Searches for new physics breaking the CP and flavor symmetries in the top quark sector at CMS

TL;DR

The paper addresses potential new physics in the top quark sector that could violate CP and flavor symmetries by employing SMEFT to parameterize a broad set of dimension-6 operators. It presents two main results: a CP-violation search in top quark pair production in association with a Z boson using CP-odd observables and equivariant neural networks, and a flavor-structure EFT study in multilepton final states that constrains generation-dependent operators across multiple regions. Across both analyses, no significant deviations from the SM are observed, and limits are placed on relevant Wilson coefficients, illustrating a robust methodology for probing symmetry-violating top interactions that will improve with larger Run 2/Run 3 datasets.

Abstract

The top quark plays an important role in a number of new physics models, some of which introduce violations to some of the accidental symmetries of the SM, such as the lepton number conservation or introduce additional sources of others already broken, such as the CP symmetry. A set of measurements is presented that probe violation of these symmetries in processes involving the top quark, in association with additional particles.

Figures (6)

• Figure 1: Representative diagrams of ${ }\xspace{ }\xspace{ }\xspace$ (left) and ${ }\xspace{ }\xspace{ }\xspace$ production (right). Taken from TOP24012.
• Figure 2: Distributions of $g_{c_{{ }\xspace{ }\xspace}^{\mathrm{I}}\xspace}$ (left) and $g_{c_{{ }\xspace{ }\xspace}^{\mathrm{I}}\xspace}$ (right), for ${ }\xspace{ }\xspace{ }\xspace$ and ${ }\xspace{ }\xspace{ }\xspace$ events, respectively. Taken from TOP24012.
• Figure 3: Distributions of $g_{c_{{ }\xspace{ }\xspace}^{\mathrm{I}}\xspace}$ (left) and $g_{c_{{ }\xspace{ }\xspace}^{\mathrm{I}}\xspace}$ (right) in the $c_{{ }\xspace{ }\xspace}^{\mathrm{I}}$-like and $c_{{ }\xspace{ }\xspace}^{\mathrm{I}}$-like regions, respectively. Taken from TOP24012.
• Figure 4: Likelihood scans as functions of $c_{{ }\xspace{ }\xspace}^{\mathrm{I}}$ and $c_{{ }\xspace{ }\xspace}^{\mathrm{I}}$, including linear contributions only (left) and both linear and quadratic contributions (right). Taken from TOP24012.
• Figure 5: Upper row: Distribution of the $$ boson candidate $p_{\text{T}}$ for ${ }\xspace{ }\xspace{ }\xspace$ (left), ${ }\xspace{ }\xspace$ (middle), and ${ }\xspace{ }\xspace$ (right) simulated events, each in its corresponding region. The SM prediction is shown along the prediction for different BSM scenarios. Lower row: Observed and simulated distributions of the $$ boson candidate $p_{\text{T}}$ in the ${ }\xspace{ }\xspace{ }\xspace$ (left), ${ }\xspace{ }\xspace$ (middle), and ${ }\xspace{ }\xspace$ (right) regions. Taken from TOP23009.