Colloquium: Dr. Thomas Humanic (Ohio State University)

Abstract: Tetraquark particles, i.e. particles composed of four quarks, with masses less than 1 GeV/c2 have been predicted for over 40 years. Candidate particles with the predicted masses and charge states have been identified, but to this date it is still controversial as to whether or not these candidate particles, listed in the Review of Particle Physics as two-quark mesons, can be interpreted as tetraquark states. Low-lying mesons that are considered as candidate tetraquarks are the f0(500), K∗0(700), f0(980) and a0(980). These particles are normally studied experimentally in low-energy pp collisions which produce higher-mass particles for which these are the decay products. The method used to produce and study these exotic particles for the present work is two-particle femtoscopy in pp and Pb-Pb collisions at the LHC with the ALICE experiment. Femtoscopy with identical particle-pairs is a method that is usually used to measure the geometry in high-energy particle interactions. By detecting non-identical pairs of ordinary mesons, femtoscopy picks out the strong final-state interaction (FSI) between the mesons in the pair.