Hadronic QCD Physics

We are:

Dr. G.M. Huber Professor of Physics

B.Sc.Phys., B.Sc.Math., Ph.D. (Regina)

Proton and Pion Form Factors
Dr. G.J. Lolos Professor Emeritus of Physics

Lyceum, Dipl.Phys. (Athens), Ph.D. (Regina)

GlueX - Exotic Hybrid Mesons
Dr. Z. Papandreou Professor of Physics

Lyceum (Thessaloniki), B.Sc.Phys., Ph.D. (Regina)

GlueX - Exotic Hybrid Mesons
Dr. A. Semenov Research Scientist, Adjunct Professor

M.Sc. (Moscow State University), Ph.D. (JINR, Dubna)

GlueX, GEn

along with postdoctoral researchers and graduate students.

Our research explained for the public:

The aim of our research group is to study and understand certain aspects of the inner workings of the fundamental building blocks of matter (quarks). Quarks are not manifested as free particles in nature, therefore their study involves investigations of their stable combinations in particles, such as nucleons (protons and neutrons) as well as the particles which ``transmit'' the nuclear force among them, the mesons. Ultimately, the glue itself, which binds quarks, is also an objective of our investigations. In order to accomplish this goal, our group leads experimental efforts in the field of subatomic physics.

Nucleons and mesons, then, are composed of smaller, more fundamental particles, the quarks and gluons. As a result of the motion of the quarks (which produces magnetism) and their electrical charge, nucleons and mesons exhibit a distinct structure. We plan to map out this structure accurately, in order to test theoretical predictions and to provide valuable input to the interpretation of other experiments in the field. We have chosen the high energy electron beam at the Jefferson Lab, USA, for this mapping, because electrons do not have a composite structure of their own and are thus the cleanest probe to access the desired physics.

The nature of the interaction among quarks, on the other hand, is best investigated with photons (quanta of pure energy) through the production of exotic mesons which are not found in ordinary matter. These exotic mesons, called exotic hybrid mesons, carry unique signatures of the combinations of quarks and gluons. The investigation of exotic particles will be pursued at the proposed, new Hall D/GlueX facility at Jefferson Lab, which will take advantage of the future energy upgrade at this laboratory.

Our main endeavours are presented below.

  • The GlueX Experiment

    For the past quarter-century, physicists have suspected that subatomic particles made of the very glue that holds matter together at the most fundamental level must exist. Recently, searches for these elusive particles have intensified as tantalizing hints of their presence have appeared. These include evidence for exotics (mesons with exotic quantum number combinations). The GlueX project at Jefferson Lab aims to identify these unusual particles predicted by QCD, but whose structure lies outside the quark model.

  • Studies of Hadronic Structure with Electromagnetic Probes

    It is widely accepted that nucleons and nuclei are built from quarks, and the theory which describes their behavior is QCD, but this understanding is far from perfect and still untested in many ways. Our research program at Jefferson Lab (USA) is based on the search of direct QCD signatures in mesons and nucleons below the region of perturbative QCD (pQCD). For example, pQCD predicts a unique behavior of the pion form factor, as a direct consequence of the asymptotic freedom of quarks at infinite momenta. Our experiments will be the first to test this prediction.

For the experts: