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Unitarity constraints in triplet extensions beyond the large s limit

Krauss, Manuel E.; Staub, Florian 1,2
1 Institut für Theoretische Physik (ITP), Karlsruher Institut für Technologie (KIT)
2 Institut für Kernphysik (IKP), Karlsruher Institut für Technologie (KIT)


Triplet extensions are attractive alternatives to the standard model (SM) of particle physics. While models with only one triplet are highly constrained by electroweak precision observables, this is not necessarily the case once several triplets are present as in the Georgi-Machacek model. As in all other BSM models, the parameter space of triplet extensions is constrained by the condition that perturbative unitarity is not violated. For this purpose, limits on the eigenvalues of the scalar 2→2 scattering matrix are set. It is very common in the BSM literature that the scattering matrix is calculated under one crucial assumption: the scattering energy s is so large that only point interactions involving quartic couplings provide non-negligible contributions. However, it is not given that this approximation is always valid—in fact, diagrams involving propagators can play an important role. We discuss the examples of (i) the SM model extended by a real triplet, (ii) the Y=1 triplet extension of the SM, and (iii) the Georgi-Machacek model, how the tree-level unitarity constraints are affected once the large s approximation is given up. For all models we find that the impact of (effective) cubic couplings can be crucial.

Verlagsausgabe §
DOI: 10.5445/IR/1000085354
Veröffentlicht am 16.08.2018
DOI: 10.1103/PhysRevD.98.015041
Zitationen: 13
Web of Science
Zitationen: 13
Zitationen: 12
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Kernphysik (IKP)
Institut für Theoretische Physik (ITP)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2018
Sprache Englisch
Identifikator ISSN: 2470-0010, 2470-0029
KITopen-ID: 1000085354
HGF-Programm 51.03.06 (POF III, LK 01) Theoretische Astroteilchenphysik
Erschienen in Physical review / D
Verlag American Physical Society (APS)
Band 98
Heft 1
Seiten Article No. 015041
Bemerkung zur Veröffentlichung Gefördert durch SCOAP3
Vorab online veröffentlicht am 31.07.2018
Nachgewiesen in Web of Science
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