Scientists studied the residual interaction between hadrons

ALICE takes the next step in understanding the interaction among hadrons.


A recent study reports the interaction between two-quark and three-quark particles. Their measurements, for the first time, unveiled an interaction between the ɸ (phi) meson (strange-antistrange quarks) and a proton (two up and one down quarks).

The interaction between ɸ (phi) and proton can only be attributed to the strong residual interaction. The residual strong interaction is the force that acts between hadrons. Such strong interaction holds together quarks inside hadrons.

Unlike the residual strong interaction, the interaction between unstable hadrons produced in particle collisions is challenging to study. However, the method called femtoscopy allowed ALICE collaboration to explore such interaction in the LHC.

In LHC, Hadrons are produced very close to each other, at distances of about 10-15 m. This scale matches the range of the residual strong force, giving them a brief chance to interact before flying away. This causes hadron pairs to experience an attractive interaction and move slightly closer to each other. The opposite happens during a repulsive interaction.

Both effects are observable when using a detailed analysis of the measured relative velocities of the particles.

The interaction between proton-meson is the crucial point for searching for the partial restoration of chiral symmetry. The left- and right-handed (chiral) symmetry determines the strong interaction. When this symmetry is broken, the effect results in a much larger mass of hadrons, like the proton and neutron, concerning the masses of the quarks that constitute them.

Studying the modifications of the properties of ɸ mesons within dense nuclear matter formed in collisions at the LHC is the possible way to search for restoration of chiral symmetry. This would also shed light on the mechanism that generates mass.

Understanding the simple two-body p-ɸ interaction in a vacuum is vital for this purpose.

Another fact- meson is considered a key to the interaction among baryons, which contains hyperons. This is due to the strange-antistrange quark content of mesons.

The hyperons may form the core of neutron stars, based on how powerful the interaction between them is. However, the direct measurement of the Y-ɸ interaction strength has not yet been carried out. Still, already today, this quantity can be related to the p-ɸ findings via fundamental symmetries. Therefore, measuring p-ɸ interaction provides indirect access to the Y-Y interaction in neutron stars.

The measurements of the moderate interaction strength by ALICE acts as a reference for further studies of the ɸ properties within the nuclear medium.

Scientists noted“More accurate measurements will follow during the upcoming LHC Run 3 and Run 4, allowing to significantly improve the precision of the extracted parameters and also to pin down the Y-ɸ interaction directly.”

Journal Reference:

  1. S. Acharya et al. Experimental Evidence for an Attractive p-ϕ Interaction. DOI: 10.1103/PhysRevLett.127.172301
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