科研之友
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摘要
Nuclear reactors are the most intense man-made source of antineutrinos, providing a useful tool for the study of these particles. Oscillation due to the neutrino mixing angle theta(13) is revealed by the disappearance of reactor (nu) over bar (e) over similar to km distances. Use of additional identical detectors located near nuclear reactors reduce systematic uncertainties related to reactor (nu) over bar (e) emission and detector efficiency, significantly improving the sensitivity of oscillation measurements. The Double Chooz, RENO, and Daya Bay experiments set out in search of theta(13) using these techniques. All three experiments have recently observed reactor (nu) over bar (e) disappearance, and have estimated values for theta(13) of 9.3 degrees +/- 2.1 degrees, 9.2 degrees +/- 0.9 degrees, and 8.7 degrees +/- 0.4 degrees respectively. The energy-dependence of (nu) over bar (e) disappearance has also allowed measurement of the effective neutrino mass difference, \Delta m(ee)(2)\ approximate to \Delta m(31)(2)\. Comparison with \Delta m(mu mu)(2)\ approximate to \Delta m(32)(2)\ from accelerator nu(mu) measurements supports the three-flavor model of neutrino oscillation. The current generation of reactor (nu) over bar (e) experiments are expected to reach similar to 3% precision in both theta(13) and \Delta m(ee)(2)\. Precise knowledge of these parameters aids interpretation of planned nu(mu) measurements, and allows future experiments to probe the neutrino mass hierarchy and possible CP-violation in neutrino oscillation. Absolute measurements of the energy spectra of (nu) over bar (e) deviate from existing models of reactor emission, particularly in the range of 5-7 MeV.
- 出版日期2015-2-4
