arXiv:astro­ph/0409423 v1 17 Sep 2004
    1
    New results from the Antarctic Muon And Neutrino Detector Array
    K. Woschnagg for the AMANDA Collaboration:
    M. Ackermann
    a
    , J. Ahrens
    b
    , H. Albrecht
    a
    , D. W. Atlee
    c
    , X. Bai
    d
    , R. Bay
    e
    , M. Bartelt
    f
    ,
    S. W. Barwick
    g
    , T. Becka
    b
    , K.­H. Becker
    f
    , J. K. Becker
    f
    , E. Bernardini
    a
    , D. Bertrand
    h
    ,
    D. J. Boersma
    a
    , S. B¨oser
    a
    , O. Botner
    i
    , A. Bouchta
    i
    , O. Bouhali
    h
    , J. Braun
    j
    , C. Burgess
    k
    , T. Burgess
    k
    ,
    T. Castermans
    l
    , D. Chirkin
    m
    , J. A. Coarasa
    c
    , B. Collin
    c
    , J. Conrad
    i
    , J. Cooley
    j
    , D. F. Cowen
    c
    ,
    A. Davour
    i
    , C. De Clercq
    n
    , T. DeYoung
    o
    , P. Desiati
    j
    , P. Ekstr¨om
    k
    , T. Feser
    b
    , T. K. Gaisser
    d
    ,
    R. Ganugapati
    j
    , H. Geenen
    f
    , L. Gerhardt
    g
    , A. Goldschmidt
    m
    , A. Groß
    f
    , A. Hallgren
    i
    , F. Halzen
    j
    ,
    K. Hanson
    j
    , D. Hardtke
    e
    , R. Hardtke
    j
    , T. Harenberg
    f
    , T. Hauschildt
    a
    , K. Helbing
    m
    , M. Hellwig
    b
    ,
    P. Herquet
    l
    , G. C. Hill
    j
    , J. Hodges
    j
    , D. Hubert
    n
    , B. Hughey
    j
    , P. O. Hulth
    k
    , K. Hultqvist
    k
    ,
    S. Hundertmark
    k
    , J. Jacobsen
    m
    , K.­H. Kampert
    f
    , A. Karle
    j
    , J. Kelley
    j
    , M. Kestel
    c
    , L. K¨opke
    b
    ,
    M. Kowalski
    a
    , M. Krasberg
    j
    , K. Kuehn
    g
    , H. Leich
    a
    , M. Leuthold
    a
    , J. Lundberg
    i
    , J. Madsen
    p
    ,
    K. Mandli
    j
    , P. Marciniewski
    i
    , H. S. Matis
    m
    , C. P. McParland
    m
    , T. Messarius
    f
    , Y. Minaeva
    k
    ,
    P. Mioˇcinovi´c
    e
    , R. Morse
    j
    , K. M¨unich
    f
    , R. Nahnhauer
    a
    , J. W. Nam
    g
    , T. Neunh¨offer
    b
    , P. Niessen
    d
    ,
    D. R. Nygren
    m
    , H.
    ¨
    Ogelman
    j
    , Ph. Olbrechts
    n
    , C. P´erez de los Heros
    i
    , A. C. Pohl
    q
    , R. Porrata
    e
    ,
    P. B. Price
    e
    , G. T. Przybylski
    m
    , K. Rawlins
    j
    , E. Resconi
    a
    , W. Rhode
    f
    , M. Ribordy
    l
    , S. Richter
    j
    ,
    J. Rodr
    ´
    iguez Martino
    k
    , H.­G. Sander
    b
    , K. Schinarakis
    f
    , S. Schlenstedt
    a
    , D. Schneider
    j
    , R. Schwarz
    j
    ,
    S. H. Seo
    c
    , A. Silvestri
    g
    , M. Solarz
    e
    , G. M. Spiczak
    p
    , C. Spiering
    a
    , M. Stamatikos
    j
    , D. Steele
    j
    ,
    P. Steffen
    a
    , R. G. Stokstad
    m
    , K.­H. Sulanke
    a
    , I. Taboada
    r
    , O. Tarasova
    a
    , L. Thollander
    k
    , S. Tilav
    d
    ,
    J. Vandenbroucke
    e
    , L. C. Voicu
    c
    , W. Wagner
    f
    , C. Walck
    k
    , M. Walter
    a
    , Y. R. Wang
    j
    , C. H. Wiebusch
    f
    ,
    R. Wischnewski
    a
    , H. Wissing
    a
    , K. Woschnagg
    e
    , G. Yodh
    g
    a
    DESY­Zeuthen, 15735 Zeuthen, Germany
    b
    Institute of Physics, University of Mainz, D­55099 Mainz, Germany
    c
    Dept. of Physics, Pennsylvania State University, University Park, PA 16802, USA
    d
    Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
    e
    Dept. of Physics, University of California, Berkeley, CA 94720, USA
    f
    Dept. of Physics, Bergische Universit¨at Wuppertal, D­42097 Wuppertal, Germany
    g
    Dept. of Physics and Astronomy, University of California, Irvine, CA 92697, USA
    h
    Universit´e Libre de Bruxelles, Science Faculty CP230, B­1050 Brussels, Belgium
    i
    Division of High Energy Physics, Uppsala University, S­75121 Uppsala, Sweden
    j
    Dept. of Physics, University of Wisconsin, Madison, WI 53706, USA
    k
    Dept. of Physics, Stockholm University, S­10691 Stockholm, Sweden
    l
    University of Mons­Hainaut, 7000 Mons, Belgium
    m
    Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
    n
    Vrije Universiteit Brussel, Dienst ELEM, B­1050 Brussels, Belgium
    o
    Dept. of Physics, University of Maryland, College Park, MD 20742, USA
    p
    Physics Dept., University of Wisconsin, River Falls, WI 54022, USA
    q
    Dept. of Technology, Kalmar University, S­39182 Kalmar, Sweden
    r
    Dept. of Physics, Universidad Sim´on Bol´ıvar, Caracas, 1080, Venezuela
    We present recent results from the Antarctic Muon And Neutrino Detector Array (AMANDA) on searches for
    high­energy neutrinos of extraterrestrial origin. We have searched for a diffuse flux of neutrinos, neutrino point
    sources and neutrinos from GRBs and from WIMP annihilations in the Sun or the center of the Earth. We also
    present a preliminary result on the first energy spectrum above a few TeV for atmospheric neutrinos.
    1. INTRODUCTION
    The existence of high­energy cosmic neutrinos
    is suggested by the observation of high­energy
    cosmic rays and gamma rays. Observation of
    cosmic neutrinos could shed light on the produc­
    tion and acceleration mechanisms of cosmic rays,
    which are not understood for energies above the
    “knee” at 10
    15
    eV. Neutrinos with energies in the
    TeV range and higher may be produced by a va­
    riety of sources. Candidate cosmic accelerators
    include supernova remnants, the accretion disk
    and jets of Active Galactic Nuclei (AGN), and
    the violent processes behind Gamma Ray Bursts
    (GRB). In these environments, neutrinos are ex­
    pected to be produced in the decays of pions cre­
    ated through proton­proton or proton­photon col­
    lisions. The AMANDA detector was built to ex­
    plore the high­energy universe in neutrinos, using
    the advantages of neutrinos as cosmic messengers.
    In January 2005, construction will begin on Ice­
    Cube [1], the km
    3
    ­sized successor to AMANDA.
    2. THE AMANDA DETECTOR
    The AMANDA detector
    1
    [2] consists of 677 op­
    tical modules arranged along 19 vertical strings
    buried deep in the glacial ice at the South Pole,
    mainly at depths between 1500 and 2000 m. Each
    module consists of a photomultiplier tube (PMT)
    housed in a spherical glass pressure vessel. PMT
    pulses are transmitted to the data acquisition
    electronics at the surface via coaxial cables (in­
    ner 4 strings), twisted pair cables (6 strings) or
    optical fibers (outer 9 strings). The geometric
    outline of the array is a cylinder which is 500 m
    high and with a radius of 100 m. The typical ver­
    tical spacing between modules is 10–20 m, and
    the horizontal spacing between strings 30–50 m.
    The optical modules record Cherenkov light
    generated by secondary charged leptons (e,
    µ
    ,
    τ
    )
    created in neutrino interactions near the detec­
    tor. Events are reconstructed by maximizing the
    likelihood that the timing pattern of the recorded
    light is produced by a hypothetical track or cas­
    1
    The full 19­string array, named AMANDA­II, started
    taking data in 2000. An earlier 10­string stage (comprising
    the inner 10 strings), called AMANDA­B10, was taking
    data in the period 1997–1999.
    cade [3]. The angular resolution is between 1.5
    ◦
    and 2.5
    ◦
    for muon tracks, depending on declina­
    tion, and
    ∼
    30
    ◦
    for cascades, the difference re­
    flecting the fact that muon tracks yield a long
    lever arm whereas cascades produce more spher­
    ical light patterns. On the other hand, the en­
    ergy resolution, which is correlated to the amount
    of detected light, is better for cascades, 0.15 in
    log(
    E
    ), than for muon tracks, 0.4 in log(
    E
    ).
    Using calibration light sources deployed with
    the strings and a YAG laser at the surface con­
    nected to diffusive balls in the ice via optical
    fibers, we have mapped [4] the optical proper­
    ties of the ice over the full relevant wavelength­
    and depth range (figure 1). The glacial ice is ex­
    tremely transparent for Cherenkov wavelengths
    near the peak sensitivity of the modules: at 400
    nm, the average absorption length is 110 m and
    the average effective scattering length is 20 m.
    Below a depth of 1500 m, both scattering and
    absorption are dominated by dust, and the opti­
    cal properties vary with dust concentration. The
    depth profile is in good agreement with variations
    of dust concentration measured in ice cores from
    other Antarctic sites [5,6,7]. These dust layers
    reflect past variations in climate. Implementa­
    tion of the detailed knowledge of ice properties
    into our detector simulation and reconstruction
    tools reduces systematic uncertainties and im­
    proves track and cascade reconstruction.
    In the 2003/04 field season, the data acquisition
    system was upgraded with Transient Waveform
    Recorders on all channels, digitizing the PMT
    pulses in the electronics on the surface. Wave­
    form digitization will increase the effective dy­
    namic range of individual channels by about a
    factor 100 and will lead to an improvement in en­
    ergy reconstruction, especially at high energies.
    3. PHYSICS TOPICS AND ANALYSIS
    STRATEGIES
    AMANDA is used to explore a variety of
    physics topics, ranging from astrophysics to par­
    ticle physics, over a wide range of energies. At the
    lower energy end, in the MeV range, AMANDA
    is sensitive to fluxes of antineutrinos from super­
    novae. For higher energies, GeV to TeV, the de­
    2
    3
    Figure 1. Optical properties of deep South Pole
    ice: absorptivity (top) and scattering coefficient
    (bottom) as function of depth and wavelength.
    The green (partially obscured) tilted planes show
    the contribution from pure ice to absorption and
    from air bubbles to scattering, respectively. If
    these contributions are subtracted, the optical
    properties vary with the concentration of insol­
    uble dust, which tracks climatological variations
    in the past [5,6,7].
    tector is used to study atmospheric neutrinos and
    to conduct indirect dark matter searches. In the
    energy range for which AMANDA has been pri­
    marily optimized, TeV to PeV, the aim is to use
    neutrinos to study AGN and GRBs, looking both
    for a diffuse flux and for point sources of high­
    energy neutrinos. Using special analysis tech­
    niques, the array is also sensitive to the ultra­high
    energies in the PeV to EeV range.
    For most analysis channels, AMANDA uses the
    Earth as a filter and looks down for up­going
    neutrinos. The main classes of background are
    up­going atmospheric neutrinos and down­going
    atmospheric muons that are misreconstructed as
    up­going. Since AMANDA is located at the
    South Pole, an up­going event will have origi­
    nated in the Northern sky.
    We present all flux limits following the ordering
    scheme in [8] and include systematic uncertainties
    in the limit calculations according to the method
    derived in [9]. The main sources of systematic
    uncertainty in the analyses presented here are the
    modelling of muon propagation and of optical ice
    properties in the detector simulation, adding up
    to roughly 25% uncertainty.
    The AMANDA collaboration adheres strictly
    to a policy of performing all analyses in a “blind”
    manner to ensure statistical purity of the results.
    In practice, this means that selection criteria are
    optimized either on a sub­sample of the data set
    which is then excluded from the analysis yield­
    ing the final result, or on a time­scrambled data
    set which is only unscrambled after the selection
    criteria have been optimized and finalized.
    4. ATMOSPHERIC NEUTRINOS
    Neutrinos, and to some extent muons, created
    by cosmic ray interactions in the atmosphere con­
    stitute the main background in most analysis
    channels, but also serve as a test beam. Using
    a neural net energy reconstruction, trained on
    a full detector and physics simulation, followed
    by regularized unfolding, we measure a prelimi­
    nary energy spectrum for up­going neutrinos with
    AMANDA­II data from 2000 (figure 2). This is
    the first atmospheric neutrino spectrum above a
    few TeV, and it extends up to 300 TeV.
    4
    Figure 2. Atmospheric neutrino energy spec­
    trum (preliminary) from regularized unfolding of
    AMANDA data, compared to the Frejus spec­
    trum [10] at lower energies. The two solid curves
    indicate model predictions [11] for the horizontal
    (upper) and vertical (lower) flux.
    5. SEARCHES FOR A DIFFUSE FLUX
    OF COSMIC NEUTRINOS
    The ultimate goal of AMANDA is to find and
    study the properties of cosmic sources of high­
    energy neutrinos. Should individual sources be
    too weak to produce an unambiguous directional
    signal in the array, the integrated neutrino flux
    from all sources could still produce a detectable
    diffuse signal. We have searched several years of
    data for such a diffuse signal using complemen­
    tary techniques in different energy regimes.
    5.1. Atmospheric neutrino spectrum
    The atmospheric neutrino spectrum (fig. 2) was
    used to set an upper limit on a diffuse
    E
    2
    flux
    of extraterrestrial muon neutrinos for the energy
    range covered by the highest bin, 100–300 TeV, by
    calculating the maximal non­atmospheric contri­
    bution to the flux in the bin given its statistical
    uncertainty. However, the bins in the unfolded
    spectrum are correlated and the uncertainty in
    the last bin can not a priori be assumed to be
    Poissonian. The statistics in the bin were there­
    fore determined with a Monte Carlo technique
    used to construct confidence belts following the
    definition by Feldman and Cousins [8]. Given the
    unfolded number of experimental events in the
    bin (a fractional number), a preliminary 90% C.L.
    upper limit of
    E
    2
    Φ
    ν
    µ
    (
    E
    )
    <
    2
    .
    6
    ×
    10
    7
    GeV cm
    2
    s
    1
    sr
    1
    (1)
    was derived for 100 TeV
    < E
    ν
    <
    300 TeV, which
    includes 33% systematic uncertainties.
    5.2. Cascades
    In the cascade channel, AMANDA has essen­
    tially 4
    π
    coverage, and is sensitive to all three
    neutrino flavors. The 2000 data sample, corre­
    sponding to 197 days livetime, was searched for
    cascade events. Event selection was based on
    topology and energy, and optimized to maximize
    the sensitivity to an
    E
    2
    signal spectrum. After
    final cuts one event remains, with an expected
    background of 0
    .
    90
    +0
    .
    69
    0
    .
    43
    from atmospheric muons
    and 0
    .
    06
    +0
    .
    09
    0
    .
    04
    from atmospheric neutrinos. Not
    having observed an excess over background, we
    calculate a limit on a signal flux. The 90% C.L.
    limit on a diffuse flux of neutrinos of all flavors
    for neutrino energies between 50 TeV and 5 PeV,
    assuming full flavor mixing so that the neutrino
    flavor ratios are 1:1:1 at the detector, is
    E
    2
    Φ
    ν
    (
    E
    )
    <
    8
    .
    6
    ×
    10
    7
    GeV cm
    2
    s
    1
    sr
    1
    .
    (2)
    Since the energy range for this analysis contains
    the energy of the Glashow resonance (6.3 PeV)
    the above limit translates to
    E
    2
    Φ
    ¯
    ν
    e
    (6
    .
    3 PeV)
    <
    2
    ×
    10
    6
    GeV cm
    2
    s
    1
    sr
    1
    .
    (3)
    These limits [12] obtained with one year (2000) of
    AMANDA­II data are roughly a factor 10 lower
    than the limits from similar searches performed
    with AMANDA­B10 data from 1997 [13] and 1999
    [12].
    5.3. Ultra High Energy neutrinos
    At ultra­high energies (UHE), above 1 PeV, the
    Earth is opaque to electron­ and muon­neutrinos.
    5
    Tau neutrinos with such initial energies might
    penetrate the Earth through regeneration [14],
    in which the
    τ
    produced in a charged­current
    ν
    τ
    interaction decays back into
    ν
    τ
    , but they will
    emerge with much lower energies. The search for
    extraterrestrial UHE neutrinos is therefore con­
    centrated on events close to the horizon and even
    from above. The latter is possible since the at­
    mospheric muon background is low at these high
    energies due to the steeply falling spectrum. Our
    search for UHE events in 1997 AMANDA­B10
    data (131 days of livetime) relies on parameters
    that are sensitive to the expected characteristics
    of an UHE signal: bright events, long tracks (for
    muons), low fraction of single photoelectron hits.
    A neural net was trained to optimize the sensitiv­
    ity to an
    E
    2
    neutrino signal in data dominated
    by atmospheric neutrino background.
    After final selection, 5 data events remain, with
    4
    .
    6 (
    ±
    36%) expected background. Thus, no ex­
    cess above background is observed and we derive
    [15] a 90% C.L. limit on an
    E
    2
    flux of neutri­
    nos of all flavors, assuming a 1:1:1 flavor ratio at
    Earth, for energies between 1 PeV and 3 EeV, of
    E
    2
    Φ
    ν
    (
    E
    )
    <
    0
    .
    99
    ×
    10
    6
    GeV cm
    2
    s
    1
    sr
    1
    .
    (4)
    A similar analysis of AMANDA­II data from 2000
    is under way. However, the bright UHE events
    also saturate the larger array, so a substantial
    gain in sensitivity will mainly be due to the ad­
    ditional exposure time and improved selection al­
    gorithms.
    5.4. Summary of diffuse searches
    Using different analysis techniques, AMANDA
    has set limits on the diffuse flux of neutrinos with
    extraterrestrial origin for neutrino energies from
    6 TeV [16] up to a few EeV. With the exception
    of the limit from the unfolded atmospheric spec­
    trum, which can be seen as a quasi­differential
    limit, the limits are on the integrated flux over
    the energy range which contains 90% of the sig­
    nal. Our limits exclude, at 90% C.L., some mod­
    els [17,18] predicting diffuse neutrino fluxes.
    6. POINT SOURCE SEARCHES
    Searches for neutrino point sources require
    good pointing resolution and are thus restricted
    to the
    ν
    µ
    channel. We have searched AMANDA­
    II data from 2000–2003 (807 days livetime) for
    a point source signal. Events were selected to
    maximize the model rejection potential [19] for
    an
    E
    2
    neutrino spectrum convoluted with the
    background spectra due to atmospheric neutrinos
    and misreconstructed atmospheric muons. The
    selection criteria were optimized for the combined
    4­year data set in each declination band sepa­
    rately, since the geometry of the detector array in­
    troduces declination­dependent efficiencies. The
    sensitivity
    of the analysis, defined as the average
    upper limit one would expect to set on a non­
    atmospheric neutrino flux if no signal is detected,
    is shown in figure 3 for a hypothetical
    E
    2
    signal
    spectrum.
    )
    δ
    sin(
    0 0.2 0.4 0.6 0.8 1
    ­2
    cm
    ­1
    Gev s
    ­6
    dN/dE / 10
    2
    E
    0.05
    0.1
    0.15
    0.2
    0.25
    0.3
    )
    δ
    sin(
    0 0.2 0.4 0.6 0.8 1
    ­2
    cm
    ­1
    Gev s
    ­6
    dN/dE / 10
    2
    E
    0.05
    0.1
    0.15
    0.2
    0.25
    0.3
    Time period
    2000
    2001
    2002
    2003
    2000­2003
    Figure 3. AMANDA­II sensitivity for an
    E
    2
    flux
    spectrum as function of declination.
    The final sample of 3369 neutrino candidates
    (with 3438 expected atmospheric neutrinos) was
    searched for point sources with two methods.
    In the first, the sky is divided into a (repeat­
    edly shifted) fine­meshed grid of overlapping bins
    which are tested for a statistically significant
    excess over the background expectation (esti­
    mated from all other bins in the same declination
    band). This search yielded no evidence for extra­
    6
    terrestrial point sources. The second method is
    an unbinned search, in which the sky locations
    of the events and their uncertainties from recon­
    struction are used to construct a sky map of sig­
    nificance in terms of fluctuation (in
    σ
    ) over back­
    ground (figure 4). This map displays only one po­
    tential hot spot (above 3
    σ
    ), which is well within
    the expectation from a random event distribu­
    tion. For comparison, the same significance map
    was constructed after randomizing the right as­
    cension for all events, thus simulating a truly
    random distribution (lower panel in the figure).
    This scrambled map is statistically indistinguish­
    able from the real (upper) map. A full statisti­
    cal analysis of many such scrambled maps proves
    that the sky map is fully compatible with a dis­
    tribution expected from an atmospheric neutrino
    sample. We thus see no evidence for point sources
    with an
    E
    2
    energy spectrum based on the first
    four years of AMANDA­II data. This preliminary
    result complements previously published results
    from point source searches with the AMANDA­
    B10 detector [20] and the first year of AMANDA­
    II data [21].
    7. SEARCH FOR NEUTRINOS FROM
    GRBs
    A special case of point source analysis is the
    search for neutrinos coincident with gamma ray
    bursts (GRBs) detected by satellite­borne detec­
    tors. For this search, the timing of the neu­
    trino event serves as an additional selection han­
    dle which significantly reduces background.
    We have used the GRB sample collected by the
    BATSE instrument on board the CGRO satellite.
    The AMANDA and BATSE data taking periods
    were overlapping between 1997, when AMANDA­
    B10 became operational, and 2000, when CGRO
    was decommissioned. In total, we have ana­
    lyzed a sample containing 312 bursts triggered
    by BATSE from this period. For each of these
    bursts, AMANDA data was searched for an ex­
    cess over background of events in a 10 min win­
    dow around the GRB time (here defined as the
    start of
    T
    90
    ). The background was estimated by
    averaging over events in the on­source spatial bin
    within
    ±
    1 hour of the burst (excluding the 10 min
    Reconstructed sky coordinates
    Scrambled in right ascension
    Figure 4. Significance map (top) constructed
    from 3369 events in the final sample from a point
    source search with AMANDA­II data from 2000–
    2003. The points show the reconstructed sky po­
    sitions (declination and right ascension) of the
    neutrino candidates. The color scale indicates the
    significance (in
    σ
    ). The lower panel shows an ex­
    ample of a significance map based on the same
    events, but with randomized right ascension co­
    ordinates.
    signal window).
    No neutrino event was observed in coincidence
    with any of the bursts. Assuming a broken power­
    law energy spectrum as proposed by Waxmann
    and Bahcall [22], with
    E
    break
    = 100 TeV and
    bulk
    = 300, we obtain a 90% C.L. upper limit
    on the expected neutrino flux at the Earth of
    E
    2
    Φ
    ν
    (
    E
    )
    <
    4
    ×
    10
    8
    GeV cm
    2
    s
    1
    sr
    1
    .
    (5)
    This is approximately a factor 15 above the
    Waxmann­Bahcall flux prediction.
    Work is under way to include other classes of
    bursts in the analysis. A class of bursts that did
    not trigger the BATSE detector but were found
    by a later off­line analysis of archived data [23]
    7
    comprises 26 events in the Northern sky during
    the up­time of AMANDA in 2000. Since 2000, the
    only source of GRB detection is the Third Inter­
    planetary Network (IPN3), a group of spacecraft
    equipped with gamma­ray burst detectors which
    uses triangulation to spatially locate the bursts.
    IPN­triggered bursts will also be included in fu­
    ture GRB­neutrino searches with AMANDA.
    8. DARK MATTER SEARCHES
    Particle physics provides an interesting candi­
    date for non­baryonic dark matter in the Weakly
    Interacting Massive Particle (WIMP). In particu­
    lar, the Minimal Supersymmetric extension of the
    Standard Model (MSSM) provides a promising
    WIMP candidate in the neutralino, which could
    be the lightest supersymmetric particle. Neu­
    tralinos can be gravitationally trapped in mas­
    sive bodies, and can then via annihilations and
    the decay of the resulting particles produce neu­
    trinos. AMANDA can therefore perform indirect
    dark matter searches by looking for fluxes of neu­
    trinos from the center of the Earth or the Sun.
    For the former, we present a preliminary up­
    date to our published limits obtained with one
    year of 10­string data [25]. We have looked for
    vertically up­going tracks in AMANDA­B10 data
    from 1997 to 1999, corresponding to a total live­
    time of 422 days. No WIMP signal was found
    and a 90% C.L. upper limit on the muon flux
    from the center of the Earth was set for neutralino
    masses between 50 GeV and 5 TeV (figure 5, up­
    per panel).
    Due to its larger mass (resulting in a deeper
    gravitational well) and a higher capture rate due
    to additional spin­dependent processes, the Sun
    can also be used for WIMP searches despite its
    much larger distance from the detector. Although
    the Sun is maximally 23
    ◦
    below the horizon at
    the South Pole, AMANDA­II can be used for
    a WIMP search thanks to its improved recon­
    struction capabilities for horizontal tracks. Anal­
    ysis of 2001 data (0.39 years of livetime) yielded
    no WIMP signal. The preliminary upper limit
    on the muon flux from the Sun is compared to
    MSSM predictions [26] in figure 5 (lower panel).
    For heavier neutralino masses, the limit obtained
    10
    ­2
    10
    ­1
    1
    10
    10
    2
    10
    3
    10
    4
    10
    5
    10
    10
    2
    10
    3
    10
    4
    σ
    SI
     
    >
     
    σ
    SI
    lim
    σ
    SI
     
    <
     
    σ
    SI
    lim
    J. Lundberg and J. Edsjö, 2004
    E
    μ
     
    >
    1 GeV
    0.05
    <
     
    Ω
    χ
    h
    2
     
    <
    0.2
    New solar system diffusion
    Neutralino Mass (GeV/c
    2
    )
    φ
    μ
    ( km
    ­2
    yr
    ­1
    )
    AMANDA 97­99 data
    BAKSAN 1997
    MACRO 2002
    SUPER­K 2004
    1
    10
    10
    2
    10
    3
    10
    4
    10
    5
    10
    6
    10
    10
    2
    10
    3
    10
    4
    σ
    SI
     
    >
     
    σ
    SI
    lim
    σ
    SI
    lim
      
    >
     
    σ
    SI
     
    >
    0.1
    σ
    SI
    lim
    0.1
    σ
    SI
    lim
      
    >
     
    σ
    SI
    J. Edsjö, 2004
    E
    th
    μ
    = 1 GeV
    σ
    SI
    lim
    = CDMS 2004
    0.05
    <
     
    Ω
    χ
    h
    2
     
    <
    0.2
    Neutralino Mass (GeV)
    Muon flux from the Sun (km
    ­2
    yr
    ­1
    )
    BAKSAN 1997
    MACRO 2002
    SUPER­K 2004
    IceCube Best­Case
    AMANDA­II, 2001
    Figure 5. Preliminary limits on the muon flux due
    to neutrinos from neutralino annihilations in the
    center of the Earth (top) and the Sun (bottom).
    The colored symbols correspond to model predic­
    tions [26] within the allowed parameter space of
    the MSSM. The green models are disfavored by
    direct searches with CDMS II [24].
    8
    with less than one year of AMANDA­II data
    is already competitive with limits from indirect
    searches with detectors that have several years of
    integrated livetime. The green points in figure 5
    correspond to models that are disfavored by di­
    rect searches [24], which appear to set more severe
    restrictions on the allowed parameter space than
    indirect searches. However, it should be noted
    that the two methods are complementary in that
    they (a) probe the WIMP distribution in the solar
    system at different epochs and (b) are sensitive to
    different parts of the velocity distribution.
    9. SUPERNOVA DETECTION
    Since 2003 the AMANDA supernova system
    includes all AMANDA­II channels. Recent up­
    grades of the online analysis software have im­
    proved the supernova detection capabilities such
    that AMANDA­II can detect 90% of supernovae
    within 9.4 kpc with less than 15 fakes per year.
    This is sufficiently robust for AMANDA to now
    contribute to the SuperNova Early Warning Sys­
    tem (SNEWS) with neutrino detectors in the
    Northern hemisphere.
    ACKNOWLEDGEMENTS
    We acknowledge the support of the following agen­
    cies: National Science Foundation – Office of Po­
    lar Programs, National Science Foundation – Physics
    Division, University of Wisconsin Alumni Research
    Foundation, Department of Energy and National
    Energy Research Scientific Computing Center (sup­
    ported by the Office of Energy Research of the
    Department of Energy), UC­Irvine ANEAS Super­
    computer Facility, USA; Swedish Research Coun­
    cil, Swedish Polar Research Secretariat and Knut
    and Alice Wallenberg Foundation, Sweden; Ger­
    man Ministry for Education and Research, Deutsche
    Forschungsgemeinschaft (DFG), Germany; Fund for
    Scientific Research (FNRS­FWO), Flanderns Insti­
    tute to encourage Scientific and Technological Re­
    search in Industry (IWT) and Belgian Federal Office
    for Scientific, Technical and Cultural affairs (OSTC),
    Belgium; Fundaci´on Venezolana de Promoci´on al In­
    vestigador (FVPI), Venezuela; D.F.C. acknowledges
    the support of the NSF CAREER program; E.R. ac­
    knowledges the support of the Marie­Curie fellowship
    program of the European Union; M.R. acknowledges
    the support of the Swiss National Science Founda­
    tion.
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