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Lesya Shchutska wants to prove the existence of heavy neutrinos

Search for a hidden world

Lesya Shchutska (pronounced: Schutska) is 33 years old and already Professor of Elementary Particle Physics at the Swiss Federal Institute of Technology Lausanne (EPFL). "At the moment I can't imagine doing anything other than physics," says the researcher, who deals with particles that so far only exist in the minds of theoretical physicists.

In addition to teaching and research, the 33-year-old scientist knows how to make complex issues comprehensible to a broad audience in a simple language - for example, at continuing education events for teachers or at the EPFL Open Day. Photo: B. Vogel
Image: CHIPP, Switzerland

It was in February 2018 when Lesya Shchutska was invited by the EPFL to an interview for a free professorship. The scientist was pregnant, and the interview proposed by the university fell pretty much on the day of the planned delivery. "Of course," says the 33-year-old researcher, "that wasn't possible, so the people from the university found a solution and suggested another date; I'm very grateful to them for that." Now Professor Shchutska is sitting in a soberly furnished room at EPFL, a provisional accommodation until she can move into her own office next year. Her daughter is now one and a half years old. The scientist brings both under one hat, child and career - thanks to the crèche that the EPFL offers for its staff and thanks to the support of her husband, a physicist himself.

Lesya - we speak English, so we call each other by our first names - is a bundle of energy. The sentences come over her lips so quickly that the listener has to put all his concentration together to follow her thoughts. The American colouring of her English reveals something of her time as a postdoc: from 2012 to 2017 she worked at CERN in Geneva in the research group of the University of Florida. "The Americans are tough and result-oriented," says Lesya. There is no doubt that these are qualities that she herself values and that correspond perfectly to her personal working style.

Evidence of heavy neutrinos

Lesya is a scientific talent - this proves her fast career. When she talks about her current research, one suspects something of the originality of her thinking, even if they are difficult topics that a non-physicist finds difficult to grasp. The starting point of her work is the theory of the existence of heavy neutrinos. Mikhail Shaposhnikov, a theoretical physicist from Russia who is a prominent professor at EPFL, postulated the existence of heavy neutrinos with a particular mass configuration in 2005 (the lightest one in the keV range, the two heavier ones in the GeV range). Unlike the 'normal' three neutrinos, the elementary particles have not yet been experimentally proven. Exactly this proof is the task Lesya has been working on in recent years and on which she continues to work.

When Lesya wants to talk about her research, she shoots up from her office chair, stands by the whiteboard and gives a small, easily comprehensible lecture: She starts with the three known neutrinos, the electron neutrino, the muon neutrino and the tau neutrino. Neutrinos were long regarded as massless. For some years it has been known that they have a mass that is, however, ten orders of magnitude smaller than the mass of their partner particles electron, muon and tau. "According to Mikhail Shaposhnikov's theory, each of the known light neutrinos has a heavy partner. We call these partners N1, N2 and N3. If these particles exist, they would be the key to solving various questions that are still unanswered today: What is dark matter made of? Why is there matter in the universe, but practically no antimatter? Why do the neutrinos known so far have such an unimaginably small mass? All these questions, says Lesya, might be answered by confirming Shaposhnikov's theory.

Alternative to the SHiP experiment

It is a fantastic perspective that Lesya sketches with a few lines on her whiteboard. If the three heavy brothers - N1, N2 and N3 - could be proved by experimental evidence, the books of modern particle physics would have to be rewritten. In recent years Lesya has been supported in her search by an ERC grant from the European Research Council (ERC). The proof has not yet been successful, but the fact that research results on the topic are already available is remarkable. For the detection of the three heavy neutrinos, the so-called SHiP experiment was to be set up at CERN in 2013. This experiment met with broad interest in the global particle physics community - including EPFL and the universities of Geneva and Zurich - but has not yet been set up for financial reasons.

Lesya was not discouraged by this setback. She found another way to search for the heavy neutrinos, using the CMS experiment, which has been running at CERN for over ten years and whose detector could possibly also detect traces of heavy neutrinos. This could happen at the moment when heavy neutrinos turn into their light brothers. Physicists call this very rare process "mixing" (not to be confused with the oscillations that light neutrinos undergo and which have been experimentally proven for years). "So far we have not proven mixing, but we have not yet evaluated all CMS data," says Lesya. "In the future, we also want to use the LHCb experiment, another CERN experiment, to search for the particles”. So the sensation could still happen.

Study at the excellent MIPT

Lesya's appointment to the EPFL in April of this year is the culmination of her scientific career. The daughter of a Ukrainian engineer and a Russian computer scientist grew up in a village in central Ukraine. At the age of nine she read a physics book. Since then she is tightly bound to sciences. When she was 16, the high school student joined the Ukrainian national team to the Physics Olympiad in Indonesia and won the bronze medal. Her mother would have preferred her daughter to become a doctor, but her father was behind her career as a physicist - he had even changed his job in order to enable Lesya to transfer to a good high school. Eventually the young woman moved to Moscow for her studies. She wanted to study physics at the Russian top university MIPT (Moscow Institute of Physics and Technology).

In 2008, after six years, Lesya obtained a master's degree in physics (specialising in particle physics). She then moved to Lausanne to the EPFL and did her doctorate under Prof. Tatsuya Nakada, where she designed a balloon experiment to explore cosmic rays. After completing her doctorate, she courageously seized every opportunity that presented itself to her: first she worked for five years as a postdoctoral fellow at the University of Florida on the CMS experiment, then from 2017 as a senior assistant in the research group of Prof. Günther Dissertori (ETH Zurich) until she was appointed professor at the EPFL in 2019.

One of the 100 most influential women

In May 2019 Lesya was awarded the 'Young Experimental Physicist Prize' by the European Physical Society. The award has not only led to friendly reactions in Lausanne, it has also made waves in the Ukrainian media, Lesya reports. One magazine promptly listed Lesya Shchutska among the 100 most influential women in Ukraine. That was certainly not wrong: as a particle physics professor at the EPFL, the scientist is to be reckoned with.

Author: Benedikt Vogel

Lesya Shchutska teaches elementary particle physics to students at the ETH Lausanne. Photo: B. Vogel
Lesya Shchutska teaches elementary particle physics to students at the ETH Lausanne. Photo: B. VogelImage: CHIPP, Switzerland


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