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arXiv 2201.00574hep-ph
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$D^0-\bar{D}^0$混合的理论问题

Theoretical aspects of $D^0-\bar{D}^0$ mixing

Hiroyuki Umeeda

摘要:

$D^0-\bar{D}^0$混合中的观测量可以用算子乘积展开(OPE)进行理论分析,其中把$1/m_c$作为展开参数。由于四夸克算符的贡献被Glashow-Iliopoulos-Maiani(GIM)机制强烈抑制,因此在OPE分析中仍然不能再现宽度差的数量级。针对这一问题,我们研究了夸克-强子对偶性,这是OPE中默认的一个假设,它适用于$D^0-\bar{D}^0$混合。特别地,排他性的宽度差和包容性的对应物可以在t Hooft模型中进行比较,在大$N_c$极限下的二维QCD。结果表明,相对于四夸克算符的四维贡献,排他宽度差的数量级得到了提高,这与$D^0-\bar{D}^0$混合的实际观测定性一致.

英文摘要:

Observables in the $D^0-\bar{D}^0$ mixing can be theoretically analyzed by the operator product expansion (OPE), in which $1/m_c$ is regarded as an expansion parameter. Since the contributions of four-quark operators are strongly suppressed by the Glashow-Iliopoulos-Maiani (GIM) mechanism, the order of magnitude of the width difference is still not reproduced in the OPE analysis. In view of this issue, quark-hadron duality, an assumption that is tacitly made in the OPE, is studied for the $D^0-\bar{D}^0$ mixing. In particular, the exclusive width difference and the inclusive counterpart can be compared within the 't Hooft model, two-dimensional QCD in the large-$N_c$ limit. It is shown that the order of magnitude of the exclusive width difference is enhanced relative to the 4D-like inclusive contributions of the four-quark operators, that is qualitatively consistent with the realistic observation of the $D^0-\bar{D}^0$ mixing.

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