Strong Interaction QCD Research Articles

Gluonic Origin and Glueball Nature of Pomeron**The project supported inpart by National NaturalScience Foundation of China under Grant No. 10247004 and the Natural ScienceFoundation of Guangxi Province of China under Grant Nos. 0339008 and 0481030

The Pomeron-nucleon coupling vertex is theoretically derived fromthe fundamental theory of strong interaction QCD. The empiricalvertex βγμF1(t) used commonly in diffractiveprocesses with a coupling strength β = 6.0 GeV-1 isinitially obtained from QCD theoretically. Our study not onlyreproduces the Pomeron-nucleon coupling from QCD but also clearlyshows the gluonic origin and glueball nature of Pomeron, whichis a longstanding puzzle. From this investigation, we claim that Pomeron can be regarded as a Reggeized tensor glueballξ(2230) with quantum numbers of IGJPC = 0+2++.Since the tensor glueball ξ(2230) lies on the Pomerontrajectory αp(t = Mξ2) = 2, the longstanding puzzlethat no physical particle lies on the Pomeron trajectory,αp(t) = 1.08 + 0.20 GeV-2 · t, seems to be solved.

JLab: probing hadronic physics with electrons and photons

Precision measurements of the structure of nucleons and nuclei in the regime of strong interaction QCD are now possible with the availability of high current polarized electron beams, polarized targets, and recoil polarimeters, in conjunction with modern spectrometers and detector instrumentation. The physics at JLab will be highlighted using two recent measurements of general interest. The ratio of the proton electric to magnetic form factors indicates the importance of the role of angular momentum in the structure of the nucleon. The existence of 5-quark configurations in the ground state wavefunctions of hadrons is confirmed by a narrow peak attributed to an exotic baryon with strangeness S=+1. These and other examples will be used to illustrate the capabilities and focus of the experimental program at JLab.

SPIN RESPONSE OF THE NUCLEON IN THE RESONANCE REGION

I discuss recent results from CLAS and Hall A at Jefferson Lab on the measurement of inclusive spin structure functions in the nucleon resonance region using polarized electron beams and polarized targets. Results on the first moment of the spin structure function for protons and neutrons will be discussed, as well as the Bjorken integral. I will argue that the helicity structure of individual resonances plays a vital role in understanding the nucleon's spin response in the domain of strong interaction QCD, and must be considered in any analysis of the nucleon spin structure at low and intermediate photon virtuality.

Recent results from Jefferson Lab

Precision measurements of the structure of nucleons and nuclei in the regime of strong interaction QCD are now possible with the availability of high current polarized electron beams, polarized targets, and recoil polarimeters, in conjunction with modern spectrometers and detector instrumentation. The authors present some recent results from the Jefferson Lab on the charge and current distributions of nucleons and nuclei. They also review measurements which relate physics at small distances to the regime where strong interaction QCD is the relevant theory.

Nucleon structure study at Jefferson Lab

With high luminosity 6 GeV electron beam, Jefferson Lab (CEBAF)'s study of the nucleon structure is focussed on the regime of strong interaction QCD. Highlights are shown on the study of the nucleon form factors, the spin structure, and the nucleon resonances. Selected new results are presented. Future upgrade to 12 GeV is briefly discussed.

Recent results from Jefferson Lab

Recent results on studies of the structure of nucleons and nuclei in the regime of strong interaction QCD are discussed. Use of high current polarized electron beams, polarized targets, and recoil polarimeters, in conjuction with modern spectrometers and detector instrumentation allow much more detailed studies of nucleon and nuclear structure than has been possible in the past. The CEBAF accelerator at Jefferson Lab was build to study the internal structure of hadrons in a regime where confinement is important and strong interaction QCD is the relevant theory. I discuss how the first experiments already make significant contributions towards an improved understanding of hadronic structure.

Probing the structure of nucleons in electromagnetic interactions

Open problems in the study of the nucleon structure using electromagnetic probes are discussed. The focus is on experimental aspects in the regime of strong interaction QCD. Significant progress in our understanding of the nucleon structure in this domain of QCD may be expected in the first decade of the next millenium. This is due to major experimental and theoretical efforts currently underway in this field.

Quark mass additivity in hadrons

The authors study mass additivity in hadrons for (i) dynamical quark masses in the chiral limit; (ii) SU(3)- and SU(4)-breaking constituent quark masses; (iii) dynamical plus current mass components in constituent quarks; (iv) current quark masses in Nambu-Goldstone mesons. In all of these case, quark mass additivity appears to be a general phenomenon whose underlying field-theoretic origin is the manifest additivity of boson tadpole insertions at both the strong interaction QCD and weak interaction QFD levels.