Extended parameterisations for MSTW PDFs and their effect on lepton charge asymmetry from W decays
Extended parameterisations for MSTW PDFs and their effect on lepton charge asymmetry from W decays
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MSTW PDF 的扩展参数化及其对 W 衰变引起的轻子电荷不对称性的影响
DOI：
10.1140/epjc/s10052-013-2318-9
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
G. Watt
中科院分区：
文献类型：
--
作者：
A. Martin;A. Mathijssen;W. Stirling;R. Thorne;B. Watt;G. Watt
我们研究了使用Chebyshev多项式扩展输入部分子分布函数（PDF）的标准MSTW参数化的效果，而不是通常的表达式，其中包含形式为（1+ λ x 0. 5 +γx）的因子。我们发现的证据表明，四个权力的多项式一般是足够的高精度。将其应用于价夸克和海夸克，胶子已经足够灵活，只需要两个功率，我们发现在整体拟合的改善，但只有在小x价上夸克PDF，uV的显着变化。我们调查的影响，也扩大，并使更灵活，“核”的修正，以氘核结构的功能。我们表明，扩展的“切比雪夫”参数化的结果在一个更好的稳定性，所需的最佳拟合的“全球”数据的氘核修正。由此产生的PDF有一个显着的，但不显着，改变价下夸克分布，dV。结果表明，对于扩展的MSTW PDF集，其不确定性可以使用23，而不是通常的20，正交的“不确定性”特征向量。这在没有和有扩展的氘核修正的情况下都是正确的。由于主要的影响是在价夸克，我们提出了一个详细的研究的依赖性的价海分离的衰变轻子电荷不对称性的预测，导致在LHC的W±生产，说明PDF和探测不同的实验方案的x范围。我们表明，修改后的MSTW PDF作出显着改善的预测，这些数据在大型强子对撞机，特别是高值的pT削减的衰变轻子。然而，这是一个特殊的情况，因为不对称性对价海细节非常敏感，特别是在低轻子快度下对x \sim M_{W}/\sqrt{s}$的价PDF的组合uV−dV。我们表明，各种各样的总截面的预测是非常相似的，使用MSTW 2008 PDF得到的，变化比PDF的不确定性小得多。
We investigate the effect of extending the standard MSTW parameterisation of input parton distribution functions (PDFs) using Chebyshev polynomials, rather than the usual expressions which involve a factor of the form (1+ϵx0.5+γx). We find evidence that four powers in the polynomial are generally sufficient for high precision. Applying this to valence and sea quarks, the gluon already being sufficiently flexible and needing only two powers, we find an improvement in the global fit, but a significant change only in the small-x valence up-quark PDF, uV. We investigate the effect of also extending, and making more flexible, the ‘nuclear’ correction to deuteron structure functions. We show that the extended ‘Chebyshev’ parameterisation results in an improved stability in the deuteron corrections that are required for the best fit to the ‘global’ data. The resulting PDFs have a significantly, but not dramatically, altered valence down-quark distribution, dV. It is shown that, for the extended set of MSTW PDFs, their uncertainties can be obtained using 23, rather than the usual 20, orthogonal ‘uncertainty’ eigenvectors. This is true both without and with extended deuteron corrections. Since the dominant effect is on the valence quarks, we present a detailed study of the dependence of the valence–sea separation on the predictions for the decay lepton charge asymmetry which results from W± production at the LHC, illustrating the PDFs and the x range probed for different experimental scenarios. We show that the modified MSTW PDFs make significantly improved predictions for these data at the LHC, particularly for high values of the pT cut of the decay lepton. However, this is a special case, since the asymmetry is extremely sensitive to valence–sea details, and in particular to the combination uV−dV of valence PDFs for $x \sim M_{W}/\sqrt{s}$ at low lepton rapidities. We show that the predictions for a wide variety of total cross sections are very similar to those obtained using the MSTW2008 PDFs, with changes being much smaller than the PDF uncertainties.
影响因子：
5
作者：
Alekhin, S.;Bluemlein, J.;Moch, S.
通讯作者：
Moch, S.
影响因子：
2.8
作者：
Ball, Richard D.;Bertone, Valerio;Ubiali, Maria
通讯作者：
Ubiali, Maria