Neutrino-2008: Where are we? Where are we going?

Abstract

Our present knowledge of neutrinos can be summarized in terms of the "standard neutrino scenario". Phenomenology of this scenario as well as attempts to uncover physics behind neutrino mass and mixing are described. Goals of future studies include complete reconstruction of the neutrino mass and flavor spectrum, further test of the standard scenario and search for new physics beyond it. Developments of new experimental techniques may lead to construction of new neutrino detectors from table-top to multi-Megaton scales which will open new horizons in the field. With detection of neutrino bursts from the Galactic supernova and high energy cosmic neutrinos neutrino astrophysics will enter qualitatively new phase. Neutrinos and LHC (and future colliders), neutrino astronomy, neutrino structure of the Universe, and probably, neutrino technologies will be among leading topics of research. 1978 -Wolfenstein: "Neutrino oscillations in matter". 1988 -Kamiokande-II: the birth of the atmospheric neutrino problem 3 . 1998 -Discovery of oscillations in atmospheric neutrinos. 2008 -Discovery of New Zealand by the neutrino community; the start of LHC. Where are we in space? -about 5000 km (baseline) from IceCube in 3D, somewhere in the electroweak brane, in extra D...Where are we in the field of neutrino physics? The answer includes: "conquest territory"the standard neutrino scenario (sec. 2); understanding neutrino masses and mixing (sec. 3); beyond the standard scenario (sec 4); a future which we know (sec. 5); a future which we can only imagine (sec. 6). Standard neutrino scenario2.1. Standard scenario "Standard neutrino scenario" can be formulated in the following way:• Neutrino interactions are described by the standard electroweak model. • There are only 3 types of light neutrinos (three flavor and three mass states).• Neutrinos are massive. Neutrino masses are in the sub-eV range -much smaller than masses of charged leptons and quarks. • Neutrinos mix. There are two large mixing angles and one small or zero angle. The pattern of lepton mixing strongly differs from that of quarks. • The observed masses and mixing have pure vacuum origin; they are generated at the electroweak, and probably, higher energy scales. These are "hard" masses.3 L. Sulak has informed me on some earlier indications of the anomaly in the IMB results.

Neutrinos: Projecting onto the Future

“…Possible solutions are (i) very light sterile neutrino whose parameters can be adjusted in such a way that it can produce a dip in the ν e survival probability at 3 MeV, and (ii) nonstandard interactions (NSI). Recall that the survival probability P ee obeys scaling: It depends on the combination ∆m 2 12 /V , and no distance is involved. So, increase of V by factor 1.6 (which can be due to contribution of the diagonal NSI,…”

“…Even more exotic explanation is related to non-local interactions in the ν− portal which leads to CPT violation and shows up as ν −ν mass splitting [18]. Surprisingly the expected mass difference is just what is needed to reconcile the solar (neutrino) and the KamLAND (antineutrino) values of ∆m 2 21 . Projecting to the far future one can imagine that exploration of oscillations of Be neutrinos in the Earth may become possible [19].…”

“…[2] summarizing situation in 2008 and trying to extrapolate it to the future. Reading the paper in proceedings [2] is nice way to check if I can trust myself. Well, various statements made in 2008 are still valid.…”

Sudbury Neutrino Observatory: Latest results and future prospects

“…SNO was sensitive to neutrinos produced by 8 B decays, socalled 8 B neutrinos, and by the reaction, 3 He + p → 4 He + ν e ,…”

“…Also, a precise measurement of θ 12 and θ 13 could distinguish various hypotheses for neutrino oscillations [3].…”