Topping-up multilepton plus b-jets anomalies at the LHC with a $Z^{\prime }$ boson

Abstract

During the last years ATLAS and CMS have reported a number of slight to mild discrepancies in signatures of multileptons plus $b$-jets in analyses such as $t\bar{t}H$, $t\bar{t}{W}^{\pm }$, $t\bar{t}Z$ and $t\bar{t}t\bar{t}$. Among them, a recent ATLAS result on $t\bar{t}H$ production has also reported an excess in the charge asymmetry in the same-sign dilepton channel with two or more $b$-tagged jets. Motivated by these tantalizing discrepancies, we study a phenomenological New Physics model consisting of a $Z^{\prime }$ boson that couples to up-type quarks via right-handed currents: $t_R{\gamma }^{\mu }{\bar{t}}_R$, $t_R{\gamma }^{\mu }{\bar{c}}_R$, and $t_R{\gamma }^{\mu }{\bar{u}}_R$. The latter vertex allows to translate the charge asymmetry at the LHC initial state protons to a final state with top quarks which, decaying to a positive lepton and a $b$-jet, provides a crucial contribution to some of the observed discrepancies. Through an analysis at a detector level, we select the region in parameter space of our model that best reproduces the data in the aforementioned $t\bar{t}H$ study, and in a recent ATLAS $t\bar{t}t\bar{t}$ search. We find that our model provides a better fit to the experimental data than the Standard Model for a New Physics scale of approximately $\sim$500 GeV, and with a hierarchical coupling of the $Z^{\prime }$ boson that favours the top quark and the presence of FCNC currents. In order to estimate the LHC sensitivity to this signal, we design a broadband search featuring many kinematic regions with different signal-to-background ratio, and perform a global analysis. We also define signal-enhanced regions and study observables that could further distinguish signal from background. We find that the region in parameter space of our model that best fits the analysed data could be probed with a significance exceeding 3 standard deviations with just the full Run-2 dataset.

arXiv comment33 pages, 16 figures, appendix included. Matches JHEP version. Changes in text and in Figures. References added. Comments welcome

References in corpus (33)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• The anti-k_t jet clustering algorithm
• An Introduction to PYTHIA 8.2
• Asymptotic formulae for likelihood-based tests of new physics
• DELPHES 3, A modular framework for fast simulation of a generic collider experiment
• FeynRules 2.0 - A complete toolbox for tree-level phenomenology
• Parton distributions with LHC data
• Tuning PYTHIA 8.1: the Monash 2013 Tune
• HistFitter software framework for statistical data analysis
• Improved Constraints on Z' Bosons from Electroweak Precision Data
• Implications of D^0-\bar D^0 Mixing for New Physics
• Large NLO corrections in $t\bar{t}{W}^{\pm }$ and $t\bar{t}t\bar{t}$ hadroproduction from supposedly subleading EW contributions
• Implications of the LHCb Evidence for Charm CP Violation
• Top-quark pair hadroproduction in association with a heavy boson at NLO+NNLL including EW corrections
• Matrix Elements of 4-fermion Operators with Quenched Wilson Fermions
• The Standard Model confronts CP violation in $D^0\to {\pi }^{+}{\pi }^{-}$ and $D^0\to K^{+}{K}^{-}$
• Associated top quark pair production with a heavy boson: differential cross sections at NLO+NNLL accuracy
• Four Tops for LHC
• The emergence of multi-lepton anomalies at the LHC and their compatibility with new physics at the EW scale
• Anatomy of inclusive $t\overline{t}W$ production at hadron colliders
• The simplest of them all: $t\bar{t}{W}^{\pm }$ at NLO accuracy in QCD
• Top-philic $Z^{\prime }$ Forces at the LHC
• Constraining $t\to u$ flavor changing neutral Higgs coupling at the LHC
• A charged Z' to conciliate the apparent disagreement between top-antitop Tevatron forward-backward asymmetry and LHC charge asymmetry
• Top A_FB at the Tevatron vs. charge asymmetry at the LHC in chiral U(1) flavor models with flavored Higgs doublets
• NLO QCD corrections to off-shell $\text{t}\bar{\text{t}}{\text{W}}^{+}$ production at the LHC
• Bounding the $Z^{\prime }tc$ coupling from $D^0-\overline{D^0}$ mixing and single top production at the ILC
• Search for $t{Z}^{\prime }$ associated production induced by $tc{Z}^{\prime }$ couplings at the LHC
• Novel Collider and Dark Matter Phenomenology of a Top-philic Z'
• Four-top as probe of light top-philic New Physics
• Top FCNC induced by a Z' boson
• $t{Z}^{\prime }$ production at hadron colliders
• Rare decays of the top quark mediated by Z' gauge bosons and flavor violation

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