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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/7287


    Title: 雙光子碰撞產生質子反質子對的研究;Proton antiproton production via two photon collisions
    Authors: 高世權;Shin-Chuan Kao
    Contributors: 物理研究所
    Keywords: 雙光子;重子對生成;質子;反質子;微擾的量子色動力學;量子色動力學;two photon;baryon pair production;proton;anti-proton;pQCD;QCD
    Date: 2002-06-12
    Issue Date: 2009-09-22 10:54:20 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 本論文測量雙光子碰撞中產生質子反質子對的截面積,其中雙光子質心能量介於2.0 Gev 至4.0 Gev,質子動量與電子束的夾角θ*在 | cosθ* | < 0.7範圍之內。本論文數據來自2000年至2001年間,在日本KEK加速器之BELLE實驗中 事件,其總亮度為32.6 fb-1。   本論文利用Monte-Carlo事件模擬及Likelihood的方法找出挑選質子與反質子對的的最佳分析方法,其結果可完全排除背景事件的影響,保證以此方法分析BELLE實驗數據可得到不包含任何背景事件的質子反質子對事件。此外,本論文分析所用的數據量二十倍於過去的實驗,所以能有更寬廣的不變質量範圍,對於粒子生成的機制能進行更精確的檢驗。 利用本論文分析結果檢驗過去利用微擾的量子色動力學對粒子生成機制描述的理論,可確定在雙光子質心能量大於2.5 Gev 的區域中,質子與反質子生成的截面積與不變質量的-12次方成正比。此外,中研院李湘楠教授最新相關理論,QCD sum rule,對重子對生成機制的描述除了在雙光子質心能量大於2.5 Gev區域符合微擾的量子色動力學的理論預測外,其在非微擾的區域中(W < 2.5 Gev)亦可描述重子對生成機制的變化,其理論曲線並與本實驗結果相符合。 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.
    Appears in Collections:[物理研究所] 博碩士論文

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