Big satisfaction among the scientists of the Section that participate in the ALICE experiment for the publication, on December 9, on Nature of the article “Unveiling the strong interaction among hadrons at the LHC”, where the first measurement of the interaction between protons and Xi (Ξ) and Omega (Ω) particles is presented (Nature volume 588, pages 232–238 (2020)).
One of the key challenges for nuclear physics today is to understand from first principles how the interaction works between protons and neutrons, which form the nucleus, and the so-called hadrons, which include, beside protons and neutrons, many other particles, such as, for example, the Ξ and Ω hyperons, produced in the accelerators and in nature in cosmic rays. Hyperons are slightly heavier than the protons and carry an additional quantum number, called strangeness.
It has been known for a long time that the quarks are the constituents of hadrons and that the interaction among quarks is coded in Quantum-Chromo Dynamics (QCD). However, deriving the interaction among hadrons from QCD remains at present a strenuous task, which is possible only by means of lattice calculations, very demanding from the computational point of view. The experimental study of the interaction between hadrons is limited by the fact that most of them, such as the Ξ and Ω hyperons, are unstable and, therefore, cannot be accelerated in beams and crashed in colliders.
A completely new method to study the interaction between hadrons has been implemented by the ALICE experiment by measuring the correlations amongparticles produced in the collisions at the Large Hadron Collider at CERN. The ALICE experiment (https://home.cern/science/experiments/alice), designed for the study of the quark-gluon plasma, a state of matter that is believed to have existed right after the Big Bang, becomes in this manner the first laboratory for the study of hadron interactions between protons and hyperons. The first measurement of this type, presented in the article on Nature, pioneers a new era in nuclear physics with precision tests of QCD in the non-perturbative regime.
Scientists of the ALICE-Trieste group have been working for many years on several topics related to hadron interactions. Interested readers can find further information on the group’s web page https://www.ts.infn.it/com/ricerca/gr3/alice.