Monday 03 March 2025
The internal structure of hadrons, the building blocks of matter, has long been a topic of fascination for physicists. Hadrons are made up of quarks and gluons, which are bound together by strong nuclear forces. However, despite significant advances in understanding these forces, the exact nature of the quark-gluon interactions within hadrons remains a mystery.
A recent study published in a scientific journal has shed new light on this complex topic. Researchers used an algebraic model to explore the internal structure of the first radial excitation of the pion, a pseudoscalar meson made up of a quark and an antiquark. The team found that the excited state exhibits distinct features, such as nodes in the leading Chebyshev moment of the amplitude, which significantly alter its distribution amplitude.
The pion is the lightest pseudoscalar meson, and its internal structure has been extensively studied. However, radial excitations of the pion have received relatively little attention. These excited states are formed when a quark-antiquark pair is created in the vacuum and then bound together by strong nuclear forces.
The researchers used a simplified model based on the continuum Schwinger methods and Nakanishi representation to study the first radial excitation of the pion. They found that the distribution amplitude of this excited state is broader than that of the ground state, with a more complex structure in momentum space. The transition form factor, which describes how the pion interacts with photons, was also studied.
One of the most interesting findings of the study is the charge density of the excited state. The researchers found that it is much broader than that of the ground state, indicating that the binding between quarks and gluons in the excited state is weaker. This is consistent with physical intuition, as one would expect the binding to be stronger for the stable ground state.
The study also explored the distribution function of the excited state, which describes how the momentum of the quark-antiquark pair is distributed within the pion. The researchers found that it is narrower than that of the ground state, with a peak around x=1/2 and distinct concave and convex fluctuations in the valence region.
The findings of this study provide new insights into the structure of excited hadrons and contribute significantly to our understanding of hadronic excitations. The results also highlight the importance of studying higher radial excitations, including their impact on processes such as light-by-light scattering.
Cite this article: “Unraveling the Internal Structure of Hadronic Excitations”, The Science Archive, 2025.
Quarks, Gluons, Hadrons, Pion, Radial Excitations, Distribution Amplitude, Transition Form Factor, Charge Density, Nakanishi Representation, Continuum Schwinger Methods
Reference: Xiaobin Wang, Lei Chang, “Unveiling the inner structure of the pion first excited state” (2025).
