RUI: Disentangling Quark and Gluon Energy Loss with Heavy Flavor Jets in the ALICE Experiment at the CERN LHC

California Polytechnic State University Foundation, San Luis Obispo CA

Investigators

Abstract

The Universe as we know it evolved from a very hot, dense primordial soup of fundamental particles that were created in the cataclysm known as the Big Bang. As the Universe expanded and cooled, these fundamental particles, called quarks and gluons, condensed into protons and neutrons, which eventually combined into nuclei that captured electrons to form atoms. Nearly everything we can observe is made from this fundamental material. Using large particle accelerators, scientists are recreating the conditions at the birth of the Universe in the laboratory by colliding gold or lead atoms at very high energies to study the properties and interactions among these particles. These investigations will provide us with clues to the deeper nature of the fundamental forces in the Universe. One of the most important discoveries to come from such experiments is that the dense matter created in these collisions is opaque to very high energy quarks and gluons produced in them. These "partons" suffer tremendous energy loss as they make their way out of the collision zone, depositing a large fraction of their initial energy in the medium. The strength of the energy loss is directly related to the density of the medium and varies according to the type of parton. It appears that the heavier the parton, the more energy loss it suffers. Energetic partons fragment into a spray of particles called a "jet". If a jet contains a high energy electron, there is a very high probability that it originated from a heavy quark. The energy loss of these electron-jets can be used to investigate the properties of the quark gluon plasma medium through which it passed. The goal of this research is to disentangle the energy loss of quarks and gluons by isolating jets containing electrons and comparing their energy loss patterns to those without electrons. The CERN Large Hadron Collider (LHC) in Switzerland collides nuclei at the highest energies ever created in a laboratory. This RUI project will utilize the ALICE experiment to explore the properties of the quark-gluon plasma using the energy loss of heavy quark jets as a probe. Undergraduate students working on this experiment will be trained in the most advanced data collection, reduction and analysis techniques at the cutting edge of high energy nuclear physics. They will be able to apply these skills in a wide variety of careers, whether they choose to pursue an advanced degree in basic science or not. Their contributions will also help us develop new understanding of the fundamental interactions among the basic building blocks of matter, leading to a deeper understanding of the Universe we inhabit.