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Abstract

A number of popular extensions of the Standard Model of particle physics
predict the existence of doubly charged scalar particles $X^{\pm\pm}$. Such
particles may be long-lived or even stable. If exist, $X^{--}$ could form
atomic bound states with light nuclei and catalyze their fusion by essentially
eliminating the Coulomb barrier between them. Such an $X$-catalyzed fusion
($X$CF) process does not require high temperatures or pressure and may have
important applications for energy production. A similar process of
muon-catalyzed fusion ($\mu$CF) has been shown not to be a viable source of
energy because of the sticking of negative muons to helium nuclei produced in
the fusion of hydrogen isotopes, which stops the catalytic process. We analyze
$X$CF in deuterium environments and show that the $X$-particles can only stick
to $^6$Li nuclei, which are produced in the third-stage reactions downstream in
the catalytic cycle. The corresponding sticking probability is very low, and,
before getting bound to $^6$Li, each $X$-particle can catalyze $\sim 3.5\cdot
10^{9}$ fusion cycles, producing $\sim 7\cdot 10^{4}$ TeV of energy. We also
discuss the ways of reactivating the $X$-particles from the Coulomb-bound
(${\rm ^6Li}X$) states, which would allow re-using them in $X$CF reactions.