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Collider Signatures of Goldstone Bosons

  • Cheung, Kingman
  • Keung, Wai-Yee
  • Yuan, Tzu-Chiang
Published Article
Publication Date
Dec 17, 2013
Submission Date
Aug 20, 2013
DOI: 10.1103/PhysRevD.89.015007
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Recently Weinberg suggested that Goldstone bosons arising from the spontaneous breakdown of some global hidden symmetries can interact weakly in the early Universe and account for a fraction of the effective number of neutrino species N_eff, which has been reported persistently 1 \sigma away from its expected value of three. In this work, we study in some details a number of experimental constraints on this interesting idea based on the simplest possibility of a global U(1), as studied by Weinberg. We work out the decay branching ratios of the associated light scalar field $\sigma$ and suggest a possible collider signature at the Large Hadron Collider (LHC). In some corners of the parameter space, the scalar field \sigma can decay into a pair of pions with a branching ratio of order O(1)% while the rest is mostly a pair of Goldstone bosons. The collider signature would be gluon fusion into the standard model Higgs boson gg -> H or associated production with a W gauge boson q q'-bar -> H W, followed by H -> \sigma \sigma -> (\pi\pi) (\alpha\alpha), where \alpha is the Goldstone boson.


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