Tetraneutron
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A tetraneutron is a hypothesised stable cluster of four neutrons. This cluster of particles is not supported by the current standard model of particle physics. However, there is some empirical evidence which suggests this particle does exist, based on an experiment by Francisco-Miguel Marqués at the Ganil accelerator in Caen based on observations of the disintegration of beryllium-14 nuclei.
This is a potentially significant discovery because the current standard model theory suggests that these clusters should not be stable, and thus should not exist. Therefore, if the existence of stable tetraneutrons can be independently confirmed, adjustments will have to be made to current physical theories.
Marqués Experiment
As with many particle accelerator experiments, Marques' team fired atomic nuculei at one another and observed the 'spray' of particles from the resulting collisions. In this case the experiment involved firing beryllium-14 nuclei at a small carbon target. The standard model theory suggests that four separate neutrons should result, but what was observed via their detectors was only one flash of light. The energy of this flash suggests that the four neutrons were fused together into a tetraneutron.
Another possible explanation for this one flash observation is that the four neutrons happened to hit the same place at the same time in the detector. Although possible, this explanation is extremely low in probability.
The standard model and the tetraneutron
It has been stated that the standard model cannot account for this particle, which is so because of the Pauli exclusion principle. This principle states that no two particles (protons, neutrons, electrons) in the same system can have identical quantum properties (such as spin).
External links
- Announcement of possible tetraneutron observations (http://www.cnrs.fr/cw/en/pres/compress/noyau.htm)
- Article showing why tetraneutrons should not exist, given current theory (http://arxiv.org/abs/nucl-th/0203003)