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Post Info TOPIC: Supersymmetry
Blobrana


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Supersymmetry Breaking
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Title: Supersymmetry Breaking Triggered by Monopoles
Authors: Csaba Csaki, David Curtin, Vikram Rentala, Yuri Shirman, John Terning

We investigate N = 1 supersymmetric gauge theories where monopole condensation triggers supersymmetry breaking in a metastable vacuum. The low-energy effective theory is an O'Raifeartaigh-like model of the kind investigated recently by Shih where the R-symmetry can be spontaneously broken. We examine several implementations with varying degrees of phenomenological interest.

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Blobrana


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RE: Supersymmetry
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Title: Stealth Supersymmetry
Authors: JiJi Fan, Matthew Reece, Joshua T. Ruderman

We present a broad class of supersymmetric models that preserve R-parity but lack missing energy signatures. These models have new light particles with weak-scale supersymmetric masses that feel SUSY breaking only through couplings to the MSSM. This small SUSY breaking leads to nearly degenerate fermion/boson pairs, with small mass splittings and hence small phase space for decays carrying away invisible energy. The simplest scenario has low-scale SUSY breaking, with missing energy only from soft gravitinos. This scenario is natural, lacks artificial tunings to produce a squeezed spectrum, and is consistent with gauge coupling unification. The resulting collider signals will be jet-rich events containing false resonances that could resemble signatures of R-parity violation. We discuss several concrete examples of the general idea, and emphasize gamma + jet + jet resonances, displaced vertices, and very large numbers of b-jets as three possible discovery modes.

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Blobrana


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Title: The Quest for Supersymmetry: Early LHC Results versus Direct and Indirect Neutralino Dark Matter Searches
Authors: Stefano Profumo

We compare the first results on searches for supersymmetry with the Large Hadron Collider (LHC) to the current and near-term performance of experiments sensitive to neutralino dark matter. We limit our study to the particular slices of parameter space of the constrained minimal supersymmetric extension to the Standard Model where CMS and ATLAS exclusion limits have been presented so far. We show where, on that parameter space, the lightest neutralino possesses a thermal relic abundance matching the value inferred by cosmological observations. We then calculate rates for, and estimate the performance of, experiments sensitive to direct and indirect signals from neutralino dark matter. We argue that this is a unique point in time, where the quest for supersymmetry -- at least in one of its practical and simple incarnations -- is undergoing a close scrutiny from the LHC and from dark matter searches that is both synergistic and complementary. Should the time of discovery finally unravel, the current performances of the collider program and of direct and indirect dark matter searches are at a conjuncture offering unique opportunities for a breakthrough on the nature of physics beyond the Standard Model.

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Blobrana


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Title: Relating quarks and leptons without grand-unification
Authors: S. Morisi, E. Peinado, Yusuke Shimizu, J. W. F. Valle

In combination with supersymmetry, flavor symmetry may relate quarks with leptons, even in the absence of a grand-unification group. We propose an SU(3)xSU(2)xU(1) model where both supersymmetry and the assumed A4 flavor symmetries are softly broken, reproducing well the observed fermion mass hierarchies and predicting: (i) a relation between down-type quarks and charged lepton masses, and (ii) a correlation between the Cabibbo angle in the quark sector, and the reactor angle characterising CP violation in neutrino oscillations.

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Blobrana


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Posts: 131433
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Squarks and gluinos
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Title: Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in sqrt(s) = 7 TeV proton-proton collisions
Authors: The ATLAS Collaboration

A search for squarks and gluinos in final states containing jets, missing transverse momentum and no electrons or muons is presented. The data were recorded by the ATLAS experiment in sqrt(s) = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 35 inverse picobarns of analysed data. Gluino masses below 500 GeV 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 increases to 870 GeV for equal mass squarks and gluinos. In MSUGRA/CMSSM models with tan(beta)= 3, A_0=0 and mu>0, squarks and gluinos of equal mass are excluded below 775 GeV. These are the most stringent limits to date.

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Blobrana


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RE: Supersymmetry
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The search for sparticles

According to Supersymmetry theory every particle must have its own partner particle - a 'sparticle' - but the ATLAS team report that, so far, they have yet to find a single sparticle.
I asked Alan Barr, one of the Oxford University physicists behind ATLAS, about the search for sparticles, what the latest results tell us, and whether the theorists should be worried:
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Blobrana


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Posts: 131433
Date:
Supersymmetry theory
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Latest results from the LHC are casting doubt on the theory of supersymmetry.

There is growing anxiety that supersymmetry theory, however elegant it might be, is wrong. Data from the Large Hadron Collider (LHC), a 27-kilometre proton smasher that straddles the FrenchSwiss border near Geneva, Switzerland, have shown no sign of the 'super particles' that the theory predicts
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Blobrana


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Posts: 131433
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RE: Supersymmetry
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Title: Confinement, brane symmetry and the Julia-Toulouse approach for defects condensation
Authors: L. S. Grigorio, M. S. Guimaraes, R. Rougemont, C. Wotzasek

In this work the phenomenon of charge confinement is approached in various contexts. An universal criteria for the identification of this phenomenon is suggested: the so-called spontaneous breaking of the brane symmetry. This local symmetry has its most common incarnation in the Dirac string ambiguity present in the electromagnetic theory with monopoles. The spontaneous breaking of the brane symmetry means that the Dirac string becomes part of a brane invariant observable which hides the realization of such a symmetry and develops energy content in the confinement regime. The establishment of this regime can be reached through the condensation of topological defects. The effective theory of the confinement regime can be obtained with the Julia-Toulouse prescription which, originally introduced as the dual mechanism to the Abelian Higgs Mechanism, is generalized in this paper to become fully compatible with Elitzur's theorem and to describe more general condensates which may break Lorentz and discrete spacetime symmetries. This generalized Julia-Toulouse approach for defects condensation is presented here through a series of different applications

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Blobrana


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Title: Tiny neutrino mass from SUSY and lepton number breaking sector
Authors: Naoyuki Haba, Tetsuo Shindou

We suggest new setup where SUSY breaking spurion F-term possesses lepton number. This setup not only modifies sparticle mass spectra but also realises several new models, where neutrino mass is naturally induced through radiative corrections. We here suggest two new models; the first one is (i): pseudo-Dirac/Schizophrenic neutrino model, and the second one is (ii): pure Majorana neutrino model. We will also show this setup can naturally apply to the supersymmetric Zee-Babu model.

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Blobrana


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Title: Top Channel for Early SUSY Discovery at the LHC
Authors: Gordon L. Kane, Eric Kuflik, Ran Lu, Lian-Tao Wang

In recent years many models of supersymmetry have implied a large production rate for events including a high multiplicity of third generation quarks, such as four top quarks. It is arguably the best-motivated channel for early LHC discovery. A particular example is generic string theories compactified to four dimensions with stabilised moduli which typically have multi-TeV squarks and lighter gluinos (below a TeV) with a large pair production rate and large branching ratios to four tops. We update and sharpen the analysis 4-top signals and background to 7 TeV LHC energy. For 1 fb-1 integrated luminosity, gluinos up to about 650 GeV in mass can be detected, with larger masses accessible for higher luminosities or at higher energies. More than one signature is likely to be accessible, with one charged lepton plus two or more b-jets, and/or same-sign dileptons plus b-jets being the best channels. A non-Standard Model signal from counting is robust, and provides information on the gluino mass, cross section, and spin.

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