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Kyrylo Bondarenko - The search for mysterious particles

Kyrylo Bondarenko from the Leiden Institute of Physics contributes to the search for sterile neutrino’s. These mysterious particles would explain three fundamental questions in particle physics. His predictions are currently used by a large collaboration of 52 scientific institutes. ‘If a sterile neutrino is discovered, it will significantly change our whole research area.’

The mystery of matter

Over thirteen billion years ago, the Big Bang created about ten billion times more matter than there is today. Simultaneously, it created the same staggering amount of antimatter. When the two counterparts collided, they annihilated each other into nothing. However, a slight asymmetry in the ratio between matter and antimatter caused a ten-billionth part of matter to survive. That part formed the Universe as we know it, including a species trying to explain this enigmatic asymmetry. This asymmetry is one of the big fundamental questions in particle physics, together with the nature of dark matter and the mystery behind neutrino particles oscillating among three different states.

Undiscovered particles

Particle physicists have developed the well-proven Standard Model, which amongst others classifies all known elementary particles. On top of that, they developed an additional model that solves the three problems mentioned above all at once: the Neutrino Minimal Standard Model. It predicts three undiscovered particles, called sterile neutrinos: one dark matter candidate and two particles that together are responsible for neutrino oscillations and matter-antimatter asymmetry. If scientists were to find them, it would provide strong evidence for the Neutrino Standard Model, and therefore the solution to three major scientific puzzles. That is why, during his PhD studies, physicist Kyrylo Bondarenko reviewed and revised ways to find the particles by extending the so-called intensity frontier.

Energy frontier

In the previous decades, physicists were pushing the energy frontier, meaning that they built ever bigger particle accelerators to smash particles against each other at speeds as high as possible. During a collision, the particles’ kinetic energy is converted into newly created particles. The higher the energy, the more massive particles could emerge. This way, they also created the relatively massive Higgs boson in the Large Hadron Collider at CERN.

Intensity frontier

The sterile neutrinos from the Neutrino Standard Model have been within our energy reach for decades. Yet, physicists have never seen them. This might be because they interact only feebly with other particles. When this is the case, a ridiculous number of consecutive collisions (in the order of 1020) would be needed before one particle finally emerges by sheer coincidence. Therefore, in order to find sterile neutrino’s, physicists should extend the intensity frontier by generating more collisions per second.

Searching together

Within the group of Alexey Boyarsky, Bondarenko has made predictions about the production and detection of sterile neutrinos and calculated their properties. These are currently used by the high-intensity SHiP experiment—a collaboration of 52 scientific institutes that searches for hidden particles. The ShiP researchers need those predictions to know what they are looking for. Their data consists of decay products of created particles. Only if they know the possible decay products of sterile neutrinos, they can (indirectly) see them. Bondarenko: ‘In our field of research, the discovery of any new particles is a great event. If a sterile neutrino will be discovered, it will significantly change the whole research area.’

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