Three-body Forces in Photoreactions on 3He

Thesis/Dissertation · Wed Feb 12 00:00:00 EST 2003

DOI:https://doi.org/10.2172/824932· OSTI ID:824932

Niccolai, Silvia ^[1]

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1. George Washington Univ., Washington, DC (United States)

We have measured the three-body photobreakup of ³He with the tagged photon beam and the CEBAF Large Acceptance Spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility, in the photon energy range between 0.35 GeV and 1.55 GeV. This measurement constitutes a wide-ranging survey of two- and three-body processes in the gamma³He → ppn reaction channel, thanks to the high statistics and large kinematic coverage obtained with the CLAS. Total and partially integrated differential cross sections for the full ppn data set and for selected kinematics were extracted and are compared to theoretical predictions of Laget (up to 1.0 GeV). At low photon energies, the calculations are generally in fair agreement with the data. The comparison shows evidence of strong contributions of three-body absorption mechanisms, especially in the star kinematics, a symmetric configuration of the three final-state nucleons. Mostly the effects of two-body absorption mechanisms are se en, as expected, in the pp-pair-breakup kinematics, where the neutron does not participate in the reaction. The quasi-two-body breakup shows angular distributions consistent with preliminary gamma³He → pd results, extracted from our experiment. The ratio of cross sections for the star configuration and for the two-body kinematics, shows a maximum for three-body effects at a photon energy of about 0.5 GeV, corresponding to a reduced photon wavelength of 0.4 fm. The 4pi-integrated cross section is in excellent agreement with previous experimental results from DAPHNE up to 800 MeV; no previous results have been obtained above this energy.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 824932
• Report Number(s): JLAB-PHY-03-39; DOE/ER/40150-2763; TRN: US0402258
• Resource Relation: Other Information: TH: Thesis; Thesis information not provided; PBD: 1 Feb 2003
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ABSORPTION
ANGULAR DISTRIBUTION
CEBAF ACCELERATOR
CONFIGURATION
CROSS SECTIONS
DIFFERENTIAL CROSS SECTIONS
ENERGY RANGE
NEUTRONS
NUCLEONS
PHOTON BEAMS
PHOTONS
SPECTROMETERS
STARS
STATISTICS
WAVELENGTHS