The European Physical Journal C | 2021
Exploring the low $$\\tan \\beta $$ region of two Higgs doublet models at the LHC
Abstract
<jats:p>Current interpretations of the LHC results on two Higgs doublet models (2HDM) underestimate the sensitivity due to neglecting higher order effects. In this work, we revisit the impact of these effects using the current cross-section times branching ratio limits of the <jats:inline-formula><jats:alternatives><jats:tex-math>$$A\\rightarrow hZ, H \\rightarrow VV$$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:mi>A</mml:mi>\n <mml:mo>→</mml:mo>\n <mml:mi>h</mml:mi>\n <mml:mi>Z</mml:mi>\n <mml:mo>,</mml:mo>\n <mml:mi>H</mml:mi>\n <mml:mo>→</mml:mo>\n <mml:mi>V</mml:mi>\n <mml:mi>V</mml:mi>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$H\\rightarrow hh$$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:mi>H</mml:mi>\n <mml:mo>→</mml:mo>\n <mml:mi>h</mml:mi>\n <mml:mi>h</mml:mi>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula> channels. With a degenerate heavy Higgs mass <jats:inline-formula><jats:alternatives><jats:tex-math>$$m_\\varPhi $$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:msub>\n <mml:mi>m</mml:mi>\n <mml:mi>Φ</mml:mi>\n </mml:msub>\n </mml:math></jats:alternatives></jats:inline-formula>, we find that the LHC searches gain sensitivity to the small <jats:inline-formula><jats:alternatives><jats:tex-math>$$\\tan \\beta $$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:mo>tan</mml:mo>\n <mml:mi>β</mml:mi>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula> region after including loop corrections, even close to <jats:inline-formula><jats:alternatives><jats:tex-math>$$\\cos (\\beta -\\alpha )=0$$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:mo>cos</mml:mo>\n <mml:mo>(</mml:mo>\n <mml:mi>β</mml:mi>\n <mml:mo>-</mml:mo>\n <mml:mi>α</mml:mi>\n <mml:mo>)</mml:mo>\n <mml:mo>=</mml:mo>\n <mml:mn>0</mml:mn>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula> which is not reachable at tree level for all types of 2HDM. For a benchmark point with <jats:inline-formula><jats:alternatives><jats:tex-math>$$m_\\varPhi =300$$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:msub>\n <mml:mi>m</mml:mi>\n <mml:mi>Φ</mml:mi>\n </mml:msub>\n <mml:mo>=</mml:mo>\n <mml:mn>300</mml:mn>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula> GeV, <jats:inline-formula><jats:alternatives><jats:tex-math>$$\\tan \\beta <1.8(1.2)$$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:mo>tan</mml:mo>\n <mml:mi>β</mml:mi>\n <mml:mo><</mml:mo>\n <mml:mn>1.8</mml:mn>\n <mml:mo>(</mml:mo>\n <mml:mn>1.2</mml:mn>\n <mml:mo>)</mml:mo>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula> can be probed for the Type-I(II) 2HDM model for <jats:inline-formula><jats:alternatives><jats:tex-math>$$\\cos (\\beta -\\alpha )=0$$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:mo>cos</mml:mo>\n <mml:mo>(</mml:mo>\n <mml:mi>β</mml:mi>\n <mml:mo>-</mml:mo>\n <mml:mi>α</mml:mi>\n <mml:mo>)</mml:mo>\n <mml:mo>=</mml:mo>\n <mml:mn>0</mml:mn>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula>. When the deviation from <jats:inline-formula><jats:alternatives><jats:tex-math>$$\\cos (\\beta -\\alpha )=0$$</jats:tex-math><mml:math xmlns:mml= http://www.w3.org/1998/Math/MathML >\n <mml:mrow>\n <mml:mo>cos</mml:mo>\n <mml:mo>(</mml:mo>\n <mml:mi>β</mml:mi>\n <mml:mo>-</mml:mo>\n <mml:mi>α</mml:mi>\n <mml:mo>)</mml:mo>\n <mml:mo>=</mml:mo>\n <mml:mn>0</mml:mn>\n </mml:mrow>\n </mml:math></jats:alternatives></jats:inline-formula> is larger, the region for which current searches have exclusion potential becomes larger.</jats:p>