1 / 26

Search for Neutrino-Induced Cascades in AMANDA II

Search for Neutrino-Induced Cascades in AMANDA II. Marek Kowalski DESY-Zeuthen Workshop on Ultra High Energy Neutrino Telescopes Chiba, 29.7.2003. Outline. Introduction Reconstruction of cascade-like events Searching for cascade-like events in the AMANDA II data Summary. S.

dylan-jimenez
Download Presentation

Search for Neutrino-Induced Cascades in AMANDA II

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Search for Neutrino-Induced Cascades in AMANDA II Marek Kowalski DESY-Zeuthen Workshop on Ultra High Energy Neutrino Telescopes Chiba, 29.7.2003 M. Kowalski

  2. Outline • Introduction • Reconstruction of cascade-like events • Searching for cascade-like events in the AMANDA II data • Summary M. Kowalski

  3. S Neutrino-Induced Cascades: Signal and Background • Signature ofne and nt are hadronic and electro-magnetic cascades. • Neutral Current interactions of all neutrino flavors produce hadronic cascades • Background consists of atmospheric muons, emitting energetic secondaries ~ 5 m M. Kowalski

  4. Why search for Neutrino-Induced Cascades? Advantages: • Large Sensitivity for ne and nt • Local events, therefore better energy resolution • Less intrinsic background of atmospheric muons & neutrinos • Nearly 4 p sensitivity Disadvantages: • Less signal than in the muon channel due to very large muon range • Worse angular resolution • Local events, therefore better energy resolution • Less background of atmospheric neutrinos • Less signal than in the muon channel since muon range very large M. Kowalski

  5. Reconstructing Cascades: Vertex Position Without scattering With scattering far track 0t t close track 0t 0t M. Kowalski

  6. Vertex Resolution Reconstruction of 1 TeV EM cascades which trigger AMANDA II Vertex resolution of cascades in the detector: (radius 100 m, height = 200 m) s ~ 5 m for x,y,z coordinates and large range of energies. M. Kowalski

  7. Parameterization of hit-probability with MC. Function is random walk inspired: Construction of Likelihood function: Energy Reconstruction M. Kowalski

  8. Reconstruction of EM cascades of energies: 102, 103 , 104 ,105 ,106 GeV. Vertex within AMANDA II.(radius = 100m, height =200m) Vertex fitted with time-likelihood. Resolution of Energy Reconstruction <7.1 s(logE) < 0.2 M. Kowalski

  9. Testing Reconstruction with In-Situ Light Sources data Vertex reconstruction: Reconstructing position of YAG laser light emitters (position known to ~ 1 m). mc Energy reconstruction: LEDs (UV 370 nm) run at different intensities. Reconstructing energy of LED events (20 % resolution) . Absolute intensity not known, but relative Intensities reconstructed correctly. M. Kowalski

  10. The cascade filter Starting with 1.2 x 109 events (in the 2000 data set) 7 cuts to reduce background The full likelihood reconstruction is performed after cut # 2 Final cut M. Kowalski

  11. Final cut variable Variables merged into one “Bayesian Discriminator” (thereby neglecting correl.) M. Kowalski [m]

  12. Cuts are optimized on MC to obtain best sensitivity. Sensitivity is defined as average upper limit on: F(E)= const x E-2 / (GeV s sr cm2) L-logE space scanned and sensitivity calculated (performing a counting rate experiment) Optimizing the Final Cut in L-logE space M. Kowalski

  13. Final energy spectrum Energy cut chosen by MC Optimization 2 events passed all cuts M. Kowalski

  14. The highest energy event (~200 TeV) 300 m M. Kowalski

  15. Effective Volume for ne ,nm and nt M. Kowalski

  16. [ g=3.0,2.5,2.0,1.5,1.0 ] Upper limits on the diffuse flux • Nobs=2; Nbg=0.5+0.5-0.3 • Upper bounds on the diffuse flux of astrophysical neutrinos (at 90% CL) for different assumed spectras: F(E) ~ E-g ; g=1-3 • Limit on tau neutrinos 25 - 30 % worse than for electron neutrinos • Glashow resonance at 6.3 PeV results in differential ne limit M. Kowalski

  17. Comparision with other Limitsand Models Preliminary (2000 data) [ SSDS [ [ MPR units: model rejection factor * assuming a flavor ratio 1:1:1 M. Kowalski

  18. Conclusions • Cascades interacting within AMANDA can be reconstructed with a resolutions: sx,y,z=5 m, sq=30o- 40o and slogE=0.1-0.2 • A search for neutrino-induced cascades in the data of the first year of AMANDA II was performed. No significant excess over background was seen! • Upper limits set on the diffuse flux of neutrinos, ruling out several AGN flux models. • AMANDA can be considered an all flavor neutrino detector! M. Kowalski

  19. Back Up M. Kowalski

  20. Angular detector sensitivity nearly uniform.Depletion due to propagation through the earth. Example:ne @ 1 PeV M. Kowalski

  21. M. Kowalski

  22. The AMANDA detectorat the South Pole • Detector deployed ~2 km deep into Antarctic ice • Instalation of 10 strings in 1996/97 (referred to as AMANDA-B10) • Comissioning of AMANDA II in 2000 consisting of 19 strings and 677 OMs M. Kowalski

  23. First Level Cascade Filter The discriminating variables are based on fast estimate of vertex position & time Late hits (but causal) Direct hits: c (ti-200 ns) < d < c ti Early hits (non causal!): d > c ti M. Kowalski

  24. Nearly/Nhits Ndirect First Level Cascade Filter M. Kowalski

  25. Final Level Cascade Filter Energy spectrum of remaining events M. Kowalski

  26. Systematic uncertainty on signal sensitivity M. Kowalski

More Related