Seesaw Spectroscopy at Colliders

Abstract

A low-scale neutrino seesaw may be probed or even reconstructed at colliders provided that supersymmetry is at the weak scale and the LSP is a sterile sneutrino. Because the neutrino Yukawa couplings are small, the NLSP is typically long-lived and thus a significant fraction of colored or charged NLSPs may stop in the detector material before decaying to the LSP and a charged lepton, gauge boson, or Higgs. For two-body NLSP decays, the energy spectrum of the visible decay product exhibits a monochromatic line for each sterile sneutrino which can be used to extract the sterile sneutrino masses and some or all entries of the neutrino Yukawa matrix modulo phases. Similar methods can be used to extract these parameters from the Dalitz plot in the case of three-body NLSP decays. Assuming that the sterile sneutrino and neutrino are roughly degenerate, one can confirm the existence of a neutrino seesaw by comparing these measured parameters to the observed active neutrino masses and mixing angles. Seesaw spectroscopy can also provide genuinely new information such as the value of θ_(13), the nature of the neutrino mass hierarchy, and the presence of CP conservation in the neutrino sector. We introduce a weak-scale theory of leptogenesis that can be directly tested by these techniques.

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