arXiv subjects

Andrea Valassi

Publications and source records attributed to Andrea Valassi.

22 records · Page 2Linked to original sources

arXiv2018

HEP Software Foundation Community White Paper Working Group - Software Development, Deployment and Validation

The High Energy Phyiscs community has developed and needs to maintain many tens of millions of lines of code and to integrate effectively the work of thousands of developers across large collaborations. Software needs to be built, validated, and deployed across hundreds of sites. Software also has a lifetime of many years, frequently beyond that of the original developer, it must be developed with sustainability in mind. Adequate recognition of software development as a critical task in the HEP community needs to be fostered and an appropriate publication and citation strategy needs to be developed. As part of the HEP Softare Foundation's Community White Paper process a working group on Software Development, Deployment and Validation was formed to examine all of these issues, identify best practice and to formulare recommendations for the next decade. Its report is presented here.

physics.comp-ph↗

arXiv2014

Information and treatment of unknown correlations in the combination of measurements using the BLUE method

We discuss the effect of large positive correlations in the combinations of several measurements of a single physical quantity using the Best Linear Unbiased Estimate (BLUE) method. We suggest a new approach for comparing the relative weights of the different measurements in their contributions to the combined knowledge about the unknown parameter, using the well-established concept of Fisher information. We argue, in particular, that one We discuss the effect of large positive correlations in the combinations of several measurements of a single physical quantity using the Best Linear Unbiased Estimate (BLUE) method. We suggest a new approach for comparing the relative weights of the different measurements in their contributions to the combined knowledge about the unknown parameter, using the well-established concept of Fisher information. We argue, in particular, that one contribution to information comes from the collective interplay of the measurements through their correlations and that this contribution cannot be attributed to any of the individual measurements alone. We show that negative coefficients in the BLUE weighted average invariably indicate the presence of a regime of high correlations, where the effect of further increasing some of these correlations is that of reducing the error on the combined estimate. In these regimes, we stress that assuming fully correlated systematic uncertainties is not a truly conservative choice, and that the correlations provided as input to BLUE combinations need to be assessed with extreme care instead. In situations where the precise evaluation of these correlations is impractical, or even impossible, we provide tools to help experimental physicists perform more conservative combinations.

physics.data-an↗

arXiv2003

Detector Description Framework in LHCb

The Gaudi architecture and framework are designed to provide a common infrastructure and environment for simulation, filtering, reconstruction and analysis applications. In this context, a Detector Description Service was developed in LHCb in order to also provide easy and coherent access to the description of the experimental apparatus. This service centralizes every information about the detector, including geometry, materials, alignment, calibration, structure and controls. From the proof of concept given by the first functional implementation of this service late 2000, the Detector Description Service has grown and has become one of the major components of the LHCb software, shared among all applications, including simulation, reconstruction, analysis and visualization. We describe here the full and functional implementation of the service. We stress the easiness of customization and extension of the detector description by the user, on the seamless integration with condition databases in order to handle time dependent data and on the choice of XML as a persistency back-end for LHCb Detector data. We show how the detector description can be shared but still contains application specific data and keeps at the same time several levels of granularity. We present several external tools which provide additional value to the Detector Description Service like a dedicated, easy to use XML editor and different geometry checkers. We finally give hints on how this service could evolve to be part of a common effort between all LHC experiments that would aim at defining common Detector description tools at the level of the LCG project.

physics.ins-det↗

arXiv2003

Objectivity Data Migration

In this article we describe the migration of event data collected by the COMPASS and HARP experiments at CERN. Together these experiments have over 300TB of physics data stored in Objectivity/DB that had to be transferred to a new data management system by the end of Q1 2003 and Q2 2003 respectively. To achieve this, data needed to be processed with a rate close to 100MB/s, employing 14 tape drives and a cluster of 30 Linux servers. The new persistency solution to accommodate the data is built upon relational databases for metadata storage and standard "flat" files for the event data. The databases contain collections of 109 events and allow generic queries or direct navigational access to the data, preserving the original C++ user API. The central data repository at CERN is implemented using several Oracle9i servers on Linux and the CERN Mass Storage System CASTOR.

hep-ex↗