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Buchalla, Gerhard; Cata, Oscar und Krause, Claudius (2014): Complete electroweak chiral Lagrangian with a light Higgs at NLO. In: Nuclear Physics B, Vol. 880: S. 552-573




We consider the Standard Model, including a light scalar boson h, as an effective theory at the weak scale v = 246 GeV of some unknown dynamics of electroweak symmetry breaking. This dynamics may be strong, with h emerging as a pseudo-Goldstone boson. The symmetry breaking scale Λ is taken to be at 4 π v or above. We review the leading-order Lagrangian within this framework, which is nonrenormalizable in general. A chiral Lagrangian can then be constructed based on a loop expansion. A systematic power counting is derived and used to identify the classes of counterterms that appear at one loop order. With this result the complete Lagrangian is constructed at next-to-leading order, O ( v 2 / Λ 2 ) . This Lagrangian is the most general effective description of the Standard Model containing a light scalar boson, in general with strong dynamics of electroweak symmetry breaking. Scenarios such as the {SILH} ansatz or the dimension-6 Lagrangian of a linearly realized Higgs sector can be recovered as special cases.