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Two internships in Japan to advance neutrino detection

On the occasion of the Autumn Meeting of the Physical Society of Japan, a student of l’X presented research work from two end-of-studies internships on neutrino detection. This conference on particle physics and cosmic rays was held September 14-17 at Shinshu University.

Pierre Goux, X2015,  and Franz Glessgen, student in High Energy Physics at l’ENSTA ParisTech, did their six-month end-of-studies internship      at Okayama University, Japan to study gadolinium, a chemical component that will be added to the huge neutrino detector Super-Kamiokande for cosmological studies. The research was presented by Pierre Goux at the Fall Meeting of the Physical Society of Japan (JPS 2018) held September 14-17 at Shinshu University.

Detecting neutrinos with Super-Kamiokande

The purpose of the Super-Kamiokande observatory in Japan is to detect neutrinos, elementary particles that are created both in the center of our Sun and during a supernova explosion. Super-Kamiokande consists of a tank of 50,000 tons of ultrapure water covered with more than ten thousand detectors, “eyes” capable of detecting gamma rays. Neutrinos are not directly detectible. Billions pass through us every second with no impact on the matter of which we are made. But it can happen that one of these neutrinos is captured by being absorbed by a water molecule that releases a high energy “gamma” ray.

Using this enormous underground detector, researchers will soon be capable of detecting neutrinos to gain a better understanding of the rate of formation of supernovae from the Big Bang to today. It is estimated that a supernova explosion occurs every second in our universe, releasing, in the form of neutrinos, more than 10 times the energy emitted by our Sun throughout its lifetime!

Improving the detector

2018 marks a turning point for Super-Kamiokande with an experimental upgrade to improve its detection capacities. In particular, researchers are planning to introduce gadolinium, a heavy element, into the tank, which will enable it to detect “relic” neutrinos from old explosions of supernovae.

While these prospects of discovery are enticing, they required a rigorous preliminary study of gadolinium. This is what Pierre Goux and Franz Glessgen undertook during their internship in Japan under the supervision of Michel Gonin, head of the Neutrinos Group at Laboratoire Leprince-Ringuet, and Makoto Sakuda, head of the Astroparticle Physics Group at Okayama University.

They two students participated in designing an experiment to study the deexcitation of gadolinium by the emission of gamma rays and relate their findings to a conclusive theoretical interpretation. The research, presented at the JPS 2018 Meeting, makes it possible to better characterize the gamma disintegrations of gadolinium, which will be introduced late 2019 into the tank of Super-Kamiokande.

These finding will also interest scientists and doctors working on neutron capture therapies for head and neck cancer. As Pierre Goux points out: “seemingly abstract theoretical physics can have concrete applications.”