In the LHC operations era, analysis of the multi-petabyte ATLAS data sample by globally distributed physicists is a challenging task. To attain the required scale the ATLAS Computing Model was ...designed around the concept of Grid computing, realized in the Worldwide LHC Computing Grid (WLCG), the largest distributed computational resource existing in the sciences. The ATLAS experiment currently stores over 140 PB of data and runs about 140,000 concurrent jobs continuously at WLCG sites. During the first run of the LHC, the ATLAS Distributed Analysis (DA) service has operated stably and scaled as planned. More than 1600 users submitted jobs in 2012, with 2 million or more analysis jobs per week, peaking at about a million jobs per day. The system dynamically distributes popular data to expedite processing and maximally utilize resources. The reliability of the DA service is high and steadily improving; Grid sites are continually validated against a set of standard tests, and a dedicated team of expert shifters provides user support and communicates user problems to the sites. Both the user support techniques and the direct feedback of users have been effective in improving the success rate and user experience when utilizing the distributed computing environment. In this contribution a description of the main components, activities and achievements of ATLAS distributed analysis is given. Several future improvements being undertaken will be described.
More than one thousand physicists analyse data collected by the ATLAS experiment at the Large Hadron Collider (LHC) at CERN through 150 computing facilities around the world. Efficient distributed ...analysis requires optimal resource usage and the interplay of several factors: robust grid and software infrastructures, and system capability to adapt to different workloads. The continuous automatic validation of grid sites and the user support provided by a dedicated team of expert shifters have been proven to provide a solid distributed analysis system for ATLAS users. Typical user workflows on the grid, and their associated metrics, are discussed. Measurements of user job performance and typical requirements are also shown.
Distributed analysis in ATLAS Dewhurst, A.; Legger, F.
Journal of physics. Conference series,
12/2015, Letnik:
664, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The ATLAS experiment accumulated more than 140 PB of data during the first run of the Large Hadron Collider (LHC) at CERN. The analysis of such an amount of data is a challenging task for the ...distributed physics community. The Distributed Analysis (DA) system of the ATLAS experiment is an established and stable component of the ATLAS distributed computing operations. About half a million user jobs are running daily on DA resources, submitted by more than 1500 ATLAS physicists. The reliability of the DA system during the first run of the LHC and the following shutdown period has been high thanks to the continuous automatic validation of the distributed analysis sites and the user support provided by a dedicated team of expert shifters. During the LHC shutdown, the ATLAS computing model has undergone several changes to improve the analysis workflows, including the re-design of the production system, a new analysis data format and event model, and the development of common reduction and analysis frameworks. We report on the impact such changes have on the DA infrastructure, describe the new DA components, and include recent performance measurements.
We give a general parameterization of the
Λ
b
→
Λ
(
1520
)
γ
decay amplitude, applicable to any strange isosinglet spin-3/2 baryon, and calculate the branching fraction and helicity amplitudes. ...Large-energy form factor relations are worked out, and it is shown that the helicity-3/2 amplitudes vanish at lowest order in soft-collinear effective theory (SCET). The suppression can be tested experimentally at the LHC and elsewhere, thus providing a benchmark for SCET. We apply the results to assess the experimental reach for a possible wrong-helicity
b
→
s
γ
dipole coupling in
Λ
b
→
Λ
(
1520
)
γ
→
p
K
γ
decays. Furthermore we revisit
Λ
b
-polarization at hadron colliders and update the prediction from heavy-quark effective theory. Opportunities associated with
b
→
d
γ
afforded by high-statistics
Λ
b
samples are briefly discussed in the general context of CP and flavour violation.
At the Large Hadron Collider (LHC), the strategy for the observation of supersymmetry in the early days is mainly based on inclusive searches. Major backgrounds are constituted by mismeasured ...multi-jet events and W, Z and t quark production in association with jets. We describe recent work performed in the ATLAS Collaboration to derive these backgrounds from the first ATLAS data.
Every day hundreds of tests are run on the Worldwide LHC Computing Grid for the ATLAS, and CMS experiments in order to evaluate the performance and reliability of the different computing sites. All ...this activity is steered, controlled, and monitored by the HammerCloud testing infrastructure. Sites with failing functionality tests are auto-excluded from the ATLAS computing grid, therefore it is essential to provide a detailed and well organized web interface for the local site administrators such that they can easily spot and promptly solve site issues. Additional functionality has been developed to extract and visualize the most relevant information. The site administrators can now be pointed easily to major site issues which lead to site blacklisting as well as possible minor issues that are usually not conspicuous enough to warrant the blacklisting of a specific site, but can still cause undesired effects such as a non-negligible job failure rate. This paper summarizes the different developments and optimizations of the HammerCloud web interface and gives an overview of typical use cases.
Earlier studies in our laboratory showed that hydroxylated metabolites of polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) competitively inhibit thyroxine (T4) ...binding to transthyretin (TTR) and type I deiodinase (D1) activity. In this study, we investigated the possible inhibitory effects of hydroxylated metabolites of polyhalogenated aromatic hydrocarbons (PHAHs) on iodothyronine sulfotransferase activity. Rat liver cytosol was used as a source of sulfotransferase enzyme in an in vitro assay with 125I-labeled 3,3‘-diiodothyronine (T2) as a model substrate. Increasing amounts of hydroxylated PCBs, PCDDs, or PCDFs or extracts from incubation mixtures of PHAHs and induced liver microsomes were added as potential inhibitors of T2 sulfotransferase activity. Hydroxylated metabolites of PCBs, PCDDs, and PCDFs were found to be potent inhibitors of T2 sulfotransferase activity in vitro with IC50 values in the low micromolar range (0.2−3.8 μM). The most potent inhibitor of T2 sulfotransferase activity in our experiments was the PCB metabolite 3-hydroxy-2,3‘,4,4‘,5-pentachlorobiphenyl with an IC50 value of 0.2 μM. A hydroxyl group in the para or meta position appeared to be an important structural requirement for T2 sulfotransferase inhibition by PCB metabolites. Ortho hydroxy PCBs were much less potent, and none of the parent PHAHs was capable of inhibiting T2 sulfotransferase activity. In addition, the formation of T2 sulfotransferase-inhibiting metabolites of individual brominated diphenyl ethers and nitrofen as well as from some commercial PHAH mixtures (e.g., Bromkal, Clophen A50, and Aroclor 1254) was also demonstrated. These results indicate that hydroxylated PHAHs are potent inhibitors of thyroid hormone sulfation. Since thyroid hormone sulfation may play an important role in regulating free hormone levels in the fetus, and PCB metabolites are known to accumulate in fetal tissues after maternal exposure to PCBs, these observations may have implications for fetal thyroid hormone homeostasis and development.
The muon detectors of the experiments at the Large Hadron Collider (LHC) have to cope with unprecedentedly high neutron and gamma ray background rates. In the forward regions of the muon spectrometer ...of the ATLAS detector, for instance, counting rates of
1.7
kHz
/
cm
2
are reached at the LHC design luminosity. For high-luminosity upgrades of the LHC, up to 10 times higher background rates are expected which require replacement of the muon chambers in the critical detector regions. Tests at the CERN Gamma Irradiation Facility showed that drift-tube detectors with 15
mm diameter aluminum tubes operated with
Ar
:
CO
2
(
93
:
7
)
gas at 3
bar and a maximum drift time of about 200
ns provide efficient and high-resolution muon tracking up to the highest expected rates. For 15
mm tube diameter, space charge effects deteriorating the spatial resolution at high rates are strongly suppressed. The sense wires have to be positioned in the chamber with an accuracy of better than
50
μ
m
in order to achieve the desired spatial resolution of a chamber of
50
μ
m
up to the highest rates. We report about the design, construction and test of prototype detectors which fulfill these requirements.
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