Abstract
We implement scalar and vector leptoquark (LQ) models in the universal FeynRules output (UFO) format assuming the Standard Model fermion content and conservation of baryon and lepton numbers. Scalar LQ implementations include next-to-leading order (NLO) QCD corrections. We report the NLO QCD inclusive cross sections in proton-proton collisions at 13 TeV, 14 TeV, and 27 TeV for all on-shell LQ production processes. These comprise (i) LQ pair production (pp → ΦΦ) and (ii) single LQ + lepton production (pp → Φℓ) for all initial quark flavours (u, d, s, c, and b). Vector LQ implementation includes adjustable non-minimal QCD coupling. We discuss several aspects of LQ searches at a hadron collider, emphasising the implications of SU(2) gauge invariance, electroweak and flavour constraints, on the possible signatures. Finally, we outline the high-pT search strategy for LQs recently proposed in the literature to resolve experimental anomalies in B-meson decays. In this context, we stress the importance of complementarity of the three LQ related processes, namely, pp → ΦΦ, pp → Φℓ, and pp → ℓℓ.
Highlights
We stress from the onset that there already exist explicit calculations of the pair production of scalar LQs at the next-toleading order (NLO) level [10, 11] as well as several studies of the NLO effects on the single LQ production [7, 12, 13] at the LHC
As an integral part of this analysis, ready-to-use universal FeynRules (UFO) [16] model files for all scalar LQs as well as one vector LQ that are suited for the flavour dependent studies of the LQ signatures at colliders within the MadGraph5 aMC@NLO [17] framework
We validate our numerical results with the existing NLO calculations for the pair production and present novel results for the single production of scalar LQs at the NLO (LO) level
Summary
2.1 Scalar LQ set-up The scalar LQ models we implement comprise S3 ≡ (3, 3, 1/3), R2 ≡ (3, 2, 7/6), R2 ≡ (3, 2, 1/6), S1 ≡ (3, 1, 4/3), and S1 ≡ (3, 1, 1/3), where we specify transformation properties under the SM gauge group. One could entertain a possibility of introducing one or more right-chiral neutrinos extending the SM fermion sector This would allow one to study one additional scalar LQ state — S1 ≡ (3, 1, −2/3) — and to consider additional sets of Yukawa couplings for R2 and S1 [5]. These three scalar multiplets have the same transformation properties under the SM gauge group as the squarks, where the role of the right-chiral neutrino(s) could be played by neutralino(s). By reproducing finite one-loop corrections, we have validated the implementation of the corresponding QCD counterterms in the UFO model(s)
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