Ultrarelativistic heavy nuclei traversing a solid target undergo successive nuclear encounters separated by atomic lattice spacings. At sufficiently high beam energies, Lorentz contraction reduces the proper time between collisions to $\mathcal{O}\left({10}^4\right)\mathrm{fm}/c$ in the center-of-mass frame of the first interaction. We then consider the fragmentation region of this first collision and show that short-lived hadrons produced in this region, with additional Lorentz boost, can reach the next nucleus before decaying. We show that this geometry enables secondary hadron–nucleus collisions involving species that cannot be realized as conventional secondary beams or in subsequent hadron–nucleus interactions in cosmic-ray cascades. For a 2.76-TeV-per-nucleon Pb beam incident on a solid Pb lattice, we determine which forward-produced hadrons can survive to a second interaction, estimate their collision probabilities, and analyze potential observable consequences. In particular, we identify some representative hadrons whose proper lifetimes are of order ${10}^3$ fm/c, e.g., specific mesons (${\eta }^{\prime }$) and heavy-flavor resonances ($J/\psi ,D^{*}\left(2010\right)$), as projectile species that become accessible through this collision space-time geometry. At substantially higher beam energies (for example, with 10-TeV-per-nucleon Pb beam), the survival probabilities are significantly enhanced. This can make even very short-lived hadrons with lifetimes of a few tens of fm [$\mathrm{\Xi }$(1530), $\omega$(782), $\varphi$(1020)] available for this secondary hadron–nucleus collision, providing an additional motivation for future ultrarelativistic fixed-target heavy-ion experiments.

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• Particle & resonance production
• Particle interactions
• QCD in nuclear reactions
• Quantum chromodynamics
• Relativistic heavy-ion collisions
• Strong interaction