Physicists from the U.S. Department of Energy's Brookhaven National Laboratory and Stony Brook University have discovered that particles formed in collimated sprays, known as jets, retain information about their origins from subatomic particle collisions. This study, highlighting a novel connection within particle physics, was recently published in the journal Physical Review Letters.
"Despite extensive research, the connection between a jet’s initial conditions and its final particle distribution has remained elusive," said Charles Joseph Naim, a research associate at the Center for Frontiers in Nuclear Science at Stony Brook University's Department of Physics and Astronomy. "This study, for the first time, establishes a direct connection between the ‘entanglement entropy’ at the earliest stage of jet formation and the particles that emerge as a jet evolves."
The evidence stems from an analysis of jet particles from proton-proton collisions observed in the ATLAS experiment at CERN's Large Hadron Collider. In these collisions, quarks and gluons interact with massive energy, scrambling and reconfiguring through a process called fragmentation. This results in the creation of new composite particles that eject as a jet.
Abhay Deshpande, a distinguished professor at Stony Brook, commented on their objective: "We wanted to see if the distribution of the hadrons in the jet was influenced by the level of entanglement among the quarks and gluons at the time the jet first formed." Deshpande holds multiple roles, including director of science for the Electron-Ion Collider at Brookhaven Lab.
Motivated by earlier research from study co-authors Zhoudunming Tu and Dmitri Kharzeev, both affiliated with Stony Brook University and Brookhaven Lab, the team explored the entanglement among quarks and gluons within protons. Their prior work demonstrated that higher entanglement entropy correlated with a more chaotic distribution of particles from proton-proton and electron-proton collisions.
"This earlier study revealed that there is maximal entanglement among the quarks and gluons within the high-energy proton," noted Tu. "In this work, we extend this approach to the production of jets, which form from the fragmentation of those quarks and gluons. Will there also be maximal entanglement 'inside' these fragmenting high-energy quarks and gluons?"
The complete study can be accessed on the Brookhaven National Laboratory website.