Slepton Production Research Articles

Search for supersymmetric sleptons and charginos with the ATLAS detector

A new search for the electroweak production of supersymmetric particles decaying into two leptons with missing transverse momentum is presented. Two simplified models are considered: direct pair production of sleptons decaying into the lightest neutralinos through leptons of the Standard Model (SM) and direct pair production of the lightest charginos decaying into the lightest neutralinos through W bosons of the SM. The analysis targets phase space regions where the difference in mass between the slepton or the lightest chargino and the lightest neutralino is close to or below the mass of the W boson. Such regions with compressed mass spectra have not been covered by any searches conducted so far due to the low cross-section of the supersymmetric signal. Therefore, improved analysis strategies are crucial to separate the supersymmetric signal from the SM backgrounds. A search for an excess of same-flavour lepton pairs in opposite-sign lepton events is made in the direct slepton pair production analysis while a machine learning approach using boosted decision trees is exploited in the chargino pair production analysis and considering both the same-flavour and different-flavour channels. No significant excesses over the expected background are observed using proton-proton collisions data collected by the ATLAS experiment at √s = 13 TeV and exclusion limits at 95% confidence level are set for each considered model. Exclusion limits are also set for selectrons and smuons separately and portions of the region excluded by the search of smuons pair production are expected to be compatible with the g-2 anomaly for small tanβ values.

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.

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.

Probing Compressed Slepton Production at Future Large Hadron Collider

Various supersymmetry searches are carried out at the Large Hadron Collider (LHC) at CERN. While some searches have focused on the color sector, others focused on electroweak production of charginos-neutralinos and sleptons. Since no sign of supersymmetry has yet to be found, limits are set on the masses of the supersymmetric particles. In this phenomenological study, we probe direct slepton signal production in compressed mass spectra scenario at the potential future proton-proton collider operating at a center of mass energy of 33 TeV. We show that slepton signal with masses up to 270 GeV can be discovered at the future hadron collider with the data corresponding to 100 fb-1 integrated luminosity when ΔM =5 GeV.

What the Fermilab muon g−2 experiment tells us about discovering supersymmetry at high luminosity and high energy upgrades to the LHC

Using an artificial neutral network we explore the parameter space of supergravity grand unified models consistent with the combined Fermilab E989 and Brookhaven E821 data on $(g-2)_\mu$. The analysis indicates that the region favored by the data is the one generated by gluino-driven radiative breaking of the electroweak symmetry. This region naturally leads to a split sparticle spectrum with light sleptons and weakinos but heavy squarks, with the stau and the chargino as the lightest charged particles. We show that if the entire deviation from the standard model $(g-2)_{\mu}$ arises from supersymmetry, then supersymmetry is discoverable at HL-LHC and HE-LHC via production and decay of sleptons within the optimal integrated luminosity of HL-LHC and with a smaller integrated luminosity at HE-LHC.

Implementation of the ATLAS-SUSY-2018-32 analysis (sleptons and electroweakinos with two leptons and missing transverse energy; 139 fb−1)

We present the implementation in MadAnalysis 5 of the ATLAS-SUSY-2018-32 search for new physics and document the validation of this re-implementation. This analysis targets, with 139 fb[Formula: see text] of proton–proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector, the electroweak pair production of supersymmetric charginos and sleptons when they further decay into a final state comprising a pair of leptons and missing energy. The validation of our work is based on three [Formula: see text]-parity conserving supersymmetric benchmark setups that feature, respectively, chargino pair-production followed by decays into leptons via an intermediate weak boson, chargino pair-production followed by chargino cascade decays into leptons through a slepton mediator, and slepton pair-production followed by slepton direct decays into leptons.

Search for direct pair production of supersymmetric partners to the {uptau }_{}^{} lepton in proton\u2013proton collisions at sqrt{s}=13,text {TeV}

A search is presented for {uptau }_{}^{} slepton pairs produced in proton–proton collisions at a center-of-mass energy of 13,text {TeV}. The search is carried out in events containing two {uptau }_{}^{} leptons in the final state, on the assumption that each {uptau }_{}^{} slepton decays primarily to a {uptau }_{}^{} lepton and a neutralino. Events are considered in which each {uptau }_{}^{} lepton decays to one or more hadrons and a neutrino, or in which one of the {uptau }_{}^{} leptons decays instead to an electron or a muon and two neutrinos. The data, collected with the CMS detector in 2016 and 2017, correspond to an integrated luminosity of 77.2,text {fb}^{-1}. The observed data are consistent with the standard model background expectation. The results are used to set 95% confidence level upper limits on the cross section for {uptau }_{}^{} slepton pair production in various models for {uptau }_{}^{} slepton masses between 90 and 200,text {GeV} and neutralino masses of 1, 10, and 20,text {GeV}. In the case of purely left-handed {uptau }_{}^{} slepton production and decay to a {uptau }_{}^{} lepton and a neutralino with a mass of 1,text {GeV}, the strongest limit is obtained for a {uptau }_{}^{} slepton mass of 125,text {GeV} at a factor of 1.14 larger than the theoretical cross section.

Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in sqrt{s}=13\xa0text {TeV}pp collisions using the ATLAS detector

A search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons is presented. The analysis is based on 139 fb^{-1} of proton–proton collisions recorded by the ATLAS detector at the Large Hadron Collider at sqrt{s}=13 text {TeV}. Three R-parity-conserving scenarios where the lightest neutralino is the lightest supersymmetric particle are considered: the production of chargino pairs with decays via either W bosons or sleptons, and the direct production of slepton pairs. The analysis is optimised for the first of these scenarios, but the results are also interpreted in the others. No significant deviations from the Standard Model expectations are observed and limits at 95% confidence level are set on the masses of relevant supersymmetric particles in each of the scenarios. For a massless lightest neutralino, masses up to 420 text {Ge}text {V} are excluded for the production of the lightest-chargino pairs assuming W-boson-mediated decays and up to 1 text {TeV} for slepton-mediated decays, whereas for slepton-pair production masses up to 700 text {Ge}text {V} are excluded assuming three generations of mass-degenerate sleptons.

Search for resonant production of second-generation sleptons with same-sign dimuon events in proton\u2013proton collisions at sqrt{s} = 13,text {TeV}

A search is presented for resonant production of second-generation sleptons (widetilde{mu } _{mathrm {L}}, widetilde{nu }_{mu }) via the R-parity-violating coupling {lambda ^{prime }_{211}} to quarks, in events with two same-sign muons and at least two jets in the final state. The smuon (muon sneutrino) is expected to decay into a muon and a neutralino (chargino), which will then decay into a second muon and at least two jets. The analysis is based on the 2016 data set of proton-proton collisions at sqrt{s}=13,text {TeV} recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9,text {fb}^{-1}. No significant deviation is observed with respect to standard model expectations. Upper limits on cross sections, ranging from 0.24 to 730,text {fb}, are derived in the context of two simplified models representing the dominant signal contributions leading to a same-sign muon pair. The cross section limits are translated into coupling limits for a modified constrained minimal supersymmetric model with {lambda ^{prime }_{211}} as the only nonzero R-parity violating coupling. The results significantly extend restrictions of the parameter space compared with previous searches for similar models.

Search for electroweak production of supersymmetric particles in final states with two or three leptons at sqrt{s}=13hbox {TeV} with the ATLAS detector

A search for the electroweak production of charginos, neutralinos and sleptons decaying into final states involving two or three electrons or muons is presented. The analysis is based on 36.1 fb^{-1} of sqrt{s}=13 TeV proton–proton collisions recorded by the ATLAS detector at the Large Hadron Collider. Several scenarios based on simplified models are considered. These include the associated production of the next-to-lightest neutralino and the lightest chargino, followed by their decays into final states with leptons and the lightest neutralino via either sleptons or Standard Model gauge bosons; direct production of chargino pairs, which in turn decay into leptons and the lightest neutralino via intermediate sleptons; and slepton pair production, where each slepton decays directly into the lightest neutralino and a lepton. No significant deviations from the Standard Model expectation are observed and stringent limits at 95% confidence level are placed on the masses of relevant supersymmetric particles in each of these scenarios. For a massless lightest neutralino, masses up to 580 GeV are excluded for the associated production of the next-to-lightest neutralino and the lightest chargino, assuming gauge-boson mediated decays, whereas for slepton-pair production masses up to 500 GeV are excluded assuming three generations of mass-degenerate sleptons.

Slepton production at e^+e^- colliders in the complex MSSM: a full one-loop analysis

For the search for scalar leptons in the minimal supersymmetric standard model (MSSM) as well as for future precision analyses of these particles an accurate knowledge of their production and decay properties is mandatory. We evaluate the cross sections for the slepton production at e^+e^- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanisms e^+e^- rightarrow tilde{l}_{gs} tilde{l}_{gs^{prime }} including soft and hard photon radiation. The dependence of the slepton production cross sections on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to many production cross sections. They amount to roughly 15% of the tree-level results but can go up to 40% or higher in extreme cases. Also the dependence on complex parameters of the one-loop corrections for the production of charged sleptons was found non-negligible. The full one-loop contributions are thus crucial for physics analyses at a future linear e^+e^- collider such as the ILC or CLIC.

Search for electroweak production of supersymmetric states in scenarios with compressed mass spectra at s=13 TeV with the ATLAS detector

A search for electroweak production of supersymmetric particles in scenarios with compressed mass spectra in final states with two low-momentum leptons and missing transverse momentum is presented. This search uses proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015-2016, corresponding to 36.1 fb$^{-1}$ of integrated luminosity at $\sqrt{s}=13$ TeV. Events with same-flavor pairs of electrons or muons with opposite electric charge are selected. The data are found to be consistent with the Standard Model prediction. Results are interpreted using simplified models of R-parity-conserving supersymmetry in which there is a small mass difference between the masses of the produced supersymmetric particles and the lightest neutralino. Exclusion limits at 95% confidence level are set on next-to-lightest neutralino masses of up to 145 GeV for Higgsino production and 175 GeV for wino production, and slepton masses of up to 190 GeV for pair production of sleptons. In the compressed mass regime, the exclusion limits extend down to mass splittings of 2.5 GeV for Higgsino production, 2 GeV for wino production, and 1 GeV for slepton production. The results are also interpreted in the context of a radiatively-driven natural supersymmetry model with non-universal Higgs boson masses.

Resonant slepton production and right sneutrino dark matter in left-right supersymmetry

Right-handed sneutrinos are natural components of left-right symmetric supersymmetric models where the gauge sector is extended to include right-handed weak interactions. Unlike in other models where right-handed sneutrinos are gauge singlets, here the right sneutrino is part of a doublet and could be a dark matter candidate whose annihilation proceeds via gauge interactions. We investigate this possibility, and find that relic density, low-energy observable and direct supersymmetry search constraints can be satisfied when the lightest supersymmetric particle is a right-handed sneutrino. We introduce benchmarks for left-right supersymmetric realizations where either a sneutrino or a neutralino is the lightest superpartner. We then study the LHC signals arising through resonant right-handed slepton production via a WR gauge-boson exchange that lead to final states enriched in leptons, additionally containing a large amount of missing transverse momentum, and featuring a low jet multiplicity. We find that such a resonant production would boost the chances of discovering these weakly interacting supersymmetric particles for a mass range extending beyond 1 TeV already with a luminosity of 100 fb−1. Finally, we compare sneutrino versus neutralino scenarios, and comment on differences with other sneutrino dark matter models.

Search for long-lived charged particles in proton-proton collisions ats=13 TeV

Results are presented of a search for heavy stable charged particles produced in proton-proton collisions at sqrt(s) = 13 TeV using a data sample corresponding to an integrated luminosity of 2.5 inverse femtobarns collected in 2015 with the CMS detector at the CERN LHC. The search is conducted using signatures of anomalously high energy deposits in the silicon tracker and long time of flight measurements by the muon system. The data are consistent with the expected background, and upper limits are set on the cross sections for production of long-lived gluinos, top squarks, tau sleptons, and leptonlike long-lived fermions. These upper limits are equivalently expressed as lower limits on the masses of new states; the limits for gluinos, ranging up to 1610 GeV, are the most stringent to date. Limits on the cross sections for direct pair production of long-lived tau sleptons are also determined.

Precision predictions for direct gaugino and slepton production at the LHC

The search for electroweak superpartners has recently moved to the centre of interest at the LHC. We provide the currently most precise theoretical predictions for these particles, use them to assess the precision of parton shower simulations, and reanalyse public experimental results assuming more general decompositions of gauginos and sleptons.

Searches for electroweak production of supersymmetric charginos, neutralinos and sleptons with the ATLAS detector

Many supersymmetry models feature charginos, neutralinos and also sleptons with masses less than a few hundred GeV. These can give rise to direct pair production rates at the LHC that can be observed in the data sample recorded by the ATLAS detector. This article presents results from searches for charginos, neutralinos and slepton production in final state events characterized by the presence of leptons, missing transverse momentum and possibly jets.

Search for electroweak supersymmetric particle production in final states with two leptons and missing transverse momentum with the ATLAS detector

Searches for the production of electroweak supersymmetric particles decaying into final states with exactly two isolated, oppositely-charged leptons (electrons, muons) and missing transverse momentum are performed using 20.3 fb-1 of 2012 proton-proton collision data at s=8 TeV recorded with the general purpose detector ATLAS at the Large Hardon Collider. The negative search results are interpreted in the framework of simplified Supersymmetry models and in various scenarios of the phenomenological Minimal Supersymmetric Standard Model [Search for direct production of charginos, neutralinos and sleptons in final states with two leptons and missing transverse momentum in pp collisions at s=8 TeV with the ATLAS detector, JHEP 05 (2014) 071. arXiv:1403.5294 [hep-ex]].

ATLAS diboson excess could be anR-parity violating dismuon excess

We propose a new possible explanation of the ATLAS di-boson excess: that it is due to heavy resonant slepton production, followed by decay into di-smuons. The smuon has a mass not too far from the W and Z masses, and so it is easily confused with W or Z bosons after its subsequent decay into di-jets, through a supersymmetry violating and R-parity violating interaction. Such a scenario is not currently excluded by other constraints and remains to be definitively tested in Run II of the LHC. Such light smuons can easily simultaneously explain the discrepancy between the measurement of the anomalous magnetic moment of the muon and the Standard Model prediction.

Searches for electroweak production of supersymmetric gauginos and sleptons with the ATLAS detector

Results from the searches for electroweak production of gauginos or sleptons decaying into leptonic final states performed using 20.3 fb−1 of proton-proton collision data at √S = 8 TeV recorded with the ATLAS experiment at the Large Hadron Collider are presented. No significant excesses are observed with respect to the prediction from Standard Model processes. Limits are set on a wide range of SUSY models.

SUSY searches: Recent results from ATLAS and CMS

Despite the absence of experimental evidence, weak scale supersymmetry remains one of the best motivated and studied Standard Model extension. Recent results from ATLAS and CMS searches for supersymmetric particles are summarized here. Weak and strong production in both R-Parity conserving and R-Parity violating supersymmetric scenarios are considered. In particular, a selection is presented of the most recent searches for squarks and gluinos, third generations squarks, direct production of charginos, neutralinos and sleptons and long-lived particles. These searches involve final states including jets, missing transverse momentum, electron or muons, taus or photons, as well as long-lived particle signatures. The data in these searches was found to be compatible with the estimated Standard Model backgrounds. Therefore, limits have been set on the masses of supersymmetric particles in various models.