Scalar leptoquarks at the LHC and flavour anomalies: a comparison of pair-production modes at NLO-QCD

Abstract

We analyse scalar leptoquark pair production at the LHC with predictions including t-channel lepton exchange contributions up to next-to-leading order (NLO) in QCD. In particular, we calculate NLO-QCD predictions for off-diagonal production channels, i.e. channels that involve two different leptoquark eigenstates and are driven solely by diagrams involving Standard Model leptons in the t-channel at leading order, as opposed to diagonal channels where a pair of the same leptoquark eigenstate is produced. We find that reliable theoretical predictions for both channels require NLO accuracy. The relative importance of the off-diagonal modes depends strongly on the considered scenario. In a generic model involving R2 and S3 leptoquarks, at large values of the Yukawa couplings off-diagonal contributions initiated by valence quarks can be up to an order of magnitude higher than the diagonal production. However, we also find that in phenomenologically viable scenarios addressing the flavour anomalies off-diagonal production is generally negligible, with a few exceptions of 10%–30% of the total rate depending on the treatment of the charm density in the proton.

Novel leptoquark pair production at LHC

“…[14] and extends the scope of the phenomenological discussion of asymmetric pair production presented therein. It also nicely complements recent work on the inclusion of the asymmetric pair production mechanism in the next-to-leading order in QCD cross section determinations for the leptoquark pair production [15]. We stress that the asymmetric contributions to the leptoquark pair production have not been included in any of publicly available experimental search analyses thus far.…”

“…(2.3) that is of quartic nature in terms of y q to start to dominate over the interference term that is of quadratic nature in y q . We note, again, that the automated inclusion of the t-channel term at the next-to-leading order in QCD has been recently introduced in the literature [15].…”

Asymmetric leptoquark pair production at LHC

“…[31] and extends the scope of the phenomenological discussion of asymmetric pair production presented therein. It also nicely complements recent work on the inclusion of the asymmetric pair production mechanism in the next-toleading order in QCD cross section determinations for the leptoquark pair production [32]. We stress that the asymmetric contributions to the leptoquark pair production have not been included in any of publicly available experimental search analyses thus far.…”

Novel leptoquark pair production @LHC

“…[1] and further investigated in Refs. [2,3]. The main feature of this novel mechanism that distinguishes it from the usual leptoquark pair production at, for example, the Large Hadron Collider (LHC) is a fact that the two leptoquarks LQ 1 and LQ 2 that are produced in proton-proton collisions through a 𝑡-channel exchange of a lepton do not comprise a charge conjugate pair, i.e., LQ 1 ≠ (LQ 2 ) * .…”