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Author: Aaron Scott Meyer
Publisher:
ISBN: 9780355077728
Category :
Languages : en
Pages : 154
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Book Description
The second approach uses lattice QCD to perform a first-principles computation of the nucleon axial form factor. The Highly Improved Staggered Quark (HISQ) action is employed for both valence and sea quarks. The results presented in this dissertation are computed at physical pion mass for one lattice spacing. This work presents a computation of the axial form factor at zero momentum transfer, and forms the basis for a computation of the axial form factor momentum dependence with an extrapolation to the continuum limit and a full systematic error budget.
Author: Aaron Scott Meyer
Publisher:
ISBN: 9780355077728
Category :
Languages : en
Pages : 154
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Book Description
The second approach uses lattice QCD to perform a first-principles computation of the nucleon axial form factor. The Highly Improved Staggered Quark (HISQ) action is employed for both valence and sea quarks. The results presented in this dissertation are computed at physical pion mass for one lattice spacing. This work presents a computation of the axial form factor at zero momentum transfer, and forms the basis for a computation of the axial form factor momentum dependence with an extrapolation to the continuum limit and a full systematic error budget.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice QCD calculations can help control theory errors by providing first-principles information on nucleon form factors. In these proceedings, we present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered baryons with 2+1+1 flavors of sea quarks. Calculations are done using physical light quark masses and are absolutely normalized. We discuss fitting form factor data with the model-independent $z$ expansion parametrization.
Author: Thomas Wurm
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Jiayu Hua
Publisher:
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Category :
Languages : en
Pages :
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Author: Tobias Schulz
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The nucleon axial charge is calculated as a function of the pion mass in full QCD. Using domain wall valence quarks and improved staggered sea quarks, we present the first calculation with pion masses as light as 354 MeV and volumes as large as (3.5 fm)3. We show that finite volume effects are small for our volumes and that a constrained fit based on finite volume chiral perturbation theory agrees with experiment within 5% statistical errors.
Author: Sergey Nikolaevich Syritsyn
Publisher:
ISBN:
Category :
Languages : en
Pages : 195
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Book Description
In this work, we calculate various nucleon structure observables using the fundamental theory of quarks and gluons, QCD, simulated on a lattice. In our simulations, we use the full QCD action including Nf = 2+ 1 dynamical quarks in the SU(2) isospin limit. We compute the nucleon vector and axial vector form factors as well as the generalized form factors, and analyze the nucleon charge, magnetization, and axial radii, anomalous magnetic moment, and axial charge. In addition, we compute quark contributions to the nucleon momentum and spin. Our calculation is novel for three reasons. It is a first full QCD calculation using both sea and valence chiral quarks with pion masses as low as m[pi] = 300 MeV. We develop a method to keep systematic effects in the lattice nucleon matrix elements under control, which helps us to obtain a better signal-to-noise ratio, to achieve higher precision and to test the applicability of low-energy effective theories. Finally, we compare the results from lattice QCD calculations with two different discretization methods and lattice spacings, with the rest of the calculation technique kept equal. The level of agreement between these results indicates that our calculations are not significantly affected by discretization effects.
Author: Jonathan Daniel Bratt
Publisher:
ISBN:
Category :
Languages : en
Pages : 166
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Book Description
Lattice gauge theory is a valuable tool for understanding how properties of the nucleon arise from the fundamental interactions of QCD. Numerical computations on the lattice can be used not only for first principles calculations of experimentally accessible quantities, but also for calculations of quantities that are not (yet) known from experiment. This thesis presents two lattice studies of the quark substructure of nucleons. The first study used overlaps calculated on the lattice to evaluate the goodness of trial nucleon sources. A variational study was performed to find the trial source that best approximated the true nucleon ground state. In this exploratory work with relatively simple trial sources on quenched lattices, we obtained overlaps as high as 80%. The second study was performed using domain wall valence fermions on Asqtad improved staggered lattices provided by the MILC collaboration, with pion masses as low as 290 MeV. We compute nucleon matrix elements of local quark operators: (F', S'l@P(0) F{Il Dt12 ... i D 0 (0)P, S), where F" E {y", -y"-y, -io*}. These operators are parameterized by generalized form factors, which in the infinite momentum frame can be unambiguously interpreted in terms of Fourier transforms of the transverse spatial distributions of quarks in a nucleon. By calculating the local operators at many different values of nucleon momentum, we extract a complete set of generalized form factors for the lowest two moments of the vector, axial and tensor operators. From the form factors, we compute a variety of quantities characterizing the internal structure of the nucleon. Finally, we explore chiral extrapolations of the lattice results to the physical pion mass.
Author: Anatoly Radyushkin
Publisher: World Scientific
ISBN: 9814471518
Category : Science
Languages : en
Pages : 453
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Book Description
Exclusive reactions are becoming one of the major sources of information about the deep structure of nucleons and other hadrons. The 2007 International Workshop held at Jefferson Lab in Newport News, Virginia, USA — the world's leading facility performing research on nuclear, hadronic and quark-gluon structure of matter — focused on the application of a variety of exclusive reactions at high momentum transfer, utilizing unpolarized and polarized beams and targets, to obtain information about nucleon ground-state and excited-state structure at short distances. This is a subject which is central to the programs of current accelerators and especially planned future facilities.This proceedings volume contains, in concentrated form, information about the newest developments, both theoretical and experimental, in the study of hard exclusive reactions.
Author: Finn M. Stokes
Publisher: Springer Nature
ISBN: 3030257223
Category : Science
Languages : en
Pages : 237
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Book Description
Quantum Chromodynamics (QCD) describes the interactions between elementary quarks and gluons as they compose the nucleons at the heart of atomic structure. The interactions give rise to complexity that can only be examined via numerical simulations on supercomputers. This work provides an introduction to the numerical simulations of lattice QCD and establishes new formalisms relevant to understanding the structure of nucleons and their excited states. The research opens with an examination of the non-trivial QCD vacuum and the emergence of “centre domains.” The focus then turns to establishing a novel Parity-Expanded Variational Analysis (PEVA) technique solving the important problem of isolating baryon states moving with finite momentum. This seminal work provides a foundation for future calculations of baryon properties. Implementation of the PEVA formalism discloses important systematic errors in conventional calculations and reveals the structure of nucleon excited states from the first principles of QCD for the first time.
