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Parton distributions in the nucleon and nuclei and hadron structure

核子、原子核和强子结构中的帕子分布

基本信息

批准号：
15540281
负责人：
KUMANO Shunzo
金额：
$ 2.24万
依托单位：
High Energy Accelerator Research Organization (2004-2006)Saga University (2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540281/
关键词：
Structure function Parton Quark Gluon QCD Q^2 evolution Nucleon Fragmentation function 原子核陽子偏極

项目摘要

(1)Polarized Parton Distribution FunctionsA global analysis has been made for determining the optimum longitudinally-polarized parton distribution functions (PDFs) from spin-asymmetry measurements of polarized lepton-nucleon scattering and pion production in polarized proton-proton collisions. Uncertainties of the polarized PDFs are estimated by the Hessian method. Results indicate that JLab data are useful for determining polarized valence-quark distributions at large x and that HERMES and COMPASS data are valuable for polarized antiquark distributions at around x〜0.1. In addition, PHENIX ones significantly reduce the uncertainty of the polarized gluon distribution.(2)Nuclear Parton Distribution FunctionsWe analyzed experimental data of nuclear structure-function ratios F_2^A/F_2^<A'> and Drell-Yan cross section ratios for obtaining optimum parton distribution functions in nuclei. Higher-order effects are included in this analysis, and new parameters are introduced in order to explain … More mass-number dependence accurately. Then, uncertainties of the nuclear PDFs are estimated by the Hessian method. Valence-quark distributions and antiquark distributions at small x are well determined ; however, the antiquark distributions are not fixed at large x. Gluon distributions have large uncertainties in the whole-x region, so that better future measurements are important. Next, we investigated effects of the difference between u_v and d_v distributions on the NuTeV sin^2θ_W anomaly. We found that such effects can partially explain the anomaly but it may not be large enough. Because such a difference cannot be accurately obtained at this stage, we need future experimental efforts.(3)Fragmentation FunctionsFragmentation functions and their uncertainties are determined by analyzing hadron-production data in electron-positron annihilation. Results indicate that gluon and light-quark fragmentation functions have large uncertainties at small Q^2. Therefore, we should be careful in describing hadron-production reactions in the small p_T region. There are large differences between widely-used functions by KKP (Kniehl, Kramer, and Potter) and Kretzer ; however, they are compatible with each other and also with our functions if the uncertainties are taken into account. Less

（1）极化部分子分布函数本文从极化轻子-核子散射和极化质子-质子碰撞中π介子产生的自旋不对称性测量出发，对最佳极化部分子分布函数（PDF）进行了全局分析。极化PDF的不对称性由Hessian方法估计。结果表明，JLab数据是有用的，以确定极化价夸克分布在大x和爱马仕和COMPASS数据是有价值的极化反夸克分布在x 0.1左右。此外，PHENIX的显着减少极化胶子分布的不确定性。（2）核部分子分布函数我们分析了核结构-功能比F_2 ^A/F_2^<A '>和Drell-Yan截面比的实验数据，以获得最佳的核部分子分布函数。高阶效应包括在这个分析中，并引入新的参数，以解释 ...更多信息质量数的依赖性。然后，核PDF的不确定度估计的海森方法。在小x时，价夸克分布和反夸克分布是确定的;然而，反夸克分布在大x时并不固定。胶子分布在整个x区域有很大的不确定性，因此未来更好的测量是很重要的。接下来，我们研究了u_v和d_v分布之间的差异对NuTeV sin^2θ_W异常的影响。我们发现，这种影响可以部分解释异常，但它可能不够大。由于现阶段无法准确获得这种差异，我们需要未来的实验努力。（3）碎裂函数通过分析正负电子湮灭中强子产生的数据，确定了碎裂函数及其不确定度。结果表明，胶子和轻夸克碎裂函数在小Q^2时具有较大的不确定性。因此，在描述小p_T区的强子产生反应时，我们应该谨慎。广泛使用的功能KKP之间有很大的差异（KKP，克雷默和波特）和Kretzer，但是，他们是相互兼容的，也与我们的功能，如果考虑到不确定性。少