First- and second-order Raman spectra of carbonaceous material through successive contact and regional metamorphic events (Ryoke belt, SW Japan)

The evolution of both the first- and second-order Raman spectra of carbonaceous material (CM) through successive contact and regional metamorphic events is explored in the western part of the Ryoke belt (Iwakuni-Yanai area, SW Japan). Thirty-two metasedimentary rock samples were collected along a N-S gradient locally affected by contact metamorphism before and after the main regional tectono-metamorphic event (DP1). First-order spectra document a decreasing peak area ratio R2 and an increasing temperature TCM towards the south and the surrounding granitoids. Domains with intermediate (535–600 °C) TCM values match the extent of the pre-DP1 contact aureole but also image a so far unclear post-DP1 aureole. The axial part of the belt, likely unaffected by granite intrusions, preserves southward increasing TCM from 425 to 660 °C. Second-order spectra show a single S1 band that splits into two peaks (S1- and S1+) whose frequency difference ΔS1 increases stepwise towards the south. The spatial distribution of ΔS1 follows that of the E–W trending regional metamorphic zones. The splitting of S1 indicates a transition from two-dimensional to three-dimensional CM and occurs at ~500 °C, which seems to be common to all metamorphic belts worldwide. Despite regional metamorphism CM was able to record the post-DP1 contact overprint and there is no clear observation of delayed CM recrystallization, which likely depends on the crystallinity of the CM precursor. A discrepancy between first- and second-order Raman parameters suggests that they partly record the influence of different factors; R2 gives an account of thermal events, particularly those related to localized contact metamorphism, whereas ΔS1 potentially yields information on regional variations in heating duration and pressure. This demonstrates the potential of the full Raman spectrum of CM for deciphering the complex thermal history of orogenic systems

Multi-messenger searches via IceCube’s high-energy neutrinos and gravitational-wave detections of LIGO/Virgo

We summarize initial results for high-energy neutrino counterpart searches coinciding with gravitational-wave events in LIGO/Virgo\u27s GWTC-2 catalog using IceCube\u27s neutrino triggers. We did not find any statistically significant high-energy neutrino counterpart and derived upper limits on the time-integrated neutrino emission on Earth as well as the isotropic equivalent energy emitted in high-energy neutrinos for each event

In-situ estimation of ice crystal properties at the South Pole using LED calibration data from the IceCube Neutrino Observatory

The IceCube Neutrino Observatory instruments about 1 km3 of deep, glacial ice at the geographic South Pole using 5160 photomultipliers to detect Cherenkov light emitted by charged relativistic particles. A unexpected light propagation effect observed by the experiment is an anisotropic attenuation, which is aligned with the local flow direction of the ice. Birefringent light propagation has been examined as a possible explanation for this effect. The predictions of a first-principles birefringence model developed for this purpose, in particular curved light trajectories resulting from asymmetric diffusion, provide a qualitatively good match to the main features of the data. This in turn allows us to deduce ice crystal properties. Since the wavelength of the detected light is short compared to the crystal size, these crystal properties do not only include the crystal orientation fabric, but also the average crystal size and shape, as a function of depth. By adding small empirical corrections to this first-principles model, a quantitatively accurate description of the optical properties of the IceCube glacial ice is obtained. In this paper, we present the experimental signature of ice optical anisotropy observed in IceCube LED calibration data, the theory and parametrization of the birefringence effect, the fitting procedures of these parameterizations to experimental data as well as the inferred crystal properties.</p

Non-standard neutrino interactions in IceCube

Non-standard neutrino interactions (NSI) may arise in various types of new physics. Their existence would change the potential that atmospheric neutrinos encounter when traversing Earth matter and hence alter their oscillation behavior. This imprint on coherent neutrino forward scattering can be probed using high-statistics neutrino experiments such as IceCube and its low-energy extension, DeepCore. Both provide extensive data samples that include all neutrino flavors, with oscillation baselines between tens of kilometers and the diameter of the Earth. DeepCore event energies reach from a few GeV up to the order of 100 GeV - which marks the lower threshold for higher energy IceCube atmospheric samples, ranging up to 10 TeV. In DeepCore data, the large sample size and energy range allow us to consider not only flavor-violating and flavor-nonuniversal NSI in the μ−τ sector, but also those involving electron flavor. The effective parameterization used in our analyses is independent of the underlying model and the new physics mass scale. In this way, competitive limits on several NSI parameters have been set in the past. The 8 years of data available now result in significantly improved sensitivities. This improvement stems not only from the increase in statistics but also from substantial improvement in the treatment of systematic uncertainties, background rejection and event reconstruction

IceCube Search for Earth-traversing ultra-high energy Neutrinos

The search for ultra-high energy neutrinos is more than half a century old. While the hunt for these neutrinos has led to major leaps in neutrino physics, including the detection of astrophysical neutrinos, neutrinos at the EeV energy scale remain undetected. Proposed strategies for the future have mostly been focused on direct detection of the first neutrino interaction, or the decay shower of the resulting charged particle. Here we present an analysis that uses, for the first time, an indirect detection strategy for EeV neutrinos. We focus on tau neutrinos that have traversed Earth, and show that they reach the IceCube detector, unabsorbed, at energies greater than 100 TeV for most trajectories. This opens up the search for ultra-high energy neutrinos to the entire sky. We use ten years of IceCube data to perform an analysis that looks for secondary neutrinos in the northern sky, and highlight the promise such a strategy can have in the next generation of experiments when combined with direct detection techniques