| Summary: | 碩士 === 國立中央大學 === 物理研究所 === 90 ===
The cross-section of the gamma gamma->p-pbar reaction , integrated over a c.m. angular region of | cosθ* | < 0.7, is measured at two photon c.m. energy (Wγγ) between 2.0 and 4.0 GeV, . The results are obtained by using events selected from an integrated luminosity of 32.6 fb-1 of the data taken by the BELLE detector.
With the help of Monte-Carlo simulation and the application of likelihood method , a powerful proton identification method is developed. After applying the proton identification , the background events are rejected and their effect can be neglected. In addition , the amount of data is twenty times larger than that of CLEO and VENUS , It can thus give better statistics for baryon pair production , in particular at low Wγγ(< 2.2 GeV) and high Wγγ( > 2.8 Gev ) region.
The measured cross-section at Wγγ > 2.5 GeV region is dominated by W-12 term based on the conventional pQCD prediction. The prediction at Wγγ < 2.5 GeV by a newer model , the QCD sum rule , is in agreement with the result of BELLE experiment.
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