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1. Extraction of the Sivers function from SIDIS, Drell-Yan, and W±/Z boson production data with TMD evolution

   https://doi.org/10.1007/JHEP05(2021)151  

   Bury, Marcin ; Prokudin, Alexei ; Vladimirov, Alexey ( May 2021 , Journal of High Energy Physics)

   null (Ed.)

   A bstract We perform a global fit of the available polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS), polarized pion-induced Drell-Yan (DY) and W ± /Z boson production data at N 3 LO and NNLO accuracy of the Transverse Momentum Dependent (TMD) evolution, and extract the Sivers function for u , d , s and for sea quarks. The Qiu-Sterman function is determined in a model independent way via the operator product expansion from the extracted Sivers function. The analysis is supplemented by additional studies, such as the estimation of applicability region, the impact of the unpolarized distributions’ uncertainties, the universality of the Sivers functions, positivity constraints, the significance of the sign-change relation, and the comparison with the existing extractions. 

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2. Measurement of the Drell-Yan forward-backward asymmetry at high dilepton masses in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP08(2022)063  

   Tumasyan, A. ; Adam, W. ; Andrejkovic, J. W. ; Bergauer, T. ; Chatterjee, S. ; Damanakis, K. ; Dragicevic, M. ; Escalante Del Valle, A. ; Frühwirth, R. ; Jeitler, M. ; et al ( August 2022 , Journal of High Energy Physics)

   A bstract A measurement of the forward-backward asymmetry of pairs of oppositely charged leptons (dimuons and dielectrons) produced by the Drell-Yan process in proton-proton collisions is presented. The data sample corresponds to an integrated luminosity of 138 fb − 1 collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV. The asymmetry is measured as a function of lepton pair mass for masses larger than 170 GeV and compared with standard model predictions. An inclusive measurement across both channels and the full mass range yields an asymmetry of 0 . 612 ± 0 . 005 (stat) ± 0 . 007 (syst). As a test of lepton flavor universality, the difference between the dimuon and dielectron asymmetries is measured as well. No statistically significant deviations from standard model predictions are observed. The measurements are used to set limits on the presence of additional gauge bosons. For a Z′ boson in the sequential standard model the observed (expected) 95% confidence level lower limit on the Z′ mass is 4.4 TeV (3.7 TeV). 

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3. Reduction of PDF uncertainty in the measurement of the weak mixing angle at the ATLAS experiment *

   https://doi.org/10.1088/1674-1137/abe36d  

   Fu, Yao ; Yang, Siqi ; Liu, Minghui ; Han, Liang ; Hou, Tie-Jiun ; Schmidt, Carl ; Wang, Chen ; Yuan, C. -P. ( May 2021 , Chinese Physics C)

   We investigate the parton distribution function (PDF) uncertainty in the measurement of the effective weak mixing angleat the CERN Large Hadron Collider (LHC). The PDF-induced uncertainty is large in proton-proton collisions at the LHC due to the dilution effect. The measurement of the Drell-Yan forward-backward asymmetry () at the LHC can be used to reduce the PDF uncertainty in themeasurement. However, when including the full mass range of lepton pairs in thedata analysis, the correlation between the PDF updating procedure and theextraction leads to a sizable bias in the obtainedvalue. From our studies, we find that the bias can be significantly reduced by removing Drell-Yan events with invariant mass around theZ-pole region, while most of the sensitivity in reducing the PDF uncertainty remains. Furthermore, the lepton charge asymmetry in theWboson events as a function of the rapidity of the charged leptons,, is known to be another observable which can be used to reduce the PDF uncertainty in themeasurement. The constraint fromis complementary to that from, and thus no bias affects theextraction. The studies are performed using the error PDF Updating Method Package (ePump), which is based on Hessian updating methods. In this article, the CT14HERA2 PDF set is used as an example.

    

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4. Understanding PDF uncertainty in W boson mass measurements*

   https://doi.org/10.1088/1674-1137/ac930b  

   Gao, Jun ; Liu, Dianyu ; Xie, Keping ( December 2022 , Chinese Physics C)

   We study the dependence of the transverse mass distribution of charged leptons and the missing energy on parton distributions (PDFs) adapted toWboson mass measurements at the CDF and ATLAS experiments. We compare the shape variations of the distribution induced by different PDFs and find that the spread of predictions from different PDF sets can be significantly larger than the PDF uncertainty predicted by a specific PDF set. We suggest analyzing the experimental data using up-to-date PDFs to gain a better understanding of the PDF uncertainties inWboson mass measurements. We also perform a series of Lagrange multiplier scans to identify the constraints on the transverse mass distribution imposed by individual data sets in the CT18 global analysis. In the case of the CDF measurement, the distribution is mostly sensitive tod-quark PDFs in the intermediatexregion, which are largely constrained by DIS and Drell-Yan data on deuteron targets and Tevatron lepton charge asymmetry data.

    

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5. The Sivers asymmetry in hadronic dijet production

   https://doi.org/10.1007/JHEP02(2021)066  

   Kang, Zhong-Bo ; Lee, Kyle ; Shao, Ding Yu ; Terry, John ( February 2021 , Journal of High Energy Physics)

   null (Ed.)

   A bstract We study the single spin asymmetry in the back-to-back dijet production in transversely polarized proton-proton collisions. Such an asymmetry is generated by the Sivers functions in the incoming polarized proton. We propose a QCD formalism in terms of the transverse momentum dependent parton distribution functions, which allow us to resum the large logarithms that arise in the perturbative calculations. We make predictions for the Sivers asymmetry of hadronic dijet production at the kinematic region that is relevant to the experiment at the Relativistic Heavy Ion Collider (RHIC). We further compute the spin asymmetries in the selected positive and negative jet charge bins, to separate the contributions from u - and d -quark Sivers functions. We find that both the sign and size of our numerical results are roughly consistent with the preliminary results from the STAR collaboration at the RHIC. 

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