Positronium formation in the forward direction in positron-C$_{\mathrm{60\thinspace }}$collisions

Following the impact of positrons with matter the formation of exotic electron-positron bound-pair, the positronium (Ps), is a vital process in nature. Varieties of target systems from atoms to smaller molecules to condensed matters have been accessed by the Ps formation spectroscopy. However, clusters and fullerenes in gas-phase have largely been one uncharted target territories until the calculations recently reported by us [1,2]. To further motivate applications of this spectroscopy to fullerene targets and to access target-level- as well as Ps-level-differential measurements, we now compute Ps formation cross sections in the forward collision direction within a very narrow angular range which is likely measurable by the existing technologies. The electronic structure of a C$_{\mathrm{60}}$ molecule is described by the local-density approximation with LB94 exchange-correlation functional [3]. The positron impact on C$_{\mathrm{60}}$ leading to the Ps formation is treated by the continuum distorted-wave-final-state approximation [4]. Comparisons with the angle-integrated result reveal more prominent diffraction resonances in the forward angle signal. [1] Hervieux et al., Phys. Rev. A \textbf{95}, 020701 (R) (2017); [2] Chakraborty et al., J. Phys.: Conf. Series \textbf{875}, 072002 (2017); [3] Choi et al., Phys. Rev. A \textbf{95}, 023404 (2017); [4] Fojon et al., Phys. Rev. A \textbf{54}, 4923 (1996).