Solar neutrino problem

Summary

The solar neutrino problem concerned a large discrepancy between the flux of solar neutrinos as predicted from the Sun's luminosity and as measured directly. The discrepancy was first observed in the mid-1960s and was resolved around 2002. The flux of neutrinos at Earth is several tens of billions per square centimetre per second, mostly from the Sun's core. They are nevertheless hard to detect, because they interact very weakly with matter, traversing the whole Earth. Of the three types (flavors) of neutrinos known in the Standard Model of particle physics, the Sun produces only electron neutrinos. When neutrino detectors became sensitive enough to measure the flow of electron neutrinos from the Sun, the number detected was much lower than predicted. In various experiments, the number deficit was between one half and two thirds. Particle physicists knew that a mechanism, discussed back in 1957 by Bruno Pontecorvo, could explain the deficit in electron neutrinos. However, they hesit

Official source

https://en.wikipedia.org/wiki/Solar_neutrino_problem

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This course presents the physical principles and the recent research developments on three topics of particle and nuclear physics: the physics of neutrinos, dark matter, and plasmas of quarks and gluons. An emphasis is given on experimental aspects in these three research fields.

We present the role of particle physics in cosmology and in the description of astrophysical phenomena. We also present the methods and technologies for the observation of cosmic particles.

Presentation of the electroweak and strong interaction theories that constitute the Standard Model of particle physics. The course also discusses the new theories proposed to solve the problems of the Standard Model.

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Viability of Dirac phase leptogenesis

Steve Blanchet

We discuss the conditions for a non-vanishing Dirac phase delta and mixing angle theta(13), sources of CP violation in neutrino oscillations, to be uniquely responsible for the observed matter - antimatter asymmetry of the Universe through leptogenesis. We show that this scenario, that we call delta-leptogenesis, is viable when the degenerate limit for the heavy right-handed (RH) neutrino spectrum is considered. We derive an interesting joint condition on sin theta(13) and the absolute neutrino mass scale that can be tested in future neutrino oscillation experiments. In the limit of the hierarchical heavy RH neutrino spectrum, we strengthen the previous result that delta-leptogenesis is only very marginally allowed, even when the production from the two heavier RH neutrinos is taken into account. An improved experimental upper bound on sin theta(13) and/or an account of quantum kinetic effects could completely rule out this option in the future. Therefore, delta-leptogenesis can be also regarded as motivation for models with degenerate heavy neutrino spectrum.

2008

Search for ultra-high-energy neutrinos with AMANDA-II

Xiaoxia Bai, Levent Demirörs, Mathieu Ribordy, Yi Wang

A search for diffuse neutrinos with energies in excess of 105 GeV is conducted with AMANDA-II data recorded between 2000 and 2002. Above 107 GeV, the Earth is essentially opaque to neutrinos. This fact, combined with the limited overburden of the AMANDA-II detector (roughly 1.5 km), concentrates these ultra-high-energy neutrinos at the horizon. The primary background for this analysis is bundles of downgoing, high-energy muons from the interaction of cosmic rays in the atmosphere. No statistically significant excess above the expected background is seen in the data, and an upper limit is set on the diffuse all-flavor neutrino flux of E2Φ 90%Cl < 2.7 × 10-7 GeV cm-2 s -1 sr-1 valid over the energy range of 2 × 10 5 to 109 GeV. A number of models that predict neutrino fluxes from active galactic nuclei are excluded at the 90% confidence level. © 2008. The American Astronomical Society. All rights reserved.

2008

The muon and anti-muon neutrino energy spectrum is determined from 2000-2003 AMANDA telescope data using regularised unfolding. This is the first measurement of atmospheric neutrinos in the energy range 2-200 TeV. The result is compared to different atmospheric neutrino models and it is compatible with the atmospheric neutrinos from pion and kaon decays. No significant contribution from charm had-ron decays or extraterrestrial neutrinos is detected. The capabilities to improve the measurement of the neutrino spectrum with the successor experiment IceCube are discussed. (c) 2010 Elsevier B.V. All rights reserved.

2010