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

The ATLAS collaboration
Aaboud, Morad , Aad, Georges , Abbott, Brad , Abdinov, Ovsat , Abeloos, Baptiste , Abhayasinghe, Deshan Kavishka , Abidi, Syed Haider , Abouzeid, Ossama , Abraham, Nicola , Abramowicz, Halina
Eur.Phys.J.C 79 (2019) 733, 2019.

Abstract (data abstract)
"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 dataset corresponding to an integrated luminosity of $36.1~\textrm{fb}^{-1}$ is used. Final states containing two same-flavour charged leptons (electrons or muons) and two or more jets are studied, as are states with one charged lepton, 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 are around 1.25 TeV for first and second generation leptoquarks, as postulated in the minimal Buchmueller-Rueckl-Wyler model, assuming a branching ratio into a charged lepton and a quark of 50%. Measurements of particle-level inclusive and differential cross-sections are presented for the $Z \rightarrow ee$, $Z \rightarrow \mu\mu$ and $t\bar{t} $ processes in several regions which are related to the search control regions. The predictions from a range of generators are compared to the measurements, and a good agreement is seen for most of the observables. However, the predictions for the $Z \rightarrow ee$ and $Z \rightarrow \mu\mu$ measurements in observables which are sensitive to jet energies are observed to disagree with the data. The measurements could be used to improve the generator predictions in these and related regions."

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