Refined bounds on MeV-scale thermal dark sectors from BBN and the CMB
Refined bounds on MeV-scale thermal dark sectors from BBN and the CMB
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DOI：
10.1088/1475-7516/2020/01/004
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发表时间：
2019-10
影响因子：
6.4
通讯作者：
N. Sabti;J.B.G. Alvey;M. Escudero;M. Fairbairn;D. Blas
中科院分区：
文献类型：
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作者：
N. Sabti;J.B.G. Alvey;M. Escudero;M. Fairbairn;D. Blas
与标准模型等离子体热耦合的新的轻态改变了宇宙的膨胀历史，并影响了原始轻元素的合成。在这项工作中，我们进行了详尽和精确的分析，大爆炸核合成（BBN）和宇宙微波背景（CMB）观测的MeV级BSM粒子的影响。我们发现BBN观测在2σ处设定了热暗物质质量的下限mχ > 0.4 MeV。这种束缚与粒子的自旋和内部自由度的数量、湮灭是s波还是p波以及湮灭的终态无关。此外，我们表明，目前的BBN加上CMB观测限制纯粹亲电和亲中微子BSM物种有一个质量，在2σ，mχ > 3.7 MeV。我们探索了未来BBN测量的范围，并表明即将到来的CMB任务应该将轻BSM热态的界限提高到m x>（10−15）MeV。最后，我们表明，非常轻的BSM物种热耦合到SM等离子体是非常不利的，目前的宇宙学观测。
New light states thermally coupled to the Standard Model plasma alter the expansion history of the Universe and impact the synthesis of the primordial light elements. In this work, we carry out an exhaustive and precise analysis of the implications of MeV-scale BSM particles in Big Bang Nucleosynthesis (BBN) and for Cosmic Microwave Background (CMB) observations. We find that BBN observations set a lower bound on the thermal dark matter mass of mχ > 0.4 MeV at 2σ. This bound is independent of the spin and number of internal degrees of freedom of the particle, of the annihilation being s-wave or p-wave, and of the annihilation final state. Furthermore, we show that current BBN plus CMB observations constrain purely electrophilic and neutrinophilic BSM species to have a mass, mχ > 3.7 MeV at 2σ. We explore the reach of future BBN measurements and show that upcoming CMB missions should improve the bounds on light BSM thermal states to mχ > (10−15) MeV. Finally, we demonstrate that very light BSM species thermally coupled to the SM plasma are highly disfavoured by current cosmological observations.