时空非对易性和超高能cosmic ray实验
Spacetime noncommutativity and ultra-high energy cosmic ray experiments
摘要：
如果新的物理学能够将中微子-核子非弹性截面推到标准模型（SM）预测之外的三个数量级，那么超高能（UHE）中微子已经在中微子观测站被观测到了。我们使用这样的约束，以揭示信息的尺度上的非对易性（NC）Lambda_NC在非对易规范场理论（NCGFT），中微子具有树级耦合的光子在一个generation-independent的方式。在我们感兴趣的能量范围内（10^10 ~ 10^11 GeV），θ展开（|theta| ~ 1/Lambda_NC ^2）以及以Lambda_NC表示的微扰展开不再保持其有意义的特征，这迫使我们求助于那些涉及全θ重算的NC场论框架。我们对光子交换过程的贡献进行了数值分析，根据对宇宙成因中微子通量的估计，可以将Lambda_NC的下限确定为高达900（450）TeV左右。另一方面，如果考虑皮埃尔俄歇天文台（PAO）最近的一个令人惊讶的结果，即UHE宇宙射线主要由高度电离的Fe核组成，那么我们的边界会变得更弱，这是由于宇宙中微子通量的减少。尽管如此，我们表明，即使是非常高的比例，在初级UHE宇宙射线的重核，我们的方法仍然可以产生显着的界限Lambda_NC，通常总是高于200 TeV。尽管如此，在这种情况下，人们遇到了Fe分数的最大值，从中可以得出关于Lambda_NC的任何有用信息，从而限定了我们方法的适用性。
英文摘要：
If new physics were capable to push the neutrino-nucleon inelastic cross section three orders of magnitude beyond the standard-model (SM) prediction, then ultra-high energy (UHE) neutrinos would have already been observed at neutrino observatories. We use such a constraint to reveal information on the scale of noncommutativity (NC) Lambda_NC in noncommutative gauge field theories (NCGFT) where neutrinos possess a tree-level coupling to photons in a generation-independent manner. In the energy range of interest (10^10 to 10^11 GeV) the theta-expansion (|theta| ~ 1/Lambda_NC^2) and therefore the perturbative expansion in terms of Lambda_NC retains no longer its meaningful character, forcing us to resort to those NC field-theoretical frameworks involving the full theta-resummation. Our numerical analysis of the contribution to the process coming from the photon exchange, pins impeccably down a lower bound on Lambda_NC to be as high as around up to 900 (450) TeV, depending on the estimates for the cosmogenic neutrino flux. If, on the other hand, one considers a surprising recent result occurred in Pierre Auger Observatory (PAO) data, that UHE cosmic rays are mainly composed of highly-ionized Fe nuclei, then our bounds get weaker, due to the diminished cosmic neutrino flux. Nevertheless, we show that even for the very high fraction of heavy nuclei in primary UHE cosmic rays, our method may still yield remarkable bounds on Lambda_NC, typically always above 200 TeV. Albeit, in this case one encounters a maximal value for the Fe fraction from which any useful information on Lambda_NC can be drawn, delimiting thus the applicability of our method.
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