6,196 research outputs found
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
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