Light Hadron Spectrum, Quark Masses and Meson Decay Constants from Lattice QCD with Wilson Fermions PDF Download
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Author: D. J. Hepburn
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Languages : en
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Author: D. J. Hepburn
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Languages : en
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Author: Derek John Hepburn
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Languages : en
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Languages : en
Pages : 24
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We calculate the B-meson decay constants fB, fBs, and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b-quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ≈ 0.11, 0.086 fm with unitary pion masses as light as M[pi] ≈ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b-quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavy-light current through O([alpha]sa). We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain fB0 = 196.2(15.7) MeV, fB+ = 195.4(15.8) MeV, fBs = 235.4(12.2) MeV, fBs/fB0 = 1.193(59), and fBs/fB+ = 1.220(82), where the errors are statistical and total systematic added in quadrature. In addition, these results are in good agreement with other published results and provide an important independent cross check of other three-flavor determinations of B-meson decay constants using staggered light quarks.
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Languages : en
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Author: Wolfgang Lucha
Publisher: World Scientific
ISBN: 9814491454
Category :
Languages : en
Pages : 388
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Quantum chromodynamics is generally accepted to be the quantum field theory which describes the strong interactions in elementary particle physics. However, the question of the mechanism responsible for the “confinement” of the color degrees of freedom of quarks and gluons into hadrons still ranks as one of the most interesting open problems in physics.This proceedings volume summarizes the state of the art in this area of research. Mathematically inclined readers will find the articles based on monopoles, vortices, and topology most interesting. Meanwhile, lattice calculations can be performed for many important physical quantities. Their results can be used as guidelines for developing models of quark confinement. These models are indispensable for theoretical physicists performing calculations with the Bethe-Salpeter equation, Dyson-Schwinger equations, effective Hamiltonians, and potential models. The cross-fertilization of all these subfields of research becomes evident from the articles in this book. A few experimental papers are also included.
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Languages : en
Pages : 29
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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.
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Languages : en
Pages : 63
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We calculate the leptonic decay constants of B_{(s)} and D_{(s)} mesons in lattice QCD using staggered light quarks and Fermilab bottom and charm quarks. We compute the heavy-light meson correlation functions on the MILC asqtad-improved staggered gauge configurations which include the effects of three light dynamical sea quarks. We simulate with several values of the light valence- and sea-quark masses (down to m̃_s/10) and at three lattice spacings (a ̃0.15, 0.12, and 0.09 fm) and extrapolate to the physical up and down quark masses and the continuum using expressions derived in heavy-light meson staggered chiral perturbation theory. We renormalize the heavy-light axial current using a mostly nonperturbative method such that only a small correction to unity must be computed in lattice perturbation theory and higher-order terms are expected to be small. We obtain f_{B+̂} = 196.9(8.9) MeV, f_{B_s} = 242.0(9.5) MeV, f_{D+̂} = 218.9(11.3) MeV, f_{D_s} = 260.1(10.8) MeV, and the SU(3) flavor-breaking ratios f_{B_s}/f_{B} = 1.229(26) and f_{D_s}/f_{D} = 1.188(25), where the numbers in parentheses are the total statistical and systematic uncertainties added in quadrature.
Author: European Twisted Mass Collaboration
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Languages : en
Pages : 20
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Author: Wolfgang Lucha
Publisher: World Scientific
ISBN: 9789810245672
Category : Science
Languages : en
Pages : 394
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Summarizes the state of the art in this area of research.
Author: D. Galletly
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Category :
Languages : en
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