Monday, April 14, 2014

Jet Production in pp, p-Pb and Pb-Pb collisions measured by the ALICE experiment

Rosi Reed (Wayne State)

In relativistic heavy-ion collisions a hot, dense medium of strongly interacting matter called the Quark Gluon Plasma (QGP) is formed. One of the main goals of jet measurements is to understand how hard scattered partons lose energy as they traverse through a colored medium. A study of jet spectra and correlations in a variety of collisional systems will allow a better understanding of the detailed mechanisms of this in-medium energy loss and will further constrain theory models of this process. The measurement of the jet production cross-section in three different colliding systems: pp, p-Pb, and Pb-Pb, allows for the determination of jets in QCD vacuum, in cold nuclear matter and in a QGP. The two reference measurements will allow a better extraction of the modification of the parton shower due to the hot partonic matter. Cold nuclear matter effects, such as shadowing, could modify the cross-section or fragmentation relative to pp, which would need to be removed from any potential measurement of the modification in hot nuclear matter. In order to fully understand the modification of the parton fragmentation function, it is important that the underlying event background and its fluctuations is well understood for all colliding systems. This fluctuating background can smear the jet spectrum, and can be corrected for along with detector effects during an unfolding process. I will present recent ALICE results on jet production and single hadrons, which are a good proxy for jets, in pp, p-Pb and Pb-Pb collisions and discuss their sensitivity to a modified jet fragmentation function.