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Novel corrections to the momentum sum rule for nuclear structure functions

PHYSICS LETTERS B 2022年 824卷

作者： Brodsky, Stanley J. Lyubovitskij, Valery E. Schmidt, Ivan Stanford Univ SLAC Natl Accelerator Lab Stanford CA 94309 USA Univ Tubingen Kepler Ctr Astro & Particle Phys Inst Theoret Phys Morgenstelle 14 D-72076 Tubingen Germany Univ Tecn Federico Santa Maria Dept Fis Casilla 110-V Valparaiso Chile Univ Tecn Federico Santa Maria Ctr Cient Tecnol Valparaiso CCTval Casilla 110 Valparaiso Chile High Energy Frontier SAPHIR ANID Millennium Inst Subat Phys Fernandez Concha 700 Santiago Chile

We address novel features of deep inelastic lepton scattering on nuclei at small Bjorken variable x(Bj). In this regime the lepton-nuclear cross section involves the interference between the standard leptonquark scattering amplitude for the deep inelastic scattering (DIS) process on a single nucleon and a two-step process where diffractive scattering on a first nucleon combines with the amplitude for DIS on a second nucleon. The phases associated with the t-channel exchanges to the diffractive amplitude can produce either a destructive or constructive quantum-mechanical interference of the one-step and two-step amplitudes. This provides a mechanism regulating the respective amounts of shadowing suppression and anti-shadowing enhancement at low x(Bj). Furthermore, the standard leading-twist operator product and handbag diagram analyses of the forward virtual Compton amplitude on the nucleus are inapplicable, barring a conventional probabilistic interpretation. A main observable consequence is the impossibility of extracting momentum and spin sum rules from nuclear structure functions. We present numerical predictions supporting this picture and test them against DIS neutrino-nucleus and charged-leptonnucleus scattering data. (C) 2021 The Author(s). Published by Elsevier B.V.

关键词： Deep inelastic scattering Diffractive deep inelastic scattering parton distribution functions Nuclear structure functions Momentum sum rules Operator expansion

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The PDF4LHC21 combination of global PDF fits for the LHC Run III*

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JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS 2022年第8期49卷 080501-080501页

作者： Ball, Richard D. Butterworth, Jon Cooper-Sarkar, Amanda M. Courtoy, Aurore Cridge, Thomas De Roeck, Albert Feltesse, Joel Forte, Stefano Giuli, Francesco Gwenlan, Claire Harland-Lang, Lucian A. Hobbs, T. J. Hou, Tie-Jiun Huston, Joey McNulty, Ronan Nadolsky, Pavel M. Nocera, Emanuele R. Rabemananjara, Tanjona R. Rojo, Juan Thorne, Robert S. Xie, Keping Yuan, C-P Univ Edinburgh Higgs Ctr JCMB Mayfield Rd Edinburgh EH9 3JZ Midlothian Scotland UCL Dept Phys & Astron London England Univ Oxford Dept Phys Oxford England Univ Nacl Autonoma Mexico Inst Fis Apartado Postal 20-364 Mexico City 01000 DF Mexico CERN CH-1211 Geneva Switzerland Univ Paris Saclay CEA IRFU F-91191 Gif Sur Yvette France Univ Milan Dipartimento Fis Tif Lab Via Celoria 16 I-20133 Milan Italy INFN Sez Milano Via Celoria 16 I-20133 Milan Italy Rudolf Peierls Ctr Beecroft BldgParks Rd Oxford England Fermilab Natl Accelerator Lab Batavia IL 60510 USA IIT Dept Phys Chicago IL 60616 USA Northeastern Univ Coll Sci Dept Phys Shenyang 110819 Peoples R China Michigan State Univ Dept Phys & Astron E Lansing MI 48824 USA Univ Coll Dublin Sch Phys Dublin 4 Ireland Southern Methodist Univ Dept Phys Dallas TX 75275 USA Vrije Univ Dept Phys & Astron NL-1081 HV Amsterdam Netherlands Nikhef Theory Grp Sci Pk 105 NL-1098 XG Amsterdam Netherlands Univ Pittsburgh Dept Phys & Astron Pittsburgh PA 15260 USA

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.

关键词： particle physics parton distribution functions large hadron collider quantum chromodynamics

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Light mesons with one dynamical gluon on the light front

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PHYSICS LETTERS B 2022年 825卷

作者： Lan, Jiangshan Fu, Kaiyu Mondal, Chandan Zhao, Xingbo Vary, James P. Lanzhou Univ Lanzhou 730000 Peoples R China Chinese Acad Sci Inst Modern Phys Lanzhou 730000 Peoples R China Univ Chinese Acad Sci Sch Nucl Sci & Technol Beijing 100049 Peoples R China Chinese Acad Sci Inst Modern Phys CAS Key Lab High Precis Nucl Spect Lanzhou 730000 Peoples R China Iowa State Univ Dept Phys & Astron Ames IA 50011 USA

We obtain the light meson mass spectroscopy from the light-front quantum chromodynamics (QCD) Hamiltonian, determined for their constituent quark-antiquark and quark-antiquark-gluon Fock components, together with a three-dimensional confinement. The eigenvectors of the light-front effective Hamiltonian provide a good quality description of the pion electromagnetic form factor, decay constant, and the valence quark distribution functions following QCD scale evolution. We also show that the pion's gluon densities can be probed through the pion-nucleus induced J/psi production data. Our pion par ton distribution functions provide excellent agreement with J/psi production data from widely different experimental conditions. (C) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://***/licenses/by/4.0/). Funded by SCOAP3.

关键词： Light mesons Dynamical gluons Form factors parton distribution functions Light-front quantization

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Search for Z' Production in 4b-Tagged Jet Final States in Proton-Proton Collisions

Search for Z' Production in 4b-Tagged Jet Final States in Pr...

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作者： Delgado, Andrea Texas A&M University

学位级别：Ph.D., Doctor of Philosophy

The LHCb experiment has reported discrepancies at a level of 3 sigma in the ratio in which B mesons decay to muons and electrons. Some theories attempt to explain these anomalies by theorizing the existence of new particles beyond the standard model, such as a new heavy neutrl gauge boson (Z′ ) coupling mostly to third-generation fermions, specifically b-quarks. This study performs a search for Z′ boson at the LHC with the CMS experiment. The main production channel is b-quark fusion, and since the b-quark parton distribution functions (PDFs) are at least ten times lower when compared to the gluon PDFs, a substantial contribution of bottom quarks coming from gluon-splitting to Z ′ production is expected. In short, a study for Z′ → b¯b decays is presented. The final state consists of 4b jets, with the two extra jets coming from the initial gluon splitting. Results correspond to 35.9 f b-1 of proton-proton collision data recorded by the CMS detector at the LHC with a center-of-mass-energy of 13 TeV during 2016.

关键词： Large Hadron Collider Compact muon solenoid Jets B-tagging B-meson anomalies parton distribution functions

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Mapping parton distributions of hadrons with lattice QCD

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Progress in Particle and Nuclear Physics 2025年 144卷

作者： Huey-Wen Lin Department of Physics and Astronomy Michigan State University East Lansing MI 48824 United States of America

The strong force which binds hadrons is described by the theory of quantum chromodynamics (QCD). Determining the character and manifestations of QCD is one of the most important and challenging outstanding issues necessary for a comprehensive understanding of the structure of hadrons. Within the context of the QCD parton picture, the parton distribution functions (PDFs) have been remarkably successful in describing a wide variety of processes. However, these PDFs have generally been confined to the description of collinear partons within the hadron. New experiments and facilities provide the opportunity to additionally explore the three-dimensional structure of hadrons, which can be described by generalized parton distributions (GPDs), for example. In recent years, a breakthrough was made in calculating the Bjorken- x dependence of PDFs in lattice QCD by using large-momentum effective theory (LaMET) and other similar frameworks. The breakthrough has led to the emergence and rapid development of direct calculations of Bjorken- x -dependent structure. In this review article, we show some of the recent progress made in lattice QCD in PDFs and GPDs and discuss future challenges.

关键词： Lattice gauge theory Quantum chromodynamics parton distribution functions Generalized parton distributions Nucleons and mesons

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Longitudinal and transverse spin transfer to Λ and Λ¯ hyperons in polarized p+p collisions at s=200 GeV

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Physical Review D 2024年第1期109卷 012004-012004页

作者： M. I. Abdulhamid B. E. Aboona J. Adam L. Adamczyk J. R. Adams I. Aggarwal M. M. Aggarwal Z. Ahammed D. M. Anderson E. C. Aschenauer S. Aslam J. Atchison V. Bairathi W. Baker J. G. Ball Cap K. Barish R. Bellwied P. Bhagat A. Bhasin S. Bhatta J. Bielcik J. Bielcikova J. D. Brandenburg X. Z. Cai H. Caines M. Calderón de la Barca Sánchez D. Cebra J. Ceska I. Chakaberia P. Chaloupka B. K. Chan Z. Chang A. Chatterjee D. Chen J. Chen J. H. Chen Z. Chen J. Cheng Y. Cheng S. Choudhury W. Christie X. Chu H. J. Crawford M. Csanád G. Dale-Gau A. Das M. Daugherity I. M. Deppner A. Dhamija L. Di Carlo P. Dixit X. Dong J. L. Drachenberg E. Duckworth J. C. Dunlop J. Engelage G. Eppley S. Esumi O. Evdokimov A. Ewigleben O. Eyser R. Fatemi S. Fazio C. J. Feng Y. Feng E. Finch Y. Fisyak F. A. Flor C. Fu C. A. Gagliardi T. Galatyuk T. Gao F. Geurts N. Ghimire A. Gibson K. Gopal X. Gou D. Grosnick A. Gupta W. Guryn A. Hamed Y. Han S. Harabasz M. D. Harasty J. W. Harris H. Harrison-Smith W. He X. H. He Y. He N. Herrmann L. Holub C. Hu Q. Hu Y. Hu H. Huang H. Z. Huang S. L. Huang T. Huang X. Huang Y. Huang T. J. Humanic D. Isenhower M. Isshiki W. W. Jacobs A. Jalotra C. Jena A. Jentsch Y. Ji J. Jia C. Jin X. Ju E. G. Judd S. Kabana M. L. Kabir S. Kagamaster D. Kalinkin K. Kang D. Kapukchyan K. Kauder D. Keane M. Kelsey Y. V. Khyzhniak D. P. Kikoła B. Kimelman D. Kincses I. Kisel A. Kiselev A. G. Knospe H. S. Ko L. K. Kosarzewski L. Kramarik L. Kumar S. Kumar R. Kunnawalkam Elayavalli R. Lacey J. M. Landgraf J. Lauret A. Lebedev J. H. Lee Y. H. Leung N. Lewis C. Li W. Li X. Li Y. Li Z. Li X. Liang Y. Liang R. Licenik T. Lin M. A. Lisa C. Liu F. Liu G. Liu H. Liu L. Liu T. Liu X. Liu Y. Liu Z. Liu T. Ljubicic W. J. Llope O. Lomicky R. S. Longacre E. M. Loyd T. Lu N. S. Lukow X. F. Luo L. Ma R. Ma Y. G. Ma N. Magdy D. Mallick S. Margetis C. Markert H. S. Matis J. A. Mazer G. McNamara K. Mi S. Mioduszewski B. Mohanty M. M. Mondal I. Mooney A. Mukherjee M. I. Nagy A. S. Nain J. D. Nam M. Nasim D. Neff J. M. Nelson D. B. Nemes M. Nie G. Nigm American University in Cairo New Cairo 11835 Egypt Texas A&M University College Station Texas 77843 Czech Technical University in Prague FNSPE Prague 115 19 Czech Republic AGH University of Krakow FPACS Cracow 30-059 Poland The Ohio State University Columbus Ohio 43210 Panjab University Chandigarh 160014 India Variable Energy Cyclotron Centre Kolkata 700064 India Brookhaven National Laboratory Upton New York 11973 Indian Institute Technology Patna Bihar 801106 India Abilene Christian University Abilene Texas 79699 Instituto de Alta Investigación Universidad de Tarapacá Arica 1000000 Chile University of California Riverside California 92521 University of Houston Houston Texas 77204 University of Jammu Jammu 180001 India State University of New York Stony Brook New York 11794 Nuclear Physics Institute of the CAS Rez 250 68 Czech Republic Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 Yale University New Haven Connecticut 06520 University of California Davis California 95616 Lawrence Berkeley National Laboratory Berkeley California 94720 University of California Los Angeles California 90095 Indiana University Bloomington Indiana 47408 National Institute of Technology Durgapur Durgapur—713209 India Shandong University Qingdao Shandong 266237 Fudan University Shanghai 200433 Tsinghua University Beijing 100084 University of California Berkeley California 94720 ELTE Eötvös Loránd University Budapest H-1117 Hungary University of Illinois at Chicago Chicago Illinois 60607 University of Heidelberg Heidelberg 69120 Germany Wayne State University Detroit Michigan 48201 Indian Institute of Science Education and Research (IISER) Berhampur 760010 India Kent State University Kent Ohio 44242 Rice University Houston Texas 77251 University of Tsukuba Tsukuba Ibaraki 305-8571 Japan Lehigh University Bethlehem Pennsylvania 18015 University of Kentucky Lexington Kentucky 40506-0055 University of Calabria & INFN-Cosenza Rend

The longitudinal and transverse spin transfers to Λ (Λ¯) hyperons in polarized proton-proton collisions are expected to be sensitive to the helicity and transversity distributions, respectively, of (anti)strange quarks in the proton, and to the corresponding polarized fragmentation functions. We report improved measurements of the longitudinal spin transfer coefficient, DLL, and the transverse spin transfer coefficient, DTT, to Λ and Λ¯ in polarized proton-proton collisions at s=200 GeV by the STAR experiment at RHIC. The dataset includes longitudinally polarized proton-proton collisions with an integrated luminosity of 52 pb−1, and transversely polarized proton-proton collisions with a similar integrated luminosity. Both datasets have about twice the statistics of previous results and cover a kinematic range of |ηΛ(Λ¯)|<1.2 and transverse momentum pT,Λ(Λ¯) up to 8 GeV/c. We also report the first measurements of the hyperon spin transfer coefficients DLL and DTT as a function of the fractional jet momentum z carried by the hyperon, which can provide more direct constraints on the polarized fragmentation functions.

关键词： Fragmentation functions parton distribution functions Quantum chromodynamics Spin-dependent parton distribution functions Strong interaction

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Pion-induced polarized Drell-Yan process at Compass

Pion-induced polarized Drell-Yan process at Compass

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作者： Pešek, Michael Charles University of Prague

In this work we present the basic theoretical concepts of the description of the nucleon spin structure. The theoretical background of two processes of interest - Semi-inclusive DIS and Drell-Yan - in the terms of Transverse Momentum De- pendent parton distribution functions is presented. The COMPASS experiment and particularly its unique polarised target are described in detail. Several target related measurements are presented. The express analysis and detector efficien- cies analysis are presented as examples of important hardware related analysis. Finally two measurements of Transverse Spin Asymmetries are presented. The first measurement is the measurement of the Transverse Spin Asymmetries in J/ψ production in the Semi-inclusive DIS on polarised protons. The second mea- surement is the measurement of Transverse Spin Asymmetries in J/ψ in the π− p polarised Drell-Yan data. 1

关键词： Nucleon spin structure parton distribution functions polarized proton target polarized Drell-Yan studies J Psi meson COMPASS experiment

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On the cancellation of radiative corrections to the cross section of electron-proton scattering

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PHYSICS LETTERS B 2019年 795卷 172-176页

作者： Fadin, V. S. Gerasimov, R. E. Budker Inst Nucl Phys SB RAS Novosibirsk 630090 Russia Novosibirsk State Univ Novosibirsk 630090 Russia

The largest radiative corrections to the cross section of electron-proton scattering at high energies are associated with emission of photons, real and virtual, by electron. They contain large logarithms coming from soft and collinear photons. Cancellation of the contributions of the soft photons to virtual and real corrections is well known. Less known is the fact that the contributions of the photons collinear to scattered electrons are also canceled for the most of experiments. On the contrary, contributions of the photons collinear to initial electrons as a rule are not canceled. It is shown, however, that these contributions are canceled for the experimental set up suggested by A.A. Vorobev for measurement of proton radius. (C) 2019 The Author(s). Published by Elsevier B.V.

关键词： Radiative corrections Electron-proton scattering Quasi-real electron method parton distribution functions

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Extraction of gluon distributions from structure functions at small x in holographic QCD

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PHYSICS LETTERS B 2020年 805卷 135470-135470页

作者： Watanabe, Akira Sawada, Takahiro Huang, Mei Chinese Acad Sci Inst High Energy Phys Beijing 100049 Peoples R China Chinese Acad Sci Theoret Phys Ctr Sci Facil Beijing 100049 Peoples R China Univ Chinese Acad Sci Sch Nucl Sci & Technol Beijing 100049 Peoples R China Osaka City Univ Dept Phys Osaka 5588585 Japan

We investigate the nucleon and pion gluon distribution functions in the framework of holographic QCD, focusing on the small Bjorken x region. Based on an approximate relation, the gluon distributions are extracted from structure functions of the unpolarized deep inelastic scattering which can be calculated with a holographic QCD model, assuming the Pomeron exchange. All the adjustable parameters of the model are determined with the HERA data of the proton structure functions. We explicitly show that the extracted proton gluon distribution is consistent with results of the recent global QCD analysis. The structure functions of the pion can be computed without any additional parameter, which enables us to predict its gluon distribution also. We find that the resulting pion gluon density is smaller than the proton's, and agrees with the recent global QCD analysis result within the uncertainties.

关键词： parton distribution functions Gauge/string correspondence AdS/CFT correspondence Pomeron

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Application of the constituent quark exchange model to the parton distributions and the EMC ratios of ¹²C and ¹⁴N nuclei

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NUCLEAR PHYSICS A 2020年 1000卷 121845-121845页

作者： Hadian, A. Modarres, M. Univ Tehran Phys Dept Tehran *** Iran

The quark exchange model (QEM) is reformulated for the A = 12 and 14 systems to obtain the constituent quark distributions of C-12 and N-14 nuclei, respectively. Afterwards, the different types of the point-like parton distribution functions (PDFs), i.e., the valence quarks, the sea quarks and the gluons, are extracted from the constituent quark model (CQM), at the hadronic scale Q(0)(2) = 0.34 GeV2 to generate the constituent quark exchange model (CQEM = QEM circle plus CQM) PDFs. From the resulted PDFs, the structure functions and the European Muon Collaboration (EMC) ratios of the above-mentioned nuclei at the appropriate hadronic scale are calculated. To make our results more comparable with the available experimental data, we evolve the PDFs, by using the standard Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGALP) evolution equations, to the higher hard scales. Subsequently, the EMC ratios of C-12 and N-14 nuclei at some higher energy scales, corresponding to the scales of available data, are calculated, at the leading (LO) and the next-to-leading (NLO) orders of pQCD. By doi ng so, it is observed that the EMC ratios do not significantly depend on the hard scale Q(2), and the outcomes are consistent with the various experimental data such as HERMES, BCDMS, JLab, SLAC, NMC, and EMC. Especially, in the mid-range of Bjorken x values, the results are so desirable. Like our previous works for the He-4 and Li-6 nuclei, we again observe that at a fixed scale Q(2), the LO and the NLO EMC ratios with high precision are approximately the same. Therefore, one can conclude that at a given hard scale, the LO approximation is good enough for calculating the EMC ratios of light nuclei. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Quark exchange model parton distribution functions Constituent quark model Structure function EMC ratio DGLAP evolution equations

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