DeepCore Detector Research Articles

IceCube at the frontier of macroscopic dark matter direct detection

For a class of macroscopic dark matter models, inelastic scattering of dark matter off a nucleus can generate electromagnetic signatures with GeV-scale energy. The IceCube detector, with its kilometer-scale size, is ideal for directly detecting such inelastic scattering. Based on the slow particle trigger for the DeepCore detector, we perform a detailed signal and background simulation to estimate the discovery potential. For order 1 GeV deposited energy in each interaction, we find that IceCube can probe the dark matter masses up to one gram.

Development of an analysis to probe the neutrino mass ordering with atmospheric neutrinos using three years of IceCube DeepCore data

The Neutrino Mass Ordering (NMO) remains one of the outstanding questions in the field of neutrino physics. One strategy to measure the NMO is to observe matter effects in the oscillation pattern of atmospheric neutrinos above sim 1,mathrm {GeV}, as proposed for several next-generation neutrino experiments. Moreover, the existing IceCube DeepCore detector can already explore this type of measurement. We present the development and application of two independent analyses to search for the signature of the NMO with three years of DeepCore data. These analyses include a full treatment of systematic uncertainties and a statistically-rigorous method to determine the significance for the NMO from a fit to the data. Both analyses show that the dataset is fully compatible with both mass orderings. For the more sensitive analysis, we observe a preference for normal ordering with a p-value of p_mathrm {IO} = 15.3% and mathrm {CL}_mathrm {s}=53.3% for the inverted ordering hypothesis, while the experimental results from both analyses are consistent within their uncertainties. Since the result is independent of the value of delta _mathrm {CP} and obtained from energies E_nu gtrsim 5,mathrm {GeV}, it is complementary to recent results from long-baseline experiments. These analyses set the groundwork for the future of this measurement with more capable detectors, such as the IceCube Upgrade and the proposed PINGU detector.

A search for sterile neutrinos with IceCube DeepCore

The DeepCore detector is a densely instrumented part of the IceCube Neutrino Observatory that lowers the neutrino detection threshold down to approximately 10 GeV resulting in the ability to measure atmospheric neutrino oscillations. The standard three neutrino mixing scenario can be tested by searching for an additional light sterile neutrino state, which does not interact via the standard weak interaction, but mixes with the three active neutrino states. This leads to an impact on the atmospheric neutrino oscillations below 100 GeV. We present improved limits to the sterile mixing element |Uτ4|2 using three years of the DeepCore data taken during 2011-2013.

Search for sterile neutrino mixing using three years of IceCube DeepCore data

We present a search for a light sterile neutrino using three years of atmospheric neutrino data from the DeepCore detector in the energy range of approximately $10-60~$GeV. DeepCore is the low-energy sub-array of the IceCube Neutrino Observatory. The standard three-neutrino paradigm can be probed by adding an additional light ($\Delta m_{41}^2 \sim 1 \mathrm{\ eV^2}$) sterile neutrino. Sterile neutrinos do not interact through the standard weak interaction, and therefore cannot be directly detected. However, their mixing with the three active neutrino states leaves an imprint on the standard atmospheric neutrino oscillations for energies below 100 GeV. A search for such mixing via muon neutrino disappearance is presented here. The data are found to be consistent with the standard three neutrino hypothesis. Therefore we derive limits on the mixing matrix elements at the level of $|U_{\mu4}|^2 < 0.11 $ and $|U_{\tau4}|^2 < 0.15 $ (90% C.L.) for the sterile neutrino mass splitting $\Delta m_{41}^2 = 1.0$ eV$^2$.

MeV–GeV neutrino propagation as a signal of magnetic field amplification in neutron star merger

Short gamma-ray bursts (sGRBs) have widely been accepted to arise from a compact object binary merger; neutron star–neutron star or neutron star–black hole. During the merger of a binary neutron star system, magnetic field can be amplified beyond magnetar field strength (∼1015–1016 G) by Kelvin–Helmholtz instabilities. Considering this effect on the GRB “fireball” dynamics, we study the emission, propagation and oscillation of multi MeV–GeV neutrinos through their self-energies and using these we compute the neutrino effective potential up to order MW−4. Additionally, we calculate the number of neutrino events and neutrino flavor ratios that we would expect on Hyper-Kamiokande and DeepCore experiments. We found that MeV neutrinos in a strong magnetic field could provide information of the topology of the field, and that the number of GeV neutrinos expected in DeepCore detector would be directly affected by the strength of the field. It is worth noting that our estimates correspond to the only trustworthy method for verifying the effect of the magnetic field amplification.

PINGU and the Neutrino Mass Hierarchy

The nature of the neutrino mass hierarchy is one of the most interesting open questions in particle physics today, and thus has drawn a great deal of attention from the neutrino physics community. The measurement of a large mixing angle between the first and third neutrino mass eigenstates has made possible several methods of measuring this hierarchy. One of these methods is a proposed expansion of the IceCube/DeepCore detector called PINGU (Precision IceCube Next Generation Upgrade) which would use atmospheric neutrinos to make the determination. This extension is made up of additional strings of optical sensors (similar to those already deployed in the IceCube detector) which will be located in the ice at the centre of IceCube. The spacing between these sensors would be smaller than even the existing DeepCore detector (both vertically and horizontally) and this increased density would permit the lowering of the neutrino detection threshold to substantially below 10 GeV. The physical nature of the detector as well as the methods used to make this measurement are presented.

PROPAGATION AND NEUTRINO OSCILLATIONS IN THE BASE OF A HIGHLY MAGNETIZED GAMMA-RAY BURST FIREBALL FLOW

Neutrons play an important role in the dynamics of gamma-ray bursts. The presence of neutrons in the baryon-loaded fireball is expected. If the neutrons abundance is comparable to that of protons, important features may be observed such as quasi-thermal multi-GeV neutrinos in coincidence with a subphotospheric $\gamma$-ray emission, nucleosynthesis at later times and rebrightening of the afterglow emission. Additionally, thermal MeV neutrinos are created by electron-positron annihilation, electron (positron) capture on protons (neutrons) and nucleonic bremsstrahlung. Although MeV neutrinos are difficult to detect, quasi-thermal GeV neutrinos are expected in km$^3$ detectors and/or DeepCore+IceCube. In this paper, we show that neutrino oscillations have outstanding implications for the dynamics of the fireball evolution and also that they can be detected through their flavor ratio on Earth. For that we derive the resonance and charged-neutrality conditions as well as the neutrino self-energy and effective potential up to order $m_W^{-4}$ at strong, moderate and weak magnetic field approximation to constrain the dynamics of the fireball. We found important implications: i) resonant oscillations are suppressed for high baryon densities as well as neutrons abundance larger than that of protons and ii) the effect of magnetic field is to decrease the proton-to-neutron ratio aside from the number of multi-GeV neutrinos expected in DeepCore detector. Also we estimate the GeV neutrino flavor ratios along the jet and on Earth.

Searching for the high-energy neutrino counterpart signals: The case of the Fermi bubbles signal and of dark matter annihilation in the inner Galaxy

The recent uncovering of the \textit{Fermi} Bubbles/haze in the \textit{Fermi} gamma-ray data has generated theoretical work to explain such a signal of hard $\gamma$-rays in combination with the \textit{WMAP} haze signal. Many of these theoretical models can have distinctively different implications with regards to the production of high energy neutrinos. We discuss the neutrino signals from different models proposed for the explanation of the \textit{Fermi} Bubbles/haze, more explicitly, from Dark Matter annihilation in the galactic halo with conditions of preferential CR diffusion, from recent AGN jet activity, from periodic diffusive shock acceleration, from stochastic 2nd order Fermi acceleration and from long time-scale star formation in the galactic center in combination with strong galactic winds. We find that some of these models will be probed by the IceCube DeepCore detector. Moreover, with a km$^3$ telescope located at the north hemisphere, we will be able to discriminate between the hadronic, leptonic and the DM models. Additionally using the reconstructed neutrino spectra we will probe annihilation of TeV scale dark matter towards the galactic center.

Measurement of Atmospheric Neutrino Oscillations with IceCube

We present the first statistically significant detection of neutrino oscillations in the high-energy regime (>20 GeV) from an analysis of IceCube Neutrino Observatory data collected in 2010 and 2011. This measurement is made possible by the low-energy threshold of the DeepCore detector (~20 GeV) and benefits from the use of the IceCube detector as a veto against cosmic-ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20-100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV-10 TeV) was extracted from IceCube data to constrain systematic uncertainties. The disappearance of low-energy upward-going muon neutrinos was observed, and the nonoscillation hypothesis is rejected with more than 5σ significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters |Δm(32)(2)|=(2.3(-0.5)(+0.6))×10(-3) eV(2) and sin(2)(2θ(23))>0.93, and maximum mixing is favored.

Sensitivities of the IceCube DeepCore detector to signatures of low-mass dark matter in the Galactic halo

We discuss the event rate in DeepCore array due to neutrino flux produced by annihilations and decays of galactic dark matter. This event rate is calculated with a 10 GeV threshold energy, which is smaller than the threshold energy taken in previous works. Taking into account the background event rate due to the atmospheric neutrino flux, we evaluate the sensitivity of DeepCore array for probing dark matter annihilation cross section and decay time. The sensitivity studies include the annihilation modes $\chi\chi\to b\bar{b}, \ \tau^+ \tau^-$, \ $\mu^+\mu^-$, and $\nu\bar{\nu}$, and decay modes $\chi\to b\bar{b}, \ \tau^+ \tau^-$, \ $\mu^+\mu^-$, and $\nu\bar{\nu}$. We compare our results with corresponding constraints derived from observations of WMAP, ACT and Fermi-LAT.

Neutrino Properties with Neutrino Telescopes

We show that atmospheric neutrinos in the IceCube Deep Core detector can be used to identify neutrino oscillations effects and measure neutrino properties.

Foreseeing Neutrino spectra in Deep Core

In the present paper we evaluate the effect of neutrino flavor mixing and possible CPT violation (MINOS like) for up-going atmospheric muon neutrinos measured with the Deep Core detector of the IceCube Neutrino Observatory at South Pole. Our evaluation of rate and spectrum is based on the known Cosmic Ray flux and its consequent atmospheric neutrino spectrum derived at Super-Kamiokande, and it takes into account propagation and flavor mixing inside the Earth, interaction into the Deep Core (variable) volume, and projection along the physical Deep Core detector. Our results differ from other ones; however when the Deep Core results will be available our predictions can be compared directly with them. Interestingly, the Minos CPT violation hint might be confirmed or not.The observed spectrum should also exhibit an anomalous minimum, due to neutrino oscillation, offering a "silent" narrow detection window for neutrinos with energies around 20 GeV, which could be very useful for a new Neutrino Astronomy.

A 20 GeVs transparent neutrino astronomy from the North Pole?

Muon neutrino astronomy is drown within a polluted atmospheric neutrino noise. However at 24 GeV energy atmospheric muon neutrinos, while rising vertically along the terrestrial diameter, should disappear (or be severely depleted) while converting into tau flavor: any rarest vertical 12 GeV muon track at South Pole Deep Core volume, pointing back to North Pole, might be tracing mostly a noise-free astrophysical signal. The corresponding Deep Core 6-7-8-9 channels trigger maybe point in those directions and inside that energy range without much background. Deep Core detector at South Pole, may scan at 18-27GeV energy windows, into a narrow vertical cone for a novel neutrino astronomy almost noise-free, pointing back toward the North Pole.Unfortunately muon at 12 GeV trace their arrival direction mostly spread around an unique string in a zenith-cone solid angle. To achieve also an azimuth angular resolution a two string detection at once is needed. The doubling of the Deep Core string number, (two new arrays of six string each, achieving an average detection distance of 36.5 m), is desirable, leading to a larger Deep Core detection mass (more than double) and a sharper zenith and azimuth angular resolution by two-string vertical axis detection. Such an improvement may show a noise free (at least factor ten) muon neutrino astronomy. This enhancement may also be a crucial probe of a peculiar anisotropy foreseen for atmospheric anti-muon, in CPT violated physics versus conserved one, following a hint by recent Minos results.