Perturbing neutrino oscillations around the solar resonance

Journal Article · 29 July 2019 · Progress of Theoretical and Experimental Physics

DOI: https://doi.org/10.1093/ptep/ptz067 · OSTI ID:1545096

Martinez-Soler, Ivan ^[1]; Minakata, Hisakazu ^[2]

---

1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States). Theoretical Physics Dept.; Northwestern Univ., Evanston, IL (United States). Dept. of Physics and Astronomy; Colegio de Física Fundamental e Interdisciplinaria de las Américas (COFI), San Juan (Puerto Rico)
2. Virginia Tech, Blacksburg, VA (United States). Dept. of Physics, Center for Neutrino Physics; Univ. of Tokyo, Kashiwa, Chiba (Japan). Inst. for Cosmic Ray Research, Research Center for Cosmic Neutrinos

Atmospheric neutrinos at low energies, $$E \lesssim 500$$ MeV, are known to be a rich source of information on lepton mixing parameters. We formulate a simple perturbative framework to elucidate the characteristic features of neutrino oscillation at around the solar-scale enhancement due to the matter effect. The clearest message that we could extract from our perturbation theory is that CP violation in the appearance oscillation probability is large, a factor of $$\sim 10$$ times larger than CP violation at around the atmospheric-scale oscillation maximum. The underlying mechanism for this is that one of the suppression factors on the CP phase-dependent terms due to the smallness of $$\Delta m^2_{21} / \Delta m^2_{31}$$ is dynamically lifted by the solar-scale enhancement. Our framework has a unique feature as a perturbation theory in which a large $$\Delta m^2_{31}$$ term outside the key 1-2 sector for the solar-scale resonance does not yield sizable corrections. On the contrary, the larger the $$\Delta m^2_{31}$$, the smaller the higher-order corrections.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: AC02-07CH11359
• OSTI ID: 1545096
• Report Number(s): arXiv:1904.07853; FERMILAB-PUB-19-149-T; NUHEP-TH/19-05; 1730033
• Journal Information: Progress of Theoretical and Experimental Physics, Vol. 2019, Issue 7; ISSN 2050-3911
• Publisher: Physical Society of JapanCopyright Statement
• Country of Publication: United States
• Language: English