The Ghostly Neutrino
Steve Boyd, University of Warwick
“If we are to understand “why weare here” and the basic propertiesof the universe we live in, we mustunderstand the neutrino.”
American Physical Society Report - 2004
A little bit of history
What are they?
Where do they come from?
Why study them?
A recent surprise
The T2K Project
CRISIS
Energy(Ra) ≠ Energy(Ac)+Energy(e)
“At the present stage of atomictheory we have no argumentsfor upholding the concept ofenergy balance in the case ofb-ray disintegrations.”
Neils Bohr
Wolfgang Pauli
“Desperate remedy.....”“I do not dare publish this idea....”“I admit my way out may look improbable....”“Weigh it and pass sentence....”
“You tell them. I'm off to a party”
Energy(Ra) ≠ Energy(Ac)+Energy(e)
Energy(Ra) Energy(Ac)+Energy(e)+ Energy(Neutrino)
What are neutrinos?
Electron, e
Tiny mass ( 1 )
-
Electron Neutrino, ne
0
Very tiny mass(<0.0000001)
Electron, e
Tiny mass ( 1 )
-
x 500
Very tiny mass(<0.0000001)
e
ne
e
ne
Electron Neutrino, ne
0
Very tiny mass(<0.0000001)
Electron, e
Tiny mass ( 1 )
-
In experiments neutrinos are NEVER seen.
We can only detect them through the byproducts of their interactions with matter.
Type of the charged particle detected used to infer the type of incoming neutrino.
e e
Electron Neutrino, ne
Electron, e
mass ( 1 ) -Muon Neutrino, nm
Muon, m
mass ( 200 ) -TauNeutrino, nt
Tau, t
mass ( 3500 ) -3 Lepton Types
m
ne
t
ne
Electron Antineutrino, ne
Positron, e+
mass ( 1 ) +
3 Antiparticles
Muon Antineutrino, nm
Muon, m+
mass ( 200 ) +Tau Antineutrino, nm
Tau, t+
mass ( 3500 ) +
Where do they come from?
Everywhere
From the Big Bang
Artist's conception
From the Big Bang
Artist's conception
One cubic foot of space contains about 10,000,000 neutrinos leftover from the Big Bang.
From Astrophysical Objects
Supernovae created the heavy elements (us) and neutrinos appear to be important to the explosion dynamics.
From the Sun
≈ 70 million per cm2 per second at the Earth
From Cosmic Rays.
Geoneutrinos
From Us.
So why don't we notice?
n are almost ghosts. They interact extremely weakly with matter.
To a neutrino a planet is mostly empty space.
"The chances of a neutrino actually hitting something as it travels through all this howling emptiness are roughly comparable to that of dropping a ball bearing at random from a cruising 747 and hitting, say, an egg sandwich."
Douglas Adams
500,000,000,000,000 solar n just went through you
enpn
enpn
enpn
enpn
enpn
enpn
enpn
Why do we study them?
Probes of environments that we otherwise cannot see
Probes of objects too far away for anythingelse
Cosmological and astrophysical implications
Matter/Antimatter imbalance
Probes of environments that we otherwise cannot see
Probes of objects too far away for anythingelse
Cosmological and astrophysical implications
Matter/Antimatter imbalance
NEUTRINO
ASTROPHYSICS
Probes of environments that we otherwise cannot see
Probes of objects too far away for anythingelse
Cosmological and astrophysical implications
Matter/Antimatter imbalance
Universal Structure
m eV m eV
m eV m eV
Probes of environments that we otherwise cannot see
Probes of objects too far away for anythingelse
Cosmological and astrophysical implications
Matter/Antimatter imbalance
Why is there more matter than antimatter?
=
Why is there more matter than antimatter?
Sub-Atomic Talk Show Disasters
CP ViolationQ. Is there a difference betweenthe physics of matter and antimatter?
A.Yes there is.
We study this herewith an experimentcalled BaBar
“B0 / B0 mixing”
Q. Is there a difference betweenthe physics of matter and antimatter?
A.Yes there is.
We've never seen it in neutrinos, though.
Matter-Antimatter Asymmetry
n
n
nn
nn
n
n n
n
nn
“Leptogenesis”
How to study this?
Neutrino OscillationsTHE discovery in neutrinos of the last 20 years
l
nl
l
nl
A typical neutrino experiment
The Sun is Broken!!!
Ray Davis – Early 1970s
An atom a day
e Cl37 e- Ar37
1 Ar atom every two days
Only
Less than expected
Expected
Measured
Num
ber
n o
bse
rved
Neutrino OscillationsTHE discovery in neutrinos of the last 20 years
e
ne
m
nm
Neutrinos were changing flavour betweensun and detector!
Distance Travelled
Pro
b.
It is
ne
0
1
e
ne
m
nm
Eh?
Q. How can a ne spontaneously turn into a nm?
Eh?
Q. How can a ne spontaneously turn into a nm?A. The ne isn't a particle. It's three!
ne ≡ “that thing which was always produced/detected with an electron”
e
ne
Quantum Stuff
e
ne
en1
en2
en3
=or
or
60%
30%
10%
e
ne
m
nm
Original n1,n2,n3
mixture
Different n1,n2,n3
mixture
n1,n2,n3
travelsat differentspeeds
This can only happen if n1,n2,n3 have different massesOnly gives us differences in masses
Long journey
Why so important?The Standard Model of Particle Physicshas no explanation for a non-zero, but tiny, neutrino mass – so we are in “unknown physics” territory.
Neutrino masses link to GUT theories.
Has cosmological implications (mass balance,structure)
Posc e≠ Posc e
The T2K Experiment
University of Warwick
University of Sheffield
Imperial College, University of London
Oxford University
University of Liverpool
University of Lancaster
Queen Mary College, University of London
Rutherford-Appleton Laboratories
295 km
295 km
JPARC Facility
JPARC Facility
TARGET nm
295 km
Super-Kamiokande
nm
ne
Super-Kamiokande
Water Cerenkov
Electron-like : has a fuzzy ring
Muon-like : has a sharp edged ring andparticle stopped in detector.
Open Questions
How much do n1,n2 and n3 weigh?
Why are they so much lighter than all the other massive particles?
Are neutrinos the same as antineutrinos?
Are neutrinos the reason we are here at all?
‘‘...these kind of findings have implications that are not limited to the laboratory. They affect the whole of society — not only our economy, but our very view of life, our understanding of our relations with others, and our place in time.’’
Bill Clinton
P e=sin2 2sin21.27 m2 LE
L
sin2(2q)
Dm2 = m12-m2
2
Why do blue sky research?5% of jobs in UK are in physics-based sectorsGross added value from physics sectors was
estimated to be 70 billion pounds in 2005Synergy between PP projects and industry – industry
acquires added skills base for other applicationsTraining - 50% of PP PhDs go into other sectors
Radioisotope productionSensors for medical applicationsHigh level computing for biological modellingSpin off tools for other science (e.g. DIAMOND)Nuclear fusion researchMuon tomography in border securityAirport scannersRock ImagingCancer treatment using next gen cyclotrons
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