Rafael Marco

Experience with the international testbed in the crossgrid project

The International Testbed of the CrossGrid Project has been in operation for the last three years, including 16 sites in 9 countries across Europe. The main achievements in installation and operation are described, and also the substantial experience gained on providing support to application and middleware developers in the project. Results are presented showing the availability of a realistic Grid framework to execute distributed interactive and parallel jobs.

Training of Neural Networks: Interactive Possibilities in a Distributed Framework

Training of Artificial Neural Networks in a Distributed Environment is considered and applied to a typical example in High Energy Physics interactive analysis. Promising results showing a reduction of the wait time from 5 hours to 5 minutes obtained in a local cluster with 64 nodes are described. Preliminary tests in a wide area network studying the impact of latency time are described; and the future work for integration in a GRID framework, that will be carried in the CrossGrid European Project, is outlined.

Study of Z Boson Production in PbPb Collisions at √sNN=2.76 TeV

A search for Z bosons in the μ+μ− decay channel has been performed in PbPb collisions at √ sNN = 2.76 TeV with the CMS detector at the LHC, in a 7.2 μb−1 data sample. The number of opposite-sign muon pairs observed in the 60–120 GeV/c2 invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of (33.8± 5.5(stat) ± 4.4(syst)) × 10−8, in the |y| < 2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions. Submitted to Physical Review Letters ∗See Appendix A for the list of collaboration members ar X iv :1 10 2. 54 35 v1 [ nu cl -e x] 2 6 Fe b 20 11A search for Z bosons in the μ(+)μ(-) decay channel has been performed in PbPb collisions at √S(NN)=2.76  TeV with the CMS detector at the LHC, in a 7.2 μb(-1) data sample. The number of opposite-sign muon pairs observed in the 60-120 GeV/c(2) invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of [33.8±5.5(stat)±4.4(syst)]×10(-8), in the |y|<2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions.

MPICH-G2 Implementation of an Interactive Artificial Neural Network Training

Distributed Training of an Artificial Neural Network (ANN) has been implemented using MPICH-G2, and deployed on the testbed of the european CrossGrid project. Load balancing, including adaptative techniques, has been used to cope with the heterogeneous setup of computing resources. First results show the feasibility of this approach, and the opportunity for a Quality of Service framework. To give an example, a reduction in the training time from 20 minutes using a single local node downto less than 3 minutes using 10 nodes distributed across Spain, Poland, and Portugal, has been obtained.

Search for exotic particles decaying to WZ in pp collisions at √s=7 TeV

A bstractA search for new exotic particles decaying to the VZ final state is performed, where V is either a W or a Z boson decaying into two overlapping jets and the Z decays into a pair of electrons, muons or neutrinos. The analysis uses a data sample of pp collisions corresponding to an integrated luminosity of 5 fb−1 collected by the CMS experiment at the LHC at

RAID-1 and Data Stripping across the GRID

\sqrt{s}=7

Erratum: Search for anomalous tt¯ production in the highly-boosted all-hadronic final state

TeV in 2011. No significant excess is observed in the mass distribution of the VZ candidates compared with the background expectation from standard model processes. Model-dependent upper limits at the 95% confidence level are set on the product of the cross section times the branching fraction of hypothetical particles decaying to the VZ final state as a function of mass. Sequential standard model W′ bosons with masses between 700 and 940 GeV are excluded. In the Randall-Sundrum model for graviton resonances with a coupling parameter of 0.05, masses between 750 and 880 GeV are also excluded.

Erratum: Measurement of the tt¯ production cross section in the dilepton channel in pp collisions at √s = 8 TeV

Stripping techniques combined with an adequate replication policy across the Grid offer the possibility to improve significatively data access and processing times, while eliminating the need for local data mirroring, so saving significatively on storage costs. First results on a local cluster following a simple strategy are presented.

Measurements of inclusive W and Z cross sections in pp collisions at ps = 7 TeV

A search is presented for a massive particle, generically referred to as a Z′, decaying into a tt− pair. The search focuses on Z′ resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 fb−1. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z′ modeled for several widths, as well as for a Randall-Sundrum Kaluza-Klein gluon. In addition, the result contrain any enhancement in tt− production beyond expectations of the standard mode for tt invariant mass larger than 1 TeV/c2.

Measurement of the inclusive W and Z production cross sections in pp collisions at ps = 7TeV with the CMS experiment

In this study, the top-antitop quark (tt¯) production cross section is measured in proton-proton collisions at √s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb–1. The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239±2 (stat.)±11 (syst.)±6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with the prediction of the standard model.