### Session C7: Neutrino Astronomy

 Saturday, March 31, 2012 1:30PM - 1:42PM C7.00001: Status update on the HALO experiment Jeffery Secrest The Helium and Lead Observatory (HALO) is currently under construction at the SNOLAB facility outside Sudbury, Canada. HALO will detect neutrinos emitted from Type II supernovae within our galactic neighborhood. The apparatus consists of a total of 384 meters of neutron proportional chambers enclosed by 80 tonnes of lead. Currently the apparatus is being assembled, the Monte Carlo is being developed, and the detector's electronics are being built. The physics and current status of the experiment will be presented. Saturday, March 31, 2012 1:42PM - 1:54PM C7.00002: Sensitivity of the Helium and Lead Observatory to Supernova Neutrino Spectra Kate Scholberg Neutrinos in the few tens-of-MeV range will produce neutrons when interacting with lead via both charged and neutral current interactions. The production of single and double neutron events is highly dependent on neutrino energy. The Helium and Lead Observatory (HALO) is a detector designed to exploit the neutrino-lead interaction in order to measure a burst of neutrinos from a nearby supernova. HALO is under construction at SNOLAB, making use of recycled lead ingots and $^3$He counters from the SNO experiment. The relative rates of single and double neutrons observed for a supernova burst will provide unique information about the spectra of electron flavor as well as muon and tau flavor neutrinos and antineutrinos. Here we present studies of the sensitivity to different supernova models and neutrino oscillation parameters of the 79-tonne HALO1 detector and of a possible future upgrade to 1 kilotonne of lead. Saturday, March 31, 2012 1:54PM - 2:06PM C7.00003: Precision Measurement of the $^{7}$Be Solar Neutrino Flux and its Annual Modulation Szymon Manecki In May 2007, the Borexino experiment opened a new chapter in the low energy solar neutrino world. Its calorimetric detector, of remarkably low levels of radioactive background, relies on the fundamental principle of elastic electron-scattering of all neutrino flavors. In the quest for the Holy Grail of solar physics, the $^{7}$Be line, we have achieved extraordinary precision below 5\%, made possible predominantly due to extensive calibration campaigns. With this sensitivity, we are able to reach levels where effects of the 7\% annual modulation of the signal become detectable. Thus, solving the solar puzzle extends beyond the Sun, it brings new tools in the search for $\nu$ oscillations in the vacuum region. With sufficient statistics, we will be able to establish or exclude almost all values of (sin$^{2}\theta$,$\Delta m^{2}$) preferred by other experiments. At this point, it is the stability control of the detector's backgrounds that plays a critical role, therefore understanding known fluctuations can drastically improve its sensitivity. The detector's performance and calibrations will be presented in the first part of this discussion, while the rest will focus on the $^{7}$Be flux measurements and signal variations with an emphasis on the stability of the backgrounds. Saturday, March 31, 2012 2:06PM - 2:18PM C7.00004: Upper limit on the diffuse flux of UHE neutrinos using the Pierre Auger Observatory Claudia Fracchiolla The Pierre Auger Observatory is the largest ultra-high energy cosmic ray detector. It provides a laboratory for studying fundamental interactions at energies well beyond those available at colliders. In addition to hadrons and photons, the Auger Observatory is also sensitive to ultra-high energy neutrinos. Measuring the flux of cosmogenic neutrinos provides crucial information about the transition point between Galactic and extragalactic cosmic rays. In this talk, I will present the sensitivity of the fluorescence detector of the Auger Observatory to electron neutrinos in the EeV energy range, and the upper limit on the diffuse flux extracted from these data. Saturday, March 31, 2012 2:18PM - 2:30PM C7.00005: The Results of Ice Studies for the ARIANNA Detector from the Antarctic Seasons 2010-11 and 2011-12 Jordan Hanson The Antarctic Ross Ice-Shelf Antenna Neutrino Array is an experiment designed to detect cosmogenic neutrinos with energies in excess of 10$^{17}$ eV, including neutrinos created as by-products of cosmic rays undergoing the GZK effect. ARIANNA is sensitive to down-going neutrinos because the Askaryan radio-frequency pulses they create reflect off of the interface between the ocean and the ice-shelf. We discuss and compare measurements of ice properties performed during two seasons of Antarctic expeditions. We calculate the depth of the ice shelf from timing delays of reflected radio pulses. We also simultaneously solve for the reflectivity of the ice-ocean interface beneath the detector volume and attenuation properties of the ice-shelf itself, using data taken with several instrumentation configurations. Finally, we demonstrate that the reflection surface preserves the polarization of reflected radio signals. Saturday, March 31, 2012 2:30PM - 2:42PM C7.00006: Analysis of Antarctic Surface Reflectivity for Reconstruction of Neutrino and Cosmic Ray Air Shower Events Jessica Stockham The ANITA experiment is designed to detect signals from neutrinos passing through the Antarctic ice sheet. Subsequent to the the ANITA II 2008-2009 flight, analysis showed the detection of cosmic ray air shower events. Events were detected directly and as reflections from the ice surface. The reconstruction of both neutrino and air shower events requires analysis and modeling of the transmission and reflection properties of the air-ice interface. Using data obtained during the ANITA II 2008-2009 flight, reflectivity of the Antarctic ice is analyzed. Direct and reflected solar intensities are compared as a function of frequency to assess specularity in reflection. Expected reflection intensities given by Fresnel coefficients are used to correct the observed intensities for viewing angle. Saturday, March 31, 2012 2:42PM - 2:54PM C7.00007: Radio Frequency Attenuation Length Estimate in Antarctic Ice from Radar Depth Sounding Data Mark Stockham The balloon-borne ANITA experiment in Antarctica seeks detection of in-ice neutrino collisions, which generate radio waves propagating upwards to the suite of 32 horn antennas that constitute ANITA. The primary virtuate of ANITA is the ability to simultaneously observe 20,000 cubic kilometers of ice from its 38-km altitude vantage point. The radio frequency signal strength observed at the balloon, however, depends on the radio frequency attenuation length of the ice through which the neutrino-generated signal must pass. Ice attenuation length varies as a function of surface temperature, depth, bedrock depth, and ice chemistry (imperfections). The CReSIS project has data from several locations on the Antarctic continent gathered from radar depth sounding. An approximation to the attenuation length, as a function of location, in Antarctic ice derived from comparing the bedrock reflection strength at different depths is presented. Saturday, March 31, 2012 2:54PM - 3:06PM C7.00008: Search for Choked GRBs using Icecube's DeepCore Jacob Daughhetee High-energy astrophysical phenomena such as supernovae (SNe) and gamma ray bursts (GRBs) are theorized to result in the production of energetic neutrinos. There is a known correlation between long duration GRBs and core-collapse SNe. A proposed scenario connecting the two involves the production of relativistic jets in a larger fraction of core-collapse SNe rather than just those resulting in GRBs. Whereas in the GRB case these jets break out of the stellar envelope, it is hypothesized that the jets produced in core-collapse SNe often fail to break through their progenitor's envelope and therefore lack a characteristic GRB electromagnetic signature. Such an event is dubbed a choked'' GRB due to the jets having insufficient energy to breach the envelope. These choked GRBs may be detectable, however, through their neutrino emission by IceCube's sub-detector, DeepCore. The combination of the transient nature of choked GRB events, imposed angular constraints, and current filtering algorithms will grant strong background rejection in a search for these events. We will present the expected number of neutrino events from a sample choked GRB at the initial cut level as well as after a selection of a few data cuts aimed at reducing background to manageable levels. Saturday, March 31, 2012 3:06PM - 3:18PM C7.00009: Astrophysical Point Source Searches with the IceCube Neutrino Observatory Naoko Kurahashi The IceCube Neutrino Observatory, designed to discover astrophysical neutrino sources, has just completed construction at the geographical South Pole making it the largest neutrino detector of TeV energies. Data taken during construction are analyzed to search for steady point-like sources, time-dependent neutrino emission correlated with AGN and other flares, as well as correlation with known TeV gamma-ray sources. Recent results of various point source searches will be presented along with outlooks for the completed detector.