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Beck Róbert Fizikus MSc II. ELTE TTK. Topics  Basic information about neutrinos  Past experiments  Neutrino oscillation  Recent and future experiments.

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Presentation on theme: "Beck Róbert Fizikus MSc II. ELTE TTK. Topics  Basic information about neutrinos  Past experiments  Neutrino oscillation  Recent and future experiments."— Presentation transcript:

1 Beck Róbert Fizikus MSc II. ELTE TTK

2 Topics  Basic information about neutrinos  Past experiments  Neutrino oscillation  Recent and future experiments 2

3 What is a neutrino?  „small neutral one” in Italian  Electrically neutral, elementary subatomic particle  Not yet measured, but non-zero mass  Speed very close to speed of light  Interactions: Weak interaction Gravity (negligible) 3

4 History of the neutrino  Existence proposed: 1930, Pauli Negative beta decay  Detected: Cowan-Reines 1956 Reactor produced antineutrinos Detected γ photons from positron annihilation (scintillator) Detected neutrons with cadmium Cross section: 4

5 History of the neutrino types  1962 Lederman, Schwartz, Steinberger: muon neutrino (AGS)  1975 tau particles, tau decay observed – Starnford Linear Acceleration Center  2000 tau neutrino’s interaction directly detected (DONUT)  Muon and tau decay, in analogy to beta decay  No interaction between these at first; SM: no mass 5

6 Historical neutrino experiments  Homestake experiment m underground (gold mine) Raymond Davis, John Bahcall, UPenn 380 m3 perchloroethylene Helium bubbled through to collect the radioactive argon 1/3 of neutrino flux predicted from Sun model 6

7 Historical neutrino experiments  Kamiokande (1983-) Cerenkov-detector Huge array (1000) of photomultiplier tubes Very good directional detection 3000 t of water 1/2 of neutrino flux predicted from Sun model  Super-Kamiokande (1996-) t of water, PMTs Inner and outer detector layers Implosion of 6600 tubes in

8 Historical neutrino experiments  Sudbury neutrino observatory ( ) Uses heavy water (1000 t) Cerenkov-detector with 9600 PMTs Also: neutron capture ○ Deuterium: 6 MeV gamma (small cross sec.) ○ Light water: 2 MeV gamma (large cross sec.) Neutral current detection array (NCD) ○ 3 He filled strings 8

9 Historical neutrino experiments  CC: ν e  NC: ν e, v μ, v τ  Homestake: CC, 1/3 flux  Kamiokande: CC + 1/6 NC, 1/2 flux  SNO: CC, CC + 1/6 NC, NC  Inside the Sun: only ν e are created  Yet: all three flavours arrive to Earth 9

10 Neutrino oscillation  Experimentally proved in 2001 by SNO  Neutrino types: three flavours They can transmute into each other while propagating through space Non-zero mass  Flavor eigenstates != mass eigenstates  Theory proposed by Pontecorvo (1957)  Quantitatively by Maki, Nakagawa, and Sakata (1962); expanded by Pontecorvo (1967) 10

11 Neutrino oscillation  Difference in mass: mass-state phases propagate at different rates  Macroscopic coherence length  Pontecorvo-Maki-Nakagawa-Sakata lepton mixing matrix 11

12 Neutrino oscillation  Pontecorvo-Maki-Nakagawa-Sakata lepton mixing matrix  Mass eigenstate propagation: plane wave  Ultrarelativistic case: 12

13 Neutrino oscillation  3 Θ angles, 3 Δm mass-differences δ, α 1,2 parameters unknown Also sign of Δm 32  Solar, atmospheric, reactor, beam neutrino oscillation Different energies Different circumstances suited for measuring different parameters  Mikheyev–Smirnov–Wolfenstein effect Electrons change propagation eigenstate energy levels due to weak interactions 13

14 Other open questions  What is with helicity? Only left-handed neutrinos, right-handed antineutrinos observed Counterparts either very heavy (seesaw), or do not take part in weak interaction (sterile)  Origin of mass Majorana mass? Higgs-field interaction (should involve both handed particles)? 14

15 Recent neutrino experiments  OPERA - Oscillation Project with Emulsion- tRacking Apparatus (2008-) CERN neutrinos to Gran Sasso project Designed for direct observation of tau neutrinos Beam (pulses) of muon neutrinos Detector: bricks of emulsion material, interleaved with scintillator counters and lead plates, followed by a magnetic spectrometer Real-time tagging of interesting bricks 2010, 2012: tau events 15

16 Recent neutrino experiments  OPERA tau observations To be continued, by Ági 16

17 Neutrinos faster than the speed of light?  High-precision GPS, atomic clocks  Proton pulse, detected neutrinos timestamped  All electronic latencies had to be taken into account  Distance: geodesy, global coordinate system  Maximum likelihood fit of signal shapes  Loose fiber optic cable  Icarus, Borexino, LVD (, OPERA) Gran Sasso detectors using the CNGS beam reported neutrino speeds consistent with the speed of light 17

18 Recent neutrino experiments  IceCube South Pole Neutrino Observatory Location: Amundsen-Scott South Pole Station, Antarctica Why there? ○ Interacting material (ice) already in place ○ Ice easy to drill into (unlike rock) – with specialized hot water drills ○ Detectors lowered into the holes ○ Better shielding from noise sources than anywhere else Completed in

19 Recent neutrino experiments  IceCube South Pole Neutrino Observatory Detectors: Digital Optical Modules, DOMs 86 strings, 60 detectors per string They detect Cherenkov radiation Spacing, calibration: TeV energy neutrinos Angular resolution < 2 degrees Supplementary detectors ○ IceTop ○ Deep Core Low-Energy Extension (<100 GeV) 19

20 Recent neutrino experiments  IceCube South Pole Neutrino Observatory Detection targets ○ Electrons: contained within detector, no source direction -> energy studies only ○ Taus: double-bang to distinguish from e -, distance between DOMs -> PeV energy; none discovered ○ Muons: good sensitivity, source direction detection Main source: cosmic rays, not muon-neutrinos, going downwards, rejected Going upwards through the Earth: caused by muon-neutrinos -Generated by cosmic rays hitting the other side of the Earth -Astronomical sources 20

21 Recent neutrino experiments  IceCube South Pole Neutrino Observatory Experimental targets ○ Extraterrestrial high-energy neutrino point sources Neutrino astronomy Neutrino flux map of the northern hemisphere ○ Gamma ray burst-neutrino coincidence ○ Neutrino oscillation measurements Measure the θ 23 mixing angle of the PMNS matrix ○ WIMP dark matter annihilation in the Sun ○ Cosmic ray composition, energies Difference between IceTop and IceCube events Milky Way supernova rays vs black hole jets (higher E) 21

22 Recent neutrino experiments  IceCube South Pole Neutrino Observatory Results ○ Too few high-E neutrinos found – inconsistent with GRB fireball model, new background flux limit ○ Atmospheric muon neutrino into tau neutrino oscillation measurement at high energies (30 GeV, Deep Core) ○ No excess WIMP-related neutrino flux found, upper limit for the annihilation rate; in the Sun and the GC ○ No neutrino point sources found above noise fluctuation ○ Cosmic ray composition, energy spectrum ○ Other flux limits, experimental concept, background study articles 22

23 Sources  Wikipedia  OPERA website  CNGS website  Fermilab website  IceCube website  Dr. Csótó Attila: Fejezetek a mag- és részecskefizikából course notes   Other various webpages 23

24 Thank you for your attention! 24

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