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-  2018 

强子结构的协变手征有效理论分析

DOI: 10.3969/j.issn.1000-5641.2018.03.013

Keywords: 手征有效场论, 强子结构, 协变框架, 定域项, 重重子手征微扰论
Key words: chiral effective field theory hadron structures covariant framework local terms heavy baryon chiral perturbation theory

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Abstract:

摘要 采用协变手征有效场论,在一圈图水平上计算了与核子部分子分布函数相关的低能区Twist-2算符矩阵元,发现破坏手征幂次规则的项全部是依赖核子质量的定域项,可通过定域抵消项减除,余下的完全是满足手征幂次规则的贡献,与非相对论的重重子手征微扰论(Heavy Baryon Chiral Perturbation Theory,HBChPT)框架下的结果一致.又因重重子手征微扰论中重子传播子的过度简化可能导致错误的核子阈值行为,故本研究结果佐证了在协变手征微扰框架下采用恰当的减除手段计算,既可得到正确的核子阈值行为,又能得到满足手征幂次规则的结果,从而更适合作为研究强子物理的有效场理论框架.
Abstract:The matrix elements of twist-2 operators related to nucleon-parton distributions were calculated at one-loop level in the framework of covariant chiral perturbation theory. It was found that all who violate chiral power counting reside in the local terms depending on nucleon mass; hence, they could be readily removed through local counterterms, namely the contributions left over fulfill chiral power counting just like with HBChPT (Heavy Baryon Chiral Perturbation Theory). Meanwhile, one may arrive at incorrect behaviors near baryon thresholds due to the oversimplification of baryon propagators in HBChPT. The results here further support the proposition that the approach of covariant chiral perturbation theory with proper subtractions could both preserve the correct threshold behaviors and fulfill chiral power counting, and hence is a framework more suitable for investigating hadron physics.

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