Textbooks and references

1
Textbooks and references

• Current Aspects of Neutrino Physics, ed D.
  Caldwell, 2001
• Introduction to High Energy Physics, 4th edition,
  D.H.Perkins, 2000
• Spaceship Neutrino, author C. Sutton, 1992
• www pages
• http//hep.fuw.edu.pl/neutrino/
  http//www.ps.uci.edu/superk/
• http//neutrinooscillation.org/
  http//www.sns.ias.edu/jnb/
• http//hep.fuw.edu.pl/neutrino/
• http//wwwlapp.in2p3.fr/neutrinos/aneut.html

From neutrinos to cosmic sources, lecture 1,
2005
2
Exams
A list of subjects will be presented at the end
of the course The student will be asked to
report on a subject of the list.
For those who attended the course (not more than
3 skipped lectures)
The student chooses one subject of the list
before the exam and reports on it during the
exam.
For others
The student chooses 3 subjects of the list before
the exam and will be asked to report on one of
them during the exam.
From neutrinos to cosmic sources, lecture 1,
2005
3
From neutrinos to cosmic sources

• Neutrinos in Standard Model
• A brief history of neutrinos
• Sources of neutrinos
• Detectors
• Neutrino oscillations - fundamentals
• Atmospheric neutrinos
• Solar neutrinos
• Neutrinos from supernovae and other cosmic
  sources
• Neutrinos from accelerators
• Direct mass measurement
• Neutrinos in Universe
• Summary of experimental results
• Future neutrino studies

From neutrinos to cosmic sources, lecture 1,
2005
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The neutrino what is it?
F. Reines ....the most tiny quantity of
reality ever imagined by a human being
and yet
Our sun emits 2x1038 ?/sec Earth receives gt
4x1010 ?/sec/cm2 Universe 330 ?/cm3 (3 times
less than photons 109 times more than nucleons)
From neutrinos to cosmic sources, lecture 1,
2005
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How small is it?
neutrino
From neutrinos to cosmic sources, lecture 1,
2005
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The hadronic particles
Baryons
Lambda
Proton
Antiproton
Mesons
From neutrinos to cosmic sources, lecture 1,
2005
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Standard Model elementary particles
Charge
Charge
antiquarks
quarks
antileptons
leptons
From neutrinos to cosmic sources, lecture 1,
2005
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Spin
fermions ½ bosons 0, 1
Angular momentum
Left-handed states
Right-handed states
From neutrinos to cosmic sources, lecture 1,
2005
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Standard Model - interactions
We know from experiments
Strong interactions Electro-magnetic
interactions Weak interactions
Electro-weak interactions
From neutrinos to cosmic sources, lecture 1,
2005
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Carriers of Interactions
Fermions s1/2
Fermions s1/2
Bozons
gluons - g
Strong
quark
quark
photons g
Electro- magnet.
e-
e-
interactive bosons
Weak
n
quark
Feynman diagrams
From neutrinos to cosmic sources, lecture 1,
2005
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Weak interactions

W-
W

W
W-
From neutrinos to cosmic sources, lecture 1,
2005
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Weak Interactions CC and NC processes

• Charged Current reaction exchange of W boson
• Proposed by Fermi (1934)
• Responsible for neutron b decay

CC

• Neutral Current reaction exchange of Z boson
• Proposed by Weinberg-Salam
• Discovered with neutrinos

NC
From neutrinos to cosmic sources, lecture 1,
2005
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Some Weak Reactions Involving Neutrinos
Inverse beta decay
Electron capture
From neutrinos to cosmic sources, lecture 1,
2005
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Some Weak Decays
neutron decay
muon decay
W-
W

W bosons transform leptons INSIDE families
From neutrinos to cosmic sources, lecture 1,
2005
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Lepton number conservation
Included in Standard Model on the basis of
observations!
Eg. tau lepton decay
tau lepton number 1 0 0 1 muon
lepton number 0 1 -1 0
tau lepton number -1 0
0 -1 electron lepton number 0
-1 1 0
From neutrinos to cosmic sources, lecture 1,
2005
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Lepton number conservation
leptons antileptons Total L 1 -1
LinitialLfinal DL0
Le 1 e- ne DLe0 Lµ1 µ-
nµ DLµ0 Lt1 t- nt
DLt0
flavor lepton numbers are also conserved in
Standard Model

• NC (neutral current) interactions can occur for
  all flavors
• For a CC (charged current) interaction a
  neutrino has to produce a charged lepton and thus
  needs enough energy to produce its mass

From neutrinos to cosmic sources, lecture 1,
2005
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Baryon number conservation
Observation proton is stable!
Why?
Why
??
Proton lifetime
Thats why in Standard Model
quarks antiquarks Baryon number B
1/3 -1/3 DB0
A question what about neutron?
From neutrinos to cosmic sources, lecture 1,
2005
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Quarks in color
quarks
Antiquarks
up
down
strange
s
s
s
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Standard Model with colors
gtgtgt
20
Success of Standard Model
Those are all (known today) elementary particles
They are governed by the same UNIVERSAL laws
of physics
However ...........
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Standard Model is incomplete

• There are 26 constants of Nature too many!
• ( among others 15 masses) we would like to
  understand relations between them and unify
  all the interactions
• We dont understand the origin of masses - a
  search
• for Higgs (which may be responsible for
  providing
• elementary particles with their masses) will be
  carried in LHC
• We already know from studies of neutrinos that
  Standard Model has to be extended

From neutrinos to cosmic sources, lecture 1,
2005
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Some numbers - units
Unit of energy (mass) used in physics of
elementary particles
1 eV (elekronvolt) 1 eV energy of a particle of
elementary charge accelerated by difference of
potential of 1V
We often take energy units as mass units
(Emc2 c1)
Uncertainty principle
This leads to relation between units of energy
and length
23
Masses
Neutrino masses before 1998!
24
A brief history of neutrino
From neutrinos to cosmic sources, lecture 1,
2005
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Two body decay
m1
m2
M
Energy-momentum conservation gt
Energy of the decay products always the same
From neutrinos to cosmic sources, lecture 1,
2005
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1913-1930 Puzzle of b decay

• Continuous spectrum of b particles
• Energy is not conserved??
• Momentum is not conserved??

From neutrinos to cosmic sources, lecture 1,
2005
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Dec 1930 A Desperate Remedy
A
A
n
e

• I have done something very bad today by
  proposing a particle that cannot be detected it
  is something no theorist should ever do.
  W.Pauli

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Sir Arthur Eddington
In an ordinary way I might say that I do not
believe in neutrinos. Dare I say that
experimental physicists will not have sufficient
ingenuity to make neutrinos.
From neutrinos to cosmic sources, lecture 1,
2005
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How to catch a neutrino?
H. Bethe
ngt p e- ?
If one observes
? p gt n e
then how about an inverse beta decay
?
Probability of a reaction (for one neutrino)
cross section x number of targets/ area
Bethe calculated cross section 10-44 cm2
One needs either 1021 cm of water to absorb a
neutrino, or a lot of neutrinos.
From neutrinos to cosmic sources, lecture 1,
2005
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Reines and Cowan a Proposal (1953)
Reactor in Savannah River as a source of
neutrinos from decays of neutron-rich nuclei.
Detector 12 m underground
?-rays produced Compton electrons, which led to
scintillation light detected by
photomultipliers. A signal was selected by a
coincidence of prompt light from positrons and
delayed light (by 15 µsec) from the neutron
absorption by a cadmium nucleus.
Liquid scintillator
Water, Cadmium chloride
In 1956 a telegram to Pauli We are happy to
inform you that we have definitely detected
neutrinos... 1995 Nobel Prize for Reines
Liquid scintillator
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But weak interactions bringa new mystery
Left- right asymmetry
From neutrinos to cosmic sources, lecture 1,
2005
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Left-right symmetry in beta decay
1957
Mrs Wu et al. measured electrons from beta decays
of Co60 nuclei whose spins were oriented (for a
few minutes) in a magnetic field. It appeared
that there were more electrons in the direction
opposite to Co60 spins. Electrons are not
symmetrically ejected over and under the plane
perpendicular to the nuclear spins!
From neutrinos to cosmic sources, lecture 1,
2005
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Left-right symmetry in beta decay (cont.)
Starting with the experiment by Wu et al. the
measurements showed that the angular distribution
of
positrons
electrons
where ? is the angle between the electron
direction and its spin and v is the electron
velocity
Thus electrons prefer backward
positrons prefer forward emission with respect
to their spins
direction of motion
direction of spin
Electrons are mostly left-handed (LH) and
positrons right-handed (RH)
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Left-right symmetry in beta decay (cont.)
We can define Longitudinal polarization
For massless neutrinos one can expect
or
i.e. neutrino polarization P is
Left-handed or right-handed?
From neutrinos to cosmic sources, lecture 1,
2005
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Measurement of neutrino polarization(or helicity)
From Pauli hypothesis neutrino spin1/2 but what
is its polarization ?
An experiment by Goldhaber et al. (1958) see a
very good description by Grzegorz Brona (MSc).
Conclusion Neutrinos accompanying positrons are
left-handed, while those accompanying electrons
are right-handed Hence by convention leptons
are left-handed anti-leptons are
right-handed electrons positrons neutrinos
anti-neutrinos
36
Goldhabers experiment
all figures thanks to Mr Grzegorz Brona (MSc)
K orbit electron
Total angular momentum of the initial state is
spin of a captured electron.
final states
i.e. spins are opposite
i.e. the recoiling nucleus has the same
polarization sense (or handedness) as the
neutrino - along or against velocity
vector. i.e. RH or LH
spin
velocity
spin
velocity
From neutrinos to cosmic sources, lecture 1,
2005
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Goldhabers experiment (cont.)
RH LH
gamma has to carry away the angular momentum of
the excited nucleus!
Next
Lets consider the LH case spins against
velocities)
if photon emitted forward
if photon emitted backward
In the same way one can show that
In RH case
spins
forward g has to be RH
Hence polarization of forward g is the same as
that of neutrinos!!
velocity
i.e. forward g has to be LH
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Goldhabers experiment (cont.)

• Hence we need to
• select forward gammas
• measure their polarization

Another great idea use resonant scattering
possible only with a forward gamma because it has
slightly higher energy than the
excitation energy (thus allowing for some recoil
energy of the nucleus)
From neutrinos to cosmic sources, lecture 1,
2005
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Schematic view of Goldhaber experiment
Experiment steps

• Electron capture by 152Eu
• Decay of 152Sm with emission of gammas
• Measurement of gamma
• polarization by scattering
• on polarized electrons in
• iron (by mgt field)
• Absorption and reemition of ? in 152Sm
  selects only photons emitted forward

From neutrinos to cosmic sources, lecture 1,
2005
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Result of the experiment
or is for magnetic field direction (up
or down) which polarizes spins of iron electrons
which act as polarimeter for gamma polarization
From neutrinos to cosmic sources, lecture 1,
2005
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Neutrinos are Left-handed
i.e its spin projection on a direction of
motion (helicity) is negative
From neutrinos to cosmic sources, lecture 1,
2005