Abstract
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.
Highlights
Background estimationThe main SM background processes to the LQ1 and LQ2 searches are the production of Z /γ ∗+jets events, ttevents where both top quarks decay leptonically, and diboson events
The signal stregth and the background scale factors are treated as free parameters, the systematic uncertainties are treated as nuisance parameters
Searches for pair-production of first, second- and thirdgeneration scalar leptoquarks have been performed with the ATLAS detector ity of 20 fb−1 of at the LHC using an integr√ated luminosdata from pp collisions at s = 8 TeV
Summary
[10] is used as a benchmark model for scalar LQ production It postulates additional constraints on the LQ properties, namely that the couplings have to be purely chiral, and makes the assumption that LQs are grouped into three families (first, second and third-generation) that couple only to leptons and quarks within the same generation. Pair-produced third-generation scalar LQs decaying to bντ bντ have been excluded by the CMS Collaboration for masses below 700 GeV at β = 0, and for masses below 560 GeV o√ver the full β range using 19.7 fb−1 of data collected at s = 8 TeV [15]. 2 3 e) final state are allowed, kinematic suppression factors which favour LQ decays to bquarks over t-quarks and the relative strengths of the Yukawa couplings would have to be considered Since these suppression factors are model dependent, limits are not provided as a function of β for the LQ3 channels
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