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Search for Stable Hadronising Squarks and Gluinos at the ATLAS Experiment at the LHC
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics.
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2011 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 1, 1-19 p.Article in journal (Refereed) Published
Abstract [en]

Hitherto unobserved long-lived massive particles with electric and/or colour charge are predicted by a range of theories which extend the Standard Model. In this Letter a search is performed at the ATLAS experiment for slow-moving charged particles produced in proton–proton collisions at 7 TeV centre-of-mass energy at the LHC, using a data-set corresponding to an integrated luminosity of 34 pb−1. No deviations from Standard Model expectations are found. This result is interpreted in a framework of supersymmetry models in which coloured sparticles can hadronise into long-lived bound hadronic states, termed R-hadrons, and 95% CL limits are set on the production cross-sections of squarks and gluinos. The influence of R-hadron interactions in matter was studied using a number of different models, and lower mass limits for stable sbottoms and stops are found to be 294 and 309 GeV respectively. The lower mass limit for a stable gluino lies in the range from 562 to 586 GeV depending on the model assumed. Each of these constraints is the most stringent to date.

Place, publisher, year, edition, pages
2011. Vol. 701, no 1, 1-19 p.
Keyword [en]
Supersymmetry, Long-lived particle, R-hadron, Limit
National Category
Subatomic Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-63000DOI: 10.1016/j.physletb.2011.05.010ISI: 000292719700001OAI: oai:DiVA.org:su-63000DiVA: diva2:446320
Projects
Atlas
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note
Publikationen har totalt 3042 författare, G. Aad et al.Available from: 2011-10-06 Created: 2011-10-06 Last updated: 2017-12-08Bibliographically 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.
Keyword
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
Physics
Identifiers
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)
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Supervisors
Available from: 2011-10-13 Created: 2011-10-07 Last updated: 2011-10-10Bibliographically approved

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Åsman, BarbroBohm, ChristianClément, ChristopheEriksson, DanielGellerstedt, KarlHellman, StenHidvégi, AttilaHolmgren, Sven-OlofJohansen, MarianneJohansson, ErikJon-And, KerstinLundberg, JohanMilstead, DavidMoa, TorbjörnNordkvist, BjörnOhm, ChristianPapadelis, ArasSelldén, BjörnSilverstein, SamuelSjölin, JörgenStrandberg, SaraTylmad, MajaYang, Zhaoyu
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