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Published February 1, 2008 | Published
Journal Article Open

CERN LHC phenomenology of an extended standard model with a real scalar singlet


Gauge singlet extensions of the standard model (SM) scalar sector may help remedy its theoretical and phenomenological shortcomings while solving outstanding problems in cosmology. Depending on the symmetries of the scalar potential, such extensions may provide a viable candidate for the observed relic density of cold dark matter or a strong first order electroweak phase transition needed for electroweak baryogenesis. Using the simplest extension of the SM scalar sector with one real singlet field, we analyze the generic implications of a singlet-extended scalar sector for Higgs boson phenomenology at the Large Hadron Collider (LHC). We consider two broad scenarios: one in which the neutral SM Higgs and singlet mix and the other in which no mixing occurs and the singlet can be a dark matter particle. For the first scenario, we analyze constraints from electroweak precision observables and their implications for LHC Higgs phenomenology. For models in which the singlet is stable, we determine the conditions under which it can yield the observed relic density, compute the cross sections for direct detection in recoil experiments, and discuss the corresponding signatures at the LHC.

Additional Information

© 2008 The American Physical Society. (Received 9 July 2007; published 19 February 2008) We thank H. Baer, D. Cline, and W-Y. Keung for helpful discussions. We also thank Shinichiro Ando and Sean Tulin for technical discussions related to the scalar loop calculations and J. Kile and J. Erler for assistance with the GAAP code. This work was supported in part by the U.S. Department of Energy under grants No. DE-FG02-95ER40896 and No. DE-FG02-05ER41361, by the Wisconsin Alumni Research Foundation, by the Friends of the IAS, and by the National Science Foundation grants No. PHY-0503584 and No. PHY-PHY-0555674.

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