Observability of 2HDM charged Higgs boson in a misaligned scenario

The Large Hadron Collider precision measurement of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msub><a:mrow><a:mi>h</a:mi></a:mrow><a:mrow><a:mn>125</a:mn></a:mrow></a:msub></a:mrow></a:math> properties suggests that a misaligned two-Higgs-doublet model (2HDM) type I is preferred among other types of the model. In this analysis, a lepton collider potential for charged Higgs boson observation is evaluated and compared with HL-LHC expectations. We focus on <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:msup><c:mrow><c:mi>H</c:mi></c:mrow><c:mrow><c:mo>±</c:mo></c:mrow></c:msup><c:mo stretchy="false">→</c:mo><c:msup><c:mrow><c:mi>W</c:mi></c:mrow><c:mrow><c:mo>±</c:mo></c:mrow></c:msup><c:msub><c:mrow><c:mi>h</c:mi></c:mrow><c:mrow><c:mn>125</c:mn></c:mrow></c:msub></c:mrow></c:math> decay which is exclusively activated in misaligned scenario. An event analysis including fast detector simulation is performed, and it is shown that some parts of the parameter space which are out of HL-LHC reach can be probed by a high-energy lepton collider with signal significance exceeding <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mn>2</f:mn><f:mi>σ</f:mi></f:math> and <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mn>5</h:mn><h:mi>σ</h:mi></h:math> for exclusion or discovery. The region with highest sensitivity is in the middle range charged Higgs boson mass, i.e., <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mn>350</j:mn><j:mo><</j:mo><j:msub><j:mi>m</j:mi><j:msup><j:mi>H</j:mi><j:mo>±</j:mo></j:msup></j:msub><j:mo><</j:mo><j:mn>450</j:mn><j:mtext> </j:mtext><j:mtext> </j:mtext><j:mi>GeV</j:mi></j:math> and <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mi>tan</l:mi><l:mi>β</l:mi><l:mo>≳</l:mo><l:mn>4</l:mn></l:math> at nonzero <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mi>cos</n:mi><n:mo stretchy="false">(</n:mo><n:mi>β</n:mi><n:mo>−</n:mo><n:mi>α</n:mi><n:mo stretchy="false">)</n:mo></n:math> values.