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Nucleon Structure In Lattice Qcd With Dynamical Domain Wall Fermions Quarks
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Book Synopsis Nucleon Structure in Lattice QCD with Dynamical Domain-wall Fermions Quarks by :
Download or read book Nucleon Structure in Lattice QCD with Dynamical Domain-wall Fermions Quarks written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm)3. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments x{sub u-d}/x{sub [Delta] u - [Delta] d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is about 1.6 GeV and the spatial volume is about (3.0 fm)3. Even with preliminary statistics of 25-30 gauge configurations, the ratios g{sub A}/g{sub V} and x{sub u-d}/x{sub {Delta} u - {Delta} d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d1, though yet to be renormalized, appears small in both sets.
Book Synopsis NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS. by : S. OHTA
Download or read book NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS. written by S. OHTA and published by . This book was released on 2006 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments x{sub u-d}/x{sub {Delta}u-{Delta}d} are in agreement with experiment, and show only very mild quark mass dependence. The second, RBC/UK, set of ensembles employs one strange and two degenerate (up and down) dynamical DWF quarks and Iwasaki gauge action. The strange quark mass is set at 0.04, and three up/down mass values of 0.03, 0.02 and 0.01 in lattice units are used. The lattice cutoff is a{sup -1} {approx} 1.6GeV and the spatial volume is about (3.0fm){sup 3}. Even with preliminary statistics of 25-30 gauge configurations, the ratios g{sub A}/g{sub V} and x{sub u-d}/x{sub {Delta}u-{Delta}d} are consistent with experiment and show only very mild quark mass dependence. Another structure function moment, d{sub 1}, though yet to be renormalized, appears small in both sets.
Book Synopsis Nucleon Structure from Dynamical Lattice QCD. by :
Download or read book Nucleon Structure from Dynamical Lattice QCD. written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present lattice QCD numerical calculations of hadronic structure functions and form factors from full-QCD lattices, with a chirally symmetric fermion action, domain-wall fermions, for the sea and valence quarks. The lattice spacing is about 0.12 fm with physical volume approximately (2 fm)3 for RBC 2-flavor ensembles and (3 fm)3 for RBC/UKQCD 2+1-flavor dynamical ones. The lightest sea quark mass is about 1/2 the strange quark mass for the former ensembles and 1/4 for the latter ones. Our calculations include: isovector vector- and axial-charge form factors and the first few moments of the polarized and unpolarized structure functions of the nucleon. Nonperturbative renormalization in RI/MOM scheme is applied.
Book Synopsis Nucleon Structure with Two Flavors of Dynamical Domain-wall Fermions by :
Download or read book Nucleon Structure with Two Flavors of Dynamical Domain-wall Fermions written by and published by . This book was released on 2008 with total page 14505 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a numerical lattice quantum chromodynamics calculation of isovector form factors and the first few moments of the isovector structure functions of the nucleon. The calculation employs two degenerate dynamical flavors of domain-wall fermions, resulting in good control of chiral symmetry breaking. Non-perturbative renormalization of the relevant quark currents is performed where necessary. The inverse lattice spacing, $a^{-1}$, is about 1.7 GeV. We use degenerate up and down dynamical quark masses around 1, 3/4 and 1/2 the strange quark mass. The physical volume of the lattice is about $(1.9{fm})^3$. The ratio of the isovector vector to axial charges, $g_A/g_V$, trends a bit lower than the experimental value as the quark mass is reduced toward the physical point. We calculate the momentum-transfer dependences of the isovector vector, axial, induced tensor and induced pseudoscalar form factors. The Goldberger-Treiman relation holds at low momentum transfer and yields a pion-nuc.
Book Synopsis Nucleon Axial Charge in 2+1 Flavor Dynamical Lattice QCD with Domain Wall Fermions by :
Download or read book Nucleon Axial Charge in 2+1 Flavor Dynamical Lattice QCD with Domain Wall Fermions written by and published by . This book was released on 2008 with total page 171602 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present results for the nucleon axial charge g_A at a fixed lattice spacing of 1/a=1.73(3) GeV using 2+1 flavors of domain wall fermions on size 16^3x32 and 24^3x64 lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The total length of the Monte Carlo trajectory at the lightest quark mass is 7360 units, including 900 for thermalization. We find finite volume effects are larger than the pion mass dependence at the smallest value of m_\pi (= 330 MeV) in our calculation. We also find that g_A exhibits a scaling with the single variable m_\pi L which can also be seen in previous two-flavor domain wall and Wilson fermion calculations. Using this scaling to eliminate the finite-volume effect, we obtain g_A = 1.20(6)(4) at the physical pion mass, m_\pi = 135 MeV, where the first and second errors are statistical and systematic. The observed finite-volume effects also appear in similar quenched simulations, but disappear when V>(2.4$ fm)^3. We argue this is a dynamical quark.
Book Synopsis Nucleon Structure and Hyperon Form Factors from Lattice QCD. by :
Download or read book Nucleon Structure and Hyperon Form Factors from Lattice QCD. written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point to be 1.23(5), consistant with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(26), consistent with the Adelaide-JLab Collaboration's result. The hyperon Sigma and Xi axial coupling constants are also performed for the first time in a lattice calculation, g_SigmaSigma = 0.441(14) and g_XiXi = -0.277(11).
Book Synopsis Exploration of Nucleon Structure in Lattice QCD with Chiral Quarks by : Sergey Nikolaevich Syritsyn
Download or read book Exploration of Nucleon Structure in Lattice QCD with Chiral Quarks written by Sergey Nikolaevich Syritsyn and published by . This book was released on 2010 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Explorations of the Quark Substructure of the Nucleon in Lattice QCD by : Jonathan Daniel Bratt
Download or read book Explorations of the Quark Substructure of the Nucleon in Lattice QCD written by Jonathan Daniel Bratt and published by . This book was released on 2009 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Lattice QCD Calculation of Nucleon Structure by :
Download or read book Lattice QCD Calculation of Nucleon Structure written by and published by . This book was released on 2016 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is emphasized in the 2015 NSAC Long Range Plan [1] that "understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics." Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out first-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large scale computer simulation. We started out by calculating the nucleon form factors − electromagnetic [2], axial-vector [3], ? NN [4], and scalar [5] form factors, the quark spin contribution [6] to the proton spin, the strangeness magnetic moment [7], the quark orbital angular momentum [8], the quark momentum fraction [9], and the quark and glue decomposition of the proton momentum and angular momentum [10]. These first round of calculations were done with Wilson fermions in the q̀uenched' approximation where the dynamical effects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge configurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations [11, 12]. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at ̃300 MeV and obtained the strange form factors [13], charm and strange quark masses, the charmonium spectrum and the Ds meson decay constant fDs [14], the strangeness and charmness [15], the meson mass decomposition [16] and the strange quark spin from the anomalous Ward identity [17]. Recently, we have started to include multiple lattices with different lattice spacings and different volumes including large lattices at the physical pion mass point. We are getting quite close to being able to calculate the hadron structure at the physical point and to do the continuum and large volume extrapolations which is our ultimate aim. We have now finished several projects which have included these systematic corrections. They include the leptonic decay width of the [18], the N sigma and strange sigma terms [19], and the strange quark magnetic moment [20]. Over the years, we have also studied hadron spectroscopy with lattice calculations and in phenomenology. These include Roper resonance [21, 22], pentaquark state [23], charmonium spectrum [24, 14], glueballs [25, 26, 27, 28], scalar mesons a0(1450) and (600) [29] and other scalar mesons [30], and the 1−+ meson [31]. In addition, we have employed the canonical approach to explore the first order phase transition and the critical point at finite density and finite temperature [32, 33]. We have also discovered a new parton degree of freedom − the connected sea partons, from the path-integral formulation of the hadronic tensor [34, 35] which explains the experimentally observed Gottfried sum rule violation [34]. Combining experimental result on the strange parton distribution, the CT10 global fitting results of the total u and d anti-partons and the lattice result of the ratio of the momentum fraction of the strange vs that of u or d in the disconnected insertion, we have shown that the connected sea partons can be isolated [36]. In this final technical report, we shall present a few representative highlights that have been achieved in the project.
Book Synopsis Lattice QCD at the Physical Point by : Thibaut Métivet
Download or read book Lattice QCD at the Physical Point written by Thibaut Métivet and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formalism of Quantum Chromodynamics on the lattice (or Lattice QCD) allows to perform ab-initio non-perturbative studies of strong-interaction driven processes, as it provides both a covariant regularisation of the theory of QCD and a natural framework for numerical computations. In this work, after a review of the main features of QCD and a step-by-step presentation of our discretization of QCD on a lattice, we undertake detailed studies of two problems of hadronic physics: the phenomenon of resonant scattering and the structure of the nucleon. The lattice calculations are performed with the Budapest-Marseille-Wuppertal Collaboration's 2+1-flavour gauge configurations, which give access to a wide range of lattice spacings, volumes and quarks masses, thereby allowing to study the sensibility of our results on these parameters, and to perform a complete continuum extrapolation. These configurations include dynamical quarks, and use a clover-improved Wilson QCD action. To investigate the scattering of particles on the lattice, we set up a Lüscher analysis for the emblematic case of pion-pion scattering in the channel of the rho meson resonance. We analyse our data with a variational generalized eigenvalue method, and give an in-depth calculation of the scattering phase-shifts and the corresponding resonance parameters, with a full control of the systematic errors. Our results provide an important step for lattice studies of scattering states, as they are the first to be performed at the physical pion mass, where one can see the actual decay of the rho into two pions. The obtained rho meson parameters are in good agreement with the experimental values, and consistent with a weak pion mass dependence of the coupling between the rho and two pions. As for our probe of the structure of the nucleon, we present a complete extraction of the electroweak isovector form factors, with a comprehensive study of the electric charge squared radius and of the axial charge. Our analysis also feature data at the physical pion mass, which turns out to be crucial in order to perform safe extrapolations to the physical point, as the chiral perturbation theory predicts violent variations of these quantities near the massless-quarks point. Our calculation includes source and sink projections onto the nucleon state, as well as a combined fit method between the two-point and three-point correlation functions to control the contamination of our data by excited states. Although one would need more data to perform a high-accuracy determination of the nucleon radius and axial charge at the physical point with a relevant estimation of the systematic errors, the results we obtain are in good agreement with the experiment and suggest that the excited-state effects are under control. Our analysis also highlights that gauge configurations ensembles near the physical pion mass and with large volumes must be used in order to extract accurate information about the nucleon structure from lattice calculations.
Book Synopsis A Lattice QCD Study of the Chiral Symmetry Breaking in the Domain Wall Fermion Formalism and the Nucleon Structure by : Valeria Grigoryevna Gadiyak
Download or read book A Lattice QCD Study of the Chiral Symmetry Breaking in the Domain Wall Fermion Formalism and the Nucleon Structure written by Valeria Grigoryevna Gadiyak and published by . This book was released on 2002 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Hadron Structure with Light Dynamical Quarks by :
Download or read book Hadron Structure with Light Dynamical Quarks written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Generalized parton distributions encompass a wealth of information concerning the three dimensional quark and gluon structure of the nucleon, and thus provide an ideal focus for the study of hadron structure using lattice QCD. The special limits corresponding to form factors and parton distributions are well explored experimentally, providing clear tests of lattice calculations, and the lack of experimental data for more general cases provides opportunities for genuine predictions and for guiding experiment. We present results from hybrid calculations with improved staggered (Asqtad) sea quarks and domain wall valence quarks at pion masses down to 350 MeV.
Book Synopsis Nucleon-Nucleon Scattering From Fully-Dynamical Lattice QCD. by :
Download or read book Nucleon-Nucleon Scattering From Fully-Dynamical Lattice QCD. written by and published by . This book was released on 2006 with total page 12001 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present results of the first fully-dynamical lattice QCD determination of nucleon-nucleon scattering lengths in the 1 S0 channel and 3 S1 - 3 D1 coupled channels. The calculations are performed with domain-wall valence quarks on the MILC staggered configurations with lattice spacing of b = 0.125 fm in the isospin-symmetric limit, and in the absence of electromagnetic interactions.
Book Synopsis Chiral Dynamics 2006 by : Mohammad W. Ahmed
Download or read book Chiral Dynamics 2006 written by Mohammad W. Ahmed and published by World Scientific. This book was released on 2007 with total page 477 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chiral Dynamics 2006 consists the most recent developments in the field of chiral symmetry and dynamics. Advances in theory and updates on experimental programs are presented in 20 papers in the plenary program and more than one hundred invited and contributed talks from the working groups are included in another section.
Book Synopsis THE PARITY PARTNER OF THE NUCLEON IN QUENCHED QCD WITH DOMAIN WALL FERMIONS. by :
Download or read book THE PARITY PARTNER OF THE NUCLEON IN QUENCHED QCD WITH DOMAIN WALL FERMIONS. written by and published by . This book was released on 2000 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present preliminary results for the mass spectrum of the nucleon and its low-lying excited states from quenched lattice QCD using the domain wall fermion method which preserves the chiral symmetry at finite lattice cutoff. Definite mass splitting is observed between the nucleon and its parity partner. This splitting grows with decreasing valence quark mass. They also present preliminary data regarding the first positive-parity excited state.
Book Synopsis Lattice QCD for Nuclear Physics by : Huey-Wen Lin
Download or read book Lattice QCD for Nuclear Physics written by Huey-Wen Lin and published by Springer. This book was released on 2014-11-21 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: With ever increasing computational resources and improvements in algorithms, new opportunities are emerging for lattice gauge theory to address key questions in strongly interacting systems, such as nuclear matter. Calculations today use dynamical gauge-field ensembles with degenerate light up/down quarks and the strange quark and it is possible now to consider including charm-quark degrees of freedom in the QCD vacuum. Pion masses and other sources of systematic error, such as finite-volume and discretization effects, are beginning to be quantified systematically. Altogether, an era of precision calculation has begun and many new observables will be calculated at the new computational facilities. The aim of this set of lectures is to provide graduate students with a grounding in the application of lattice gauge theory methods to strongly interacting systems and in particular to nuclear physics. A wide variety of topics are covered, including continuum field theory, lattice discretizations, hadron spectroscopy and structure, many-body systems, together with more topical lectures in nuclear physics aimed a providing a broad phenomenological background. Exercises to encourage hands-on experience with parallel computing and data analysis are included.
Book Synopsis PROCEEDINGS OF RIKEN BNL RESEARCH CENTER WORKSHOP ENTITLED - DOMAIN WALL FERMIONS AT TEN YEARS (VOLUME 84). by :
Download or read book PROCEEDINGS OF RIKEN BNL RESEARCH CENTER WORKSHOP ENTITLED - DOMAIN WALL FERMIONS AT TEN YEARS (VOLUME 84). written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The workshop was held to mark the 10th anniversary of the first numerical simulations of QCD using domain wall fermions initiated at BNL. It is very gratifying that in the intervening decade widespread use of domain wall and overlap fermions is being made. It therefore seemed appropriate at this stage for some ''communal introspection'' of the progress that has been made, hurdles that need to be overcome, and physics that can and should be done with chiral fermions. The meeting was very well attended, drawing about 60 registered participants primarily from Europe, Japan and the US. It was quite remarkable that pioneers David Kaplan, Herbert Neuberger, Rajamani Narayanan, Yigal Shamir, Sinya Aoki, and Pavlos Vranas all attended the workshop. Comparisons between domain wall and overlap formulations, with their respective advantages and limitations, were discussed at length, and a broad physics program including pion and kaon physics, the epsilon regime, nucleon structure, and topology, among others, emerged. New machines and improved algorithms have played a key role in realizing realistic dynamical fermion lattice simulations (small quark mass, large volume, and so on), so much in fact that measurements are now as costly. Consequently, ways to make the measurements more efficient were also discussed. We were very pleased to see the keen and ever growing interest in chiral fermions in our community and the significant strides our colleagues have made in bringing chiral fermions to the fore of lattice QCD calculations. Their contributions made the workshop a success, and we thank them deeply for sharing their time and ideas. Finally, we must especially acknowledge Norman Christ and Bob Mawhinney for their early and continued collaboration without which the success of domain wall fermions would not have been possible.
