KamLAND

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KamLAND ( Kamioka Liquid Scintillator Antineutrino Detector ) is a Japanese neutrino experiment in a former mine near Kamioka and, like Kamiokande and its successor Super-Kamiokande, belongs to the Kamioka Observatory. It is used to observe electron antineutrinos and consists of a balloon with scintillator liquid 13 m in diameter, which is surrounded by photomultipliers

The antineutrinos are detected via

(a reaction with an energy threshold of 1.8 MeV) and the resulting positron generates a photon when the pair annihilates with an electron , which is detected by the photomultiplier. Various additional measures have been taken to eliminate the influence of cosmic rays and radioactivity from the surrounding rock, for example the balloon is in a bath of high-purity oil and there are additional Cherenkov detectors for cosmic rays.

The antineutrinos are especially generated during radioactive decay in the many surrounding Japanese nuclear reactors (their averaged distance gives an average of the base length of 180 km). The data acquisition began in 2002 and already in the first 145 days there were clear indications of neutrino oscillations , since instead of the 86.8 ± 5.6 events expected without neutrino oscillations, only 54 were counted. In 2008 and 2011 the results of precision measurements of the neutrino mixing angles (in the three neutrino model of the standard model ) and neutrino masses were published.

At KamLAND, geoneutrinos were also observed from the radioactive decay of thorium and uranium in the earth's interior and, independent of this, limits for the heat flow from the earth's interior through radioactive decay.

2011 was with xenon -filled balloon in the balloon with the liquid scintillator placed in the search for double beta decay , especially neutrinoless double beta decay, which would indicate Majorana neutrinos ( KamLAND Zen Double Beta Decay Search ). A first lower limit for the lifespan due to neutrino-free double beta decay was published in 2013 and is 1.9 · 10 25 years.

KamLand is part of the Supernova Early Warning System .

The KamLAND team received the Breakthrough Prize in Fundamental Physics in 2016 .

literature

  • Atsuto Suzuki, Antineutrino science in KamLand, Arxiv

Web links

Individual evidence

  1. ^ First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance, Phys. Rev. Lett., Vol. 90, 2003, p.021802, Arxiv
  2. ↑ S. Abe et al. a., Precision Measurement of Neutrino Oscillation Parameters with KamLAND, Physical Review Letters, Volume 100, 2008, p. 221803, PMID 18643415
  3. ↑ A. Gando et al. a., Constraints on θ13 from A Three-Flavor Oscillation Analysis of Reactor Antineutrinos at KamLAND, Physical Review D, Volume 83, 2011, p. 052002, Arxiv
  4. ↑ T. Araki et al. a., Experimental investigation of geologically produced antineutrinos with KamLAND, Nature, Volume 436, 2005, pp. 499-503.
  5. ↑ A. Gando et al. a. Partial radiogenic heat model for Earth revealed by geoneutrino measurements, Nature Geoscience, Volume 4, 2011, pp. 647-651
  6. ↑ A. Gando et al. a., Limit on Neutrinoless ββ Decay of 136Xe from the First Phase of KamLAND-Zen and Comparison with the Positive Claim in 76Ge, Physical Review Letters, Volume 110, 2013, p. 062502, Arxiv