Measuring the total neutrino cross section using the IceCube detector

1. Measuring the total neutrino cross section using the IceCube detector Sandy Miarecki University of California-Berkeley Lawrence Berkeley National Lab Neutrino Summer School, July 2011

2. IceCube at the South Pole IC22 (2007) IC40 (2008) IC09 (2006) IC86 (2011) IC59 (2009) IC79 (2010) IceTop 81 stations x 2 tanks 2.5 km IceCube Lab (ICL) central computing facility IceCube 80 strings ~125 m spacing 60 DOMs per string ~17 m spacing DeepCore array of 6 strings 60 DOMs per string ~7 m spacing

3. IceCube Sensors • Digital Optical Modules (DOMs) • Hamamatsu 25 cm PMTs with digitized waveforms • Quantum efficiency is higher for DeepCore than IceCube DOMs • IceCube detects the Cherenkov photons from charged particles • ~70,000 upgoing muons/year • Energies 10 GeV-1 EeV • Supernovae, neutrino point sources, dark matter, neutrino oscillations, magnetic monopoles, and much much more !

4. Energy Differences (simulated events) Eµ= 10 TeV, 90 hits Eµ= 6 PeV, 1000 hits • Color of DOM indictates time of arrival (red to purple) • Size of DOM indicates number of photoeletrons (PE)

5. Neutrino cross section • Neutrinos are "detected" when they interact in the Earth and create muons • Idea: examine neutrino absorption in the Earth to find total neutrino-nucleon cross section • Use atmospheric neutrinos as luminosity source • Use current Earth model for density profile • Approximately 20,000 "upgoing" muon events seen in IceCube per year > ~1 TeV (IC79 config) • Compare event rate per zenith angle per energy to expected values to calculate total nm cross section

6. Atmospheric neutrinos Atmospheric muon neutrino flux interaction length vs. energy • Cosmic rays (mainly protons and He ions) interact with atmosphere, form kaons and pions, decaying into neutrinos • Earth diameter ~interaction length ~40 TeV • Higher zenith angles = higher absorption • Higher neutrino energies = higher absorption Effective Earth diameter area of thesis interest Neutrino Neutrino Energy IceCube: arXiv:1010.3980v2 R. Gandhi: arXiv:hep-ph/9512364v1

7. Preliminary Reference Earth Model (PREM) Zenith = 180 deg Ave r= 8.0 g/cm3 Dist = 12,742 km Muon energy measurement is very important to the results Zenith = 150 deg Ave r= 4.0 g/cm3 Dist = 11,035 km 2,200 km Zenith = 120 deg Ave r= 3.2 g/cm3 Dist = 6,371 km Zenith=100 deg will provide a near zero-absorption baseline Zenith = 100 deg Ave r= 2.6 g/cm3 Dist = 2,213 km

8. Energy Calculation Method(Truncated Mean) Preliminary Preliminary • Similar method to wire chamber and calorimeter studies by omitting highest wire measurements • Energy resolution improved by ~40% • Significant decrease in scatter with cuts

9. The Collaboration Sweden: Uppsala Universitet Stockholm Universitet Germany: Universität Mainz DESY-Zeuthen Ruhr-Universität Bochum Universität Dortmund Universität Wuppertal Humboldt Universität Universität Bonn MPI Heidelberg RWTH Aachen Canada: University of Alberta UK: Oxford University USA: Pennsylvania State University Lawrence Berkeley National Lab University of California-Berkeley University of California-Irvine Clark-Atlanta University Georgia Institute of Technology University of Maryland Ohio State University University of Wisconsin-Madison University of Wisconsin-River Falls University of Kansas University of Delaware-Newark University of Alabama-Tuscaloosa Southern University and A&M College, Baton Rouge University of Alaska, Anchorage Barbados: University of the West Indies Japan: Chiba University Belgium: Université Libre de Bruxelles Vrije Universiteit Brussel Universiteit Gent Université de Mons-Hainaut Switzerland: EPFL New Zealand: University of Canterbury 36 institutions, ~250 members http://icecube.wisc.edu

10. Questions?

11. dE/dx References • Auchincloss, P.S., “A study of the energy dependence of the mean, truncated mean, and most probable energy deposition of high-energy muons in sampling calorimeters”, Nucl. Instr. and Meth. in Phys. Res. A, 343 (1994) 463-469. • Cowen, Glen, “Ideas on Particle Identification Using Ionization Energy Loss”, ALEPH 95-101, TPCGEN 95-001, August 15, 1995 (Univ of Siegen). • Bichsel, Hans, “Particle Identification at Star-TPC with Ionization Measurements”, Astroparticle, Particle and Space Physics, Detectors And Medical Physics Applications, Sep 2003. • Bichsel, Hans, “A Method to Improve Tracking and Particle Identification in TPCs and Silicon Detectors”, Nuclear Instruments and Methods in Physics Research A, 562 (2006) 154–197.

12. Neutrino References • Gaisser, T. et al, “Particle Astrophysics with High Energy Neutrinos”, Phys. Reports 258 (1995) 173-236. • Gandhi, R. et al, “Ultrahigh-Energy Neutrino Interactions”, Astropartricle Physics 5 (1996) 81-110. • Lipari, P., and Stanev, T., “Propagation of Multi-TeV Muons”, Phys. Rev. D v.44, n.11, 1 Dec 1991. • Gaisser, T., “Atmospheric Neutrino Fluxes”, arXiv:astro-ph/05023801 v1, 18 Feb 2005. • Particle Data Group, "Plots of Cross Sections and Related Quantities", pdg.lbl.gov/2011/reviews/rpp2011-rev-cross-section-plots.pdf • Dziewonski, A., and Anderson, D., "Preliminary Reference Earth Model", Phys. Earth Planet. Inter. 25:297-356.

13. The End

14. Digital Optical Modules • 25 cm PMT • 12 LED flashers for calibration • full digitized waveforms:Analogue Transient Waveform Digitizer (ATWD) 400 ns / 320 MHz samplingx 3 different gainsFast ADC6.4 μs / 40 MHz sampling

15. Neutrino x-section (PDG)(E < 350 GeV)

16. Toy Model slide Gaisser Halzen Stanev 1995 Gaisser Halzen Stanev 1995 Gandhi 1996 X(q) = density * distance stot(E) ~ 0.96x10-35 * E0.80

17. dE/dx Energy Method • Calculate the expected PE for each event • Compare to the actual PE for each event • Use energy equation: dE/dx = A + B*E to get E • Roughly linear > 850 GeV • A = 0.931 x 0.25958 GeV/m (ionization) • B = 0.931 x 3.5709e-4 /m (brem, pair, nuclear) • Affected by large errors due to random PE spikes Total PE (actual) = dE/dx (GeV/m) Total PE (expected)

18. IceCube Energy Method • Muon energy reconstruction has sizeable uncertainties due to large stochastic losses • Distribution of energy losses (dE/dx) for events has a long high-energy tail The mean should be in here… Number of Events …but these events skew the mean Calculated dE/dx (GeV/m)

19. Typical 10 TeVMuon (simulation) • Detector view • Plot of photoelectrons (PE) per bin • High PE seen in bin 1 and bin 5 • High PE bins skew the average dE/dx calculation, which is used for energy reconstruction Number of PE

20. Truncated Mean Method • Wire chamber and calorimeter studies of charged particles had a similar energy resolution problem • Wires detected ionization energy at intervals • The resolution improved by ~40% by omitting highest 30-50% of wire measurements • Truncated Mean Particle X X X X Wires

21. Truncated Bins • Binning DOMs within cylinder 20-80m from track • Minimum of 3 bins for event to qualify • Cut highest 10%, 20%, etc. of bins • Most precise cut at 40% • Get new dE/dx values for simulated events • Plot LOG10 dE/dx vs. actual sim energy (center) • Determine new constants for energy equation • Calculate the new energy for each event • Works for all zenith angles (full detector)

22. Progression of Truncations10 TeV – 100 PeV Preliminary • LOG10 plots of dE/dx vs. MMC energy • Significant decrease in scatter with cuts • Lower energies also improved Preliminary 0% bins cut 20% bins cut Preliminary 40% bins cut