Down-going Neutrinos Research Articles

Search for Ultra-High-Energy Neutrinos with the Telescope Array Surface Detector

We present an upper limit on the flux of ultra-high-energy down-going neutrinos for $E > 10^{18}\ \mbox{eV}$ derived with the nine years of data collected by the Telescope Array surface detector (05-11-2008 -- 05-10-2017). The method is based on the multivariate analysis technique, so-called Boosted Decision Trees (BDT). Proton-neutrino classifier is built upon 16 observables related to both the properties of the shower front and the lateral distribution function.

Search for cosmic high energy down-going neutrino fluxes from point-like sources with ANTARES

Installed in the Mediterranean Sea, at a depth of ∼ 2.5 km, ANTARES is the largest undersea neutrino telescope currently operating. The search for point-like sources with neutrino telescopes is normally limited to a fraction of the sky, due to the selection of events for which the direction of the neutrino candidate has been reconstructed as coming from below the detector horizon, usually referred to as “up-going” events, in order to significantly reduce the atmospheric muons background. In this contribution we demonstrate that through an energy and direction dependent event selection the background can be effectively suppressed so that a part of the region above the horizon can be included in the search. The strategy for the study of a “down-going” neutrino flux is described and the ANTARES sensitivity is presented. No indication of a neutrino signal has been found in the analysed data and upper limits on the flux normalization of a ∝ Ev-2 energy spectrum of neutrinos from several candidate point-like sources in that region have been set.

LIMIT ON UHE NEUTRINO FLUXES FROM THE PIERRE AUGER OBSERVATORY

The surface detector of the Pierre Auger Observatory is sensitive to Ultra High Energy (UHE) neutrinos. Neutrinos of all flavors can interact in the atmosphere producing inclined showers near the ground. Moreover, ultra high energy Earth-skimming tau neutrinos can be observed through the detection of showers induced by the decay of tau leptons created by interactions in the Earth’s crust. In both cases, neutrino showers can be identified through the time structure of the signals in the surface detector stations. Two sets of identification criteria have been designed to search for down-going and up-going neutrinos in the recorded data, with no candidates found. We will discuss the identification criteria used, and we will present the corresponding limits on the diffuse and point source neutrino fluxes.

Search for ultra-high energy photons and neutrinos using Telescope Array surface detector

We search for ultra-high energy photons by analyzing geometrical properties of shower fronts of events registered by the Telescope Array surface detector. By making use of an event-by-event statistical method, we derive upper limits on the absolute flux of primary photons with energies above 1019 eV, 1019.5 eV and above 1020 eV based on the three years data from Telescope Array surface detector (May 2008 – May 2011). We report the results of down-going neutrino search based on the analysis of very inclined events.

Search for ultra-high energy photons and neutrinos using Telescope Array surface detector

We search for ultra-high energy photons by analyzing geometrical properties of shower fronts of events registered by the Telescope Array surface detector. By making use of an event-by-event statistical method, we derive upper limits on the absolute flux of primary photons with energies above 1019eV, 1019.5eV and above 1020eV based on the three years data from Telescope Array surface detector (May 2008 – May 2011). We report the results of down-going neutrino search based on the analysis of very inclined events.

Publisher’s Note: Search for ultrahigh energy neutrinos in highly inclined events at the Pierre Auger Observatory [Phys. Rev. D84, 122005 (2011)

The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavours above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E^-2 differential energy spectrum the limit on the single flavour neutrino is (E^2 * dN/dE) < 1.74x10^-7 GeV cm^-2 s^-1 sr^-1 at 90% C.L. in the energy range 1x10^17 eV < E < 1x10^20 eV.

Search for ultrahigh energy neutrinos in highly inclined events at the Pierre Auger Observatory

The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavors above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E-2 differential energy spectrum the limit on the single-flavor neutrino is E2dN/dE<1.74×10-7GeVcm -2s-1sr-1 at 90% C.L. in the energy range 1×1017eV<E<1×1020eV. © 2011 American Physical Society.

Limit on the diffuse flux of ultra high energy neutrinos using the Pierre Auger Observatory

The surface array of water-Cherenkov detectors of the Pierre Auger Observatory is sensitive to neutrinos of energies around or above 1 EeV. All flavours interact through charged and neutral current interactions in the atmosphere (down-going), and tau neutrinos may also induce the "earth skimming" mechanism (up-going or crossing mountains). Both types of interaction may produce nearly horizontal atmospheric showers close to the ground, triggering the surface array; they may be distinguished from normal showers thanks to the broad time structure of the signals in the water tanks. Using data collected from january 2004 to february 2009, we use an analysis based on down-going neutrinos to obtain a limit on the all-flavour diffuse neutrino flux. We also update the previous limit for up-going tau neutrinos. Sources of possible backgrounds and systematic uncertainties are discussed.

A GEANT-BASED STUDY OF ATMOSPHERIC NEUTRINO OSCILLATION PARAMETERS AT INO

We have studied the dependence of the allowed space of the atmospheric neutrino oscillation parameters on the time of exposure for a magnetized Iron CALorimeter (ICAL) detector at the India-based Neutrino Observatory (INO). We have performed a Monte Carlo simulation for a 50 kTon ICAL detector generating events by the neutrino generator NUANCE and simulating the detector response by GEANT. A chi-square analysis for the ratio of the up-going and down-going neutrinos as a function of L/E is performed and the allowed regions at 90% and 99% CL are displayed. These results are found to be better than the current experimental results of MINOS and Super-K. The possibilities of further improvement have also been discussed.

Simulation of up- and down-going neutrino induced showers at the site of the Pierre Auger Observatory

We present a study about the possibility to detect neutrino induced extensive air showers at the Pierre Auger Observatory. The Monte Carlo simulations performed take into account the details of the neutrino propagation inside the Earth, the air as well as the surrounding mountains which are modelled by a digital elevation map. Details on the sensitivity with respect to the incoming direction as well as the aperture and the total observable event rates are calculated on the basis of various assumptions of the incoming neutrino flux.

A MC approach to simulate up- and down-going neutrino showers including local topographic conditions

The extragalactic flux of protons is predicted to be suppressed above the famous Greisen–Zatsepin–Kuzmin cut-off at about E GZK ≃ 50 EeV due to the resonant photo-pion production with the cosmic microwave background. Current cosmic ray data do not give a conclusive confirmation of the GZK cut-off and the quest about the origin and the chemical composition of the highest energy cosmic rays is still open. Amongst other particles neutrinos are expected to add to the composition of the cosmic radiation at highest energies. We present an approach to simulate neutrino induced air showers by a full Monte Carlo simulation chain. Starting with neutrinos at the top of the atmosphere, the performed simulations take into account the details of the neutrino propagation inside the Earth and atmosphere as well as inside the surrounding mountains. The products of the interactions are input for air shower simulations. The mountains are modelled by means of a digital elevation map. To exemplify the potential and features of the developed tools we study the possibility to detect neutrino induced extensive air showers with the fluorescence detector set-up of the Pierre Auger Observatory. Both, down-going neutrinos and up-going neutrinos are simulated and their rates are determined. To evaluate the sensitivity, as a function of the incoming direction, the aperture, the acceptance and the total observable event rates are calculated for the Waxman–Bahcall (WB) bound.

Neutrino detection with inclined air showers

The possibilities of detecting high-energy neutrinos through inclined showers produced in the atmosphere are addressed with an emphasis on the detection of air showers by arrays of particle detectors. Rates of inclined showers produced by both down-going neutrino interactions and by up-coming τ decays from Earth-skimming neutrinos as a function of shower energy are calculated with analytical methods using two sample neutrino fluxes with different spectral indices. The relative contributions from different flavours and charged, neutral current and resonant interactions are compared for down-going neutrinos interacting in the atmosphere. No detailed description of detectors is attempted but rough energy thresholds are implemented to establish the ranges of energies which are more suitable for neutrino detection through inclined showers. Down-going and up-coming rates are compared.