# ICHEP 2022

Jul 6 – 13, 2022
Bologna, Italy
Europe/Rome timezone

## Novel broad-mass search for new scalar particles in FCNC top quark decays using the full Run 2 data of the ATLAS detector

Jul 8, 2022, 7:05 PM
1h 25m
Bologna, Italy

#### Bologna, Italy

Palazzo della Cultura e dei Congressi
Poster Beyond the Standard Model

Nicola Orlando

### Description

No analysis in ATLAS or CMS has so far searched for FCNC decays of top quarks into a new scalar (X) in a broad mass range probing branching ratios below $10^{-3}$. In the case of the Higgs boson, branching ratios $t\rightarrow H+u/c$ are predicted within the SM to be of about $O(10^{-17})/O(10^{-15})$. Several beyond-SM theoretical models predict new particles and enhanced branching ratios. In particular, simple SM extensions involve the Froggatt-Nielsen mechanism, which introduces a scalar field with flavour charge, the so-called flavon, featuring flavour violating interactions. Using the full Run 2 data, ATLAS has performed a search for a scalar of a mass in the range between 20 and 160 GeV and decaying into a pair of bottom quarks. In order to distinguish signal from background, a feed-forward neural network that uses kinematic variables together with various invariant masses of pairs of $b$-jets is used in the fits for the various mass hypotheses. The method, strategy and preliminary results for both FCNC decays $t\rightarrow cX$ and $t\rightarrow uX$ will be presented.

In-person participation Yes