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Register a new userThe Implications of $bar{ u}_e e^-to W^-gamma$ for the Detection of High-Energy $bar{ u}_e$
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H. Athar
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We discuss some motivations for detecting high-energy neutrinos through the pure electroweak processes such as $bar{ u}_e e^-to W^- $ and $bar{ u}_e e^-to W^-gamma$. We argue that the latter process can be viewed as an enhancement to the former one. The event-rate enhancement is estimated.
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Absorption of high-energy $bar{ u}_e$ over electrons above the W boson production threshold is reexamined. It is pointed out that, in the case of photon emissions along the direction of incident high-energy $bar{ u}_e$, the kinematically allowed average energy carried by the final state hard photon can be $leq 1%$ of the incident $bar{ u}_e$ energy above the W boson production threshold. The differential energy spectrum for the final state hard photon is calculated. We also discuss implications of our results for the prospective search of high-energy $bar{ u}_e$ through this final state hard photon.
We calculate the Doppler broadening of the $W^-$ resonance produced in $bar{ u}_e e^-$ collisions of cosmic anti-neutrinos with $E_{ u}approx 6.3 PeV$ with electrons in atoms up to Iron. Revisiting this issue is prompted by recent observations of PeV neutrinos by Ice-Cube. Despite its poor energy resolution, the $20%$ Doppler broadening of the resonance due to electronic motions can produce observable effects via non-linear neutrino absorption near the resonance. The attendant suppression of the peak cross section allows $bar{ u}_e$ to travel correspondingly longer distances. While this effect is unlikely to be directly detected in the near future, it may facilitate terrestrial tomography at depths of $sim 10 km$, complementing deeper explorations using the more frequent nuclear interactions at lower energies.
The processes of neutrino production of electron-positron pairs, $ u bar u to e^- e^+$ and $ u to u e^- e^+$, in a magnetic field of arbitrary strength, where electrons and positrons can be created in the states corresponding to excited Landau levels, are analysed. The results can be applied for calculating the efficiency of the electron-positron plasma production by neutrinos in the conditions of the Kerr black hole accretion disc considered by experts as the most possible source of a short cosmological gamma burst.
Using a sample of 225.3 million $jpsi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider in 2009, searches for the decays of $eta$ and $eta^primetopi^+ e^- bar{ u}_e +c.c.$ in $jpsi to phi eta$ and $phieta^prime$ are performed. The $phi$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag $eta$ and $eta^prime$ semileptonic decays. No signals are observed for either $eta$ or $eta^prime$, and upper limits at the 90% confidence level are determined to be $7.3times 10^{-4}$ and $5.0times 10^{-4}$ for the ratios $frac{{mathcal B}(etato pi^+ e^- bar{ u}_e +c.c.)}{{mathcal B}(eta to pippimpiz)}$ and $frac{{mathcal B}(eta^primeto pi^+ e^-bar{ u}_e +c.c.)}{{mathcal B}(eta^prime to pippimeta)}$, respectively. These are the first upper limit values determined for $eta$ and $eta^prime$ semileptonic weak decays.
We examine the muonium ($mu ^+e^-$)-antimuonium ($mu ^-e^+$) system in the models which accomodate the dilepton gauge bosons, and study their contributions to the ground state hyperfine splitting in ``muonium. We also consider the exotic muon decay $mu ^+to e^+ +overline u _e + u _{mu}$ mediated by the dilepton gauge boson, and obtain a lower bound $(M_{X^{pm }}/g_{3l})>550 rm GeV$ at 90% confidence level for the singly-charged dilepton mass using the unitarity relation of the Kobayashi-Maskawa matrix for the 3-family case.
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