Joint Laboratory Seminar

Date and Time: Thursday, 21 June 2018, at 3:00 PM

Venue: Blokhintsev Hall (4th floor), Bogoliubov Laboratory of Theoretical Physics

Seminar topic: «Reactor neutrino anomalies»

Speaker: Vogel P. (Caltech, USA)

Abstract:

In the last twenty years several neutrino anomalies were observed. They include experimental results involving disappearance of neutrons of a certain flavor, or appearance of neutrons of a different flavor, which do not fit into the standard three neutrino flavor scenario. Their common characteristic feature is that L/E_v ~ 1m/MeV, perhaps implying existence of additional, sterile, neutrinos with mass of ~ 1eV. I will discuss, in detail, the anomalies involving the nuclear reactor neutrinos. Two of them have been experimentally firmly established: the total rate of the detection reaction v_e+p → e⁺+n is about 6% lower than expectation at alll distances from the reactor explored so far, and there is a shoulder (so-called “bump”) at ~ 5MeV of the neutrino energy, that is also unexpected. However, these features depend on the assumed reactor v_e spectrum. I will describe how the spectrum is evaluated, and discuss its uncertainties. The most recent results, based on the very short baseline experiments, NEOS, 24 m from the reactor core and DANSS, (12.7+10.7) m, are essentially model independent and suggest that △m²₄₁ ≈ 1.3 eV² and sin²2θ_ee ≈ 0.04, a ~ 3,5 σ effect. I will discuss how these latest results fit with the previous ones. The story is not over as yet.

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