OpenUCT :: Browsing by Author "Horowitz, William A."

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pQCD energy loss and thermal field theory in small systems
(2019) Kolbe, Isobel; Horowitz, William A.
In recent years, experiments at the Large Hadron Collider and the Relativistic Heavy Ion Collider have discovered that many of the signatures that are traditionally ascribed to the presence of a quark-gluon plasma (QGP) in central heavy-ion collisions also manifest in certain classes of peripheral heavy-ion collisions as well as in smaller colliding systems. The glaring exception to this list of observations of QGP signatures in small systems is the partonic energy loss. However, current theoretical descriptions of partonic energy loss are ill-adapted to small systems. This thesis first presents a numerical analysis of an analytical small system extension of a standard energy loss formula, and finds that major inconsistencies in the description of small system energy loss persist, motivating a need for a first principles calculation of the properties of a small droplet of QGP. Thereafter, a first step toward such a calculation is presented by considering a single, massless, scalar field that has been geometrically confined by means of Dirichlet boundary conditions. This toy model reveals, via thermal field theoretic techniques, that quantum fields are very sensitive to the presence of a boundary, presenting significant deviations from the Stefan-Boltzmann limit and revealing a geometrically driven phase transition at the scale of the medium.