Meson Physics at Arizona State University

Project: Research project

Description

Quantum chromodynamics (QCD) provides a successful description of the phenomena associated with strongly-interacting elementary particles at high energies. Yet, extending that understanding to the low-energy, non-perturbative regime is hampered by severe limitations in our knowledge of the excitations of the nucleon and light mesons. Since the excitation spectra for nucleons and mesons still possess major gaps and ambiguities, any QCD-based description of those hadrons and, therefore, any attempt to embed that understanding in nuclear matter faces severe handicaps. With such deficiencies in our knowledge of nucleon and meson properties, the transition between the non-perturbative and perturbative energy regimes remains mysterious. The proposed research and education program will utilize polarized tagged photon beams in Hall B at Jefferson Lab to reveal new details of light hadron structure and to help isolate the quark and gluon angular momentum and spin contributions within hadrons. The work will provide data on polarization observables in meson photoproduction, including double polarization observables, many of which have never been measured before. These data are absolutely necessary for progress in understanding the structure of the nucleon. This program will also investigate the extension of these studies above the few GeV photon energy region through participation in Hall D at Jefferson Lab, opening up the possibility of producing and identifying exotic meson states, which permit probing excitations of the gluonic flux tubes between quarks. The team of investigators is experienced in the types of experiments and analyses which form the subject of this proposal. The investigators are long-term, active members of the CEBAF Large Acceptance Spectrometer (CLAS) Collaboration at Jefferson Lab. The project director is a charter member of that collaboration and was a key member of the team building the tagged photon facility at Jefferson Lab. The investigators have led multiple data analysis efforts for CLAS experiments, which have produced publications on differential cross sections for meson photoproduction experiments under prior awards. The team includes one of the spokespersons on the approved experiment at Jefferson Lab described in the proposal which will measure polarization observables for , and meson photoproduction. Team members have also helped commission both the Jefferson Lab frozen spin target (FROST) and the coherent bremsstrahlung photon beam, essential components of the work to be undertaken. The data to be obtained on polarization observables possesses significant intellectual merit. These data are specifically aimed at enabling achievement of one of the NSAC critical milestones for hadronic physics, the combined analysis of available data on single , , and K photo-production of nucleon resonances... The FROST measurements are specifically mentioned in the White Paper from the 2007 Division of Nuclear Physics Town Hall Meeting on Hadronic Physics. The exploration of gluonic excitations with polarized photon photoproduction is one of the prime motivations for the 12 GeV upgrade at Jefferson Lab, including the construction of Hall D and the GlueX detector. The project also will also have significant broader impacts. While advancing discovery and understanding, the project incorporates teaching, training, and learning through the integrated involvement of undergraduate and graduate students and postdoctoral researchers. Participating students and postdoctoral personnel will be coached and encouraged to participate and make presentations at professional meetings. The work will strengthen existing collaborative ties in Hall B between ASU and institutions around the world, and establish a new collaborative relationship between ASU and the GlueX Collaboration. The group will continue to maintain and operate the tagged photon facility at Jefferson Lab for the us
StatusFinished
Effective start/end date9/1/1011/30/13

Funding

  • National Science Foundation (NSF): $680,000.00

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mesons
photoproduction
physics
education
photon beams
photons
polarization
acceptability
hadrons
students
excitation
proposals
quantum chromodynamics
quarks
spectrometers
disabilities
energy
elementary particles
personnel
nuclear physics