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PhD candidate makes predictions on production and detection of sterile neutrinos

Physicists propose the existence of sterile neutrinos that would explain three big mysteries in nature. To actually find them in particle accelerators, researchers need to know how they are produced and how they decay. PhD candidate Kyrylo Bondarenko has made predictions about this, which are currently used by a large collaboration of 52 scientific institutes. He thesis received the predicate cum laude.

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, which quickly annihilated with its counterpart into nothing. This could have been the shortest and only story in the Universe. However, a slight asymmetry in the ratio between matter and antimatter caused a ten-billionth part to survive. That formed the Universe as we know it, including a species trying to explain this enigmatic asymmetry. It is one of the big fundamental questions in particle physics, together with the nature of dark matter and the mystery behind neutrino particles oscillating between three different kinds.

νMSM model

On top of the well-proven Standard Model, particles physicists have developed an additional model that solves the three problems mentioned above all at once: the Neutrino Minimal Standard Model (νMSM). It predicts three undiscovered particles, called sterile neutrinos: a dark matter candidate with a mass of between 1 and 50 keV/c2 and two particles that are together responsible for neutrino oscillations and matter-antimatter asymmetry, with a mass range of a few MeV/c2 to tens of GeV/c2. If scientists were to find them, it would provide strong evidence for the νMSM model, and therefore the solution to three major scientific puzzles. So where do you look? During his PhD studies, physicist Kyrylo Bondarenko has reviewed and revised ways to find the particles by extending the intensity frontier.

Energy frontier

In the previous decades, physicists were pushing the energy frontier, meaning that they build 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. The relatively massive Higgs boson was produced in the Large Hadron Collider at CERN by increasing the energy frontier up to 8 TeV.

Intensity frontier

The sterile neutrinos from the νMSM model have been within our energy reach for decades. The reason why we have never seen them, might be that they are interacting feebly with other particles. Then you would need a ridiculous number of consecutive collisions, in the order of 1020, before one finally emerges by sheer coincidence. This means that physicists should extend the intensity frontier by generating more collisions per second. Within the group of Alexey Boyarsky, Bondarenko has made predictions on the production and detection of sterile neutrinos. These are currently used by the 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.

Kyrylo Bondarenko defends his PhD thesis on November 15th at 11:15 in the Academy building.

Promotor Alexey Boyarsky: 'Kyrylo significantly developed phenomenology of new particles that may be responsible for the observed “beyond Standard Model problems”, contributed very significantly in the development of Monte Carlo simulations of the SHiP collaboration, a new experiment in CERN that will be looking for such particles, and predicted sensitivities of SHiP for a number of “portals” for new physics. His work was very significant and visible in the collaboration of 39 institutes from many countries, it also required a unique combination of theoretical and experimental expertise.'

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