QUANTUM MECHANICS

Quantum Mechanics



Quantum Mechanics

Introduction

The signal theory of light, and in specific the principle of interference, was formulated by Thomas juvenile in 1801. In the 20th century, the principle of interference was extended to the quantum mechanical signal functions describing matter. The occurrence of quantum mechanical interference of distinct neutrino states, neutrino oscillations, has provided one of the most stimulating developments in high energy element physics of the last decade. Observations of the flavour oscillations of neutrinos made by distant causes, such as from the core of the Sun, provide convincing evidence that neutrinos have mass. This item recounts the major characteristics and the most significant untested facts of this unusual submission of the principle of interference.

The fields of nuclear and particle physics commenced with the discovery of the radioactivity of uranium (Becquerel 1896). Within 10 years three distinct types of radioactive decays were isolated, a-, (- and y-rays. The decay products were soon identified as 4He nuclei, electrons and photons, respectively. Since a radioactive decay corresponds to a transition between two particular nuclear states, the energy released is fixed. Consequently, in a- and y-decays the 4He nuclei and the photons are produced mono-energetically. By contrast, the energy spectrum of P-decays was shown to be continuous (Chadwick 1914).

Although the success of the Fermi theory of P-decay provided strong evidence for the existence of the neutrino, it was not until much later that the neutrino was observed directly. Neutrinos experience neither the electromagnetic force nor the nuclear strong force, and interact only via the aptly named weak force. The weakness of this force means that for neutrinos emitted in P-decay, the mean free path in water is about 50 light-years. The 20-year gap between the proposal and discovery of the neutrino was due to the inherent difficulties of neutrino detection which requires both an intense neutrino source and a large mass detector. In the first direct observation of the neutrino (Reines & Cowan 1956, 66), neutrinos from a reactor source (1013 Ve cm-2 s-1) were detected by the inverse P-decay reaction,

Ve +p -+ n+ e+.

This observation demonstrated the existence of the neutrino and opened up a new area of study in particle physics. Until recently it was broadly assumed that neutrinos were massless. However, in 1998 the Super-Kamiokande experiment published compelling evidence that muon neutrinos produced in the atmosphere were oscillating into tau neutrinos (Fukada et al. 1998c, 1254). The almost inescapable implication is that neutrinos have a small but non-zero mass. The unconfirmed results of the LSND trial (Aguilar et al. 2001, 663) are not considered here.

Observations

The behaviour of this scheme can be appreciated by looking at its usual modes of oscillation. If the two pendulums are equal then one usual mode comprises of both pendulums wavering in the identical main heading with a unchanging expanse between them, while the other comprises of the pendulums wavering in converse (mirror image) directions. These usual modes have (slightly) distinct frequencies because the second engages the (weak) jump while the ...