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arXiv 0810.5557hep-phastro-ph
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狄拉克暗物质的有效理论

An Effective Theory of Dirac Dark Matter

Roni Harnik, Graham D. Kribs

摘要:

一个稳定的狄拉克费米子与四个费米子相互作用的轻子抑制的规模为λ ~ 1 TeV的显示,提供了一个可行的候选暗物质。热遗迹丰度符合宇宙学,而核反冲直接检测界限自动避免在没有(大)耦合夸克。早期宇宙的湮灭截面与我们银河系附近的湮灭是一样的。这使得狄拉克费米子暗物质自然地解释了PAMELA观测到的正电子比过剩,并给出了目前天体物理学的不确定性。我们使用Galprop程序的信号和背景的传播,我们详细讨论了传播参数,更重要的是,注入光谱所产生的不确定性。费米/GLAST有机会看到狄拉克费米子质量的伽马射线谱中的一个特征。ATIC/PPB-BETS观测到的过量也可以用重的狄拉克暗物质来解释。一个具有Dirac bino的超对称模型提供了一个可行的有效理论UV模型。轻子算符的优势,以及由此观测到的过量正电子而非反质子,自然可以用与方夸克相比,轻子的超荷大且质量低来解释。最小化升压因子意味着右手选择器是最轻的slepton,这是我们模型的特征。质量小于几百GeV的超电子(或超光子)是一个不可避免的结果,等待大型强子对撞机的发现。

英文摘要:

A stable Dirac fermion with four-fermion interactions to leptons suppressed by a scale Lambda ~ 1 TeV is shown to provide a viable candidate for dark matter. The thermal relic abundance matches cosmology, while nuclear recoil direct detection bounds are automatically avoided in the absence of (large) couplings to quarks. The annihilation cross section in the early Universe is the same as the annihilation in our galactic neighborhood. This allows Dirac fermion dark matter to naturally explain the positron ratio excess observed by PAMELA with a minimal boost factor, given present astrophysical uncertainties. We use the Galprop program for propagation of signal and background; we discuss in detail the uncertainties resulting from the propagation parameters and, more importantly, the injected spectra. Fermi/GLAST has an opportunity to see a feature in the gamma-ray spectrum at the mass of the Dirac fermion. The excess observed by ATIC/PPB-BETS may also be explained with Dirac dark matter that is heavy. A supersymmetric model with a Dirac bino provides a viable UV model of the effective theory. The dominance of the leptonic operators, and thus the observation of an excess in positrons and not in anti-protons, is naturally explained by the large hypercharge and low mass of sleptons as compared with squarks. Minimizing the boost factor implies the right-handed selectron is the lightest slepton, which is characteristic of our model. Selectrons (or sleptons) with mass less than a few hundred GeV are an inescapable consequence awaiting discovery at the LHC.

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