Public Abstract

DE-SC0002145: QCD Description of Hadronic Interactions at High Energies

Award Status: Active

Institution: The Pennsylvania State University, University Park, PA
UEI: NPM2J7MSCF61
DUNS: 003403953

Most Recent Award Date: 09/23/2025
Number of Support Periods: 16
PM: Morreale, Astrid

Current Budget Period: 08/01/2025 - 05/31/2026
Current Project Period: 08/01/2025 - 05/31/2028
PI: Stasto, Anna

Supplement Budget Period: N/A

Public Abstract

QCD Description of Hadronic Interactions at High Energies Anna Stasto, Pennsylvania State University (principal investigator) Quantum Chromodynamics (QCD) is the non-abelian quantum field theory of strong interactions. It is part of the Standard Model of particle physics, which has been very successful in describing the experimental data in a wide range of scales. Nevertheless, despite this success, there are still many fundamental questions that are left unanswered and need to be explored. One of them is the accurate description and thorough understanding of the dynamics of strong interactions at very high energies and partonic densities. This is the regime which is probed in the high energy particle colliders like Large Hadron Collider and in cosmic ray interactions, as well as in neutrino observatories. Highly energetic collisions with protons and nuclei explore the kinematic region which is characterized by many interesting phenomena, such as very high gluon density and diffraction. Description of these phenomena at high energies or low Bjorken x requires appropriate computational techniques. In this proposal we aim to explore high energy limit of QCD through the formal and phenomenological analysis of variety of hadronic processes which can be probed in current and future high-energy accelerators. This includes processes that are currently studied at proton-proton and nuclei collisions at LHC and in future Electron Ion Collider. The first topic which will be studied as part of this project is the heavy quark production in ultraperipheral collisions (UPC) at the LHC. In these events the interaction between nuclei is dominated by the electromagnetic part. The heavy quark production in UPCs is an excellent probe of the nuclear structure at low values of Bjorken x. Charmed meson production at fixed order in collinear framework as well as using resummed approach will be calculated including nuclear effects. The results of the calculations will be compared with the LHC data from UPC on this process. The diffractive component for the charm production in UPCs will also be computed. Low x dynamics can be also tested in diffractive processes occurring in electron-proton/nucleus and hadronic collisions. These are events with large rapidity gaps and are usually interpreted as an exchange of the colorless object. Analysis of the inclusive diffractive structure function at the Electron Ion Collider will be performed, with a focus on the potential parton saturation effects. In particular the impact of the effects of higher twists onto inclusive diffractive structure functions will be investigated and possibility of distinguishing the signals of saturation. Investigation of the diffraction on a deuteron targets is also planned. Furthermore, we plan to explore the dissociative diffraction of heavy vector mesons at large momentum transfers, using the Balitsky-Fadin-Kuraev-Lipatov (BFKL) non-forward evolution including small x resummation, in the ultraperipheral collisions. The final goal in this project will be focused on the extension and phenomenological applications of the resummation framework at small x, the Ciafaloni-Colferai-Salam-Stasto (CCSS) approach. Resummation at small x is necessary for the precise predictions for phenomenology at high energies. Numerical solutions of the resummed evolution with CCSS resummation and saturation will be provided for the unintegrated gluon density. Further steps will include the incorporation of higher order collinear contributions. Finally, the recently constructed resummed impact factors will be incorporated in the calculations for the structure functions and calculations will be applied to phenomenology. Interplay between the parton saturation and resummation effects will be investigated.

QCD Description of Hadronic Interactions at High Energies
Anna Stasto, Pennsylvania State University (principal investigator)

Quantum Chromodynamics (QCD) is the non-abelian quantum field theory of strong interactions. It is part of the Standard Model of particle physics, which has been very successful in describing the experimental data in a wide range of scales. Nevertheless, despite this success, there are still many fundamental questions that are left unanswered and need to be explored. One of them is the accurate description and thorough understanding of the dynamics of strong interactions at very high energies and partonic densities. This is the regime which is probed in the high energy particle colliders like Large Hadron Collider and in cosmic ray interactions, as well as in neutrino observatories.

Highly energetic collisions with protons and nuclei explore the kinematic region which is characterized by many interesting phenomena, such as very high gluon density and diffraction. Description of these phenomena at high energies or low Bjorken x requires appropriate computational techniques.

In this proposal we aim to explore high energy limit of QCD through the formal and phenomenological analysis of variety of hadronic processes which can be probed in current and future high-energy accelerators. This includes processes that are currently studied at proton-proton and nuclei collisions at LHC and in future Electron Ion Collider.

The first topic which will be studied as part of this project is the heavy quark production in ultraperipheral collisions (UPC) at the LHC. In these events the interaction between nuclei is dominated by the electromagnetic part. The heavy quark production in UPCs is an excellent probe of the nuclear structure at low values of Bjorken x. Charmed meson production at fixed order in collinear framework as well as using resummed approach will be calculated including nuclear effects. The results of the calculations will be compared with the LHC data from UPC on this process. The diffractive component for the charm production in UPCs will also be computed.

Low x dynamics can be also tested in diffractive processes occurring in electron-proton/nucleus and hadronic collisions. These are events with large rapidity gaps and are usually interpreted as an exchange of the colorless object. Analysis of the inclusive diffractive structure function at the Electron Ion Collider will be performed, with a focus on the potential parton saturation effects. In particular the impact of the effects of higher twists onto inclusive diffractive structure functions will be investigated and possibility of distinguishing the signals of saturation. Investigation of the diffraction on a deuteron targets is also planned. Furthermore, we plan to explore the dissociative diffraction of heavy vector mesons at large momentum transfers, using the Balitsky-Fadin-Kuraev-Lipatov (BFKL) non-forward evolution including small x resummation, in the ultraperipheral collisions.

The final goal in this project will be focused on the extension and phenomenological applications of the resummation framework at small x, the Ciafaloni-Colferai-Salam-Stasto (CCSS) approach. Resummation at small x is necessary for the precise predictions for phenomenology at high energies. Numerical solutions of the resummed evolution with CCSS resummation and saturation will be provided for the unintegrated gluon density. Further steps will include the incorporation of higher order collinear contributions.

Finally, the recently constructed resummed impact factors will be incorporated in the calculations for the structure functions and calculations will be applied to phenomenology. Interplay between the parton saturation and resummation effects will be investigated.