58846599
DIRAC data management: consistency, integrity and coherence of data
The DIRAC Data Management System (DMS) relies on both WLCG (Worldwide LHC Computing Grid Project) Data Management services (LCG File Catalogues, Storage Resource Managers and File Transfer System (FTS)) and LHCb specific components (Bookkeeping database). The complexity of both the DMS and its interactions with numerous WLCG components as well as the instability of facilities concerned, has frequently turned into unexpected problems in data moving and/or data registration, preventing a coherent picture of datasets. Several developments in LHCb have been made in order to avoid data corruptions, missing data incoherence and inconsistences among Catalogues and physical storage both through safety measures at data management level (failover mechanism, check sums, roll back mechanism) and extensive background checks. In this paper all the tools developed for checking data integrity and consistency will be presented as well as a Storage Usage agent, whose aim is to produce an up-to-date accounting of all LHCb storage usage using the LFC mirror database. The goal of this activity is the development of a generic tool suite able to categorize, analyze and systematically cure the disparate problems affecting the DMS in order to maintain a consistent picture of the main catalogues (Bookkeeping and LFC) and the Storage Elements.
129617632
The Durham Extensive Air Shower Array
5719579
DIRAC: A Community Grid Solution
The DIRAC system was developed in order to provide a complete solution for using the distributed computing resources of the LHCb experiment at CERN for data production and analysis. It allows a concurrent use of over 10K CPUs and 10M file replicas distributed over many tens of sites. The sites can be part of a Computing Grid such as WLCG or standalone computing clusters all integrated in a single management structure. DIRAC is a generic system with the LHCb specific functionality incorporated through a number of plug-in modules. It can be easily adapted to the needs of other communities. Special attention is paid to the resilience of the DIRAC components to allow an efficient use of non-reliable resources. The DIRAC production management components provide a framework for building highly automated data production systems including data distribution and data driven workload scheduling. In this paper we give an overview of the DIRAC system architecture and design choices. We show how different components are put together to compose an integrated data processing system including all the aspects of the LHCb experiment - from the MC production and raw data reconstruction to the final user analysis.
62238242
Data stream handling in the LHCb experiment
This paper presents the event data handling in the LHCb experiment, starting from the acceptance of events by the software trigger farm to making the data available for offline reprocessing. In the data acquisition system, events accepted by the High Level Trigger farm are assembled into streams according to their type. Each stream will be written to disk as a 2 GB file for optimal storage and ease of reconstruction. Under nominal conditions about 2 such files will be produced per minute. The life cycle and state transitions of each file are managed by means of a dedicated database. These files must be copied to the tape storage and simultaneously be made available online to various calibration and monitoring tasks. Additionally, to initiate the start of the offline re-processing all file parameters must be propagated to the offline Grid data analysis system. This system has been designed for extreme robustness and reliability with redundancy in almost every component and supports various fail-over mechanisms. The software, hardware, and protocols designed for this purpose will be discussed in detail. Performance figures of data-challenges done in 2007 will be shown.
31995433
Data Handling and Transfer in the LHCb Experiment
This paper focuses on the management of raw event data files containing the electronic response to particle collisions in the LHCb detector at the LHC storage ring at CERN. The typical file life cycle is presented, starting from writing of raw event streams into files to transfer to the CERN tape storage system and to the offline GRID distributed processing infrastructure. A distributed solution centered on a dedicated database is implemented to address the raw event data management needs. The solution is integrated with the data acquisition system software chain and with the experiment control system. The software architecture and hardware configurations are explained together with the testing methods, current development status and future plans.
120919376
The Durham air shower array - III: Evaluation of the array's response to showers
Abstract A Monte Carlo investigation of the Durham air shower array is described in which the systematic biases introduced into air shower data recorded by the experiment are evaluated.
39846719
Galaxy Zoo: Bar Lengths in Nearby Disk Galaxies
We present an analysis of bar length measurements of 3150 local galaxies in a volume limited sample of low redshift (z =3), and we find that observers were able to reproduce their own bar lengths to 3% and each others' to better than 20%. We find a "color bimodality" in our disk galaxy population with bar length, i.e., longer bars inhabit redder disk galaxies and the bars themselves are redder, and that the bluest galaxies host the smallest galactic bars (< 5 kpc/h). We also find that bar and disk colors are clearly correlated, and for galaxies with small bars, the disk is, on average, redder than the bar colors, while for longer bars the bar then itself is redder, on average, than the disk. We further find that galaxies with a prominent bulge are more likely to host longer bars than those without bulges. We categorise our galaxy populations by how the bar and/or ring are connected to the spiral arms. We find that galaxies whose bars are directly connected to the spiral arms are preferentially bluer and that these galaxies host typically shorter bars. Within the scatter, we find that stronger bars are found in galaxies which host a ring (and only a ring). The bar length and width measurements used herein are made publicly available for others to use (this http URL).
119795360
A search for electron pairs at the CERN ISR
Abstract A search has been made for electron pairs of large invariant mass produced in high-energy proton collisions at the CERN ISR. Data are presented for a centre-of-mass energy (√ s ) of 52.7 GeV. All electron pair candidates are believed to be consistent with background. Upper limits are obtained for the existence of massive objects decaying into electron pairs.
121223746
Correlations between large transverse momentum π0 mesons and charged particles at the CERN ISR
Abstract A study of the charged particles emitted together with a large transverse momentum π O was made at the CERN ISR at a centre-of-mass energy s = 52.7 GeV . The π O mesons and the charged particles were observed in two detectors, each centred at θ cm = 90° and each covering a laboratory solid angle of 0.59 sr for π o 's and 1.1 sr for charged particles. The multiplicity of charged particles, observed in the same and in the opposite hemisphere as the π O , was found to be larger than the average multiplicity for inelastic interactions. Some rapidity and azimuthal correlations were observed.
16404024
Star-planet interactions
Much effort has been invested in recent years, both observationally and theoretically, to understand the interacting processes taking place in planetary systems consisting of a hot Jupiter orbiting its star within 10 stellar radii. Several independent studies have converged on the same scenario: that a short‐period planet can induce activity on the photosphere and upper atmosphere of its host star. The growing body of evidence for such magnetic star‐planet interactions includes a diverse array of photometric, spectroscopic and spectropolarimetric studies. The nature of which is modeled to be strongly affected by both the stellar and planetary magnetic fields, possibly influencing the magnetic activity of both bodies, as well as affecting irradiation and non‐thermal and dynamical processes. Tidal interactions are responsible for the circularization of the planet orbit, for the synchronization of the planet rotation with the orbital period, and may also synchronize the outer convective envelope of the star ...
123077055
Results on large transverse momentum phenomena
Preliminary results of an experiment on large transverse momentum phenomena performed at the CERN‐ISR at centre‐of‐mass energies of 52.7 and 44.8 GeV are presented. The topics studied were the inclusive reaction p+p⇒πo+ “anything”, where the πo was emitted around 90° in the centre‐of‐mass system, (πoπo) correlations, and the charged multiplicity associated with large transverse momentum πo's. In addition, results of a search for electrons and electron pairs are included.