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The software of the ATLAS beam pick-up based LHC monitoring system
Stockholm University, Faculty of Science, Department of Physics. (Elementarpartikelfysik)
2010 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 219, no 1Article in journal (Refereed) Published
Abstract [en]

The ATLAS BPTX stations are comprised of electrostatic button pick-up detectors, located 175 m away along the beam pipe on both sides of ATLAS. The pick-ups are installed as a part of the LHC beam instrumentation and used by ATLAS for timing purposes. The signals from the ATLAS BPTX detectors are used both in the trigger system and for a stand-alone monitoring system for the LHC beams and timing signals. The monitoring software measures the phase between collisions and clock with high accuracy in order to guarantee a stable phase relationship for optimal signal sampling in the sub-detector front-end electronics. It also measures the properties of the individual bunches and the structure of the beams. In this paper, the BPTX monitoring software is described, its algorithms explained and a few example monitoring displays shown. In addition, results from the monitoring system during the first period of single beam running in September 2008 are presented.

Place, publisher, year, edition, pages
IOP Publishing, 2010. Vol. 219, no 1
National Category
Subatomic Physics
URN: urn:nbn:se:su:diva-63067DOI: 10.1088/1742-6596/219/2/022040OAI: diva2:446617
Available from: 2011-10-07 Created: 2011-10-07 Last updated: 2011-10-10Bibliographically approved
In thesis
1. Searches for exotic stable massive particles with the ATLAS experiment
Open this publication in new window or tab >>Searches for exotic stable massive particles with the ATLAS experiment
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents two signature-based searches for exotic long-lived particles using experimental data collected by the ATLAS experiment at the Large Hadron Collider (LHC) at CERN. At the LHC, proton-proton collisions take place at the world-record center-of-mass energy of 7 TeV and luminosities of up to  3×1033 cm-2s-1 . New physics has long been anticipated at the LHC and in this thesis two searches for hitherto unobserved particles are presented.

Long-lived heavy hadrons have been predicted by models of supersymmetry, and these were the target of the first physics analysis. Using measurements of timing and energy loss, a search for so-called R-hadrons was performed. No excess was observed in the data, and new lower limits were established on the masses of meta-stable supersymmetric particles with color charge: mgluino > 562-586 GeV (depending on choice of scattering model), mstop > 309 GeV and msbottom > 294 GeV. These constraints are the most stringent limits published to date.

In addition, a ``blue-sky'' search was made for objects possessing high electric charge. Ionization energy loss measurements were combined with variables describing the shape of electromagnetic showers to separate the sought signal from background processes. No event in the experimental data passed the selection and the results are in agreement with a background-only hypothesis. Upper limits between 1-12 pb were computed for the production cross sections of particles with electric charge 6e ≤ |q| ≤ 17e and mass 200 ≤ m ≤ 1000 GeV. This is the first dedicated search for such particles at the LHC.

Finally, a system designed to monitor the LHC beams and timing signals based on beam pick-up detectors is described together with results from early LHC operation.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2011. 185 p.
ATLAS, ATLAS experiment, supersymmetry, squark, gluino, stable massive particles, long-lived particles, physics analysis, search analysis, LHC, Large Hadron Collider
National Category
Subatomic Physics
Research subject
urn:nbn:se:su:diva-63068 (URN)978-91-7447-341-4 (ISBN)
Public defence
2011-11-04, sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Available from: 2011-10-13 Created: 2011-10-07 Last updated: 2011-10-10Bibliographically approved

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