ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in root s=7 TeV proton-proton collisions. Phys. Lett. B, 710(1), 67–85.
Abstract: A search for squarks and gluinos in events containing jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2011 by the ATLAS experiment in root s = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation is observed in 1.04 fb(-1) of data. Gluino and squark masses below 700 GeV and 875 GeV respectively are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino. The exclusion limit increases to 1075 GeV for squarks and gluinos of equal mass. In MSUGRA/CMSSM models with tan beta = 10, A(0) = 0 and μ> 0, squarks and gluinos of equal mass are excluded for masses below 950 GeV. These limits extend the region of supersymmetric parameter space excluded by previous measurements.
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Bates, R. L. et al, Bernabeu Verdu, J., Civera, J. V., Gonzalez, F., Lacasta, C., & Sanchez, J. (2012). The ATLAS SCT grounding and shielding concept and implementation. J. Instrum., 7, P03005.
Abstract: This paper describes the design and implementation of the grounding and shielding system for the ATLAS SemiConductor Tracker (SCT). The mitigation of electromagnetic interference and noise pickup through power lines is the critical design goal as they have the potential to jeopardize the electrical performance. We accomplish this by adhering to the ATLAS grounding rules, by avoiding ground loops and isolating the different subdetectors. Noise sources are identified and design rules to protect the SCT against them are described. A rigorous implementation of the design was crucial to achieve the required performance. This paper highlights the location, connection and assembly of the different components that affect the grounding and shielding system: cables, filters, cooling pipes, shielding enclosure, power supplies and others. Special care is taken with the electrical properties of materials and joints. The monitoring of the grounding system during the installation period is also discussed. Finally, after connecting more than four thousand SCT modules to all of their services, electrical, mechanical and thermal within the wider ATLAS experimental environment, dedicated tests show that noise pickup is minimised.
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Altheimer, A. et al, Villaplana Perez, M., & Vos, M. (2012). Jet substructure at the Tevatron and LHC: new results, new tools, new benchmarks. J. Phys. G, 39(6), 063001–44pp.
Abstract: In this paper, we review recent theoretical progress and the latest experimental results in jet substructure from the Tevatron and the LHC. We review the status of and outlook for calculation and simulation tools for studying jet substructure. Following up on the report of the Boost 2010 workshop, we present a new set of benchmark comparisons of substructure techniques, focusing on the set of variables and grooming methods that are collectively known as 'top taggers'. To facilitate further exploration, we have attempted to collect, harmonize and publish software implementations of these techniques.
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Arbelaez, C., Hirsch, M., & Reichert, L. (2012). Supersymmetric mass spectra and the seesaw type-I scale. J. High Energy Phys., 02(2), 112.
Abstract: We calculate supersymmetric mass spectra with cMSSM boundary conditions and a type-I seesaw mechanism added to explain current neutrino data. Using published, estimated errors on SUSY mass observables for a combined LHC+ILC analysis, we perform a theoretical chi(2) analysis to identify parameter regions where pure cMSSM and cMSSM plus seesaw type-I might be distinguishable with LHC+ILC data. The most important observables are determined to be the (left) smuon and selectron masses and the splitting between them, respectively. Splitting in the (left) smuon and selectrons is tiny in most of cMSSM parameter space, but can be quite sizeable for large values of the seesaw scale, m S S. Thus, for very roughly m(SS) >= 10(14) GeV hints for type-I seesaw might appear in SUSY mass measurements. Since our numerical results depend sensitively on forecasted error bars, we discuss in some detail the accuracies, which need to be achieved, before a realistic analysis searching for signs of type-I seesaw in SUSY spectra can be carried out.
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Hirsch, M., Malinsky, M., Porod, W., Reichert, L., & Staub, F. (2012). Hefty MSSM-like light Higgs in extended gauge models. J. High Energy Phys., 02(2), 084.
Abstract: It is well known that in the MSSM the lightest neutral Higgs h(0) must be, at the tree level, lighter than the Z boson and that the loop corrections shift this stringent upper bound up to about 130GeV. Extending the MSSM gauge group in a suitable way, the new Higgs sector dynamics can push the tree-level mass of h(0) well above the tree-level MSSM limit if it couples to the new gauge sector. This effect is further pronounced at the loop level and h(0) masses in the 140GeV ballpark can be reached easily. We exemplify this for a sample setting with a low-scale U(1)(R) x U(1)(B-L) gauge symmetry in which neutrino masses can be implemented via the inverse seesaw mechanism.
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