1,720,994 research outputs found
Search for supersymmetry in events with four or more leptons in √s=13 TeV pp collisions with ATLAS
No full textResults from a search for supersymmetry in events with four or more charged leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb−1 of proton--proton collisions delivered by the Large Hadron Collider at √s=13 TeV and recorded by the ATLAS detector. Four-lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits are set at the 95% confidence level in simplified models of General Gauge Mediated supersymmetry, where higgsino masses are excluded between 110 and 295 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged leptons, lower limits of 1.4 TeV, 1.06 TeV, and 2.25 TeV are placed on wino, slepton and gluino masses, respectively
Searches for electroweak production of supersymmetric electroweakinos and sleptons with the ATLAS detector
No full textMany supersymmetry models feature gauginos 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. The talk presents results from searches for electroweakino and slepton pair production in final states with leptons, and were performed with pp collisions at a centre-of-mass energy of 13 TeV
Search for Supersymmetry with the ATLAS detector at the LHC
No full textThe search of SUSY is an important part of the physics program at CERN's LHC. The large amount of data successfully collected by the experiments so far, provide a unique opportunity to explore SUSY with novel analysis techniques. If particles predicted by SUSY exist and are not extremely massive, they must be produced at LHC collision events and could be hiding in data collected by the ATLAS and CMS detectors. However, unlike most processes at the LHC, which are governed by strong force interactions, electroweak superpartners would be created through the much weaker electroweak interaction, thus lowering their production rates. Further, most of these new SUSY particles are expected to be unstable and can be searched by tracing their decay products { typically into a known SM particle and a LSP, which could be stable and non-interacting, thus forming a natural dark matter candidate. Despite the low production cross-section of electroweak SUSY processes, events with many leptons in the nal state are very interesting since SM processes mimicking them are very rare. ATLAS searched for such multi-lepton events and presented the results in terms of the number of events from new physics processes with a four-lepton signature, and also in terms of RPV and RPC SUSY models. All data yields are found to be consistent with SM expectations and results are thus used to set upper limits on the event yields from processes beyond the SM. Stringent exclusion limits are set in simplied models of GGM SUSY with higgsino particles, which are assumed to decay into either Higgs or Z bosons. In RPV simplied models with decays of the LSP to charged leptons, exclusions are placed on the mass of wino, slepton and gluino masses up to the TeV scale, extending signicantly the lower limit results set by previous ATLAS searches. Until recently, an important superpartner of the tau slepton, the "stau", had yet to be searched for beyond the exclusion limit of around 90 GeV found at the LHC's predecessor at CERN, the LEP collider. A light stau, if it exists, could play a role in neutralino co-annihilation, moderating the amount of dark matter in the visible universe, which otherwise would be too abundant to explain astrophysical measurements. The search for a light stau is experimentally challenging due to its extremely low production rate in LHC pp collisions, requiring advanced techniques to reconstruct the SM tau leptons it can decay into. In fact, during the LHC Run 1 data taking period, only a narrow parameter region around a stau mass of 109 GeV and a massless lightest neutralino could be excluded by LHC experiments. In LHC Run 2, ATLAS search eorts target the direct production of a pair of staus, each decaying into one tau lepton and one invisible LSP. The ATLAS data do not reveal hints for stau pair production and thus new exclusion limits are set on the mass of staus using dierent assumptions on the presence of both possible stau types (left and right, referring to the two dierent spin states of the tau partner lepton). The limits obtained supersede signicantly the LEP results and are in fact the strongest obtained so far in collider experiments. Overall, both sets of results place strong constraints on important supersymmetric scenarios, which will guide future ATLAS searches. Further, they illustrate the benets brought by advanced analysis techniques, which help improve the sensitivity to new physics phenomena at colliders in the future
Jet production cross section and jet properties in pp collisions at 7 TeV centre-of-mass energy with the ATLAS detector
No full textJet cross sections have been measured with the ATLAS detector for the first time in proton-proton collisions at center-of-mass energy of t TeV. The measurement uses an integrated luminosity of 17 nb-1 recorded at the Large Hadron Collider. The anti-kt algorithm is used to identify jets, with jet resolution parameters R=0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets above 60 GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and angle chi. The experimental results are compared to the expectations based on next-to-leading order QCD.Jet cross sections have been measured with the ATLAS detector for the first time in proton-proton collisions at center-of-mass energy of t TeV. The measurement uses an integrated luminosity of 17 nb-1 recorded at the Large Hadron Collider. The anti-kt algorithm is used to identify jets, with jet resolution parameters R=0.6. The dominant uncertainty comes from the jet energy scale, which is determined to within 7% for central jets above 60 GeV transverse momentum. Inclusive single-jet differential cross sections are presented as functions of jet transverse momentum and rapidity. Dijet cross sections are presented as functions of dijet mass and angle chi. The experimental results are compared to the expectations based on next-to-leading order QCD
Measurement of the multi-jet cross-sections with the ATLAS detector at the LHC
No full textInclusive multi-jet production is studied using the ATLAS detector for proton-proton collisions
with a center-of-mass energy of 7 TeV at the Large Hadron Collider at CERN.
The data sample corresponds to an integrated luminosity of 2.4~pb, using the first proton-proton data collected by the ATLAS detector in 2010.
Results on multi-jet cross sections are presented and compared to both
leading-order plus parton-shower Monte Carlo predictions and next-to-leading-order QCD calculations
Measurement of the Higgs boson production in decays of two τ leptons using the ATLAS detector
No full textA measurement of total production cross sections of the Higgs boson in proton-proton collisions is presented in the H → ττ decay channel. The analysis is performed using 36.1 fb −1 of data recorded by the ATLAS experiment at the Large Hadron Collider at a center- of-mass energy of √s = 13 TeV
Searches for Beyond-Standard-Model Higgs Bosons in ATLAS
No full textPresentation of searches for high mass Beyond the Standard Model Higgs Bosons in several channels, made at Ecom = 13 TeV with the 2015 data performed at the LHC run-1 by the ATLAS collaboration
Cross-section measurements of the Higgs boson decaying to a pair of tau leptons in proton--proton collisions at TeV with the ATLAS detector
No full textA measurement of total production cross sections of the Higgs boson in proton--proton collisions is presented in the decay channel. The analysis is performed using 36.1 of data recorded by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy of TeV. Total cross sections are determined separately for vector boson fusion production and gluon-gluon fusion production. All measurements are in agreement with Standard Model expectations of a Higgs boson with mass of
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