Neutrino Radiography of the Earth with the IceCube Neutrino Observatory

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1 Neutrino Radiography of the Earth with the IceCube Neutrino Observatory Dec AGU Fall Meeting 2012 in San Francisco Kotoyo Hoshina, Hiroyuki Tanaka and IceCube Collaboration

2 Scan our Earth with Neutrinos! X ray Muon Neutrino small 10 4 ~10 5 ev ~10 13 ev Transmittance ~10 14 ev (10TeV~100TeV) Large

3 History of Neutrino Radiography L.V. Volkova and G.T. Zatsepin (1974) published the original proposal of Neutrino Radiography : using TEVATRON to beam neutrinos through the Earth, detecting them with mobile detectors, and obtaining radiograph images of the Earth. A.D. Rujula et al. (1983) proposed a neutrino factory dedicated to geological science and the discussion of possible experiments. T.L. Wilson (1984) proposed to use Sky neutrinos which are atmospheric neutrinos or extraterrestrial neutrinos. Fig : A.D. Rujula et al. Late 1990 ~ now numerous calculations have been published using : kilometer scale neutrino telescope high-energy atmospheric / cosmic neutrinos

4 Whole Earth vs Mantle atmospheric neutrinos diffuse cosmic neutrinos neutrino beam from accelerator(s) Neutrino beam from astrophysical source(s) Huge Fixed neutrino detector movable neutrino detectors Today s topics neutrino beam from accelerator cavity Off-axis neutrino : low energy and not sensitive to the cavity On-axis neutrino : High energy, sensitive to the cavity Figs : W. Winter arxiv:physics/

5 Tomography or Radiography Neutrino Oscillation Tomography Neutrino Energy up to ~30 GeV Sensitive to the density of electrons, which requires chemical models of the core and mantle in order to convert the result to the densities Provides ample statistics of events (if we use atmospheric neutrinos) Neutrino Absorption Radiography Neutrino Energy up ~TeV to 100 TeV (for Core) Sensitive to the density of protons and neutrons, which can be translated directly into density of core materials Presents challenging to obtain enough statistics of events (if we use atmospheric neutrinos) Neutrino Tomography and Radiography complement each other!

6 Measuring Core Density of the Earth downgoing charged particles non charged particles not detected detected! upgoing γ π 0 π - π + e + e - e + e - µ - µ + e + absorbed ν µ _ ν µ ν e absorbed 147deg 6 North Pole

7 Neutrino Flux Oscillation Increases x 500 per energy decade core ~200 evts after event selection

8 IceCube Structure IC79 IC40 Digital Optical Module (DOM)

9 How is an event reconstructed? Geometry reconstruction (Direction, Position) Large energy loss with electro-magnetic showers use timing and number of arrival photons Energy Reconstruction use number of arrival photons (charge of DOMs) For best reconstruction we have to use our knowledge of ice property (not uniform) (Atmospheric) Muon path

10 Selecting pure neutrino induced upgoing events Single Muon Coincidence Muons Data Atmospheric Neutrino Atmospheric Single Muons Atmospheric Coincidence Muons Before After cos(zenith) cos(zenith)

11 PREM vs FLATCORE model PREM (Preliminary Reference Earth Model) FLATCORE (Density of Core is constant) Density [g/cm 2 ] Density [g/cm 2 ] Radius from the Earth Center [m] cos(zenith) FLATCORE model doesn t conserve Earth s mass, but still useful to estimate the resolution of Earth s density at core angle with the IceCube

12 IC40 Analysis - After event selection Number of Events IC40 Data Simulation Honda 2006 Red box - simulation is fit with data to obtain fit parameters Black box - Using fit parameters, simulations are compared with data Number of Events log10(reco. dedx) IC40 Data Cos(Zenith) preliminary cos(zenith) log10 (reconstruction dedx) *DOM efficiency *slope * norm. IC40 Data Simulation Honda 2006 * fit parameters

13 Comparison of Zenith at Core Region IC40 Data vs Simulations Color mesh shows statistical errors of center of predictions (due to limited simulation statistics) Number of events IC40 1year preliminary Separation of PREM and FLATCORE predictions is within statistical errors of IC40 one year data. IC40 is not sensitive to model difference. cos(zenith)

14 Simulation with IC79 10 years Nevts (Reconstruction Energy >10TeV) very conservative estimation of ~10yr measurement (Calculated with IC79 simulation) PREM FLATCORE Cos(Reconstruction Zenith) Core only, in linear scale Cos(Reconstruction Zenith) Errors are statistical uncertainty of center prediction due to limited simulation statistics

15 Extensions of IceCube DeepCore Already deployed and extends the low energy threshold to 10GeV Obtained data start to present oscillation effects due to the matter PINGU - Low energy extension of IceCube (a developing proposal) Extends energy threshold as low as 1GeV Provides precise measurement of oscillation effect with ample statistics - possible application of Neutrino Oscillation Tomography of the Earth Precision Icecube Next Generation Upgrade) IceCube/DeepCore/PINGU could be a unique facility for both Neutrino Radiography and Neutrino Tomography! Fig : Carsten Rott

16 Summary First study of Neutrino Radiography with IceCube 40 strings is performed. Separation of PREM and FLATCORE predictions is within statistical errors of IC40 one year data, thus IC40 is not sensitive to model difference. New data will be available soon (IC79, IC86) 10 years prediction gives 1 sigma separation at most vertically upgoing bin. Future extension of IceCube (PINGU) could provide an opportunity of Neutrino Oscillation Tomography

17 backups

18 ERI Univ. of Tokyo (Associate Member)

19 Absorption of Neutrino depends on energy Total Column Depth [g/m 2 ] 1.09 x g/m 2 Zenith [deg] Neutrino Cross Section [mb] Oscillation core No Absorption mantle log10(neutrino Energy [GeV]) Mean free path of ~40TeV neutrino is equivalent to the Earth s total column depth at 180 deg

20 Fitting simulation with data at Mantle region Data Simulation Honda 2006 Used atmospheric neutrino model : Honda et al Normalization factor of atmospheric neutrino flux : Ratio between assumed and normal DOM efficiency : log10 (Reconstruction dedx [GeV]) Spectral index correction for the atmospheric neutrino spectrum :

21 dedx is sensitive to muon energy above 1TeV Simulation Atmospheric Neutrino log10 (Reconstruction dedx [GeV]) Poor event statistics Poor energy resolution log10 (True Muon Energy [GeV]) 21

22 Expected Number of Neutrino detected with the IceCube in 10 years Number of Neutrino 10TeV 30TeV 147deg Zenith Angle M. C. Gonzalez-Garcia, Francis Halzen, Michele Maltoni, and Hiroyuki K. M. Tanaka 22 Phys. Rev. Lett. 100, (2008)