LHC signatures of a generalized Georgi-Machacek model

Vector-boson fusion productions of new Higgs bosons decaying into pairs of electroweak gauge bosons (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mi>W</a:mi><a:mo>±</a:mo></a:msup><a:msup><a:mi>W</a:mi><a:mo>±</a:mo></a:msup></a:math>, <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>W</c:mi><c:mi>Z</c:mi></c:math>, and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>Z</e:mi><e:mi>Z</e:mi></e:math>) are smoking-gun signature of new Higgs bosons in general, and of the Georgi-Machacek (GM) model in particular. Notably, ATLAS has observed a <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>3.3</g:mn><g:mi>σ</g:mi></g:math> excess in <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msup><i:mi>W</i:mi><i:mo>±</i:mo></i:msup><i:msup><i:mi>W</i:mi><i:mo>±</i:mo></i:msup></i:math> at <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mo>≈</k:mo><k:mn>450</k:mn><k:mtext> </k:mtext><k:mtext> </k:mtext><k:mi>GeV</k:mi></k:math> and a <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mn>2.8</m:mn><m:mi>σ</m:mi></m:math> excess in the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>W</o:mi><o:mi>Z</o:mi></o:math> channel at <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mo>≈</q:mo><q:mn>375</q:mn><q:mtext> </q:mtext><q:mtext> </q:mtext><q:mi>GeV</q:mi></q:math>, while compact muon solenoid reported weaker-than-expected limits at these masses. In this article, we consider a generalized version of the GM model without the custodial <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mi>S</s:mi><s:mi>U</s:mi><s:mo stretchy="false">(</s:mo><s:mn>2</s:mn><s:msub><s:mo stretchy="false">)</s:mo><s:mi>C</s:mi></s:msub></s:math> symmetry in the scalar potential as a minimal model to explain these excesses. In the limit of small mixing among the Higgs bosons, the <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:msup><w:mi>W</w:mi><w:mo>±</w:mo></w:msup><w:msup><w:mi>W</w:mi><w:mo>±</w:mo></w:msup></w:math> and <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"><y:mi>W</y:mi><y:mi>Z</y:mi></y:math> signals can be explained by the doubly and singly charged Higgs bosons originating primarily from the <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mi>Y</ab:mi><ab:mo>=</ab:mo><ab:mn>1</ab:mn></ab:math> triplet, while respecting the bounds from <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline"><cb:mi>Z</cb:mi><cb:mi>Z</cb:mi></cb:math> searches. Furthermore, the neutral Higgs boson mostly contained in the <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline"><eb:mi>Y</eb:mi><eb:mo>=</eb:mo><eb:mn>0</eb:mn></eb:math> triplet can account for the (<gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML" display="inline"><gb:mo>≈</gb:mo><gb:mn>4</gb:mn><gb:mi>σ</gb:mi></gb:math>) excess at <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline"><ib:mo>≈</ib:mo><ib:mn>152</ib:mn><ib:mtext> </ib:mtext><ib:mtext> </ib:mtext><ib:mi>GeV</ib:mi></ib:math> in associated diphoton production. Furthermore, the model is consistent with the constraints from vacuum stability and the Standard Model Higgs signal strength measurements, such that it can provide a valid combined explanation for some of the most significant LHC excesses.