Neutrino Astronomy at the South Pole AMANDA and IceCube

Transcription

1 1 Neutrino Astronomy at the South Pole AMANDA and IceCube Ignacio Taboada University of California - Berkeley Topics in Astroparticle and Underground Physics Zaragoza. Sept 10-14, 2005

2 2 The IceCube Collaboration Sweden: USA: Bartol Research Institute University of Alabama Pennsylvania State University University of California Berkeley University of California Irvine Clark-Atlanta University University of Maryland Institute for Advanced Study University of Wisconsin-Madison University of Wisconsin-River Falls Lawrence Berkeley National Lab University of Kansas Southern University and A&M College Uppsala Universitet Stockholm Universitet UK: Imperial College Oxford University Netherlands: Utrecht University Germany: Humboldt Universität Universität Mainz DESY-Zeuthen Universität Dortmund Universität Wuppertal Universität Berlin Belgium: Japan: Chiba University Université Libre de Bruxelles Vrije Universiteit Brussel Universiteit Gent Université de Mons-Hainaut New Zealand: Antarctica: University of Canterbury Amundsen Scott South Pole Station In March 2005, AMANDA merged into the IceCube collaboration

3 3 Neutrino Astronomy Candidate sources: SN remnants, Quasars Active Galactic Nuclei Gamma Ray Bursts Exotics Explained by SN Unexplained Guaranteed sources: Atmospheric neutrinos (from π & K decay) Galactic plane: CR interacting with ISM, concentrated on the disk GZK p γ + n π+ (p π0) Astronomical Messengers: Neutrinos: Neutrinos Not absorbed, not deflected. Small cross section Big Detectors Needed Protons. Protons Deflected by Magnetic fields. Absorbed GZK Photons. Photons Not deflected. Absorbed E> 10 TeV (IR) and E>10 PeV (3K)

4 4 Neutrino Detection in Antarctic Ice O(km) muons ~15 m Θ μν 0.7 E ν /TeV 0.7 Event reconstruction by Cherenkov light timing O(10 m) cascades Average Ice Properties λabs ~ nm λsca ~ nm Most transparent natural solid known

5 5 Amundsen-Scott South Pole Station Ic ec ub e ay yw k S Road to work South Pole Dome AMANDA 1500 m Summer camp 2000 m [not to scale]

6 6 AMANDA 1996 AMANDA-B AMANDA-B AMANDA-II (first 4-string prototype) (inner core of AMANDA-II) 4 strings 80 OMs 10 strings 302 OMs 19 strings 677 OMs Data years: 1996 Data years: Data years: 2000 What s up? Up-going Down-going (from Northern sky) (from Southern sky) Optical Module PMT noise: ~1 khz WWe use the Earth as a filter for e down-going atmospheric muons

7 7 AMANDA Physics Topics Results shown in this talk: Atmospheric neutrinos Searches for extra-terrestrial fluxes Neutrino Diffuse fluxes Neutrino Point sources Neutrinos from the galactic plane Neutrinos from GRBs SNe in the Milky Way Other results: Searches for WIMPs: Sun/Earth center Atmospheric muon spectrum Cosmic Ray composition Search for magnetic monopoles Many others... Agreed collaboration strategy: Blind Analyses

8 8 Atmospheric Neutrinos Atmospheric neutrinos: - Guaranteed test beam - Background for other searches Neural Network energy reconstruction of up-going µ's Regularized unfolding ν energy spectrum Set limit on cosmic neutrino flux: How much E-2 cosmic ν - signal allowed within uncertainty of highest energy bins? Limit on diffuse E-2 νμ flux ( TeV): E2Φνμ(E) < GeV cm-2 s-1 sr-1

9 9 Diffuse fluxes νµ Search All flavor search All flavor search HE: TeV < Eν < PeV UHE: Eν > P ev HE: TeV < Eν < PeV Use directionality + energy-related variables to reject atm µ background Earth opaque 4π search search Search confined to upgoing tracks Use high-quality tracks Limits from 1997 and Limits Search in the upper hemisphere and close to the horizon Bright events: many hit OMs with several hits/om Energy-related variables best handle of analysis Limit from Sensitivity from Limits on νµ Background: brem. from down-going muons Limits from 1997, 1999 Limits and 2000 Signal Background Limits that assume νe:νµ:ντ :: 1:1:1

10 10 Diffuse fluxes: Summary

11 11 Neutrino Point Sources Search for excesses of events compared to the background from: The Northern sky A set of selected candidate sources Require good pointing resolution (good quality events) Background estimated from exp. data with randomized α (i.e. time) Sensitivity ~ flat up to horizon average flux upper limit [cm-2s-1] Cuts optimized by declination bands Average upper limit = sensitivity (δ>0 ) (integrated above 10 GeV, E-2 signal) AMANDA-B10 AMANDA-II Significant improvement w.r.t. first analysis with AMANDA-B10 At the south pole: δ declination δ=0o (horizontal) δ=90o (vertical) sin(δ) Declination averaged sensitivity for a Eν-2 spectrum and Eν > 10 GeV Φνlim ~ cm-2s-1

12 12 Neutrino Point Sources Event selection optimized for both E-2 & E-3 spectra Data from (807 days) 3369 ν from northern hemisphere 3438 ν expected from atmosphere Maximum significance: 3.4 σ Probability of a background fluctuation: 92 %

13 13 Neutrino Point Sources Selected objects and full scan of the northern sky: On-Source No statistically significant effect observed Off-Source Sensitivity Φν/Φγ~2 for 200 days of high-state and spectral results from HEGRA Crab Nebula: The chance probability of such an excess (or higher) given the number of trials is 64% Source Expected # of ν bckg events (4 years) (4 years) Flux Upper Limit Φ90%(Eν>10 GeV) [10-8cm-2s-1] Markarian ES SS Cygnus X Cygnus X Crab Nebula out of 33 Sources ry a in m eli Pr Systematic uncertainties under investigation We have also performed a time-dependent search for specific sources. No evidence of sources found.

14 14 Neutrinos from the Galactic Plane Location of AMANDA not optimal reach only outer region of the galactic plane: 33o < δ < 213o Three signal ansatz: Line source, Gaussian source, Diffuse source Limits include systematic uncertainty of 30% on atm. ν flux Energy range: 0.2 to 40 TeV - Gaus. limit Model On-source On-source Expected region events bckg. 2o o Limit 6.4x10-5 (line) GeV-1cm-2s-1rad-1 6.6x10-4 (diffuse) GeV-1cm-2s-1sr-1 4.8x10-4 (gauss) GeV-1cm-2s-1sr-1

15 15 Neutrinos from GRBs Low background analysis due to time and directional coincidence Off-Time Always Blind Precursor On Time 110 s T90 Several search techniques: Muons Coincident with T90 Precursor Cascades Coincident with T90 Rolling time window Bckg Measurement & Stability ±1 hour from burst A search for νµ in coincidence with GRB has also been made 10 min 1 hour 1 hour time Preliminary 90%CL limit / sensitivity assuming WB spectrum # GRB from '97 - ' BATSE triggered bursts E2dΦν/dE = GeV cm-2s-1 sr-1 '00 - ' BATSE & IPN bursts E2dΦν/dE = GeV cm-2 s-1 sr-1 '01 - '03 50 IPN bursts '01 (425) Rolling window E2dΦν/dE = GeV cm-2s-1sr-1 73 BATSE triggered bursts E2dΦν/dE = GeV cm-2s-1sr-1 year '00 (EB at 100 TeV and Γ = 300) (Assuming Razzaque et. al. model) E2dΦν/dE = GeV cm-2 s-1 sr-1

16 16 Burst of low-energy (MeV) neutrinos from core-collapse supernovae Global PMT noise rate increase due to νe + p e+ + n Low energy O(MeV) track: no pointing Monitor stable subset of Optical Modules Supernovae Crab Nebula Sun Cassiopeia. A LMC Cygnus-X1 SMC Approximate AMANDA horizon Special DAQ 92% (mass) coverage of the Galaxy light years AMANDA part of SNEWS alert network

17 17 IceCube Observatory IceTop: air shower array 50 m Firn 80 Stations / 2 Tanks each 2 DOMs per tank 125 m grid, 1 km2 at 690 g/cm2 Ethres ~ 300 TeV for 4 stations Useful rate up to ~EeV Ice 145 0m AMANDA Digital Optical Module 324 m 245 0m PMT Noise 700 Hz IceCube: deep ice array 80 Strings / 60 DOMs each 17 m DOM spacing 125 m between strings 1 km3 instrumented

18 18 IceCube Status An IceTop Station: Two tanks 1 In-Ice String with 60 DOMs deployed 4 IceTop Stations / 8 Tanks / 16 DOMs An In-Ice DOM being lowered into the ice

19 19 An IceCube-IceTop Event 4 IceTop Stations AMANDA Deployed String

20 20 IceCube Outlook Season 2005/2006: Up to 12 new strings to be deployed Up to 16 new stations to be deployed Instrumented volume would be ~10 times larger than that of AMANDA-II Detector to finish construcion by 2009/2010

21 21 Summary Many results from AMANDA-B10 and AMANDA-II on multiple physics topics Results from combined analyses No evidence for extraterrestrial neutrinos yet First IceCube string and 4 IceTop stations deployed and taking data IceCube will significantly improve astrophysics and cosmic ray measurements