Simplified models for LHC new physics searches

117

172

Relatively light Top Partners are unmistakable signatures of reasonably Natural Composite Higgs models and as such they are worth searching for at the LHC. Their phenomenology is characterized by a certain amount of model-dependence, which makes the interpretation of Top Partner experimental searches not completely straightforward especially if one is willing to take also single production into account. We describe a modelindependent strategy by which the interpretation is provided on the parameter space of a Simplified Model that captures the relevant features of all the explicit constructions. The Simplified Model limits are easy to interpret within explicit models, in a way that requires no recasting and no knowledge of the experimental details of the analyses.We illustrate the method by concrete examples, among which the searches for a charge 5/3 Partner in same-sign dileptons and the searches for a charge 2/3 singlet. In each case we perform a theory recasting of the available 8 TeV Run-1 results and an estimate of the 13 TeV Run-2 reach, also including the effect of single production for which dedicated experimental analyses are not yet available. A rough assessment of the reach of a hypothetical 100 TeV collider is also provided.

Section: Jhep12(2014)097mentioning

confidence: 99%

On the interpretation of Top Partners searches

Matsedonskyi

Panico

Wulzer

2014

117

172

“…Simplified models [27] have successfully been invoked by the LHC experiments to present the results of searches for new physics in a more model independent way, and to facilitate the interpretation of the results in different BSM scenarios. In this spirit, we will perform the majority of our analyses in the limiting cases where either µ M 1 , M 2 ∼ M Z , such that only the electroweak gauginos are present at the weak scale, or where M 1 , M 2 µ ∼ M Z , such that only Higgsinos are light.…”

Section: Phenomenology and Limits On Electroweakinosmentioning

confidence: 99%

Compressed electroweakino spectra at the LHC

Schwaller

Zurita

2014

Self Cite

138

146

In this work, we examine the sensitivity of monojet searches at the LHC to directly produced charginos and neutralinos (electroweakinos) in the limit of small mass splitting, where the traditional multilepton plus missing energy searches loose their sensitivity. We first recast the existing 8 TeV monojet search at CMS in terms of a SUSY simplified model with only light gauginos (winos and binos) or only light Higgsinos. The current searches are not sensitive to MSSM-like production cross sections, but would be sensitive to models with 2-20 times enhanced production cross section, for particle masses between 100 GeV and 250 GeV. Then we explore the sensitivity in the 14 TeV run of the LHC. Here we emphasise that in addition to the pure monojet search, soft leptons present in the samples can be used to increase the sensitivity. Exclusion of electroweakino masses up to 200 GeV is possible with 300 fb −1 at the LHC, if the systematic error can be reduced to the 1% level. Discovery is possible with 3000 fb −1 in some regions of parameter space.

“…The signal models considered cover simplified [26,27] and phenomenological SUSY models, as well as a minimal Universal Extra Dimension (mUED) scenario [28,29]. Some of these models were also probed by other ATLAS searches based on the 8 TeV pp dataset, using different final-state selections [30][31][32][33][34].…”

Section: Signal Event Samplesmentioning

confidence: 99%

Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s = 8 $$ \sqrt{s}=8 $$ TeV with the ATLAS detector

Aad¹,

Kupčo²,

Davison³

et al. 2015

Abstract:The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy √ s = 8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb −1 . No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c ) of approximately 30. Keywords: Hadron-Hadron Scattering JHEP04(2015)116The ATLAS collaboration 58 IntroductionSupersymmetry (SUSY) [1][2][3][4][5][6][7][8][9] postulates the existence of particles (sparticles) which differ by half a unit of spin from their Standard Model (SM) partners. The squarks (q L andq R ) and sleptons (˜ L and˜ R ) are the scalar partners of the left-handed and right-handed quarks and leptons, the gluinos (g) are the fermionic partners of the gluons, and the charginos (χ ± i with i = 1, 2) and neutralinos (χ 0 i with i = 1, 2, 3, 4) are the mass eigenstates (ordered from the lightest to the heaviest) formed from the linear superpositions of the SUSY partners of the Higgs and electroweak gauge bosons. An attractive feature of SUSY is that it can solve the SM hierarchy problem [10][11][12][13][14][15] if the gluino, higgsino and top squark masses are not much higher than the TeV scale.If strongly interacting sparticles exist at the TeV scale, they should be accessible at the Large Hadron Collider (LHC). In the minimal supersymmetric extension of the SM such particles decay into jets, possibly leptons, and the lightest sparticle (LSP). If the LSP is stable owing to R-parity conservation [15][16][17][18][19] and only weakly interacting, it escapes detection, leading to missing transverse momentum (p miss T and its magnitude E miss T ) in the final state. In this scenario, the LSP can be a dark-matter candidate. Significant E miss T can also arise in R-parity-violating scenarios in which the LSP decays to final states containing neutrinos or in scenarios where neutrinos are present in the cascade decay chains of the produced sparticles.This paper presents a search with the ATLAS detector [20,21] for SUSY in final states containing jets, at least one isolated lepton (electron or muon) and large E miss T . Different search channels are used in order to cover a broad parameter space: the events are selected by different requirements on the transverse momentum (p T ) of the leptons, either using low-p T leptons (referred to as the "soft" lepton selection), or high-p T leptons (referred to as the "hard" lepton selection). Each of these categories is further subdivided i...