2026/07/17 by Haipeng An, Hongyi Jiang · 2 citations
#hep-ph #astro-ph.CO
We investigate the production of particles much heavier than the characteristic scale of a cosmological first-order phase transition through collisions of highly boosted bubble walls. Using the scalar order-parameter field, we derive the ultraviolet behavior of its Fourier-space profile for both elastic and inelastic collisions. In the regime χ≡ω2-k2≫ Mh2, we find the universal result ϕ(χ) = -2V^′(2vϕ)χ-2+O(χ-3), implying that the spectral density scales as F(χ)∝ [V^′(2vϕ)]2χ-4. Thus, heavy-particle production is localized near the instant of collision and, at leading order, depends on the scalar potential only through V^′(2vϕ). We verify this behavior using high-precision numerical solutions of the trapping equation, carefully suppressing spectral leakage from the finite integration domain, and obtain agreement over a broad ultraviolet range. We then derive analytical production rates for general heavy-particle thresholds and for fermion pairs, together with their cosmological number density and yield. Finally, we extend the analysis to (3+1) dimensions and incorporate the finite bubble radius, finding an order-one suppression relative to the parallel-wall approximation. Our results revise the ultraviolet scaling used in previous treatments and have direct implications for superheavy dark-matter production and baryogenesis from bubble collisions.