The Higgs boson decay into ZZ decaying to identical fermion pairs

Abstract: In order to investigate various decay channels of the Higgs boson $h$ or the hypothetical dilaton, we consider a neutral particle $X$ with zero spin and arbitrary $CP$ parity. This particle can decay into two off-mass-shell $Z$ bosons ($Z_1^*$ and $Z_2^*$) decaying to identical fermion-antifermion pairs ($f \bar{f}$): $X \to Z_1^* Z_2^* \to f \bar{f} f \bar{f}$. We derive analytical formulas for the fully differential width of this decay and for the fully differential width of $h \to Z_1^* Z_2^* \to 4 \ell$ ($4 \ell$ stands for $4 e$, $4 \mu$, or $2 e 2 \mu$). Integration of these formulas yields some Standard Model histogram distributions of the decay $h \to Z_1^* Z_2^* \to 4 \ell$, which are compared with corresponding Monte Carlo simulated distributions obtained by ATLAS and with ATLAS experimental data.