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Neutralinos, Big Bang Nucleosynthesis and 6Li in Low-Metallicity Stars.pdf

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Neutralinos, Big Bang Nucleosynthesis and 6Li in Low-Metallicity Stars

a r X i v : a s t r o - p h / 0 4 0 5 5 8 3 v 2 2 2 N o v 2 0 0 4 Neutralinos, Big Bang Nucleosynthesis and 6Li in Low-Metallicity Stars Karsten Jedamzik Laboratoire de Physique Mathe?mathique et The?orique, C.N.R.S., Universite? de Montpellier II, 34095 Montpellier Cedex 5, France The synthesis of 6Li during the epoch of Big Bang nucleosynthesis (BBN) due to residual anni- hilation of dark matter particles is considered. By comparing the predicted 6Li to observations of this isotope in low-metallicity stars, generic constraints on s-wave dark matter annihilation rates into quarks, gauge bosons, and Higgs bosons are derived. It may be shown that, for example, wino dark matter in anomaly-mediated SUSY breaking scenarios with masses mχ ～ 250GeV or light neutralinos with mχ ～ 20GeV annihilating into light quarks are, taken face value, ruled out. These constraints may only be circumvented if significant 6Li depletion has occurred in all three low-metallicity stars in which this isotope has been observed to date. In general, scenarios invoking non-thermally generated neutralinos with enhanced annihilation rates for a putative explanation of cosmic ray positron or galactic center as well as diffuse background gamma-ray signals by present- day neutralino annihilation will have to face a stringent 6Li overproduction problem. On the other hand, it is possible that 6Li as observed in low-metallicity stars is entirely due to residual dark matter annihilation during BBN, even for neutralinos undergoing a standard thermal freeze-out. The nature of the ubiquitous cosmological dark mat- ter is one of the outstanding questions in cosmology. Though there exist a multitude of proposed candidates, much consideration has been given to the supersymmet- ric (SUSY) neutralino, provided it is the lightest super- symmetric particle (LSP). SUSY extensions of the stan- dard model are particularly successful in overcoming a number of shortfalls of the standard model, such as the hierarc