Lutz Koepke

The Wavelength-shifting Optical Module (WOM) is a novel photosensor concept for the instrumentation of large detector volumes with single-photon sensitivity. The key objective is to improve the signal-to-noise ratio, which is achieved by decoupling the photosensitive area of a sensor from the cathode area of its photomultiplier tube (PMT). The WOM consists of a transparent tube with two PMTs attached to its ends. The tube is coated with wavelength-shifting paint that absorbs ultraviolet photons with nearly 100% efficiency. Depending on the environment, e.g., air (ice), up to 73% (41%) of the subsequently emitted optical photons can be captured by total internal reflection and propagate towards the PMTs, where they are recorded. The optical properties of the paint, the geometry of the tube, and the coupling of the tube to the PMTs have been optimized for maximal sensitivity based on theoretical derivations and experimental evaluations. Prototypes were built to demonstrate the technique and to develop a reproducible construction process. Important measurable characteristics of the WOM are the wavelength-dependent effective area, the transit time spread of detected photons, and the signal-to-noise ratio. The WOM outperforms bare PMTs, especially with respect to the low signal-to-noise ratio with an increase of a factor up to 8.9 in air (5.2 in ice). Since the gain in sensitivity is mostly in the UV regime, the WOM is an ideal sensor for Cherenkov and scintillation detectors.

Papers on searches for beyond the standard model physics, submitted to the 35th International Cosmic Ray Conference (ICRC 2017, Busan, South Korea) by the IceCube Collaboration

IceCube, a cubic kilometer Cherenkov detector, is an ideal instrument for the detection of astrophysical neutrino fluxes and rare interactions of exotic particles. One way to advance IceCube neutrino analyses would be the development of methods to identify the neutrino flavor and reaction type. While charged current interactions leading to long tracks of charged muons can be easily distinguished from those leading to particle cascades of O(10) m extension, the 17 m sensor distance makes it very challenging to identify the type of cascade as being due to the fragmentation of the struck nucleus or due to showers initiated by electrons or tauons. Only at very high energies, the average tau flight distance of 50 m/PeV, in principle, allows one to identify a tau-neutrino interaction. So far, IceCube has not registered telltale events of such kind. The creation of neutrons, spallation products and muons in hadronic showers offers an alternative handle to identify a hadronic interaction. However, the regular data acquisition system is restricted to a O(10) microsecond readout window, limiting the detection to relativistic or low relativistic particles. Recently, the development of a spooling system to store the complete detector hit map for a configurable time interval made it possible to register a potential "afterglow" of highly energetic events. While the signal from Michel electrons from muon decay will be difficult to extract due to light scattering in the ice and afterpulses of the PMTs, the detection of 2.224 MeV photons from neutron capture on hydrogen is promising due to the low PMT dark rates of the sensors in IceCube. One should note that luminescence in the ice could be a competing effect. In this paper, we summarize the physics scope and particle identification opportunities, study the underlying physics of delayed signals and the expected detector response in a Cherenkov detector, discuss a newly installed automatic real time triggering system, with emphasis on the the capabilities and limitations of the data acquisition system for such an analysis, and outline the expected potential of IceCube for particle identification through the use of delayed signals.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

This paper describes the response of the IceCube neutrino telescope located at the geographic south pole to outbursts of MeV neutrinos from the core collapse of nearby massive stars. IceCube was completed in December 2010 forming a lattice of 5160 photomultiplier tubes that monitor a volume of ~1 km3 in the deep Antarctic ice for particle induced photons. The telescope was designed to detect neutrinos with energies greater than 100 GeV. Owing to subfreezing ice temperatures, the photomultiplier dark noise rates are particularly low. Hence IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photomultiplier rates on top of the dark noise. With 2 ms timing resolution, IceCube can detect subtle features in the temporal development of the supernova neutrino burst. For a supernova at the galactic center, its sensitivity matches that of a background-free megaton-scale supernova search experiment. The sensitivity decreases to 20 standard deviations at the galactic edge (30 kpc) and 6 standard deviations at the Large Magellanic Cloud (50 kpc). IceCube is sending triggers from potential supernovae to the Supernova Early Warning System. The sensitivity to neutrino properties such as the neutrino hierarchy is discussed, as well as the possibility to

IceCube was completed in December 2010. It forms a lattice of 5160 photomultiplier tubes that monitor a volume of ~ 1 cubic km in the deep Antarctic ice for particle induced photons. The telescope was designed to detect neutrinos with energies greater than 100 GeV. Owing to subfreezing ice temperatures, the photomultiplier dark noise rates are particularly low. Hence IceCube can also detect large numbers of MeV neutrinos by observing a collective rise in all photomultiplier rates on top of the dark noise. With 2 ms timing resolution, IceCube can track subtle features in the temporal development of the supernova neutrino burst. For a supernova at the galactic center, its sensitivity matches that of a background-free megaton-scale supernova search experiment. The sensitivity decreases to 20 standard deviations at the galactic edge (30 kpc) and 6 standard deviations at the Large Magellanic Cloud (50 kpc). IceCube is sending triggers from potential supernovae to the Supernova Early Warning System. The sensitivity to neutrino properties such as the neutrino hierarchy is discussed and simulations of tantalizing signatures, such as the formation of a quark star or a black hole as well as the characteristics of shock waves are presented. All results are preliminary.