3 Questions: Pinning down a neutrino’s mass

KATRIN experiment investigates the ghostly particle.

Jennifer Chu | MIT News Office
June 8, 2018

Neutrinos are everywhere, and yet their presence is rarely felt. Scientists have assumed for decades that, because they interact so little with matter, neutrinos must lack any measurable mass. But recent experiments have shown that these “ghostly” particles do in fact hold some weight. Ever since, the hunt has been on to pin down a neutrino’s mass — a vanishingly small measurement that could have huge implications for our understanding of how the universe has evolved.

Today, a major experiment has joined this fundamental search. The Karlsruhe Tritium Neutrino Experiment, or KATRIN, is a massive detector based in the town of Karlsruhe, Germany, that has been designed to measure a neutrino’s mass with far greater precision than existing experiments. At KATRIN’s heart is a 200-ton, zeppelin-like spectrometer, and scientists hope that with the experiment launching today they can start to collect data that in the next few years will give them a better idea of just how massive neutrinos can be.

Professor of physics Joseph Formaggio is part of the team of scientists that will get a first look at KATRIN’s data as they come in. Formaggio and others from MIT helped construct part of the detector’s apparatus and developed software to simulate the trajectory of particles passing through the detector. His group is now working along with a team of scientists around the world on software to analyze the data for signs of neutrino mass. MIT News sat down with Formaggio ahead of the experiment’s launch, for a chat about KATRIN and the monumental structure built to search for an infinitesimal signal.