Speaker: Tarak Nath Maity (Indian Institute of Science)
A search for dark matter using sub- PeV γ-rays observed by Tibet ASγ
The discovery of diffuse sub-PeV gamma-rays by the Tibet ASγ collaboration promises to revolutionize our understanding of the high-energy astrophysical universe. It has been shown that this data broadly agrees with prior theoretical expectations. In this talk, we will explore the impact of this discovery on a well-motivated new physics scenario: PeV-scale decaying dark matter (DM). Considering a wide range of final states in DM decay, a number of DM density profiles, and numerous astrophysical background models, we find that this data provides the most stringent limit on DM lifetime for various Standard Model final states. In particular, we find that the strongest constraints are derived for DM masses in between a few PeV to few tens of PeV.
Speaker: Bei Zhou
Dimuons in Neutrino Telescopes: New Predictions and First Candidates in IceCube
Neutrino telescopes are powerful probes of high-energy astrophysics and particle physics. Their power is increased when they can isolate different event classes, e.g., by flavor, though that is not the only possibility. Here we focus on a new event class for neutrino telescopes: dimuons, two energetic muons from one neutrino interaction. We make new theoretical and observational contributions. For the theoretical part, we calculate dimuon production cross sections and detection prospects via deep-inelastic scattering (DIS; where we greatly improve upon prior work) and W-boson production (WBP; where we present first results). We show that IceCube should have ≃400 dimuons (≃8 from WBP) in its current data and that IceCube-Gen2, with a higher threshold but a larger exposure, can detect ≃1200 dimuons (≃30 from WBP) in 10 years. These dimuons are almost all produced by atmospheric neutrinos. For the observational part, we perform a simple but conservative analysis of IceCube public data, finding the first candidate dimuon events (19 events). Though some IceCube experts we consulted argue these events cannot be real dimuons, (A) these events match well all aspects of our predictions and (B) no other compelling hypotheses have been raised. Whether these 19 events are real dimuons or some new background (or signal!), it is important to understand them. Here we share full details to help IceCube and to attract scrutiny from the broader community. Together, these theoretical and observational contributions help open a valuable new direction for neutrino telescopes, one especially important for probing high-energy QCD and new physics.
