Download Neutrinos and their mass

Cecilia Lunardini
Institute for Nuclear Theory
University of Washington
http://www.int.washington.edu/users/lunardi/
The subatomic world: particles

We are made of atoms

Atoms are made of particles

Only some particles stay inside atoms

There is a whole “zoo” of free particles
We are particle investigators

Billions of particles
arrive here every
day from space!




Why are they here?
Where do they come
from?
What are they?
We capture them to
learn
The elusive neutrinos

They are invisible!


Three species :
No trace in optical
devices (telescopes, etc.)
Muon neutrino
Electron neutrino
Tau neutrino
They are everywhere!

about 300 in a teaspoon volume (1 cubic cm)

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from 1 second after the Big Bang
60 billions every second across your thumb’s nail (1
square cm) from the Sun
http://www-istp.gsfc.nasa.gov/istp/outreach/sunspotting.html
http://hubblesite.org/gallery/album/
How we thought they
behaved
The old theory of neutrino behavior
The mass-less neutrino

The mass


myself: 50 Kg (110 lb)
A particle (proton):
50 Kg
80 billions of billions of billions
proton

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Most particles have
some mass
The neutrino was
believed to have no
mass
neutrino

Mass-less particles have a very ordinary life


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Born (e.g., in the Sun)
Travel at speed of light
Get caught (absorbed) by matter (e.g., on Earth)
The puzzle of the missing
neutrinos
The neutrino trap

Experimenter Raymond
Davis decided to count
the neutrinos from the
Sun


To check the nuclear
reactions inside the Sun
He made a “neutrino
trap” made of cleaning
fluid (containing
Chlorine)

The trap worked
similarly to a colander:
The prediction

Theorist John Bahcall
calculated the number
of neutrinos expected
in the trap


Using knowledge of the
Sun
He found 9 “Solar
Units”
Photo from
http://www.sns.ias.edu/~jnb/JohnphotosHtml/
Something was wrong…
prediction

The counted neutrinos
were only 2 and ½
Solar Units !!

Only about 1/3 of the
prediction
How they actually do
behave
The new theory of neutrino behavior
Are we catching everyone?

The Sun only emits
neutrinos of the
electron species

The trap is unable to
catch the muon and
tau species!!
Are neutrinos “mutants”?

Theorist Bruno
Pontecorvo had an
idea…
“What if some
neutrinos mutate
from electron to
muon species on the
way?”
A lot of thinking was done…
Bruno
Pontecorvo
Alexei Smirnov
Stas Mikeyev
Lincoln Wolfenstein
See http://www.sns.ias.edu/~jnb/ for more photos
New theory: neutrinos with mass

Maybe the neutrinos have mass..

If so, the electron neutrino and the muon neutrino
could be like two sides of the same object
Muon neutrino
Electron neutrino
The “oscillations” idea

The neutrinos could rotate (“oscillate”)

They rotate while the travel
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Those neutrinos that arrive as muon are
missed!
You probably know what to
do….
Let’s make a better trap!

A “colander” that catches everyone:
The technological challenge

Thousands of tons of
water (and heavy
water) were needed
Sudbury Neutrino Observatory,
Sudbury, Canada
Photo: Kamioka Observatory, ICRR,
The University of Tokyo
And, finally… bingo!!

With an “all species”
trap the numbers
matched!
Neutrinos
counted
Neutrinos
predicted
½ Nobel prize soon came
December 2002
Raymond Davis
Masatoshi Koshiba
Photo: http://www.yasooo.com/en/people/color2/02.html
The fundamental meaning
Ok, the neutrinos have mass.
But, why is this interesting??
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Particles have mass if they can “hold hands”:
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Neutrinos are unable to hold hands

They are all left-armed
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Something exotic must happen…
Probably a new particle “helps” them!
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Indication of a new species!!
Neutrinos outside the
solar system
A gallery
Exploding stars: supernovae

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Gravitational energy is converted into neutrinos
Huge storm of neutrinos floods the Earth for 10-15 seconds
More powerful than all the stars of the universe together

In 1987 the star
Sanduleak (in the
Large Magellanic
Cloud) went supernova

Kamiokande (Japan)
and IMB (USA)
captured the neutrinos
The gamma ray emitters
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Exotic supernovae emit
powerful flashes of
gamma rays
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Mistaken for new weapon
of the Soviet Union….
Still mysterious
Neutrinos come
together with the
gamma rays

More energetic than any
human technology
The dark neutrinos

The mysterious
Dark Matter
contains neutrinos
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Primordial, from the
Big Bang
http://hubblesite.org/gallery/album/
The question of the mass

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Speed of light: C= 300000 Km/s ( … mph)
Human being: m=80 kg (~ 160 lb)  E =…
Mass and neutrino behavior

How much do neutrino weigh?
Even man-made neutrinos go
missing
The elusive neutrinos

They are invisible!


No trace in optical
devices (telescopes,
etc.)
Three “flavors”