Direct Top Squark Pair Production Research Articles

Search for top squarks in events with a Higgs or Z boson using 139\xa0fb^{-1} of pp collision data at sqrt{s}=13\xa0TeV with the ATLAS detector

This paper presents a search for direct top squark pair production in events with missing transverse momentum plus either a pair of jets consistent with Standard Model Higgs boson decay into b-quarks or a same-flavour opposite-sign dilepton pair with an invariant mass consistent with a Z boson. The analysis is performed using the proton–proton collision data at sqrt{s}=13 TeV collected with the ATLAS detector during the LHC Run-2, corresponding to an integrated luminosity of 139 fb^{-1}. No excess is observed in the data above the Standard Model predictions. The results are interpreted in simplified models featuring direct production of pairs of either the lighter top squark (tilde{t}_1) or the heavier top squark (tilde{t}_2), excluding at 95% confidence level tilde{t}_1 and tilde{t}_2 masses up to about 1220 and 875 GeV, respectively.

Search for direct top squark pair production in events with one lepton, jets, and missing transverse momentum at 13 TeV with the CMS experiment

A search for direct top squark pair production is presented. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV recorded by the CMS experiment at the LHC during 2016, 2017, and 2018, corresponding to an integrated luminosity of 137 fb−1. The search is carried out using events with a single isolated electron or muon, multiple jets, and large transverse momentum imbalance. The observed data are consistent with the expectations from standard model processes. Exclusions are set in the context of simplified top squark pair production models. Depending on the model, exclusion limits at 95% confidence level for top squark masses up to 1.2 TeV are set for a massless lightest supersymmetric particle, assumed to be the neutralino. For models with top squark masses of 1 TeV, neutralino masses up to 600 GeV are excluded.

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

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

Search for supersymmetry in proton-proton collisions at 13 TeV using identified top quarks

A search for supersymmetry is presented based on proton-proton collision events containing identified hadronically decaying top quarks, no leptons, and an imbalance $p_\mathrm{T}^\text{miss}$ in transverse momentum. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb$^{-1}$. Search regions are defined in terms of the multiplicity of bottom quark jet and top quark candidates, the $p_\mathrm{T}^\text{miss}$, the scalar sum of jet transverse momenta, and the $m_{\mathrm{T2}}$ mass variable. No statistically significant excess of events is observed relative to the expectation from the standard model. Lower limits on the masses of supersymmetric particles are determined at 95% confidence level in the context of simplified models with top quark production. For a model with direct top squark pair production followed by the decay of each top squark to a top quark and a neutralino, top squark masses up to 1020 GeV and neutralino masses up to 430 GeV are excluded. For a model with pair production of gluinos followed by the decay of each gluino to a top quark-antiquark pair and a neutralino, gluino masses up to 2040 GeV and neutralino masses up to 1150 GeV are excluded. These limits extend previous results.

Searches for direct pair production of third generation squarks with the ATLAS detector

Naturalness arguments for weak-scale supersymmetry favour supersymmetric partners of the third generation quarks with masses not too far from those of their Standard Model counterparts. Top or bottom squarks with masses less than or around one TeV can also give rise to direct pair production rates at the Large Hadron Collider (LHC) that can be observed in the data sample recorded by the ATLAS detector. This document presents recent ATLAS results from searches for direct top and bottom squark pair production considering both R-parity conserving and R-parity violating scenarios, using the data collected during the LHC Run 2 at a centre-of-mass energy of √s = 13 TeV.

Search for direct top squark pair production in final states with two leptons in sqrt{s} = 13 TeV pp collisions with the ATLAS detector

The results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using 36.1~hbox {fb}^{-1} of integrated luminosity from proton–proton collisions at sqrt{s}=13 TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark tilde{t} and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay tilde{t} rightarrow b tilde{chi }_{1}^{pm } into a b-quark and the lightest chargino with tilde{chi }_{1}^{pm } rightarrow W tilde{chi }_{1}^{0}, the decay tilde{t} rightarrow t tilde{chi }_{1}^{0} into an on-shell top quark and the lightest neutralino, the three-body decay tilde{t} rightarrow b W tilde{chi }_{1}^{0} and the four-body decay tilde{t} rightarrow b ell nu tilde{chi }_{1}^{0}. No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the tilde{t} and tilde{chi }_{1}^{0} masses. The results exclude at 95% confidence level tilde{t} masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches.

Search for direct production of supersymmetric partners of the top quark in the all-jets final state in proton-proton collisions at sqrt{s}=13 TeV

A search for direct production of top squark pairs in events with jets and large transverse momentum imbalance is presented. The data are based on proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector in 2016 at the CERN LHC, and correspond to an integrated luminosity of 35.9 fb−1. The search considers a variety of R-parity conserving supersymmetric models, including ones for which the top squark and neutralino masses are nearly degenerate. Specialized jet reconstruction tools are developed to exploit the unique characteristics of the signal topologies. With no significant excess of events observed above the standard model expectations, upper limits are set on the direct top squark pair production cross section in the context of simplified supersymmetric models for various decay hypotheses. Models with larger differences in mass between the top squark and neutralino are probed for masses up to 1040 and 500 GeV, respectively, whereas models with a more compressed mass hierarchy are probed up to 660 and 610 GeV, respectively. The smallest mass difference probed is for masses near to 550 and 540 GeV, respectively.

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

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 sqrt{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 ( {tilde{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 ( {tilde{t}}_2 ) decaying via {tilde{t}}_2to Z{tilde{t}}_1 or {tilde{t}}_2to h{tilde{t}}_1 . The results exclude at 95% confidence level {tilde{t}}_2 and {tilde{t}}_1 masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.

Search for supersymmetry with extremely compressed spectra with the ATLAS and CMS detectors

Results of searches for supersymmetry via direct production of third-generation squarks and gluinos are reported. The analysis use 20.3 fb−1 of proton-proton collision data recorded by the ATLAS experiment and 19.5 fb−1 recorded by the CMS experiment at a centre-of-mass energy of s=8 TeV. Different signal regions based on monojet-like and c-tagged event selections optimize the sensitivity for direct top squark pair production with small mass differences between the hypothetical supersymmetric particles. In an complementary approach, the heavier top squark is searched for under the assumption that a Z boson is emitted in its decay to the lighter top squark. This strategy retains sensitivity for mass configurations where signals of direct production of the lighter top squark are hard to distinguish from the top quark pair production background. For the case of the gluino, a soft lepton analysis improves sensitivity for small mass differences between the gluino and the lightest neutralino. No significant excess above the Standard Model background expectation is observed in any of the analyses. The resulting limits significantly extend previous results at colliders.

Search for direct top squark pair production in final states with two tau leptons in pp collisions at [Formula: see text]TeV with the ATLAS detector.

A search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb^{-1} of proton–proton collision data at sqrt{s}=8~mathrm{TeV}. The data were collected by the ATLAS experiment at the LHC in 2012. Top squark candidates are searched for in events with either two hadronically decaying tau leptons, one hadronically decaying tau and one light lepton, or two light leptons. No significant excess over the Standard Model expectation is found. Exclusion limits at 95~% confidence level are set as a function of the top squark and scalar tau masses. Depending on the scalar tau mass, ranging from the 87~mathrm{GeV} LEP limit to the top squark mass, lower limits between 490 and 650~mathrm{GeV} are placed on the top squark mass within the model considered.

Search for pair-produced third-generation squarks decaying via charm quarks or in compressed supersymmetric scenarios inppcollisions ats=8 TeVwith the ATLAS detector

Results of a search for supersymmetry via direct production of third-generation squarks are reported, using $20.3$ fb$^{-1}$ of proton-proton collision data at $\sqrt{s} = 8$ TeV recorded by the ATLAS experiment at the LHC in 2012. Two different analysis strategies based on monojet-like and $c$-tagged event selections are carried out to optimize the sensitivity for direct top squark pair production in the decay channel to a charm quark and the lightest neutralino ($\tilde{t}_1 \to c + \tilde{\chi}_{1}^{0}$) across the top squark--neutralino mass parameter space. No excess above the Standard Model background expectation is observed. The results are interpreted in the context of direct pair production of top squarks and presented in terms of exclusion limits in the ($m_{\tilde{t}_1}$, $m_{\tilde{\chi}_{1}^{0}}$) parameter space. A top squark of mass up to about 240 GeV is excluded at 95$\%$ confidence level for arbitrary neutralino masses, within the kinematic boundaries. Top squark masses up to 270 GeV are excluded for a neutralino mass of 200 GeV. In a scenario where the top squark and the lightest neutralino are nearly degenerate in mass, top squark masses up to 260 GeV are excluded. The results from the monojet-like analysis are also interpreted in terms of compressed scenarios for top squark pair production in the decay channel $\tilde{t}_1 \to b + ff^{'} + \tilde{\chi}^{0}_{1}$ and sbottom pair production with $\tilde{b}_1 \to b + \tilde{\chi}^{0}_{1}$, leading to a similar exclusion for nearly mass-degenerate third-generation squarks and the lightest neutralino. The results in this paper significantly extend previous results at colliders.

Search for direct top squark pair production in events with a [Formula: see text] boson, [Formula: see text]-jets and missing transverse momentum in [Formula: see text] TeV [Formula: see text] collisions with the ATLAS detector.

A search is presented for direct top squark pair production using events with at least two leptons including a same-flavour opposite-sign pair with invariant mass consistent with the Z boson mass, jets tagged as originating from b-quarks and missing transverse momentum. The analysis is performed with proton–proton collision data at sqrt{s}=8{hbox { TeV}} collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20.3 fb^{-1}. No excess beyond the Standard Model expectation is observed. Interpretations of the results are provided in models based on the direct pair production of the heavier top squark state (tilde{t}_2) followed by the decay to the lighter top squark state (tilde{t}_1) via tilde{t}_2 rightarrow Ztilde{t}_1, and for tilde{t}_1 pair production in natural gauge-mediated supersymmetry breaking scenarios where the neutralino (tilde{chi }^0_1) is the next-to-lightest supersymmetric particle and decays producing a Z boson and a gravitino (tilde{G}) via the tilde{chi }^0_1 rightarrow Ztilde{G} process.

Search for direct top-squark pair production in final states with two leptons in pp collisions at $ \sqrt{s} $ = 8 TeV with the ATLAS detector

A search is presented for direct top-squark pair production in final states with two leptons (electrons or muons) of opposite charge using 20.3fb-1 of pp collision data at sqrt(s)=8TeV, collected by the ATLAS experiment at the Large Hadron Collider in 2012. No excess over the Standard Model expectation is found. The results are interpreted under the separate assumptions (i) that the top squark decays to a b-quark in addition to an on-shell chargino whose decay occurs via a real or virtual W boson, or (ii) that the top squark decays to a t-quark and the lightest neutralino. A top squark with a mass between 150 GeV and 445 GeV decaying to a b-quark and an on-shell chargino is excluded at 95% confidence level for a top squark mass equal to the chargino mass plus 10 GeV, in the case of a 1 GeV lightest neutralino. Top squarks with masses between 215 (90) GeV and 530 (170) GeV decaying to an on-shell (off-shell) t-quark and a neutralino are excluded at 95% confidence level for a 1 GeV neutralino.

Searches for direct stop production in events with two leptons in √s= 8 TeVppcollisions using 20 fb−1of ATLAS data

Three searches for direct top squark pair production are presented. They target different decay modes, each with two leptons (electrons or muons) in the final state. The searches use 20.3 fb−1 of pp collision data at √s = 8 TeV collected by the ATLAS experiment at the Large Hadron Collider. No excesses over Standard Model expectations are observed, and the results are interpreted under the separate assumptions that the light top squark decays to a b -quark and the lightest chargino, or to a t -quark and the lightest neutralino.

Search for direct top squark pair production in final states with one isolated lepton using 21 fb−1of data collected with the ATLAS detector

Naturalness arguments for weak-scale supersymmetry favour supersymmetric partners of the third generation quarks with masses not too far from those of their Stan- dard Model counterparts. Top or bottom scalar quarks (or squarks) with masses less than a few hundred GeV can give rise to direct pair production rates at the LHC that can be ob- served in the data sample recorded by the ATLAS detector. This proceeding summarises the latest results of a search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in √ s = 8 TeV pp collisions at the LHC, using 20. 7f b −1 of ATLAS data. Two top squark (˜) decay scenarios are considered: the decay to a top quark and a stable undetected neutral particle ( ˜ χ 0 ), and the decay to a bot- tom quark and a chargino, where the chargino decays via an on- or off-shell W boson to the ˜ χ 0 . The data are found to be consistent with Standard Model expectations and have been reinterpreted in terms of various SUSY scenarios.

Search for direct top squark pair production in final states with one electron or muon using 21 fb−1of ATLAS data

This article presents latest results of the search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in √ s = 8TeV pp collisions using L=21 fb −1 of data recorded with the ATLAS detector at the LHC. Two top squark decay scenarios are considered: (a) to a top quark and a long-lived undetected neutral particle (LSP), (b) to a bottom quark and a chargino, where the chargino decays via an on- or off-shell W boson to the LSP. The analysis also employs a new dedicated shape-fit method to target the challenging parameter region where m(˜ t) is close to the kinematic boundary m(t) +m(LSP).

Search for Direct Top Squark Pair Production in Final States with One Isolated Lepton, Jets, and Missing Transverse Momentum ins=7 TeVppCollisions Using4.7 fb−1of ATLAS Data

A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at sqrt[s] = 7 TeV. The measurement is based on 4.7 fb(-1) of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.