Search For Scalar Leptoquarks Research Articles

Searches for scalar leptoquarks and differential cross-section measurements in dilepton\u2013dijet events in proton\u2013proton collisions at a centre-of-mass energy of varvec{sqrt{s}} = 13\xa0TeV with the ATLAS experiment

Searches for scalar leptoquarks pair-produced in proton–proton collisions at sqrt{s}=13 TeV at the Large Hadron Collider are performed by the ATLAS experiment. A data set corresponding to an integrated luminosity of 36.1 fb^{-1} is used. Final states containing two electrons or two muons and two or more jets are studied, as are states with one electron or muon, missing transverse momentum and two or more jets. No statistically significant excess above the Standard Model expectation is observed. The observed and expected lower limits on the leptoquark mass at 95% confidence level extend up to 1.29 TeV and 1.23 TeV for first- and second-generation leptoquarks, respectively, as postulated in the minimal Buchmüller–Rückl–Wyler model, assuming a branching ratio into a charged lepton and a quark of 50%. In addition, measurements of particle-level fiducial and differential cross sections are presented for the Zrightarrow ee, Zrightarrow mu mu and tbar{t} processes in several regions related to the search control regions. Predictions from a range of generators are compared with the measurements, and good agreement is seen for many of the observables. However, the predictions for the Zrightarrow ell ell measurements in observables sensitive to jet energies disagree with the data.

Search for scalar leptoquarks in pp collisions at = 13 TeV with the ATLAS experiment

An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at = 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb−1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results.

Searches for scalar leptoquarks in pp collisions at [Formula: see text] = 8TeV with the ATLAS detector.

Searches for pair-produced scalar leptoquarks are performed using 20 fb^{-1} of proton–proton collision data provided by the LHC and recorded by the ATLAS detector at sqrt{s}=8 TeV. Events with two electrons (muons) and two or more jets in the final state are used to search for first (second)-generation leptoquarks. The results from two previously published ATLAS analyses are interpreted in terms of third-generation leptoquarks decaying to bnu _{tau }bar{b}bar{nu _{tau }} and tnu _{tau }bar{t}bar{nu _{tau }} final states. No statistically significant excess above the Standard Model expectation is observed in any channel and scalar leptoquarks are excluded at 95 % CL with masses up to m_{mathrm {LQ1}}< 1050 GeV for first-generation leptoquarks, m_{mathrm {LQ2}}< 1000 GeV for second-generation leptoquarks, m_{mathrm {LQ3}}< 625 GeV for third-generation leptoquarks in the bnu _{tau }bar{b}bar{nu _{tau }} channel, and 200 < m_{mathrm {LQ3}}< 640 GeV in the tnu _{tau }bar{t}bar{nu _{tau }} channel.

A search for scalar leptoquarks in Z 0 decays

A search for scalar leptoquarks has been performed with data from the OPAL detector at the e +e − storage ring LEP. In a data sample corresponding to an integrated luminosity of 6.3 pb −1 no evidence for leptoquark production was observed where the leptoquark decays into a quark and either a charged lepton (e, μ, τ) or a neutrino. An upper limit of 1.7 pb on the production cross section for leptoquarks is obtainedassuming a branching ratio of 50% for the decay of the leptoquark into the channels with a charged lepton. Lower limits on the leptoquark mass between 41.4 and 46.4 GeV/ c 2 at 95% CL are obtained, depending on the effecte SU(2) × U(1) invariant couplings assigned to the leptoquark.