We realized a phenomenological study of top-antitop production in the environment of CERN's Compact Linear Collider project in its third stage. We followed the approach of Standard Model Effective Filed Theory (SMEFT), using the Warsaw basis for the set of mass-dimension 6 operators. From this basis, we analyzed separately the five operators that generate contributions at tree-level to the process $e^+e^-\rightarrow t\bar{t}$, namely: $\mathbb{O}{tW},\: \mathbb{O}{tB},\: \mathbb{O}{\phi t},\: \mathbb{O}{\phi q(1)} \text{ and } \mathbb{O}{\phi q(3)}$. The Beyond Standard Model (BSM) effects associated with these operators were characterized with three techniques: 1) we parameterized their impact on the total cross section in terms of a quadratic function in the Wilson coefficients, 2) we studied the dependence of cross section on the momentum transfer at the top-antitop production vertex using the differential distributions as a function of transverse momentum, and 3) we established bounds on the absolute values of the Wilson coefficients. These bounds are a measure of the sensitivity of our analysis for detecting BSM effects under the SMEFT paradigm. The results obtained show that our method has enough sensitivity for detecting linear BSM effects in the mostly negative polarization of CLIC ($\mathcal{P}{e^-}=-0.8$), yielding bounds of the order of $10^{-2}\text{ TeV}^{-2}$ for the coefficients $c_{tW,tB}$ and of the order of $1\text{ TeV}^{-2}$ for the coefficients $c_{\phi t,\phi q}$. For the mostly positive polarization ($\mathcal{P}{e^-}=+0.8$), we didn't reach enough sensitivity for detecting the linear BSM effects, yielding bounds of the order of $10^{-1} \text{ TeV}^{-2}$ for the coefficients $c{tW,tB}$ and of the order of $10\text{ TeV}^{-2}$ for the coefficients $c_{\phi t,\phi q}$, both of which lie in the quadratic SMEFT regime.

pablocov.i23@gmail.com

Pablo Villaseñor Inda