120145716
The response of air shower arrays to air showers
Abstract The air shower that is measured and analysed by an air shower experiment is not, in general, an unprejudiced derivative of the data. Biases of many kinds are present in these experiments and they can significantly modify the interpretation of the results if not eliminated.
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.
119595431
A wire-spark-chamber system with on-line computers
Abstract We describe the performance of a system of wire spark chambers and 2 on-line computers (one being time-shared) used in an experiment at the Brookhaven A.G.S. to study the decay of K± mesons via the τ mode (K±→ π ± π ± π ∓).
18104149
Galaxy Zoo 2: detailed morphological classifications for 304 122 galaxies from the Sloan Digital Sky Survey
We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304 122 galaxies drawn from the Sloan Digital Sky Survey (SDSS). Morphology is a powerful probe for quantifying a galaxy's dynamical history; however, automatic classifications of morphology (either by computer analysis of images or by using other physical parameters as proxies) still have drawbacks when compared to visual inspection. The large number of images available in current surveys makes visual inspection of each galaxy impractical for individual astronomers. GZ2 uses classifications from volunteer citizen scientists to measure morphologies for all galaxies in the DR7 Legacy survey with mr > 17, in addition to deeper images from SDSS Stripe 82. While the original GZ2 project identified galaxies as early-types, late-types or mergers, GZ2 measures finer morphological features. These include bars, bulges and the shapes of edge-on disks, as well as quantifying the relative strengths of galactic bulges and spiral arms. This paper presents the full public data release for the project, including measures of accuracy and bias. The majority (≳90 per cent) of GZ2 classifications agree with those made by professional astronomers, especially for morphological T-types, strong bars and arm curvature. Both the raw and reduced data products can be obtained in electronic format at http://data.galaxyzoo.org.
120618738
Observation of high mass electron-positron pairs produced in proton-proton collisions at the CERN ISR
Abstract In an experiment performed at the CERN Intersecting Storage Rings (ISR), 11 e + e − pairs of high invariant mass value (> 2.5 GeV/c 2 ) have been observed. Of these events, 9 can be interpreted as arising from the reaction p + p → J (3.1) + anything. the cross-section for this reaction is estimated and compared with the result obtained at lower centre-of-mass energies.
14431702
Diffuse interstellar bands in z < 0.6 Ca ii absorbers
The diffuse interstellar bands (DIBs) probably arise from complex organic molecules whose strength in local galaxies correlates with neutral hydrogen column density, N(H i), and dust reddening, E(B−V). Because Ca ii absorbers in quasar (QSO) spectra are posited to have high N(H i) and significant E(B−V), they represent promising sites for the detection of DIBs at cosmological distances. Here we present the results from the first search for DIBs in nine Ca ii-selected absorbers at 0.07 < zabs < 0.55. We detect the 5780-A DIB in one line of sight at zabs= 0.1556; this is only the second QSO absorber in which a DIB has been detected. Unlike the majority of local DIB sight-lines, both QSO absorbers with detected DIBs show weak 6284-A absorption compared with the 5780-A band. This may be indicative of different physical conditions in intermediate redshift QSO absorbers compared with local galaxies. Assuming that local relations between the 5780-A DIB strength and N(H i) and E(B−V) apply in QSO absorbers, DIB detections and limits can be used to derive N(H i) and E(B−V). For the one absorber in this study with a detected DIB, we derive E(B−V) = 0.23 mag and log N(H i) ≥ 20.9, consistent with previous conclusions that Ca ii systems have high H i column densities and significant reddening. For the remaining eight Ca ii-selected absorbers with 5780-A DIB non-detections, we derive E(B−V) upper limits of 0.1–0.3 mag.
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.