Search for charged Higgs bosons through vectorlike top quark pair production at the LHC

Abstract

We investigate the discovery prospects for a vectorlike top partner (VLT) in the type-II two-Higgs-doublet model (2HDM-II) extended by a vectorlike quark doublet (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>T</a:mi><a:mi>B</a:mi></a:math>) at the 14 TeV LHC. The study focuses on the pair production process <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>p</c:mi><c:mi>p</c:mi><c:mo stretchy="false">→</c:mo><c:mi>T</c:mi><c:mover accent="true"><c:mi>T</c:mi><c:mo stretchy="false">¯</c:mo></c:mover><c:mo stretchy="false">→</c:mo><c:mi>b</c:mi><c:msup><c:mi>H</c:mi><c:mo>+</c:mo></c:msup><c:mover accent="true"><c:mi>b</c:mi><c:mo stretchy="false">¯</c:mo></c:mover><c:msup><c:mi>H</c:mi><c:mo>−</c:mo></c:msup><c:mo stretchy="false">→</c:mo><c:mi>b</c:mi><c:mo stretchy="false">(</c:mo><c:mi>t</c:mi><c:mi>b</c:mi><c:mo stretchy="false">)</c:mo><c:mover accent="true"><c:mi>b</c:mi><c:mo stretchy="false">¯</c:mo></c:mover><c:mo stretchy="false">(</c:mo><c:mover accent="true"><c:mi>t</c:mi><c:mo stretchy="false">¯</c:mo></c:mover><c:mi>b</c:mi><c:mo stretchy="false">)</c:mo></c:math>, yielding fully hadronic final states characterized by high <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:mi>b</t:mi></t:math>-jet multiplicity. Two analysis strategies are employed, requiring at least four or five <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mi>b</v:mi></v:math>-tagged jets (<x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:mrow><x:mn>4</x:mn><x:mi>b</x:mi></x:mrow></x:math> and <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:mrow><z:mn>5</z:mn><z:mi>b</z:mi></z:mrow></z:math>), to exploit the signal topology. Assuming a charged Higgs mass of <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"><bb:msub><bb:mi>m</bb:mi><bb:msup><bb:mi>H</bb:mi><bb:mo>±</bb:mo></bb:msup></bb:msub><bb:mo>∼</bb:mo><bb:mn>600</bb:mn><bb:mtext> </bb:mtext><bb:mtext> </bb:mtext><bb:mi>GeV</bb:mi></bb:math> and a systematic uncertainty of <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:mi>δ</db:mi><db:mo>=</db:mo><db:mn>5</db:mn><db:mo>%</db:mo></db:math>, the <fb:math xmlns:fb="http://www.w3.org/1998/Math/MathML" display="inline"><fb:mrow><fb:mn>4</fb:mn><fb:mi>b</fb:mi></fb:mrow></fb:math> channel enables discovery up to <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" display="inline"><hb:msub><hb:mi>m</hb:mi><hb:mi>T</hb:mi></hb:msub><hb:mo>∼</hb:mo><hb:mn>1200</hb:mn><hb:mtext> </hb:mtext><hb:mtext> </hb:mtext><hb:mi>GeV</hb:mi></hb:math> at <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML" display="inline"><jb:mi mathvariant="script">L</jb:mi><jb:mo>=</jb:mo><jb:mn>300</jb:mn><jb:mtext> </jb:mtext><jb:mtext> </jb:mtext><jb:msup><jb:mi>fb</jb:mi><jb:mrow><jb:mo>−</jb:mo><jb:mn>1</jb:mn></jb:mrow></jb:msup></jb:math>, while the <mb:math xmlns:mb="http://www.w3.org/1998/Math/MathML" display="inline"><mb:mrow><mb:mn>5</mb:mn><mb:mi>b</mb:mi></mb:mrow></mb:math> analysis extends the reach to <ob:math xmlns:ob="http://www.w3.org/1998/Math/MathML" display="inline"><ob:msub><ob:mi>m</ob:mi><ob:mi>T</ob:mi></ob:msub><ob:mo>∼</ob:mo><ob:mn>1300</ob:mn><ob:mtext> </ob:mtext><ob:mtext> </ob:mtext><ob:mi>GeV</ob:mi></ob:math>. At higher luminosities of <qb:math xmlns:qb="http://www.w3.org/1998/Math/MathML" display="inline"><qb:mrow><qb:mn>1000</qb:mn><qb:mi>–</qb:mi><qb:mn>3000</qb:mn><qb:mtext> </qb:mtext><qb:mtext> </qb:mtext><qb:msup><qb:mi>fb</qb:mi><qb:mrow><qb:mo>−</qb:mo><qb:mn>1</qb:mn></qb:mrow></qb:msup></qb:mrow></qb:math>, the <sb:math xmlns:sb="http://www.w3.org/1998/Math/MathML" display="inline"><sb:mrow><sb:mn>5</sb:mn><sb:mi>b</sb:mi></sb:mrow></sb:math> strategy achieves discovery sensitivity up to <ub:math xmlns:ub="http://www.w3.org/1998/Math/MathML" display="inline"><ub:msub><ub:mi>m</ub:mi><ub:mi>T</ub:mi></ub:msub><ub:mo>∼</ub:mo><ub:mn>1400</ub:mn><ub:mtext> </ub:mtext><ub:mtext> </ub:mtext><ub:mi>GeV</ub:mi></ub:math>. The reach is significantly reduced as <wb:math xmlns:wb="http://www.w3.org/1998/Math/MathML" display="inline"><wb:msub><wb:mi>m</wb:mi><wb:msup><wb:mi>H</wb:mi><wb:mo>±</wb:mo></wb:msup></wb:msub></wb:math> increases, due to the suppression of the <yb:math xmlns:yb="http://www.w3.org/1998/Math/MathML" display="inline"><yb:mi>BR</yb:mi><yb:mo stretchy="false">(</yb:mo><yb:mi>T</yb:mi><yb:mo stretchy="false">→</yb:mo><yb:msup><yb:mi>H</yb:mi><yb:mo>+</yb:mo></yb:msup><yb:mi>b</yb:mi><yb:mo stretchy="false">)</yb:mo></yb:math>: for <dc:math xmlns:dc="http://www.w3.org/1998/Math/MathML" display="inline"><dc:msub><dc:mi>m</dc:mi><dc:msup><dc:mi>H</dc:mi><dc:mo>±</dc:mo></dc:msup></dc:msub><dc:mo>∼</dc:mo><dc:mn>1000</dc:mn><dc:mtext> </dc:mtext><dc:mtext> </dc:mtext><dc:mi>GeV</dc:mi></dc:math>, discovery becomes unattainable across all luminosity and systematic uncertainty configurations. Sensitivity is also strongly impacted by systematic uncertainties: for <fc:math xmlns:fc="http://www.w3.org/1998/Math/MathML" display="inline"><fc:mi>δ</fc:mi><fc:mo>=</fc:mo><fc:mn>10</fc:mn><fc:mo>%</fc:mo></fc:math> and <hc:math xmlns:hc="http://www.w3.org/1998/Math/MathML" display="inline"><hc:msub><hc:mi>m</hc:mi><hc:msup><hc:mi>H</hc:mi><hc:mo>±</hc:mo></hc:msup></hc:msub><hc:mo>&lt;</hc:mo><hc:mspace linebreak="goodbreak"/><hc:mn>1000</hc:mn><hc:mtext> </hc:mtext><hc:mtext> </hc:mtext><hc:mi>GeV</hc:mi></hc:math>, discovery remains viable up to <kc:math xmlns:kc="http://www.w3.org/1998/Math/MathML" display="inline"><kc:msub><kc:mi>m</kc:mi><kc:mi>T</kc:mi></kc:msub><kc:mo>∼</kc:mo><kc:mn>1200</kc:mn><kc:mtext> </kc:mtext><kc:mtext> </kc:mtext><kc:mi>GeV</kc:mi></kc:math> in the <mc:math xmlns:mc="http://www.w3.org/1998/Math/MathML" display="inline"><mc:mrow><mc:mn>5</mc:mn><mc:mi>b</mc:mi></mc:mrow></mc:math> analysis, while for <oc:math xmlns:oc="http://www.w3.org/1998/Math/MathML" display="inline"><oc:mi>δ</oc:mi><oc:mo>=</oc:mo><oc:mn>20</oc:mn><oc:mo>%</oc:mo></oc:math>, no discovery is achievable for <qc:math xmlns:qc="http://www.w3.org/1998/Math/MathML" display="inline"><qc:msub><qc:mi>m</qc:mi><qc:mi>T</qc:mi></qc:msub><qc:mo>≥</qc:mo><qc:mn>1000</qc:mn><qc:mtext> </qc:mtext><qc:mtext> </qc:mtext><qc:mi>GeV</qc:mi></qc:math>.