Search for heavy pseudoscalar and scalar bosons decaying to a top quark pair in proton–proton collisions at $\sqrt{s} = 13\,\textrm{TeV}$
(2025) Reports on Progress in Physics — Vol. 88 (2025)
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- A search for pseudoscalar or scalar bosons decaying to a top quark pair (${\text{t}}\bar{\text{t}}$) in final states with one or two charged leptons is presented. The analyzed proton–proton collision data was marc:recorded at $\sqrt{s} = 13\,\textrm{TeV}$ by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 138 $\textrm{fb}^{-1}$. The invariant mass $m_{\mathrm{t}\bar{\mathrm{t}}}$ of the reconstructed ${\text{t}}\bar{\text{t}}$ system and variables sensitive to its spin and parity are used to discriminate against the standard model ${\text{t}}\bar{\text{t}}$ background. Interference between pseudoscalar or scalar boson production and the standard model ${\text{t}}\bar{\text{t}}$ continuum is included, leading to peak-dip structures in the $m_{\mathrm{t}\bar{\mathrm{t}}}$ distribution. An excess of the data above the background prediction, based on perturbative quantum chromodynamics (QCD) calculations, is observed near the kinematic ${\text{t}}\bar{\text{t}}$ production threshold, while good agreement is found for high $m_{\mathrm{t}\bar{\mathrm{t}}}$. The data are consistent with the background prediction if the contribution from a simplified model of a color-singlet ${}^1\mathrm{S}_0^{[1]}$ ${\text{t}}\bar{\text{t}}$ quasi-bound state $\eta_{\mathrm{t}}$, inspired by nonrelativistic QCD, is added. Upper limits at 95% confidence level are set on the coupling between the pseudoscalar or scalar bosons and the top quark for boson masses in the range 365–1000 GeV, relative widths between 0.5% and 25%, and two background scenarios with or without $\eta_{\mathrm{t}}$ contribution.
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Bein, S., Benecke, A., Bethani, A., Bruno, G., Cappati, A., de Favereau de Jeneret, J., Delaere, C., Giammanco, A., Guzel, A. O., Lemaitre, V., Lidrych, J., Malek, P., Mastrapasqua, P., Turkcapar, S., CMS, EMAIL:cms-publication-committee-chair@cern.ch, & et al. (2025). Search for heavy pseudoscalar and scalar bosons decaying to a top quark pair in proton–proton collisions at $\sqrt{s} = 13\,\textrm{TeV}$. Reports on Progress in Physics, 88. https://doi.org/10.1088/1361-6633/ae2207 (Original work published 2025)