Search For Direct Pair Production Research Articles

Search for direct pair production of sleptons and charginos decaying to two leptons and neutralinos with mass splittings near the W-boson mass in sqrt{s} = 13 TeV pp collisions with the ATLAS detector

A search for the electroweak production of pairs of charged sleptons or charginos decaying into two-lepton final states with missing transverse momentum is presented. Two simplified models of R-parity-conserving supersymmetry are considered: direct pair-production of sleptons left(overset{sim }{ell}overset{sim }{ell}right) , with each decaying into a charged lepton and a {overset{sim }{chi}}_1^0 neutralino, and direct pair-production of the lightest charginos left({overset{sim }{chi}}_1^{pm }{overset{sim }{chi}}_1^{mp}right) , with each decaying into a W-boson and a {overset{sim }{chi}}_1^0 . The lightest neutralino left({overset{sim }{chi}}_1^0right) is assumed to be the lightest supersymmetric particle (LSP). The analyses target the experimentally challenging mass regions where mleft(overset{sim }{ell}right)-mleft({overset{sim }{chi}}_1^0right) and mleft({overset{sim }{chi}}_1^{pm}right)-mleft({overset{sim }{chi}}_1^0right) are close to the W-boson mass (‘moderately compressed’ regions). The search uses 139 fb−1 of sqrt{s} = 13 TeV proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider. No significant excesses over the expected background are observed. Exclusion limits on the simplified models under study are reported in the left(overset{sim }{ell },{overset{sim }{chi}}_1^0right) and left({overset{sim }{chi}}_1^{pm }{overset{sim }{chi}}_1^0right) mass planes at 95% confidence level (CL). Sleptons with masses up to 150 GeV are excluded at 95% CL for the case of a mass-splitting between sleptons and the LSP of 50 GeV. Chargino masses up to 140 GeV are excluded at 95% CL for the case of a mass-splitting between the chargino and the LSP down to about 100 GeV.

Search for new phenomena in events with two opposite-charge leptons, jets and missing transverse momentum in pp collisions at sqrt{mathrm{s}} = 13 TeV with the ATLAS detector

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 models are considered, in which the mediator is produced in association with a pair of top quarks. The mediator subsequently decays to a pair of dark-matter particles. No significant excess of events is observed above the Standard Model background, and limits are set at 95% confidence level. The results exclude top squark masses up to about 1 TeV, and masses of the lightest neutralino up to about 500 GeV. Limits on dark-matter production are set for scalar (pseudoscalar) mediator masses up to about 250 (300) GeV.

Search for a scalar partner of the top quark in the all-hadronic t{bar{t}} plus missing transverse momentum final state at sqrt{s}=13\xa0TeV with the ATLAS detector

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 hbox {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}} rightarrow t^{(*)} {tilde{chi }}^0_1, with t^{(*)} denoting an on-shell (off-shell) top quark and {tilde{chi }}^0_1 the lightest neutralino. Three specific event selections are optimised for the following scenarios. In the scenario where m_{{tilde{t}}}> m_t+m_{{tilde{chi }}^0_1}, top squark masses are excluded in the range 400–1250 GeV for {tilde{chi }}^0_1 masses below 200 GeV at 95% confidence level. In the situation where m_{{tilde{t}}}sim m_t+m_{{tilde{chi }}^0_1}, top squark masses in the range 300–630 GeV are excluded, while in the case where m_{{tilde{t}}}< m_W+m_b+m_{{tilde{chi }}^0_1} (with m_{{tilde{t}}}-m_{{tilde{chi }}^0_1}ge 5 GeV), considered for the first time in an ATLAS all-hadronic search, top squark masses in the range 300–660 GeV are excluded. Limits are also set for scalar third-generation up-type leptoquarks, excluding leptoquarks with masses below 1240 GeV when considering only leptoquark decays into a top quark and a neutrino.

Search for top squarks decaying to tau sleptons in pp collisions at s=13 TeV with the ATLAS detector

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. The analysis results are interpreted in terms of model-independent limits and used to derive exclusion limits on the masses of the top squark $\tilde t_1$ and the tau slepton $\tilde \tau_1$ in a simplified model of supersymmetry with a nearly massless gravitino. In this model, masses up to $m(\tilde t_1) = 1.16$ TeV and $m(\tilde \tau_1) = 1.00$ TeV are excluded at 95% confidence level.

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.

Searches for Direct Pair Production of Third Generation Squarks with the ATLAS Detector

This document summarises recent ATLAS results for searches for third generation squarks using 36.1 [Formula: see text] of LHC proton-proton collision data collected at [Formula: see text] TeV. Despite the absence of experimental evidence, weak scale supersymmetry remains one of the best motivated and studied Standard Model extensions. Supersymmetry can naturally solve the Standard Model hierarchy problem by preventing a large fine-tuning in the Higgs sector: a typical natural SUSY spectrum contains light third generation squarks (stops and sbottoms). Both R-Parity conserving and R-Parity violating scenarios are considered. The searches involve final states including jets, missing transverse momentum, electrons or muons. Simplified models predicting pair production of third generation squarks have been excluded at 95% CL up to about one TeV in the most favourable scenarios.

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.

Erratum to: Search for direct pair production of scalar top quarks in the single- and dilepton channels in proton-proton collisions at s = 8 $$ \sqrt{s}=8 $$ TeV

Citation: The, C. M. S. c., Khachatryan, V., Sirunyan, A. M., Tumasyan, A., Adam, W., Asilar, E., . . . Woods, N. (2016). Erratum to: Search for direct pair production of scalar top quarks in the single- and dilepton channels in proton-proton collisions at ?s = 8 TeV (JHEP, (2016) 7, (027), 10.1007/JHEP07(2016)027). Journal of High Energy Physics, 2016(9). doi:10.1007/JHEP09(2016)056

Search for direct pair production of supersymmetric top quarks decaying to all-hadronic final states in pp collisions at [Formula: see text

Results are reported from a search for the pair production of top squarks, the supersymmetric partners of top quarks, in final states with jets and missing transverse momentum. The data sample used in this search was collected by the CMS detector and corresponds to an integrated luminosity of 18.9,text {fb}^text {-1} of proton-proton collisions at a centre-of-mass energy of 8;text {TeV} produced by the LHC. The search features novel background suppression and prediction methods, including a dedicated top quark pair reconstruction algorithm. The data are found to be in agreement with the predicted backgrounds. Exclusion limits are set in simplified supersymmetry models with the top squark decaying to jets and an undetected neutralino, either through a top quark or through a bottom quark and chargino. Models with the top squark decaying via a top quark are excluded for top squark masses up to 755;text {GeV} in the case of neutralino masses below 200;text {GeV}. For decays via a chargino, top squark masses up to 620;text {GeV} are excluded, depending on the masses of the chargino and neutralino.

Search for direct pair production of scalar top quarks in the single- and dilepton channels in proton-proton collisions at s = 8 $$ \sqrt{s}=8 $$ TeV

Results are reported from a search for the top squark, the lighter of the two supersymmetric partners of the top quark. The data sample corresponds to 19.7 inverse femtobarns of proton-proton collisions at sqrt(s) = 8 TeV collected with the CMS detector at the LHC. The search targets top squark to b chi+/- and top squark to t(*) chi0 decay modes, where chi+/- and chi0 are the lightest chargino and neutralino, respectively. The reconstructed final state consists of jets, b jets, missing transverse energy, and either one or two leptons. Leading backgrounds are determined from data. No significant excess in data is observed above the expectation from standard model processes. The results exclude a region of the two-dimensional plane of possible top squark and chi0 masses. The highest excluded top squark and chi0 masses are about 700 GeV and 250 GeV, respectively.

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 a few hundred GeV can also give rise to direct pair production rates at the LHC proton-proton collisions that can be observed in the data sample recorded by the ATLAS detector. The talk presents recent ATLAS results from searches for direct stop and sbottom pair production.

Erratum to: ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider ATLAS Collaboration

The online version of the original article can be found under doi:10.1140/epjc/s10052-015-3726-9

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.

ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider.

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 {mathrm{fb}^{-1}} of collisions at a centre-of-mass energy of sqrt{s} = 8 TeV, although in some case an additional 4.7 {mathrm{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 limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models.

Search for direct pair production of a chargino and a neutralino decaying to the 125GeV Higgs boson in [Formula: see text]TeV [Formula: see text] collisions with the ATLAS detector.

A search is presented for the direct pair production of a chargino and a neutralino pprightarrow tilde{chi }_1^pm tilde{chi }_2^0, where the chargino decays to the lightest neutralino and the W boson, tilde{chi }_1^pm rightarrow tilde{chi }_1^0(W^{pm }rightarrow ell ^{pm }nu ), while the neutralino decays to the lightest neutralino and the 125 GeV Higgs boson, tilde{chi }_2^0rightarrow tilde{chi }_1^0(hrightarrow bb/gamma gamma /ell ^{pm }nu qq). The final states considered for the search have large missing transverse momentum, an isolated electron or muon, and one of the following: either two jets identified as originating from bottom quarks, or two photons, or a second electron or muon with the same electric charge. The analysis is based on 20.3 mathrm {fb}^{-1} of sqrt{s}=8{mathrm { TeV}} proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations, and limits are set in the context of a simplified supersymmetric model.

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. If the masses of top and bottom squarks are below 1 TeV, the direct pair production cross-section is sufficient to produce observable signatures at the ATLAS detector and to probe various theoretical scenarios with the Large Hadron Collider (LHC) data at √s = 8 TeV. The most recent ATLAS results from searches for direct stop and sbottom pair production are presented in these proceedings. No evidence of deviations from the Standard Model expectation has been observed, and the limits have been set on the masses of the top and bottom squarks.

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. If the masses of top and bottom squarks are below 1 TeV, the direct pair production cross-section is sufficient to produce observable signatures at the ATLAS detector and to probe various theoretical scenarios with the Large Hadron Collider (LHC) data at √s = 8 TeV. The most recent ATLAS results from searches for direct stop and sbottom pair production are presented in these proceedings. No evidence of deviations from the Standard Model expectation has been observed, and the limits have been set on the masses of the top and bottom squarks.

Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at s $$ \sqrt{s} $$ = 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 $\tilde{t} \rightarrow t \tilde{\chi}_{1}^{0}$ or $\tilde{t}\rightarrow b\tilde{\chi}_{1}^{\pm} \rightarrow b W^{\left(\ast\right)} \tilde{\chi}_{1}^{0}$, where $\tilde{\chi}_{1}^{0}$ ($\tilde{\chi}_{1}^{\pm}$) 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 $\tilde{t} \rightarrow t \tilde{\chi}_{1}^{0}$. For a branching fraction of 100%, top squark masses in the range 270-645 GeV are excluded for $\tilde{\chi}_{1}^{0}$ masses below 30 GeV. For a branching fraction of 50% to either $\tilde{t} \rightarrow t \tilde{\chi}_{1}^{0}$ or $\tilde{t}\rightarrow b\tilde{\chi}_{1}^{\pm}$, and assuming the $\tilde{\chi}_{1}^{\pm}$ mass to be twice the $\tilde{\chi}_{1}^{0}$ mass, top squark masses in the range 250-550 GeV are excluded for $\tilde{\chi}_{1}^{0}$ masses below 60 GeV.

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

The most recent results of the searches for direct production of third generation squarks with the ATLAS detector are presented. All the selected analyses use 21 fb−1 of pp collisions at √s = 8 TeV and follow the assumptions of a Minimal Supersymmetric extension of the Standard Model of Particle Physics where the R-parity is conserved and the lightest supersymmetric particle (LSP) is the lightest neutralino. Naturalness considerations require that the partners of the top and bottom quarks are light (O (1 TeV)) and hence have a relatively high production cross-section at the LHC. Since no deviations from the Standard Model predictions are observed, limits are set for different mass hierarchies and mass relations between the bottom and top squarks and the lightest chargino and neutralino.

Search for a Supersymmetric Partner to the Top Quark in Final States with Jets and Missing Transverse Momentum ats=7 TeVwith the ATLAS Detector

A search for direct pair production of supersymmetric top squarks (t(1)) is presented, assuming the t(1) decays into a top quark and the lightest supersymmetric particle, χ(1)(0), and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5(-3.6)(+3.7)(4.4(-1.3)(+1.7)) events in two signal regions based on ∫Ldt = 4.7 fb(-1) of pp collision data taken at sqrt[s] = 7 TeV with the ATLAS detector at the LHC. An exclusion region in the t(1) versus χ(1)(0) mass plane is evaluated: 370<m(t)(1)}<465 GeV is excluded for m(χ)(1)(0) ~ 0 GeV while m(t)(1) = 445 GeV is excluded for m(χ)(1)(0) ≤ 50 GeV.