56112268
Infrared gluon and ghost propagator exponents from lattice QCD
The compatibility of the pure power law infrared solution of QCD and lattice data for the gluon and ghost propagators in Landau gauge is discussed. For the gluon propagator, the lattice data are well described by a pure power law with an infrared exponent κ∼0.53, in the Dyson–Schwinger notation. κ is measured using a technique that suppresses finite volume effects. This value is consistent with a vanishing zero momentum gluon propagator, in agreement with the Gribov–Zwanziger confinement scenario. For the ghost propagator, the lattice data seem not to follow a pure power law, at least for the range of momenta accessed in our simulation.
117914077
Force Gradient Integrators
We present initial results of the use of Force Gradient integ rators for lattice field theories. These promise to give significant performance improvements, espe cially for light fermions and large lattices. Our results show that this is indeed the case, indi cating a speed-up of more than a factor of two, which is expected to increase as the integration step size becomes smaller for larger lattices and smaller fermion masses.
15178500
Gauge fixing methods and Gribov copies effects in lattice QCD
We compare two Landau gauge fixing methods, aiming to find the global maximum of the gauge fixing functional. Moreover, a systematic effect of Gribov copies in the gluon and ghost propagators computed in Landau gauge is presented and discussed.
16286511
Infrared exponents of gluon and ghost propagators from Lattice QCD
The compatibility of the pure power law infrared solution of QCD Dyson-Schwinger equations (DSE) and lattice data for the gluon and ghost propagators in Landau gauge is discussed. For the gluon propagator, the lattice data is compatible with the DSE infrared solution with an exponent $\kappa\sim0.53$, measured using a technique that suppresses finite volume effects and allows to model these corrections to the lattice data. For the ghost propagator, the lattice data does not seem to follow the infrared DSE power law solution.
118845565
Spectral densities from the lattice
We discuss a method to extract the K\"all\'{e}n-Lehmann spectral density of a particle (be it elementary or bound state) propagator by means of 4d lattice data. We employ a linear regularization strategy, commonly known as the Tikhonov method with Morozov discrepancy principle. An important virtue over the popular maximum entropy method is the possibility to also probe unphysical spectral densities, as, for example, of a confined gluon. We apply our proposal to the SU(3) glue sector.
119119666
Shadow Hamiltonians, Poisson Brackets, and Gauge Theories
Numerical lattice gauge theory computations to generate gauge field configurations including the effects of dynamical fermions are usually carried out using algorithms that require the molecular dynamics evolution of gauge fields using symplectic integrators. Sophisticated integrators are commonly used but hard to optimize, and force-gradient integrators show promise especially for large lattice volumes. We explain that symplectic integrators lead to very efficient Monte Carlo algorithms because they exactly conserve a shadow Hamiltonian. The shadow Hamiltonian may be expanded in terms of Poisson brackets and can be used to optimize the integrators. We show how this may be done for gauge theories by extending the formulation of Hamiltonian mechanics on Lie groups to include Poisson brackets and shadows and by giving a general method for the practical computation of forces, force gradients, and Poisson brackets for gauge theories.
119203978
How the Inverse See-Saw Mechanism Can Reveal Itself Natural, Canonical and Independent of the Right-Handed Neutrino Mass
The common lore in the literature of neutrino mass generation is that the canonical see-saw mechanism beautifully offers an explanation for the tiny neutrino mass but at the cost of introducing right-handed neutrinos at a scale that is out of range for the current experiments. The inverse see-saw mechanism is an interesting alternative to the canonical one once it leads to tiny neutrino masses with the advantage of being testable at TeV scale. However, this last mechanism suffers from an issue of naturalness concerning the scale responsible for such small masses, namely, the parameter µ that is related to lepton number violation and is supposed to be at the keV scale, much lower than the electroweak one. However, no theoretical framework was built that offers an explanation for obtaining this specific scale. In this work we propose a variation of the inverse see-saw mechanism by assuming a minimal scalar and fermionic set of singlet fields, along with a Z5 Z2 symmetry, that allows a dynamical explanation for the smallness of µ, recovering the neat canonical see-saw formula and with right-handed (RH) neutrinos free to be at the electroweak scale, thus testable at LHC and current neutrino experiments. PACS: 14.60.St; 12.60.Fr.
122619113
Infrared Finite Gluon Propagator and the Structure of Chiral Symmetry Breaking
We study the chiral symmetry breaking in QeD, using an effective potential for composite operators, with infrared finite gluon propagators that have been found by numerical calculation of the Schwinger· Dyson equations as well. as in lattice simulations. The existence of a gluon propagator that is finite at k 2 =O modifies substantially the transition between the phases with and without chiral symmetry.
1436056
Critical coupling for dynamical chiral-symmetry breaking with an infrared finite gluon propagator
Abstract We compute the critical coupling constant for the dynamical chiral-symmetry breaking in a model of quantum chromodynamics, solving numerically the quark self-energy using infrared finite gluon propagators found as solutions of the Schwinger-Dyson equation for the gluon, and one gluon propagator determined in numerical lattice simulations. The gluon mass scale screens the force responsible for the chiral breaking, and the transition occurs only for a larger critical coupling constant than the one obtained with the perturbative propagator. The critical coupling shows a great sensibility to the gluon mass scale variation, as well as to the functional form of the gluon propagator.
15081043
Fixed points and vacuum energy of dynamically broken gauge theories
We show that if a gauge theory with dynamical symmetry breaking has nontrivial fixed points, they will correspond to extrema of the vacuum energy. This relationship provides a different method to determine fixed points.
209834953
Commissioning of the CMS High-Level Trigger with Cosmic Rays
The CMS High-Level Trigger (HLT) is responsible for ensuring that data samples with potentially interesting events are recorded with high efficiency and good quality. This paper gives an overview of the HLT and focuses on its commissioning using cosmic rays. The selection of triggers that were deployed is presented and the online grouping of triggered events into streams and primary datasets is discussed. Tools for online and offline data quality monitoring for the HLT are described, and the operational performance of the muon HLT algorithms is reviewed. The average time taken for the HLT selection and its dependence on detector and operating conditions are presented. The HLT performed reliably and helped provide a large dataset. This dataset has proven to be invaluable for understanding the performance of the trigger and the CMS experiment as a whole.