Newswise – The Science

Difficult cores such as lead-208 are usually characterized by an outer shell Neutrons, called neutron skin. If those cores Are collided Quarks and gluons form at speeds close to the speed of light Protons and the neutrons fuse into a state of matter called a quark-gluon plasma. The shape and size of the Quark-gluon plasma These collisions are influenced by the thickness of the neutron skin. This makes it possible to infer this thickness from experimental observations.

The impact

In an atom core, the size of the neutron skin is sensitive to the strong interaction between protons and neutrons. The same interaction determines the behavior of the matter of which it is composed Neutron stars. They are among the most mysterious objects observed in the sky. They have a mass about one to two times that of the Sun, but a radius of only about 6 miles. Therefore, the neutron skin determinations on Earth allow us to deepen our knowledge of these extreme celestial objects.


The thickness of the neutron skin of a heavy nucleus influences the shape and size of the quark-gluon plasma that results from high-energy collisions between two nuclei cores. This, in turn, affects the distribution of particles emitted in these collisions, which are measured by particle detectors at the Large Hadron Collider. Researchers have developed sophisticated theoretical models to describe these collisions, including advanced tools that allow scientists to adjust model parameters to describe large sets of experimental data points.

In this analysis, researchers used the Trajectum hydrodynamic model tuned to 670 experimental data points measured at the Large Hadron Collider. One of the parameters of this model is the size of the neutron skin. By comparing the model parameters with the experimental results, the researchers found the neutron skin value of lead-208 that best describes the data. This provides the first neutron skin determination for lead cores using collider data.


One of the researchers was funded by the German Research Foundation (DFG) as part of the German Excellence Strategy (Excellence Cluster Heidelberg STRUCTURES). Another researcher was supported by the Department of Energy Office of Science and the Office of Nuclear Physics.

Journal link: Physical Review Letters, November 2023

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