Universal Geometric Scaling in Cosmic Ray Spallation: Evidence of a Dynamical Causal Horizon from AMS-02

TL;DR

This paper presents evidence that cosmic ray spallation at high energies exhibits universal geometric scaling, suggesting a causal horizon and thermal bath effect that supersede traditional microscopic models.

Contribution

It introduces a macroscopic geometric framework explaining high-energy cosmic ray flux ratios as converging to an energy-independent plateau, supported by theoretical and observational evidence.

Findings

Secondary-to-secondary flux ratios converge to energy-independent plateaus at high energies.

A causal horizon with an effective Unruh temperature explains the observed scaling.

The asymptotic scale matches the nuclear liquid-gas phase transition limit.

Abstract

The interpretation of high-precision cosmic ray spectra is fundamentally bottlenecked by uncertainties in fragmentation cross-sections. Traditional kinematic models, driven by phase-space expansions, typically predict complex, energy-dependent evolutions. However, AMS-02 measurements reveal that at high rigidities ($R > 30$~GV), secondary-to-secondary flux ratios (Li/B, Be/B, and Li/Be) strictly converge to energy-independent plateaus. To understand this anomaly, we explore a macroscopic geometric framework. The ultra-relativistic spallation of a target nucleus snaps residual strong-interaction flux tubes, inducing an extreme deceleration on the remnant. Using a semi-microscopic estimation based on the Woods-Saxon potential and pion exchange, we suggest this dynamically generates a causal horizon with an effective Unruh temperature $T_U \approx 5.6-5.8$~MeV. Utilizing the Be/B ratio as an absolute calibration channel, we extract an asymptotic scale of $6.08$~MeV, remarkably consistent with our theoretical estimation and the established nuclear liquid-gas phase transition limit. Subsequent blind tests on Lithium ratios demonstrate a universal zero-slope convergence, providing compelling evidence that a constant geometric thermal bath effectively supersedes complex microscopic kinematics at high energies.