178787319
Determining the Arrival Directions of Extensive Air Showers from Fast Timing Measurements
60523028
DIRAC: data production management
The LHCb Computing Model describes the dataflow for all stages in the processing of real and simulated events, and defines the role of LHCb associated Tier-1 and Tier-2 computing centers. The WLCG 'Dress Rehearsal' exercise aims to allow LHC experiments to deploy the full chain of their Computing Models, making use of all underlying WLCG services and resources, in preparation for real data taking. During this exercise simulated RAW physics data, matching the properties of eventual real data, will be uploaded from the LHCb Online storage system to Grid enabled storage. This data will then be replicated to LHCb Tier-1 centers and subsequently processed (reconstructed and stripped). The product of this processing is user analysis data that are distributed to all LHCb Tier-1 centers. DIRAC, LHCbs Workload and Data Management System, supports the implementation of the Computing Model in a data driven, real time and coordinated fashion. In this paper the LHCb Computing Model will be reviewed and the DIRAC components providing the needed functionality to support the Computing Model will be detailed. An evaluation of the preparedness for real data taking will also be given.
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.
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.
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.
121598426
High-energy muons in extensive air showers
SummaryA study has been made of the density of high-energy muons (10<Eμ<300 GeV) as a function of the distance from the axis of extensive air showers in the size range 2·105<Ne<3·106,i.e. showers produced by primary cosmic rays in a decade of energy centered on 5·1015 eV. The results for muons above 50 GeV agree with those from the Lodz-Moscow group, but those for muons above 200 GeV are a little different from the only other experimental results: those of Acharyaet al. Comparison with predictions favours a CKP-type model with a «normal» comparison. The simple scaling model with any composition does not give a good fit to the data, but no doubt modifications could be made, principally an increase in the mean transverse momentum, which would restore agreement.RiassuntoSi è effettuato uno studio della densità dei muoni (10<Eμ<300 GeV) in funzione della distanza dall’asse di sciami d’aria estesi nell’intervallo di grandezza 2·105<Ne<<3·106, cioè sciami prodotti da raggi cosmici del primario in un decadimento di energia centrato su 5 · 1015 eV. I risultati per muoni al di sopra di 50 GeV sono in accordo con quelli del gruppo di Lodz-Moscow, ma quelle per muoni al di sopra di 200 GeV sono un po’ differenti dagli unici altri risultati sperimentali: quelli di Acharyaet al. Confronti con produzioni sono a favore del modello del tipo CKP con una composizione « normale ». Il modello a variazione di scala semplice con qualsiasi composizione non dà un buon adattamento ai dati, ma, senza dubbio, modificazioni potrebbero essere fatte, principalmente un aumento nell’impulso trasversale medio, che ripristinerebbero l’accordo.
115544175
Estimated rates for electron backgrounds at LEP
123932176
Particle Production by 2.9-BeV Protons Incident on Beryllium and Platinum
60474978
The performance of a 16000 wire mini-drift MWPC system
120328133
Evidence for pomeron single-quark interactions in proton diffraction at the ISR
Abstract Measurements are presented of two exclusive diffractive reactions, pp → (Λ 0 φ 0 K + ) p and pp → (Λ 0 Λ 0 p)p , at √ s = 63 GeV . Pronounced correlations with the beam direction are observed (in the rest frame of the forward-going bracketed system) for those outgoing particles which contain the beam valence quarks. In each case there is a forward-Λ0 in correlation with a backward K+ or p, respectively. No such behavior is seen for the particles which do not contain beam valence quarks (φ 0 and Λ 0 , respectively) . Interpreted as examples of pomeron-proton scattering, these results constitute evidence that, for these final states, the pomeron interacts with a single valence quark and apparently back-scatters it. The subsequent hadronization leads to a longitudinal event structure.
122529613
A Measurement of Single Electrons, electron Pairs, and Associated Phenomena, in Proton Proton Collisions at the CERN ISR
Abstract Measurements of single-electron production in proton-proton collisions at the CERN ISR are presented for five centre-of-mass energies √s = 23.5, 30.6, 44.8, 52.7, and 62.4 GeV. The invariant cross sections for single electrons with transverse momenta of 0.60 to 4.7 GeV/c are given. Measurements of electron-positron pairs and measurements of charged hadrons produced in association with the single electrons, are also reported.