Recent high precision experimental data from a variety of hadronic processes opens new opportunities for determination of the collinear parton distribution functions (PDFs) of the proton. In fact, the wealth of information from experiments such as the Large Hadron Collider (LHC) and others, makes it difficult to quickly assess the impact on the PDFs, short of performing computationally expensive global fits. As an alternative, we explore new methods for quantifying the potential impact of experimental data on the extraction of proton PDFs. Our approach relies crucially on the correlation between theory-data residuals and the PDFs themselves, as well as on a newly defined quantity -the sensitivity -which represents an extension of the correlation and reflects both PDF-driven and experimental uncertainties. This approach is realized in a new, publicly available analysis package PDFSENSE, which operates with these statistical measures to identify particularly sensitive experiments, weigh their relative or potential impact on PDFs, and visualize their detailed distributions in a space of the parton momentum fraction x and factorization scale µ. This tool offers a new means of understanding the influence of individual measurements in existing fits, as well as a predictive device for directing future fits toward the highest impact data and assumptions. XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS2018)16-20 April 2018 Kobe, Japan * The webpage for the PDFSense tool is: https://metapdf.hepforge.org/PDFSense/ We acknowledge the hospitality of CERN, DESY, and Fermilab where a portion of this work was performed.
We study the possibility of intrinsic (nonperturbative) charm in parton distribution functions (PDF) of the proton, within the context of the CT10 next-to-next-to-leading order global analysis. Three models for the intrinsic charm (IC) quark content are compared: (i)ĉðxÞ ¼ 0 (zero-IC model); (ii)ĉðxÞ is parametrized by a valence-like parton distribution (BHPS model); (iii)ĉðxÞ is parametrized by a sea-like parton distribution (SEA model). In these models, the intrinsic charm content,ĉðxÞ, is included in the charm PDF at the matching scale Q c ¼ m c ¼ 1.3 GeV. The best fits to data are constructed and compared. Correlations between the value of m c and the amount of IC are also considered.
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. The 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.
We explore a new possibility of electroweak baryogenesis in the next-to-minimal supersymmetric standard model. In this model, a strong first-order electroweak phase transition can be achieved due to the additional singlet Higgs field. The new impact of its superpartner (singlino) on the baryon asymmetry is investigated by employing the closed-time-path formalism. We find that the CP violating source term fueled by the singlino could be large enough to generate the observed baryon asymmetry of the Universe without any conflicts with the current constraints from the non-observation of the Thallium, neutron and Mercury electric dipole moments.
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