Squark and gluino production cross sections in $$pp$$ p p collisions at $$\sqrt{s} = 13, 14, 33$$ s = 13 , 14 , 33 and $$100$$ 100 TeV

A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three b-tagged jets is presented. The search uses 36.1 fb −1 of √ s = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits are extracted constraining four simplified models of R-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2 TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model tttt production of 60 fb (6.5 × the Standard Model prediction) at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields. Conclusion 25The ATLAS collaboration 34 IntroductionThe ATLAS experiment at the Large Hadron Collider (LHC) has carried out a large number of searches for beyond the Standard Model (BSM) physics. These searches cover a broad range of different final-state particles and kinematics. However, one gap in the search coverage, as pointed out in refs. [1,2], is in final states with one or more leptons, many jets and no-or-little missing transverse momentum (the magnitude of which is denoted by -1 - JHEP09(2017)088E miss T ). Such a search is presented in this article, considering final states with an isolated lepton (electron or muon), at least eight to twelve jets (depending on the jet transverse momentum threshold), either zero or many b-tagged jets, and with no requirement on E miss T . This search has potential sensitivity to a large number of BSM physics models. In this article, model-independent limits on the possible contribution of BSM physics to several single-bin signal regions are presented. In addition, four R-parity-violating (RPV) supersymmetric (SUSY [3-8]) benchmark models are used to interpret the results. In this case, a multi-bin fit to the two-dimensional space of jet-multiplicity and b-tagged jet multiplicity is used to constrain the models. The dominant Standard Model (SM) background arises from top-quark pair production and W/Z+jets production, with at least one lepton produced in the vector boson decay. The theoretical modelling of these backgrounds at high jet multiplicity suffers from large uncertainties, so they are estimated from the data by extrapolating the b-tagged jet multiplicity distribution extracted at moderate jet multiplicities to the high jet multiplicities of the search region. Previous searches targeting similar RPV SUSY models have been carried out by the ATLAS and CMS collabo...

Section: Jhep09(2017)088mentioning

confidence: 99%

Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using s = 13 $$ \sqrt{s}=13 $$ TeV proton-proton collision data

Aaboud¹,

Aad²,

Abbott³

et al. 2017

“…The nominal cross-section and the uncertainty are based on predictions using different PDF sets and factorisation and renormalisation scales, as described in ref. [67].…”

Section: Jhep08(2017)006mentioning

confidence: 99%

Search for direct top squark pair production in events with a Higgs or Z boson, and missing transverse momentum in s = 13 $$ \sqrt{s}=13 $$ TeV pp collisions with the ATLAS detector

Aaboud¹,

Aad²,

Abbott³

et al. 2017

A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a Z boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (h) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from b-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at √ s = 13 TeV collected with the ATLAS detector at the LHC in 2015-2016, corresponding to an integrated luminosity of 36.1 fb −1 . No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks (t 1 ) with long decay chains involving Z or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs (t 2 ) decaying viat 2 → Zt 1 ort 2 → ht 1 . The results exclude at 95% confidence levelt 2 andt 1 masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.

“…We also consider the case where a jet is replaced by heavy flavor quark. In each figure we show the current limit on the pair-production cross section times BR 2 , normalized to the NLO+NLL cross section of a scalar colored triplet taken from [20][21][22]. Presented this way, when a single mode dominates the decay (namely BR = 1), the y axis corresponds to the number of copies of the X representation that are experimentally allowed.…”

Section: Jhep02(2017)104mentioning

confidence: 99%

“…(These searches are more effective for gluinos, which have a significantly higher cross section [22]. )…”

Section: Jhep02(2017)104mentioning

confidence: 99%

Exotic colored scalars at the LHC

Blum

Efrati

Frugiuele

et al. 2017

Abstract:We study the phenomenology of exotic color-triplet scalar particles X with charge |Q| = 2/3, 4/3, 5/3, 7/3, 8/3 and 10/3. If X is an SU(2) W -non-singlet, mass splitting within the multiplet allows for cascade decays of the members into the lightest state. We study examples where the lightest state, in turn, decays into a three-body W ± jj final state, and show that in such case the entire multiplet is compatible with indirect precision tests and with direct collider searches for continuum pair production of X down to m X ∼ 250 GeV. However, bound states S, made of XX † pairs at m S ≈ 2m X , form under rather generic conditions and their decay to diphoton can be the first discovery channel of the model. Furthermore, for SU(2) W -non-singlets, the mode S → W + W − may be observable and the width of S → γγ and S → jj may appear large as a consequence of mass splittings within the X-multiplet. As an example we study in detail the case of an SU(2) W -quartet, finding that m X 450 GeV is allowed by all current searches.