Scalar leptoquark pair production at the LHC: precision predictions in the era of flavour anomalies

Abstract

We comprehensively examine precision predictions for scalar leptoquark pair production at the LHC. In particular, we investigate the impact of lepton t-channel exchange diagrams that are potentially relevant in the context of leptoquark scenarios providing an explanation for the flavour anomalies. We also evaluate the corresponding total rates at the next-to-leading order in QCD. Moreover, we complement this calculation with the resummation of soft-gluon radiation at the next-to-next-to-leading logarithmic accuracy, hence providing the most precise predictions for leptoquark pair production at the LHC to date. Relying on a variety of benchmark scenarios favoured by the anomalies, our results exhibit an interesting interplay between the t-channel diagram contributions, the flavour texture satisfied by the leptoquark Yukawa couplings, the leptoquark masses and their representations under the Standard Model gauge group, as well as the chosen set of parton densities used for the numerical evaluations. The net effect on a cross section turns out to be very non-generic and ranges up to about 60% with respect to the usual next-to-leading-order predictions in QCD (i.e. without any t-channel contribution) for some scenarios considered. Dedicated calculations are thus required for any individual leptoquark model that could be considered in a collider analysis in order to assess the size of the studied corrections. In order to facilitate such calculations we provide dedicated public numerical packages.

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

“…From the theoretical side, calculations for cross sections of scalar leptoquark pair production are available at the next-to-leading order (NLO) in the strong coupling constant α s already for some time [67,68]. More recently these fixed-order calculations have been matched with parton showers [69,70], and with soft-gluon resummation up to next-to-nextto-leading logarithmic accuracy [71][72][73]. In the latter works, in addition to the pure-QCD contribution, also so-called t-channel contributions (i.e.…”

“…In the present work, we investigate the relevance of the off-diagonal production mechanism in more detail, in particular in the context of models relevant for explaining flavour anomalies. Given the impact of higher-order QCD effects on the predictions for scalar leptoquark pair-production reported in [71][72][73], and generally their relevance for the production of heavy coloured particles in hadronic channels, we increase the precision of the off-diagonal production mechanism of scalar leptoquarks by calculating the associated NLO-QCD corrections. We also compare the off-diagonal production rates with diagonal production through both QCD and Yukawa coupling-induced t-channel mechanisms.…”

“…We also compare the off-diagonal production rates with diagonal production through both QCD and Yukawa coupling-induced t-channel mechanisms. The computations are included in our framework of scalar leptoquark pair production for various leptoquark models [71][72][73] with the MadGraph5_aMC@NLO [92] and POWHEG-BOX [93][94][95] software. In addition, we comprehensively study the impact of the Yukawa-coupling-driven contributions on inclusive rates for phenomenologically viable leptoquark models that offer a solution to the flavour anomalies.…”

On Drell-Yan production of scalar leptoquarks coupling to heavy-quark flavours

“…The main goal of this article is to refine the theoretical description of DY production in scalar LQ models (see also [44][45][46][47][48][49][50][51][52][53] for publications similar in spirit). To this purpose we calculate the next-to-leading order (NLO) QCD corrections to pp → + − production.…”

New Physics in $b \to s μμ$: FCC-hh or a Muon Collider?

“…Leptoquarks are colored particles and therefore easily produced in hadron colliders thanks to the QCD interactions [93][94][95][96][97][98][99][100]. The representative Feynman diagram is shown in Fig.…”