DIRAC framework evaluation for the Fermi\boldsymbol{Fermi}-LAT and CTA experiments

DIRAC (Distributed Infrastructure with Remote Agent Control) is a general framework for the management of tasks over distributed heterogeneous computing environments. It has been originally developed to support the production activities of the LHCb (Large Hadron Collider Beauty) experiment and today is extensively used by several particle physics and biology communities. Current ($Fermi$ Large Area Telescope -- LAT) and planned (Cherenkov Telescope Array -- CTA) new generation astrophysical/cosmological experiments, with very large processing and storage needs, are currently investigating the usability of DIRAC in this context. Each of these use cases has some peculiarities: $Fermi$-LAT will interface DIRAC to its own workflow system to allow the access to the grid resources, while CTA is using DIRAC as workflow management system for Monte Carlo production and analysis on the grid. We describe the prototype effort that we lead toward deploying a DIRAC solution for some aspects of $Fermi$-LAT and CTA needs.Comment: proceedings to CHEP 2013 conference : http://www.chep2013.org

HTC Scientific Computing in a Distributed Cloud Environment

This paper describes the use of a distributed cloud computing system for high-throughput computing (HTC) scientific applications. The distributed cloud computing system is composed of a number of separate Infrastructure-as-a-Service (IaaS) clouds that are utilized in a unified infrastructure. The distributed cloud has been in production-quality operation for two years with approximately 500,000 completed jobs where a typical workload has 500 simultaneous embarrassingly-parallel jobs that run for approximately 12 hours. We review the design and implementation of the system which is based on pre-existing components and a number of custom components. We discuss the operation of the system, and describe our plans for the expansion to more sites and increased computing capacity

Technical support for Life Sciences communities on a production grid infrastructure

Production operation of large distributed computing infrastructures (DCI) still requires a lot of human intervention to reach acceptable quality of service. This may be achievable for scientific communities with solid IT support, but it remains a show-stopper for others. Some application execution environments are used to hide runtime technical issues from end users. But they mostly aim at fault-tolerance rather than incident resolution, and their operation still requires substantial manpower. A longer-term support activity is thus needed to ensure sustained quality of service for Virtual Organisations (VO). This paper describes how the biomed VO has addressed this challenge by setting up a technical support team. Its organisation, tooling, daily tasks, and procedures are described. Results are shown in terms of resource usage by end users, amount of reported incidents, and developed software tools. Based on our experience, we suggest ways to measure the impact of the technical support, perspectives to decrease its human cost and make it more community-specific.Comment: HealthGrid'12, Amsterdam : Netherlands (2012

Vers une fédération de Cloud Académique dans France Grilles

Vers une fédération de Cloud Académique dans France Grille

Measurement of relative branching fractions of B decays to ψ(2S) and J/ψ mesons

The relative rates of B-meson decays into J/ψ and ψ(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions (B) are measured to be B(B +→ψ(2S)K + ) B(B+→J/ψK+) = 0.594±0.006(stat)±0.016(syst)±0.015(Rψ), B(B0→ψ(2S)K ∗0) B(B0→J/ψK∗0) = 0.476±0.014(stat)±0.010(syst)±0.012(Rψ), B(B0 s →ψ(2S)φ) B(B0 s →J/ψφ) = 0.489±0.026(stat)±0.021(syst)±0.012(Rψ), where the third uncertainty is from the ratio of the ψ(2S) and J/ψ branching fractions to μ + μ −. 1 Introductio

NLO predictions for the growth of F2F_2 at small xx and comparison with experimental data

We present parametrizations for the proton structure function $F_2$ in the next to leading order in perturbative QCD. The calculations show that the dominant term to $F_2(x,Q^2)$ should grow as x^{-\ls} for small $x$ values, with the exponent \ls being essentially independent of $Q^2$. Comparisons with the most recent H1 and ZEUS data confirm the value \ls \sim 0.35 obtained previously from fits to low energy data.Comment: 18 page

Optimized PET module for both pixelated and monolithic scintillator crystals

[eng] Time-of-Flight Positron Emission Tomography (TOF-PET) scanners demand fast and efficient photo-sensors and scintillators coupled to fast readout electronics. Nowadays, there are two main configurations regarding the scintillator crystal geometry: the segmented or pixelated and the monolithic approach. Depending on the cost, spatial resolution and time requirements of the PET module, one can choose between one or another. The pixelated crystal is the most extensive configuration on TOF-PET scanners as the coincidence time resolution is better compared to the monolithic. On the contrary, monolithic scintillator crystals for Time-of-Flight Positron Emission Tomography (ToF-PET) are increasing in popularity this last years due to their performance potential and price in front of the commonly used segmented crystals. On one hand, monolithic blocks allows to determine 3D information of the gamma-ray interaction inside the crystal, which enables the possibility to correct the parallax error (radial astigmatism) at off-center positions within a PET scanner, resulting in an improvement of the spatial resolution of the device. On the other hand, due to the simplicity during the crystal manufacturing process as well as for the detector design, the price is reduced compared to a regular pixelated detector. The thesis starts with the use of HRFlexToT, an ASIC developed in this group, as the readout electronics for measurements with single pixelated crystals coupled to different SiPMs. These measurements show an energy linearity error of 3% and an energy resolution below 10% of the 511 keV photopeak. Single Photon Time Resolution (SPTR) measurements performed using an FBK SiPM NUV-HD (4 mm x 4 mm pixel size) and a Hamamatsu SiPM S13360-3050CS gave a 141 ps and 167 ps FWHM respectively. Coincidence Time Resolution (CTR) measurements with small cross-section pixelated crystals (LFS crystal, 3 m x 3 mm x 20 mm ) coupled to a single Hamamatsu SiPM S13360-3050CS provides a CTR of 180 ps FWHM. Shorter crystals (LSO:Ce Ca 0.4%) coupled to a Hamamatsu S13360-3050CS SiPM or FBK-NUVHD yields a CTR of 117 ps and 119 ps respectively. Then, the results with different monolithic crystals and SiPM sensors using HRFlexToT ASIC will be presented. A Lutetium Fine Silicate (LFS) of 25 mm x 25 mm x 20 mm, a small LSO:Ce Ca 0.2% of 8 mm x 8 mm x 5 mm and a Lutetium-Yttrium Oxyorthosilicate (LYSO) of 25 mm x 25 mm x 10 mm has been experimentally tested. After subtracting the TDC contribution (82 ps FWHM), a coincidence time resolution of 244 ps FWHM for the small LFS crystal and 333 ps FWHM for the largest LFS one is reported. Additionally, a novel time calibration correction method for CTR improvement that involves a pico-second pulsed laser will be detailed. In the last part of the dissertation, a new developed simulation framework that will enable the cross-optimization of the whole PET system will be explained. It takes into consideration the photon physics interaction in the scintillator crystal, the sensor response (sensor size, pixel pitch, dead area, capacitance) and the readout electronics behavior (input impedance, noise, bandwidth, summation). This framework has allowed us to study a new promising approach that will help reducing the CTR parameter by segmenting a large area SiPM into "m" smaller SiPMs and then summing them to recover all the signal spread along these smaller sensors. A 15% improvement on time resolution is expected by segmenting a 4 mm x 4 mm single sensor into 9 sensors of 1.3 mm x 1.3 mm with respect to the case where no segmentation is applied.[cat] Aquesta tesi tenia com a objectiu la fabricació i avaluació d'un prototip per a detecció de fotons gamma en aplicació per imatge mèdica, més concretament en Tomografia per Emissió de Positrons amb mesura de temps de vol (TOF-PET). L'avaluació del mòdul va començar fent una caracterització completa del chip (ASIC) anomenat HRFlexToT, una versió nova i millorada de l'antic chip FlexToT, desenvolupat i fabricat pel grup de la Unitat Tecnològica del ICC de la Universitat de Barcelona. Aquesta avaluació inicial del chip compren des de la comprovació de les funcionalitats bàsiques fins a la generació d'un test automàtic per generar les gràfiques de linealitat corresponents durant el test elèctric. Un cop donat per bo, es va muntar en una placa demostrada, també ideada per l'equip d'enginyers del grup, i ja quedava llesta per realitzar les mesures pertinents. Tot seguit, es varen realitzar les mesures òptiques, que incloïa mesures de Singe Photon Time Resolution (SPTR) i de Coincidence Time Resolution (CTR). Aquest valors actuen com a figures de mèrit a l'hora de comparar les prestacions amb d'altres ASICs competidors del HRFlexToT. Es van obtenir valors de 60 ps de resposta pel que respecta al SPTR i de 115 ps de CTR en cristalls segmentats, una millora entorn del 20-30% respecte a la versió predecessora del chip. Aquests valors mostren ser el límit de l'estat de l'art actual i amb aquesta idea es van començar a fer altres mesures, en aquest cas amb cristall monolítics, blocs grans llegits per diversos fotosensors de les empreses Hamamatsu i FBK. Per altra banda, es va provar el funcionament del ASIC en configuració anomenada monolítica, on el cristall centellejador s'utilitza en blocs grans en coptes d’emprar cristalls segmentats, això abarateix el cost total del detector. Aquesta configuració degrada les propietats de CTR, un paràmetre crític a l'hora de tenir un producte bo i eficient. S’han obtingut mesures de 250 ps de CTR amb aquesta configuració, d’on es pot dir que l’HRFlexToT es trobar a l’estat de l’art de la tecnologia electrònica dedicada a TOF-PET amb cristalls segmentats i monolítics. Finalment, es va desenvolupar una nova eina simulació que consisteix en un sistema híbrid entre un simulador físic i un electrònic per tal de tenir una idea del comportament complet del mòdul detector. Una solució que ningú havia provat fins ara o que no es pot trobar en la literatura