γγ^＊→π0跃迁的形状因子对共振态谱有限宽度的依赖性  

Dependence of Form Factors of γγ^＊→π0 Transition to the Finiteness of the Resonance Widths

作　　者：张胜昔[1] 张振宇[1] 刘觉平[1] 

机构地区：[1]武汉大学物理科学与技术学院,湖北武汉430072

出　　处：《武汉大学学报（理学版）》2007年第1期63-66,共4页Journal of Wuhan University:Natural Science Edition

基　　金：国家自然科学基金(10075036);北京正负电子对撞机国家实验室开放课题基金;北京谱仪合作组研究基金资助项目

摘　　要：基于量子色动力学(QCD)定域光锥求和规则,用ρ-ω介子共振态有限宽度近似取代了通常的零宽度近似,采用对偶解析延拓(ACD)方法,在色散关系中取N阶多项式为权重函数来清除或削弱共振谱和量子色动力学中不可靠区域的积分的影响,通过分析计算得到了γγ*→π0形状因子Fγγ*→π0(0,Q2)的解析式及其数值结果.结果表明由零宽度和有限宽度的共振谱形式得到的形状因子大致相同,且与实验数据符合,说明Fγγ*→π0(0,Q2)对共振态谱宽度的大小仅有较弱的依赖性,并验证了π介子光锥波函数渐近形式的正确性.In the framework of the local quantum chromodynamics sum rules, instead of the usual zerowidth approximation, the finite-width approximation for the resonances, the ρ-ω mesons, is used to investigate the form factor of the transition γγ^＊→π0. According to the method of the analytic continuation by duality, the weight function, the polynomial of a low order N, is added to the dispersion integral to annihilate the integrand in the region where both resonance saturation and the QCD asymptotic expression are least reliable. The resultant form factor in the cases for the zero-and finite-widths are almost the same, and agree well with the experimental measurements, it thus shows a weak dependence of the form factor on the finiteness of the widths of the resonances, and justifies the correctness of the asymptotic form of the pion light-cone wave function.

关 键 词：量子色动力学 定域光锥求和规则 形状因子 

分 类 号：O413.4[理学—理论物理]