Rubin-LSST

Abstract:

<jats:p>A search for the production of three Higgs bosons (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>H</a:mi><a:mi>H</a:mi><a:mi>H</a:mi></a:math>) in the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>b</c:mi><c:mover accent="true"><c:mi>b</c:mi><c:mo stretchy="false">¯</c:mo></c:mover><c:mi>b</c:mi><c:mover accent="true"><c:mi>b</c:mi><c:mo stretchy="false">¯</c:mo></c:mover><c:mi>b</c:mi><c:mover accent="true"><c:mi>b</c:mi><c:mo stretchy="false">¯</c:mo></c:mover></c:math> final state is presented. The search uses <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mn>126</k:mn><k:mtext> </k:mtext><k:mtext> </k:mtext><k:msup><k:mi>fb</k:mi><k:mrow><k:mo>−</k:mo><k:mn>1</k:mn></k:mrow></k:msup></k:math> of proton-proton collision data at <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msqrt><m:mi>s</m:mi></m:msqrt><m:mo>=</m:mo><m:mn>13</m:mn><m:mtext> </m:mtext><m:mtext> </m:mtext><m:mi>TeV</m:mi></m:math> collected with the ATLAS detector at the Large Hadron Collider. The analysis targets both nonresonant and resonant production of <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>H</o:mi><o:mi>H</o:mi><o:mi>H</o:mi></o:math>. The resonant interpretations primarily consider a cascade decay topology of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mi>X</q:mi><q:mo stretchy="false">→</q:mo><q:mi>S</q:mi><q:mi>H</q:mi><q:mo stretchy="false">→</q:mo><q:mi>H</q:mi><q:mi>H</q:mi><q:mi>H</q:mi></q:math> with masses of the new scalars <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"><u:mi>X</u:mi></u:math> and <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mi>S</w:mi></w:math> up to 1.5 and 1 TeV, respectively. In addition to scenarios where <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"><y:mi>S</y:mi></y:math> is off-shell, the nonresonant interpretation includes a search for Standard Model <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mi>H</ab:mi><ab:mi>H</ab:mi><ab:mi>H</ab:mi></ab:math> production, with limits on the trilinear and quartic Higgs self-coupling set. No evidence for <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline"><cb:mi>H</cb:mi><cb:mi>H</cb:mi><cb:mi>H</cb:mi></cb:math> production is observed. An upper limit of 59 fb is set, at the 95% confidence level, on the cross section for Standard Model <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline"><eb:mi>H</eb:mi><eb:mi>H</eb:mi><eb:mi>H</eb:mi></eb:math> production.</jats:p> <jats:sec> <jats:title/> <jats:supplementary-material> <jats:permissions> <jats:copyright-statement>© 2025 CERN, for the ATLAS Collaboration</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> <jats:copyright-holder>CERN</jats:copyright-holder> </jats:permissions> </jats:supplementary-material> </jats:sec>

Abstract:

<jats:p>We present new exclusion bounds obtained at the European X-Ray Free Electron Laser facility (EuXFEL) on axionlike particles in the mass range <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msup><a:mrow><a:mn>10</a:mn></a:mrow><a:mrow><a:mo>−</a:mo><a:mn>3</a:mn></a:mrow></a:msup><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mrow><a:mi>eV</a:mi></a:mrow><a:mo>≲</a:mo><a:msub><a:mrow><a:mi>m</a:mi></a:mrow><a:mrow><a:mi>a</a:mi></a:mrow></a:msub><a:mo>≲</a:mo><a:msup><a:mrow><a:mn>10</a:mn></a:mrow><a:mrow><a:mn>4</a:mn></a:mrow></a:msup><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>eV</a:mi></a:mrow></a:math>. Our experiment exploits the Primakoff effect via which photons can, in the presence of a strong external electric field, decay into axions, which then convert back into photons after passing through an opaque wall. While similar searches have been performed previously at a third-generation synchrotron [Yamaji , ], our work demonstrates improved sensitivity, exploiting the higher brightness of x-rays at EuXFEL.</jats:p> <jats:sec> <jats:title/> <jats:supplementary-material> <jats:permissions> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material> </jats:sec>