209999944
Just how different are SU(2) and SU(3) Landau propagators in the IR regime
The infrared behavior of gluon and ghost propagators in Yang-Mills theories is of central importance for understanding quark and gluon confinement in QCD. While simulations of pure SU(3) gauge theory correspond to the physical case in the limit of infinite quark mass, the SU(2) case (i.e. pure two-color QCD) is usually employed as a simplification, in the hope that qualitative features be the same as for the SU(3) case. Here we carry out the first comparative study of lattice (Landau) propagators for these two gauge groups. Our data were especially produced with equivalent lattice parameters in order to allow a careful comparison of the two cases. We find very good agreement between SU(2) ans SU(3) propagators, showing that in the IR limit the equivalence of the two cases is quantitative. Our results seem to confirm the prediction from Schwinger-Dyson equations that the infrared exponents are independent of the gauge group SU(N_c).
118493159
Gluon screening mass at finite temperature from the Landau gauge gluon propagator in lattice QCD
We address the interpretation of the Landau gauge gluon propagator at finite temperature as a massive-type bosonic propagator. Using pure gauge SU(3) lattice simulations at a fixed lattice volume $\ensuremath{\sim}(6.5\text{ }\text{ }\mathrm{fm}{)}^{3}$, we compute the electric and magnetic form factors, extract a gluon mass from Yukawa-like fits, and study its temperature dependence. This is relevant both for the Debye screening at high temperature $T$ and for confinement at low $T$.
7542535
Exploring the infrared Landau gauge propagators using large asymmetric lattices
We report on the infrared limit of the quenched lattice Landau gauge gluon and ghost propagators computed from large asymmetric lattices. In particular, the compatibility of the pure power law infrared solutions of the Dyson-Schwinger equations with the lattice data is investigated and the exponent $\kappa$ is measured. The gluon lattice data favour $\kappa \sim 0.52$, which would imply a vanishing zero momentum gluon propagator. For the subset of lattices where the ghost propagator was computed, the data is not compatible with a pure power law. Our data also show a decreasing running coupling in the infrared region. Furthermore, positivity violation for the gluon propagator is also verified.
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.
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.
118792625
Some properties of two Nambu-Jona-Lasinio -type models with inputs from lattice QCD
IPNL, Universit´e de Lyon/Universit´e Lyon 1, CNRS/IN2P3, 4 rue E.Fermi,F-69622 Villeurbanne Cedex, FranceWe investigate the phase diagram of the so-called Polyakov–Nambu–Jona-Lasinio (PNJL) model at ﬁnite temperature and nonzero chemicalpotential. The calculations are performed in the light and strange quarksectors (u, d, s), which includes the ’t Hooft instanton induced interactionterm that breaks the axial symmetry, and the quarks are coupled to the(spatially constant) temporal background gauge ﬁeld. On one hand, a spe-cial attention is payed to the critical end point (CEP). The strength of theﬂavor-mixing interaction alters the CEP location, since when it becomesweaker the CEP moves to low temperatures and can even disappear. Onthe other hand, we also explore the connection between QCD, a nonlocalNambu–Jona-Lasinio type model and the Landau gauge gluon propaga-tor. Possible links between the quenched gluon propagator and low energyhadronic phenomenology are investigated.PACS numbers: 11.10.Wx, 11.30.Rd, 12.40.-y
18290847
Electric charge quantization and the muon anomalous magnetic moment
We investigate some proposals to solve the electric charge quantization puzzle that simultaneously explain the recent measured deviation on the muon anomalous magnetic moment. For this we assess extensions of the electro-weak standard model spanning modifications on the scalar sector only. It is interesting to verify that one can have modest extensions which easily account for the solution for both problems.
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.
26680612
Search for solar axions by the CERN axion solar telescope with 3He buffer gas: closing the hot dark matter gap.
The CERN Axion Solar Telescope has finished its search for solar axions with (3)He buffer gas, covering the search range 0.64 eV ≲ ma ≲ 1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of gaγ ≲ 3.3 × 10(-10)  GeV(-1) at 95% C.L., with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of gaγ, for example by the currently discussed next generation helioscope International AXion Observatory.
120805024
Search for First Generation Scalar Leptoquarks in pp Collisions at $\sqrt{s}=7$ TeV with the ATLAS Detector
We report a search for first generation scalar leptoquarks using 1.03 fb−1 of proton–proton collisions data produced by the Large Hadron Collider at and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generation scalar leptoquark with masses when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).
56306636
Light composite Higgs from an effective action for technicolor
We compute an effective action for a composite Higgs boson formed by new fermions belonging to a general technicolor non-Abelian gauge theory, using a quite general expression for the fermionic self-energy that depends on a certain parameter ($\ensuremath{\alpha}$), that defines the technicolor theory from the extreme walking behavior up to the one with a standard operator product expansion behavior. We discuss the values of the trilinear and quadrilinear scalar couplings. Our calculation spans all the possible physical possibilities for mass and couplings of the composite system. In the case of extreme walking technicolor theories we verify that it is possible to have a composite Higgs boson with a mass as light as the present experimental limit, contrary to the usual expectation of a heavy mass for the composite Higgs boson. In this case we obtain an upper limit for the Higgs boson mass, (${M}_{H}\ensuremath{\le}\mathcal{O}(700)\text{ }\text{ }\mathrm{GeV}$ for $SU(2{)}_{\mathrm{TC}}$), and the experimental data on the Higgs boson mass constrain $SU(N{)}_{\mathrm{TC}}$ technicolor gauge groups to be smaller than $SU(10{)}_{\mathrm{TC}}$.