123368629
Annihilation at rest of antiprotons and protons into neutral particles
Abstract Annihilation of antiprotons and protons at rest into neutral particles has been studied with the Crystal Barrel detector at LEAR. Annihilation frequencies are determined for final states containing π 0 , η , η ′ and ω mesons using a liquid and a room temperature, 12 bar, gaseous hydrogen target. Including annihilation frequencies for production of neutral kaons from other experiments, the identified reactions for annihilation in liquid hydrogen add up to a branching fraction of (3.56±0.28)% per annihilation compared to the frequency of (3.50±0.30)% with which we observe the all-neutral decay modes inclusively. Since the exclusive final states are normalized to the Crystal Barrel measurement of the π 0 π 0 branching ratio, the latter result is strongly supported by this present study.
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.
53706779
Spectroscopy of Light Quark Systems
Thi s article i s part of a proposal for the construction of a high intensity proto~ accelerator in Europe (EHF, Proposal for a European Hadron Facility, edited by J.F.Crawford (SIN), supported by BMFT (Germany) and INFN (Italy)). Experiments concerning the spectroscopy of light Quark systems are discussed, which can be performed wi th Kaon beams of high intensi ty and high purity at EHF. After abrief review of the status of Mesonand Baryonspectroscopy an optimized detection system is presented, and two specific experiments (Glue-Ball production with Kbeams; radiative decays of the A(1405)-resonance) are discussed in detail. A Monte-Carlo-simulation shows, that clear signals for these processes can be obtained in short measuring times. These examples demonstrate, that wi th high quali ty Kbeams new and important information on Hadron-spectroscopy can be obtained, which is important for a further understanding of Quantum-Chromo-Dynamics.
118178926
GRID SERVICES FOR THE MAGIC EXPERIMENT
Exploring signals from the outer space has become an observational science under fast expansion. On the basis of its advanced technology the MAGIC telescope is the natural building block for the first large scale ground based high energy gamma-ray observatory. The low energy threshold for gamma-rays together with different background sources leads to a considerable amount of data. The analysis will be done in different institutes spread over Europe. Therefore MAGIC offers the opportunity to use the Grid technology to setup a distributed computational and data intensive analysis system with the nowadays available technology. Benefits of Grid computing for the MAGIC telescope are presented.
123370608
Computing technology and environment for physics research
Over the past year a remarkable progress in computing technology and environment for physics research has been achieved. This article tries to summarize the contributions to the field as presented in the course of the ACAT2003 conference.
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.
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.
16238417
Gravitational collapse and the formation of black holes for the spherically symmetric Einstein-Vlasov system
We review results on the spherically symmetric, asymptotically flat Einstein-Vlasov system. We focus on a recent result where we found explicit conditions on the initial data which guarantee the formation of a black hole in the evolution. Among these data there are data such that the corresponding solutions exist globally in Schwarzschild coordinates. We put these results into a more general context, and we include arguments which show that the spacetimes we obtain satisfy the weak cosmic censorship conjecture and contain a black hole in the sense of suitable mathematical definitions of these concepts which are available in the literature.
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.