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arXiv 1502.01884astro-ph.COhep-ph
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热WIMP质量和湮灭截面的CMB约束

CMB Constraints On The Thermal WIMP Mass And Annihilation Cross Section

Gary Steigman

摘要:

热遗迹,通常被称为弱相互作用大质量粒子(WIMP),是在宇宙早期演化过程中产生的粒子,其现在(遗迹)的丰度仅取决于它的质量和它的热平均湮灭截面(湮灭率因子)σ vann。目前的观测限制,不存在这种影响提供了边界的质量和湮灭截面的遗迹粒子,可能,但不一定是暗物质的候选人。对于暗物质候选者WIMP,CMB约束为湮灭截面设定了一个上限,导致其质量的下限取决于WIMP是否是其自身的反粒子。对于自共轭WIMP,m_min = 50fGeV,其中f是电磁能量效率因子。对于非自共轭的WIMP,最小质量是两倍大。对于暗物质密度的次主导分量WIMP,其质量没有约束,并且由CMB施加的湮灭截面的上限转变为湮灭截面的下限。这些结果概述和量化这里使用最新的CMB约束的稳定,对称(粒子和反粒子的数量相等),WIMP的湮灭是s波为主,和粒子,或不是,自己的反粒子。

英文摘要:

A thermal relic, often referred to as a weakly interacting massive particle (WIMP), is a particle produced during the early evolution of the Universe whose present (relic) abundance depends only on its mass and its thermally averaged annihilation cross section (annihilation rate factor) sigma*v_ann. Late time WIMP annihilation has the potential to affect the cosmic microwave background (CMB) power spectrum. Current observational constraints on the absence of such effects provide bounds on the mass and the annihilation cross section of relic particles that may, but need not be dark matter candidates. For a WIMP that is a dark matter candidate, the CMB constraint sets an upper bound to the annihilation cross section, leading to a lower bound to its mass that depends on whether or not the WIMP is its own antiparticle. For a self-conjugate WIMP, m_min = 50f GeV, where f is an electromagnetic energy efficiency factor. For a non self-conjugate WIMP, the minimum mass is a factor of two larger. For a WIMP that is a subdominant component of the dark matter density there is no bound on its mass and the upper bound to its annihilation cross section imposed by the CMB transforms into a lower bound to its annihilation cross section. These results are outlined and quantified here using the latest CMB constraints for a stable, symmetric (equal number of particles and antiparticles), WIMP whose annihilation is s-wave dominated, and for particles that are, or are not, their own antiparticle.

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