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Published online: 25 February 2009 | doi:10.1038/nchina.2009.36

Nuclear physics: A massive problem

Tim Reid

Introduction

The neutrino is possibly the most difficult elementary particle to detect, but scientists have devised ingenious ways to study it. Liang Zhan and co-workers at the Chinese Academy of Sciences in Beijing¹ describe a method that could answer one of the trickiest questions about the neutrino — how it gets its mass.

Neutrinos exist in three different types, or 'flavours'. It is believed that they can oscillate between all three flavours as they move through space. This quantum mechanical effect has been observed in neutrinos from the Sun, the atmosphere, nuclear reactors and particle accelerators.

The oscillation between flavours is related to the fact that the neutrino also has three possible states of mass. The puzzle that remains is to work out the neutrino 'mass hierarchy' — the order of the three mass states from lightest to heaviest. Unfortunately, many scientists predict that to observe the mass hierarchy would need impractically huge detectors separated by hundreds or thousands of kilometres.

Wen and co-workers suggest that one way to overcome this problem is to do a Fourier transform on the data, which greatly improves the detector sensitivity. Their calculations show that when a proper Fourier transform is used, a detector with mass around 10,000 tons is all that is needed to identify the mass hierarchy of neutrinos emitted from a nuclear reactor positioned 60 kilometres away.

The authors of this work are from:
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China.

Reference

1. Zhan, L., Wang, Y., Cao, J. & Wen, L. Determination of the neutrino mass hierarchy at an intermediate baseline. Phys. Rev. D doi:10.1103/PhysRevD.78.111103 (2008). | Article | ADS | ChemPort |