The inexplicable neutrino

6 October 2021

Ghost Particle screened at CineGlobe on 26 August, directed by Geneva Guerin

Francesca Stocker
Inside protoDUNE Francesca Stocker, star of Ghost Particle. Credit: Ghost Particle

Claustrophobia. South Dakota. A clattering elevator lowers a crew of hard-hat-clad physicists 1500 metres below the ground. 750,000 tonnes of rock are about to be excavated from this former gold mine at the Sanford Underground Research Facility (SURF) to accommodate the liquid-argon time projection chambers (TPCs) of the international Deep Underground Neutrino Experiment (DUNE). Towards the end of the decade, DUNE will track neutrinos that originate 1300 km away at Fermilab in Chicago, addressing leptonic CP violation as well as an ambitious research programme in astrophysics.

Having set the scene, director Geneva Guerin, co-founder of Canadian production company Cinécoop, cuts to a wide expanse: a climber scaling a rock face near the French–Swiss border. Francesca Stocker, the star of the film and then a PhD student at the University of Bern, narrates, relating the scientific method to rock climbing. Stocker and her fellow protagonists are engaging, and the film vividly captures the human spirit surrounding the birth of a modern particle-physics detector.

I don’t think it is possible to explain a neutrino for a general audience

Geneva Guerin

But the viewer is not allowed to settle for long in any one location. After zipping to CERN, and a tour through its corridors accompanied by eerie cello music, we meet Stocker in her home kitchen, explaining how she got interested in science as a child. Next, we hop to Federico Sánchez, spokesperson of the T2K experiment in Japan, explaining the basics of the Standard Model. 

Ghost Particle

T2K, and its successor Hyper-Kamiokande, DUNE’s equal in ambition and scope, both feature in the one-hour-long film. But the focus is on the development of the prototype DUNE detector modules that have been designed, built and tested at the CERN Neutrino Platform – and here the film is at its best. Guerin had full access to protoDUNE activities, allowing her to immerse the viewer with the peculiar but oddly fitting accompaniment of a solo didgeridoo inside the protoDUNE cryostat. We gatecrash celebrations when the vessel was filled with liquid argon and the first test-beam tracks were recorded. The film focuses on detailed descriptions of the workings of TPCs and other parts of the apparatus rather than accessible explanations of the neutrino’s fascinating and mysterious nature. Unformatted plots and graphics are pulled from various sources. While authentic, this gives the film an unpolished, home-made feel.

Given the density of the exposition in some parts, beyond the most enthusiastic popular-science fans, Ghost Particle seems best tailored for physics students encountering experimental neutrino physics for the first time – a point that Guerin herself made during a live Q&A following the CineGlobe screening: “I was aiming at people like me – those who love science documentaries,” she told the capacity crowd. “Originally I envisaged a three-part series over a decade or more, but I realised that I don’t think it is possible to explain a neutrino for a general audience, so maybe it’s something for educational purposes, to help future generations get introduced to this exciting programme.”

The film ends as it began, with the rickety elevator continuing its 12-minute descent into the bowels of the Earth.

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