Parton distributions from LHC, HERA, Tevatron and fixed target data: MSHT20 PDFs
Parton distributions from LHC, HERA, Tevatron and fixed target data: MSHT20 PDFs
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DOI：
10.1140/epjc/s10052-021-09057-0
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发表时间：
2021-04-01
影响因子：
4.4
通讯作者：
Thorne, R. S.
中科院分区：
文献类型：
--
作者：
Bailey, S.;Cridge, T.;Thorne, R. S.
我们提出了一套新的MSHT 20部分子分布函数（PDF）的质子，从全球可用的硬散射数据的分析。PDF可在NNLO、NLO和LO上获得，并取代MMHT 14集。它们是使用相同的基本框架获得的，但是参数化现在被调整和扩展，并且有32对特征向量PDF。我们还包括大量的新的数据集：从最终HERA合并的数据，总的和重味结构功能，最终Tevatron数据，特别是大量的新的LHC 7和8 TeV的数据集矢量玻色子生产，包括喷气机和顶夸克分布。我们包括了所有数据集的NNLO QCD校正，在拟合中发挥了重要作用，并在相关的NLO EW校正。我们发现这些更新对PDF有重要影响，并且NNLO拟合首次强烈优于NLO，反映了拟合中包含的数据范围更广，特别是精度更高。在许多情况下（尽管不是所有情况下），中心值发生了一些变化，PDF的不确定性显著降低。尽管如此，PDF和由此产生的预测通常在MMHT 14结果的一个标准差内。主要的变化是由于改进的参数化和新的精确数据，在小x处的u - d价夸克差，由于大大改进的参数化，在小x处的（d）过bar，（u）过bar差，以及由于LHC W，Z数据的影响和包括新的中微子DIS中双μ子产生的NNLO修正的奇异夸克PDF。我们讨论了我们结果的唯象影响。一般来说，在预测过程中，如希格斯粒子，顶夸克对和W，Z生产后LHC运行II能量的不确定性降低。
We present the new MSHT20 set of parton distribution functions (PDFs) of the proton, determined from global analyses of the available hard scattering data. The PDFs aremade available at NNLO, NLO, and LO, and supersede the MMHT14 sets. They are obtained using the same basic framework, but the parameterisation is now adapted and extended, and there are 32 pairs of eigenvector PDFs. We also include a large number of new data sets: from the final HERA combined data on total and heavy flavour structure functions, to final Tevatron data, and in particular a significant number of new LHC 7 and 8 TeV data sets on vector boson production, inclusive jets and top quark distributions. We include up to NNLO QCD corrections for all data sets that play a major role in the fit, and NLO EW corrections where relevant. We find that these updates have an important impact on the PDFs, and for the first time the NNLO fit is strongly favoured over the NLO, reflecting the wider range and in particular increased precision of data included in the fit. There are some changes to central values and a significant reduction in the uncertainties of the PDFs in many, though not all, cases. Nonetheless, the PDFs and the resulting predictions are generally within one standard deviation of the MMHT14 results. The major changes are the u - d valence quark difference at small x, due to the improved parameterisation and new precise data, the (d) over bar,(u) over bar difference at small x, due to a much improved parameterisation, and the strange quark PDF due to the effect of LHC W, Z data and inclusion of new NNLO corrections for dimuon production in neutrino DIS. We discuss the phenomenological impact of our results, and in general find reduced uncertainties in predictions for processes such as Higgs, top quark pair and W, Z production at post LHC Run-II energies.