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Experimental Study of the Charged Pion Photoprodcution on Deuteron

Author: HanYunCheng
Tutor: WangTieShan
School: Lanzhou University
Course: Particle Physics and Nuclear Physics
Keywords: NKS2 spectrometer Tagged photon system Pion photoproduction Deuteron Cross section
CLC: O571.424
Type: PhD thesis
Year: 2010
Downloads: 43
Quote: 1
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Abstract


Pion photoproduction from the nucleon has been proved as one of the best mechanisms to study the nucleon and its resonances as well as to study the role of the pion and resonances in nuclei. Single pion photoproduction is the standard method for the investigation of the electromagnetic resonance couplings, being one of the most important testing grounds for hadron models. For a systematic analysis of single-pion photoproduction such as a full multipole analysis including the isospin structure of the amplitudes, detailed measurements of photoproduc-tion on neutrons are needed. Only with good data on both proton and neutron targets one can hope to disentangle the isoscalar and isovector electromagnetic couplings of the various N andΔresonances, as well as the isospin properties of the non-resonant background amplitudes. The amount of experimental data on protons and the phenomenological analysis of these reactions is rather satis-factory. On the contrary the experimental data on neutrons is, in this respect, still insufficient. Most of the data from deuteron targets still stem from measure-ments with untagged photon beams. Often, only ratios of proton-neutron cross sections have been measured with at times insufficient separation of single and double pion production channels. The need for better data is obvious.The photoproduction of pion has been studied with NKS2 in an energy range from 0.8 to 1.1 GeV at Laboratory of Nuclear Science, Tohoku University (LNS-Tohoku). The real photon beam is provided by the tagged photon system of LNS-Tohoku. The reactionγd→π-pp is selected for the calibration of the photon tagging system and the evaluation for performance of NKS2. Both total and differential cross sections of theγd→π-pp reaction are measured with photon energy from 0.8 to 1.1 GeV. The results of present work are compared with the other available experimental data and theoretical calculations.NKS2 is large acceptance spectrometer for measuring charged particles, which consists of two types of drift chambers, inner hodoscopes (IH), outer ho-doscopes (OH), and electron veto counters (EV). The design, composition of NKS2 and the analysis, test of it are described in this dissertation.The reactionγd→π-pp is selected for the calibration of the photon tagging system and the evaluation for performance of NKS2. The calibration, which is based on a complete kinematical measurement of the final state particles, agrees with the design of the tagging system and the previous measurement using the electron-positron pair production.The agreement indicates that both NKS2 and the tagging system perform well. The possibility of photon energy calibration is thus exhibited using a complete kinematical measurement of the reaction ofγd→π-pp. This is the first report which calibrates the photon tagging system using hadron channels.Both total and differential cross sections of theγd→π-pp reaction are measured with photon energy from 0.8 to 1.1 GeV. The quasi-free (QF) process on bound neutron inside deuteron and non-quasi-free (NQF) contributions are derived separately. The photon energy precision of the cross-section ofγd→π-pp is improved to be 6 MeV, and theπ-emission angle covers the region of 20°-160°in the center of yd system. The cross-section ofγd→(π-Pp)NQF is derived at the first time. This result would be useful to study the influence of deuteron environment and final state interaction on the photoproduction process.The precision data presented in this dissertation will help us further con-strain theoretical analysis and will allow for a precise determination of the cor-responding neutron electromagnetic parameters.

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