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Neutrinos Beck Róbert Fizikus MSc II. ELTE TTK.

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Presentation on theme: "Neutrinos Beck Róbert Fizikus MSc II. ELTE TTK."— Presentation transcript:

1 Neutrinos Beck Róbert Fizikus MSc II. ELTE TTK

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

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)

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:

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

6 Historical neutrino experiments
Homestake experiment 1478 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

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 2001

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) 3He filled strings

9 Historical neutrino experiments
CC: νe NC: νe, vμ, vτ Homestake: CC, 1/3 flux Kamiokande: CC + 1/6 NC, 1/2 flux SNO: CC, CC + 1/6 NC, NC Inside the Sun: only νe are created Yet: all three flavours arrive to Earth

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)

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

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

13 Neutrino oscillation 3 Θ angles, 3 Δm mass-differences
δ, α1,2 parameters unknown Also sign of Δm32 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

14 Other open questions What is with helicity? Origin of mass
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)?

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

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

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

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 2010

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)

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

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 θ23 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)

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

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

24 Thank you for your attention!

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