Abstracts of Interest
Selected by:
Hayden James
Abstract: 2412.12972
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Title:Search for dark matter from the center of the Earth with ten years of IceCube data
View PDF HTML (experimental)Abstract:The nature of dark matter remains unresolved in fundamental physics. Weakly Interacting Massive Particles (WIMPs), which could explain the nature of dark matter, can be captured by celestial bodies like the Sun or Earth, leading to enhanced self-annihilation into Standard Model particles including neutrinos detectable by neutrino telescopes such as the IceCube Neutrino Observatory. This article presents a search for muon neutrinos from the center of the Earth performed with 10 years of IceCube data using a track-like event selection. We considered a number of WIMP annihilation channels ($\chi\chi\rightarrow\tau^+\tau^-$/$W^+W^-$/$b\bar{b}$) and masses ranging from 10 GeV to 10 TeV. No significant excess over background due to a dark matter signal was found while the most significant result corresponds to the annihilation channel $\chi\chi\rightarrow b\bar{b}$ for the mass $m_{\chi}=250$~GeV with a post-trial significance of $1.06\sigma$. Our results are competitive with previous such searches and direct detection experiments. Our upper limits on the spin-independent WIMP scattering are world-leading among neutrino telescopes for WIMP masses $m_{\chi}>100$~GeV.
Abstract: 2412.11537
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Title:The effect of a biosphere on the habitable timespan of stagnant-lid planets and implications for the atmospheric spectrum
View PDF HTML (experimental)Abstract:Temperature-dependent biological productivity controls silicate weathering and thereby extends the potential habitable timespan of Earth. Models and theoretical considerations indicate that the runaway greenhouse on Earth-like exoplanets is generally accompanied by a dramatic increase in atmospheric H$_2$O and CO$_2$, which might be observed with the upcoming generation of space telescopes. If an active biosphere extends the habitable timespan of exoplanets similarly to Earth, observing the atmospheric spectra of exoplanets near the inner edge of the habitable zone could then give insights into whether the planet is inhabited. Here, we explore this idea for Earth-like stagnant-lid planets. We find that while for a reduced mantle, a surface biosphere extends the habitable timespan of the planet by about 1 Gyr, for more oxidising conditions, the biologically enhanced rate of weathering becomes increasingly compensated for by an increased supply rate of CO$_2$ to the atmosphere. Observationally, the resulting difference in atmospheric CO$_2$ near the inner edge of the habitable zone is clearly distinguishable between biotic planets with active weathering and abiotic planets that have experienced a runaway greenhouse. For an efficient hydrological cycle, the increased bioproductivity also leads to a CH$_4$ biosignature observable with JWST. As the planet becomes uninhabitable, the H$_2$O infrared absorption bands dominate, but the 4.3-micron CO$_2$ band remains a clear window into the CO$_2$ abundances. In summary, while the effect of life on the carbonate-silicate cycle leaves a record in the atmospheric spectrum of Earth-like stagnant-lid planets, future work is needed especially to determine the tectonic state and composition of exoplanets and to push forward the development of the next generation of space telescopes.
Abstract: 2412.14550
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Title:A new air shower array in the Southern Hemisphere looking for the origins of Cosmic rays: the ALPACA experiment
View PDF HTML (experimental)Abstract:The Tibet AS$\gamma$ experiment successfully detected sub-PeV $\gamma$-rays from the Crab nebula using a Surface Array and underground muon detector. Considering this, we are building in Bolivia a new experiment to explore the Southern Hemisphere, looking for the origins of cosmic rays in our Galaxy. The name of this project is Andes Large area PArticle detector for Cosmic ray physics and Astronomy (ALPACA). A prototype array called ALPAQUITA, with $1/4$ the total area of the full ALPACA, started observations in September $2022$. In this paper we introduce the status of ALPAQUITA and the plans to extend the array. We also report the results of the observation of the moon shadow in cosmic rays.
Abstract: 2412.14236
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Title:Mapping Dark Matter Through the Dust of the Milky Way Part I: Dust Correction and Phase Space Density
View PDF HTML (experimental)Abstract:The Boltzmann equation relates the equilibrium phase space distribution of stars in the Milky Way to the Galaxy's gravitational potential. However, observations of stellar populations are biased by extinction from foreground dust, which complicates measurements of the potential in the disk and towards the Galactic center. Using the kinematics of Red Clump and Red Branch stars in Gaia DR3, we use machine learning to simultaneously estimate both the unbiased stellar phase space density and the gravitational potential. The unbiased phase space density is obtained through a learned "dust efficiency factor" -- an observational selection function that accounts for dust extinction. The potential and the dust efficiency are parameterized by fully connected neural networks and are completely data driven. We validate the dust efficiency using a recent three-dimensional dust map in this work, and examine the potential in a companion paper.
Abstract: 2412.14264
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Title:Indirect Detection of Hot Dark Matter
View PDF HTML (experimental)Abstract:Cosmologically stable, light particles that came into thermal contact with the Standard Model in the early universe may persist today as a form of hot dark matter. For relics with masses in the eV range, their role in structure formation depends critically on their mass. We trace the evolution of such hot relics and derive their density profiles around cold dark matter halos, introducing a framework for their indirect detection. Applying this framework to axions -- a natural candidate for a particle that can reach thermal equilibrium with the Standard Model in the early universe and capable of decaying into two photons -- we establish stringent limits on the axion-photon coupling $g_{a \gamma} $ using current observations of dwarf galaxies, the Milky Way halo, and galaxy clusters. Our results set new bounds on hot axions in the $\mathcal{O}(1-10)\,$eV range.
Abstract: 2412.12923
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Title:Generation of cosmic ray trajectories by a Diffusion Model trained on test particles in 3D magnetohydrodynamic turbulence
View PDF HTML (experimental)Abstract:Models for the transport of high energy charged particles through strong magnetic turbulence play a key role in space and astrophysical studies, such as describing the propagation of solar energetic particles and high energy cosmic rays. Inspired by the recent advances in high-performance machine learning techniques, we investigate the application of generative diffusion models to synthesizing test particle trajectories obtained from a turbulent magnetohydrodynamics simulation. We consider velocity increment, spatial transport and curvature statistics, and find excellent agreement with the baseline trajectories for fixed particle energies. Additionally, we consider two synthetic turbulence models for comparison. Finally, challenges towards an application-ready transport model based on our approach are discussed.
Abstract: 2412.12268
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Title:Pauli blocking: probing beyond-mean-field effects in neutrino flavor evolution
View PDF HTML (experimental)Abstract:Neutrino quantum kinetics in dense astrophysical environments is investigated relying on the mean-field approximation. However, it remains to be understood whether mean-field corrections could hinder flavor instabilities that are otherwise foreseen. In this paper, we heuristically explore whether beyond-mean-field effects due to neutrino degeneracy can affect the flavor conversion physics. We find that these corrections shift the stability regions for a suite of (anti)neutrino distributions; a configuration of angular distributions that is stable in the mean-field case can become unstable, or the flavor conversion of previously unstable ensembles can be damped. Our work should serve as a motivation for further understanding the limitations of the mean-field treatment.
Abstract: 2412.13062
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Title:The PeV Frontier: Status of Gamma-ray astronomy after two decades with H.E.S.S., MAGIC, VERITAS and the new window recently opened by HAWC and LHAASO
View PDF HTML (experimental)Abstract:One of the main purposes in $\gamma$-ray astronomy is linked to the origin of Galactic cosmic rays. Unlike cosmic rays, $\gamma$ rays can be used to probe their production sites in the Galaxy and to find which type of astrophysical sources is able to accelerated particles up to PeV energies. Twenty years of observations with current Imaging Atmospheric Cherenkov Telescopes (H.E.S.S., MAGIC and VERITAS) provided an unprecedented view of the very-high-energy $\gamma$-ray sky and a large variety of Galactic sources which are prominent TeV emitters, such as supernova remnants, pulsar wind nebulae, massive stellar clusters and binary systems, in addition to a large fraction of unidentified TeV sources. For a long time, supernova remnants were the most promising candidates for the main source of Galactic cosmic rays, but the new window of ultra-high-energy $\gamma$ rays recently opened by HAWC and LHAASO gave unexpected results and demonstrated the need to re-evaluate some scenarios and to revise some of our definitions. The highest-energy $\gamma$-ray sources are not associated with standard candidates for the main source of Galactic cosmic rays and challenged our usual paradigms, highlighting the vastness of what needs to be explored and understood in the next decades.
Abstract: 2412.15417
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Title:Tethered Balloons for Radio Detection of Neutrinos?
View PDF HTML (experimental)Abstract:The long-duration balloon platform for radio detection of energetic neutrinos, pioneered by ANITA, affords large instantaneous effective areas but has limited livetime. Conversely, tethered balloons, traditionally used for radio detection of non-science objectives (such as electronic surveillance), allow for much longer livetimes, albeit at significantly lower altitudes. In this contribution, a tethered balloon platform for neutrino detection is considered, including estimates of the neutrino sensitivity and a discussion the feasibility of such a platform. Both the Askaryan and tau-neutrino induced Extensive Air Shower channels are explored as target science data for the platform. Tethered balloons locations on ice sheets, land, and in steep valleys or fjords will be considered. Ground-based array calibration and cosmic-ray air shower use cases will also be briefly commented on.
Abstract: 2412.11565
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Title:Monitoring blazar variability to understand extragalactic jets
View PDF HTML (experimental)Abstract:We review the main topics in the field of blazar multiwavelength variability as a tool to understand the physics and structure of extragalactic jets and their central engine. We address issues such as the cross-correlation between flux variations at different frequencies, the mechanisms to explain the long-term and short-term variability, the size of the jet emitting regions, the polarization behaviour, and the periodicities detected in the multiwavelength light curves.
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