This seminar highlights the significant progress made in the identification of exotic multiquark resonances, a breakthrough made possible by a decade's worth of extensive, precise data from experiments like the LHCb, enhanced by advancements in computational methods. A key factor in these discoveries has been the high production of charm and bottom states, boosted by an efficient trigger system, combined with superior tracking and particle identification technologies. These tools are vital in detecting and analyzing narrow states. Central to our understanding of these exotic particles is the use of multidimensional angular analysis. This technique is instrumental in distinguishing different quantum numbers, thereby offering insights organization of the exotic multiples. These states, which manifest as resonances in meson-meson or meson-baryon systems, have prompted a reevaluation and expansion of traditional quark models to include tetraquarks and pentaquarks. An interesting aspect of these discoveries is the realization that each new class of hadrons is accompanied by a spectrum of its radial and orbital excitations, suggesting a multitude of potential states. However, the manifestation of these states is intricately influenced by the continuum - the hadronic system into which they decay. This aspect is particularly evident in several states that resemble hadron-hadron molecules. Such observations are progressively blurring the distinctions between conventional Quantum Chromodynamics (QCD) states and nuclear physics, underscoring a pressing need to decipher the internal structure of these exotic hadrons and how their formation correlates with the fundamental laws of QCD. This seminar aims to provide an exploration of these fascinating developments from both experimental and theoretical standpoints, illuminating the dynamic and evolving landscape of particle physics.
Alessandro Pilloni is an Assistant Professor at the University of Messina since 2021. He got his Ph.D. in Rome in 2016, and then he has been a post-doc in the theory division of Jefferson Lab, at ETC Trento and and at INFN Rome.
Mikhail Mikhasenko is an Associate Professor at Ruhr University Bochum since 2023. He got his Ph.D. at Bonn University in 2019 in the group of Bernhard Ketzer, and then he moved to CERN as a research fellow and then to Munich at the ORIGINS Excellence Cluster.