M. Reale

Current achievements of the DELPHI ring imaging Cherenkov detector

Abstract The DELPHI experiment has already collected 2.5 million Z 0 decays with the ring imaging Cherenkov detector (RICH) operational. This detector, covering most of the solid angle, is designed to perform π K separation from 0.8 to 20 GeV/ c and K/p separation from 0.8 to 35 GeV/ c . After a brief detector description we discuss the actual operating conditions, the data monitoring and the signal treatment. The collected data from Z 0 decays and the detector response to signals from the calibration system are used to evaluate the performance of the RICH system.

Deployment of a WLCG network monitoring infrastructure based on the perfSONAR-PS technology

The WLCG infrastructure moved from a very rigid network topology, based on the MONARC model, to a more relaxed system, where data movement between regions or countries does not necessarily need to involve T1 centres. While this evolution brought obvious advantages, especially in terms of flexibility for the LHC experiments data management systems, it also opened the question of how to monitor the increasing number of possible network paths, in order to provide a global reliable network service. The perfSONAR network monitoring system has been evaluated and agreed as a proper solution to cover the WLCG network monitoring use cases: it allows WLCG to plan and execute latency and bandwidth tests between any instrumented endpoint through a central scheduling configuration, it allows archiving of the metrics in a local database, it provides a programmatic and a web based interface exposing the tests results; it also provides a graphical interface for remote management operations. In this contribution we will present our activity to deploy a perfSONAR based network monitoring infrastructure, in the scope of the WLCG Operations Coordination initiative: we will motivate the main choices we agreed in terms of configuration and management, describe the additional tools we developed to complement the standard packages and present the status of the deployment, together with the possible future evolution.

WLCG and IPv6 – the HEPiX IPv6 working group

The HEPiX (http://www.hepix.org) IPv6 Working Group has been investigating the many issues which feed into the decision on the timetable for the use of IPv6 (http://www.ietf.org/rfc/rfc2460.txt) networking protocols in High Energy Physics (HEP) Computing, in particular in the Worldwide Large Hadron Collider (LHC) Computing Grid (WLCG). RIPE NCC, the European Regional Internet Registry (RIR), ran out ofIPv4 addresses in September 2012. The North and South America RIRs are expected to run out soon. In recent months it has become more clear that some WLCG sites, including CERN, are running short of IPv4 address space, now without the possibility of applying for more. This has increased the urgency for the switch-on of dual-stack IPv4/IPv6 on all outward facing WLCG services to allow for the eventual support of IPv6-only clients. The activities of the group include the analysis and testing of the readiness for IPv6 and the performance of many required components, including the applications, middleware, management and monitoring tools essential for HEP computing. Many WLCG Tier 1/2 sites are participants in the groups distributed IPv6 testbed and the major LHC experiment collaborations are engaged in the testing. We are constructing a group web/wiki which will contain useful information on the IPv6 readiness of the various software components and a knowledge base (http://hepix-ipv6.web.cern.ch/knowledge-base). This paper describes the work done by the working group and its future plans.

The ring imaging Cherenkov detectors of DELPHI

A ring imaging Cherenkov (RICH) detector system has been built and is now in full operation within the DELPHI experiment. Large data samples of Z/sup 0/ decays are being collected with good resolution on the observed Cherenkov angles. Several studies of Z/sup 0/ decays using the RICH have already been performed on limited samples. Disturbance of the detector operation caused by shrinkage of polymeric construction materials and by migration of radiator substance is reported. These effects have been counteracted and do not endanger the quality of the data. >

Performance of the ring imaging Cherenkov detector of DELPHI

Abstract The general purpose particle detector DELPHI at the Large Electron Positron collider at CERN was built to give the complete information of each event. DELPHI uses ring imaging Cherenkov counters to provide hadron identification in most of the momentum range below 45 GeV/ c and over almost the full solid angle. Charged particles traversing gaseous and liquid fluorocarbon radiators create photons used for Cherenkov angle reconstruction. Some of the design features of the detector will be presented, with emphasis on the experience which was gained in the operation of these large systems. The hadron identification power of the ring imaging Cherenkov detector closely meets the main design values. Data processing and performance of the detector will be discussed using dimuon events collected during 1994. Pion rejection factors for kaon tagging will be shown.

Neutronic Assessment and Criticality Analysis of the In-Vessel Fuel Storage Facilities in the CDT Project

The main objective of the CDT project is to establish an engineering design of a Fast Spectrum Transmutation Experimental Facility (FASTEF) that is the pilot plant of an industrial-scale of both an Accelerator Driven System (ADS) and a Lead Fast Reactor (LFR), based on the MYRRHA reactor concept, planned to be built during the next decade. An important issue regarding the reactor design of the MYRRHA/FASTEF experiment is the in-vessel fuel storage facility for fresh fuel, as it might have an impact on the criticality of the overall system that must be analyzed and quantified. In this work, the neutronic analysis of the in-vessel fuel storage facility and its coupling with the critical core was performed, using the state of the art Monte Carlo program MCNPX 2.6.0. Using this program several parameters were analyzed, like the criticality behavior (namely the Keff), the fission power production and the radiation damage (the displacements per atom).

Identified final states in the hadronic decays of the Z

Abstract Two physics analyses performed with RICH detector identification are presented. Both refer to the hadronic decays of the Z recorded by the DELPHI experiment at LEP during the 1992 data taking. The first analysis is the measurement of the spectral composition of the hadronic events by a maximum likelihood technique using the average reconstructed Cherenkov angle. The inclusive fractions of kaons and protons as a function of momentum and related quantities such as the average multiplicities and the ξ ∗ peak position are reported. The differential production cross sections have also been measured. These quantities are compared with the JETSET predictions and with the MLLA+LPHD QCD theoretical predictions for the hadron mass spectra. The second analysis shows another way of using the RICH as an identification tool: an individual track-by-track hadronic flavour tagging is used, merging the Cherenkov information with that coming from the d E d x . In bb events selected by a lifetime tag, kaons and protons have been selected to measure for the first time the average multiplicity of kaons and protons in Z → b b events. Studying the rapidity distribution with respect to the thrust axis, the average multiplicity of kaons and protons in the decay of the B hadrons has been extracted.