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