DIRAC: a community grid solution Tsaregorodtsev, A; Bargiotti, M; Brook, N ...
Journal of physics. Conference series,
07/2008, Letnik:
119, Številka:
6
Journal Article
Recenzirano
Odprti dostop
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.
We present an analysis of the existing data on charmonium hadro-production based on non-relativistic QCD (NRQCD) calculations at the next-to-leading order (NLO). All the data on J/ψ and ψ(2S) ...production in fixed-target experiments and on pp collisions at low energy are included. We find that the amount of color-octet contribution needed to describe the data is about 1/10 of that found at the Tevatron.
The p¯ stopping power in helium from 1 keV kinetic energy is evaluated. Contrary to the effect observed around and below the maximum, Obelix data indicate a p¯ stopping power higher than that for ...proton, the difference being of the order of 15±5% at ≈700 keV. The result contributes to assert the fundamental difference between p¯ stoppings in the simplest gases (He, H2) and in solid targets below some MeV.
Measurements of the kinematic distributions of
J
/
ψ
mesons produced in
p
–C,
p
–Ti and
p
–W collisions at
in the Feynman-
x
region −0.34<
x
F
<0.14 and for transverse momentum up to
p
T
=5.4 GeV/c ...are presented. The
x
F
and
p
T
dependencies of the nuclear suppression parameter,
α
, are also given. The results are based on 2.4×10
5
J
/
ψ
mesons reconstructed in both the
e
+
e
−
and
μ
+
μ
−
decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of
x
F
for the first time. The average value of
α
in the measured
x
F
region is 0.981±0.015. The data suggest that the strong nuclear suppression of
J
/
ψ
production previously observed at high
x
F
turns into an enhancement at negative
x
F
.
Barkas effect for antiproton stopping in H2 Lodi Rizzini, E; Bianconi, A; Bussa, M P ...
Physical review letters,
2002-Oct-28, 20021028, Letnik:
89, Številka:
18
Journal Article
Recenzirano
We report the stopping power of molecular hydrogen for antiprotons of kinetic energy above the maximum (approximately 100 keV) with the purpose of comparing with the proton one. Our result is ...consistent with a positive difference in antiproton-proton stopping powers above approximately 250 keV and with a maximum difference between the stopping powers of 21%+/-3% at around 600 keV.
The electromagnetic calorimeter of the HERA-B experiment Avoni, G.; Baldanza, C.; Bargiotti, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2001, Letnik:
461, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The electromagnetic calorimeter of the HERA-B experiment employs the “shashlik” technology of sampled scintillator/tungsten(lead) sandwiches readout by photomultipliers. In this paper, we present a ...general overview of the system and the present results on energy and spatial resolution. The performances of the fast electron pre-trigger system are quoted as well.
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.
A study of the angular distributions of leptons from decays of
J
/
ψ
’s produced in p-C and p-W collisions at
has been performed in the
J
/
ψ
Feynman-
x
region −0.34<
x
F
<0.14 and for
J
/
ψ
...transverse momenta up to 5.4 GeV/
c
. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3×10
5
J
/
ψ
’s reconstructed in both the
e
+
e
−
and
μ
+
μ
−
decay channels, indicate that
J
/
ψ
’s are produced polarized. The magnitude of the effect is maximal at low
p
T
. For
p
T
>1 GeV/
c
a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises.
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