Experiments by a group of physicists from the Technical University of Munich (TUM) have shown that a particle made up of four neutrons could very well exist. The study was carried out at the accelerator laboratory at the Garching Research Campus.
In their experiment, physicists bombarded a target made of lithium-7, accelerating its particles to about 12% of the speed of light. This reaction should generate carbon-10 and tetraneutron. The results are in line with physicists’ expectations: by repeating the same task, they can detect a tetraneutron.
Almost two decades ago, a group of French scientists reported the possibility of the existence and even fixation of the demanded tetraneutron. However, later work by other groups showed that the methodology used could not prove the existence of a tetraneutron.
In 2016, a group of scientists from Japan bombarded a target with helium-4 with a beam of radioactive particles of helium-8 to obtain tetraneutrons from helium-4. This reaction should have produced beryllium-8.
They managed to find four such atoms. According to the results of measurements, physicists confirmed that the tetraneutron was not a bound particle and quickly decayed into four neutrons.
In a new study, measurements have shown that the tetraneutron will be about as stable as the neutron itself. It would then decay by beta decay with a half-life of 450 seconds.
Moreover, the group’s measurements matched the signature one would expect from carbon-10 in its first excited state and a tetraneutron associated with a voltage of 0.42 megaelectronvolts (MeV). With these measurements, the team achieved a confidence level greater than 99.7% or three sigma.
Dr. Thomas Festermann said: “For us, this is the only physically plausible explanation for the measured values in every respect.”
But in physics, the existence of a particle is considered definitively proven only after 5 sigma confidence has been achieved. The team is looking forward to independent confirmation.