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Yuichi Uesaka

Publications and source records attributed to Yuichi Uesaka.

21 records · Page 2Linked to original sources

Higgs mediated CLFV processes $μN(eN)\rightarrowτX$ via gluon operators

We revisit charged lepton flavor violating (CLFV) scattering processes $\ell_{i} N \to τX \, (\ell_{i} \ni e, μ)$ mediated by Higgs. We point out that a new subprocess $\ell_{i} g \to τg$ via the effective interactions of Higgs and gluon gives the dominant contribution to $\ell_{i} N \to τX$ for an incident beam energy of $E_{\ell} \lesssim 1\,\text{TeV}$ in fixed target experiments. Furthermore, in the light of quark number conservation, we consider quark pair-production processes $\ell_{i} g \to τq \bar{q}$ ($q$ denotes quarks) instead of $\ell_{i} q \to τq$. This corrects the threshold energy of each subprocess contributing to $σ(\ell_{i} N \to τX)$. Reevaluation of $σ(\ell_{i} N \to τX)$ including all of relevant subprocesses shows that the search for $\ell_{i} N \to τX$ could serve a complementary opportunity with other relevant processes to shed light on the Higgs CLFV.

hep-ph↗

Improved analyses for $μ^-e^-\rightarrow e^-e^-$ in muonic atoms by contact interactions

The charged lepton flavor violating (CLFV) processes of $μ^-e^-\rightarrow e^-e^-$ decay by four Fermi contact interactions in a muonic atom for various atoms are investigated. The wave functions of bound and scattering state leptons are properly treated by solving Dirac equations with Coulomb interaction of the finite nuclear charge distributions. This new effect contributes significantly in particular for heavier atoms, where the obtained decay rate is about one order of magnitude larger than the previous estimation for $^{208}$Pb. We find that, as the atomic number $Z$ increases, the $μ^-e^-\rightarrow e^-e^-$ decay rates increase more rapidly than the result of the previous work of $Z^3$, suggesting this decay as one of the promising processes to search for CLFV interaction.

hep-ph↗

Improved analysis of the CLFV decay of muonic atoms $μ^-e^-\rightarrow e^-e^-$

Koike et al. proposed the charged lepton flavor violation (CLFV) decay of the muonic atom $μ^-e^-\rightarrow e^-e^-$ as one of the promising processes to search for new physics beyond the standard model. It was found that the attractive interaction of leptons with the nucleus enhances the transition rate of the $μ^-e^-\rightarrow e^-e^-$ process. We report on our improved analysis of this process by taking into account the distortion of the out-going electrons in the nuclear Coulomb potential and the relativistic treatment of the muon and the electrons. As results, we found significant enhancement of the transition rate. The transition rate for $^{208}$Pb becomes about 7 times larger than the previous estimation, which enhances the sensitivity of this process to discover the CLFV interaction. We also report on the energy spectrum of the out-going electron.

hep-ph↗