S-Link to Gigabit Ethernet Adapter New Frame Segmentation for LHCb Data Acquisition System

Data Acquisition and Control Systems used in high energy physics experiments, such as those which will take place in the Large Hadron Collider (LHC) at CERN, require the specification of data formats and transmission protocols as well as the use of high speed links and interfaces. In this context, a new Frame Segmentation process will be presented and discussed, based on data formats adopted by the LHCb experience for the interconnection of two standardized systems: S-link and Gigabit Ethernet. Simulation results of the transfer capacity of the proposed mechanism will be also reported, together with guidelines for its physical implementation.Comment: 6 pages, 6 figures. Computing in High Energy and Nuclear Physics - CHEP03, La Jolla, CA, March 200

Parton showers as sources of energy-momentum deposition in the QGP and their implication for shockwave formation at RHIC and at the LHC

We derive the distribution of energy and momentum transmitted from a primary fast parton and its medium-induced bremsstrahlung gluons to a thermalized quark-gluon plasma. Our calculation takes into account the important and thus far neglected effects of quantum interference between the resulting color currents. We use our result to obtain the rate at which energy is absorbed by the medium as a function of time and find that the rate is modified by the quantum interference between the primary parton and secondary gluons. This Landau-Pomeranchuk-Migdal type interference persists for time scales relevant to heavy ion phenomenology. We further couple the newly derived source of energy and momentum deposition to linearized hydrodynamics to obtain the bulk medium response to realistic parton propagation and splitting in the quark-gluon plasma. We find that because of the characteristic large angle in-medium gluon emission and the multiple sources of energy deposition in a parton shower, formation of well defined Mach cones by energetic jets in heavy ion reactions is not likely.Comment: 8 pages, 4 figure

Monitoring the LHCb Experiment Computing Infrastructure with NAGIOS

LHCb has a large and complex infrastructure consisting of thousands of servers and embedded computers, hundreds of network devices and a lot of common infrastructure services such as shared storage, login and time services, databases and many others. All aspects that are operatively critic are integrated into the standard Experiment Control System (ECS) based on PVSSII. This enables non-expert operators to do first-line reactions. As the lower level and in particular for monitoring the infrastructure, the Control System itself depends on a secondary infrastructure, whose monitoring is based on NAGIOS. We present the design and implementation of the fabric management based on NAGIOS. Care has been taken to complement rather than duplicate functionality available in the Experiment Control System

Monitoring the LHCb Experiment Computing Infrastructure with NAGIOS

LHCb has a large and complex infrastructure consisting of thousands of servers and embedded computers, hundreds of network devices and a lot of common infrastructure services such as shared storage, login and time services, databases and many others. All aspects that are operatively critic are integrated into the standard Experiment Control System (ECS) based on PVSSII. This enables non-expert operators to do first-line reactions. As the lower level and in particular for monitoring the infrastructure, the Control System itself depends on a secondary infrastructure, whose monitoring is based on NAGIOS. We present the design and implementation of the fabric management based on NAGIOS. Care has been taken to complement rather than duplicate functionality available in the Experiment Control System

Chaotic advection of reacting substances: Plankton dynamics on a meandering jet

We study the spatial patterns formed by interacting populations or reacting chemicals under the influence of chaotic flows. In particular, we have considered a three-component model of plankton dynamics advected by a meandering jet. We report general results, stressing the existence of a smooth-filamental transition in the concentration patterns depending on the relative strength of the stirring by the chaotic flow and the relaxation properties of planktonic dynamical system. Patterns obtained in open and closed flows are compared.Comment: 5 pages, 3 figues, latex compiled with modegs.cl

Excitable media in open and closed chaotic flows

We investigate the response of an excitable medium to a localized perturbation in the presence of a two-dimensional smooth chaotic flow. Two distinct types of flows are numerically considered: open and closed. For both of them three distinct regimes are found, depending on the relative strengths of the stirring and the rate of the excitable reaction. In order to clarify and understand the role of the many competing mechanisms present, simplified models of the process are introduced. They are one-dimensional baker-map models for the flow and a one-dimensional approximation for the transverse profile of the filaments.Comment: 14 pages, 16 figure

Phototactic clustering of swimming microorganisms in a turbulent velocity field

We study the distribution of swimming microorganisms advected by a two-dimensional smooth turbulent flow and attracted towards a light source through phototaxis. It is shown that particles aggregate along a dynamical attractor with fractal measure whose dimension depends on the strength of the phototaxis. Using an effective diffusion approximation for the flow, we derive an analytic expression for the increase in light exposure over the aggregate and by extension an accurate prediction for the fractal dimension based on the properties of the advection and the statistics of the attracting field

The IRAM-30m line survey of the Horsehead PDR: I. CF+ as a tracer of C+ and a measure of the Fluorine abundance

C+ is a key species in the interstellar medium but its 158 {\mu}m fine structure line cannot be observed from ground-based telescopes. Current models of fluorine chemistry predict that CF+ is the second most important fluorine reservoir, in regions where C+ is abundant. We detected the J = 1-0 and J = 2-1 rotational lines of CF+ with high signal-to-noise ratio towards the PDR and dense core positions in the Horsehead. Using a rotational diagram analysis, we derive a column density of N(CF+) = (1.5 - 2.0) \times 10^12 cm^-2. Because of the simple fluorine chemistry, the CF+ column density is proportional to the fluorine abundance. We thus infer the fluorine gas-phase abundance to be F/H = (0.6 - 1.5) \times 10^-8. Photochemical models indicate that CF+ is found in the layers where C+ is abundant. The emission arises in the UV illuminated skin of the nebula, tracing the outermost cloud layers. Indeed, CF+ and C+ are the only species observed to date in the Horsehead with a double peaked line profile caused by kinematics. We therefore propose that CF+, which is detectable from the ground, can be used as a proxy of the C+ layers.Comment: Accepted to A&A, 4 pages, 4 figures, 2 table