A search for the nonresonant production of Higgs boson pairs in the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>H</a:mi><a:mi>H</a:mi><a:mo stretchy="false">→</a:mo><a:mi>b</a:mi><a:mover accent="true"><a:mi>b</a:mi><a:mo stretchy="false">¯</a:mo></a:mover><a:msup><a:mi>τ</a:mi><a:mo>+</a:mo></a:msup><a:msup><a:mi>τ</a:mi><a:mo>−</a:mo></a:msup></a:math> channel is performed using <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mn>140</f:mn><f:mtext> </f:mtext><f:mtext> </f:mtext><f:msup><f:mi>fb</f:mi><f:mrow><f:mo>−</f:mo><f:mn>1</f:mn></f:mrow></f:msup></f:math> of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The analysis strategy is optimized to probe anomalous values of the Higgs boson self-coupling modifier <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:msub><h:mi>κ</h:mi><h:mi>λ</h:mi></h:msub></h:math> and of the quartic <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mi>H</j:mi><j:mi>H</j:mi><j:mi>V</j:mi><j:mi>V</j:mi></j:math> (<l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mrow><l:mrow><l:mi>V</l:mi><l:mo>=</l:mo><l:mi>W</l:mi></l:mrow><l:mo>,</l:mo><l:mrow><l:mi>Z</l:mi></l:mrow></l:mrow></l:math>) coupling modifier <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:msub><n:mi>κ</n:mi><n:mrow><n:mn>2</n:mn><n:mi>V</n:mi></n:mrow></n:msub></n:math>. No significant excess above the expected background from Standard Model processes is observed. An observed (expected) upper limit <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"><p:msub><p:mi>μ</p:mi><p:mrow><p:mi>H</p:mi><p:mi>H</p:mi></p:mrow></p:msub><p:mo><</p:mo><p:mn>5.9</p:mn><p:mo stretchy="false">(</p:mo><p:mn>3.3</p:mn><p:mo stretchy="false">)</p:mo></p:math> is set at 95% confidence-level on the Higgs boson pair production cross section normalized to its Standard Model prediction. The coupling modifiers are constrained to an observed (expected) 95% confidence interval of <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:mo>−</t:mo><t:mn>3.1</t:mn><t:mo><</t:mo><t:msub><t:mi>κ</t:mi><t:mi>λ</t:mi></t:msub><t:mo><</t:mo><t:mn>9.0</t:mn></t:math> (<v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mo>−</v:mo><v:mn>2.5</v:mn><v:mo><</v:mo><v:msub><v:mi>κ</v:mi><v:mi>λ</v:mi></v:msub><v:mo><</v:mo><v:mn>9.3</v:mn></v:math>) and <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:mo>−</x:mo><x:mn>0.5</x:mn><x:mo><</x:mo><x:msub><x:mi>κ</x:mi><x:mrow><x:mn>2</x:mn><x:mi>V</x:mi></x:mrow></x:msub><x:mo><</x:mo><x:mn>2.7</x:mn></x:math> (<z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:mo>−</z:mo><z:mn>0.2</z:mn><z:mo><</z:mo><z:msub><z:mi>κ</z:mi><z:mrow><z:mn>2</z:mn><z:mi>V</z:mi></z:mrow></z:msub><z:mo><</z:mo><z:mn>2.4</z:mn></z:math>), assuming all other Higgs boson couplings are fixed to the Standard Model prediction. The results are also interpreted in the context of effective field theories via constraints on anomalous Higgs boson couplings and Higgs boson pair production cross sections assuming different kinematic benchmark scenarios. © 2024 CERN, for the ATLAS Collaboration 2024 CERN
Particle physics theoretical and experimental studies
