ALP-ine quests at the LHC: hunting axion-like particles via peaks and dips in $t \bar{t}$ production

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Preprint
Report number	arXiv:2404.19014 ; DESY-24-059 ; IFT-UAM/CSIC-24-042 ; KA-TP-06-2024 ; MITP-24-044
Title	ALP-ine quests at the LHC: hunting axion-like particles via peaks and dips in $t \bar{t}$ production
Author(s)	Anuar, Afiq (CERN) ; Biekötter, Anke (Mainz U., Inst. Phys. ; U. Mainz, PRISMA) ; Biekötter, Thomas (KIT, Karlsruhe, TP) ; Grohsjean, Alexander (Hamburg U.) ; Heinemeyer, Sven (Madrid, IFT) ; Jeppe, Laurids (DESY) ; Schwanenberger, Christian (Hamburg U. ; DESY) ; Weiglein, Georg (DESY ; Hamburg U., Inst. Theor. Phys. II)
Imprint	2024-04-29
Number of pages	35
Note	28 pages, 9 figures
Subject category	hep-ph ; Particle Physics - Phenomenology
Abstract	We present an analysis of the sensitivity of current and future LHC searches for new spin-0 particles in top-anti-top-quark ($t\bar{t}$) final states, focusing on generic axion-like particles (ALPs) that are coupled to top quarks and gluons. As a first step, we derive new limits on the effective ALP Lagrangian in terms of the Wilson coefficients $c_t$ and $c_{\tilde{G}}$ based on the results of the CMS search using $35.9$ fb$^{-1}$ of data, collected at $\sqrt{s} = 13$ TeV. We then investigate how the production of an ALP with generic couplings to gluons and top quarks can be distinguished from the production of a pseudoscalar which couples to gluons exclusively via a top-quark loop. To this end, we make use of the invariant $t\bar{t}$ mass distribution and angular correlations that are sensitive to the $t\bar{t}$ spin correlation. Using a mass of 400 GeV as an example, we find that already the data collected during Run 2 and Run 3 of the LHC provides an interesting sensitivity to the underlying nature of a possible new particle. We also analyze the prospects for data anticipated to be collected during the high-luminosity phase of the LHC. Finally, we compare the limits obtained from the $t \bar t$ searches to existing experimental bounds from LHC searches for narrow di-photon resonances, from measurements of the production of four top quarks, and from global analyses of ALP-SMEFT interference effects.
Other source	Inspire
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0)

$The background-subtracted inclusive $pp \to \ttbar$ cross section, including resonant $pp \to a$ production and ALP/SM interference, $\sigma_{t \bar t}^{\rm tot} - \sigma_{t \bar t}^{\rm SM}$, is shown in the plane of the ALP couplings $\cG/f_a$ and $\ct/f_a$ for different ALP masses and relative widths of $400 \gev$ and 2.5\% (left) as well as $800 \gev$ and 5.0\% (right). Negative values of $\ct$ are not shown as the cross section is symmetric under the sign change of both $\ct$ and $\cG$, see Eq.~\eqref{eq:xSec_para}.$ $The background-subtracted inclusive $pp \to \ttbar$ cross section, including resonant $pp \to a$ production and ALP/SM interference, $\sigma_{t \bar t}^{\rm tot} - \sigma_{t \bar t}^{\rm SM}$, is shown in the plane of the ALP couplings $\cG/f_a$ and $\ct/f_a$ for different ALP masses and relative widths of $400 \gev$ and 2.5\% (left) as well as $800 \gev$ and 5.0\% (right). Negative values of $\ct$ are not shown as the cross section is symmetric under the sign change of both $\ct$ and $\cG$, see Eq.~\eqref{eq:xSec_para}.$ $Differential distribution in $\mtt$ for the SM (top) and for a pseudoscalar Higgs boson with $m_A = 400 \gev$, 4.0\% width and a coupling strength of $\gAtt = 0.9$, where the SM background has been subtracted (bottom). The left plot shows the distribution inclusive in the variable $\chel$, while the right plot shows it after selecting only events with $\chel$ 0.6$. Our smeared prediction (blue) is compared to the CMS simulation taken from \cite{CMS:2019pzc} (red). All predictions are shown for an integrated luminosity of $35.9 \, \fb$. The gray bands show the expected statistical uncertainty from the SM $\ttbar$ background." width="200px"/> Show more plots

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