119193631
Non-perturbative analysis of the Gribov-Zwanziger action
In the non‐perturbative regime the usual gauge fixing is not sufficient due to the Gribov problem. To deal with it one can restrict the integration in the path integral to the first Gribov region by using the Gribov‐Zwanziger action. In its local form it features additional auxiliary fields which mix with the gluon at the two‐point level. We present an explicit infrared analysis of this action. We show that from the two possible scaling solutions obtained previously only one remains: It coincides exactly with the results from the Faddeev‐Popov action, i.e., the ghost propagator is infrared enhanced and the gluon propagator infrared suppressed and the corresponding power law behavior is described by only one parameter κ = 0.5953…. This corroborates the argument by Zwanziger that for functional equations it suffices to take into account the appropriate boundary conditions and no explicit restriction in the path integral measure is required.
15541387
Lower dimensional Yang-Mills theory as a laboratory to study the infrared regime
Lattice studies of the infrared regime of gauge theories are complicated by the required extensive limits, the performed gauge fixing and the demand for high statistics. Using a general power counting scheme for the infrared limit of Landau gauge SU(N) Yang-Mills theory in arbitrary dimensions we show that the infrared behavior of Greens functions is both qualitatively and quantitatively similar in two, three and four spacetime dimensions. Therefore, lower dimensional lattice simulations can serve as a simplified laboratory to analyze the presently applied approximations and to obtain first results for higher correlation functions.
118463320
Infrared analysis of Dyson-Schwinger equations taking into account the Gribov horizon in Landau gauge
The low momentum behavior of the Landau gauge Gribov-Zwanziger action is investigated using the respective Dyson-Schwinger equations. Because of the mixing of the gluon and the auxiliary fields four scenarios can be distinguished for the infrared behavior. Two of them lead to inconsistencies and can be discarded. Another one corresponds to the case where the auxiliary fields behave exactly like the Faddeev-Popov ghosts and the same scaling relation as in standard Landau gauge, {kappa}{sub A}+2{kappa}{sub c}=0, is valid. Even the parameter {kappa} is found to be the same, 0.595. The mixed propagators, which appear, are suppressed in all loops, and their anomalous infrared exponent can also be determined. A fourth case provides an even stricter scaling relation that includes also the mixed propagators, but possesses the same qualitative feature, i.e. the propagators of the Faddeev-Popov ghost and the auxiliary fields are infrared enhanced and the mixed and the gluon propagators are infrared suppressed. In this case the system of equations to obtain the parameter {kappa} is nonlinear in all variables.
124472128
Infrared behavior of vertex functions in d-dimensional Yang-Mills theory
119208185
Going beyond the propagators of Landau gauge Yang-Mills theory
We present results for the propagators and the ghost-gluon vertex of Landau gauge Yang-Mills theory obtained from Dyson-Schwinger equations. Solving these three quantities simultaneously constitutes a new step in truncating these equations. We also introduce a new model for the three-gluon vertex that is motivated by lattice results. It features a zero crossing which is confirmed a posteriori by a Dyson-Schwinger calculation. Within our setup we can reproduce lattice data very well. We establish that also for the ghost-gluon vertex a difference between decoupling and scaling solutions is present. For the scaling solution we discuss the possibility of modifying the infrared exponents via an angle dependence of the ghost-gluon vertex. However, no such dependence is found in our calculations. Finally, we calculate the Schwinger function for the gluon propagator.
7904061
Confinement and Green functions in Landau-gauge QCD
Institut fur Physik, Karl-Franzens-Universitat, Universitatsplatz 5, A-8010 Graz, AustriaIn a functionalapproachto QCD the infraredbehaviourof LandaugaugeGreenfunctionsis inves-tigated. Positivity violation for, and thus conﬁnement of, gluons is demonstrated, and the analyticstructure of the gluon propagator is studied. Quark conﬁnem ent is related to an infrared diver-gence of the quark-gluon vertex. In the latter various components are dynamically induced dueto the spontaneous breaking of chiral symmetry. As a result an infrared ﬁnite running coupling inthe Yang-Mills sector is derived whereas the running coupling related to the quark-gluonvertex isinfrared divergent. Based on a truncation for the quark-gluon vertex Dyson-Schwinger equation,which respects the analytically determined infrared behavior, numerical results for the coupledsystem of the quark propagator and vertex Dyson-Schwinger equations are presented. The result-ing quark mass function as well as the vertex function show only a very weak dependence on thecurrent quark mass in the deep infrared. From this we infer by an analysis of the quark-quarkscattering kernel a linearly rising quark potential with an almost mass independent string tensionin the case of broken chiral symmetry.8th Conference Quark Conﬁnement and the Hadron SpectrumSeptember 1-6, 2008Mainz, Germany
121825292
The Cryogenic Dark Matter Search (CDMS) : Present Status and Future
The CDMS collaboration utilizes Ge detectors for their Weakly Interacting Massive Particle (WIMP) search at the Soudan mine, Minnesota. The final data run of CDMS II is complete and a detector upgrade for SuperCDMS has commenced. A SuperTower of five 1‐inch thick Ge crystals has been installed and undergoing commissioning. Its surface‐event rejection capability should allow SuperCDMS to continue to run background free for the next proposed phases: 15 kg Ge deployment at Soudan, and up to 150 kg Ge deployment at SNOLAB. Recent detector advances to allow a 1 tonne Ge experiment are also discussed.
9879642
Results from a low-energy analysis of the CDMS II germanium data.
We report results from a reanalysis of data from the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory. Data taken between October 2006 and September 2008 using eight germanium detectors are reanalyzed with a lowered, 2 keV recoil-energy threshold, to give increased sensitivity to interactions from weakly interacting massive particles (WIMPs) with masses below ∼10  GeV/c(2). This analysis provides stronger constraints than previous CDMS II results for WIMP masses below 9  GeV/c(2) and excludes parameter space associated with possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments.
15665437
Testing LMC Microlensing Scenarios: The Discrimination Power of the SuperMACHO Microlensing Survey
Characterizing the nature and spatial distribution of the lensing objects that produce the previously measured microlensing optical depth toward the Large Magellanic Cloud (LMC) remains an open problem. We present an appraisal of the ability of the SuperMACHO Project, a next-generation microlensing survey directed toward the LMC, to discriminate between various proposed lensing populations. We consider two scenarios: lensing by a uniform foreground screen of objects and self-lensing by LMC stars. The optical depth for screen lensing is essentially constant across the face of the LMC, whereas the optical depth for self-lensing shows a strong spatial dependence. We have carried out extensive simulations, based on data obtained during the first year of the project, to assess the SuperMACHO survey's ability to discriminate between these two scenarios. In our simulations we predict the expected number of observed microlensing events for various LMC models for each of our fields by adding artificial stars to the images and estimating the spatial and temporal efficiency of detecting microlensing events using Monte Carlo methods. We find that the event rate itself shows significant sensitivity to the choice of the LMC luminosity function, limiting the conclusions that can be drawn from the absolute rate. If instead we determine the differential event rate across the LMC, we will decrease the impact of these systematic biases and render our conclusions more robust. With this approach the SuperMACHO Project should be able to distinguish between the two categories of lens populations. This will provide important constraints on the nature of the lensing objects and their contributions to the Galactic dark matter halo.
1767124
Search for weakly interacting massive particles with the first five-tower data from the cryogenic dark matter search at the soudan underground laboratory.
We report results from the Cryogenic Dark Matter Search at the Soudan Underground Laboratory (CDMS II) featuring the full complement of 30 detectors. A blind analysis of data taken between October 2006 and July 2007 sets an upper limit on the weakly interacting massive particle (WIMP) nucleon spin-independent cross section of 6.6x10;{-44} cm;{2} (4.6x10;{-44} cm;{2} when combined with previous CDMS II data) at the 90% confidence level for a WIMP mass of 60 GeV/c;{2}. This achieves the best sensitivity for dark matter WIMPs with masses above 44 GeV/c;{2}, and significantly restricts the parameter space for some favored supersymmetric models.
122653747
Results of the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) employs Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. CDMS data, accounting for the neutron background, give limits on the spin-independent WIMP-nucleon elastic-scattering cross section that exclude unexplored parameter space above 10 GeV c-2 WIMP mass and. at > 75% CL. the entire 3σ allowed region for the WIMP signal reported by the DAMA experiment.