Invariant-mass spectra of the sum of particle and antiparticle states of (anti)$^4_{\Lambda}\rm He$  candidates on the upper left and of (anti)$^4_{\Lambda}\rm H$  candidates on the upper right. In the lower panels, the invariant-mass spectra of the particle fraction only of the $^4_{\Lambda}\rm He$ candidates on the left and of the $^4_{\Lambda}\rm H$ candidates on the right are presented. Each spectrum is fitted with a KDE template for the signal peak (blue curve) and an exponential function to model the background (orange curve).