PHYSICS
ALICE uses ML to determine charm & beauty dynamics in quark-gluon plasma
New data from ALICE sheds light on the behavior of charm and beauty particles in quark-gluon plasma. When lead ions collide at high energies in the LHC, they create a super-hot and dense state called quark-gluon plasma where quarks and gluons are no longer bound inside hadrons. This extreme environment is believed to have existed for a brief moment just after the Big Bang before quickly expanding and cooling down. As it cools, the quarks and gluons form back into hadrons which can be detected by particle detectors.
The study conducted by ALICE involved lead-lead collisions at non-direct angles. They compared the elliptic flow of "prompt" D mesons (produced immediately after the collision) to that of "non-prompt" D mesons (produced during the decay of B mesons). Charm quarks combine with light quarks to form D mesons while beauty quarks form B mesons. Previous studies have shown that the elliptic flow of "prompt" D mesons is nearly as strong as that of the lightest hadrons, and pions. However, it is expected that the elliptic flow of B mesons will be weaker than that of prompt D mesons due to the predicted longer thermalization time for beauty quarks compared to charm quarks.
In the recent analysis of off-center lead-lead collisions during Run 2 of the LHC, ALICE measured the elliptic flow of B mesons by examining the flow of "non-prompt" D mesons that originate from B meson decays. This was possible through the use of machine-learning techniques, which helped distinguish between products of non-prompt and prompt D meson decays and suppress background particle processes that imitate D meson production and decay.
The latest measurement reveals a significant difference in the elliptic flow of non-prompt D mesons compared to their prompt counterparts, confirming previous expectations. This discovery provides valuable insights into the thermalization process of beauty quarks within the quark-gluon plasma and sets the stage for future ALICE investigations using data from Run 3 of the LHC. The increased sample of lead-lead collisions obtained in 2023 will pave the way for a deeper analysis of charm and beauty particles, unraveling further mysteries surrounding their behavior within the quark-gluon plasma.
