X. Espinal

Design, construction, and initial performance of SciBar detector in K2K experiment

A new near detector for the K2K long baseline neutrino experiment, the SciBar, was constructed and started data taking to study neutrino interactions. In K2K, neutrino oscillation is studied by comparing the number of neutrino interactions and energy spectrum between near and far detectors. In order to study neutrino oscillations more precisely, it is necessary to improve the measurement of neutrino spectrum and interactions below 1 GeV, where the latest K2K results suggest maximum oscillation. For that purpose, SciBar is designed to be fully active with fine segmentation. We present the design and basic performance. All detector components have been working as expected. Also presented are the measurements of charged current interactions which are used in the latest K2K oscillation analysis

The LHC Tier-1 at PIC: ten years of operations

This paper summarizes ten years of operational experience of the WLCG Tier-1 computer centre at Port d’Informacio Cientifica (PIC), which serves the ATLAS, CMS and LHCb experiments. The centre, located in Barcelona (Spain), has supported all of the commissioning activities be- fore the Large Hadron Collider (LHC) produced real collisions, it has continuously adapted to the new requirements, introducing new technologies as they became available, and it has grown significantly in resources offered to the LHC experiments, while maintaining top reliability levels as compared to other centres. Additional work has been done in the last years to reduce the power costs of the Tier-1 centre, and to prepare for the next challenges that are expected to come. Some thoughts on how the current WLCG system could evolve are also presented.

Dimensioning storage and computing clusters for efficient high throughput computing

Scientific experiments are producing huge amounts of data, and the size of their datasets and total volume of data continues increasing. These data are then processed by researchers belonging to large scientific collaborations, with the Large Hadron Collider being a good example. The focal point of scientific data centers has shifted from efficiently coping with PetaByte scale storage to deliver quality data processing throughput. The dimensioning of the internal components in High Throughput Computing (HTC) data centers is of crucial importance to cope with all the activities demanded by the experiments, both the online (data acceptance) and the offline (data processing, simulation and user analysis). This requires a precise setup involving disk and tape storage services, a computing cluster and the internal networking to prevent bottlenecks, overloads and undesired slowness that lead to losses cpu cycles and batch jobs failures. In this paper we point out relevant features for running a successful data storage and processing service in an intensive HTC environment.

Experiences with http/WebDAV protocols for data access in high throughput computing

In the past, access to remote storage was considered to be at least one order of magnitude slower than local disk access. Improvement on network technologies provide the alternative of using remote disk. For those accesses one can today reach levels of throughput similar or exceeding those of local disks. Common choices as access protocols in the WLCG collaboration are RFIO, [GSI]DCAP, GRIDFTP, XROOTD and NFS. HTTP protocol shows a promising alternative as it is a simple, lightweight protocol. It also enables the use of standard technologies such as http caching or load balancing which can be used to improve service resilience and scalability or to boost performance for some use cases seen in HEP such as the hot files. WebDAV extensions allow writing data, giving it enough functionality to work as a remote access protocol. This paper will show our experiences with the WebDAV door for dCache, in terms of functionality and performance, applied to some of the HEP work flows in the LHC Tier1 at PIC.

ATLAS Distributed Computing Operations Shift Team Experience

Description of ATLAS Distributed Computing Operations Shift (ADCoS) duties and available monitoring tools along with the operational experience is presented in this paper.