Atmospheric Muon Neutrinos Research Articles

Searches for Sterile Neutrinos with the IceCube Detector.

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320GeV to 20TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous ν_{μ} or ν[over ¯]_{μ} disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the 3+1 model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to sin^{2}2θ_{24}≤0.02 at Δm^{2}∼0.3 eV^{2} at the 90%confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99%confidence level for the global best-fit value of |U_{e4}|^{2}.

Charm contribution to the atmospheric neutrino flux

We revisit the estimate of the charm particle contribution to the atmospheric neutrino flux that is expected to dominate at high energies because long-lived high-energy pions and kaons interact in the atmosphere before decaying into neutrinos. We focus on the production of forward charm particles which carry a large fraction of the momentum of the incident proton. In the case of strange particles, such a component is familiar from the abundant production of $K^{+} \Lambda$ pairs. These forward charm particles can dominate the high-energy atmospheric neutrino flux in underground experiments. Modern collider experiments have no coverage in the very large rapidity region where charm forward pair production dominates. Using archival accelerator data as well as IceCube measurements of atmospheric electron and muon neutrino fluxes, we obtain an upper limit on forward $\bar{D}^0 \Lambda_c$ pair production and on the associated flux of high-energy atmospheric neutrinos. We conclude that the prompt flux may dominate the much-studied central component and represent a significant contribution to the TeV atmospheric neutrino flux. Importantly, it cannot accommodate the PeV flux of high-energy cosmic neutrinos, nor the excess of events observed by IceCube in the 30--200 TeV energy range indicating either structure in the flux of cosmic accelerators, or a presence of more than one component in the cosmic flux observed.

Precision measurement of neutrino oscillation parameters at INO-ICAL detector

A magnetized Iron CALorimeter (ICAL) detector at the India-based neutrino observatory (INO) is used to study neutrino oscillation sensitivity using atmospheric muon neutrino source. The ICAL detector will be able to detect muon tracks and hadron showers produced by neutrino interactions with the iron target. We have performed precision measurement analysis for the atmospheric neutrino oscillation parameters with the muon neutrino events, generated by Monte Carlo NUANCE event generator. A marginalized χ2 analysis based on reconstructed neutrino energy and muon zenith angle binning scheme has been performed to determine the sensitivity for the atmospheric neutrino mixing parameters, \(\sin ^{2}\theta _{23}\) and \(| {\Delta } m^{2}_{23}|\).

IceCube Results and PINGU Perspectives

The last three years of IceCube operation with the completed detector have resulted in a plethora of results, including the first observation of high energy astrophysical neutrinos, tests of a possible neutrino flux from atmospheric charm meson decay, and competitive results of neutrino oscillation from atmospheric muon neutrino disappearance. Based on the success of IceCube, a new low energy in-fill, known as the Precision IceCube Next Generation Upgrade, is being proposed with the primary physics goal of resolving the ordering of the neutrino mass hierarchy.

PINGU and the neutrino mass hierarchy: Statistical and systematic aspects

The proposed PINGU project (Precision IceCube Next Generation Upgrade) is expected to collect $O({10}^{5})$ atmospheric muon and electron neutrino events in a few years of exposure, and to probe the neutrino mass hierarchy through its imprint on the event spectra in energy and direction. In the presence of non-negligible and partly unknown shape systematics, the analysis of high-statistics spectral variations will face subtle challenges that are largely unprecedented in neutrino physics. We discuss these issues both on general grounds and in the currently envisaged PINGU configuration, where we find that possible shape uncertainties at the (few) percent level can noticeably affect the sensitivity to the hierarchy. We also discuss the interplay between the mixing angle ${\ensuremath{\theta}}_{23}$ and the PINGU sensitivity to the hierarchy. Our results suggest that more refined estimates of spectral uncertainties are needed in next-generation, large-volume atmospheric neutrino experiments.

Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data

We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 GeV and 100 GeV, where a strong disappearance signal is expected. The detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by $\Delta m^2_{32}=2.72^{+0.19}_{-0.20}\times 10^{-3}\,\mathrm{eV}^2$ and $\sin^2\theta_{23} = 0.53^{+0.09}_{-0.12}$ (normal mass hierarchy assumed). The results are compatible and comparable in precision to those of dedicated oscillation experiments.

The sensitivity of the ICAL detector at India-based Neutrino Observatory to neutrino oscillation parameters

The India-based Neutrino Observatory (INO) will host a 50 kt magnetized iron calorimeter (ICAL) detector that will be able to detect muon tracks and hadron showers produced by Charged-Current muon neutrino interactions in the detector. The ICAL experiment will be able to determine the precision of atmospheric neutrino mixing parameters and neutrino mass hierarchy using atmospheric muon neutrinos through earth matter effect. In this paper, we report on the sensitivity for the atmospheric neutrino mixing parameters ($\sin^{2}\theta_{23}$ and $|\Delta m^{2}_{32}|$) for the ICAL detector using the reconstructed neutrino energy and muon direction as observables. We apply realistic resolutions and efficiencies obtained by the ICAL collaboration with a GEANT4-based simulation to reconstruct neutrino energy and muon direction. Our study shows that using neutrino energy and muon direction as observables for a $\chi^{2}$ analysis, ICAL detector can measure $\sin^{2}\theta_{23}$ and $|\Delta m^{2}_{32}|$ with 13% and 4% uncertainties at 1$\sigma$ confidence level for 10 years of exposure.

Development of a general analysis and unfolding scheme and its application to measure the energy spectrum of atmospheric neutrinos with IceCube: IceCube Collaboration.

We present the development and application of a generic analysis scheme for the measurement of neutrino spectra with the IceCube detector. This scheme is based on regularized unfolding, preceded by an event selection which uses a Minimum Redundancy Maximum Relevance algorithm to select the relevant variables and a random forest for the classification of events. The analysis has been developed using IceCube data from the 59-string configuration of the detector. 27,771 neutrino candidates were detected in 346 days of livetime. A rejection of 99.9999 % of the atmospheric muon background is achieved. The energy spectrum of the atmospheric neutrino flux is obtained using the TRUEE unfolding program. The unfolded spectrum of atmospheric muon neutrinos covers an energy range from 100 GeV to 1 PeV. Compared to the previous measurement using the detector in the 40-string configuration, the analysis presented here, extends the upper end of the atmospheric neutrino spectrum by more than a factor of two, reaching an energy region that has not been previously accessed by spectral measurements.

Measurement of Atmospheric Neutrino Oscillations with IceCube/DeepCore in its 79-string Configuration

With its low-energy extension DeepCore, the IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station is able to detect neutrino events with energies as low as 10GeV. This permits the investigation of flavor oscillations of atmospheric muon neutrinos in an energy range not covered by other experiments, opening a new window on the physics of atmospheric neutrino oscillations. The oscillation probability depends on the observed neutrino zenith angle and energy. Maximum disappearance is expected for vertically upward moving muon neutrinos at around 25GeV. A recent analysis has rejected the non-oscillation hypothesis with a significance of about 5 σ based on data obtained with IceCube while it was operating in its 79-string configuration [1]. The analysis presented here uses data from the same detector configuration, but implements a more powerful approach for the event selection, which yields a dataset with an order of magnitude higher statistics (more than 8 000 events). We present new results based on a likelihood analysis of the two observables zenith angle and energy. The non-oscillation hypothesis is rejected with a significance32 of about 5.7 σ. In the 2-flavor approximation, our best-fit oscillation parameters are Δm2 = (2.2 ± 0.5) · 10−3eV2 and0.14 sin2 (2θ23) = 1.0+0-0.14, in good agreement with measurements at lower energy.

Characterization of 3 mm glass electrodes and development of RPC detectors for INO-ICAL experiment

India-based Neutrino Observatory (INO) is a multi-institutional facility, planned to be built up in South India. The INO facility will host a 51kton magnetized Iron CALorimeter (ICAL) detector to study atmospheric muon neutrinos. Iron plates have been chosen as the target material whereas Resistive Plate Chambers (RPCs) have been chosen as the active detector element for the ICAL experiment. Due to the large number of RPCs needed (~28,000 of 2m×2m in size) for ICAL experiment and for the long lifetime of the experiment, it is necessary to perform a detailed R&D such that each and every parameter of the detector performance can be optimized to improve the physics output. In this paper, we report on the detailed material and electrical properties studies for various types of glass electrodes available locally. We also report on the performance studies carried out on the RPCs made with these electrodes as well as the effect of gas composition and environmental temperature on the detector performance. We also lay emphasis on the usage of materials for RPC electrodes and the suitable environmental conditions applicable for operating the RPC detector for optimal physics output at INO-ICAL experiment.

Measurement of the atmospheric νe flux in IceCube.

We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80GeV and 6TeV, using data recorded during the first year of operation of IceCube's DeepCore low-energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496±66(stat)±88(syst) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range.

Neutrino Oscillations in the Atmospheric Parameter Region: From the Early Experiments to the Present

The aim of this paper is to provide a historical perspective on the main experimental steps which led to the current picture of neutrino oscillations in the &#x201c;atmospheric parameter region.&#x201d; In the 1980s a deficit of atmospheric muon neutrinos was observed with the first generation of underground experiments. In the following decade new experiments provided fundamental results which led to the discovery claims in 1998. At the beginning of the new century neutrino beams of medium and high energy became available and several long baseline experiments were performed and added new information to the atmospheric neutrino puzzle. The interpretation of the results of atmospheric and long baseline neutrino experiments was in terms of dominant <svg style="vertical-align:-5.76988pt;width:63.137501px;" id="M1" height="14.925" version="1.1" viewBox="0 0 63.137501 14.925" width="63.137501" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,7.675)"><path id="x1D708" d="M509 373q0 -52 -42.5 -118.5t-124.5 -159.5l-94 -107h-27q-22 209 -78 342q-21 48 -41 48q-18 0 -63 -62l-22 21q77 111 125 111q30 0 52 -21.5t38 -75.5q37 -130 52 -285q48 62 74.5 99.5t53.5 87t27 76.5q0 43 -17 60q-5 5 -5 15q0 17 12.5 30.5t28.5 13.5&#xA;q21 0 36 -22.5t15 -52.5z" /></g> <g transform="matrix(.012,-0,0,-.012,9.1,11.762)"><path id="x1D707" d="M538 96q-38 -45 -84 -76.5t-71 -31.5q-44 0 -15 117q12 49 18 89h-2q-99 -128 -163 -178q-36 -28 -70 -28q-26 0 -44 38h-2q-16 -69 -16 -129q0 -43 11 -75.5t24 -42.5l1 -6q-7 -12 -24.5 -23t-37.5 -11q-40 0 -40 76q0 52 35 202l94 407l78 24l5 -5q-32 -122 -72 -310&#xA;q-7 -33 0 -55t25 -22q36 0 105.5 75t107.5 145l32 146l75 26h10q-50 -197 -78 -347q-7 -38 6 -38q7 0 31 17t47 39z" /></g> <g transform="matrix(.017,-0,0,-.017,23.888,7.675)"><path id="x2192" d="M901 255q-71 -62 -185 -187l-22 15l102 147h-727v50h727l-102 147l22 15q114 -125 185 -187z" /></g><g transform="matrix(.017,-0,0,-.017,47.652,7.675)"><use xlink:href="#x1D708"/></g> <g transform="matrix(.012,-0,0,-.012,56.7,11.762)"><path id="x1D70F" d="M471 456q-22 -60 -37 -85q-20 -3 -84 -3q-9 0 -29 2t-29 2q-38 -145 -54 -234q-15 -80 14 -80q23 0 68 38l14 -25q-78 -83 -137 -83q-50 0 -50 64q0 25 7 57l67 266q-57 4 -98 -9t-80 -49l-20 21q14 18 27 31t36.5 30t56.5 26t73 9q26 0 82.5 -2t89.5 -2q21 0 32 5t24 24&#xA;z" /></g> </svg> oscillations. Short recollections are made of the SNO solar neutrino measurements, of the results with neutrino telescopes, and of reactor neutrinos to measure sin<sup >2</sup><svg style="vertical-align:-3.3907pt;width:20.637501px;" id="M2" height="16.450001" version="1.1" viewBox="0 0 20.637501 16.450001" width="20.637501" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,12.162)"><path id="x1D703" d="M475 507q0 -83 -20 -172t-56 -167.5t-93.5 -129t-125.5 -50.5q-157 0 -157 227q0 78 21.5 164t59 161t96.5 123.5t126 48.5q79 0 114 -58t35 -147zM391 522q0 155 -81 155q-62 0 -111 -82.5t-73 -200.5h253q12 81 12 128zM373 346h-255q-12 -91 -12 -150q0 -72 20 -123&#xA;t63 -51q34 0 64 28.5t52.5 77t39 103t28.5 115.5z" /></g> <g transform="matrix(.012,-0,0,-.012,8.525,16.25)"><path id="x31" d="M384 0h-275v27q67 5 81.5 18.5t14.5 68.5v385q0 38 -7.5 47.5t-40.5 10.5l-48 2v24q85 15 178 52v-521q0 -55 14.5 -68.5t82.5 -18.5v-27z" /></g><g transform="matrix(.012,-0,0,-.012,14.236,16.25)"><path id="x33" d="M285 378v-2q65 -13 102 -54.5t37 -97.5q0 -57 -30.5 -104.5t-74 -75t-85.5 -42t-72 -14.5q-31 0 -59.5 11t-40.5 23q-19 18 -16 36q1 16 23 33q13 10 24 0q58 -51 124 -51q55 0 88 40t33 112q0 64 -39 96.5t-88 32.5q-29 0 -64 -11l-6 29q77 25 118 57.5t41 84.5&#xA;q0 45 -26.5 69.5t-68.5 24.5q-67 0 -120 -79l-20 20l43 63q51 56 127 56h1q66 0 107 -37t41 -95q0 -42 -31 -71q-22 -23 -68 -54z" /></g> </svg>. Over the years the phenomenological picture improved in completeness and increased in complexity. A short perspective concludes the paper.

High-energy spectra of atmospheric neutrinos

A calculation of the atmospheric high-energy muon neutrino spectra and zenith-angle distributions is performed for two primary spectrum parameterizations (by Gaisser and Honda and by Zatsepin and Sokolskaya) with the use of QGSJET-II-03 and SIBYLL 2.1 hadronic models. A comparison of the zenith angle-averaged muon neutrino spectrum with the data of Frejus, AMANDA-II, and IceCube40 experiments makes it clear that, even at energies above 100 TeV, the prompt neutrino contribution is not apparent because of the considerable uncertainties of the experimental data in the high-energy region.

BEAMING NEUTRINOS AND ANTI-NEUTRINOS ACROSS THE EARTH TO DISENTANGLE NEUTRINO MIXING PARAMETERS

A MINOS result seemed to hint a different anti-neutrino mass splitting and mixing angle with respect to the neutrino ones, offering a hint for a CPT violation in lepton sector. However more recent MINOS data reduced the neutrino-antineutrino differences leading to a narrow discrepancy almost compatible with no CPT violation, hard to be disentangled. Moreover last a few years of OPERA activity on tau appearance is still un-probed (one unique event). Both flavor muon-tau mixing, tau appearance and eventual CPT violation disentanglement need more tools to be enhanced. Atmospheric muon neutrino spectra and anisotropy in Deep Core at ten-tens GeV (yet unpublished) may test the muon-tau conversion but they can hardly reveal such last tiny MINOS CPT asymmetry. We show how the longest baseline neutrino oscillation available, crossing most of the Earth diameter, within an OPERA-like experiment from CERN (or FERMILAB) to ICECUBE-Deep Core neutrino detector at 21 GeV energy, may at best disentangle even last tiny CPT violation (within 6 sigma a year) while testing at highest rate tau-antitau appearance. We propose the muon neutrino disappearance or (for any CPT violation) the partial anti-muon appearance at the longest distances. Such a tuned detection experiment may lead to a clear and strong signature of tau or anti-tau generation (even within its neutral current noise background events): nearly one antitau or two tau a day. The tau appearance signal is above (or within) 10 sigma a year, even for 1% OPERA-like experiment. Peculiar configurations for theta_13 angle test and hierarchy neutrino mass test may also be addressed by a Deep Core-PINGU array detector observing electron neutrino shower at 6 GeV neutrino energy windows.

Atmospheric neutrinos as a probe ofeV2-scale active-sterile oscillations

The downgoing atmospheric ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ and ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ fluxes can be significantly altered due to the presence of ${\mathrm{eV}}^{2}$-scale active-sterile oscillations. We study the sensitivity of a large liquid argon detector and a large magnetized iron detector (like the proposed ICAL at INO) to these oscillations. Such oscillations are indicated by results from LSND, and more recently, from MiniBooNE and from reanalyses of reactor experiments following recent recalculations of reactor fluxes. There are other tentative indications of the presence of sterile states in both the $\ensuremath{\nu}$ and $\overline{\ensuremath{\nu}}$ sectors as well. Using the allowed sterile parameter ranges in a $3+1$ mixing framework in order to test these results, we perform a fit assuming active-sterile oscillations in both the muon neutrino and antineutrino sectors, and compute oscillation exclusion limits using atmospheric downgoing muon neutrino and antineutrino events. We find that (for both ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ and ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$) a liquid argon detector, an ICAL-like detector or a combined analysis of both detectors with an exposure of $1\text{ }\text{ }\mathrm{Mt}/\mathrm{yr}$ provides significant sensitivity to regions of parameter space in the range $0.1&lt;\ensuremath{\Delta}{m}^{2}&lt;5\text{ }\text{ }{\mathrm{eV}}^{2}$ for ${sin}^{2}2{\ensuremath{\Theta}}_{\ensuremath{\mu}\ensuremath{\mu}}\ensuremath{\ge}0.08$. Thus atmospheric neutrino experiments can provide complementary coverage in these regions, improving sensitivity limits in combination with bounds from other experiments on these parameters. We also analyze the bounds using muon antineutrino events only and compare them with the results from MiniBooNE.

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.

Downward-going tau neutrinos as a new prospect of detecting dark matter

Dark matter trapped in the Sun produces a flux of all flavors of neutrinos, which then reach the Earth after propagating out of the Sun and oscillating from the production point to the detector. The typical signal which is looked at refers to the muon neutrino component and consists of a flux of up-going muons in a neutrino detector. We propose instead a novel signature: the possibility of looking at the tau neutrino component of the dark matter signal, which is almost background-free in the downward-going direction, since the tau neutrino amount in atmospheric neutrinos is negligible and in the down-going baseline atmospheric muon-neutrinos have no time to sizably oscillate. We analyze the prospects of studying the downward-going tau neutrinos from dark matter annihilation (or decay) in the Sun in Cherenkov detectors, by looking at hadronic showers produced in the charged-current tau neutrino interactions and subsequent tau decay. We discuss the various sources of background (namely the small tau neutrino component in atmospheric neutrinos, both from direct production and from oscillations; tau neutrinos from solar corona interactions; the galactic tau neutrino component) as well as sources of background due to misidentification of electron and muon events. We find that the downward-going tau neutrinos signal has potentially very good prospects for Mton scale Cherenkov detectors, the main limitation being the level of misidentification of non-tau events, which need to be kept at level of percent. Several tens of events per year (depending on the dark matter mass and annihilation/decay channel) are potentially collectible with a Mton scale detector, and a 5 sigma significance discovery is potentially reachable for dark matter masses in the range from 20 to 300 GeV with a few years of exposure on a Mton detector.

Search for a diffuse flux of astrophysical muon neutrinos with the IceCube 40-string detector

The IceCube Neutrino Observatory is a 1 km$^{3}$ detector currently taking data at the South Pole. One of the main strategies used to look for astrophysical neutrinos with IceCube is the search for a diffuse flux of high-energy neutrinos from unresolved sources. A hard energy spectrum of neutrinos from isotropically distributed astrophysical sources could manifest itself as a detectable signal that may be differentiated from the atmospheric neutrino background by spectral measurement. This analysis uses data from the IceCube detector collected in its half completed configuration which operated between April 2008 and May 2009 to search for a diffuse flux of astrophysical muon neutrinos. A total of 12,877 upward going candidate neutrino events have been selected for this analysis. No evidence for a diffuse flux of astrophysical muon neutrinos was found in the data set leading to a 90 percent C.L. upper limit on the normalization of an $E^{-2}$ astrophysical $\nu_{\mu}$ flux of $8.9 \times 10^{-9} \ \mathrm{GeV \ cm^{-2} \ s^{-1} \ sr^{-1}}$. The analysis is sensitive in the energy range between $35 \ \mathrm{TeV} - 7 \ \mathrm{PeV}$. The 12,877 candidate neutrino events are consistent with atmospheric muon neutrinos measured from 332 GeV to 84 TeV and no evidence for a prompt component to the atmospheric neutrino spectrum is found.

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.

Deep Core muon neutrino rate and anisotropy by mixing and CPT violation

Neutrinos are allowed to mix and to oscillate among their flavor. Muon and tau in particular oscillate at largest values. Last Minos experiment claimed MINOS Collaboration [12] possible difference among their matter and anti-matter masses, leading to a first violation of the most believed CPT symmetry. Isotropically born atmospheric muon neutrino at E ν μ ≃ 20 – 80 GeV , while upgoing, they might be partially suppressed by mixing in analogy to historical SuperKamiokande muon neutrino disappearance into tau, leading to large-scale anisotropy signals. Here, we show an independent muon rate foreseen in Deep Core based on observed SK signals extrapolated to Deep Core mass and its surrounding. Our rate prediction partially differ from previous ones. The ν μ , ν ̄ μ disappearance into ν τ , ν ̄ τ is leading to a μ , μ ̄ anisotropy in vertical upgoing muon track: in particular along channel 3–5 we expect a huge rate (nearly ten thousand of events) of neutral current events, charged current electron and inclined crossing muons. Moreover, at channel 6–9 we expect a severe suppression of the rate due to muon disappearance (in CPT conserved frame). A CPT violation may induce a suppression of vertical upgoing tracks because of larger ν ̄ μ reduction for E ν ̄ μ ≥ 35 GeV , corresponding to channel 9–10, and an amplified rate of events between channels 4–5–6.