Exploring sizable triple Higgs couplings in the 2HDM
F. Arco, S. Heinemeyer, M. J. Herrero
Abstract
Abstract An important task at future colliders is the measurement of the triple Higgs coupling. Depending on its size relative to the Standard Model (SM) value, certain collider options result in a higher experimental accuracy. Within the framework of Two Higgs Doublet Models (2HDM) types I and II we investigate the allowed ranges for all triple Higgs couplings involving at least one light, SM-like Higgs boson. We take into account theoretical constraints (unitarity, stability), experimental constraints from direct Higgs-boson searches, measurements of the SM-like Higgs-boson properties, flavor observables and electroweak precision data. We find that the SM-type triple Higgs coupling w.r.t. its SM value, $$\lambda _{hhh}/\lambda _{\mathrm {SM}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mi>hhh</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mi>λ</mml:mi> <mml:mi>SM</mml:mi> </mml:msub> </mml:mrow> </mml:math> , can range between $$\sim -0.5$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mo>-</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:math> and $$\sim 1.5$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>1.5</mml:mn> </mml:mrow> </mml:math> . Depending on which value is realized, the HL-LHC can compete with, or is clearly inferior to the ILC. We find the coupling $$\lambda _{hhH}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mi>hhH</mml:mi> </mml:mrow> </mml:msub> </mml:math> between $$\sim -1.5$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mo>-</mml:mo> <mml:mn>1.5</mml:mn> </mml:mrow> </mml:math> and $$\sim 1.5$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>1.5</mml:mn> </mml:mrow> </mml:math> . Triple Higgs couplings involving two heavy Higgs bosons, $$\lambda _{hHH}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mi>hHH</mml:mi> </mml:mrow> </mml:msub> </mml:math> , $$\lambda _{hAA}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mi>hAA</mml:mi> </mml:mrow> </mml:msub> </mml:math> and $$\lambda _{hH^+H^-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mi>h</mml:mi> <mml:msup> <mml:mi>H</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>H</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:msub> </mml:math> can reach values up to $${{\mathcal {O}}}(10)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>O</mml:mi> <mml:mo>(</mml:mo> <mml:mn>10</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> , roughly independent of the 2HDM type. This can lead to potentially strongly enhanced production of two Higgs-bosons at the HL-LHC or high-energy $$e^+e^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> colliders.