Armesto Néstor, Paukkunen Hannu, Penín José Manuel, Salgado Carlos A, Zurita Pía
Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15782 Galicia, Spain.
Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15782 Galicia, Spain ; Department of Physics, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland ; Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland.
Eur Phys J C Part Fields. 2016;76(4):218. doi: 10.1140/epjc/s10052-016-4078-9. Epub 2016 Apr 21.
We report on an analysis of the impact of available experimental data on hard processes in proton-lead collisions during Run I at the large hadron collider on nuclear modifications of parton distribution functions. Our analysis is restricted to the EPS09 and DSSZ global fits. The measurements that we consider comprise production of massive gauge bosons, jets, charged hadrons and pions. This is the first time a study of nuclear PDFs includes this number of different observables. The goal of the paper is twofold: (i) checking the description of the data by nPDFs, as well as the relevance of these nuclear effects, in a quantitative manner; (ii) testing the constraining power of these data in eventual global fits, for which we use the Bayesian reweighting technique. We find an overall good, even too good, description of the data, indicating that more constraining power would require a better control over the systematic uncertainties and/or the proper proton-proton reference from LHC Run II. Some of the observables, however, show sizeable tension with specific choices of proton and nuclear PDFs. We also comment on the corresponding improvements as regards the theoretical treatment.
我们报告了对大型强子对撞机第一阶段质子-铅碰撞中硬过程的现有实验数据对部分子分布函数的核修正影响的分析。我们的分析仅限于EPS09和DSSZ全局拟合。我们考虑的测量包括大质量规范玻色子、喷注、带电强子和π介子的产生。这是首次对核部分子分布函数的研究包含如此多不同的可观测量。本文的目标有两个：（i）以定量方式检验核部分子分布函数对数据的描述以及这些核效应的相关性；（ii）测试这些数据在最终全局拟合中的约束能力，为此我们使用贝叶斯重加权技术。我们发现对数据的整体描述很好，甚至好得过头了，这表明要获得更大的约束能力需要更好地控制系统不确定性和/或来自大型强子对撞机第二阶段的合适质子-质子参考数据。然而，一些可观测量与质子和核部分子分布函数的特定选择存在相当大的差异。我们还对理论处理方面的相应改进进行了评论。
