Possible mixing between elementary and bound state fields in the $$t\bar{t}$$ production excess at the LHC

Abstract Recent report by CMS Collaboration on the excess of top and anti-top pair production is studied, under the hypothesis of the coexistence of a toponium $$(\eta _t)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>η</mml:mi> <mml:mi>t</mml:mi> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> and an additional elementary field $$(\Psi )$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>Ψ</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> . We examine the scenario where toponium and an additional field are mixed, and consider the plausible scenarios in that case. Two scenarios are examined: one is the minimal model with $$\Psi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Ψ</mml:mi> </mml:math> close to the inert Higgs doublet, and the other is embedded into the two Higgs doublet models (2HDM), where $$\Psi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Ψ</mml:mi> </mml:math> is one of the two Higgs scalars after transforming the basis. The value of each coupling constant is restricted by the Multicritical Point Principle (MPP). Consistency with the data gives constraints on a mixing angle $$\theta \ (-45^\circ \le \theta \le 45^\circ )$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>θ</mml:mi> <mml:mspace/> <mml:mo>(</mml:mo> <mml:mo>-</mml:mo> <mml:msup> <mml:mn>45</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> <mml:mo>≤</mml:mo> <mml:mi>θ</mml:mi> <mml:mo>≤</mml:mo> <mml:msup> <mml:mn>45</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> , with which the mass eigenstate $$\Psi ^\prime $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>Ψ</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:math> contributing to the excess is defined by $$\Psi ^\prime =\Psi \cos \theta + \eta _t\sin \theta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>Ψ</mml:mi> <mml:mo>′</mml:mo> </mml:msup> <mml:mo>=</mml:mo> <mml:mi>Ψ</mml:mi> <mml:mo>cos</mml:mo> <mml:mi>θ</mml:mi> <mml:mo>+</mml:mo> <mml:msub> <mml:mi>η</mml:mi> <mml:mi>t</mml:mi> </mml:msub> <mml:mo>sin</mml:mo> <mml:mi>θ</mml:mi> </mml:mrow> </mml:math> . The obtained results are $$|\theta | \le 13^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mo>|</mml:mo> <mml:mi>θ</mml:mi> <mml:mo>|</mml:mo> </mml:mrow> <mml:mo>≤</mml:mo> <mml:msup> <mml:mn>13</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:mrow> </mml:math> for the minimum scenario, and $$|\theta | \le 1^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mo>|</mml:mo> <mml:mi>θ</mml:mi> <mml:mo>|</mml:mo> </mml:mrow> <mml:mo>≤</mml:mo> <mml:msup> <mml:mn>1</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:mrow> </mml:math> for the second scenario of 2HDM (Type II and Y). We also briefly discuss the comparison with Type I and X.