121889238
Antiproton-proton annihilation at rest into two mesons
Abstract Branching ratios for antiproton-proton annihilations at rest into two mesons are given. The data were obtained at LEAR by stopping antiprotons in a liquid hydrogen target. Both charged and neutral annihilation products were detected in the Crystal Barrel detector. Representative data are presented, and their bearing on the general picture of annihilation dynamics is discussed. In addition, preliminary branching ratios for two-body radiative annihilations are given.
109382492
Integration of virtualized worker nodes in standard batch systems
Current experiments in HEP only use a limited number of operating system flavours. Their software might only be validated on one single OS platform. Resource providers might have other operating systems of choice for the installation of the batch infrastructure. This is especially the case if a cluster is shared with other communities, or communities that have stricter security requirements. One solution would be to statically divide the cluster into separated sub-clusters. In such a scenario, no opportunistic distribution of the load can be achieved, resulting in a poor overall utilization efficiency. Another approach is to make the batch system aware of virtualization, and to provide each community with its favoured operating system in a virtual machine. Here, the scheduler has full flexibility, resulting in a better overall efficiency of the resources. In our contribution, we present a lightweight concept for the integration of virtual worker nodes into standard batch systems. The virtual machines are started on the worker nodes just before jobs are executed there. No meta-scheduling is introduced. We demonstrate two prototype implementations, one based on the Sun Grid Engine (SGE), the other using Maui/Torque as a batch system. Both solutions support local job as well as Grid job submission. The hypervisors currently used are Xen and KVM, a port to another system is easily envisageable. To better handle different virtual machines on the physical host, the management solution VmImageManager is developed. We will present first experience from running the two prototype implementations. In a last part, we will show the potential future use of this lightweight concept when integrated into high-level (i.e. Grid) work-flows.
12991826
A comparison between the performance of feed forward neural networks and the supervised growing neural gas algorithm
Abstract The Supervised Growing Neural Gas algorithm (SGNG) provides an interesting alternative to standard Multi-Layer Perceptrons (MLP). A comparison is drawn between the performance of SGNG and MLP in the domain of function mapping. A further field of interest is classification power, which has been investigated with real data taken by PS197 at CERN. The characteristics of the two network models will be discussed from a practical point of view as well as their advantages and disadvantages.
1655743
A distributed, Grid-based analysis system for the MAGIC telescope
The observation of high-energetic γ-rays with ground based air cerenkov telescopes is one of the most exciting areas in modern astro particle physics giving insight into active galactic nuclei (AGN), pulsars, supernova remnants, unidentified EGRET sources, γ-ray bursts and cosmology. The MAGIC telescope started operation at the end of 2003. The low energy threshold for γ-rays together with different background sources leads to a considerable amount of data. The data analysis will be done in different institutes spread across Europe. The production of Monte Carlo events including the simulation of Cerenkov light in the atmosphere is very computing intensive and another challenge for a collaboration like MAGIC. The current Grid technology widely deployed over 80 sites by LCG has recently proven to be mature and well adapted to set up a distributed computational and data intensive analysis system meeting the requirements of experiments like MAGIC. The basic architecture of such a distributed, Europe wide Grid system will be presented. First implementation results will be shown. This Grid might be the starting point for a wider distributed astro particle Grid in Europe.
109845469
Virtualized Batch Worker Nodes: Conception and Integration in HPC Environments
There are various use cases where one has to separate user environments from the provided machine hardware, operating system or software setup on a cluster. To achieve this, a lightweight implementation of dynamically virtualized worker nodes in common batch systems is presented. Additionally, a summary of experiences and performance measurements obtained by running such a virtualized cluster, shared between nine different departments of the Karlsruhe Institute of Technology, is presented.
13325907
Application of a Neural Network and a Genetic Algorithm in the Analysis of Multi Particle Final States
The analysis of a particle physics experiment requires the correct selection of the desired multiplicity of charged (pions or kaons) and neutral (photons) particles. Due to fluctuations in hadronic and electromagnetic showers often too many photons are reconstructed by the analysis software. The combination of a feed forward neural network and a genetic algorithm is used to separate photons and fluctuations.
119595744
Rotating, Stationary, Axially Symmetric Spacetimes with Collisionless Matter
The existence of stationary solutions to the Einstein–Vlasov system which are axially symmetric and have non-zero total angular momentum is shown. This provides mathematical models for rotating, general relativistic and asymptotically flat non-vacuum spacetimes. If angular momentum is allowed to be non-zero, the system of equations to solve contains one semilinear elliptic equation which is singular on the axis of rotation. This can be handled very efficiently by recasting the equation as one for an axisymmetric unknown on $${\mathbb{R}^5}$$R5.
53967767
Existence of Axially Symmetric Static Solutions of the Einstein-Vlasov System
We prove the existence of static, asymptotically flat non-vacuum spacetimes with axial symmetry where the matter is modeled as a collisionless gas. The axially symmetric solutions of the resulting Einstein-Vlasov system are obtained via the implicit function theorem by perturbing off a suitable spherically symmetric steady state of the Vlasov-Poisson system.
7205471
Multipole Radiation in a Collisionless Gas Coupled to Electromagnetism or Scalar Gravitation
We consider the relativistic Vlasov-Maxwell and Vlasov-Nordström systems which describe large particle ensembles interacting by either electromagnetic fields or a relativistic scalar gravity model. For both systems we derive a radiation formula analogous to the Einstein quadrupole formula in general relativity.