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 weakscale 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 χ ≳ 100 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 annihilationchannel branching ratios considerably weaken the sensitivity. For thermal WIMPs with s-wave 2 → 2 annihilation to visible final states, we find the dark matter mass is only known to be m χ ≳ 20 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 χ ≲ 100 TeV), it defines what we call the "WIMP window." To probe the remaining mass range, we outline ways forward.

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.

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 (∼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.

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 Lμ−Lτ number, $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$ U 1 L μ − L τ , 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.

We reexamine 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 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 the non-Poissonian template fitting 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.

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We analyze the Sun as a source for the indirect detection of dark matter through a search for gamma rays from the solar disk. Capture of dark matter by elastic interactions with the solar nuclei followed by annihilation to long-lived mediators can produce a detectable gamma-ray flux. We search 3 years of data from the High Altitude Water Cherenkov (HAWC) observatory and find no statistically significant detection of TeV gamma-ray emission from the Sun. Using this, we constrain the spin-dependent elastic scattering cross section of dark matter with protons for dark matter masses above 1 TeV, assuming a sufficiently long-lived mediator. The results complement constraints obtained from Fermi-LAT observations of the Sun and together cover WIMP masses between 4 and 10 6 GeV. In the optimal scenario, the cross-section constraints for mediator decays to gamma rays can be as strong as ∼10 −45 cm 2 , which is more than 4 orders of magnitude stronger than current direct-detection experiments for a 1 TeV dark matter mass. The cross-section constraints at higher masses are even better, nearly 7 orders of magnitude better than the current direct-detection constraints for a 100 TeV dark matter mass. This demonstration of sensitivity encourages detailed development of theoretical models in light of these powerful new constraints.

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 nonrenormalizable 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. PACS numbers: 95.35.+d, 12.15.Lk