Introduction to the Standard Model, QCD and the Lattice (original) (raw)
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Computational Aspects of Lattice QCD
2003
Monte Carlo simulations applied to the lattice formulation of quantum chromodynamics (QCD) enable a study of the theory from first principles, in a nonperturbative way. After over two decades of developments in the methodology for this study and with present-day computers in the teraflops range, lattice-QCD simulations are now able to provide quantitative predictions with errors of a few percent. This means that these simulations will soon become the main source of theoretical results for comparison with experiments in physics of the strong interactions. It is therefore an important moment for the beginning of Brazilian participation in the field.
Searching for new physics at the frontiers with lattice quantum chromodynamics
Annals of the New York Academy of Sciences, 2012
Numerical lattice-quantum chromodynamics (QCD) simulations, when combined with experimental measurements, allow the determination of fundamental parameters of the particle-physics Standard Model and enable searches for physics beyond-the-Standard Model. We present the current status of lattice-QCD weak matrix element calculations needed to obtain the elements and phase of the Cabibbo-Kobayashi-Maskawa (CKM) matrix and to test the Standard Model in the quark-flavor sector. We then discuss evidence that may hint at the presence of new physics beyond the Standard Model CKM framework. Finally, we discuss two opportunities where we expect lattice QCD to play a pivotal role in searching for, and possibly discovery of, new physics at upcoming high-intensity experiments: rare K → decays and the muon anomalous magnetic moment. The next several years may witness the discovery of new elementary particles at the Large Hadron Collider (LHC). The interplay between lattice QCD, high-energy experiments at the LHC, and high-intensity experiments will be needed to determine the underlying structure of whatever physics beyond-the-Standard Model is realized in nature.
Quantum chromodynamics on-lattice
vixra 1905.0471, 2019
This paper describes a new numerical QCD calculation method (direct minimization of QCD-QED-action) and its results for the first-generation (u,d) hadrons. Here we start with the standard color-Lagrangian LQCD=LDirac+Lgluon , model the quarks qi as parameterized gaussians, and the gluons Agi as Ritz-Galerkin-series. We minimize the Lagrangian numerically with parameters par=(par(q),{αk},par(Ag)) for first-generation hadrons (nucleons, pseudo-scalar mesons, vector mesons). The resulting parameters yield the correct masses, correct magnetic moments for the nucleons, the gluon-distribution and the quark-distribution with interesting insights into the hadron structure.
1998
These notes aim to provide a pedagogical introduction to Lattice QCD. The topics covered include the scope of LQCD calculations, lattice discretization of gauge and fermion (naive, Wilson, and staggered) actions, doubling problem, improved gauge and Dirac actions, confinement and strong coupling expansions, phase transitions in the lattice theory, lattice operators, a general discussion of statistical and systematic errors in simulations of LQCD, the analyses of the hadron spectrum, glueball masses, the strong coupling constant, and the quark masses.
Lattice QCD thermodynamics on the Grid
Computer Physics Communications, 2010
We describe how we have used simultaneously O(10 3) nodes of the EGEE Grid, accumulating ca. 300 CPU-years in 2-3 months, to determine an important property of Quantum Chromodynamics. We explain how Grid resources were exploited eciently and with ease, using userlevel overlay based on Ganga and DIANE tools above standard Grid software stack. Application-specic scheduling and resource selection based on simple but powerful heuristics allowed to improve eciency of the processing to obtain desired scientic results by a specied deadline. This is also a demonstration of combined use of supercomputers, to calculate the initial state of the QCD system, and Grids, to perform the subsequent massively distributed simulations. The QCD simulation was performed on a 16 3 × 4 lattice. Keeping the strange quark mass at its physical value, we reduced the masses of the up and down quarks until, under an increase of temperature, the system underwent a second-order phase transition to a quark-gluon plasma. Then we measured the response of this system to an increase in the quark density. We nd that the transition is smoothened rather than sharpened. If conrmed on a ner lattice, this nding makes it unlikely for ongoing experimental searches to nd a QCD critical point at small chemical potential.
Hadron Physics and Confinement Physics in Lattice QCD
AIP Conference Proceedings, 2001
We are aiming to construct Quark Hadron Physics and Confinement Physics based on QCD. Using SU(3) c lattice QCD, we are investigating the three-quark potential at T = 0 and T = 0, mass spectra of positive and negative-parity baryons in the octet and the decuplet representations of the SU(3) flavor, glueball properties at T = 0 and T = 0. We study also Confinement Physics using lattice QCD. In the maximally abelian (MA) gauge, the off-diagonal gluon amplitude is strongly suppressed, and then the off-diagonal gluon phase shows strong randomness, which leads to a large effective off-diagonal gluon mass, M off ≃ 1.2GeV. Due to the large off-diagonal gluon mass in the MA gauge, infrared QCD is abelianized like nonabelian Higgs theories. In the MA gauge, there appears a macroscopic network of the monopole world-line covering the whole system. From the monopole current, we extract the dual gluon field B µ , and examine the longitudinal magnetic screening. We obtain m B ≃ 0.5 GeV in the infrared region, which indicates the dual Higgs mechanism by monopole condensation. From infrared abelian dominance and infrared monopole condensation, low-energy QCD in the MA gauge is described with the dual Ginzburg-Landau (DGL) theory.
Towards a Determination of the Spectrum of QCD Using a Space-Time Lattice
NSTAR 2005 - Proceedings of the Workshop on the Physics of Excited Nucleons, 2006
Progress by the Lattice Hadron Physics Collaboration in determining the baryon and meson resonance spectrum of QCD using Monte Carlo methods with spacetime lattices is described. The extraction of excited-state energies necessitates the evaluation of correlation matrices of sets of operators, and the importance of extended three-quark operators to capture both the radial and orbital structures of baryons is emphasized. The use of both quark-field smearing and link-field smearing in the operators is essential for reducing the couplings of the operators to the high-frequency modes and for reducing statistical noise in the correlators. The extraction of nine energy levels in a given symmetry channel is demonstrated, and identifying the continuum spin quantum numbers of the levels is discussed. * Speaker.