Lepton-flavor Violation at Future Lepton Colliders and the Atmospheric Neutrino Oscillation

Abstract

It can be expected from the result for the atmospheric neutrino by the SUPERKAMIOKANDE and the CHOOZ result that the the lepton-flavor violating (LFV) interaction between the second and third generations exits at the high energy scale. This leads to a non-vanishing LFV left-handed slepton mass between the second and third generations, induced by the radiative correction, in the minimal supergravity scenario. In this article, assuming that the supersymmetric standard model with the right-handed neutrinos explains the atmospheric neutrino result, we show that the reach of the LFV slepton production in the future lepton colliders can be more significant than that of τ → μγ. 1 Talk given at 34th Rencontres de Moriond: Electroweak Interactions and Unified Theories, Les Arcs, France, 13-20 Mar 1999. The lepton-flavor violation (LFV) is one of the characteristic signatures in the supersymmetric (SUSY) extension of the Standard Model (SM). Introduction of supersymmetry to the SM is one of the promising idea beyond the SM, since it is a solution of the naturalness problem associated with the Higgs boson mass, as well-known. In order to make this model phenomenologically viable, we have to introduce the SUSY breaking terms. This may lead to the LFV by the gaps between the mass bases of sleptons and of leptons. In the minimal supergravity scenario, which is the one of the candidates of the generation mechanism of the SUSY breaking in the SUSY SM, the magnitude of the LFV depends on the high energy physics beyond the SUSY SM. In this scenario, the slepton masses are degenerate and the lepton flavor is conserved at the tree level. However, if the LFV interaction at the high energy scale, such as the Yukawa interaction of the righthanded neutrinos, exits, the radiative correction to the slepton masses is lepton-flavor violating [1, 2]. The SUPERKAMIOKANDE provided the convincing result for the atmospheric neutrino anomaly, and showed that it comes from the neutrino oscillation [3]. Combined with the CHOOZ experiment [4], it is natural to consider that the oscillation is between the muon and the tau neutrinos, and ∆m2νμντ ≃ (5× 10 − 6× 10)eV, sin 2θνμντ > 0.82. (1) This means that the LFV interaction, such as the Yukawa coupling of the right-handed neutrino in the see-saw mechanism [5], exits in order to generate the small neutrino masses, and that the LFV between the second and the third generations in the slepton mass matrix is generated in the minimal supergravity scenario. The ways to study the LFV between the second and third generations in the SUSY SM are i) the LFV radiative processes such as τ → μγ and ii) the LFV slepton production processes in the future colliders with the signal τμX 6 E [6, 7]. In this article we compare the reach of the LFV slepton production in the future lepton colliders with that of τ → μγ, assuming that the SUSY SM with the right-handed neutrinos explains the atmospheric neutrino result. Due to low statistics of the τ → μγ experiments and the weak GIM suppressions in the LFV production processes of slepton, search for the LFV slepton production in the future lepton colliders can be more significant than the future

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Cite this paper

@inproceedings{Hisano1999LeptonflavorVA, title={Lepton-flavor Violation at Future Lepton Colliders and the Atmospheric Neutrino Oscillation}, author={Junji Hisano}, year={1999} }