https://doi.org/10.1140/epjc/s10052-023-11982-1
Regular Article - Theoretical Physics
Leveraging on-shell interference to search for FCNCs of the top quark and the Z boson
1
Fakultät für Physik, TU Dortmund, 44221, Dortmund, Germany
2
III. Physikalisches Institut A, RWTH Aachen University, Aachen, Germany
3
Fermilab Accelerator Laboratory, Batavia, IL, USA
e
emmanuel.stamou@tu-dortmund.de
Received:
7
July
2023
Accepted:
25
August
2023
Published online:
27
September
2023
Flavour-changing-neutral currents (FCNCs) involving the top quark are highly suppressed within the Standard Model (SM). Hence, any signal in current or planned future collider experiments would constitute a clear manifestation of physics beyond the SM. We propose a novel, interference-based strategy to search for top-quark FCNCs involving the Z boson that has the potential to complement traditional search strategies due to a more favourable luminosity scaling. The strategy leverages on-shell interference between the FCNC and SM decay of the top quark into hadronic final states. We estimate the feasibility of the most promising case of anomalous tZc couplings using Monte Carlo simulations and a simplified detector simulation. We consider the main background processes and discriminate the signal from the background with a deep neural network that is parametrised in the value of the anomalous tZc coupling. We present sensitivity projections for the HL-LHC and the FCC-hh. We find an expected 95% CL upper limit of 
for the HL-LHC. In general, we conclude that the interference-based approach has the potential to provide both competitive and complementary constraints to traditional multi-lepton searches and other strategies that have been proposed to search for tZc FCNCs.
© The Author(s) 2023
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Funded by SCOAP3. SCOAP3 supports the goals of the International Year of Basic Sciences for Sustainable Development.
