Search

We point out that dark matter can illuminate planetary skies via ultraviolet airglow. Dark matter annihilation products can excite molecular hydrogen, which then deexcites to produce ultraviolet emission in the Lyman and Werner bands. We search for this new effect by analyzing nightside ultraviolet radiation data from Voyager 1, Voyager 2, and New Horizons flybys of Neptune, Uranus, Saturn, and Jupiter. Our findings set new constraints on the dark matter-nucleon scattering cross section down to about $10^{-40}~$cm$^2$. We highlight that future ultraviolet airglow measurements of Solar System planets or other worlds provide a new dark matter discovery avenue., Comment: 5+6 pages, 3+2 figures

We show that stars in the inner parsec of the Milky Way can be significantly affected by dark matter annihilation, producing population-level effects that are visible in a Hertzsprung-Russell (HR) diagram. We establish the dark HR diagram, where stars lie on a new stable $\textit{dark main sequence}$ with similar luminosities, but lower temperatures, than the standard main sequence. The dark matter density in these stars continuously replenishes, granting these stars immortality and solving multiple stellar anomalies. Upcoming telescopes could detect the dark main sequence, offering a new dark matter discovery avenue., Comment: 6 pages, 3 figures. Appendix adds 2 pages, 1 figure

Dark Matter (DM) can become captured, deposit annihilation energy, and hence increase the heat flow in exoplanets and brown dwarfs. Detecting such a DM-induced heating in a population of exoplanets in the inner kpc of the Milky Way thus provides potential sensitivity to the galactic DM halo parameters. We develop a Bayesian Hierarchical Model to investigate the feasibility of DM discovery with exoplanets and examine future prospects to recover the spatial distribution of DM in the Milky Way. We reconstruct from mock exoplanet datasets observable parameters such as exoplanet age, temperature, mass, and location, together with DM halo parameters, for representative choices of measurement uncertainty and the number of exoplanets detected. We find that detection of $\mathcal{O}(100)$ exoplanets in the inner Galaxy can yield quantitative information on the galactic DM density profile, under the assumption of 10% measurement uncertainty. Even as few as $\mathcal{O}(10)$ exoplanets can deliver meaningful sensitivities if the DM density and inner slope are sufficiently large., Comment: Comments are welcome. 14 pages, 11 figures, 2 tables

A wide variety of celestial bodies have been considered as dark matter detectors. Which stands the best chance of delivering the discovery of dark matter? Which is the most powerful dark matter detector? We investigate a range of objects, including the Sun, Earth, Jupiter, Brown Dwarfs, White Dwarfs, Neutron Stars, Stellar populations, and Exoplanets. We quantify how different objects are optimal dark matter detectors in different regimes by deconstructing some of the in-built assumptions in these search sensitivities, including observation potential and particle model assumptions. We show how different objects can be expected to deliver corroborating signals. We discuss different search strategies, their opportunities and limitations, and the interplay of regimes where different celestial objects are optimal dark matter detectors., Comment: 53 pages, 13 figures

Dark kinetic heating of neutron stars has been previously studied as a promising dark matter detection avenue. Kinetic heating occurs when dark matter is sped up to relativistic speeds in the gravitational well of high-escape velocity objects, and deposits kinetic energy after becoming captured by the object, thereby increasing its temperature. We show that dark kinetic heating can be significant even in objects with low-escape velocities, such as exoplanets and brown dwarfs, increasing the discovery potential of such searches. This can occur if there is a long-range dark force, creating a "dark escape velocity", leading to heating rates substantially larger than those expected from neutron stars. We consequently set constraints on dark sector parameters using Wide-field Infrared Survey Explorer and JWST data on Super-Jupiter WISE 0855-0714, and map out future sensitivity to the dark matter scattering cross section below $10^{-40}~{\rm cm}^2$. We compare dark kinetic heating rates of other lower escape velocity objects such as the Earth, Sun, and white dwarfs, finding complementary kinetic heating signals are possible depending on particle physics parameters., Comment: 24 pages, 11 figures

We recently pointed out that power measurements of single quasiparticle devices can be used to detect dark matter. These devices have the lowest known energy thresholds, far surpassing standard direct detection experiments, requiring energy deposition above only about an meV. We calculate dark matter induced quasiparticle densities in transmon qubits, and use the latest transmon qubit measurements that provide one of the strongest existing lab-based bounds on dark matter-nucleon scattering below about 100 MeV. We strongly constrain sub-component dark matter, using both a dark matter population thermalized in the Earth as well as the dark matter wind from the Galactic halo. We demonstrate future potential sensitivities using devices with low quasiparticle densities., Comment: (v2) 11 pages, 5 figures, matches published version

We present a new search for dark matter using planetary atmospheres. We point out that annihilating dark matter in planets can produce ionizing radiation, which can lead to excess production of ionospheric $H_3^+$. We apply this search strategy to the night side of Jupiter near the equator. The night side has zero solar irradiation, and low latitudes are sufficiently far from ionizing auroras, leading to an effectively background-free search. We use Cassini data on ionospheric $H_3^+$ emission collected 3 hours either side of Jovian midnight, during its flyby in 2000, and set novel constraints on the dark matter-nucleon scattering cross section down to about $10^{-38}$ cm$^2$. We also highlight that dark matter atmospheric ionization may be detected in Jovian exoplanets using future high-precision measurements of planetary spectra., Comment: 7 pages, 2 figures. Comments welcome!

High resolution infrared data has revealed several young stars in close proximity to Sgr A*. These stars may encounter extremely high dark matter densities. We examine scenarios where dark matter scatters on stellar gas, accumulates in stellar cores, and then annihilates. We study the stars S2, S62, S4711 and S4714 and find three observable effects. First, dark matter interactions can inhibit in situ star-formation close to Sgr A*, favoring scenarios where these stars migrate into the Galactic Center. Second, dark matter interactions can delay main sequence evolution, making stars older than they appear. Third, very high dark matter densities can inject enough energy to disrupt main sequence stars, allowing S-star observations to constrain the dark matter density near Sgr A*., Comment: 14 pages, 8 figures. Revised version matches version accepted by PRD

In the past few years, many mesoscale systems have been proposed as possible detectors of sub-GeV dark matter particles. In this work, we point out the feasibility of probing dark matter-nucleon scattering cross section using superconductor-based quantum devices with meV-scale energy threshold. We compute new limits on spin-independent dark matter scattering cross section using the existing power measurement data from three different experiments for MeV to 10 GeV mass. We derive the limits for both halo and thermalized dark matter populations., Comment: Contribution to TAUP 2023, University of Vienna

We show that Milky Way white dwarfs are excellent targets for dark matter (DM) detection. Using Fermi and H.E.S.S. Galactic center gamma-ray data, we investigate sensitivity to DM annihilating within white dwarfs into long-lived or boosted mediators and producing detectable gamma rays. Depending on the Galactic DM distribution, we set new constraints on the spin-independent scattering cross section down to $10^{-45}-10^{-41}$ cm$^2$ in the sub-GeV DM mass range, which is multiple orders of magnitude stronger than existing limits. For a generalized NFW DM profile, we find that our white dwarf constraints exceed spin-independent direct detection limits across most of the sub-GeV to multi-TeV DM mass range, achieving sensitivities as low as about $10^{-46}$ cm$^2$. In addition, we improve earlier versions of the DM capture calculation in white dwarfs, by including the low-temperature distribution of nuclei when the white dwarf approaches crystallization. This yields smaller capture rates than previously calculated by a factor of a few up to two orders of magnitude, depending on white dwarf size and the astrophysical system., Comment: 29 pages, 5 figures, published in JCAP

Signatures of dark matter in celestial objects have become of increasing interest due to their powerful detection prospects. To test any of these signatures, the fundamental quantity needed is the rate in which dark matter is captured by celestial objects. Depending on whether dark matter is light, heavy, or comparable in mass to the celestial-body scattering targets, there are different considerations when calculating the capture rate. Furthermore, if dark matter has strong or weak interactions, the physical behaviour important for capture varies. Using both analytic approximations and simulations, we demonstrate how to treat dark matter capture in a range of celestial objects for arbitrary dark matter mass and interaction strength. We release our calculation framework as a public package available in both Python and Mathematica versions, called Asteria., Comment: 32 pages, 11 figures, for the Asteria package, see https://zenodo.org/record/8150110

The minimum testable dark matter (DM) mass for almost all DM signatures in celestial bodies is determined by the rate at which DM evaporates. DM evaporation has previously been calculated assuming a competition between the gravitational potential of the object, and thermal kicks from the celestial-body matter. We point out a new effect, where mediators with a range larger than the interparticle spacing induce a force proportional to the density gradient of celestial objects, forming an evaporation barrier for the DM. This effect can be so significant that evaporation does not occur even for sub-MeV DM, in stark contrast to previous calculations. This opens up a wide range of new light DM searches, many orders of magnitude in DM mass below the sensitivity of direct detection., Comment: 20 pages, 5 figures, published in JCAP

We point out that power measurements of single quasiparticle devices open a new avenue to detect dark matter (DM). The threshold of these devices is set by the Cooper pair binding energy, and is therefore so low that they can detect DM as light as about an MeV incoming from the Galactic halo, as well as the low-velocity thermalized DM component potentially present in the Earth. Using existing power measurements with these new devices, as well as power measurements with SuperCDMS-CPD, we set new constraints on the spin-independent DM scattering cross section for DM masses from about 10 MeV to 10 GeV. We outline future directions to improve sensitivity to both halo DM and a thermalized DM population in the Earth using power deposition in quantum devices., Comment: v2: version published in PRL

Dark matter (DM) can be captured in celestial bodies after scattering and losing sufficient energy to become gravitationally bound. We derive a general framework that describes the current DM distribution inside celestial objects, which self-consistently includes the effects of concentration diffusion, thermal diffusion, gravity, and capture accumulation. For DM with sufficient interactions, we show that a significant DM population can thermalize and sit towards the celestial-body surface. This floating distribution allows for new phenomenology for DM searches in a wide range of celestial bodies, including the Sun, Earth, Jupiter, Brown Dwarfs, and Exoplanets., Comment: 20 pages, 6 figures, 100000000000000+ dark matter particles per cm^3 at Earth's surface. v2: expanded appendix B, references added

Cosmological and astrophysical observations currently provide the only robust, positive evidence for dark matter. Cosmic probes of dark matter, which seek to determine the fundamental properties of dark matter through observations of the cosmos, have emerged as a promising means to reveal the nature of dark matter. This report summarizes the current status and future potential of cosmic probes to inform our understanding of the fundamental nature of dark matter in the coming decade., Comment: Report of the CF3 Topical Group for Snowmass 2021; 35 pages, 10 figures, many references. V3 updates Fig 3-2 and the author list

This report summarizes the findings of the CF1 Topical Subgroup to Snowmass 2021, which was focused on particle dark matter. One of the most important scientific goals of the next decade is to reveal the nature of dark matter (DM). To accomplish this goal, we must delve deep, to cover high priority targets including weakly-interacting massive particles (WIMPs), and search wide, to explore as much motivated DM parameter space as possible. A diverse, continuous portfolio of experiments at large, medium, and small scales that includes both direct and indirect detection techniques maximizes the probability of discovering particle DM. Detailed calibrations and modeling of signal and background processes are required to make a convincing discovery. In the event that a candidate particle is found through different means, for example at a particle collider, the program described in this report is also essential to show that it is consistent with the actual cosmological DM. The US has a leading role in both direct and indirect detection dark matter experiments -- to maintain this leading role, it is imperative to continue funding major experiments and support a robust R\&D program., Comment: Submitted 30 pages, 11 figures, many references, Report of the CF1 Topical Group for Snowmass 2021

We summarize progress made in theoretical astrophysics and cosmology over the past decade and areas of interest for the coming decade. This Report is prepared as the TF09 "Astrophysics and Cosmology" topical group summary for the Theory Frontier as part of the Snowmass 2021 process., Comment: 57 pages

A sub-fraction of dark matter or new particles trapped inside celestial objects can significantly alter their macroscopic properties. We investigate the new physics imprint on celestial objects by using a generic framework to solve the Tolman-Oppenheimer-Volkoff (TOV) equations for up to two fluids. We test the impact of populations of new particles on celestial objects, including the sensitivity to self-interaction sizes, new particle mass, and net population mass. Applying our setup to neutron stars and boson stars, we find rich phenomenology for a range of these parameters, including the creation of extended atmospheres. These atmospheres are detectable by their impact on the tidal love number, which can be measured at upcoming gravitational wave experiments such as Advanced LIGO, the Einstein Telescope, and LISA. We release our calculation framework as a publicly available code, allowing the TOV equations to be generically solved for arbitrary new physics models in novel and admixed celestial objects., Comment: 10 pages, 6 figures. Code available and archived at https://zenodo.org/record/7361819#.Y5pqrtLMKC0. Version accepted for publication in PRD

Exploring dark matter via observations of extreme astrophysical environments -- defined here as heavy compact objects such as white dwarfs, neutron stars, and black holes, as well as supernovae and compact object merger events -- has been a major field of growth since the last Snowmass process. Theoretical work has highlighted the utility of current and near-future observatories to constrain novel dark matter parameter space across the full mass range. This includes gravitational wave instruments and observatories spanning the electromagnetic spectrum, from radio to gamma-rays. While recent searches already provide leading sensitivity to various dark matter models, this work also highlights the need for theoretical astrophysics research to better constrain the properties of these extreme astrophysical systems. The unique potential of these search signatures to probe dark matter adds motivation to proposed next-generation astronomical and gravitational wave instruments., Comment: Contribution to Snowmass 2021 -- CF3. Dark Matter: Cosmic Probes

This white paper discusses the current landscape and prospects for experiments sensitive to particle dark matter processes producing photons and cosmic rays. Much of the gamma-ray sky remains unexplored on a level of sensitivity that would enable the discovery of a dark matter signal. Currently operating GeV-TeV observatories, such as Fermi-LAT, atmospheric Cherenkov telescopes, and water Cherenkov detector arrays continue to target several promising dark matter-rich environments within and beyond the Galaxy. Soon, several new experiments will continue to explore, with increased sensitivity, especially extended targets in the sky. This paper reviews the several near-term and longer-term plans for gamma-ray observatories, from MeV energies up to hundreds of TeV. Similarly, the X-ray sky has been and continues to be monitored by decade-old observatories. Upcoming telescopes will further bolster searches and allow new discovery space for lines from, e.g., sterile neutrinos and axion-photon conversion. Furthermore, this overview discusses currently operating cosmic-ray probes and the landscape of future experiments that will clarify existing persistent anomalies in cosmic radiation and spearhead possible new discoveries. Finally, the article closes with a discussion of necessary cross section measurements that need to be conducted at colliders to reduce substantial uncertainties in interpreting photon and cosmic-ray measurements in space., Comment: 61 pages, 21 figures, Snowmass2021 Cosmic Frontier White Paper

Intriguing signals with excesses over expected backgrounds have been observed in many astrophysical and terrestrial settings, which could potentially have a dark matter origin. Astrophysical excesses include the Galactic Center GeV gamma-ray excess detected by the Fermi Gamma-Ray Space Telescope, the AMS antiproton and positron excesses, and the 511 and 3.5 keV X-ray lines. Direct detection excesses include the DAMA/LIBRA annual modulation signal, the XENON1T excess, and low-threshold excesses in solid state detectors. We discuss avenues to resolve these excesses, with actions the field can take over the next several years., Comment: 57 pages, solicited white paper submitted to the Proceedings of the US Community Study on the Future of Particle Physics (Snowmass 2021)

This whitepaper focuses on the astrophysical systematics which are encountered in dark matter searches. Oftentimes in indirect and also in direct dark matter searches, astrophysical systematics are a major limiting factor to sensitivity to dark matter. Just as there are many forms of dark matter searches, there are many forms of backgrounds. We attempt to cover the major systematics arising in dark matter searches using photons -- radio and gamma rays -- to cosmic rays, neutrinos and gravitational waves. Examples include astrophysical sources of cosmic messengers and their interactions which can mimic dark matter signatures. In turn, these depend on commensurate studies in understanding the cosmic environment -- gas distributions, magnetic field configurations -- as well as relevant nuclear astrophysics. We also cover the astrophysics governing celestial bodies and galaxies used to probe dark matter, from black holes to dwarf galaxies. Finally, we cover astrophysical backgrounds related to probing the dark matter distribution and kinematics, which impact a wide range of dark matter studies. In the future, the rise of multi-messenger astronomy, and novel analysis methods to exploit it for dark matter, will offer various strategic ways to continue to enhance our understanding of astrophysical backgrounds to deliver improved sensitivity to dark matter., Comment: contribution to Snowmass 2021

We outline the unique opportunities and challenges in the search for "ultraheavy" dark matter candidates with masses between roughly $10~{\rm TeV}$ and the Planck scale $m_{\rm pl} \approx 10^{16}~{\rm TeV}$. This mass range presents a wide and relatively unexplored dark matter parameter space, with a rich space of possible models and cosmic histories. We emphasize that both current detectors and new, targeted search techniques, via both direct and indirect detection, are poised to contribute to searches for ultraheavy particle dark matter in the coming decade. We highlight the need for new developments in this space, including new analyses of current and imminent direct and indirect experiments targeting ultraheavy dark matter and development of new, ultra-sensitive detector technologies like next-generation liquid noble detectors, neutrino experiments, and specialized quantum sensing techniques., Comment: Solicited community whitepaper for the Snowmass2021 process (Cosmic frontier, particle dark matter working group). 10 pages, 3 figures, many references. Comments welcome. v2: minor revisions based on comments

While astrophysical and cosmological probes provide a remarkably precise and consistent picture of the quantity and general properties of dark matter, its fundamental nature remains one of the most significant open questions in physics. Obtaining a more comprehensive understanding of dark matter within the next decade will require overcoming a number of theoretical challenges: the groundwork for these strides is being laid now, yet much remains to be done. Chief among the upcoming challenges is establishing the theoretical foundation needed to harness the full potential of new observables in the astrophysical and cosmological domains, spanning the early Universe to the inner portions of galaxies and the stars therein. Identifying the nature of dark matter will also entail repurposing and implementing a wide range of theoretical techniques from outside the typical toolkit of astrophysics, ranging from effective field theory to the dramatically evolving world of machine learning and artificial-intelligence-based statistical inference. Through this work, the theory frontier will be at the heart of dark matter discoveries in the upcoming decade., Comment: Contribution to Snowmass 2021, 24 pages, 4 figures, comments welcome

We present the first dedicated $\gamma$-ray analysis of Jupiter, using 12 years of data from the Fermi Telescope. We find no robust evidence of $\gamma$-ray emission, and set upper limits of $\sim10^{-9}~$GeV cm$^{-2}\,$s$^{-1}$ on the Jovian $\gamma$-ray flux. We point out that Jupiter is an advantageous dark matter (DM) target due to its large surface area (compared to other solar system planets), and cool core temperature (compared to the Sun). These properties allow Jupiter to both capture and retain lighter DM, providing a complementary probe of sub-GeV DM. We therefore identify and perform a new search for DM-sourced $\gamma$-rays in Jupiter, where DM annihilates to long-lived particles, which can escape the Jovian surface and decay into $\gamma$-rays. We consequently constrain DM-proton scattering cross-sections as low as about $10^{-40}~$cm$^2$, showing Jupiter is up to ten orders of magnitude more sensitive than direct detection. This sensitivity is reached under the assumption that the mediator decay length is sufficient to escape Jupiter, and the equilibrium between DM capture and annihilation; sensitivities can be lower depending on the DM model. Our work motivates follow-up studies with upcoming MeV telescopes such as AMEGO and e-ASTROGAM., Comment: 5+11 pages, 4+2 figures, version accepted for publication in PRL

Indirect detection experiments typically measure the flux of annihilating dark matter (DM) particles propagating freely through galactic halos. We consider a new scenario where celestial bodies "focus" DM annihilation events, increasing the efficiency of halo annihilation. In this setup, DM is first captured by celestial bodies, such as neutron stars or brown dwarfs, and then annihilates within them. If DM annihilates to sufficiently long-lived particles, they can escape and subsequently decay into detectable radiation. This produces a distinctive annihilation morphology, which scales as the product of the DM and celestial body densities, rather than as DM density squared. We show that this signal can dominate over the halo annihilation rate in $\gamma$-ray observations in both the Milky Way Galactic center and globular clusters. We use \textit{Fermi} and H.E.S.S. data to constrain the DM-nucleon scattering cross section, setting powerful new limits down to $\sim10^{-39}~$cm$^2$ for sub-GeV DM using brown dwarfs, which is up to nine orders of magnitude stronger than existing limits. We demonstrate that neutron stars can set limits for TeV-scale DM down to about $10^{-47}~$cm$^2$.

We present exoplanets as new targets to discover Dark Matter (DM). Throughout the Milky Way, DM can scatter, become captured, deposit annihilation energy, and increase the heat flow within exoplanets. We estimate upcoming infrared telescope sensitivity to this scenario, finding actionable discovery or exclusion searches. We find that DM with masses above about an MeV can be probed with exoplanets at DM-proton and DM-electron scattering cross sections down to about $10^{-37}$cm$^2$, stronger than existing limits by up to six orders of magnitude. Supporting evidence of a DM origin can be identified through DM-induced exoplanet heating correlated with Galactic position, and hence DM density. This provides new motivation to measure the temperature of the billions of brown dwarfs, rogue planets, and gas giants peppered throughout our Galaxy., Comment: 5+25 pages, 3+7 figures, 100000000000+ exoplanets. v4: appendix IV updated, sensitivity plots extended, conclusions unchanged

New light particles produced in supernovae can lead to additional energy loss and a consequent deficit in neutrino production in conflict with the neutrinos observed from Supernova 1987A (SN1987A). Contrary to the majority of previous SN1987A studies, we examine the impact of $Z'$ bosons, axions, and axion-like particles (ALPs) interacting with the muons produced in SN1987A. For the first time, we find constraints on generic $Z'$ bosons coupled to muons, and apply our results to particle models including gauged $L_\mu-L_\tau$ number, $U(1)_{L_\mu-L_\tau}$, and gauged $B-L$ number, $U(1)_{B-L}$. We constrain $Z'$ bosons with masses up to about 250-500 MeV, and down to about $10^{-9}$ in $Z'$-muon coupling. We also extend previous work on axion-muon couplings by examining the importance of loop-level interactions, as well as performing calculations over a wider range of axion masses. We constrain muon-coupled axions from arbitrarily low masses up to about 200-500 MeV, with bounds extending down to axion-muon couplings of approximately $10^{-8}$ GeV$^{-1}$. We conclude that supernovae broadly provide a sensitive probe of new lightly-coupled particles interacting with muons., Comment: 29 pages, several hot pink figures. v2: figs 7 and 8 updated, references added

I present a short overview of the latest developments in indirect searches for dark matter using gamma rays, X-rays, charged cosmic rays, micro waves, radio waves, and neutrinos. I briefly outline key past, present, and future experiments and their search strategies. In several searches there are exciting anomalies which could potentially be emerging dark matter signals. I discuss these anomalous signals, and some future prospects to determine their origins., Comment: 25 pages, 10 figures (including 4 new telescope timescale/sensitivity summary plots). Mini-review, based on an invited overview talk presented at EDSU 2020, Pointe-\`a-Pitre, Guadeloupe

The Galactic Center GeV excess (GCE) has garnered great interest as a possible signal of either dark matter annihilation or some novel astrophysical phenomenon, such as a new population of gamma-ray emitting pulsars. In a companion paper, we showed that in a $10^\circ$ radius region of interest (ROI) surrounding the Galactic Center, apparent evidence for GCE point sources (PSs) from non-Poissonian template fitting (NPTF) is actually an artifact of unmodeled north-south asymmetry of the GCE. In this work, we develop a simplified analytic description of how signal mismodeling can drive an apparent preference for a PS population, and demonstrate how the behavior pointed out in the companion paper also appears in simpler simulated datasets that contain no PS signals at all. We explore the generality of this behavior in the real gamma-ray data, and discuss the implications for past and future studies using NPTF techniques. While the drop in PS preference once north-south asymmetry is included is not ubiquitous in larger ROIs, we show that any overly-rigid signal model is expected to yield a spurious PS signal that can appear very convincing: as well as apparent significance comparable to what one would expect from a true PS population, the signal can exhibit stability against a range of variations in the analysis, and a source count function that is very consistent with previous apparent NPTF-based detections of a GCE PS population. This contrasts with previously-studied forms of systematic mismodeling which are unlikely to mimic a PS population in the same way. In the light of this observation, and its explicit realization in the region where the GCE is brightest, we argue that a dominantly smooth origin for the GCE is not in tension with existing NPTF analyses., Comment: 47 pages, 14 figures, published in PRD. See also companion PRL paper arXiv:2002.12370

We re-examine evidence that the Galactic Center Excess (GCE) originates primarily from point sources (PSs). We show that in our region of interest, non-Poissonian template fitting (NPTF) evidence for GCE PSs is an artifact of unmodeled north-south asymmetry of the GCE. This asymmetry is strongly favored by the fit (although it is unclear if this is physical), and when it is allowed, the preference for PSs becomes insignificant. We reproduce this behavior in simulations, including detailed properties of the spurious PS population. We conclude that NTPF evidence for GCE PSs is highly susceptible to certain systematic errors, and should not at present be taken to robustly disfavor a dominantly smooth GCE., Comment: 6+6 pages, 3+3 figures, published in PRL. See also companion PRD paper arXiv:2002.12371

In hidden sector models, dark matter does not directly couple to the particle content of the Standard Model, strongly suppressing rates at direct detection experiments, while still allowing for large signals from annihilation. In this paper, we conduct an extensive study of hidden sector dark matter, covering a wide range of dark matter spins, mediator spins, interaction diagrams, and annihilation final states, in each case determining whether the annihilations are s-wave (thus enabling efficient annihilation in the universe today). We then go on to consider a variety of portal interactions that allow the hidden sector annihilation products to decay into the Standard Model. We broadly classify constraints from relic density requirements and dwarf spheroidal galaxy observations. In the scenario that the hidden sector was in equilibrium with the Standard Model in the early universe, we place a lower bound on the portal coupling, as well as on the dark matter's elastic scattering cross section with nuclei. We apply our hidden sector results to the observed Galactic Center gamma-ray excess and the cosmic-ray antiproton excess. We find that both of these excesses can be simultaneously explained by a variety of hidden sector models, without any tension with constraints from observations of dwarf spheroidal galaxies., Comment: 40 pages, 11 figures, matches the JHEP version, references added

Neutron stars serve as excellent next-generation thermal detectors of dark matter, heated by the scattering and annihilation of dark matter accelerated to relativistic speeds in their deep gravitational wells. However, the dynamics of neutron star cores are uncertain, making it difficult at present to unequivocally compute dark matter scattering in this region. On the other hand, the physics of an outer layer of the neutron star, the crust, is more robustly understood. We show that dark matter scattering solely with the low-density crust still kinetically heats neutron stars to infrared temperatures detectable by forthcoming telescopes. We find that for both spin-independent and spin-dependent scattering on nucleons, the crust-only cross section sensitivity is $10^{-43} - 10^{-41}$~cm$^2$ for dark matter masses of 100 MeV $-$ 1 PeV, with the best sensitivity arising from dark matter scattering with a crust constituent called nuclear pasta (including gnocchi, spaghetti, and lasagna phases). For dark matter masses from 10 eV to 1 MeV, the sensitivity is $10^{-39} - 10^{-34}$~cm$^2$, arising from exciting collective phonon modes in a neutron superfluid in the inner crust. Furthermore, for any $s$-wave or $p$-wave annihilating dark matter, we show that dark matter will efficiently annihilate by thermalizing just with the neutron star crust, regardless of whether the dark matter ever scatters with the neutron star core. This implies efficient annihilation in neutron stars for any electroweakly interacting dark matter with inelastic mass splittings of up to 200 MeV, including Higgsinos. We conclude that neutron star crusts play a key role in dark matter scattering and annihilation in neutron stars., Comment: 42 pages, 7 figures, 1 table, JCAP version

Statistical evidence has previously suggested that the Galactic Center GeV Excess (GCE) originates largely from point sources, and not from annihilating dark matter. We examine the impact of unmodeled source populations on identifying the true origin of the GCE using non-Poissonian template fitting (NPTF) methods. In a proof-of-principle example with simulated data, we discover that unmodeled sources in the Fermi Bubbles can lead to a dark matter signal being misattributed to point sources by the NPTF. We discover striking behavior consistent with a mismodeling effect in the real Fermi data, finding that large artificial injected dark matter signals are completely misattributed to point sources. Consequently, we conclude that dark matter may provide a dominant contribution to the GCE after all., Comment: 7+32 pages, 2+20 figures

Weakly Interacting Massive Particles (WIMPs) have long reigned as one of the leading classes of dark matter candidates. The observed dark matter abundance can be naturally obtained by freezeout of weak-scale dark matter annihilations in the early universe. This "thermal WIMP" scenario makes direct predictions for the total annihilation cross section that can be tested in present-day experiments. While the dark matter mass constraint can be as high as $m_\chi\gtrsim100$ GeV for particular annihilation channels, the constraint on the total cross section has not been determined. We construct the first model-independent limit on the WIMP total annihilation cross section, showing that allowed combinations of the annihilation-channel branching ratios considerably weaken the sensitivity. For thermal WIMPs with s-wave $2\rightarrow2$ annihilation to visible final states, we find the dark matter mass is only known to be $m_\chi\gtrsim20$ GeV. This is the strongest largely model-independent lower limit on the mass of thermal-relic WIMPs, together with the upper limit on the mass from the unitarity bound ($m_\chi\lesssim 100$ TeV), it defines what we call the "WIMP window". To probe the remaining mass range, we outline ways forward., Comment: 16 pages, 10 figures, references added, accepted for publication in PRD

Many dark matter interaction types lead to annihilation processes which suffer from p-wave suppression or helicity suppression, rendering them subdominant to unsuppressed s-wave processes. We demonstrate that the natural inclusion of dark initial state radiation can open an unsuppressed s-wave annihilation channel, and thus provide the dominant dark matter annihilation process for particular interaction types. We illustrate this effect with the bremsstrahlung of a dark spin-0 or dark spin-1 particle from fermionic dark matter, $\overline{\chi}\chi\rightarrow \overline{f}f\phi$ or $\overline{f}fZ'$. The dark initial state radiation process, despite having a 3-body final state, proceeds at the same order in the new physics scale $\Lambda$ as the annihilation to the 2-body final state $\overline{\chi}\chi\rightarrow \overline{f}f$. This is lower order in $\Lambda$ than the well-studied lifting of helicity suppression via Standard Model final state radiation, or virtual internal bremsstrahlung. This dark bremsstrahlung process should influence LHC and indirect detection searches for dark matter., Comment: 10 pages, 5 figures, 2 tables. v2: minor changes, matches version published in PRD

Dark matter capture and annihilation in the Sun can produce detectable high-energy neutrinos, providing a probe of the dark matter-proton scattering cross section. We consider the case when annihilation proceeds via long-lived dark mediators, which allows gamma rays to escape the Sun and reduces the attenuation of neutrinos. For gamma rays, there are exciting new opportunities, due to detailed measurements of GeV solar gamma rays with Fermi, and unprecedented sensitivities in the TeV range with HAWC and LHAASO. For neutrinos, the enhanced flux, particularly at higher energies ($\sim$TeV), allows a more sensitive dark matter search with IceCube and KM3NeT. We show that these search channels can be extremely powerful, potentially improving sensitivity to the dark matter spin-dependent scattering cross section by several orders of magnitude relative to present searches for high-energy solar neutrinos, as well as direct detection experiments., Comment: 17 pages, 8 figures, updated with recent HAWC sensitivity, matches version published in PRD

In the simplified dark matter models commonly studied, the mass generation mechanism for the dark fields is not typically specified. We demonstrate that the dark matter interaction types, and hence the annihilation processes relevant for relic density and indirect detection, are strongly dictated by the mass generation mechanism chosen for the dark sector particles, and the requirement of gauge invariance. We focus on the class of models in which fermionic dark matter couples to a spin-1 vector or axial-vector mediator. However, in order to generate dark sector mass terms, it is necessary in most cases to introduce a dark Higgs field and thus a spin-0 scalar mediator will also be present. In the case that all the dark sector fields gain masses via coupling to a single dark sector Higgs field, it is mandatory that the axial-vector coupling of the spin-1 mediator to the dark matter is non-zero; the vector coupling may also be present depending on the charge assignments. For all other mass generation options, only pure vector couplings between the spin-1 mediator and the dark matter are allowed. If these coupling restrictions are not obeyed, unphysical results may be obtained such as a violation of unitarity at high energies. These two-mediator scenarios lead to important phenomenology that does not arise in single mediator models. We survey two-mediator dark matter models which contain both vector and scalar mediators, and explore their relic density and indirect detection phenomenology., Comment: 25 pages, 8 figures

We consider the indirect detection signals for a self-consistent hidden $U(1)$ model containing a Majorana dark matter candidate, $\chi$, a dark gauge boson, $Z'$, and a dark Higgs, $s$. Compared with a model containing only a dark matter candidate and $Z'$ mediator, the addition of the scalar provides a mass generation mechanism for the dark sector particles and is required in order to avoid unitarity violation at high energies. We find that the inclusion of the two mediators opens up a new two-body s-wave annihilation channel, $\chi\overline\chi\rightarrow sZ'$. This new process, which is missed in the usual single-mediator simplified model approach, can be the dominant annihilation channel. This provides rich phenomenology for indirect detection searches, allows indirect searches to explore regions of parameter space not accessible with other commonly considered s-wave annihilation processes, and enables both the $Z'$ and scalar couplings to be probed. We examine the phenomenology of the sector with a focus on this new process, and determine the limits on the model parameter space from Fermi data on dwarf spheriodal galaxies and other relevant experiments., Comment: 17 pages, 7 figures. v2: cross section corrected, qualitative conclusions unchanged; references added

We study mono-W signals of dark matter (DM) production at the LHC, in the context of gauge invariant renormalizable models. We analyze two simplified models, one involving an s-channel Z' mediator and the other a t-channel colored scalar mediator, and consider examples in which the DM-quark couplings are either isospin conserving or isospin violating after electroweak symmetry breaking. While previous work on mono-W signals have focused on isospin violating EFTs, obtaining very strong limits, we find that isospin violating effects are small once such physics is embedded into a gauge invariant simplified model. We thus find that the 8 TeV mono-W results are much less constraining than those arising from mono-jet searches. Considering both the leptonic (mono-lepton) and hadronic (mono fat jet) decays of the W, we determine the 14 TeV LHC reach of the mono-W searches with 3000 fb$^{-1}$ of data. While a mono-W signal would provide an important complement to a mono-jet discovery channel, existing constraints on these models imply it will be a challenging signal to observe at the 14 TeV LHC., Comment: 19 pages, 8 figures

Effective field theory (EFT) formulations of dark matter interactions have proven to be a convenient and popular way to quantify LHC bounds on dark matter. However, some of the non-renormalizable EFT operators considered do not respect the gauge symmetries of the Standard Model. We carefully discuss under what circumstances such operators can arise, and outline potential issues in their interpretation and application., Comment: 5 pages, 4 figures

We consider a scenario where dark matter (DM) interacts exclusively with Standard Model (SM) leptons at tree level. Due to the absence of tree-level couplings to quarks, the constraints on leptophilic dark matter arising from direct detection and hadron collider experiments are weaker than those for a generic WIMP. We study a simple model in which interactions of DM with SM leptons are mediated by a leptophilic $Z'$ boson, and determine constraints on this scenario arising from relic density, direct detection, and other experiments. We then determine current LHC limits and project the future discovery reach. We show that, despite the absence of direct interactions with quarks, this scenario can be strongly constrained., Comment: 12 pages, 15 figures