分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-15
摘要： In split-supersymmetry (split-SUSY), gluino is a metastable particle and thus can freeze out in the early universe. The late decay of such a long-life gluino into the lightest supersymmetric particle (LSP) may provide much of the cosmic dark-matter content. In this work, assuming the LSP is gravitino produced from the late decay of the metastable gluino, we examine the Wilkinson microwave anisotropy probe (WMAP) dark-matter constraints on the gluino mass. We find that to provide the full abundance of dark matter, the gluino must be heavier than about 14 TeV and thus not accessible at the CERN large hadron collider (LHC).
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-15
摘要： In the Affleck-Dine mechanism of baryogenesis, nontopological solitons called Q-balls can be formed. In this work we propose that such Q-balls decay during the BBN era and study the cosmological consequence of such late decays. We find that the late-decaying baryonic Q-balls with lifetime of about 10(3) s can provide a new developing mechanism for the BBN through a rolling baryon-to-photon ratio eta, which can naturally explain the discrepancy of the BBN prediction with the WMAP data on Li-7 abundance. For the late-decaying leptonic Q-balls with lifetime of about 10(6) s, we find that their decay product, gravitinos, can serve as a dark matter candidate and give an explanation for the approximate equality of dark and baryon matter densities. (C) 2004 Elsevier B.V. All rights reserved.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-15
摘要： The heavy gravitino in the minimal supergravity (mSUGRA) models is likely to be the lightest supersymmetric particle (LSP). Produced from the late decays of the metastable weakly interacting massive particles (WIMPS) such as the lightest neutralinos, the stable gravitinos can be plausible candidates for the cold dark matter in the universe. Such gravitino dark matter can naturally evade the current detection experiments due to its superweak couplings. However, this scenario must be subjected to the constraints from the big bang nucleosynthesis (BBN) predictions for light element abundances as well as the Wilkinson microwave anisotropy probe (WMAP) data for the relic density. Assuming the popular case in which the lightest neutralino is the next-to-lightest supersymmetric particle (NLSP), we find that requiring BBN predictions for light element abundances to agree with the WMAP data can impose upper and lower mass bounds on both the gravitino LSP and the neutralino NLSP. A scan over the mSUGRA parameter space, subjected to the BBN constraints, the WMAP data and the b --> sgamma bounds, shows that the low tan beta (less than or similar to 40) region as well as the region accessible at the CERN Large Hadron Collider (LHC) will be severely constrained. Such stringent constraints on the parameter space might be instructive for testing this scenario in future collider experiments.
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