arXiv 1508.033202015-08-13hep-phnucl-th

$XY \! Z$介子产生和衰变的新动力学图象

A New Dynamical Picture for the Production and Decay of the $XY \! Z$ Mesons

Richard F. Lebed

备注：: 11 pages, includes 2 .eps figures and conference style files. To be published in the proceedings of CHARM-2015, Detroit, MI, 18-22 May 2015

摘要：

我介绍了一个全新的动力学描述奇异charmoniumlike强子，基于竞争的影响，夸克之间的强吸引力的双夸克，和无法对自己的双夸克强子化由于是一个颜色的非单线态。这个机制自然地解释了，例如，$Z(4475)$强烈地倾向于衰变为$ψ(2S)$而不是$J/ψ$，存在一个衰变为$Λ_c$重子对的态$X(4630)$，以及为什么有些而不是所有的外来粒子都位于强子阈值附近。由于高能量成分计数规则，四夸克性质的国家产生重大变化的高$s$缩放的截面，以产生这样的国家和吸引共振对生产阈值的尖点效应的潜力。最近观察到的$P_c^+$五夸克候选者被认为是自然地适合这个计划。

英文摘要：

I introduce an entirely new dynamical description for exotic charmoniumlike hadrons, based upon the competing effects of the strong attraction between quarks in a diquark, and the inability of the diquark to hadronize on its own due to being a color nonsinglet. This mechanism naturally explains, for example, the strong preference of the $Z(4475)$ to decay to $ψ(2S)$ rather than the $J/ψ$, the existence of a state $X(4630)$ that decays to $Λ_c$ baryon pairs, and why some but not all exotics lie near hadronic thresholds. Owing to high-energy constituent counting rules, the four-quark nature of the states produces major changes to both the high-$s$ scaling of cross sections for producing such states and to the potency of the cusp effect of attracting resonances to pair-production thresholds. The recently observed $P_c^+$ pentaquark candidates are seen to fit naturally into this scheme.

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英文摘要：

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