Neutrino detection Laura Rossetto Experimental techniques for particle astrophysics January 27th 2011 1 Outline • I – About neutrinos short history of neutrino discovery different neutrino sources neutrino oscillation characteristics of neutrino detection • II – Neutrino experiments Cherenkov detectors: SuperKamiokaNDE Sudbury Neutrino Observatory (SNO) IceCube Scintillation detectors: KamLAND Borexino • III – Neutrinos from SN1987A SNEWS 2 Laura Rossetto – January 27th 2011 I – Neutrino history • The existence of this particle was postulated by Pauli in 1930 to preserve the conservation of – energy, momentum and angular momentum in the b decay ( n p + e + ne ) • the term neutrino was coined by Fermi in 1934 • first detection in 1956 in the so-called Cowan-Reines experiment: n created in a nuclear reactor were detected in a tank of water through the inverse b decay + anti-ne + p n + e • Frederick Reines received the Nobel Prize in Physics in 1995 • nm first detected in 1962 by Lederman, Schwartz and Steinberg Nobel Prize in Physics in 1988 • discovery of the solar neutrino problem in 1967 Davis, Nobel Prize in Physics in 2002 • detection of anti-ne from SN1987a Koshiba, Nobel Prize in Physics in 2002 • nt first detected in 2000 by the DONUT collaboration at FermiLab observation of missing energy in t decays the latest particle of the Standard Model to have been directly observed!!! 3 Laura Rossetto – January 27th 2011 I – Neutrino energy spectrum F. Halzen and S.R. Klein, 2010, Review of Scientific Instruments, 81 • Cosmic neutrino energy spectrum 10-12 eV – 1020 eV • low energy n produced in the Big-Bang • E ~ 106 eV n produced by Supernovae solar n • 108 eV < E < 1011 eV atmospheric n • above ~ 1011 eV n from extragalactic sources • highest energy decay products of p’s produced via interactions of cosmic rays with background microwave photons 4 Laura Rossetto – January 27th 2011 I – Solar neutrino problem • First experimental evidence in the Homestake Gold Mine experiment (South Dakota) in 1967 • the leader of the experiment was Raymond Davis who received the Nobel Prize in Physics in 2002 8 7 • the idea was to detect solar ne emitted by the decay of B and Be in the Sun via the reaction 37 37 – Cl + ne Ar + e • the experiment was built in the mine at 1478 m underground and it consisted of 100000 gallon tank of perchloroethylene C2Cl4 , rich in chlorine • first results: upper limit 3SNU , 1 SNU = 10–36 captures (target atom)–1 s–1 • predictions from the standard solar model (Bahcall & Shaviv, 1967) 7.5 ± 3 SNU • the solar neutrino problem the ne produced in the Sun turned to be only 1/3 of those expected results confirmed by KamiokaNDE, Gallex, SNO, KamLAND later on this luck of n was interpreted as neutrino oscillation R. Davis, 2003, ChemPhysChem, 4 5 Laura Rossetto – January 27th 2011 I – Neutrino oscillation • First pointed out by Pontecorvo in 1957 • oscillation the 3 n species are constituted by a mixing of 3 mass eigenstates (1, 2, 3) • the mixing matrix is: ne n1 The probability of a neutrino changing its flavour is: nm = U n2 ( n ) ( n ) t 3 c12 = cosJ12 , s12 = sinJ12 , J12 mixing angle 1–2 c13 = cosJ13 , s13 = sinJ13 , J13 mixing angle 1–3 c23 = cosJ23 , s23 = sinJ23 , J23 mixing angle 2–3 6 Laura Rossetto – January 27th 2011 I – Neutrino oscillation Observed values of oscillation parameters: • SNO (solar neutrinos) and KamLAND (nuclear reactor neutrinos) 2 Sen (2J12) = 0.82 ± 0.07 n n 2 –5 2 e m Dm 12 = 8.0 · 10 eV T. Araki et al., 2005, Physical Review Letters 94, 081801 • Super–KamiokaNDE (atmospheric neutrinos) 2 Sen (2J23) > 0.92 n n –3 2 –3 2 m t 1.5 · 10 < Dm 23 < 3.4 · 10 eV Y. Ashie et al., 2005, Physical Review D 71, 112005 • CHOOZ (nuclear reactor neutrinos) 2 Sen (2J13) < 0.2 at 90% C.L. n n 2 –3 2 e t assuming Dm 13 = 2 · 10 eV S. Eidelman et al., 2004, Particle Data Group, Physics Letters B, 592 M. Apollonio et al., 2003, The European Physical Journal C 27, 331 7 Laura Rossetto – January 27th 2011 I – Characteristics of neutrino detectors • Neutrino detectors must be underground large background radiation from cosmic rays interaction in the atmoshpere • very large detector is required very small neutrino cross section (s ~ 10–41 cm2) • flavour identification is needed atmospheric nm >> atmospheric ne and nt • good energy resolution important for identifying where neutrinos are produced (i.e. atmospheric n, Supernovae n, extragalactic sources) 8 Laura Rossetto – January 27th 2011 I – Characteristics of neutrino detectors • Cherenkov detectors – + charged-current interactions: ne + n p + e , anti-ne + p n + e – – elastic scattering: nx + e nx + e positrons and electrons emitted Cherenkov light KamiokaNDE – SuperKamiokaNDE Sudbury Neutrino Observatory (SNO) AMANDA – IceCube Antares, NEMO, NESTOR – KM3NeT • Liquid scintillation detectors detection of the fluorescence light emitted by excited substance + (usually fluoride organic compound): anti-ne + p n + e KamLAND Borexino CHOOZ LVD 9 Laura Rossetto – January 27th 2011 I – Characteristics of neutrino detectors Cherenkov detectors Liquid scintillation detectors Production of light 100 photons/MeV 10000 photons/MeV Direction information YES NO Costs low high Dimensions 50 ktons – 1 km3 up to 1 kton (SuperKamiokaNDE – IceCube) 10 Laura Rossetto – January 27th 2011 II – Super-KamiokaNDE • Evolution of the previous KamiokaNDE = Kamioka Nucleon Decay Experiment • atmospheric n observed via charged–current interactions 2 • it measured Dm 23 and J23 http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html • 50 ktons water Cherenkov detector located at the Kamioka observatory, Japan • rock overburden of 2700 m.w.e. • two concentric cylindrical 42 m 42 detectors Mt. Ikenoyama • inner detector 11146 PMTs • outer detector cylindrical shell of water 2.6 – 2.75 m thick; 1885 outward-facing PMTs 39.3 m (4p active veto, thick passive radioactivity shield) 11 Laura Rossetto – January 27th 2011 II – Super-KamiokaNDE • Evolution of the previous KamiokaNDE = Kamioka Nucleon Decay Experiment • atmospheric n observed via charged–current interactions • it measured Dm2 and J 23 23 http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html 42 m 42 Mt. Ikenoyama 39.3 m 12 Laura Rossetto – January 27th 2011 II – Super-KamiokaNDE The outer PMTs permit to distinguish between neutrino and cosmic ray particle Inner detector Outer detector http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html nm event ne event – – nm + N X + m ne + e ne + e a Cherenkov ring is emitted the emitted electron generates an electromagnetic shower which is very similar to a Cherenkov ring 13 Laura Rossetto – January 27th 2011 II – Sudbury Neutrino Observatory (SNO) Heavy-water Cherenkov detector designed to detect solar neutrino and 2 to observe the neutrino oscillation flavours (Dm 12 and J12) http://www.sno.phy.queensu.ca/ • Built at 2070 m (~ 6000 m.w.e.) below ground in the Creighton mine near Sudbury, Canada • two concentric spherical detectors immersed in water (H2O) within a 30 meter barrel-shaped cavity Acrylic vessel • 1000 tons of heavy-water (D2O) contained by a 12 m diameter (D2O) transparent acrylic vessel Inner H2O (inner sphere) (1.7 kT) • 9600 PMTs mounted on a Outer H O 2 geodesic support structure which (5.7 kT) surrounds the heavy-water vessel 14 Laura Rossetto – January 27th 2011 II – Sudbury Neutrino Observatory (SNO) proton – proton chain in which solar neutrinos are produced (Standard Solar Model) http://www.sno.phy.queensu.ca/ Charged current reaction – ne + D p + p + e W • it occurs only for ne at solar neutrino energies ( ~ 100 keV – 10 MeV) • the recoil e– energy is strongly correlated with the incident n energy precise measurement of the 8B n energy spectrum 15 Laura Rossetto – January 27th 2011 II – Sudbury Neutrino Observatory (SNO) http://www.sno.phy.queensu.ca/ Electron scattering – – e + nx e + nx • the recoil e– direction is strongly correlated with the direction of the incident n (direction to the Sun) • it’s sensitive to all n flavours • s(ne) ~ 6.5 s(nm , nt ) Neutral current reaction nx + D p + n + nx • it’s sensitive to all n flavours • it provides a direct measurement of the total flux of 8B n from the Sun 16 Laura Rossetto – January 27th 2011 II – IceCube • 1 km3 of Antarctic ice acts as a large F. Halzen and S.R. Klein, 2010, Review of Scientific Instruments, 81 tracking calorimeter • 86 vertical strings arranged on an hexagonal grid (covering 1 km2 of the surface) with 60 DOMs each; the total number of DOMs is 5160 • DOMs are attached to the strings every 17 m between 1450 m and 2450 m DOMs • DeepCore 6 strings situated on a denser 72 m triangular grid • strings deployed in the ice using hot-water drill • the complete IceCube will observe several hundred n/day with E > 100 GeV; Construction will be completed in January 2011 DeepCore will observe n with energy up to ~ 10 GeV 17 Laura Rossetto – January 27th 2011 II – IceCube A.Achterberg et al., 2006, Astroparticle Physics, 26 • Each PMT is enclosed in a transparent pressure sphere Digital Optical Module (DOM) • a DOM also contains a digitally controlled high voltage supply 35 cm and a data acquisition system • IceTop surface air-shower array consisting of 160 ice-filled Tanks of the tanks (2 tanks for each string), IceTop array each instrumented with 2 DOMs • IceTop detects cosmic-ray air showers with a threshold of about 300 TeV 18 Laura Rossetto – January 27th 2011 II – IceCube F. Halzen and S.R. Klein, 2010, Review of Scientific Instruments, 81 ~ km–long muon tracks from nm ~ 10m–long cascade from ne , nt • IceCube detects n by observing the Cherenkov radiation from the charged particles produced by n interactions • m tracks from nm are ~ km–long the m direction can be determined accurately (IceCube angular resolution is better than 1° for long tracks) • tracks from ne and nt are shorter leptons and nuclear targets produce showers 19 Laura Rossetto – January 27th 2011 II – IceCube F.