Algorithm Devised by HSE University and Yandex Helped to Catch New Particle at the Large Hadron Collider

The LHCb collaboration has announced that four new particles, excited omega baryons (Ω-b), have been observed in an experiment. The two higher mass signals peaks exceed significance of 5σ. This is the first experimental observation of such particles. These events were preselected by the algorithm developed by the joined effort of HSE University's Laboratory of Methods for Big Data Analysis and Yandex LLC.

The LHCb (Large Hadron Collider beauty) is one of the four major experiments situated carried out at the Large Hadron Collider. The experimentis optimised to analyse processes involving b and c quarks. In 2019, violation of CP-symmetry were observed and a previously unknown 'molecular' type of pentaquark was discovered by this experiment.

Recently, the collaboration published a preprint of its paper submitted to the Physical Review Letters journal. The paper provides evidence for the first-ever experimental observation of excited Ω−b states, or 'charmed omega' – a particle consisting of one b (beauty) quark and two s (strange) quarks. Excited state means that these particles have masses higher than the basic state for their configuration of constituent quarks. All four particles were registered with a topological trigger developed by scientists of the Laboratory of Methods for Big Data Analysis. The trigger essentially utilizes MatrixNet, the algorithm developed by Yandex and used for a variety of core company projects including Yandex web search engine.

'This trigger is based on employing oblivious decision trees,' notes Denis Derkach, Senior Researcher at the Laboratory of Methods for Big Data Analysis, 'Andrey Ustyuzhanin, Lab Principle Investigator together with Tatiana Likhomanenko, Alex Rogozhnikov in collaboration with LHCb colleagues devised a new solution on top of MatrixNet This solution allows selecting the data in significantly more effective way. It doesn't search for specific decays or specific physical processes, but groups of decays with common topological properties, which might be interesting for us. This approach allows the experiment to cast a wide search. If we only look for, say, pentaquarks, we could only find pentaquarks. In contrast, the proposed approach allows searching for many different new particles and phenomena.'

The LHCb data indicates that the observed new masses are consistent with the theoretical predictions for excited Ω−b resonances. All four new particles registered in the collider have masses about 6.3 GeV, about six times larger than that of a proton.

More information:
arxiv.org/abs/2001.00851

Provided by HSE University