for the ground state in the MuPs system has also been evaluated as $Δ$ = 23.078 $MHz$.
In the current work, We investigated the production of neutral Higgs boson and two charged Charginos owing to electron-positron annihilation via different propagators
Processes of electron-positron annihilation into a pair of fermions were considered. Forward-backward and left-right asymmetries were studied, taking into account polarization of initial and final particles. Complete 1-loop electroweak radiative corrections were included. A wide energy range including the $Z$ boson peak and higher energies relevant for future $e^+e^-$ colliders was covered. Sensitivity of observable asymmetries to the electroweak mixing angle and fermion weak coupling was discussed.
In a companion publication, we have explored how to examine the summation of large logarithms in a parton shower. Here, we apply this general program to the thrust distribution in electron-positron annihilation, using several shower algorithms. The method is to work with an appropriate integral transform of the distribution for the observable of interest. Then, we reformulate the parton shower calculation so as to obtain the transformed distribution as an exponential for which we can compute the terms in the perturbative expansion of the exponent.
The explicit expression for the R-ratio of electron-positron annihilation into hadrons, which properly accounts for all the effects due to continuation of the spacelike perturbative results into the timelike domain, is obtained at an arbitrary loop level. Several equivalent ways to derive a commonly employed approximation of the R-ratio are recapped and the impact of discarded in the latter higher-order pi2-terms on the evaluation of the strong running coupling is elucidated. The obtained results substantially facilitate the theoretical study of electron-positron annihilation into hadrons and …
High energy positron annihilation is a viable mechanism to produce dark photons ($A^\prime$). This reaction plays a significant role in beam-dump experiments using experiments using multi-GeV electron-beams on thick targets by enhancing the sensitivity to $A^\prime$ production. The positrons produced by the electromagnetic shower can produce an $A^\prime$ via non-resonant ($e^+ + e^- \to γ+ A^\prime$) and resonant ($e^+ + e^- \to A^\prime$) annihilation on atomic electrons. For visible decays, the contribution of resonant annihilation results in a larger sensitivity with respect to limits deri…
Electron-positron annihilation into a pair of top quarks is considered at the energy of the future collider CLIC. Polarization components of the top quark are calculated with the $γt \bar{t}$ and $Z t \bar{t}$ interactions which follow from the Lagrangian of the effective field theory of the Standard Model. The polarization vector as a function of the scattering angle is calculated and averaged components of polarization are analyzed as functions of anomalous coupling constants. Extrema of these observables (maxima, minima and saddle points) are studied as functions of the $e^+ e^-$ energy.
Electron-positron annihilation largely occurs in local thermal and chemical equilibrium after the neutrinos fall out of thermal equilibrium and during the Big Bang Nucleosynthesis (BBN) epoch. The effects of this process are evident in BBN yields as well as the relativistic degrees of freedom. We self-consistently calculate the collision integral for electron-positron creation and annihilation using the Klein-Nishina amplitude and appropriate statistical factors for Fermi-blocking and Bose-enhancement. Our calculations suggest that this annihilation freezes out when the photon-electron-positro…
We apply the modern multiloop methods to the calculation of the total cross sections of electron-positron annihilation to 2 and 3 photons exactly in $s/m^2$ with the accuracy $O(α^3)$. Examining the asymptotics of our results, we find agreement with Ref. [Andreassi_et_al_1962] and discover mistakes in the results of Refs. [Eidelman&Kuraev_1978,Berends&Kleiss_1981]. This mistake is due to the terms, omitted in differential cross section in Refs. \[Eidelman&Kuraev_1978,Berends&Kleiss_1981], which are peaked in the kinematic region with all three photons being quasi-parallel to the collision axis…
