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.

title: Gribov copies and gauge fixing in lattice gauge theories
abstract: We address the problem of the gauge fixing versus Gribov copies in lattice gauge theories. For the Landau gauge, results show that a suitable combination of evolutionary algorithms with traditional steepest descent methods identifies the global maximum of the optimisation function. We discuss the performance of the combined algorithm on small cubic lattices for SU(2) and SU(3).

title: Infrared gluon and ghost propagator exponents from lattice QCD
abstract: 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.

title: What does low energy physics tell us about the zero momentum gluon propagator
abstract: The connection between QCD, a nonlocal Nambu–Jona-Lasinio type model and the Landau gauge gluon propagator is explored. This two point function is parameterized by a functional form which is compatible with Dyson–Schwinger and lattice QCD results. Demanding the nonlocal model to reproduce the experimental values for the pion mass, the pion decay constant, Γ π → γ γ and the light quark condensate we conclude that low energy physics does not distinguish between the so-called decoupling and scaling solutions of the Dyson–Schwinger equations. This result means that, provided that the model parameters are chosen appropriately, one is free to choose any of the above scenarios. Furthermore, the nonlocal Nambu–Jona-Lasinio quark model considered here is chiral invariant and satisfies the GMOR relation at the 1% level of precision.

title: Gauge fixing methods and Gribov copies effects in lattice QCD
abstract: 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.

title: The gluon propagator from large asymmetric lattices
abstract: The Landau-gauge gluon propagator is computed for the SU(3) gauge theory on lattices up to a size of $32^3 \times 200$. We use the standard Wilson action at $\beta = 6.0$ and compare our results with previous computations using large asymmetric and symmetric lattices. In particular, we focus on the impact of the lattice geometry and momentum cuts to achieve compatibility between data from symmetric and asymmetric lattices for a large range of momenta.

title: Alignment of the CMS Silicon Tracker during Commissioning with Cosmic Rays
abstract: This is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 IOP

title: Infrared Finite Gluon Propagator and the Structure of Chiral Symmetry Breaking
abstract: 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.

title: 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.

title: Electroweak production of Z bosons with forward-backward jets at CMS

title: Multiplicity and transverse momentum dependence of two- and four-particle correlations in pPb and PbPb collisions
abstract: Measurements of two- and four-particle angular correlations for charged particles emitted in pPb collisions are presented over a wide range in pseudorapidity and full azimuth. The data, corresponding to an integrated luminosity of approximately 31 nb^(−1), were collected during the 2013 LHC pPb run at a nucleon–nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. The results are compared to 2.76 TeV semi-peripheral PbPb collision data, collected during the 2011 PbPb run, covering a similar range of particle multiplicities. The observed correlations are characterized by the near-side (|Δϕ|≈0) associated pair yields and the azimuthal anisotropy Fourier harmonics (v_n). The second-order (v_2) and third-order (v_3) anisotropy harmonics are extracted using the two-particle azimuthal correlation technique. A four-particle correlation method is also applied to obtain the value of v_2 and further explore the multi-particle nature of the correlations. Both associated pair yields and anisotropy harmonics are studied as a function of particle multiplicity and transverse momentum. The associated pair yields, the four-particle v_2, and the v_3 become apparent at about the same multiplicity. A remarkable similarity in the v_3 signal as a function of multiplicity is observed between the pPb and PbPb systems. Predictions based on the color glass condensate and hydrodynamic models are compared to the experimental results.