Three exceptions in the calculation of relic abundances.
Three exceptions in the calculation of relic abundances.
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DOI：
10.1103/physrevd.43.3191
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发表时间：
1991-05
期刊：
影响因子：
--
通讯作者：
K. Griest;D. Seckel
中科院分区：
文献类型：
--
作者：
K. Griest;D. Seckel
通过跟踪基本粒子在早期宇宙中的湮灭和冻结来计算它们的残余丰度，已经成为讨论粒子暗物质候选者的重要和标准工具。我们发现文献中出现了三种计算遗迹丰度的标准方法失败的情况。第一种情况发生在另一个粒子的质量与残余粒子接近，并且与它共享一个量子数，一个例子是轻夸克与中性伴子暗物质。附加粒子必须包含在反应网络中，因为它的湮灭可以控制残余物的丰度。第二种情况发生在遗迹粒子接近质量阈值时。以前，湮灭成比遗迹粒子重的粒子被认为是运动学禁止的，但我们表明，如果质量差是\ensuremath{\sim}5- 15%，这些“禁止”通道可以主导横截面，并确定遗迹丰度。第三种情况发生在湮灭发生在横截面的极点附近。对热平均和冻结后的湮灭的适当处理表明，由极点引起的遗迹丰度的下降并不像以前认为的那样尖锐或深刻。
The calculation of relic abundances of elementary particles by following their annihilation and freeze-out in the early Universe has become an important and standard tool in discussing particle dark-matter candidates. We find three situations, all occurring in the literature, in which the standard methods of calculating relic abundances fail. The first situation occurs when another particle lies near in mass to the relic particle and shares a quantum number with it. An example is a light squark with neutralino dark matter. The additional particle must be included in the reaction network, since its annihilation can control the relic abundance. The second situation occurs when the relic particle lies near a mass threshold. Previously, annihilation into particles heavier than the relic particle was considered kinematically forbidden, but we show that if the mass difference is \ensuremath{\sim}5-15%, these "forbidden" channels can dominate the cross section and determine the relic abundance. The third situation occurs when the annihilation takes place near a pole in the cross section. Proper treatment of the thermal averaging and the annihilation after freeze-out shows that the dip in relic abundance caused by a pole is not nearly as sharp or deep as previously thought.