Abstract
We study the Lepton Flavor Violating (LFV) $e(\mu)-\tau$ conversion in Deep Inelastic Scattering (DIS) of electron (muon) on fixed-target nuclei. Our model-independent analysis is based on the set of the low-energy effective four-fermion LFV operators composed of leptons and quarks with the corresponding mass scales $\Lambda_{k}$ for each operator. Using the estimated sensitivity of the search for this LFV process in events with large missing energy in the NA64 experiment at the CERN SPS, we derive lower limits for $\Lambda_{k}$ and compared them with the corresponding limits existing in the literature. We show that the DIS $e(\mu)-\tau$ conversion is able to provide a plenty of new limits as yet non-existing in the literature. We also analyzed the energy spectrum of the final-state $\tau$ and discussed viability of the observation of this process in the NA64 experiment and ones akin to it. The case of polarized beams and targets is also discussed.
Highlights
The lepton flavor violation (LFV) is absent in the standard model (SM), if neutrinos are massless
Using the estimated sensitivity of the search for this lepton flavor violating (LFV) process in events with large missing energy in the NA64 experiment at the CERN SPS, we derive lower limits for Λk and compared them with the corresponding limits existing in the literature
We derive limits on the mass scales Λ of the LFV operators in Eqs. (5)–(7) and compare them with the corresponding limits existing in the literature
Summary
The lepton flavor violation (LFV) is absent in the standard model (SM), if neutrinos are massless. The experiment will build and operate a fully hermetic detector placed on the H4 beam line at the CERN SPS with the primary goal to search for light dark photon (A0) coupled to photon, e.g., dark photons (A0), or sub-GeV dark gauge boson Z0 coupled only to quarks or only to charged leptons. The NA64 experiment is capable for study lepton conversion in the inclusive scattering of electrons or muons on nuclei e−ðμ−Þ þ ðA; ZÞ → τ− þ X. For study of the μ − τ conversion it is planned to use the 150 GeV muon beam from the M2 beamline with the muon intensity ≃2 × 109 per SPS spill and intesity of 1013 protons on target
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have