Study Sheds New Light on Particle Creation
Physicists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory (BNL) and Stony Brook University have shown that particles produced in collimated sprays called jets retain information about their origins in subatomic particle smashups. The study was recently published as an Editor’s Suggestion 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 in Stony Brook’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 comes from an analysis of jet particles emerging from proton-proton collisions captured by the ATLAS experiment at the Large Hadron Collider, a 17-mile-circumference circular collider located at CERN, the European Organization for Nuclear Research. In these powerful collisions, the individual building blocks of the colliding protons, known as quarks and gluons, scatter off one another and sometimes get knocked free with enormous amounts of energy. But quarks can’t stay free for long. They and the gluons that normally hold them together immediately begin to split and reconnect through a branching process called fragmentation. The result is the formation of many new composite particles made of pairs or triplicates of quarks — collectively known as hadrons — that spray out of the collision in a coordinated way, that is, as a jet.
“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,” said Abhay Deshpande, a distinguished professor at Stony Brook. Deshpande holds a joint appointment as director of science for the Electron-Ion Collider, a new nuclear physics research facility under construction at Brookhaven Lab, and he is also currently serving as BNL’s interim associate laboratory director for nuclear and particle physics.
The analysis was motivated in part by earlier research by study co-authors Zhoudunming Tu and Dmitri Kharzeev, both with faculty roles at Stony Brook and appointments at BNL. Their study, published last year, revealed a connection between entanglement among quarks and gluons within protons and the overall distribution of particles emerging from proton-proton and electron-proton smashups. In that work, the higher the entanglement entropy among the quarks and gluons, the greater the entropy, or “messiness,” in the distribution of particles produced.
“This earlier study revealed that there is maximal entanglement among the quarks and gluons within the high-energy proton,” said 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?”
Read the full story at the BNL website.