Neutrino detection

Laura Rossetto

Experimental techniques for particle astrophysics

January 27th 2011

1 Outline • I – About  short history of discovery  different neutrino sources   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 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  observation of missing energy in t decays  the latest particle of the 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

• (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 , 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 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  and nuclear targets produce showers 19 Laura Rossetto – January 27th 2011 II – IceCube

F. Halzen and S.R. Klein, 2010, Review of Scientific Instruments, 81

2. 1. Simulated events of 3 types of neutrino interactions in IceCube:

1. nm + N  X + m

2. ne + N  cascade

3. n + N  t + cascade  3. t 1  cascade1 + cascade2

20 Laura Rossetto – January 27th 2011 II – KamLAND http://kamland.stanford.edu/Pictures/Pictures.html T. Araki et al., 2005, Nature, 436

• KamLAND  Kamioka Liquid AntiNeutrino Detector

• observation of anti-ne emitted by nuclear reactors • a 13-m-diameter transparent balloon containes 1 kton of ultrapure liquid scintillator • the balloon is suspended in non-scintillating oil and surrounded by 1879 PMTs • a 3.2 kton water-Cherenkov detector surrounds the containment sphere, absorbing g rays and neutrons from the surrounding rock and detecting cosmic-ray m

21 Laura Rossetto – January 27th 2011 II – KamLAND http://kamland.stanford.edu/Pictures/Pictures.html T. Araki et al., 2005, Nature, 436

+ • anti-ne are detected via inverse b decay: anti-ne + p  e + n • observation of n oscillation: it detected 258 anti-ne candidate events with E > 3.4 MeV compared to 365.2 ± 23.7 events expected in the absence of n oscillation 2 • most precise measurement of J12 and Dm 12 238 232 • first detector that measured the anti-ne produced in the Earth from the U and Th (geoneutrini)

22 Laura Rossetto – January 27th 2011 II – Borexino

G. Alimonti et al., 2009 , Nuclear Instruments and Methods in Physics Research A, 600

13.7 m

• Large volume liquid scintillator detector 7 8 • it performed measurements of solar n from Be and B through ne elastic scattering • located deep underground (~ 3600 m.w.e.) at the Gran Sasso Laboratory, Italy • 278 tons of liquid scintillator contained in a spherical nylon vessel • the scintillation light is detected via 2212 PMTs located on the inner spherical surface • the sphere is enclosed in a tank filled with 2100 tons of water as shielding for g and neutron background 23 Laura Rossetto – January 27th 2011 III – Supernova neutrinos

• Explosion of the supernova SN1987A in the Large Magellanic Cloud on February 23rd 1987

24 Laura Rossetto – January 27th 2011 III – Supernova neutrinos

• Explosion of the supernova SN1987A in the Large Magellanic Cloud on February 23rd 1987

• a signal associated with the supernova was detected by 4 neutrino detectors: KamiokaNDE–II (Japan)  Cherenkov water detector Irvine–Michigan–Brookhaven (IMB, USA)  Cherenkov water detector Baksan Scintillation Telescope (BST, north Caucasus)  liquid scintillator detector Liquid Scintillator Detector (LSD, Mont Blanc)

• LSD detected 5 pulses with a duration of 7s at 2h 52min 36.8s U.T. (imitation rate = 1.78 · 10–3/day)

• IMB, Kamiokande–II and BST detected a second burst delayed by 4.7 hours in comparison with the LSD one  Koshiba received the Nobel Prize in Physics in 2002 for the first real time observation of supernova neutrinos

• the events detected by IMB, Kamiokande–II and BST are consistent among them

• the events detected by LSD remain still a mystery!!

25 Laura Rossetto – January 27th 2011 III – Supernova neutrinos

Events detected Energy (MeV) Time (U.T.) Dt (s) LSD 5 5.8 – 7.8 2:52:36.8 7 IMB 8 15 – 40 7:35:41 – Kamiokande–II 12 6.3 – 35.4 7:35 13 BST 5 12 – 23.3 7:36:12 9

• Standard core–collapse scenario of a supernova: n create during the formation of the neutron star – (e + p  ne + n) and then in greater abundance during the rapid cooling phase; theoretical calculations predict an average neutrino energy ~ 15 MeV which correspond to a total number of n emitted ~ 1057 – 1058 in few seconds  this standard scenario cannot explain all the events detected in correlation to the SN1987a

• a new scenario have been proposed: a massive rotating star breaks into 2 fragments with masses

M ~ 20 M0 and m ~ (1 – 2) M0 ; the massive component continues to collapse and produces the first neutrino burst during the proto-neutron star formation; the low mass star approaches the massive component and because of gravitational losses it will be disrupted  its matter is accreted by the massive star, thus producing the second neutrino burst

• the problem is still not solved! 26 Laura Rossetto – January 27th 2011 III – SNEWS

• Waiting the next galactic supernova ...

• SNEWS = SuperNova Early Warning System

• the SNEWS project involves several neutrino detectors currently running or nearing completion, like Super–KamiokaNDE, SNO, LVD, IceCube, Borexino, etc.

• the idea is to create an alert network linking several neutrino detectors in coincidence  provide an early warning on the next galactic supernova

• neutrino detection of the next supernova will be very important in understanding the core–collapse scenario, and perhaps explaining the events detected during the SN1987A

27 Laura Rossetto – January 27th 2011 Summary • I – About neutrinos  when and how neutrinos were discovered  the solar neutrino problem and its solution  neutrino oscillation  characteristics of neutrino detection

• II – Neutrino experiments  Cherenkov detectors (Super–KamiokaNDE, SNO, IceCube)  Scintillation detector (KamLAND, Borexino)

• III – SN1987A neutrinos  neutrinos emitted from a supernova were detected for the first time  waiting the next galactic supernova  SNEWS

 new results from neutrino experiments, like IceCube, will probably permit to understand better cosmic rays acceleration in astrophysical sources

28 Laura Rossetto – January 27th 2011 Bibliography

Articles:

• Y. Ashie et al., Measurement of atmospheric neutrino oscillation parameters by Super-Kamiokande I, Physical Review D 71, 112005 (2005)

8 • B. Aharmim et al., Determination of the ne and total B solar neutrino fluxes using the Sudbury Neutrino Observatory Phase I data set, Physical review C 75, 045502 (2007)

• F. Halzen and S.R. Klein, IceCube: an instrument for Review of scientific instruments 81, 081101 (2010)

• A. Achterberg, First year performance of the IceCube neutrino telescope Astroparticle Physics 26, 155 – 173 (2006)

• T. Araki et al., Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion, Physical Review Letters 94, 081801 (2005)

• T. Araki et al., Experimental investigation of geologically produced antineutrinos with KamLAND, Nature 436, 499 – 503 (2005)

• M. Aglietta et al., Neutrino Astrophysics and SN1987A, Il Nuovo Cimento 13, 365 – 374 (1990)

• K.S. Hirata et al., Observation in the Kamiokande-II detector of the neutrino burst from the supernova SN1987, Physical Review D 38, (1990) 29 Laura Rossetto – January 27th 2011 Bibliography

• G. Alimonti et al., The Borexino detector at the Laboratori Nazionali del Gran Sasso, arXiv:0806.2400v1, 2008

• G. Bellini et al., Measurement of the solar 8B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector, arXiv:0808.2868v3, 2010

• C. Arpesella et al., Direct measurement of the 7Be solar neutrino flux with 192 Days of Borexino data, Physical Review Letters 101, 091302 (2010)

Websites:

• Super-KamiokaNDE home page  http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html

• Sudbury Neutrino Observatory (SNO) home page  http://www.sno.phy.queensu.ca/

• KamLAND home page  http://kamland.stanford.edu/

• IceCube home page http://icecube.wisc.edu/

• SNEWS home page  http://snews.bnl.gov/news.html

30 Laura Rossetto – January 27th 2011