A study of exclusive quarkonium decays within the effective field theory framework

有效场论框架内专有夸克素衰变的研究

• 批准号: 445769443
• 负责人: Dr. Nikolay Kivel, Ph.D.
• 金额: --
• 依托单位: Arbeitsgruppe Theoretische Teilchen und Kernphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/445769443?language=en
• 关键词: study; exclusive; quarkonium; decays; within

This proposal is dedicated to investigation of exclusive quarkonium decays within the effective theory frameworks. Many new precise data about various exclusive decays of charmonium and bottomonium states have been obtained during the last years by the CLEO, BABAR, BELLE, BES and LHCb collaborations. At present, the BES III, BELLE II and LHCb experiments continue to collect the data. Many accurate measurements are also expected in the near future from the PANDA@FAIR experiments. Although the spectrum of low-lying quarkonia is at present reasonably well understood, many of it decays are not yet well understood or are puzzling. A successful description of exclusive decays will shed light on the complicated underlying QCD dynamics involving different scales.In the first part of the project I plan to study the baryon-antibaryon decays of $S$- and $P$-wave charmonia. These decays are sufficiently well measured for many various final states and include $p, n, \Lambda, \Sigma$ and $\Xi$ mesons. A description of these decays depends on the wave functions of charmonium and baryons. For a long time is was accepted that the $3$-quark leading-twist distribution amplitude (DA), which is associated with the baryon wave functions, provides a reasonable estimate of the decay widths. However, the new calculations of various baryon DAs, which were made in QCD sum rules and on the lattice, indicate that the effect from higher twist DAs can be sufficiently large. This strongly affect the existing description of charmonia decays. This point is also supported by the large values of the branching ratios for various helicity suppressed decays. The latter have not been even systematically considered. The goal of this project is to study the $S$- and $P$- charmonia decays taking into account the higher twist DAs of the baryons. The second part of the project is devoted to a study of the colour-octet contributions in decays of $^3S_1$ charmonia into $PV$ final states, with $PV=\rho\pi, K^*\bar K, \dots$. The measured ratio of the $\Psi(2S)$ and $J/\Psi$ branching ratios is about two order of magnitude smaller than one expected from the leading-order description. A similar effect is also observed for many other two-body hadronic channels. The colour-octet contribution is often proposed to be responsible for an explanation of this effect. However, a systematic description of such a contribution for exclusive decays have not yet been suggested. The goal of this project is to study the colour-octet mechanism in the $PV$-decays in a systematic way using the effective field theory framework. It is planned to define the relevant colour-octet operators, to study their properties and the mixing with the colour-singlet operators, to study colour-octet matrix elements and their role in the description of the decay width.

该建议致力于研究有效理论框架中的独家夸克腐烂。克莱奥（Cleo），巴巴尔（Babar），贝尔（Belle），BES和LHCB合作获得了许多有关慈善和底部国家的各种独家衰减的新的精确数据。目前，BES III，Belle II和LHCB实验继续收集数据。预计在不久的将来，Panda@Fair实验也有许多准确的测量。尽管目前的低洼夸克尼亚的范围众所周知，但其中许多衰减尚未得到充分理解或令人困惑。对独家衰减的成功描述将阐明涉及不同尺度的复杂基础QCD动态。 这些衰减对许多最终状态进行了足够的测量，包括$ p，n，\ lambda，\ sigma $和$ \ xi $梅森。 这些衰变的描述取决于炭和重子的波函数。很长一段时间以来，人们认为，与Baryon Wave函数相关的3美元Quark领先分配幅度（DA）提供了对衰减宽度的合理估计。但是，在QCD和晶格中制定的各种Baryon DA的新计算表明，较高扭曲DAS的影响可能足够大。 这强烈影响了charmonia衰变的现有描述。对于各种螺旋性抑制的衰减，分支比的较大值也支持了这一点。后者甚至没有被系统地考虑。 该项目的目的是考虑$ S $和$ p $ - charmonia腐烂，考虑到Baryons的更高扭曲。 该项目的第二部分致力于研究$^3S_1 $ CHARMONIA $^3S_1 $ charmonia to $ pv $最终状态的研究，其中$ pv = \ rho \ pi，k^*\ bar k，k k，\ dots $。 $ \ psi（2s）$和$ j/\ psi $分支比率的测量比率大约要比前阶说明预期的一个数量级小。 对于许多其他两体Hadronic通道，也观察到类似的效果。 通常提出颜色贡献的贡献是为了解释这种效果。 但是，尚未提出对这种对独家衰减的贡献的系统描述。该项目的目的是使用有效的现场理论框架以系统的方式研究$ PV $ - 订单中的颜色octet机制。计划定义相关的彩色运算符，研究其特性和与颜色单缝操作员的混合，以研究颜色octet矩阵元素及其在衰减宽度描述中的作用。