Search For Squarks Research Articles

Hunting squarks in Higgsino LSP scenarios at the LHC

Current searches for squarks are inefficient in cases when the squark does not directly decay to the lightest supersymmetric particle (LSP), because those decays are Yukawa suppressed. This occurs when producing the first two generations of squarks and when, at the same time, there are several electroweakinos lighter than those squarks. In this paper, we analyze the signal of the pair production of squarks that subsequently decay to an intermediate neutralino (${\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{3}^{0}$) plus jets. The neutralino will then decay to the LSP (mainly Higgsino) and a Higgs. We have simulated the events and designed a discovery strategy based on a signal of two jets, four $b$ quarks, and missing transverse energy. We obtain very promising values for the Large Hadron Collider sensitivity at 14 TeV and $300\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$.

Searches for supersymmetry in CMS

The results from the CMS search for supersymmetric particles based on Run-2 data recorded at a center-of-mass energy of 13[Formula: see text]TeV are summarized. Strong and weak production of SUSY scenarios are considered. Results presented include the searches for squarks and gluinos, direct production of charginos, neutralinos and sleptons. These searches involve final state objects comprising jets, missing transverse momentum, electrons or muons, taus or photons, as well as long-lived particles. The data in these searches are found to be consistent with Standard Model predictions and no significant excess is observed. Upper limits have been set on the masses of supersymmetric particles from a variety of search channels.

Search for squarks and gluinos in final states with one isolated lepton, jets, and missing transverse momentum at sqrt{s}=13 TeV with the ATLAS detector

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 (tilde{chi }^0_1), and quarks, are presented: the signal is characterised by the presence of a single charged lepton (e^{pm } or mu ^{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 delivered by the Large Hadron Collider and recorded by the ATLAS experiment. No statistically significant excess of events above the Standard Model expectation is found. Limits are set on the direct production of squarks and gluinos in simplified models. Masses of gluino (squark) up to 2.2 (1.4 ) are excluded at 95% confidence level for a light tilde{chi }^0_1.

Search for squarks and gluinos in final states with jets and missing transverse momentum using 139 fb\u22121 of sqrt{s} = 13 TeV pp collision data with the ATLAS detector

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 neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.30 TeV for a simplified model containing only a gluino and the lightest neutralino, assuming the latter is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.85 TeV are excluded if the lightest neutralino is massless. These limits extend substantially beyond the region of supersymmetric parameter space excluded previously by similar searches with the ATLAS detector.

Searches for squarks and gluinos with the ATLAS detector

Despite the absence of experimental evidence, weak scale supersymmetry remains one of the best motivated and studied Standard Model extensions. This report summarizes recent results on searches for supersymmetric squarks and gluinos, including third-generation squarks produced directly or via decay of gluinos, using data collected by the ATLAS detector at the LHC. Some models of supersymmetry, including models with R-parity violation, predict that the lightest supersymmetric particle will decay back into Standard Model particles, removing the classical missing transverse momentum signature. These more difficult signatures have also been investigated, and results from these searches are presented.

Search for squarks and gluinos in final states with same-sign leptons and jets using 139 fb\u22121 of data collected with the ATLAS detector

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 featuring both R-parity conservation and R-parity violation, raising the exclusion limits beyond those of previous ATLAS searches to 1600 GeV for gluino masses and 750 GeV for bottom and top squark masses in these scenarios.

Compressed stop searches with two leptons and two b-jets

In top squark (stop) searches with a compressed spectrum, it is very helpful to consider the stop production recoiling against a hard jet from the initial state radiation to obtain a significant amount of missing transverse energy. In particular, the kinematic variable RM which measures the ratio of the lightest neutralino mass and the stop mass proved to be crucial in separating the signals from the backgrounds in both the all-hadronic decay and the semileptonic decay of the stops. Here we generalize the search method to the dileptonic stop decays. In this case, due to the two missing neutrinos, there are not enough kinematic constraint equations to solve for the RM variable exactly, but only render an allowed interval consistent with the event. However, we show that the minimum and the maximum values of this allowed interval still provide useful variables in discriminating signals from the backgrounds. Although in the traditional stop decay to a top quark and the lightest neutralino, the dileptonic mode is not as competitive due to its small branching ratio, it becomes the main search mode if the stops decay through the charginos and sleptons with a compressed spectrum. We show that with the new variables, the dileptonic search of the stop can cover regions of the parameter space which have not been constrained before.

Search for squarks and gluinos in final states with hadronically decaying τ -leptons, jets, and missing transverse momentum using pp collisions at s=13 TeV with the ATLAS detector

A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying $\tau$-lepton is presented. Two exclusive final states with either exactly one or at least two $\tau$-leptons are considered. The analysis is based on proton-proton collisions at $\sqrt{s}$ = 13 TeV corresponding to an integrated luminosity of 36.1 fb$^{-1}$ delivered by the Large Hadron Collider and recorded by the ATLAS detector in 2015 and 2016. No significant excess is observed over the Standard Model expectation. At 95% confidence level, model-independent upper limits on the cross section are set and exclusion limits are provided for two signal scenarios: a simplified model of gluino pair production with $\tau$-rich cascade decays, and a model with gauge-mediated supersymmetry breaking (GMSB). In the simplified model, gluino masses up to 2000 GeV are excluded for low values of the mass of the lightest supersymmetric particle (LSP), while LSP masses up to 1000 GeV are excluded for gluino masses around 1400 GeV. In the GMSB model, values of the supersymmetry-breaking scale are excluded below 110 TeV for all values of $\tan\beta$ in the range $2 \leq \tan\beta \leq 60$, and below 120 TeV for $\tan\beta>30$.

Flavour-violating decays of mixed top-charm squarks at the LHC

We explore signatures related to squark decays in the framework of non-minimally flavour-violating supersymmetry. We consider a simplified model where the lightest squark consists of an admixture of charm and top flavour. By recasting the existing LHC searches for top and charm squarks, we show that the limits on squark masses from these analyses are significantly weakened when the top-charm mixing is sizeable. We propose a dedicated search for squarks based on the tc+{E_{mathrm {T}}^{mathrm {miss}}} final state which enhances the experimental sensitivity for the case of high mixing, and we map its expected reach for the forthcoming runs of the LHC. We emphasize the role of analyses requiring a jet tagged as produced by the fragmentation of a charm quark in understanding the squark mixing pattern, thus providing a novel handle on new physics. Our results show that, in order to achieve full coverage of the parameter space of supersymmetric models, it is necessary to extend current experimental search programmes with analyses specifically targeting the cases where the lightest top-partner is a mixed state.

Constraining slepton and chargino through compressed top squark search

We examine the compressed mass spectrum with sub-TeV top squark left(tilde{t}right) as lightest colored (s)particle in natural supersymmetry (SUSY). Such spectra are searched along with an additional hard jet, not only to boost the soft decay particles, also to yield enough missing transverse momentum. Several interesting kinematic variables are proposed to improve the probe performance for this difficult region, where we concentrate on relatively clean dileptonic channel of the top squark decaying into lightest neutralino (χ10), which is also the lightest supersymmetric particle. In this work, we investigate the merit of these kinematic variables, sensitive to compressed mass region extending the search by introducing additional states, chargino and slepton (sneutrino) having masses in between the tilde{t} and χ10. Enhanced production and lack of branching suppression are capable of providing a strong limit on chargino and slepton/sneutrino mass along with top squark mass. We perform a detailed collider analysis using simplified SUSY spectrum and found that with the present LHC data {M}_{tilde{t}} can be excluded up to 710 GeV right away for {M}_{upchi_1^0} of 640 GeV for a particular mass gap between different states.

Inclusive searches for squarks and gluinos with the ATLAS detector

Despite the absence of experimental evidence, the weak scale supersymmetry remains as one of the best motivated and studied theoretical models beyond the Standard Model. This article summarises recent ATLAS results on inclusive searches for squarks and gluinos in R-parity conserving SUSY scenarios, including third generation squarks produced in the decay of gluinos. The searches involve final states containing jets, missing transverse momentum with and without a light lepton. No significance excess above the Standard Model prediction is observed and exclusion limits are set on 2-dimensional mass planes of benchmark signal models.

Search for squarks and gluinos in events with an isolated lepton, jets, and missing transverse momentum at s=13 TeV with the ATLAS detector

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 TeV for gluino pair production and up to 1.25 TeV for squark pair production.

Likelihood analysis of the minimal AMSB model

We perform a likelihood analysis of the minimal anomaly-mediated supersymmetry-breaking (mAMSB) model using constraints from cosmology and accelerator experiments. We find that either a wino-like or a Higgsino-like neutralino LSP, tilde{chi }^0_{1}, may provide the cold dark matter (DM), both with similar likelihoods. The upper limit on the DM density from Planck and other experiments enforces m_{tilde{chi }^0_{1}} lesssim 3 ,, mathrm {TeV} after the inclusion of Sommerfeld enhancement in its annihilations. If most of the cold DM density is provided by the tilde{chi }^0_{1}, the measured value of the Higgs mass favours a limited range of tan beta sim 5 (and also for tan beta sim 45 if mu > 0) but the scalar mass m_0 is poorly constrained. In the wino-LSP case, m_{3/2} is constrained to about 900,, mathrm {TeV} and m_{tilde{chi }^0_{1}} to 2.9pm 0.1,, mathrm {TeV}, whereas in the Higgsino-LSP case m_{3/2} has just a lower limit gtrsim 650,, mathrm {TeV} (gtrsim 480,, mathrm {TeV}) and m_{tilde{chi }^0_{1}} is constrained to 1.12 ~(1.13) pm 0.02,, mathrm {TeV} in the mu >0 (mu <0) scenario. In neither case can the anomalous magnetic moment of the muon, (g-2)_mu , be improved significantly relative to its Standard Model (SM) value, nor do flavour measurements constrain the model significantly, and there are poor prospects for discovering supersymmetric particles at the LHC, though there are some prospects for direct DM detection. On the other hand, if the tilde{chi }^0_{1} contributes only a fraction of the cold DM density, future LHC -based searches for gluinos, squarks and heavier chargino and neutralino states as well as disappearing track searches in the wino-like LSP region will be relevant, and interference effects enable mathrm{BR}(B_{s, d} rightarrow mu ^+mu ^-) to agree with the data better than in the SM in the case of wino-like DM with mu > 0.

Phenomenological profile of top squarks from natural supersymmetry at the LHC

In supersymmetric models with radiatively-driven naturalness and light higgsinos, the top squarks may lie in the 0.5- 3TeV range and thus only a fraction of natural parameter space is accessible to LHC searches. We outline the range of top squark and lightest SUSY particle masses preferred by electroweak naturalness in the standard parameter space plane. We note that the branching fraction for b-> s\gamma decay favors top squarks much heavier than 500 GeV. Such a range of top-squark mass values is in contrast to previous expectations where m(stop)<500 GeV had been considered natural. In radiative natural SUSY, top squarks decay roughly equally via t1-> bW1 and Z_{1,2} where W1 and Z_{1,2} are higgsino-like electroweak-inos. Thus, top squark pair production should yield all of t\bar{t}+\eslt, t\bar{b}+\eslt, b\bar{t}+\eslt and b\bar{b}+\eslt signatures at comparable rates. We propose that future LHC top squark searches take place within a semi-simplified model which corresponds more closely to expectations from theory.

Searches for Squarks and Gluinos with ATLAS

One of the most versatile and attractive extensions to the successful yet incomplete Standard Model of particle physics is Supersymmetry – a theory the ATLAS experiment at the Large Hadron Collider is looking for in its recorded data. Due to the nature of proton-proton collisions, the recorded physics events are mainly produced via the strong force. This fact makes searches for the superpartners of the gluon and the quarks particularly promising.

Search for squarks and gluinos in events with hadronically decaying tau leptons, jets and missing transverse momentum in proton-proton collisions at [Formula: see text]TeV recorded with the ATLAS detector.

A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton has been performed using 3.2 fb^{-1} of proton–proton collision data at sqrt{s}=13{mathrm { TeV}} recorded by the ATLAS detector at the Large Hadron Collider in 2015. Two exclusive final states are considered, with either exactly one or at least two tau leptons. No excess over the Standard Model prediction is observed in the data. Results are interpreted in the context of gauge-mediated supersymmetry breaking and a simplified model of gluino pair production with tau-rich cascade decays, substantially improving on previous limits. In the GMSB model considered, supersymmetry-breaking scale (Lambda ) values below 92 {mathrm { TeV}} are excluded at the 95% confidence level, corresponding to gluino masses below 2000 {mathrm { GeV}}. For large values of tan beta , values of Lambda up to 107 {mathrm { TeV}} and gluino masses up to 2300 {mathrm { GeV}} are excluded. In the simplified model, gluino masses are excluded up to 1570 {mathrm { GeV}} for neutralino masses around 100 {mathrm { GeV}}. Neutralino masses below 700 {mathrm { GeV}} are excluded for all gluino masses between 800 and 1500 {mathrm { GeV}}, while the strongest exclusion of 750 {mathrm { GeV}} is achieved for gluino masses around 1450 {mathrm { GeV}}.

Search for squarks and gluinos in final states with jets and missing transverse momentum at [Formula: see text] =13 [Formula: see text]with the ATLAS detector.

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~{mathrm{TeV}} proton–proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 3.2 mathrm{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 set at 1.51 {mathrm{TeV}} for a simplified model incorporating only a gluino octet and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.03 {mathrm{TeV}} are excluded for a massless lightest neutralino. These limits substantially extend the region of supersymmetric parameter space excluded by previous measurements with the ATLAS detector.

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum and 20.3 fb−1 of [formula omitted] proton–proton collision data

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 of 20.3 fb−1 recorded in 2012 at s=8 TeV centre-of-mass energy by the ATLAS experiment at the LHC.

Inclusive Searches for Squarks and Gluinos with the ATLAS detector

Despite the absence of experimental evidence, weak scale supersymmetry is one of the best motivated and studied Standard Model extensions. This paper summarises recent results on inclusive searches for supersymmetric squarks and gluinos obtained with the ATLAS detector at the LHC. Results are presented for searches in final state events containing jets, missing transverse momentum, leptons, or photons.

Search for pair-produced third-generation squarks in compressed supersymmetric scenarios using monojet-like final states in pp collisions at [formula omitted] with the ATLAS detector at the LHC

Searches for third-generation squarks are reported, using 20.3 fb-1 of proton-proton collisions at s=8 TeV recorded by the ATLAS experiment at the LHC. The analysis has been optimized for the stop decaying into a charm quark plus a neutralino SUSY signal and it is carried out in several signal regions differing by the requirements on the pT of the leading jet and the missing transverse energy. No excess above the Standard Model background expectation is observed. Limits are set on the visible cross-section of new physics within the requirements of the search. The results of this analysis are interpreted in terms of compressed scenarios for top squark pair production in the decay channels t˜1→c+χ˜10 and t˜1→b+ff′+χ˜10, and in terms of bottom squark pair production in the decay channel b˜1→b+χ˜10. Similar exclusions are found for the nearly mass-degenerated third-generation squarks and the lightest neutralino. In particular, masses of the t˜1 and b˜1 up to 240 GeV are excluded at 95% CL, thus significantly extending the previous collider results.