Transcript Slide 1
Cosmic Gall
Neutrinos they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids down a drafty hall
Or photons through a sheet of glass.
They snub the most exquisite gas,
Ignore the most substantial wall,
Cold-shoulder steel and sounding brass,
Insult the stallion in his stall,
And, scorning barriers of class,
Infiltrate you and me! Like tall
And painless guillotines, they fall
Down through our heads into the grass.
At night, they enter at Nepal
And pierce the lover and his lass
From underneath the bed – you call
It wonderful; I call it crass.
John Updike (1960)
Wat vooraf ging …
The History before the history (1896-1930)
• Before the neutrino comes, the beta decay problem had to appear. And in order for that problem
to appear, radioactivity had to be discovered. Henri Becquerel in the year 1896, then Pierre and
Marie Curie were the first actors of this time. While Henri Becquerel discovered some strange
radiation coming from uranium salts, Pierre and Marie Curie isolated radium, a material much
more radioactive than uranium.
• In 1899, Rutherford shows that two types of radiation exist, that he calls alpha and beta. In
1900, Villard gives evidence for a third type of radiation coming from radium, that he calls
gamma radiation. In 1902, Pierre and Marie Curie show that beta radiation was nothing else
than electrons, while F. Soddy and E. Rutherford estimate that alpha, beta and gamma radiation
are different types of radioactivity.
• A crazy race begins to study in details those radiations coming from radioactive materials.
Around 1904, Rutherford shows that alpha radiation is made of something like helium atoms.
Finally, three types of radioactivity are definitely asserted:
alpha radioactivity: an Helium 4 nucleus (two protons and two neutrons) comes
out of the radioactive nucleus.
gamma radioactivity: a photon of great energy (few MeV) comes out of the
radioactive nucleus.
beta radioactivity: an electron comes out of the radioactive nucleus.
• The beta radiation (electron), the presumed only particle emitted, should have had a well fixed
energy. But, after different studies of this radiation made by Lise Meitner, Otto Hahn, Wilson
and von Baeyer, James Chadwick shows in 1914 that this is not the case: the electron energy
spectrum is continuous.
• Do we have to throw away the energy conservation principle, the sacred principle of scientists
always verified by experiment ?... Niels Bohr, among others, dares to believe it. We must wait
the year 1930 and Wolfgang Pauli in order the see an other solution.
,
(Uit : ‘History of the neutrinos’ http://wwwlapp.in2p3.fr/neutrinos/aneut.html)
Probleempje ?
Beta-verval :
Energieverdeling elektronen :
Voorstel : Pauli (1930)
Pauli's letter of the 4th of December 1930
Dear Radioactive Ladies and Gentlemen,
As the bearer of these lines, to whom I graciously ask you to listen, will explain
to you in more detail, how because of the "wrong" statistics of the N and Li6
nuclei and the continuous beta spectrum, I have hit upon a desperate remedy
to save the "exchange theorem" of statistics and the law of conservation of
energy. Namely, the possibility that there could exist in the nuclei electrically
neutral particles, that I wish to call neutrons, which have spin 1/2 and obey the
exclusion principle and which 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 masses. The continuous beta spectrum would then become
understandable by the assumption that in beta decay a neutron is emitted in
addition to the electron such that the sum of the energies of the neutron and
the electron is constant... I agree that my remedy could seem incredible
because one should have seen those neutrons much earlier if they really exist.
But only the one who dare can win and the difficult situation, due to the
continuous structure of the beta spectrum, is lighted by a remark of my
honoured predecessor, Mr Debye, who told me recently in Bruxelles: "Oh, It's
well better not to think to this at all, like new taxes". From now on, every
solution to the issue must be discussed. Thus, dear radioactive people, look
and judge. Unfortunately, I cannot appear in Tubingen personally since I am
indispensable here in Zurich because of a ball on the night of 6/7 December.
With my best regards to you, and also to Mr Back.
Your humble servant . W. Pauli, December 1930
Solvay conferentie, Brussel, oktober 1933
At Solvay conference in Bruxelles, in October 1933,
Pauli says, speaking about his particles:
"... their mass can not be very much more than the
electron mass. In order to distinguish them from
heavy neutrons, mister Fermi has proposed to name
them "neutrinos". It is possible that the proper mass
of neutrinos be zero... It seems to me plausible that
neutrinos have a spin 1/2... We know nothing about
the interaction of neutrinos with the other particles of
matter and with photons: the hypothesis that they
have a magnetic moment seems to me not funded at
all."
Fermi-theorie voor neutrino-interacties
W±, Z0 : zware ijkbosonen
1
m q2
2
W
Lage energie
processen
1
G
F
2
mW
2
Belangrijke benaderingen :
-lage-energie puntinteractie, er
worden geen ijkbosonen
uitgewisseld
(…. -> Glashow-Weinberg-Salam
’68)
-geen pariteitsbreking
( … ->Feynman & Gell-Mann ’56)
‘Zwakke’ interactie :koppelingsconstante klein
GF = 1.16639 10− 5 GeV − 2
heel
kleine werkzame doorsneden !
Neutrino-experimenten in de kinderschoenen
‘From Poltergeist to particle’ :
neutrino-detectie : Savannah River,
(Cowan&Reines 1956)
2 neutrino experiment : ontdekking
muon neutrino (Lederman, Schwartz,
Steinberger (1962) )
Homestake
(Davis, 1970) :
zonneneutrino’s
Waar ?
•
•
•
•
•
•
•
kosmologische neutrino’s
natuurlijke radio-acitiveit
reactorneutrino’s
supernovaneutrino’s
hoog-energetische kosmische
neutrino’s
zonneneutrino’s
atmosferische neutrino’s
Neutrino-oscillaties – Pontecorvo 1957
Bruno Pontecorvo
Voorwaarden voor oscillaties :
• mixing
• massaverschillen
Neutrino mixing en oscillaties
Oscillaties in materie – MSW effect
(Mikheyev-Smirnov-Wolfenstein ’78/’85)
de curves corresponderen
met verschillende waarden
van de vacuum mixing
hoek θ
A/Δm2
Neutrino-oscillaties experimenteel bekeken
•
Eerste positief signaal : Super-Kamiokande (1998) – atmosferisch neutrino’s
-Kamiokamijn
-waterdetector
-enkel elektronneutrino’s
http://neutrino.phys.washington.edu/~superk/
SK resultaten
azimuthale asymmetrie (PRL 811562-1567,1998)
Gedetecteerde/verwachte events
… maar waar is de rest naartoe ? …
…. SNO !
Bevestiging : SNO (Sudbury Neutrino Observatory,
Canada) ook gevoelig aan neutrale stroomreacties :
neutrino’s van alle flavors !
neutrale stroom – detectie neutronen : ook mu, tauneutrino’s !
geladen stroom
elektron scattering –
relatief kleine werkzame
doorsneden
http://www.sno.phy.queensu.ca/
8B
zonneutrino’s : dag/nacht asymmetrie
Oscillatieparameters
•
Maki-Nagawa-Sakata matrix !
•
•
oscillatielengte Lν
massakwadraat verschillen Δm2
Experimenteel :
… neutrinos over the world
Chooz
07-04
April 11, 2007
Media Contact:
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Photos and graphics of the MiniBooNE experiment are available at: http://www.fnal.gov/pub/presspass/images/BooNE-images.html
For immediate release
MiniBooNE opens the box
Results from Fermilab experiment resolve long-standing neutrino question
BATAVIA, Illinois-Scientists of the MiniBooNE1 experiment at the Department of Energy's Fermilab2 today (April 11) announced
their first findings. The MiniBooNE results resolve questions raised by observations of the LSND3 experiment in the 1990s that
appeared to contradict findings of other neutrino experiments worldwide. MiniBooNE researchers showed conclusively that the
LSND results could not be due to simple neutrino oscillation, a phenomenon in which one type of neutrino transforms into another
type and back again.
The announcement significantly clarifies the overall picture of how neutrinos behave.
Currently, three types or "flavors" of neutrinos are known to exist: electron neutrinos, muon neutrinos and tau neutrinos. In the last
10 years, several experiments have shown that neutrinos can oscillate from one flavor to another and back. The observations
made by the LSND collaboration also suggested the presence of neutrino oscillation, but in a neutrino mass region vastly different
from other experiments. Reconciling the LSND observations with the oscillation results of other neutrino experiments would have
required the presence of a fourth, or "sterile" type of neutrino, with properties different from the three standard neutrinos. The
existence of sterile neutrinos would throw serious doubt on the current structure of particle physics, known as the Standard Model
of Particles and Forces. Because of the far-reaching consequences of this interpretation, the LSND findings cried out for
independent verification.
The MiniBooNE collaboration ruled out the simple LSND oscillation interpretation by looking for signs of muon neutrinos oscillating
into electron neutrinos in the region indicated by the LSND observations. The collaboration found no appearance of electron
neutrinos as predicted by a simple two-neutrino oscillation scenario.
"It was very important to verify or refute the surprising LSND result," said Robin Staffin, DOE Associate Director of Science for High
Energy Physics. "We never know what nature has in store for us. The MiniBooNE experiment was an important one to do and is to
be complimented for a job well done."
The MiniBooNE experiment, approved in 1998, took data for the current analysis from 2002 until the end of 2005 using muon
neutrinos produced by the Booster accelerator at Fermilab. The MiniBooNE detector, located about 500 meters from the point at