Author: Massimiliano ProcuraPublisher:
ISBN:
Category :
Languages : en
Pages : 141
Book Description
Quark Mass Dependence of Nucleon Observables and Lattice QCD
Author: Massimiliano ProcuraPublisher:
ISBN:
Category :
Languages : en
Pages : 141
Book Description
Aspects of Quark Mass Dependence in Lattice QCD
Author: Lukas VarnhorstStudies in Hadron Structure Using Lattice QCD with Quark Masses that Almost Reach the Physical Point
Author: Jeremy Russell GreenPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Lattice QCD allows us to study the structure of hadrons from first-principles calculations of quantum chromodynamics. We present calculations that shed light on the behavior of quarks inside hadrons in both qualitative and quantitative ways. The first is a study of diquarks. We bind two quarks in a baryon with a static quark and compute the simultaneous two-quark density, including corrections for periodic boundary conditions. Defining a correlation function to isolate the intrinsic correlations of the diquark, we find that away from the immediate vicinity of the static quark, the diquark has a consistent shape, with much stronger correlations seen in the scalar diquark than in the axial-vector diquark. We present results at pion masses 293 and 940 MeV and discuss the dependence on the pion mass. The second set of calculations is a more quantitative study that covers a wide range of (mainly isovector) nucleon observables, including the Dirac and Pauli radii, the magnetic moment, the axial charge, and the average quark momentum fraction. Two major advances over previous calculations are the use of a near-physical pion mass, which nearly eliminates the uncertainty associated with extrapolation to the physical point, and the control over systematic errors caused by excited states, which is a significant focus of this thesis. Using pion masses as low as 149 MeV and spatial box sizes as large as 5.6 fm, we show the importance of good control over excited states for obtaining successful postdictions -- which we achieve for several quantities -- and we identify a remaining source of systematic error that is likely responsible for disagreement with experiment in the axial sector. We then use this understanding of systematics to make predictions for observables that have not been measured experimentally.
The Proceedings of the International Symposium on Nuclear Electro-Weak Spectroscopy for Symmetries in Electro-Weak Nuclear-Processes
Author: H. TokiPublisher: World Scientific
ISBN: 9789812381255
Category : Science
Languages : en
Pages : 380
Book Description
The NEWS99 international symposium discusses symmetries in electroweak processes in nuclei. Many phenomena in nuclear and particle physics are related to symmetry. It is known that we are living in a left-handed world as far as the Weak interaction is concerned, but neutrino physics suggests that a right-handed world may also be relevant. Chiral symmetry and its breaking plays an essential role in generating hadron masses. Symmetries related to flavor in the strong interaction like isospin, SU(3) and so on are known to be violated although they play a crucial role for the understanding of phenomena in nuclear and particle physics. The treatment of tiny breaking is of particular importance. Weak and electromagnetic interactions are well established at the fundamental level and can be used to probe the structure of nuclei and hadrons. A wide variety of phenomena in nuclear and particle physics were discussed in NEWS99 with an emphasis on symmetry. Topics ranged from nuclear structure to neutrino properties,,covering highly phenomenological to fundamental fields.
Strangeness and Charge Symmetry Violation in Nucleon Structure
Author: Phiala Elisabeth ShanahanPublisher: Springer
ISBN: 3319314386
Category : Science
Languages : en
Pages : 224
Book Description
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.
Lattice QCD for Nuclear Physics
Author: Huey-Wen LinPublisher: Springer
ISBN: 3319080229
Category : Science
Languages : en
Pages : 255
Book Description
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.
Exploration of Nucleon Structure in Lattice QCD with Chiral Quarks
Author: Sergey Nikolaevich SyritsynPublisher:
ISBN:
Category :
Languages : en
Pages : 195
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.
Nucleon Structure in Lattice QCD with Dynamical Domain-wall Fermions Quarks
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
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.
NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.
Author: S. OHTAPublisher:
ISBN:
Category :
Languages : en
Pages : 9
Book Description
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.
Author: