Neutrinos, fundamental particles in physics, have been found to be larger than previously thought. A team led by Joseph Smolsky at the Colorado School of Mines has made the first direct measurement of a neutrino’s wave packet, finding that it must be at least hundreds of times larger than an atomic nucleus.
Unlike spheres, particles are inherently fuzzy waves in quantum mechanics. Physicists measure a particle’s size by looking for its wave packet – a region where the wave vibrates strongly and beyond which it sharply trails off. However, measuring this for neutrinos is challenging due to their infrequent interactions with normal matter.
Smolsky’s team measured radioactive beryllium as it decayed into lithium using a particle accelerator. By studying the lithium atoms precisely and analyzing the energy released during the process, they inferred the properties of the neutrino. The measurement reveals that neutrinos are at least 6.2 picometres in size – far larger than an atomic nucleus.
The result was surprising to some scientists, as it suggests that the neutrino’s wave packet is much larger than the nuclear structure itself. This finding has significant implications for building future neutrino detectors capable of precise measurements of neutrino oscillations.
Oscillations are crucial in understanding why there is more matter than antimatter in the universe. However, if the neutrino is too small, its wave packet would overlap with different types of neutrinos, resulting in inaccurate measurements. The direct measurement by Smolsky’s team brings us closer to resolving this issue and unlocking the secrets of neutrino physics.
Source: https://www.newscientist.com/article/2468207-how-big-is-a-neutrino-were-finally-starting-to-get-an-answer