QCD Description of Hadronic Interactions at High Energies

Anna Stasto, Pennsylvania State University (principal investigator)

Standard Model of particle physics is a fundamental theory which has been very successful in describing interactions of elementary particles. Its predictions  have been very well tested in experiments in a wide range of scales. Despite this overwhelming success there are still many questions that are left unanswered.  One of them is the dynamics  of strong interactions at high energies, which is still not completely understood. This is of great importance since this  is tested at high-energy collider experiments and in cosmic ray interactions.

The aim of this proposal is to address the fundamental questions in the strong interactions in the limit of high energies or low Bjorken x through the formal and phenomenological analysis of  variety of hadronic processes which can be probed in current and future high-energy  accelerators. 

Quantum Chromodynamics (QCD) is the non-abelian quantum field theory of strong interactions.  Due to the property of asymptotic freedom perturbative techniques have been very successful in description of the experimental data at short distance scales.  In the high-energy limit standard techniques can be however insufficient, as  it is expected that novel phenomena will appear in this regime. QCD predicts formation of a very dense partonic system in the highly energetic collisions as well as in collisions involving nuclear beams. This requires appropriate computational approach to describe accurately  novel phenomena at small Bjorken x.  

The first goal in this project is to extend the resummation framework at small x previously developed by the PI  and collaborators. In particular, PI intends to include  the resummation of the higher order terms in impact factors for Deep Inelastic Scattering (DIS) and  match to the resummed evolution in the gluon channel. Interplay between the resummed evolution  in this approach using the unintegrated gluon density  and the gluon  saturation effects will be investigated.

Low x dynamics can be also tested in diffractive processes.
 Analysis of the potential of the Electron Ion Collider (EIC) to measure the diffractive structure functions will be performed.  Studies of the momentum transfer dependence in diffractive structure functions will be done and the prospects in the context of EIC evaluated. Dissociative diffraction of vector mesons at large momentum transfers will be explored, using the Balitsky-Fadin-Kuraev-Lipatov non-forward evolution, also with resummation, in the context of current and future experimental data from electron-proton colliders.  Studies in the context of photoproduction, also in the ultraperipheral collisions of nuclei are planned.

Forward production in high energy collisions will be investigated within the small x framework. Predictions for the prompt neutrino fluxes originating from the  heavy meson decays will be made, using the unintegrated gluon density at small x including resummation as well as saturation. Finally, impact of different fragmentation scenarios  will be investigated.