Study of anomalous Spin/CP components on the Higgs coupling to W pairs with the ATLAS detector

Anomalous Spin/CP components in the $HWW$ vertex would be evidence of physics beyond the Standard Model. More specifically, the measurement of anomalous CP-odd components would entail a new source of CP-violation that could, perhaps, explain the observed baryonic asymmetry of the Universe. This work studies the ATLAS sensitivity these components, with an integrated luminosity $L = 139 \mathrm{fb}^{-1}$ at $\sqrt{s} = 13 \:\mathrm{TeV}$. It targets the $W\!H \to \ell \nu b \bar{b}, \ell = e,\mu$ process in the boosted regime, $p_{T_W} > 250 \:\mathrm{GeV}$, where the sensitivity is higher. After optimization of the event selection, the sensitivity to the SM signal and to signals with additional anomalous components was computed, by measuring the expected signal strength, $\mu_{exp}$, and the expected significance, $Z_{exp}$. For the Standard Model (SM) signal, $\mu_{exp} = 1.00 \pm 0.41$ and $Z_{exp}=2.52\sigma$. For signals with anomalous CP-even components, and also for a signal with an anomalous CP-odd component with large coupling, the expected signal strengths are not compatible with their SM value, with $Z_{exp} > 5\sigma$. For a signal with an anomalous CP-odd component with smaller coupling, $\mu_{exp} = 1.54 \pm 0.42$ and $Z_{exp}=4.04\sigma$, compatible with the SM measurement. A set of angular observables sensitive to the different anomalous components is introduced, showing that the asymmetry in the \cDPlus observable has a value of $A(\cos \delta^+) = -0.319 \pm 0.12$ for the signal with an anomalous CP-odd component with smaller coupling, and a zero value for SM sample and backgrounds, thus improving the sensitivity.