Dodi Irawan
ROME — Seventy years have passed since one of the most revolutionary discoveries in the history of physics: the detection of the neutrino particle. This discovery, which fundamentally changed our understanding of the universe, still harbors profound mysteries in 2026, especially concerning its mass. Professor Gianpaolo Pallavicini from the Italian National Institute for Nuclear Physics (INFN) asserts, "There are still many unresolved mysteries, such as that of its mass."
The concept of the neutrino was first hypothesized by Wolfgang Pauli in 1930 to explain anomalies in beta decay, a radioactive process. Pauli referred to it as a "small neutral particle," later named "neutrino" by Enrico Fermi. For many years, the existence of this particle remained purely theoretical, challenging scientists to prove it.
The major breakthrough arrived in 1956. Clyde Cowan and Frederick Reines, two American physicists, successfully detected neutrinos through their iconic Reines-Cowan experiment near the Savannah River nuclear reactor in the United States. This discovery validated Pauli's hypothesis and opened a new chapter in particle physics.
The detection of neutrinos proved the existence of particles that interact very weakly with matter, earning them the moniker "ghost particles" due to their almost undetectable nature. Their presence forced physicists to revise and enrich the Standard Model of particle physics, a theoretical framework explaining all fundamental particles and their interacting forces.
Although the initial Standard Model assumed neutrinos were massless, further observations revealed that neutrinos undergo oscillation, a phenomenon only possible if they possess mass. This remains one of the greatest puzzles in modern physics.
The mystery of neutrino mass is not a minor detail. Understanding neutrino mass has the potential to uncover new physics beyond the Standard Model. It could provide crucial clues about the nature of dark matter and dark energy that dominate the universe, or even why there is more matter than antimatter.
Scientists worldwide continue to conduct extensive research to measure neutrino mass and understand its properties. Giant projects such as Super-Kamiokande in Japan, the IceCube Neutrino Observatory in Antarctica, and KATRIN in Germany are some examples of these collective efforts.
ITALY, through the Istituto Nazionale di Fisica Nucleare (INFN), plays a central role in this global endeavor. INFN is involved in various international neutrino experiments, including the Gran Sasso underground laboratory, which hosts major experiments like Borexino and GERDA, aiming to delve deeper into the nature of these particles.
Professor Pallavicini of INFN adds, "The absence of neutrino mass in the Standard Model is one of its biggest weaknesses. Determining this mass will not only fill that gap but also open a window to entirely new physics, perhaps related to grand unified theories."
Capturing and studying neutrinos presents significant challenges. Due to their extremely weak interaction, trillions of neutrinos pass through our bodies every second without leaving a trace. Neutrino observatories are often built deep underground or beneath thick ice to shield detectors from cosmic radiation and enable the detection of these incredibly rare particles.
The implications of discovering neutrino mass extend into the field of cosmology. If neutrinos possess mass, however small, their immense abundance in the universe means they could contribute to the universe's total mass, influencing the formation of large-scale cosmic structures.
As its 70th anniversary is commemorated in 2026, the neutrino remains one of the most fascinating and enigmatic subjects of study in physics. Its journey from a hypothetical particle to a key player in the Standard Model, and now as a gateway to new physics, affirms that the universe still holds many secrets waiting to be unveiled.
