HBT and Fluctuations: Recent Results

We give an overview of the latest results of HBT and fluctuations studies in heavy ion collisions presented during the Quark Matter 2001 Conference.Comment: Contribution to Quark Matter 2001 Conferenc

Kaon Interferometry: A Sensitive Probe of the QCD Equation of State?

We calculate the kaon HBT radius parameters for high energy heavy ion collisions, assuming a first order phase transition from a thermalized Quark-Gluon-Plasma to a gas of hadrons. At high transverse momenta K_T ~ 1 GeV/c direct emission from the phase boundary becomes important, the emission duration signal, i.e., the R_out/R_side ratio, and its sensitivity to T_c (and thus to the latent heat of the phase transition) are enlarged. Moreover, the QGP+hadronic rescattering transport model calculations do not yield unusual large radii (R_i<9fm). Finite momentum resolution effects have a strong impact on the extracted HBT parameters (R_i and lambda) as well as on the ratio R_out/R_side.Comment: 4 pages, 2 figure

Particle Correlations at RHIC - Scrutiny of a Puzzle

We present calculations of two-pion and two-kaon correlation functions in relativistic heavy ion collisions from a relativistic transport model that includes explicitly a first-order phase transition from a thermalized quark-gluon plasma to a hadron gas. We compare the obtained correlation radii with recent data from RHIC. The predicted R_side radii agree with data while the R_out and R_long radii are overestimated. We also address the impact of in-medium modifications, for example, a broadening of the rho-meson, on the correlation radii. In particular, the longitudinal correlation radius R_long is reduced, improving the comparison to data.Comment: 4 pages, 3 figure

Kaon interferometry : a sensitive probe of the QCD equation of state?

We calculate the kaon HBT radius parameters for high energy heavy ion collisions, assuming a first order phase transition from a thermalized Quark-Gluon-Plasma to a gas of hadrons. At high transverse momenta K_T ~ 1 GeV/c direct emission from the phase boundary becomes important, the emission duration signal, i.e., the R_out/R_side ratio, and its sensitivity to T_c (and thus to the latent heat of the phase transition) are enlarged. Moreover, the QGP+hadronic rescattering transport model calculations do not yield unusual large radii (R_i<9fm). Finite momentum resolution effects have a strong impact on the extracted HBT parameters (R_i and lambda) as well as on the ratio R_out/R_side

High-Throughput Computing on High-Performance Platforms: A Case Study

The computing systems used by LHC experiments has historically consisted of the federation of hundreds to thousands of distributed resources, ranging from small to mid-size resource. In spite of the impressive scale of the existing distributed computing solutions, the federation of small to mid-size resources will be insufficient to meet projected future demands. This paper is a case study of how the ATLAS experiment has embraced Titan---a DOE leadership facility in conjunction with traditional distributed high- throughput computing to reach sustained production scales of approximately 52M core-hours a years. The three main contributions of this paper are: (i) a critical evaluation of design and operational considerations to support the sustained, scalable and production usage of Titan; (ii) a preliminary characterization of a next generation executor for PanDA to support new workloads and advanced execution modes; and (iii) early lessons for how current and future experimental and observational systems can be integrated with production supercomputers and other platforms in a general and extensible manner

Evaluating Streaming Strategies for Event Processing across Infrastructure Clouds

Abstract-Infrastructure clouds revolutionized the way in which we approach resource procurement by providing an easy way to lease compute and storage resources on short notice, for a short amount of time, and on a pay-as-you-go basis. This new opportunity, however, introduces new performance trade-offs. Making the right choices in leveraging different types of storage available in the cloud is particularly important for applications that depend on managing large amounts of data within and across clouds. An increasing number of such applications conform to a pattern in which data processing relies on streaming the data to a compute platform where a set of similar operations is repeatedly applied to independent chunks of data. This pattern is evident in virtual observatories such as the Ocean Observatory Initiative, in cases when new data is evaluated against existing features in geospatial computations or when experimental data is processed as a series of time events. In this paper, we propose two strategies for efficiently implementing such streaming in the cloud and evaluate them in the context of an ATLAS application processing experimental data. Our results show that choosing the right cloud configuration can improve overall application performance by as much as three times

Evaluating Streaming Strategies for Event Processing across Infrastructure Clouds

International audienceInfrastructure clouds revolutionized the way in which we approach resource procurement by providing an easy way to lease compute and storage resources on short notice, for a short amount of time, and on a pay-as-you-go basis. This new opportunity, however, introduces new performance trade-offs. Making the right choices in leveraging different types of storage available in the cloud is particularly important for applications that depend on managing large amounts of data within and across clouds. An increasing number of such applications conformto a pattern in which data processing relies on streaming the data to a compute platform where a set of similar operations is repeatedly applied to independent chunks of data. This pattern is evident in virtual observatories such as the Ocean Observatory Initiative, in cases when new data is evaluated against existing features in geospatial computations or when experimental data is processed as a series of time events. In this paper, we propose two strategies for efficiently implementing such streaming in the cloud and evaluate them in the contextof an ATLAS application processing experimental data. Our results show that choosing the right cloud configuration can improve overall application performance by as much as three times

(Strange) Meson Interferometry at RHIC

We make predictions for the kaon interferometry measurements in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). A first order phase transition from a thermalized Quark-Gluon-Plasma (QGP) to a gas of hadrons is assumed for the transport calculations. The fraction of kaons that are directly emitted from the phase boundary is considerably enhanced at large transverse momenta K_T ~ 1 GeV/c. In this kinematic region, the sensitivity of the R_out/R_side ratio to the QGP-properties is enlarged. Here, the results of the 1-dimensional correlation analysis are presented. The extracted interferometry radii, depending on $K_T$, are not unusually large and are strongly affected by momentum resolution effects.Comment: 8 pages, 6 figure

Deuterons and space-momentum correlations in high energy nuclear collisions

Using a microscopic transport model together with a coalescence after-burner, we study the formation of deuterons in Au + Au central collisions at s = 200 AGeV . It is found that the deuteron transverse momentum distributions are strongly a ected by the nucleon space-momentum correlations, at the moment of freeze-out, which are mostly determined by the number of rescatterings. This feature is useful for studying collision dynamics at ultrarelativistic energies