GeV photon beams are provided at SPring-8/LEPS facility by backward-Compton scattering (BCS) from Argon laser photon against the 8-GeV electrons inside the SPring-8 storage ring. The energy range of tagged photon by measuring the recoil electron is from 1.5 to 2.4 GeV, and enables us to study the strange meson- and baryon-photoproduction, such as £p(1020), £N(1405) and £N(1520) . In the past 30 years, other than the high-energy £N(1520) photoproduction at NINA/LAMP2 experiment, there is no further study of the £N(1520) photoproduction near the threshold. Based on this exclusive measurement at NINA/LAMP2 experiment, several theoretical calculations predict that the £N(1520) photoproduction near the threshold can be explained by t-channel K* exchange, t-channel K exchange or the contact term together with the t-channel K exchange under the gauge invariance.
This experiment was performed at SPring-8/LEPS facility with liquid hydrogen and deuterium targets by a forward spectrometer from 2002 to 2003. The electroproduction experiment with similar c.m. energy region performed by JLab/CLAS is included for comparison. We study three two-track detection modes to reconstruct the £N(1520) resonance and other resonant/non-resonant backgrounds by the invariant mass and missing mass spectra. Utilizing the one-/two-step side-band subtraction methods and Monte Carlo simulation method, we measure the differential cross sections, K^- decay asymmetries in t-channel helicity frame and photon beam asymmetries to understand the production mechanism of £N(1520) . This is the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K^{+/0} angles. It can be explained by the dominance of the contact term along with the t-channel K exchange under the satisfaction of gauge invariance. This interpretation was also compatible with the differential cross sections, K^- decay asymmetry, and the photon beam asymmetry measured in the production from protons in the forward K^+ angles.
A detector upgrade for the acceptance complement is done by introducing a time projection chamber, the configuration and operation principles except for the physics results will also be discussed in this thesis.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0713109-113454 |
| Date | 13 July 2009 |
| Creators | Chen, Jia-ye |
| Contributors | Ping-Kun Teng, Chie-Tong Kuo, Wen-Chen Chang, Ping J. Chou, Rurng-Sheng Guo |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0713109-113454 |
| Rights | unrestricted, Copyright information available at source archive |
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