Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at $\sqrt{s}=8$ TeV with the ATLAS detector
The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of $20.1 \rm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s}=8$ TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via $\tilde{t} \rightarrow t \tildeχ_{1}^{0}$ or $\tilde{t}\rightarrow b\tildeχ_{1}^{\pm} \rightarrow b W^{\left(\ast\right)} \tildeχ_{1}^{0}$, where $\tildeχ_{1}^{0}$ ($\tildeχ_{1}^{\pm}$) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of $\tilde{t} \rightarrow t \tildeχ_{1}^{0}$. For a branching fraction of 100%, top squark masses in the range 270-645 GeV are excluded for $\tildeχ_{1}^{0}$ masses below 30 GeV. For a branching fraction of 50% to either $\tilde{t} \rightarrow t \tildeχ_{1}^{0}$ or $\tilde{t}\rightarrow b\tildeχ_{1}^{\pm}$, and assuming the $\tildeχ_{1}^{\pm}$ mass to be twice the $\tildeχ_{1}^{0}$ mass, top squark masses in the range 250-550 GeV are excluded for $\tildeχ_{1}^{0}$ masses below 60 GeV.
Weak scale supersymmetry is one of the best motivated and studied Standard Model extensions. It predicts the existence of new heavy coloured particles called squarks and gluinos which are the supersymmetric partners of the quarks and gluons, respectively. The poster summarises results on inclusive searches for supersymmetric squarks and gluinos in events containing jets and missing transverse momentum without leptons. The searches use the full data sample recorded in 2012 at $\sqrt{s}$=8~TeV centre-of-mass energy by the ATLAS experiment at the LHC.
A search for squarks and gluinos in final states containing jets, missing transverse momentum and no high-pT electrons or muons is presented. The data represent the complete sample recorded in 2011 by the ATLAS experiment in 7 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 4.7 fb^-1. No excess above the Standard Model background expectation is observed. Gluino masses below 860 GeV and squark masses below 1320 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet an…
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 m…
This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb^-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded.
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 sqrt(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 increase…
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 exc…
A search for the pair production of top squarks, each with R-parity-violating decays into two Standard Model quarks, is performed using 17.4 fb$^{-1}$ of $\sqrt{s}$ = 8 TeV proton-proton collision data recorded by the ATLAS experiment at the LHC. Each top squark is assumed to decay to a b- and an s-quark, leading to four quarks in the final state. Background discrimination is achieved with the use of b-tagging and selections on the mass and substructure of large-radius jets, providing sensitivity to top squark masses as low as 100 GeV. No evidence of an excess beyond the Standard Model backgro…
The results of a search for pair production of light top squarks are presented, using 4.7 fb^-1 of sqrt(s) = 7 TeV proton-proton collisions collected with the ATLAS detector at the Large Hadron Collider. This search targets top squarks with masses similar to, or lighter than, the top quark mass. Final states containing exclusively one or two leptons (e, mu), large missing transverse momentum, light-jets and b-jets are used to reconstruct the top squark pair system. Global mass scale variables are used to separate the signal from a large ttbar background. No excess over the Standard Model expec…
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 $\sqrt{s}=8$ 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 fun…
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 …
The results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton--proton collision data at a center-of-mass energy of $\sqrt{s}$ = 13 TeV are presented. The dataset used was recorded during 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 $fb^{-1}$. No significant excess beyond the expected background is found. Exclusion limits at 95% confidence level are set in a number of supersymmetric scenarios, reaching masses up to 2.1 Te…
A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded in 2015 and 2016 by the ATLAS experiment in $\sqrt{s}$=13 TeV proton--proton collisions at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb$^{-1}$. The results are interpreted in the context of various models where squarks and gluinos are pair-produced and the neutralino is the lightest supersymmetric particle. An exclusion l…
A search for squarks and gluinos in final states containing hadronic jets, missing transverse momentum but no electrons or muons is presented. The data were recorded in 2015 by the ATLAS experiment in $\sqrt{s}=$ 13 TeV proton--proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 3.2 fb$^{-1}$ of analyzed data. Results are interpreted within simplified models that assume R-parity is conserved and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is…
A search for squarks and gluinos in final states containing high-$p_{\rm T}$ jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in $\sqrt{s}=8$ TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of $20.3 \mathrm{fb}^{-1}$. No significant excess above the Standard Model expectation is observed. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest super…
A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb$^{-1}$. The results are interpreted in the context of various $R$-parity-conserving models where squarks and gluinos are produced in pairs or in association and a neutral…
Despite the absence of experimental evidence, weak scale supersymmetry remains one of the best motivated and studied Standard Model extensions. This report summarises recent ATLAS results on inclusive searches for supersymmetric squarks and gluinos, including third generation squarks produced in the decay of gluinos. Results are presented for both R-parity conserving and R-parity violating scenarios, with final states containing jets with and without missing transverse momentum, light leptons, taus or photons.
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 interprete…
A search for supersymmetric partners of gluons and quarks is presented, involving signatures with jets and either two isolated leptons (electrons or muons) with the same electric charge, or at least three isolated leptons. A data sample of proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to a total integrated luminosity of 139 fb$^{-1}$, is used for the search. No significant excess over the Standard Model expectation is observed. The results are interpreted in simplified supersymmetric models fea…
The results of a search for gluino and squark pair production with the pairs decaying via the lightest charginos into a final state consisting of two $W$ bosons, the lightest neutralinos ($\tildeχ^0_1$), and quarks, are presented. The signal is characterised by the presence of a single charged lepton ($e^{\pm}$ or $μ^{\pm}$) from a $W$ boson decay, jets, and missing transverse momentum. The analysis is performed using 139 fb$^{-1}$ of proton-proton collision data taken at a centre-of-mass energy $\sqrt{s}=13$ TeV delivered by the Large Hadron Collider and recorded by the ATLAS experiment. No s…
These proceedings summarize the results of four analyses which searched for squarks and gluinos in hadronic final states with missing transverse momentum in 2.3 fb$^{-1}$ of data in proton-proton collisions at $\sqrt{s}=13$ TeV collected in the year 2015 with the CMS detector at the CERN LHC. Each analysis is characterized by a different kinematic variable that is sensitive to the presence of invisible particles, e.g., $M_\text{T2}$, $α_{\text{T}}$, and razor variables. We observed no significant deviation from the standard model prediction and placed limits on the production cross sections an…
The results of a search for pair production of supersymmetric partners of the Standard Model third-generation quarks are reported. This search uses 20.1 fb-1 of pp collisions at sqrt{s}=8 TeV collected by the ATLAS experiment at the Large Hadron Collider. The lightest bottom and top squarks (b1 and t1 respectively) are searched for in a final state with large missing transverse momentum and two jets identified as originating from b-quarks. No excess of events above the expected level of Standard Model background is found. The results are used to set upper limits on the visible cross section fo…
Searches for third-generation squarks in fully hadronic final states are presented using data samples corresponding to integrated luminosities of 19.4 or 19.7 inverse femtobarns, collected at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. Three mutually exclusive searches are presented, each optimized for a different decay topology. They include a multijet search requiring one fully reconstructed top quark, a dijet search requiring one or two jets originating from b quarks, and a monojet search. No excesses above the standard model expectations are seen, and limits are set …
The result of a search for pair production of the supersymmetric partner of the Standard Model bottom quark ($\tilde{b}_1$) is reported. The search uses 3.2 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}=$13 TeV collected by the ATLAS experiment at the Large Hadron Collider in 2015. Bottom squarks are searched for in events containing large missing transverse momentum and exactly two jets identified as originating from $b$-quarks. No excess above the expected Standard Model background yield is observed. Exclusion limits at 95% confidence level on the mass of the bottom squark are derived in phenome…
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 ($\tilde{t}_1 \to c + \tildeχ_{1}^{0}$) across the top squark--neutralino mass parameter space. No excess above the Standard Model b…
This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton-proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 fb$^{-1}$ of collisions at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV, although in some case an additional 4.7 fb$^{-1}$ of collision data at $\sqrt{s}$ = 7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion li…
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 $\sqrt{s}=8$ 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 dir…
A measurement of spin correlation in $t\bar{t}$ production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The correlation between the top and antitop quark spins is extracted from dilepton $t\bar{t}$ events by using the difference in azimuthal angle between the two charged leptons in the laboratory frame. In the helicity basis the measured degree of correlation corresponds to $A_{helicity} = 0.38 \pm 0.04$, in agreement with the S…
A search for direct pair production of top squarks in final states with two tau leptons, $b$-jets, and missing transverse momentum is presented. The analysis is based on proton-proton collision data at $\sqrt{s} = 13$ TeV corresponding to an integrated luminosity of 36.1 fb$^{-1}$ recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. Two exclusive channels with either two hadronically decaying tau leptons or one hadronically and one leptonically decaying tau lepton are considered. No significant deviation from the Standard Model predictions is observed in the data. Th…
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 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 $\tilde{t} \rightarrow b \tildeχ_{1}^{\pm}$ into a $b$-quark and the lightest chargino with …
The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of $20.1 \rm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s}=8$ TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via $\tilde{t} \rightarrow t \tildeχ_{1}^{0}$ or $\tilde{t}\rightarrow b\tildeχ_{1}^{\pm} \rightarrow b W^{\left(\ast\right)} \tildeχ_{1}^{0}$, where $\tildeχ_{1}^{0}$ ($\tildeχ_{1}^{\pm}$) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in e…
The results of a search for the direct pair production of top squarks, the supersymmetric partner of the top quark, in final states with one isolated electron or muon, several energetic jets, and missing transverse momentum are reported. The analysis also targets spin-0 mediator models, where the mediator decays into a pair of dark-matter particles and is produced in association with a pair of top quarks. The search uses data from proton-proton collisions delivered by the Large Hadron Collider in 2015 and 2016 at a centre-of-mass energy of $\sqrt{s}=13$ TeV and recorded by the ATLAS detector, …
A search for supersymmetric partners of quarks is performed in the topology of multijet events accompanied by at least one tau lepton decaying hadronically and large missing transverse energy. Approximately 1 fb-1 of ppbar collision data from the Fermilab Tevatron Collider at a center of mass energy of 1.96 TeV recorded by the D0 detector is analyzed. Results are combined with the previously published D0 inclusive search for squarks and gluinos. No evidence of physics beyond the standard model is found and lower limits on the squark mass up to 410 GeV are derived in the framework of minimal su…
A summary is presented of ATLAS searches for gluinos and first- and second-generation squarks in final states containing jets and missing transverse momentum, with or without leptons or b-jets, in the $\sqrt{s}$ = 8 TeV data set collected at the Large Hadron Collider in 2012. This paper reports the results of new interpretations and statistical combinations of previously published analyses, as well as a new analysis. Since no significant excess of events over the Standard Model expectation is observed, the data are used to set limits in a variety of models. In all the considered simplified mod…
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 (LHC) are reported. The search is based on proton-proton collision data at a centre-of-mass energy $\sqrt{s} = 8$ 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 the parameters of a minimal universal extra dimensions model, excluding a compactification radius of…
Hitherto unobserved long-lived massive particles with electric and/or colour charge are predicted by a range of theories which extend the Standard Model. In this paper a search is performed at the ATLAS experiment for slow-moving charged particles produced in proton-proton collisions at 7 TeV centre-of-mass energy at the LHC, using a data-set corresponding to an integrated luminosity of 34 pb-1. No deviations from Standard Model expectations are found. This result is interpreted in a framework of supersymmetry models in which coloured sparticles can hadronise into long-lived bound hadronic sta…
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 additional leptons, jets, jets identified as originating from $b$-quarks, and missing transverse momentum 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, corresp…
Search for pair production of squarks or gluinos decaying via sleptons or weak bosons in final states with two same-sign or three leptons with the ATLAS detector
We study the impact of the jets and missing transverse momentum SUSY analyses of the ATLAS experiment on the phenomenological MSSM (pMSSM). We investigate sets of SUSY models with a flat and logarithmic prior in the SUSY mass scale and a mass range up to 1 and 3 TeV, respectively. These models were found previously in the study 'Supersymmetry without Prejudice'. Removing models with long-lived SUSY particles, we show that 99% of 20000 randomly generated pMSSM model points with a flat prior and 87% for a logarithmic prior are excluded by the ATLAS results. For models with squarks and gluinos be…
A search for pair production of bottom squarks in events with hadronically decaying $τ$-leptons, $b$-tagged jets and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisions at $\sqrt{s}$ = 13 TeV delivered by the Large Hadron Collider and recorded by the ATLAS detector from 2015 to 2018, and corresponds to an integrated luminosity of 139 fb$^{-1}$. The observed data are compatible with the expected Standard Model background. Results are interpreted in a simplified model where each bottom squark is assumed to decay into the second-lightest neutr…
A search for production of the supersymmetric partners of the top quark, top squarks, is presented. The search is based on proton-proton collision events containing multiple jets, no leptons, and large transverse momentum imbalance. 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 137 fb$^{-1}$. The targeted signal production scenarios are direct and gluino-mediated top squark production, including scenarios in which the top squark and neutralino masses are nearly degenerate. The search utilizes no…
Search for direct pair production of top squarks in $pp$ collisions at $\sqrt{s}= 13$ TeV and $13.6$ TeV in events with two oppositely charged leptons using the ATLAS detector
EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究中心（CERN））
A search is presented for the direct pair production of the stop, the supersymmetric partner of the top quark, that decays through an $R$-parity-violating coupling to a final state with two leptons and two jets, at least one of which is identified as a $b$-jet. The dataset corresponds to an integrated luminosity of 36.1 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of $\sqrt{s} = 13$ TeV, collected in 2015 and 2016 by the ATLAS detector at the LHC. No significant excess is observed over the Standard Model background, and exclusion limits are set on stop pair production at a …
Using the ATLAS 4.7 $fb^{-1}$ data on new physics search in the jets + $\met$ channel, we obtain new limits on the lighter top squark ($\tilde t_1$) considering all its decay modes assuming that it is the next to lightest supersymmetric particle (NLSP). If the decay $\lstop$ $\ra c \lspone$ dominates and the production of dark matter relic density is due to NLSP - LSP co-annihilation then the lower limit on $\mlstop $ is 240 GeV. The limit changes to 200 GeV if the decay $\lstop$ $\ra b W \lspone$ dominates. Combining these results it follows that $\lstop $ NLSP induced baryogenesis is now con…
A search for supersymmetric particles in final states with zero, one, and two leptons, with and without jets identified as originating from b-quarks, in 4.7 fb-1 of sqrt(s)=7 TeV pp collisions produced by the Large Hadron Collider and recorded by the ATLAS detector is presented. The search uses a set of variables carrying information on the event kinematics transverse and parallel to the beam line that are sensitive to several topologies expected in supersymmetry. Mutually exclusive final states are defined, allowing a combination of all channels to increase the search sensitivity. No deviatio…
The result of a search for the pair production of the lightest supersymmetric partner of the bottom quark ($\tilde{b}_{1}$) using 139 fb$^{-1}$ of proton-proton data collected at $\sqrt{s} = 13$ TeV by the ATLAS detector is reported. In the supersymmetric scenarios considered both of the bottom-squarks decay into a $b$-quark and the second-lightest neutralino, $\tilde{b}_{1} \rightarrow b + \tildeχ^{0}_{2}$. Each $\tildeχ^{0}_{2}$ is assumed to subsequently decay with 100% branching ratio into a Higgs boson ($h$) like the one in the Standard Model and the lightest neutralino: $\tildeχ^{0}_{2} …
The results of a search for new phenomena in final states with $b$-jets and missing transverse momentum using 139 fb$^{-1}$ of proton-proton data collected at a centre-of-mass energy $\sqrt{s} = 13$ TeV by the ATLAS detector at the LHC are reported. The analysis targets final states produced by the decay of a pair-produced supersymmetric bottom squark into a bottom quark and a stable neutralino. The analysis also seeks evidence for models of pair production of dark matter particles produced through the decay of a generic scalar or pseudoscalar mediator state in association with a pair of botto…
An updated search is performed for gluino, top squark, or bottom squark R-hadrons that have come to rest within the ATLAS calorimeter, and decay at some later time to hadronic jets and a neutralino, using 5.0 and 22.9 fb-1 of pp collisions at 7 and 8 TeV, respectively. Candidate decay events are triggered in selected empty bunch crossings of the LHC in order to remove pp collision backgrounds. Selections based on jet shape and muon-system activity are applied to discriminate signal events from cosmic ray and beam-halo muon backgrounds. In the absence of an excess of events, improved limits are…
Search for top squark pair production in a final state with at least one hadronically decaying tau lepton in proton-proton collisions at $\sqrt{s}$ = 13 TeV
A search for top-squark pair production, in final states containing a top quark, a charm quark and missing transverse momentum, using the 139 fb$^{-1}$ of $pp$ collision data collected by the ATLAS detector
A search for pair production of a scalar partner of the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of 36.1 fb$^{-1}$ of $\sqrt{s}$=13 TeV proton-proton collisions collected using the ATLAS detector at the LHC yields no significant excess over the expected Standard Model background. To interpret the results a simplified supersymmetric model is used where the top squark is assumed to decay via $\tilde{t}_1 \rightarrow t^{(*)} \tildeχ^0_1$ and $\tilde{t}_1\rightarrow b\tildeχ^\pm_1 \rightarrow b W^{(*)} \tildeχ^0_1$, where $\tildeχ^0_1$ (…
The results of a search for direct pair production of top squarks and for dark matter in events with two opposite-charge leptons (electrons or muons), jets and missing transverse momentum are reported, using 139 fb$^{-1}$ of integrated luminosity from proton-proton collisions at $\sqrt{s} = 13$ TeV, collected by the ATLAS detector at the Large Hadron Collider during Run 2 (2015-2018). This search considers the pair production of top squarks and is sensitive across a wide range of mass differences between the top squark and the lightest neutralino. Additionally, spin-0 mediator dark-matter mode…
We calculate the rates for inclusive hadronic decay of the three $χ_{bJ}$ states into a pair of light bottom squarks as a function of the masses of the bottom squark and the gluino. We include color-singlet and color-octet configurations. The color-octet contribution is found to be insignificant for the $χ_{b0}$ but can dominate in the $χ_{b2}$ case if current lattice estimates are used for the color-octet matrix element. In comparison with the standard model values, bottom squark decays can increase the predicted hadronic width of the $χ_{b0}$ by as much as 35%, for very small bottom squark m…
A search for direct pair production of scalar partners of the top quark (top squarks or scalar third-generation up-type leptoquarks) in the all-hadronic $t\bar{t}$ plus missing transverse momentum final state is presented. The analysis of 139 fb$^{-1}$ of ${\sqrt{s}=13}$ TeV proton-proton collision data collected using the ATLAS detector at the LHC yields no significant excess over the Standard Model background expectation. To interpret the results, a supersymmetric model is used where the top squark decays via $\tilde{t} \to t^{(*)} \tildeχ^0_1$, with $t^{(*)}$ denoting an on-shell (off-shell…
Search for squarks and gluinos in $pp$ collisions at $\sqrt{s} = 13$ TeV and $13.6$ TeV in events with $τ$-leptons, jets and missing transverse momentum using the ATLAS detector
EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究中心（CERN））
利用 ATLAS 探测器在 13 TeV 和 13.6 TeV 撞击数据中，研究 squarks 和 gluinos 的产生，排除了部分高质子质量范围。
The presence of tau leptons in the final state is an important signature in many Higgs boson and SUSY searches. With the ATLAS detector, hadronically decaying tau leptons can be reconstructed in a wide range of transverse energies. The reconstruction algorithm for hadronically decaying tau leptons is explained and the performance of tau lepton identification is shown. Particularly important is the discrimination of hadronically decaying tau leptons against overwhelming backgrounds from QCD jets.
Hadronically decaying tau leptons are of prime importance in numerous physics analyses in ATLAS. The spectrum of the possible applications of hadronically decaying tau leptons reaches from Standard Model measurements, including Higgs searches, to searches for physics beyond the Standard Model. The basic principles behind the sophisticated tau reconstruction and identification techniques, which are specifically designed to identify hadronically decaying taus and reject various background processes, are delineated here along with current data-driven estimates of their respective performance.
Recent results on searches for third generation supersymmetry carried out by the ATLAS collaboration with 2.05 fb-1 of sqrt(s) = 7 TeV pp collisions recorded with the LHC in 2011 are reported. These analyses focus on search for gluino- and squark-mediated stau production, direct scalar bottom pair production and gluino-mediated sbottom and stop pair production.
Recent results from the proton-proton collision data taken by the ATLAS experiment on exotic resonances are presented. A search for $J/ψp$ resonances in $Λ_{b}\rightarrow J/ψp K$ decays with large $p K$ invariant masses is reported. A search for exotic resonances in the four-muon final state is shown.
