A scalable data taking system at a test beam for LHC

We propose the installation of a data taking system at a test beam for the simultaneous test of LHC detectors, trigger and readout electronics, together with the development of the supporting architecture in a multiprocessor environment. A strong emphasis is put on a highly modular design, such that new hardware and software developments can be conveniently introduced for training and evaluation. One of the main thrusts of the project will be the modelling and system integration of different readout architectures, which are meant to provide a valuable training ground for new techniques. To address these aspects in a realistic manner, we propose to collaborate with two detector R+D projects

Metadata for ATLAS

This document provides an overview of the metadata, which are needed to characterize ATLAS event data at different levels (a complete run, data streams within a run, luminosity blocks within a run, individual events)

Experience with fibre channel in the environment of the ATLAS DAQ protoype "-1" project

Fibre Channel equipment has been evaluated in the environment of the ATLAS DAQ prototype "-1". Fibre Channel PCI and PMC cards have been tested on PwerPC-based VME processor boards running LynxOS and on Pentium-based personal computers running Windows NT. The performance in terms of overhead and bandwidth has been measured in point-to-point, arbitrated loop and fabric configuration with a Fibre Ch annel switch. The possible used of the equipment for event building in the ATLAS DAQ prototype "-1" has been studied

Using Linux PCs in DAQ applications

ATLAS Data Acquisition/Event Filter "-1" (DAQ/EF1) project provides the opportunity to explore the use of commodity hardware (PCs) and Open Source Software (Linux) in DAQ applications. In DAQ/EF-1 there is an element called the LDAQ which is responsible for providing local run-control, error-handling and reporting for a number of read- out modules in front end crates. This element is also responsible for providing event data for monitoring and for the interface with the global control and monitoring system (Back-End). We present the results of an evaluation of the Linux operating system made in the context of DAQ/EF-1 where there are no strong real-time requirements. We also report on our experience in implementing the LDAQ on a VMEbus based PC (the VMIVME-7587) and a desktop PC linked to VMEbus with a Bit3 interface both running Linux. We then present the problems encountered during the integration with VMEbus, the status of the LDAQ implementation and draw some conclusions on the use of Linux in DAQ applications. (18 refs)

Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment

We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment

Helicity-dependent cross sections and double-polarization observable E in η photoproduction from quasifree protons and neutrons

Precise helicity-dependent cross sections and the double-polarization observable E were measured for η photoproduction from quasifree protons and neutrons bound in the deuteron. The η → 2γ and η → 3π0 → 6γ decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were detected with the electromagnetic calorimeters Crystal Ball and TAPS, which covered 98% of the full solid angle. The results show that the narrow structure observed earlier in the unpolarized excitation function of η photoproduction off the neutron appears only in reactions with antiparallel photon and nucleon spin (σ1/2). It is absent for reactions with parallel spin orientation (σ3/2) and thus very probably related to partial waves with total spin 1/2. The behavior of the angular distributions of the helicity-dependent cross sections was analyzed by fitting them with Legendre polynomials. The results are in good agreement with a model from the Bonn-Gatchina group, which uses an interference of P11 and S11 partial waves to explain the narrow structure

Inclusive search for same-sign dilepton signatures in pp collisions at root s=7 TeV with the ATLAS detector

An inclusive search is presented for new physics in events with two isolated leptons (e or mu) having the same electric charge. The data are selected from events collected from p p collisions at root s = 7 TeV by the ATLAS detector and correspond to an integrated luminosity of 34 pb(-1). The spectra in dilepton invariant mass, missing transverse momentum and jet multiplicity are presented and compared to Standard Model predictions. In this event sample, no evidence is found for contributions beyond those of the Standard Model. Limits are set on the cross-section in a fiducial region for new sources of same-sign high-mass dilepton events in the ee, e mu and mu mu channels. Four models predicting same-sign dilepton signals are constrained: two descriptions of Majorana neutrinos, a cascade topology similar to supersymmetry or universal extra dimensions, and fourth generation d-type quarks. Assuming a new physics scale of 1 TeV, Majorana neutrinos produced by an effective operator V with masses below 460 GeV are excluded at 95% confidence level. A lower limit of 290 GeV is set at 95% confidence level on the mass of fourth generation d-type quarks

Measurement of the top quark-pair production cross section with ATLAS in pp collisions at \sqrt{s}=7\TeV

A measurement of the production cross-section for top quark pairs(\ttbar) in $pp$ collisions at \sqrt{s}=7 \TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron $e$ or muon $\mu$) with large missing transverse energy and at least four jets, and dilepton ($ee$, $\mu\mu$ or $e\mu$) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-\ttbar Standard Model processes are estimated using data-driven methods and determined to be $12.2 \pm 3.9$ events and $2.5 \pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM \ttbar production. The inclusive top quark pair production cross-section is measured to be \sigmattbar=145 \pm 31 ^{+42}_{-27} pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.Comment: 30 pages plus author list (50 pages total), 9 figures, 11 tables, CERN-PH number and final journal adde