Studying hadrons with hidden strangeness

• Grant number: 25/19497-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2025
• End date: July 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - Nuclear Physics
• Principal Investigator: Alberto Martinez Torres
• Grantee: Rafaela Costa Teles
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The LHCb Collaboration was responsible for one of the significant discoveries of the last decade: the undeniable existence of pentaquark states, the so-called Pc states. Initially, two states were observed, Pc(4450) and Pc(4380), but subsequent analyses, using more statistics and improved measurement techniques, revealed that the broad structure related to Pc(4450) corresponded to two narrow states, Pc(4440) and Pc(4457), and another narrow structure was found at 4312 MeV, Pc(4312). These states, discovered in the invariant mass distribution of J/¿ p obtained from ¿_b decays, represent nucleon resonances with hidden charm, i.e., c anti-c content and isospin 1/2, and they require a minimum content of five quarks to explain these quantum numbers. Pc states are, then, what are generally known as exotic hadrons, that is, those that do not fit the traditional quark model, and in which baryons are described as three-quark bound states. Since the Pc states are nucleon resonances with mass in the charmonium region, it is worth asking whether there are lighter partners of the Pc states with hidden strangeness. If so, how could such states be identified experimentally? In this project, the student will study the properties of Nstar resonances with hidden strangeness, which may be partners of Pc states. (AU)