Speaker
Description
Accurate prediction of beam-beam-induced backgrounds, particularly incoherent electron-positron pair production, is essential for validating the occupancy budgets for the innermost tracking (vertex) detector at FCC-ee. These predictions currently rely on GUINEA-PIG, a mature, specialized particle in cell (PIC) code simulating a single beam-beam pass. WarpX, a GPU-accelerated, 3D Poisson solver PIC code, has recently been benchmarked against GUINEA-PIG and Xsuite across a broad range of collider scenarios, including the FCC-ee Z and tt̄ operating points [1,2]. For both cases, the two codes agree to within 1.3% in total luminosity per bunch crossing relative to the geometric expectation, with convergence of this metric requiring resolution of the transverse beam size at the interaction point with several grid cells (Nᵧ ≥ 2048 for FCC-ee Z) [1]. WarpX production runs for these cases complete in the order of a few minutes on a single GPU node, versus several hours on a single CPU for GUINEA-PIG, at comparable physical fidelity. Building on this validated foundation, we shift focus from integrated luminosity to the differential, low-angle incoherent-pair distribution of the deflection ridge in the (pT, θ) plane, which most directly governs vertex-detector occupancy. We compare GUINEA-PIG and WarpX across all three FCC-ee operating points and assess agreement in the region most relevant to detector background estimates. We also outline next steps toward a full WarpX-to-detector-simulation pipeline.
[1] A. Formenti, R. Lehe, A. Huebl, S. S. Bulanov, A. Myers, J. Osterhoff, J.-L. Vay, S. Gessner, P. Kicsiny, A. Kinderman, B. Nguyen, and J. Park, "A modern particle-in-cell code for beam-beam simulations of future colliders," in preparation (2026).
[2] P. Kicsiny, "WarpX: a massively parallel PIC framework for future colliders," poster presented at FCC Week 2026, SLAC National Accelerator Laboratory (2026).
