The IceCube Neutrino Observatory at the South Pole, which detects Cherenkov light from charged particles produced in neutrino interactions, firmly established the existence of an astrophysical ...high-energy neutrino component. Here I present IceCube’s High-Energy Starting Event sample and the new results obtained with a livetime of about 7.5 years. I will focus on the new measurement of the flavor composition performed using this sample. IceCube is directly sensitive to each neutrino flavor via the single cascade, track and double cascade event topologies, the latter being the topology produced in tauneutrino interactions above an energy threshold of ~100 TeV. A measurement of the flavor ratio on Earth can provide important constraints on sources and production mechanisms within the standard model, and also constrain various beyond-standard-model processes.
Das IceCube Neutrino Observatorium am Südpol hat die Existenz eines diffusen astrophysikalischen Neutrinoflusses nachgewiesen. Die Flavor-Zusammensetzung astrophysikalischer Neutrinos trägt ...Informationen über Orte kosmischer Teilchenbeschleunigung und Auswirkungen potenzieller neuer Physik auf die Neutrinoausbreitung. Zur seiner Bestimmung ist die Beobachtung von Tau-Neutrinos nötig. Ab einer Energie von ~O(100 TeV) kann deren Wechselwirkung über geladene Ströme eine Doppelkaskaden-Topologie ergeben, bei der die zwei Energiedepositionen am Tau-Entstehungs- und Tau-Zerfallsvertex aufgelöst werden können. Diese wird zusammen mit den bereits bekannten Topologien Einzel-Kaskade und Spur zur Messung der Flavor-Zusammensetzung auf der Erde benutzt. In dieser Arbeit werden im Detektorvolumen von IceCube anfangende Ereignisse mit hohen Energien algorithmisch in drei Topologien klassifiziert. Im Datensatz mit einer Lebensdauer von 7.5 Jahren werden zum ersten Mal zwei Doppelkaskaden identifiziert; diese sind Kandidaten für Tau-Neutrinos. Die Eigenschaften der zwei Tau-Neutrino-Kandidaten werden in einer a-posteriori Analyse im Detail studiert. Die statistische Methode wird durch einen Log-Likelihood-Quotienten-Test mit multi-dimensionalen Wahrscheinlichkeitsdichten verbessert. Eine der Doppelkaskaden ist konsistent mit dem Szenario einer misklassifizierten Einzelkaskade, während für die zweite Doppelkaskade die Wahrscheinlichkeit eines nicht-Tau-Neutrino Szenarios auf nur 3% bestimmt wird. Die gemessene Flavor-Zusammensetzung ist konsistent mit der Annahme von astrophysikalischen Neutrinos sowie mit bisher veröffentlichen Resultaten. Die Messung ergibt einen astrophysikalischen Tau-Neutrino Fluss von dPhi / dE=3.0 (-1.8,+2.2) (E / 100TeV)^(-2.87) 10^(-18) GeV^(-1) cm^(-2) s^(-1) sr^(-1), was dem ersten positiven Ergebnis für die Tau-Normalisierung entspricht. Die Nichtexistenz eines astrophysikalischen Tau-Neutrino Flusses wird mit einer Signifikanz von 2.8 sigma abgelehnt.
The IceCube neutrino observatory at the South Pole has confirmed the existence of a diffuse astrophysical neutrino flux. The flavor composition of astrophysical neutrinos carries information on the environments at the sites of cosmic particle acceleration as well as potential imprints of new physics acting during neutrino propagation. To measure the flavor composition the observation of the long-elusive tau neutrinos is required. Starting at an energy of ~O(100 TeV) a tau neutrino charged current interaction can produce a double cascade topology, where the two energy depositions from the tau creation and the tau decay vertices are resolvable. This topology together with the well-established track and single cascade topology is used to measure the flavor composition on Earth. In this work, high-energy events starting in IceCube's detector volume are classified algorithmically into the three topologies. In the dataset with a livetime of 7.5 years, two events are classified as double cascades for the first time, yielding multi-TeV tau-neutrino candidates. The properties of the two tau-neutrino candidates are investigated in an a-posteriori analysis. The statistical method is improved by performing a log-likelihood-ratio test using multi-dimensional probability densities. One of the double cascades is consistent with being a misclassified single cascade, while the second double cascade is found to have a misclassification probability of only 3%. The measured flavor composition nu_e:nu_mu:nu_tau = 0.20:0.39:0.42 is consistent with astrophysical neutrinos and with previously published results. The astrophysical tau-neutrino flux is measured to dPhi / dE=3.0 (-1.8,+2.2) (E / 100TeV)^(-2.87) 10^(-18) GeV^(-1) cm^(-2) s^(-1) sr^(-1) with spectral index gamma=2.87 (-0.20,+0.21), yielding the first non-zero results for the tau normalization. The absence of an astrophysical tau-neutrino flux is disfavored at 2.8 sigma.
Tau neutrinos in the next decade: from GeV to EeV Abraham, Roshan Mammen; Alvarez-Muñiz, Jaime; Argüelles, Carlos A ...
Journal of physics. G, Nuclear and particle physics,
11/2022, Volume:
49, Issue:
11
Journal Article
The IceCube Neutrino Observatory at the South Pole, which detects Cherenkov light from charged particles produced in neutrino interactions, firmly established the existence of an astrophysical ...high-energy neutrino component. Here I present IceCube's High-Energy Starting Event sample and the new results obtained with a livetime of about 7.5 years. I will focus on the new measurement of the flavor composition performed using this sample. IceCube is directly sensitive to each neutrino flavor via the single cascade, track and double cascade event topologies, the latter being the topology produced in tau-neutrino interactions above an energy threshold of ~100 TeV. A measurement of the flavor ratio on Earth can provide important constraints on sources and production mechanisms within the standard model, and also constrain various beyond-standard-model processes.
Project 8 is a next generation experiment aiming to directly measure the neutrino mass using the tritium endpoint method with a targeted sensitivity of 40 meV. Having established a new measuring ...technique, Cyclotron Radiation Emission Spectroscopy (CRES), the next development phase will demonstrate CRES on a large source volume, culminating in a pilot-scale CRES experiment with atomic tritium. A promising option is a mode-filtered, cylindrical, resonant cavity in which cyclotron radiation from magnetically trapped beta electrons only couples to the lowest eigenmode, maximizing effective volume and minimizing signal complexity. Recent progress in the experiment design, including a small scale cavity CRES proof-of-concept apparatus to demonstrate CRES in cavities and its scalability to large volumes are described.
The IceCube Neutrino Observatory at the South Pole, which detects Cherenkov light from charged particles produced in neutrino interactions, firmly established the existence of an astrophysical ...high-energy neutrino component. The expected neutrino flavor composition on Earth is \(\nu_e:\nu_{\mu}:\nu_{\tau}\) of about 1:1:1 for neutrinos produced in astrophysical sources through pion decay. A measurement of the flavor composition on Earth can provide important constraints on sources and production mechanisms within the standard model, and can also constrain various beyond-standard-model processes. Here the measurement of the flavor composition performed on IceCube's High-Energy Starting Events sample with a livetime of about 7.5 years is presented. IceCube is directly sensitive to each neutrino flavor via the single cascade, track and double cascade event topologies. In IceCube, \(\nu_{\tau}\)-CC interactions above \(\sim\) 100 TeV can produce resolvable double cascades, breaking the degeneracy between \(\nu_e\) and \(\nu_{\tau}\) present at lower energies. IceCube's first two identified double cascades are presented and the properties of the two \(\nu_{\tau}\) candidates are discussed.
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