117892720
Purpose and Physics of Event‐by‐Event Analysis
Event‐by‐event analysis is the study of event‐wise and ensemble correlation structure in the hadronic final state of heavy ion collisions. Statistical and topological techniques are applied to large event populations to reveal fluctuations and correlations deviating from a null hypothesis. Correlations can arise from initial‐state scattering, incomplete equilibration and from critical correlations developed during traversal of the QCD phase boundary. The goal of this analysis is a phenomenological description of full QCD at and above the phase boundary.
117386684
The positron-electron peak puzzle: results from APEX
I. Ahmad1, S.M. Austin2, B.B. Back1, R.R. Betts1,3, F.P. Calaprice4, K.C. Chan5, A. Chishti5, P. Chowdhury5, C. Conner3, R.W. Dunford1, J.D. Fox6, S.J. Freedman1,7, M. Freer1,8, S.B. Gazes 9,10, A.L. Hallin 11, T. Happ1,12, D. Henderson1, N.I. Kaloskamis5,13,?, E. Kashy2, W. Kutschera1, J. Last1, C.J. Lister1,5, M. Liu 11, M.R. Maier, D.J. Mercer2, D. Mikolas2, P.A.A. Perera10, M.D. Rhein1,12, E. Roa6, J.P. Schiffer1,9, T.A. Trainor 14, P. Wilt1, J.S. Winfield2, M. Wolanski1,9, F.L.H. Wolfs10, A.H. Wuosmaa1, A. Young4, J.E. Yurkon2
119277342
THE AZIMUTH STRUCTURE OF NUCLEAR COLLISIONS — I
We describe azimuth structure commonly associated with elliptic and directed flow in the context of 2D angular autocorrelations for the purpose of precise separation of so-called nonflow (mainly minijets) from flow. We extend the Fourier-transform description of azimuth structure to include power spectra and autocorrelations related by the Wiener–Khintchine theorem. We analyze several examples of conventional flow analysis in that context and question the relevance of reaction plane estimation to flow analysis. We introduce the 2D angular autocorrelation with examples from data analysis and describe a simulation exercise which demonstrates precise separation of flow and nonflow using the 2D autocorrelation method. We show that an alternative correlation measure based on Pearson's normalized covariance provides a more intuitive measure of azimuth structure.
33152244
First capture of antiprotons in a Penning trap: A kiloelectronvolt source.
Antiprotons from the Low Energy Antiproton Ring of CERN are slowed from 21 MeV to below 3 keV by being passed through 3 mm of material, mostly Be. While still in flight, the kiloelectronvolt antiprotons are captured in a Penning trap created by the sudden application of a 3-kV potential. Antiprotons are held for 100 s and more. Prospects are now excellent for much longer trapping times under better vacuum conditions. This demonstrates the feasibility of a greatly improved measurement of the inertial mass of the antiproton and opens the way to other intriguing experiments.
14037638
Event-by-Event Physics at the CERN SPS
Event-by-event physics in nuclear collisions has been an active field of research for more than a decade. Jet production in p-p and e-e collisions and flow in heavy-ion collisions have been extensively studied at LEP, CSPS, TEVATRON, BEVALAC and AGS among other facilities. Jets and flow are large-amplitude and/or large-scale effects which are detectable despite the rather small particle multiplicities per event from these collision systems. Multiplicities have been limited by small system size (p-p, e-e) or low energy densities (heavy ions). Both jet and flow phenomena are manifestations of symmetry reduction or increased correlation with respect to a nominally thermalized system of produced particles.
118621443
The "soft ridge" -- is it initial-state geometry or modified jets?
A same-side (SS, on azimuth $\phi$) 2D peak in measured angular correlations from 200 GeV \pp collisions exhibits properties expected for jet formation. In more-central \auau collisions the SS peak becomes elongated on pseudorapidity $\eta$ and the transverse momentum $p_t$ structure is modified. In the latter case the SS 2D peak has been referred to as a "Soft Ridge", and arguments have been presented that the elongated peak represents flow phenomena ("triangular" and "higher harmonic" flows), possibly related to the initial-state \aa geometry. In this presentation I demonstrate that "higher harmonic flows" are related to SS 2D peak properties and review evidence for a jet interpretation of the SS peak for all \auau centralities.
134906969
Synchrotron-based studies of microbe-metal ion-mineral interactions
97905177
Structure and reactivity of environmental interfaces : Application of grazing angle X-ray spectroscopy and long-period X-ray standing waves
Abstract Chemical processes occurring at environmental interfaces (e.g. mineral–fluid, mineral–organic matter and mineral–biofilm interfaces) have a profound impact on the environmental fate and bioavailability of aqueous metals and other contaminant species. However, the direct analysis of molecular scale structure and properties of environmental interfaces, particularly under “high-pressure” or “wet” conditions is highly challenging. Synchrotron based X-ray scattering and spectroscopic approaches offer numerous advantages, such as the high penetrating power and molecular scale information inherent to X-ray techniques. Yet, the ability to localize information content to environmental interfaces requires challenging experimental configurations. Here, the application of grazing angle X-ray fluorescence techniques is reviewed, including the presentation of a model formalism that allows for quantitative analysis of fluorescent yield profiles and discussion of the experimental setup. Illustrative examples are discussed, particularly in the context of combining results of GI measurements with the results of other complementary interface probes such as crystal truncation rod diffraction and X-ray microprobe spectroscopic studies.
8518308
Pb(II) distributions at biofilm–metal oxide interfaces
The distribution of aqueous Pb(II) sorbed at the interface between Burkholderia cepacia biofilms and hematite (α-Fe2O3) or corundum (α-Al2O3) surfaces has been probed by using an application of the long-period x-ray standing wave technique. Attached bacteria and adsorbed organic matter may interfere with sorption processes on metal oxide surfaces by changing the characteristics of the electrical double layer at the solid–solution interface, blocking surface sites, or providing a variety of new sites for metal binding. In this work, Pb Lα fluorescence yield profiles for samples equilibrated with 10−7 to 10−3.8 M Pb(II) were measured and modeled to determine quantitatively the partitioning of Pb(II) at the biofilm–metal oxide interface. Our data show that the reactive sites on the metal oxide surfaces were not passivated by the formation of a monolayer biofilm. Instead, high-energy surface sites on the metal oxides form the dominant sink for Pb(II) at submicromolar concentrations, following the trend α-Fe2O3 (0001) > α-Al2O3 (11̄02) > α-Al2O3 (0001), despite the greater site density within the overlying biofilms. At [Pb] > 10−6 M, significant Pb uptake by the biofilms was observed.