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Creators/Authors contains: "Yuan, C.-P."

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  1. Free, publicly-accessible full text available July 1, 2023
  2. Free, publicly-accessible full text available June 1, 2023
  3. Abstract

    We propose a new observable for the measurement of the forward–backward asymmetry$$(A_{FB})$$(AFB)in Drell–Yan lepton production. At hadron colliders, the$$A_{FB}$$AFBdistribution is sensitive to both the electroweak (EW) fundamental parameter$$\sin ^{2} \theta _{W}$$sin2θW, the weak mixing angle, and the parton distribution functions (PDFs). Hence, the determination of$$\sin ^{2} \theta _{W}$$sin2θWand the updating of PDFs by directly using the same$$A_{FB}$$AFBspectrum are strongly correlated. This correlation would introduce large bias or uncertainty into both precise measurements of EW and PDF sectors. In this article, we show that the sensitivity of$$A_{FB}$$AFBon$$\sin ^{2} \theta _{W}$$sin2θWis dominated by its average value around theZpole region, while the shape (or gradient) of the$$A_{FB}$$AFBspectrum is insensitive to$$\sin ^{2} \theta _{W}$$sin2θWand contains important information on the PDF modeling. Accordingly, a new observable related to the gradient of the spectrum is introduced, and demonstrated to be able to significantly reduce the potential bias on the determination of$$\sin ^{2} \theta _{W}$$sin2θWwhen updating the PDFs using the same$$A_{FB}$$AFBdata.

  4. Free, publicly-accessible full text available March 1, 2023
  5. Sissa (Ed.)
    We discuss recent CTEQ-TEA group activities after the publication of the CT18 global analysis of parton distribution functions (PDFs) in the proton. In particular, we discuss a new calculation for the photon content in the proton, termed as CT18lux and CT18qed PDFs, and the impact of novel charm- and bottom-quark production cross section measurements at HERA on the CT18 global analysis.
    Free, publicly-accessible full text available March 8, 2023
  6. Abstract A precise knowledge of the quark and gluon structure of the proton, encoded by the parton distribution functions (PDFs), is of paramount importance for the interpretation of high-energy processes at present and future lepton–hadron and hadron–hadron colliders. Motivated by recent progress in the PDF determinations carried out by the CT, MSHT, and NNPDF groups, we present an updated combination of global PDF fits: PDF4LHC21. It is based on the Monte Carlo combination of the CT18, MSHT20, and NNPDF3.1 sets followed by either its Hessian reduction or its replica compression. Extensive benchmark studies are carried out in order to disentangle the origin of the differences between the three global PDF sets. In particular, dedicated fits based on almost identical theory settings and input datasets are performed by the three groups, highlighting the role played by the respective fitting methodologies. We compare the new PDF4LHC21 combination with its predecessor, PDF4LHC15, demonstrating their good overall consistency and a modest reduction of PDF uncertainties for key LHC processes such as electroweak gauge boson production and Higgs boson production in gluon fusion. We study the phenomenological implications of PDF4LHC21 for a representative selection of inclusive, fiducial, and differential cross sections at the LHC. Themore »PDF4LHC21 combination is made available via the LHAPDF library and provides a robust, user-friendly, and efficient method to estimate the PDF uncertainties associated to theoretical calculations for the upcoming Run III of the LHC and beyond.« less
    Free, publicly-accessible full text available July 5, 2023
  7. A bstract Understanding how sea quarks behave inside a nucleon is one of the most important physics goals of the proposed Electron-Ion Collider in China (EicC), which is designed to have a 3.5 GeV polarized electron beam (80% polarization) colliding with a 20 GeV polarized proton beam (70% polarization) at instantaneous luminosity of 2 × 10 33 cm − 2 s − 1 . A specific topic at EicC is to understand the polarization of individual quarks inside a longitudinally polarized nucleon. The potential of various future EicC data, including the inclusive and semi-inclusive deep inelastic scattering data from both doubly polarized electron-proton and electron- 3 He collisions, to reduce the uncertainties of parton helicity distributions is explored at the next-to-leading order in QCD, using the Error PDF Updating Method Package ( e P ump ) which is based on the Hessian profiling method. We show that the semi-inclusive data are well able to provide good separation between flavour distributions, and to constrain their uncertainties in the x > 0 . 005 region, especially when electron- 3 He collisions, acting as effective electron-neutron collisions, are taken into account. To enable this study, we have generated a Hessian representation of themore »DSSV14 set of PDF replicas, named DSSV14H PDFs.« less
  8. Abstract

    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 themore »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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