Surprisingly, the contribution to the cosmic opacity to UHE ($E>10^{18} \, \rm eV$) $\gamma$-rays has been systematically computed so far for the $\gamma \gamma \to e^+e^-$ and $\gamma \gamma \to e^+ e^- e^+ e^-$ processes alone. We go a step further by systematically evaluating the additional opacity brought about by other leptons and hadrons. We find that the dominant channels are those leading to the production of $\mu^{\pm}$ and hadrons (mainly $\pi^{\pm}$, $\pi^0$, $K^{\pm}$, $K^0$, $\eta$). For nearly the GZK radius, the photon survival probability becomes smaller by about a factor of two with respect to current estimates.

中文翻译：

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用轻子和强子产生估计超高能光子的γγ吸收

令人惊讶的是，到目前为止，已经系统地计算了对 UHE ($E>10^{18} \, \rm eV$) $\gamma$ 射线的贡献，用于 $\gamma \gamma \to e^+ e^-$ 和 $\gamma \gamma \to e^+ e^- e^+ e^-$ 单独处理。我们更进一步，系统地评估了其他轻子和强子带来的额外不透明度。我们发现主导通道是那些导致产生 $\mu^{\pm}$ 和强子的通道（主要是 $\pi^{\pm}$, $\pi^0$, $K^{\pm} $、$K^0$、$\eta$）。对于接近 GZK 半径，相对于当前估计，光子存活概率变小了大约两倍。