Investigation of the Second Moment of the Nucleon's G1 and G2 Structure Functions in Two-flavor Lattice QCD PDF Download

Author: QCDSF/UKQCD Collaboration (Germany)
Publisher:
ISBN:
Category :
Languages : en
Pages : 9

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Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309478561
Category : Science
Languages : en
Pages : 153

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Understanding of protons and neutrons, or "nucleons"â€"the building blocks of atomic nucleiâ€"has advanced dramatically, both theoretically and experimentally, in the past half century. A central goal of modern nuclear physics is to understand the structure of the proton and neutron directly from the dynamics of their quarks and gluons governed by the theory of their interactions, quantum chromodynamics (QCD), and how nuclear interactions between protons and neutrons emerge from these dynamics. With deeper understanding of the quark-gluon structure of matter, scientists are poised to reach a deeper picture of these building blocks, and atomic nuclei themselves, as collective many-body systems with new emergent behavior. The development of a U.S. domestic electron-ion collider (EIC) facility has the potential to answer questions that are central to completing an understanding of atoms and integral to the agenda of nuclear physics today. This study assesses the merits and significance of the science that could be addressed by an EIC, and its importance to nuclear physics in particular and to the physical sciences in general. It evaluates the significance of the science that would be enabled by the construction of an EIC, its benefits to U.S. leadership in nuclear physics, and the benefits to other fields of science of a U.S.-based EIC.

Author: Zhouyou Fan
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0

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Parton distribution functions (PDFs) are important to characterize the structure of the hadrons such as protons and neutrons. The contribution to the structure from quarks has been studied in detail during the past few decades. The structure in the gluon sector is also important but less studied. For high-energy hadrons, the gluon contribution dominates at small x, where x is the momentum fraction carried by a quark or gluon. At large x, the uncertainty of the gluon PDF is large, especially compared to that of the quark PDFs at large x. Gluon PDFs for nucleons and pions are mostly extracted from global analysis of experimental data using perturbation theory as a guide. Theoretically, lattice QCD provides an independent non-perturbative theoretical approach to calculate the gluon PDFs. We present the exploratory study of nucleon gluon PDFs from lattice QCD using the quasi-PDF approach. Using valence overlap fermions on the 2 + 1-flavor domain-wall fermion gauge ensemble, the quasi-PDF matrix elements we obtain agree with the Fourier transform of the global-fit PDF within statistical uncertainty. We further study the x-dependent nucleon and pion gluon distributions via the pseudo-PDF approach on lattice ensembles with 2 + 1 + 1 flavors of highly improved staggered quarks (HISQ) generated by the MILC Collaboration. Using clover fermions for the valence action, and adding momentum smearing, PDFs are found for pion boost momenta up to 2.56 9́8 GeV. Several lattice sizes and spacings (a 9́8 0.9, 0.12 and 0.15 9́8 fm) were evaluated, resulting in three pion masses, MÏ0 9́8 220, 310 and 690 9́8 MeV/c2.

Author:
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ISBN:
Category :
Languages : en
Pages :

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Author: Navid Nekouee
Publisher: Proquest, UMI Dissertation Publishing
ISBN: 9781249889274
Category :
Languages : en
Pages : 244

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Enjoy a wide range of dissertations and theses published from graduate schools and universities from around the world. Covering a wide range of academic topics, we are happy to increase overall global access to these works and make them available outside of traditional academic databases. These works are packaged and produced by BiblioLabs under license by ProQuest UMI. The description for these dissertations was produced by BiblioLabs and is in no way affiliated with, in connection with, or representative of the abstract meta-data associated with the dissertations published by ProQuest UMI. If you have any questions relating to this particular dissertation, you may contact BiblioLabs directly.

Author:
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Category :
Languages : en
Pages :

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We present new experimental results of the 3He spin structure function g2 in the resonance region at Q2 values between 1.2 and 3.0 (GeV/c)2. Spin dependent moments of the neutron were then extracted. Our main result, the inelastic contribution to the neutron d2 matrix element, was found to be small (Q2) = 2.4 (GeV/c)2 and in agreement with the Lattice QCD calculation. The Burkhardt-Cottingham sum rule for 3He neutron was tested with the measured data and using the Wandzura-Wilczek relation for the low x unmeasured region.

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Category :
Languages : en
Pages : 8

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Here, we present a determination of nucleon-nucleon scattering phase shifts for L>0. The S, P, D and F phase shifts for both the spin-triplet and spin-singlet channels are computed for the first time with lattice Quantum ChromoDynamics. This required the design and implementation of novel lattice methods involving displaced sources and momentum-space cubic sinks. In order to demonstrate the utility of our approach, the calculations were performed in the SU(3)-flavor limit where the light quark masses have been tuned to the physical strange quark mass, corresponding to m[pi]=mKH"00~MeV. Two spatial volumes of V H"(3.5 fm)3 and V H"(4.6 fm)3 were used. Furthermore, the finite-volume spectrum is extracted from the exponential falloff of the correlation functions. Said spectrum is mapped onto the infinite volume phase shifts using the generalization of the Luscher formalism for two-nucleon systems.

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Category :
Languages : en
Pages :

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Experimental data on the F2 structure functions of the proton and deuteron, including recent results from CLAS at Jefferson Lab, have been used to construct their n=12 moments. A comprehensive analysis of the moments in terms of the operator product expansion has been performed to separate the moments into leading and higher twist contributions. Particular attention was paid to the issue of nuclear corrections in the deuteron, when extracting the neutron moments from data. The difference between the proton and neutron moments was compared directly with lattice QCD simulations. Combining leading twist moments of the neutron and proton we found the d/u ratio at x-1 approaching 0, although the precision of the data did not allow to exclude the 1/5 value. The higher twist components of the proton and neutron moments suggest that multi-parton correlations are isospin independent.

Author: Phiala Elisabeth Shanahan
Publisher: Springer
ISBN: 3319314386
Category : Science
Languages : en
Pages : 224

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This thesis discusses two key topics: strangeness and charge symmetry violation (CSV) in the nucleon. It also provides a pedagogical introduction to chiral effective field theory tailored to the high-precision era of lattice quantum chromodynamics (QCD). Because the nucleon has zero net strangeness, strange observables give tremendous insight into the nature of the vacuum; they can only arise through quantum fluctuations in which strange–antistrange quark pairs are generated. As a result, the precise values of these quantities within QCD are important in physics arenas as diverse as precision tests of QCD, searches for physics beyond the Standard Model, and the interpretation of dark matter direct-detection experiments. Similarly, the precise knowledge of CSV observables has, with increasing experimental precision, become essential to the interpretation of many searches for physics beyond the Standard Model. In this thesis, the numerical lattice gauge theory approach to QCD is combined with the chiral perturbation theory formalism to determine strange and CSV quantities in a diverse range of observables including the octet baryon masses, sigma terms, electromagnetic form factors, and parton distribution functions. This thesis builds a comprehensive and coherent picture of the current status of understanding of strangeness and charge symmetry violation in the nucleon.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 169

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The inclusive inelastic electron scattering o the proton was measured at five different beam energies 1.5, 2.5, 4.0, 4.2 and 4.4 GeV. The data were taken, during February-March 1999, on a liquid hydrogen target with the CLAS detector installed in Hall-B of the Thomas Jefferson National Accelerator Facility (TJNAF). The obtained high statistics and high precision data appear to be in good agreement with previously measured world data and permit to integrate experimental values of F2 over x at fixed Q2 , allowing for the first time the evaluation of its experimental moments at low and moderate values of Q2 . In a combined analysis of CLAS and world data, the Q2-evolution of the experimental moments was explored in the range from 0.3 up to 100 GeV2 . This offered a unique possibility to trace changes of the proton structure function from hard DIS down to the non-perturbative regime through the transition region, which is of particular interest for the TJNAF physics program. The obtained experimental moments allowed to perform a separation between the leading twist, calculable in the framework of the perturbative QCD (pQCD), and higher twists, treated effectively. A comparison with theoretical predictions based either on lattice QCD simulations or obtained within models of the nucleon structure may represent an important test of our understanding of the nucleon structure as observed at large wavelengths.