Hadronic event structure, power corrections and the strong coupling at LEP

Infrared and collinear events shapes are suited to directly probe properties of hard QCD. They are traditionally used to measure the strong coupling and to test the gauge structure of QCD. Perturbative predictions exist in several variations all of which depend on the renormalisation scheme leading to large theoretical uncertainties in the determination of $alpha_s$. To overcome this dominating error more and more schemes for setting the renormalisation scale are investigated. The application of RGI perturbation theory shows an incredible small spread of $\alpha_s$ indicating a reduced uncertainty and allows a measurement of the $\beta$-function directly from mean values.Comment: 5 pages, uses moriond.sty (included). Contribution to "XXXVIIth Rencontres de Moriond, QCD and hadronic interactions", Les Arcs, France, March 2002. See http://www.delphi.uni-wuppertal.de/qcd/Talks.html#Moriond200

Tuning Monte Carlo Generators: The Perugia Tunes

We present 9 new tunes of the pT-ordered shower and underlying-event model in PYTHIA 6.4. These "Perugia" tunes update and supersede the older "S0" family. The data sets used to constrain the models include hadronic Z0 decays at LEP, Tevatron minimum-bias data at 630, 1800, and 1960 GeV, Tevatron Drell-Yan data at 1800 and 1960 GeV, and SPS min-bias data at 200, 546, and 900 GeV. In addition to the central parameter set, called "Perugia 0", we introduce a set of 8 related "Perugia Variations" that attempt to systematically explore soft, hard, parton density, and colour structure variations in the theoretical parameters. Based on these variations, a best-guess prediction of the charged track multiplicity in inelastic, nondiffractive minimum-bias events at the LHC is made. Note that these tunes can only be used with PYTHIA 6, not with PYTHIA 8. Note: this report was updated in March 2011 with a new set of variations, collectively labeled "Perugia 2011", that are optimized for matching applications and which also take into account some lessons from the early LHC data. In order not to break the original text, these are described separately in Appendix B. Note 2: a subsequent "Perugia 2012" update is described in Appendix C.Comment: 46 page

Hadron masses and power corrections to event shapes

It is widely believed that hadronisation leads to 1/Q corrections to e+e- event shapes. We show that there are further corrections, proportional to (ln Q)^A/Q with A=4C_A/beta_0~=1.6, associated with hadron masses and whose relative normalisations can be calculated from one observable to another. At today's energies these extra corrections can be of the same order of magnitude as `traditional' 1/Q corrections. They fall into two classes: universal and non-universal. The latter can be eliminated by suitable redefinitions of the observables

Stability and electronic structure of the complex K2_2PtCl6_6 structure-type hydrides

The stability and bonding of the ternary complex K$_2$PtCl$_6$ structure hydrides is discussed using first principles density functional calculations. The cohesion is dominated by ionic contributions, but ligand field effects are important, and are responsible for the 18-electron rule. Similarities to oxides are discussed in terms of the electronic structure. However, phonon calculations for Sr$_2$RuH$_6$ also show differences, particularly in the polarizability of the RuH$_6$ octahedra. Nevertheless, the yet to be made compounds Pb$_2$RuH$_6$ and Be$_2$FeH$_6$ are possible ferroelectrics. The electronic structure and magnetic properties of the decomposition product, FeBe$_2$ are reported. Implications of the results for H storage are discussed

'Appreciating' Drainage Assets in New Zealand Cities: Rain Garden Treatment and Hydraulic Performance

Despite recognising rain gardens as a best management practice (BMP) to mitigate urban stormwater runoff, there is a dearth of knowledge about their treatment and infiltration performance. It is believed that organic substrates may enhance some contaminant removal but hinder hydraulic throughput although data showing this is sparse. In order to evaluate the influence of substrate composition on bioinfiltrative system effectiveness, mesocosm-scale (180 L, 0.17 m2) laboratory rain gardens were established. Saturated (constant head) hydraulic conductivity was determined before and after the experimental treatment tests that employed stormwater collected from a neighbouring catchment to investigate contaminant removal efficiencies. The principal contaminant (Zn, Cu, Pb and nutrients) removal efficiencies were investigated for three substrates comprising various proportions of organic topsoil. All total metal concentrations in the effluent were <50% of influent concentrations, with the exception of copper in the topsoil-only system that had negligible reduction due to a high dissolved fraction. The system comprising topsoil only had the lowest saturated hydraulic conductivity of 162 mm/hr and demonstrated the poorest metal (Cu, Zn) removal efficiencies. Interestingly, the system with a combination of sand and topsoil demonstrated most promising metal removal of Cu (53%), Zn (81.2%) and Pb (89.1%) with adequate hydraulic performance (296 mm/hr) required for a stormwater infiltrative system. Overall, metal removal was greater at an effluent pH of 7.38 compared to the 6.24 pH provided in the raw stormwater. Some pH buffering was provided by the calcareous sand in two of the systems, whereas the topsoil-only system lacked such buffering potential to facilitate adequate metal removal. These data highlight the influence of organic topsoil on pH that clearly governs metal speciation and hence removal efficacy in bioinfiltrative systems. Nitrate was net exported from all the systems, especially topsoil contrary to what is believed to be easily removed

TensorFlow Estimators: Managing Simplicity vs. Flexibility in High-Level Machine Learning Frameworks

We present a framework for specifying, training, evaluating, and deploying machine learning models. Our focus is on simplifying cutting edge machine learning for practitioners in order to bring such technologies into production. Recognizing the fast evolution of the field of deep learning, we make no attempt to capture the design space of all possible model architectures in a domain- specific language (DSL) or similar configuration language. We allow users to write code to define their models, but provide abstractions that guide develop- ers to write models in ways conducive to productionization. We also provide a unifying Estimator interface, making it possible to write downstream infrastructure (e.g. distributed training, hyperparameter tuning) independent of the model implementation. We balance the competing demands for flexibility and simplicity by offering APIs at different levels of abstraction, making common model architectures available out of the box, while providing a library of utilities designed to speed up experimentation with model architectures. To make out of the box models flexible and usable across a wide range of problems, these canned Estimators are parameterized not only over traditional hyperparameters, but also using feature columns, a declarative specification describing how to interpret input data. We discuss our experience in using this framework in re- search and production environments, and show the impact on code health, maintainability, and development speed.Comment: 8 pages, Appeared at KDD 2017, August 13--17, 2017, Halifax, NS, Canad

Yang-Yang thermodynamics on an atom chip

We investigate the behavior of a weakly interacting nearly one-dimensional (1D) trapped Bose gas at finite temperature. We perform in situ measurements of spatial density profiles and show that they are very well described by a model based on exact solutions obtained using the Yang-Yang thermodynamic formalism, in a regime where other, approximate theoretical approaches fail. We use Bose-gas focusing [Shvarchuck etal., Phys. Rev. Lett. 89, 270404 (2002)] to probe the axial momentum distribution of the gas, and find good agreement with the in situ results.Comment: extended introduction and conclusions, and minor changes throughout; accepted for publication in Phys. Rev. Let

Exact Results for Kinetics of Catalytic Reactions

The kinetics of an irreversible catalytic reaction on substrate of arbitrary dimension is examined. In the limit of infinitesimal reaction rate (reaction-controlled limit), we solve the dimer-dimer surface reaction model (or voter model) exactly in arbitrary dimension $D$. The density of reactive interfaces is found to exhibit a power law decay for $D<2$ and a slow logarithmic decay in two dimensions. We discuss the relevance of these results for the monomer-monomer surface reaction model.Comment: 4 pages, RevTeX, no figure