Researchers Obtain New Analytical Solution to Quantum Chromodynamics Evolution Equation (Quantum)

A research group led by Prof. CHEN Xurong at the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS) has for the first time, successfully applied the “homogeneous balance method” to the quantum chromodynamics (QCD) evolution equation and obtained a new analytical solution of the Balitsky-Kovchegov (BK) evolution equation. The results were published on March 12 in Physical Review D.  

The distribution of partons (quarks and gluons) in protons and nuclei is essential for understanding many high-energy physical processes, as all studies on high-energy physical processes involving protons and nuclei require the function information of partons distributions.  

Since the distribution of gluons cannot be measured directly by electrons probe without charge, the partons evolution equations, which are basic in QCD theory, are the powerful tools to extract quarks and gluon distribution functions from experimental data. The electron ion colliders (EIC), which are being proposed in China and abroad, will offer precise measurements of partons distribution functions in nuclei to test various QCD evolution equations.

Figure 2. Geometric scaling law, experimental data (red), and the curve (black) given by the study. (Image by IMP) 

“The BK equation is a complex QCD evolutionary equation, and its analytical solution is essential for the study of gluon condensed physics,” said Prof. CHEN Xurong. 

Then researchers obtained the saturated energy scale of the gluon, and finally gave the geometric scale law, which revealed the law of the color glass condensed (CGC) matter in the high energy region. 

This progress not only promotes our understanding of QCD theory and the CGC states, but also provides theoretical support for the electron ion collider projects.  

This work was supported by the pilot project of CAS. 

Featured image: QCD Evolution Equations. (Image by A. Accardi et al.)

Reference: Xiaopeng Wang, Yirui Yang, Wei Kou, Rong Wang, and Xurong Chen, “Analytical solution of Balitsky-Kovchegov equation with homogeneous balance method”, Phys. Rev. D 103, 056008 – Published 12 March 2021.

Provided by Chinese Academy of Sciences

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