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arXiv 1503.08213hep-phastro-ph.COastro-ph.HE
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银河系中心gamma ray过剩的多介质模型

Multimediator models for the galactic center gamma ray excess

James M. Cline, Grace Dupuis, Zuowei Liu, Wei Xue

摘要:

来自银河系中心的过量GeV级伽马射线的初步证据已经得到了几个小组的证实,包括费米合作小组,该观测是基于其数据。暗物质湮灭成标准模型粒子已被证明能很好地拟合各种末态粒子的信号,但通用模型与直接探测的约束不一致。暗物质湮灭为介质,随后衰变的模型约束较少。我们执行全球适合这样的模型最近的数据,允许分支分数到所有可能的费米子最终状态变化。最佳拟合模型,包括AMS-02实验的约束(以及反质子比),要求主要分支到μ子,并含有$b$夸克的$\sim 10-20\%$混合物,而不含其他种类。这表明有两个标量介质与希格斯粒子混合的模型,其质量与这种衰变模式一致。因此,衰变为$μ^+μ^-$的标量必须比$2m_τ\cong 3.6$ GeV轻。如此小的质量可以导致索末菲增强,这有助于解释为什么最佳拟合湮灭截面大于热遗迹密度所需的值。对于轻介质质量$\sim (0.2-2)$ GeV,它也可以自然地导致弹性DM自相互作用在正确的水平,以解决小结构形成的差异,如预测的碰撞冷暗物质。

英文摘要:

Tentative evidence for excess GeV-scale gamma rays from the galactic center has been corroborated by several groups, including the Fermi collaboration, on whose data the observation is based. Dark matter annihilation into standard model particles has been shown to give a good fit to the signal for a variety of final state particles, but generic models are inconsistent with constraints from direct detection. Models where the dark matter annihilates to mediators that subsequently decay are less constrained. We perform global fits of such models to recent data, allowing branching fractions to all possible fermionic final states to vary. The best fit models, including constraints from the AMS-02 experiment (and also antiproton ratio), require branching primarily to muons, with a $\sim 10-20\%$ admixture of $b$ quarks, and no other species. This suggests models in which there are two scalar mediators that mix with the Higgs, and have masses consistent with such a decay pattern. The scalar that decays to $μ^+μ^-$ must therefore be lighter than $2m_τ\cong 3.6$ GeV. Such a small mass can cause Sommerfeld enhancement, which is useful to explain why the best-fit annihilation cross section is larger than the value needed for a thermal relic density. For light mediator masses $\sim (0.2-2)$ GeV, it can also naturally lead to elastic DM self-interactions at the right level for addressing discrepancies in small structure formation as predicted by collisionless cold dark matter.

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