scholarly journals Search for physics beyond the standard model in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at s=13 TeV

2021 ◽  
Vol 2105 (1) ◽  
pp. 012012
Author(s):  
Ioanna Papavergou ◽  
Emmanouil Vourliotis
Keyword(s):  
Standard Model ◽  
Mass Parameter ◽  
Mass Difference ◽  
Final States ◽  
Top Squark ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
Upper Limits ◽  
The Standard Model ◽  
Proton Proton Collisions

Abstract The most recent CMS results from a search for supersymmetry (SUSY) with a compressed mass spectrum in leptonic final states will be presented. The search is targeting signatures with missing transverse momentum and two or three low-momentum (soft) leptons. The dataset used is collected by the CMS experiment during the Run–2 proton-proton collisions at s = 13 TeV at the LHC, and corresponds to an integrated luminosity of up to 137 fb−1. The observed data are found to be in agreement with the Standard Model prediction and exclusion upper limits are set on the SUSY particles production cross section. The results are interpreted in terms of electroweakino and top squark pair production. In both cases, a small mass difference between the produced SUSY particles and the lightest neutralino is considered. A wino-bino and a higgsino simplified models are used for the electroweakino interpretation. Exclusion limits at 95% confidence level are set on x ˜ 2 0 / x ˜ 1 ± masses up to 280 GeV for a mass difference between the x ˜ 2 0 / x ˜ 1 ± and the lightest neutralino of 10 GeV for the wino-bino production. In the higgsino interpretation x ˜ 2 0 / x ˜ 1 ± masses are excluded up to 210 GeV for a mass difference of 7.5 GeV and up to 150 GeV for a mass difference of 3 GeV. The results for the higgsino production are additionally interpreted in terms of a phenomenological minimal SUSY extension of the standard model, excluding the higgsino mass parameter μ up to 180 GeV for bino mass parameter M1 = 800 GeV. Upper limits at 95% confidence level are set on the top squark pair production interpretation, excluding top squark masses up to 530 GeV in the four-body top squark decay model and up to 475 GeV in the chargino-mediated decay model for a mass difference between the top squark and the lightest neutralino of 30 GeV.

scholarly journals Search for supersymmetry in final states with two oppositely charged same-flavor leptons and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
T. Bergauer ◽  
...  
Keyword(s):  
Standard Model ◽  
Lepton Pair ◽  
Beyond The Standard Model ◽  
Final States ◽  
Proton Proton ◽  
Proton Collisions ◽  
Missing Transverse Momentum ◽  
The Standard Model ◽  
Proton Proton Collisions ◽  
Oppositely Charged

Abstract A search for phenomena beyond the standard model in final states with two oppositely charged same-flavor leptons and missing transverse momentum is presented. The search uses a data sample of proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, collected by the CMS experiment at the LHC. Three potential signatures of physics beyond the standard model are explored: an excess of events with a lepton pair, whose invariant mass is consistent with the Z boson mass; a kinematic edge in the invariant mass distribution of the lepton pair; and the nonresonant production of two leptons. The observed event yields are consistent with those expected from standard model backgrounds. The results of the first search allow the exclusion of gluino masses up to 1870 GeV, as well as chargino (neutralino) masses up to 750 (800) GeV, while those of the searches for the other two signatures allow the exclusion of light-flavor (bottom) squark masses up to 1800 (1600) GeV and slepton masses up to 700 GeV, respectively, at 95% confidence level within certain supersymmetry scenarios.

scholarly journals Search for dark matter in association with an energetic photon in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Dark Matter ◽  
Transverse Momentum ◽  
Standard Model ◽  
Confidence Level ◽  
Axial Vector ◽  
Beyond The Standard Model ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
Upper Limits ◽  
The Standard Model

Abstract A search for dark matter is conducted in final states containing a photon and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV. The data, collected during 2015–2018 by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 fb−1. No deviations from the predictions of the Standard Model are observed and 95% confidence-level upper limits between 2.45 fb and 0.5 fb are set on the visible cross section for contributions from physics beyond the Standard Model, in different ranges of the missing transverse momentum. The results are interpreted as 95% confidence-level limits in models where weakly interacting dark-matter candidates are pair-produced via an s-channel axial-vector or vector mediator. Dark-matter candidates with masses up to 415 (580) GeV are excluded for axial-vector (vector) mediators, while the maximum excluded mass of the mediator is 1460 (1470) GeV. In addition, the results are expressed in terms of 95% confidence-level limits on the parameters of a model with an axion-like particle produced in association with a photon, and are used to constrain the coupling gaZγ of an axion-like particle to the electroweak gauge bosons.

Implementation of the CMS-EXO-19-002 search in the MadAnalysis 5 framework (physics beyond the Standard Model with multilepton final states; 137 fb−1)

2021 ◽  
Vol 36 (01) ◽  
pp. 2141012
Author(s):  
Eric Conte ◽  
Robin Ducrocq
Keyword(s):  
Standard Model ◽  
Beyond The Standard Model ◽  
Final States ◽  
Text Data ◽  
Proton Proton ◽  
Original Analysis ◽  
The Standard Model ◽  
Light Scalar ◽  
Charged Leptons ◽  
Proton Proton Collisions

In this paper, we present the MadAnalysis 5 implementation of the CMS-EXO-19-002 analysis, probing an excess of events featuring multiple charged leptons in LHC proton–proton collisions at [Formula: see text]. The original analysis is based on data acquired by the CMS detector during the 2016–2018 campaign, which corresponds to an integrated luminosity of 137 fb[Formula: see text]. Data have been tested against hypothetical extensions of the Standard Model where additional leptons can stem from new heavy fermion decays or from new light scalar/pseudoscalar decays. The CMS selection has been fully implemented in the MadAnalysis 5 platform and successfully validated by reproducing official results in the form of signal distributions at the end of the selection.

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

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Standard Model ◽  
Atlas Detector ◽  
Proton Collision ◽  
Top Squark ◽  
Proton Proton ◽  
Direct Production ◽  
Missing Transverse Momentum ◽  
The Standard Model ◽  
Model Predictions ◽  
Proton Proton Collision

AbstractThis 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 $$\sqrt{s}=13$$ s = 13 TeV collected with the ATLAS detector during the LHC Run-2, corresponding to an integrated luminosity of 139 fb$$^{-1}$$ - 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 ($$\tilde{t}_1$$ t ~ 1 ) or the heavier top squark ($$\tilde{t}_2$$ t ~ 2 ), excluding at 95% confidence level $$\tilde{t}_1$$ t ~ 1 and $$\tilde{t}_2$$ t ~ 2 masses up to about 1220 and 875 GeV, respectively.

scholarly journals Search for new phenomena in final states with b-jets and missing transverse momentum in $$ \sqrt{\mathrm{s}} $$ = 13 TeV pp collisions with the ATLAS detector

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Pair Production ◽  
Atlas Detector ◽  
Final States ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
The Standard Model ◽  
Proton Data ◽  
Identification Techniques ◽  
New Phenomena

Abstract 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 $$ \sqrt{s} $$ 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 bottom quarks, and models of pair production of scalar third-generation down-type leptoquarks. No significant excess of events over the Standard Model background expectation is observed in any of the signal regions considered by the analysis. Bottom squark masses below 1270 GeV are excluded at 95% confidence level if the neutralino is massless. In the case of nearly mass-degenerate bottom squarks and neutralinos, the use of dedicated secondary-vertex identification techniques permits the exclusion of bottom squarks with masses up to 660 GeV for mass splittings between the squark and the neutralino of 10 GeV. These limits extend substantially beyond the regions of parameter space excluded by similar ATLAS searches performed previously.

scholarly journals Search for squarks and gluinos in final states with jets and missing transverse momentum using 139 fb−1 of $$ \sqrt{s} $$ = 13 TeV pp collision data with the ATLAS detector

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Simplified Model ◽  
Supersymmetric Particle ◽  
Final States ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
First And Second Generation ◽  
Proton Proton Collisions

Abstract 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 $$ \sqrt{s} $$ 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.

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