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arXiv 0707.4200hep-ph
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QCD对QED真空极化的修正

QCD Corrections to QED Vacuum Polarization

P. Castelo Ferreira, J. Dias de Deus

摘要:

我们计算了背景磁场中真空极化对QED计算的QCD修正。形式上,虚拟$e\bar{e}$环路的图与虚拟$q\bar{q}$环路的图相同。然而,由于限制,或随着$p^2$的减少,$α_s$的增长,不允许直接计算该图。在大的$p^2$,我们认为虚拟的$q\bar{q}$图,在中间区域,我们讨论的夸克凝聚$\left< q\bar{q}\right>$的贡献的作用,并在低能量极限,我们认为$π^0$,以及带电的π $π^+π^-$环。虽然这些效应似乎超出了光子-光子实验室实验的测量精度,但它们可能与PDMATHAMT射线爆发传播有关。特别是,从星系的中心(8.5千秒差距)的排放量,我们表明,中性赝标量π $π_0$和光子之间的混合呈现偏离幂律谱的$TeV$范围。对于标量夸克凝聚,$\left< q\bar{q} right>$和虚$q\bar{q}$环只与非常高的辐射密度$\sim 300 MeV/fm^3$和非常强的$\sim 10^{14} T$级磁场有关。

英文摘要:

We compute QCD corrections to QED calculations for vacuum polarization in background magnetic fields. Formally, the diagram for virtual $e\bar{e}$ loops is identical to the one for virtual $q\bar{q}$ loops. However due to confinement, or to the growth of $α_s$ as $p^2$ decreases, a direct calculation of the diagram is not allowed. At large $p^2$ we consider the virtual $q\bar{q}$ diagram, in the intermediate region we discuss the role of the contribution of quark condensates $\left< q\bar{q}\right>$ and at the low-energy limit we consider the $π^0$, as well as charged pion $π^+π^-$ loops. Although these effects seem to be out of the measurement accuracy of photon-photon laboratory experiments they may be relevant for $γ$-ray burst propagation. In particular, for emissions from the center of the galaxy (8.5 kpc), we show that the mixing between the neutral pseudo-scalar pion $π_0$ and photons renders a deviation from the power-law spectrum in the $TeV$ range. As for scalar quark condensates $\left< q\bar{q} right>$ and virtual $q\bar{q}$ loops are relevant only for very high radiation density $\sim 300 MeV/fm^3$ and very strong magnetic fields of order $\sim 10^{14} T$.

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