Second-generation Squarks Research Articles

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.

Search for squarks and gluinos in final states with jets and missing transverse momentum using 36 fb−1 of 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 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 limit at the 95\% confidence level on the mass of the gluino is set at 2.03 TeV for a simplified model incorporating only a gluino 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 1.55 TeV are excluded if the lightest neutralino is massless. These limits substantially extend the region of supersymmetric parameter space previously excluded by searches with the ATLAS detector.

Likelihood analysis of the pMSSM11 in light of LHC 13-TeV data

We use MasterCode to perform a frequentist analysis of the constraints on a phenomenological MSSM model with 11 parameters, the pMSSM11, including constraints from sim 36/fb of LHC data at 13 TeV and PICO, XENON1T and PandaX-II searches for dark matter scattering, as well as previous accelerator and astrophysical measurements, presenting fits both with and without the (g-2)_mu constraint. The pMSSM11 is specified by the following parameters: 3 gaugino masses M_{1,2,3}, a common mass for the first-and second-generation squarks m_{tilde{q}} and a distinct third-generation squark mass m_{tilde{q}_3}, a common mass for the first-and second-generation sleptons m_{tilde{ell }} and a distinct third-generation slepton mass m_{tilde{tau }}, a common trilinear mixing parameter A, the Higgs mixing parameter mu , the pseudoscalar Higgs mass M_A and tan beta . In the fit including (g-2)_mu , a Bino-like tilde{chi }^0_{1} is preferred, whereas a Higgsino-like tilde{chi }^0_{1} is mildly favoured when the (g-2)_mu constraint is dropped. We identify the mechanisms that operate in different regions of the pMSSM11 parameter space to bring the relic density of the lightest neutralino, tilde{chi }^0_{1}, into the range indicated by cosmological data. In the fit including (g-2)_mu , coannihilations with tilde{chi }^0_{2} and the Wino-like tilde{chi }^pm _{1} or with nearly-degenerate first- and second-generation sleptons are active, whereas coannihilations with the tilde{chi }^0_{2} and the Higgsino-like tilde{chi }^pm _{1} or with first- and second-generation squarks may be important when the (g-2)_mu constraint is dropped. In the two cases, we present chi ^2 functions in two-dimensional mass planes as well as their one-dimensional profile projections and best-fit spectra. Prospects remain for discovering strongly-interacting sparticles at the LHC, in both the scenarios with and without the (g-2)_mu constraint, as well as for discovering electroweakly-interacting sparticles at a future linear e^+ e^- collider such as the ILC or CLIC.

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.

Summary of the searches for squarks and gluinos using s = 8 $$ \sqrt{s}=8 $$ TeV pp collisions with the ATLAS experiment at the LHC

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 models that assume R-parity conservation, the limit on the gluino mass exceeds 1150 GeV at 95% confidence level, for an LSP mass smaller than 100 GeV. Furthermore, exclusion limits are set for left-handed squarks in a phenomenological MSSM model, a minimal Supergravity/Constrained MSSM model, R-parity-violation scenarios, a minimal gauge-mediated supersymmetry breaking model, a natural gauge mediation model, a non-universal Higgs mass model with gaugino mediation and a minimal model of universal extra dimensions.

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using s = 8 $$ \sqrt{s}=8 $$ TeV proton-proton collision data

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 supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with $\tan\beta=30$, $A_0=-2m_0$ and $\mu> 0$, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector.

Non-degenerate squarks from flavored gauge mediation

Abstract We study the squark spectra of Flavored Gauge Mediation Models, in which messenger-matter uperpotential couplings generate new, generation-dependent contributions to the squark masses. The new couplings are controlled by the same flavor symmetry that explains the fermion masses, leading to excellent alignment of the quark and squark mass matrices. This allows for large squark mass splittings consistent with all flavor bounds. In particular, second-generation squarks are often significantly lighter than the first-generation squarks. As squark production at the LHC is dominated by the up- and down-squarks and the efficiencies for squark searches increase with their masses, the charm and/or strange squark masses can be well below the current LHC bounds. At the same time, even with a single set of messengers, the models can generate large stop mixings which result in large loop contributions to the Higgs mass.

Scalar-top masses from SUSY loops with 125 GeV [formula omitted] and precise [formula omitted

We constrain the masses of scalar-tops (stop) by analyzing the new precision Tevatron measurement of the W-boson mass and the LHC/Tevatron indications of a Higgs boson of mass 125.5±1 GeV. Our study adopts Natural SUSY with low fine-tuning, which has multi-TeV first- and second-generation squarks and a light Higgsino mixing parameter μ=150 GeV. An effective Lagrangian calculation is made of mh to 3 loops using the H3m program with weak scale SUSY parameters obtained from RGE evolution from the GUT scale in the Natural SUSY scenario. The SUSY radiative corrections to the Higgs mass imply maximal off-diagonal elements of the stop mass matrix and a mass splitting of the two stops larger than 400 GeV.