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:

Active galactic nucleus (AGN) growth in disc-dominated, merger-free galaxies is poorly understood, largely due to the difficulty in disentangling the AGN emission from that of the host galaxy. By carefully separating this emission, we examine the differences between AGNs in galaxies hosting a (possibly) merger-grown, classical bulge, and AGNs in secularly grown, truly bulgeless disc galaxies. We use galfit to obtain robust, accurate morphologies of 100 disc-dominated galaxies imaged with the Hubble Space Telescope. Adopting an inclusive definition of classical bulges, we detect a classical bulge component in per cent of the galaxies. These bulges were not visible in Sloan Digital Sky Survey photometry, however these galaxies are still unambiguously disc-dominated, with an average bulge-to-total luminosity ratio of . We find some correlation between bulge mass and black hole mass for disc-dominated galaxies, though this correlation is significantly weaker in comparison to the relation for bulge-dominated or elliptical galaxies. Furthermore, a significant fraction ( per cent) of our black holes are overly massive when compared to the relationship for elliptical galaxies. We find a weak correlation between total stellar mass and black hole mass for the disc-dominated galaxies, hinting that the stochasticity of black hole–galaxy co-evolution may be higher in disc-dominated than bulge-dominated systems.

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>