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Neutrino “Astronomy” neutrino “astronomy” francis halzen university of wisconsin http://icecube.wisc.edu • introduction • the rationale for building a km3 neutrino detector • IceCube: 3 challenges • drilling • optics of ice • atmospheric muons • neutrino physics: GeV to 100 TeV • PeV neutrinos: first evidence for cosmic neutrinos IceCube.wisc.edu energy (eV) n CMB Radio flux TeV sources Visible cosmic rays rays - g particle flux In the Universe GeV Galactic and extragalactic cosmic rays knee ankle and GZK feature cosmic rays neutrinos produced in interactions of cosmic rays with microwave photons cosmic rays interact with the microwave background p g n and p 0 cosmic rays disappear, neutrinos appear {e e} 6 E 2 10 TeV 1 event per cubic kilometer per year ...but it points at its source • introduction • the rationale for building a km3 neutrino detector • IceCube: 3 challenges • drilling • optics of ice • atmospheric muons • neutrino physics: GeV to 100 TeV • PeV neutrinos: first evidence for cosmic neutrinos IceCube.wisc.edu shock acceleration (solar flare) coronal mass ejection 10 GeV particles flows of charged particles result in large B-fields Hillas formula : • accelerator must contain the particles • dimensional analysis, difficult to satisfy energy (eV) / / galactic cosmic rays / / 10-12 erg cm-3 galactic / cosmic rays/ CMB 10-41 erg/cm3 extragalactic Radio / / cosmic rays / -19 -3 Visible 3x10 erg cm flux / 410 photons / 3 / of 2.7 K per cm / rays or - / g 10-12 erg cm-3 / ~ 0.5 eV cm-3 / / GeV cassiopeia A supernova remnant in X-rays gravitational energy released is trans- formed into acceleration acceleration when particles cross high B-fields neutrinos from supernova remnants : molecular clouds as beam dumps Galactic plane in 10 TeV gamma rays : supernova remnants in star forming regions Standard Deviations Standard Southern Hemisphere Sky 90° 65° 30° 210° milagro neutral pions 0 + - are observed as + - gamma rays g g n n e+ e- charged pions + - are observed as e g e + neutrinos e+ g + e ne n n n g g Cygnus region : Milagro translation of TeV gamma rays into TeV neutrinos : 3 ± 1 n per year in IceCube per source 5s in 5 years of IceCube … IceCube image of our Galaxy > 10 TeV cassiopeia A supernova remnant in X-rays and if the star collapses to a black hole … happens in seconds not thousands of years beamed along the spin axis of the black hole simulation not image collapse of massive star produces a gamma ray burst spinning black hole neutrinos are produced in the interactions of fireball protons (cosmic rays) with synchrotron photons decays to PeV neutrino decays to cosmic ray GRB: one neutrino per cosmic ray observed active galaxy particle flows near supermassive black hole sources accommodating the observed energy budget Galactic: supernova remnants? extragalactic: gamma ray bursts? active galaxies? GRBGZ GRB GZK 100 Galactic supernovae 10 8 9 events per km2yr neutrinos in coincidence with GRB alerts aligned with SWIFT GRB angular accuracy 0.2 deg energy 109 TeV but…. GRB on probation • introduction • the rationale for building a km3 neutrino detector • IceCube: 3 challenges • drilling • optics of ice • atmospheric muons • neutrino physics: GeV to 100 TeV • PeV neutrinos: first evidence for cosmic neutrinos IceCube.wisc.edu M. Markov B. Pontecorvo 1960 M.Markov : we propose to install detectors deep in a lake or in the sea and to determine the direction of charged particles with the help of Cherenkov radiation. • shielded and optically transparent medium Pn nsn R n • lattice of photomultipliers n photomultiplier tube 93 TeV muon energy measurement ( > 1 TeV ) convert the amount of light emitted to measurement of the muon energy (number of optical modules, number of photons, dE/dx, …) why did it take so long ? 2000 AMANDA South Pole Dome 1500 m 2000 m Amundsen-Scott South Pole station [not to scale] AMANDA event: muon neutrino neutrino interaction creates muon track n + p + … analog signal after 2 km… not pretty architecture of independent DOMs 10 inch pmt LED flasher board HV board main board Digital Optical Module (DOM) … each DOM independently collects light signals like this… Digitized Waveform …time stamps them with 2 nanoseconds precision and sends them to a computer that sorts them into muon and neutrino events… IceCube / Deep Core • 5160 optical sensors between 1.5 ~ 2.5 km completed December 2010 • 10 GeV to infinity • ~ 0.5 degree on-line < 0.3 degree off line • < 15% energy resolution Digital Optical Module (DOM) each DOM is independent: continuously sends time- stamped wave forms 89 TeV 43 • introduction • the rationale for building a km3 neutrino detector • IceCube: 3 challenges • drilling • optics of ice • atmospheric muons • neutrino physics: GeV to 100 TeV • PeV neutrinos: first evidence for cosmic neutrinos IceCube.wisc.edu IceCube Site nozzle delivers • 200 gallons per minute • 7 Mpa • 90 degree C 4.8 megawatt heating plant drilling and deployment drill hole and install 60 DOMs in less than two days to 2.5 km 46 absorption length 220m most transparent solid in Nature...or laboratory scattering length 47m … you looked at 10msec of data ! muons detected per year: • atmospheric* ~ 1011 • atmospheric** n ~ 105 • cosmic n ~ 10 * 2700 per second ** 1 every 6 minutes … on to IceCube science we measure the flux of atmospheric muons and neutrinos at higher energies and with better statistics than previous experiments. Any deviations from what is expected is new neutrino physics or new astrophysics. We just look for surprises. • introduction • the rationale for building a km3 neutrino detector • IceCube: 3 challenges • drilling • optics of ice • atmospheric muons • neutrino physics: GeV to 100 TeV • PeV neutrinos: first evidence for cosmic neutrinos IceCube.wisc.edu the atmospheric neutrino “background” but also up to 100 TeV neutrinos for … particle physics … radiography of the Earth … … calibration ! • cosmic neutrinos: energy > 100 TeV • atmospheric background: 1~2 events per year atmospheric neutrino spectrum oscillations in DeepCore [energy ~30 GeV; 5.6 sigma] Vertical Horizontal 57 measured at 10X higher energy IceCube/DeepCore: atmospheric and sterile sensitivity Lsterile potential sterile neutrino limits Esmaili et al, JCAP 1211, 057 • introduction • the rationale for building a km3 neutrino detector • IceCube: 3 challenges • drilling • optics of ice • atmospheric muons • neutrino physics: GeV to 100 TeV • PeV neutrinos: first evidence for cosmic neutrinos IceCube.wisc.edu cosmic rays interact with the microwave background p g n and p 0 cosmic rays disappear, neutrinos appear {e e} 6 E 2 10 TeV ~1 event per cubed kilometer per year GZK neutrinos: > 41,000 photons near the horizon number of channels > 300 unblinding: 2 events in the signal region tracks and showers • energy 1,070 TeV 1,210 TeV (15% resolution) • showers • downgoing • not atmospheric flux at present level of diffuse limit largest bkgd: atmospheric charm < 3 sigma digital optical module 44 on string 20 only GRBGZ GRB GZK 100 Galactic supernovae 10 8 9 events per km2yr search for a diffuse cosmic neutrino flux atmospheric charm cosmic highest energy event 86 • find more contained events (420 Mton) no simulation: • total calorimetry tag muons in the veto region and see what • complete sky coverage fraction is vetoed by the layer of detectors • flavor determined below • some will be muon neutrinos with good angular resolution loss in statistics is compensated by event definition total charge collected by PMTs of events with interaction inside the detector E2Φ(E) = (3.6±1.2)·10−8 GeVcm−2s−1sr−1 atmospheric n and 100 TeV n • 28 events • poisson excess 4.3 sigma atm. background: up neutrinos 4.6 muons 6 down atmospheric muon (blue) + neutrino (red) background + astrophysical E2Φ(E) =(3.6±1.2)·10−8 GeVcm−2s−1sr−1 energy deposited in the detector zenith angle increase in threshold not important (in the region where atmospheric background dominates) Effective volumes DecaCube (1/2/3) IceCube DeepCore Spacing 1 (120m): IceCube (1 km3) + 98 strings (1,3 km3) = 2.3 km3 Spacing 2 (240m): IceCube (1 km3) + 99 strings (5,3 km3) = 6.3 km3 Spacing 3 (360m): IceCube (1 km3) + 95 strings (11,6 km3) = 12.6 km3 “It is not wise to speculate before the data.” Sherlock Holmes “If statistics matters, do a better experiment.” Rutherford • we have another year of data • we will do a better analysis, this one was…. • ….blind (literally) 39 Institutions ~220 collaborators 96 .
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