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Abstract:

We study the cross-correlation between maps of the unresolved 𝛾-ray background constructed from the 12-year data release of the Fermi Large-Area Telescope, and the overdensity of galaxies in the redshift range 𝑧≲0.4 as measured by the 2MASS photometric redshift survey and the WISE-SuperCOSMOS photometric survey. A signal is detected at the 8−10⁢𝜎 level, which we interpret in terms of both astrophysical 𝛾-ray sources, and weakly interacting massive particles (WIMP) dark matter decay and annihilation. The sensitivity achieved allows us to characterise the energy and redshift dependence of the signal, and we show that the latter is incompatible with a pure dark matter origin. We thus use our measurement to place an upper bound on the WIMP decay rate and the annihilation cross section, finding constraints that are competitive with those found in other analyses. Our analysis is based on the extraction of clean model-independent observables that can then be used to constrain arbitrary astrophysical and particle physics models. In this sense we produce measurements of the 𝛾-ray emissivity as a function of redshift and rest-frame energy 𝜖, and of a quantity 𝐹⁡(𝜖) encapsulating all WIMP parameters relevant for dark matter decay or annihilation. We make these measurements, together with a full account of their statistical uncertainties, publicly available.

Abstract:

<jats:p>We study the cross-correlation between maps of the unresolved <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>γ</a:mi></a:math>-ray background constructed from the 12-year data release of the Large-Area Telescope, and the overdensity of galaxies in the redshift range <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>z</c:mi><c:mo>≲</c:mo><c:mn>0.4</c:mn></c:math> as measured by the 2MASS photometric redshift survey and the WISE-SuperCOSMOS photometric survey. A signal is detected at the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>8</e:mn><e:mo>−</e:mo><e:mn>10</e:mn><e:mi>σ</e:mi></e:math> level, which we interpret in terms of both astrophysical <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>γ</g:mi></g:math>-ray sources, and weakly interacting massive particles (WIMP) dark matter decay and annihilation. The sensitivity achieved allows us to characterise the energy and redshift dependence of the signal, and we show that the latter is incompatible with a pure dark matter origin. We thus use our measurement to place an upper bound on the WIMP decay rate and the annihilation cross section, finding constraints that are competitive with those found in other analyses. Our analysis is based on the extraction of clean model-independent observables that can then be used to constrain arbitrary astrophysical and particle physics models. In this sense we produce measurements of the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>γ</i:mi></i:math>-ray emissivity as a function of redshift and rest-frame energy <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>ϵ</k:mi></k:math>, and of a quantity <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>F</m:mi><m:mo stretchy="false">(</m:mo><m:mi>ϵ</m:mi><m:mo stretchy="false">)</m:mo></m:math> encapsulating all WIMP parameters relevant for dark matter decay or annihilation. We make these measurements, together with a full account of their statistical uncertainties, publicly available.</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>2024</jats:copyright-year> </jats:permissions> </jats:supplementary-material> </jats:sec>

Abstract:

Inflation is a highly favored theory for the early Universe. It is compatible with current observations of the cosmic microwave background and large scale structure and is a driver in the quest to detect primordial gravitational waves. It is also, given the current quality of the data, highly underdetermined with a large number of candidate implementations. We use a new method in symbolic regression to generate all possible simple scalar field potentials for one of two possible basis sets of operators. Treating these as single-field, slow-roll inflationary models we then score them with an information-theoretic metric ("minimum description length") that quantifies their efficiency in compressing the information in current data. We explore two possible priors on the parameter space of potentials, one related to the functions' structural complexity and one that uses a Katz back-off language model to prefer functions that may be theoretically motivated. This enables us to identify the inflaton potentials that optimally balance simplicity with accuracy at explaining current data, which may subsequently find theoretical motivation. Our exploratory study opens the door to extraction of fundamental physics directly from data, and may be augmented with more refined theoretical priors in the quest for a complete understanding of the early Universe.