A Different Angle on the Color Glass Condensate

Physics 16, s89
Predictions indicate that a new type of measurement at the future electron–ion collider could spot an elusive high-density regime of gluons called the color glass condensate.  
Brookhaven National Laboratory

The gluon is the “glue” of subatomic particles, mediating the strong force that binds quarks to make subatomic particles such as protons and neutrons. Researchers can image the gluons within a proton by colliding protons with high-energy electrons. Most often, the resulting image reveals sparsely distributed gluons. But under specific conditions, such collisions are predicted to provide a glimpse of a very high-density state of gluons called the color glass condensate. Now Xiaohui Liu of Beijing Normal University and colleagues propose a way to observe the color glass condensate using the future electron–ion collider (EIC), which is set to be built at Brookhaven National Laboratory, New York [1].

The EIC will collide electrons with heavy ions, such as gold. Liu and colleagues propose looking for signatures of the color glass condensate in the debris of these collisions. Their method involves measuring the energy of the debris as a function of its angle relative to the collision axis. Models indicate that a measure of correlation between the debris energy and angle depends on whether the gluons in the ion that participated in the collision were in a dilute state or the color glass state. So, by measuring this correlation, Liu and colleagues predict that researchers can pinpoint the “saturation scale,” which marks the onset of the color glass condensate regime within an ion. Such a measurement could shed light on the unique ability of gluons to interact among themselves.

–Nikhil Karthik

Nikhil Karthik is an Associate Editor for Physical Review Letters.


  1. H.-Y. Liu et al., “Nucleon energy correlators for the color glass condensate,” Phys. Rev. Lett. 130, 181901 (2023).

Subject Areas

Particles and FieldsNuclear Physics

Related Articles

Colossal Magnetic Field Detected in Nuclear Matter
Nuclear Physics

Colossal Magnetic Field Detected in Nuclear Matter

Collisions of heavy ions briefly produced a magnetic field 1018 times stronger than Earth’s, and it left observable effects. Read More »

Three’s Company for Bottom Quarks
Nuclear Physics

Three’s Company for Bottom Quarks

Bottom quarks are increasingly more likely to exist in three-quark states rather than two-quark ones as the density of their environment increases. Read More »

Five New Isotopes Is Just the Beginning
Particles and Fields

Five New Isotopes Is Just the Beginning

Less than a year after its opening, the Facility for Rare Isotope Beams produced five never-before-seen isotopes for observation, a success that researchers say highlights the discovery potential of the facility. Read More »

More Articles