Search

The active galaxy NGC 1068 was recently identified by the IceCube neutrino observatory as the first known steady-state, extragalactic neutrino point source, associated with about 79 events over ten years. We use the IceCube data to place limits on possible neutrino self-interactions mediated by scalar particles with mass between 1 - 10 MeV. We find that constraints on flavor-specific $\nu_{\tau}$ self-interactions with low mediator masses are comparable to constraints derived from the diffuse high-energy neutrino flux at low energies, while constraints on flavor-universal self-interactions are less restrictive than current bounds., Comment: 9 pages, 5 figures

Cosmic strings that couple to neutrinos may account for a portion of the high-energy astrophysical neutrino (HEAN) flux seen by IceCube. Here, we calculate the observed spectrum of neutrinos emitted from a population of cosmic string loops that contain quasi-cusps, -kinks, or kink-kink collisions. We consider two broad neutrino emission models: one where these string features emit a neutrino directly, and one where they emit a scalar particle which then eventually decays to a neutrino. In either case, the spectrum of cosmic string neutrinos does not match that of the observed HEAN spectrum. We thus find that the maximum contribution of cosmic string neutrinos, through these two scenarios, to be at most $\sim 45$ % of the observed flux. However, we also find that the presence of cosmic string neutrinos can lead to bumps in the observed neutrino spectrum. Finally, for each of the models presented, we present the viable parameter space for neutrino emission., Comment: 11 pages, 7 figures

Neutrinos are the Standard Model (SM) particles which we understand the least, often due to how weakly they interact with the other SM particles. Beyond this, very little is known about interactions among the neutrinos, i.e., their self-interactions. The SM predicts neutrino self-interactions at a level beyond any current experimental capabilities, leaving open the possibility for beyond-the-SM interactions across many energy scales. In this white paper, we review the current knowledge of neutrino self-interactions from a vast array of probes, from cosmology, to astrophysics, to the laboratory. We also discuss theoretical motivations for such self-interactions, including neutrino masses and possible connections to dark matter. Looking forward, we discuss the capabilities of searches in the next generation and beyond, highlighting the possibility of future discovery of this beyond-the-SM physics., Comment: Editors: Nikita Blinov, Mauricio Bustamante, Kevin J. Kelly, Yue Zhang. 29 pages, 16 figures, plus references. Contribution to Snowmass 2021

Dark matter particles can be gravitationally trapped by celestial bodies, motivating searches for localized annihilation or decay. If neutrinos are among the decay products, then IceCube and other neutrino observatories could detect them. We investigate this scenario for dark matter particles above $m_{\chi} \gtrsim$ PeV producing tau neutrino signals, using updated modeling of dark matter capture and thermalization. At these energies, tau neutrino regeneration is an important effect during propagation through Earth, allowing detection at distances far longer than one interaction length. We show how large energy loss of tau leptons above $\sim$ PeV drives a wide range of initial energies to the same final energy spectrum of "secondary" tau neutrinos at the detector, and we provide an analytic approximation to the numerical results. This effect enables an experiment to constrain decays that occur at very high energies, and we examine the reach of the IceCube high-energy starting event (HESE) sample in the parameter space of trapped dark matter annihilations and decays above PeV. We find that the parameter space probed by IceCube searches would require dark matter cross sections in tension with existing direct-detection bounds., Comment: Updated to include projected IceCube-Gen2 sensitivity, various minor revisions for clarity, some references added

If neutrinos have self-interactions, these will induce scatterings between astrophysical and cosmic neutrinos. Prior work proposed to look for possible resulting resonance features in astrophysical neutrino spectra in order to seek a neutrino self-interaction which can be either diagonal in the neutrino flavor space or couple different neutrino flavors. The calculation of the astrophysical spectra involves either a Monte Carlo simulation or a computationally intensive numerical integration of an integro-partial-differential equation. As a result only limited regions of the neutrino self-interaction parameter space have been explored, and only flavor-diagonal self-interactions have been considered. Here, we present a fully analytic form for the astrophysical neutrino spectra for arbitrary neutrino number and arbitrary self-coupling matrix that accurately obtains the resonance features in the observable neutrino spectra. The results can be applied to calculations of the diffuse supernova neutrino background and of the spectrum from high-energy astrophysical neutrino sources. We illustrate with a few examples., Comment: 11 pages, 8 figures

Popular accounts of exciting discoveries often draw students to physics and astronomy, but at the introductory level it is challenging to connect with these in a meaningful way. The use of real astronomical data in the classroom can help bridge this gap and build valuable quantitative and scientific reasoning skills. This paper presents a strategy for studying Hubble's Law and the accelerating expansion of the universe using actual data. Along with understanding the physical concepts, an explicit goal is to develop skills for analyzing data in terms of a model., Comment: Accepted & to appear in The Physics Teacher

New physics beyond the Standard Model could appear at long baseline oscillation experiments as non-standard interactions (NSI) between neutrinos and matter. If so, determination of the CP-violating phase $\delta_{13}$ is ambiguous due to interference with additional complex phases. I'll present my work using both numerical solutions and a perturbative approach to study oscillation probabilities in the presence of NSI. I'll show how the CP phase degeneracies are visualized on biprobability plots, and the extent to which the energy spectrum for a given baseline length can help resolve them. In particular, this shows how the broad range of energies at DUNE would help distinguish between maximal, standard CP violation and the absence of CP violation with large $\epsilon_{e\tau}$., Comment: Talk presented at CIPANP2018, based on arXiv:1806.09221

Non-standard interactions (NSI) between neutrinos and matter at long-baseline experiments could make determination of the CP-violating phase $\delta_{13}$ ambiguous due to interference with additional complex phases. Such degeneracies are often studied in the context of specific experiments and a few parameter choices, leaving it unclear how to extract a general understanding of when two sets of parameters may be degenerate or how different types of experiments in principle combine to lift such a degeneracy. This work complements detailed simulations of individual experiments by showing how underlying parameters relate to degeneracies as represented on a biprobability plot. We show how a range of energies near the oscillation maximum $\Delta_{31} = \pi/2$ separates some degenerate probabilities along the CP-conserving direction of biprobability space according to $\delta_{+} \equiv \delta_{13} + \delta_{e\tau}$, while near $\Delta_{31} = 3\pi/2$ degenerate probabilities are separated along the CP-violating direction according to $\delta_{e\tau}$. We apply this to the experimental hints that suggest $\delta_{13} \sim -\pi/2$ to see that this could also be consistent with $\delta_{13}, \delta_{e\tau} = 0$ or $\pi$. The baseline and energy range characteristic of DUNE provides some resolution, but a further improvement comes from beams a few degrees off-axis at $\gtrsim 1000$ km baselines, including some proposed sites for T2HKK., Comment: Version accepted & to appear in Nuclear Physics B

After inflation, a period of preheating may have produced a stochastic background of high frequency gravitational waves (GWs) that would persist until today. The nature of the inflaton's coupling to Standard Model or other fields is unknown, so it is useful to ask what features such fields may typically have, and how these affect predictions for the GW's produced. Here we consider the inflaton to be coupled to a light scalar field, and show that even a very small quartic self-interaction term will reduce the amplitude of the GW spectrum. For self-coupling $\lambda_{\chi} \gtrsim g^2$, where $g^2$ is the inflaton-scalar coupling, the peak energy density goes as $\Omega_{\rm gw}^{(\lambda_{\chi})} / \Omega_{\rm gw}^{(\lambda_{\chi}=0)} \sim (g^2/\lambda_{\chi})^{2}$. A consequence is that if the universe reheats through an inflaton-Higgs coupling then the spectrum would be suppressed but the dynamics would be sensitive to the Higgs potential near the energy scale of inflation., Comment: 19 pages, 4 figures. Added Section V and some references. Version accepted by PRD

In hidden sector models with an extra U(1) gauge group, new fields can interact with the Standard Model only through gauge kinetic mixing and the Higgs portal. After the U(1) is spontaneously broken, these interactions couple the resultant cosmic strings to Standard Model particles. We calculate the spectrum of radiation emitted by these "dark strings" in the form of Higgs bosons, Z bosons, and Standard Model fermions assuming that string tension is above the TeV scale. We also calculate the scattering cross sections of Standard Model fermions on dark strings due to the Aharonov-Bohm interaction. These radiation and scattering calculations will be applied in a subsequent paper to study the cosmological evolution and observational signatures of dark strings., Comment: 25 pages + 19 appendices / references ; 2 figures

We consider the Standard Model extended by a hidden sector U(1)_X symmetry that is spontaneously broken at the TeV scale by the vacuum expectation value of an additional scalar field. We study "dark string" solutions in this model and their properties due to the Higgs portal and gauge kinetic mixing operators. We find that dark strings effectively interact with Higgs and Z bosons by linear couplings, and with leptons and baryons via Aharonov-Bohm couplings, thus possibly leading to new cosmological constraints on dark matter models with spontaneously broken extra U(1) symmetry factors., Comment: 38 pages, 12 figures