Download NEUTRINOS

F. TASNÁDI
LINKÖPING UNIVERSITY
THEORETICAL PHYSICS
NEUTRINO OSCILLATIONS & MASS
thefundamentaldiscoveriesinphysicscon4nues
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CONGRATULATIONS - NOBEL PRIZE IN PHYSICS 2016
… the secrets of exotic matter
/quantum physics becomes visible in the cold/
David J. Thouless
F. Duncan M. Haldane
J. Michael Kosterlitz
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ONE WAY OF DOING FUNDAMENTAL PHYSICS
LHC
Higgs boson the
“God particle”
27 KM
STANDARD MODEL
125 GeV
4 July 2012
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ANOTHER WAY OF DOING FUNDAMENTAL PHYSICS
SUSY
supersymmetry
fermions
bosons
(super)string theory
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PARTICLE WORLD - THE STANDARD MODEL
/1970 - ???/
neutrinos
flavours
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METAMORPHOSIS IN THE PARTICLE WORLD - NOBEL 2015
“The Nobel Prize in Physics 2015 recognises Takaaki Kajita in
Japan and Arthur B. McDonald in Canada, for their key
contributions to the experiments which demonstrated that neutrinos
change identities (flavours). This metamorphosis requires that
neutrinos have mass. The discovery has changed our understanding
of the innermost workings of matter and can prove crucial to our view
of the universe.”
http://www.nobelprize.org
Takaaki Kajita Arthur B. McDonald
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SOURCES OF NEUTRINOS
Trillions of neutrinos passing through our bodies every second — almost all of these
are produced in fusion reactions in the Sun's core.
Solar neutrinos
Atmospheric neutrinos
Other sources:
Big Bang
cosmic rays
Supernovas
…
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WHAT IS A NEUTRINO? - THE POLTERGEIST “PARTICLE”
beta decay:
energy conservation:
1929, Niels Bohr: …”possible limitation
of the conservation theorems …”
1930: W. Pauli’s letter:
“Dear Radioactive Ladies and Gentlemen …
there could exist electrically neutral particles, which I will call “neutrons”, that have
spin 1/2 and obey the exclusion principle and that further differ from light quanta in
that they do not travel with the velocity of light. The mass of the “neutrons” should
be of the same order of magnitude as the electron mass and in any event not larger
than 0.01 proton mass. ”
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WHAT IS A NEUTRINO? - THE REAL PARTICLE
1931: The name neutrino by E. Fermi “the Italain little neutral one”
1934: The theory of beta decay by E. Fermi - (anti)neutrinos are included, produced!
1934, Niels Bohr: “… I don’t yet feel fully convinced of the physical existence of the neutrino.”
1956: “Poltergeist is OVER” F. Reines & C. Cowan detect the trace of (anti)neutrino
scintillation detector
Reines & Cowan
1958: neutrinos are ALWAYS left-handed
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THE HANDEDNESS - THE VAMPIRE NEUTRINO PARTICLE
momentum vs. spinning = handedness
p~
p
~
⌫
~
S
~
S
neutrino
mirror
1957, Abdus Salam: “On reflecting a neutrino in a mirror, one sees nothing.”
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THE MASS - NO AGE OF THE NEUTRINO
special relativity: massive particle can NEVER travel at the speed of light
left-handed
A
two-handed
⌫¯
vA
right-handed
B
MASSLESS NEUTRINO
Using massless particles in Dirac’s
equations violates left-right symmetry
and results in two ‘components’
equation - neutrino (left) &
antineutrino (right).
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THE FLAVOURS- THE DIFFERENT NEUTRINOS
1937: the muon or “heavy electron” from cosmic ray
1949: pion, Yukawa’s particle
Bruno Pontecorvo in Dubna - investigate the muon decay:
µ!e +
µ ! e + 2⌫
conserve the ‘muon-ness’
n ! p + e + ⌫¯
TWO TYPES OF NEUTRINO
⌫ e , ⌫µ
conserve the ‘electron-ness’
1975: a new lepton was found: the tau
conserve ‘tau-ness’
THREE FLAVOURS OF NEUTRINO
⌫ e , ⌫µ , ⌫⌧
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WHAT IS A NEUTRINO? - IN THE STANDARD MODEL
MASSLESS & LEFT-HANDED “VAMPIRE”
el
d
o
m
d
r
a
d
n
sta
NEUTRINO
|ei
|µi
|⌧ i
electron-flavour
muon-flavour
tau-flavour
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MASS EIGENSTATES - SHORT QUANTUM MECHANICS
special relativity, energy & momentum conservation:
particle
particle stays in this mass eigenstate
E 2 = p2 c2 + m2 c4
E, p ! m
NO OSCILLATION between different |mi states.
|mie
particle
i
m (t)
|f1 i
spontaneously
|f2 i
|f1 i, |f2 i ARE NOT MASS EIGENSTATES!
It is ‘nonsense’ to speak about the mass if the
particle is characterised by fi quantum numbers
!
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BECAUSE ONLY PARTICLE WITH MASS CAN OSCILLATE
/1957, B. Pontecorovo suggests neutrino oscillation/
neutrino
|µi
⌫
spontaneously
|ei, |µi ARE NOT MASS EIGENSTATES!
P e
i mj (t)
|ei = j j |mj ie
P µ
i mj (t)
|µi = j j |mj ie
|ei
/coherent superposition/
Flavour oscillation can happen only if the mass eigenvalues are different!
The zero eigenvalue is excluded by the fact that all neutrinos are oscillating.
⌫e = coherent superposition of mass states
W
e
NEUTRINOS
HAVE MASS
+
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SOLAR (E-)NEUTRINO PROBLEM (1968) - HOMESTAKE EXP.
deficit of solar neutrinos
SK: Super Kamiokande
SNO: Sudbury Neutrino Observatory
theoretical rate:
8.5 ± 0.9 SNU
Standard Solar Model
experimental rate:
2.56 ± 0.32 SNU
SNU: Solar Neutrino Unit
1 SNU = 1 reaction per 1036 target per second)
p + p ! 2 H + e+ + ⌫ e
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8
⇤
+
B ! Be + e + ⌫e
NEUTRINO OSCILLATION?
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EXPENSIVE “DEEP & DARK SCIENCE” IN JAPAN & CANADA
SUPER KAMIOKANDE:
-
operational in 1996 (started 1991)
zinc mine
1000 m below Earth surface
50,000 tonnes of pure water (light beam can travel 70 m before intensity is 1/2)
more than 13,000 light detectors to detect Cherenkov radiation
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B solar neutrinos
muon neutrinos (atmospheric)
SUDBURY NEUTRINO OBSERVATORY:
-
operational in 1999
1,000 tonnes heavy-water and for extra shielding ultra-pure water
9500 light detectors
all flavours of neutrinos (including 8B solar neutrinos)
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SUPER KAMIOKANDE (SK) KAMIOKA, JAPAN
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SUDBURY NEUTRINO OBSERVATORY (SNO) CANADA, ONTARIO
photo: Lawrence Berkeley Nat'l Lab
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ICECUBE - ANTARCTICA
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ICECUBE - THE LABORATORY
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ATMOSPHERIC NEUTRINOS IN SK - YEAR 1998
⌫x + e ! ⌫x + e
ISOTROPIC FLUX
long (⌫µ )
short (⌫µ )
⇡ 50%
The nobel prize in physics 2015, Popular science background
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NEUTRINOS IN SNO - YEAR 2001
⌫x + e ! ⌫x + e
reaction-1: ⌫e + 2 H ! e + p + p
reaction-2: ⌫x + 2 H ! ⌫x + p + n
reaction-1
1 (⌫e , Sun)
reaction-2
2 (all, Sun)
2 (all, Sun)
=
theory (⌫e , Sun)
The nobel prize in physics 2015, Popular science background
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NEUTRINO MASS - CONTRADICTIONS! STANDARD MODEL?
Contradiction between left-handedness and mass!
Solution?
1) right-handed neutrinos are not detected
2) extremely weak weak-interaction
Dirac neutrino
Majorana neutrino
⌫ = ⌫¯
⌫ 6= ⌫¯
superstring theory (11 dimensions)
mass by Higgs mechanism
experimentalists
matter=antimatter
mass by Higgs mechanism
theorists
supersymmetry (SUSY), string theory, etc…
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FUNDAMENTAL “PHILOSOPHY”
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WE NEED THE TECHNOLOGY TO MAKE IT
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CMS DETECTOR
THANK YOU
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MUON AND TAU NEUTRINOS (SNO WITH SK)
reaction-1
3.26
reaction-2
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THE “AMAZING” NEUTRINOS - PROPERTIES
- In our Universe what we see are stars, galaxies, … but what we do not see that the
Universe is filled with neutrinos, the second most abundant particles in the Universe
after photons; every cm3 of space contains around 300 neutrinos.
- Trillions of neutrinos are passing through our bodies every second — almost all of these are
produced in fusion reactions in the Sun's core - interact only with the weak force.
H2 O
⇡ 1.7 ⇥ 1017 m ⇡ 106 ⇥ d(Sun-Earth)
Pb
⇡ 1.5 ⇥ 1016 m
- Direct mass measurements: “massless”?
- Indirect mass measurements:
5
5 ⇥ 10 m⌫e
mp
⇡ me ⇡
1840
m⌫ > 0
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