• effective field theory
• hypernuclei
• hyperon-nucleon interaction
• low-energy contact interactions
• neutron stars

In recent years, there has been a notable interest in investigating hyper-nuclear systems, which are systems where one or more nucleons, such as neutrons or protons, are replaced by hyperons. Hyperons are a type of baryon that contains at least one strange quark.
In neutron stars (NSs), especially under the extreme high-density conditions found in their interiors, the conversion of nucleons into hyperons becomes energetically favorable. Due to these high-density conditions, hyperons also become stable particles within NSs. Their presence lowers the energy density and thus the pressure within the star, a phenomenon known as the softening of the Equation of State (EoS). This softening in turn causes an underestimation of the maximum mass that can be reached in NS (a NS with a mass greater than the maximum mass collapses into a black hole), which contradicts experimental evidence. This discrepancy is known as the "hyperon puzzle." Solving this puzzle requires a detailed understanding of hyperon-nucleon (YN) interactions, hyperon-hyperon (YY) interactions, and three-body interactions involving hyperons and nucleons. Understanding the YN interaction is crucial not only for addressing the hyperon puzzle but also for enhancing our knowledge of strong interactions in the strange quark sector.
This project focuses on developing a local potential model for the 𝝠N interaction. "Local" here means that the interaction depends only on the relative distance between the particles, besides spin and isospin. The interaction developed in this work is expressed in coordinate space and was derived using the formalism of an Effective Field Theory (EFT), a low-energy realization of Quantum Chromodynamics (QCD). This EFT approach, which involves only contact terms, allows for a simplified operatorial structure and easier numerical implementation, making it suitable for studying complex systems like massive hypernuclei. Since we are using an EFT approach, our model is only valid up to a specific energy threshold, which is the so-called cutoff scale.
This potential model depends on some constants, known as Low Energy Constants, and commonly referred to as LECs, which encode the high-energy effects not resolved by the theory. The LECs had to be fixed through a fitting procedure to some experimental data. In the context of YN interaction, the only available data for this purpose are total cross sections of the 𝝠p elastic scattering. We had then to compute from the potential model, the cross section for 𝝠p elastic scattering, as a function of the LECs. The obtained results for this cross section were inserted in a chi square-function that was minimized to find the LECs values. We investigated eleven different values for the cutoff parameter, in the range [0.3, 3] fm. We found a reasonable agreement of our results with existing literature, from the comparison of the obtained chi square results, especially for cutoffs of the order of 1.5-2 fm. We also studied some predictions on the cross section in a wider energy range (up to kinetic energy in the center-of-mass frame E_CM=160 MeV) than the one used for the fit (E_CM=80 MeV) and we found out that our model can accurately predict reasonable results in that range too. In summary, we developed a local contact potential model for the 𝝠N interaction. The results show comparable degree of accuracy with existing literature and demonstrate the model ability to accurately reproduce cross sections, even beyond its primary range of applicability.