Drell-Yan production in third-generation gauge vector leptoquark models at NLO+PS in QCD

Abstract

Motivated by the long-standing hints of lepton-flavour non-universality in the b → cℓν and b → sℓ+ℓ− channels, we study Drell-Yan ditau production at the Large Hadron Collider (LHC). In the context of models with third-generation gauge vector leptoquarks (LQs), we calculate the complete $$ \mathcal{O} $$ O (αs) corrections to the pp → τ+τ− process, achieving next-to-leading order (NLO) plus parton shower (NLO+PS) accuracy using the POWHEG method. We provide a dedicated Monte Carlo code that evaluates the NLO QCD corrections on-the-fly in the event generation and use it to study the numerical impact of NLO+PS corrections on the kinematic distributions that enter the existing experimental searches for non-resonant ditau final states. Based on our phenomenological analysis we derive NLO accurate constraints on the masses and couplings of third-generation gauge vector LQs using the latest LHC ditau search results corresponding to an integrated luminosity of around 140 fb−1 of proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV. The presented NLO+PS generator allows for an improved signal modelling, making it an essential tool for future ATLAS and CMS searches for vector LQs in τ+τ− final states at LHC Run III and beyond.

Highpt: A Tool for High-Pt Drell-Yan Tails Beyond the Standard Model

“…Therefore, the NLO effects could be incorporated through kfactors that rescale the cross section bin by bin. The relevant NLO effects have already been studied for specific cases in the literature for the SMEFT [40] and for explicit leptoquark models [41,42]. However, a treatment of the NLO corrections in full generality, as would be required for the present work, is a more involved task that we leave for future work.…”

Third-Family Quark-Lepton Unification and Electroweak Precision Tests

“…[52], we rescale the likelihood obtained from HighPT to match the NLO predictions derived in Ref. [53] for the ATLAS and CMS searches in the b-tag channel. In addition, a lower bound on the vector-like quark mass m Q is implemented by introducing a term in the likelihood of the form…”

Electroweak-flavour and quark-lepton unification: a family non-universal path

“…For large LQ masses, the high-energy process pp → τ + τ − + X, to which the LQ contributes via the t-channel exchange, turns out to be the most effective probe. From the recent CMS analysis in [36], focused on the LQ t-channel exchange amplitude, one extracts the bound Λ U 1.6 TeV [30,37], with a tantalizing 3σ excess for Λ U ≈ 1.6 TeV. Setting Λ U = 1.6 TeV and β sτ L = 0 we get C c LL | th β R =−1 = 0.012 or, equivalently,…”