Search for pair production of scalar leptoquarks decaying into first- or second-generation leptons and top quarks in proton–proton collisions at $$\sqrt{s}$$ = 13 TeV with the ATLAS detector

Abstract

A search for pair production of scalar leptoquarks, each decaying into either an electron or a muon and a top quark, is presented. This is the first leptoquark search using ATLAS data to investigate top-philic cross-generational couplings that could provide explanations for recently observed anomalies in B meson decays. This analysis targets high leptoquark masses which cause the decay products of each resultant top quark to be contained within a single high-$$p_{\mathrm {T}}$$ p T large-radius jet. The full Run 2 dataset is exploited, consisting of $$139~\hbox {fb}^{-1}$$ 139 fb - 1 of data collected from proton–proton collisions at $$\sqrt{s}=13~\mathrm {TeV}$$ s = 13 TeV from 2015 to 2018 with the ATLAS detector at the CERN Large Hadron Collider. In the absence of any significant deviation from the background expectation, lower limits on the leptoquark masses are set at $$1480~\mathrm {GeV}$$ 1480 GeV and $$1470~\mathrm {GeV}$$ 1470 GeV for the electron and muon channel, respectively.

Resonant third-generation leptoquark signatures at the Large Hadron Collider

“…While the ATLAS and the CMS collaborations have mainly focused on LQ pair production via strong interactions in gluon-gluon fusion or quark-antiquark annihilation (cf. [39][40][41][42][43] for the latest results), the importance of LQ pair production via t-channel exchange of a lepton, of LQ exchange in Drell-Yan (DY) like di-lepton production and of single LQ production in gluon-quark fusion in constraining the quark-lepton-LQ couplings has also been established [28,29,[44][45][46][47][48][49][50][51][52][53][54][55][56][57].…”

Novel leptoquark pair production at LHC

“…(See, for example, refs. [41][42][43][44][45] for a sample of the latest bounds.) The relevant cross sections for the leptoquark pair production in proton-proton collisions are already available at the next-to-leading order [46][47][48][49][50] as well as the next-to-next-to-leading order [51][52][53][54] in strong coupling constant and the associated tools to produce these cross sections are readily accessible for the signal simulation if and when needed.…”

Flavorful leptoquarks at the LHC and beyond: spin 1

“…Leptoquark-based explanations of the deviations found in B-physics motivated the recent search for pair-produced scalar leptoquarks with 139 fb −1 of data from 13 TeV p-p collisions [23]. Mass limits for scalar leptoquarks decaying dominantly to top and electron (muon), obtained from this search, are 1470 GeV (1480 GeV).…”

“…The reason why this simplified framework is sensible is two-fold: there is presently no necessity to consider couplings to electrons, and flavor symmetries explaining neutrino masses and mixing result in leptoquark couplings to a single lepton species [21]. We stress that dedicated searches for leptoquarks decaying to leptons other than muons [23] are well-motivated and complementary, however, beyond the scope of this work.…”

“…To explore more general settings we employ in addition a flipped benchmark pattern, with inverted hierarchy, and a democratic one. Note that flavor non-diagonal couplings to leptons and quarks are required to explain the anomalies (1.1), as is taken into account in recent leptoquark searches in pair production at ATLAS [22,23]; see [24][25][26][27] for other recent single and pair production searches and [28] for a review on leptoquark phenomenology.…”