Nucleon Structure and Nuclear Force Studies

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This award is to support the research activities of two professors,their graduate students and a Senior Research Associate at Kent StateUniversity in the area of experimental medium-energy nuclear physics. The general objectives are the study of the structure of the nucleon(neutron or proton) and the nature of the nuclear force. This group isinvolved in experiments being performed, or to be performed at theJefferson National Accelerator Facility (Jlab) in Virginia and at theRelativistic Heavy-Ion Collider (RHIC) on Long Island, New York. Anexperiment is in progress at Jlab to determine the charge distributioninside the neutron. The neutron, while neutral overall, is known toconsist of objects with both positive and negative charges. Theseobjects are called "quarks". The quarks are held together by theexchange of particles called "gluons". Exactly how the quarks combine,move, and interact inside the neutron is not known. A precisemeasurement of the charge distribution, called the Electric Form Factor,will provide one of the most sensitive tests available of various modelsof the neutron structure. These measurements are only recently possibleand require the electron beam characteristics now available at Jlab andinvolve the use of a large-volume neutron polarimeter developed by thisgroup in experiments performed during the last decade at otheraccelerator facilities. The development, installation, calibration, andoperation of the polarimeter represents the unique contribution of thisgroup to this important experiment. This group plans also to performanother experiment at Jlab to study short-range correlation betweennucleons inside nuclei. Such short-range correlations are known toexist, but the exact nature and strength of such correlations are onlypoorly determined. This group will bring its expertise with neutrondetectors to help study such correlations involving neutrons.This group has recently joined an effort planned to study interactionsbetween colliding beams of polarized protons using the "STAR" detectorat RHIC (STAR stands for Solenoidal Tracker at RHIC). The object ofthis study is to determine the exact origin of the intrinsic angularmomentum, or spin, of the proton. The spin, like the chargedistribution, arises from the existence, interactions and movements ofthe constituents of the proton, generally believed to be the quarks andgluons. To date, only the contributions from the quarks has beendetermined; this project offers the possibility of determining thecontribution to the spin of the proton due to gluons. In order tomeasure these contributions, it is necessary to observe hadronic jetsproduced at relatively small angles in the collisions. This group,together with a collaboration of other researchers from IndianaUniversity, Argonne National Laboratory, and others, will construct anew "end-cap calorimeter" to be installed at one end of the present STARdetector at RHIC. It will be this group's responsibility to providecharacterizations and calibrations of the multi-anode photomultipliertubes used for particle detection in this new calorimeter.