Transcript PHY313 - CEI544 The Mystery of Matter From Quarks to the

PHY313 - CEI544
The Mystery of Matter
From Quarks to the Cosmos
Spring 2005
Peter Paul/Norbert Pietralla
Office Physics D-143
www.physics.sunysb.edu PHY313
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Information about the Trip to BNL
• When and where: Thursday March 31, 2005 at 5:20 pm pickup by bus (free)
in the Physics Parking lot. We will drive to BNL and arrive around 6pm (20
miles). We will visit The Relativistic Heavy Ion Collider (RHIC) and its two
large experiments, Phenix and Star. Experts will be on hand to explain
research and equipment. We will return by about 7:30 pm to arrive back at
Stony Brook by 8pm.
• What are the formalities? You need to sign up either in class or to my e-mail
address [email protected]. by this Friday night. You must bring along a valid
picture ID. That’s all! The guard will go through the bus and check the picture
ID’s.
• What about private cars: You will still have to sign up and must bring a
picture ID (your drivers license) to the event. You will park your car at the lab
gate, join the bus for the tour on-site and then be driven back to your car.
• There is NO radiation hazard on site. I hope many or even most will sign up
for a unique opportunity.
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What have we learned last time I
• The elements up to the tightest bound
one, 56Fe, are formed during the
burning process in the star as it uses its
primordial fuel, 75% hydrogen (protons)
and 25% Helium.
• In the first step the star burns four
protons into 4He. Once sufficed 4He is
produced, 3 4He will combine to yield
12C. This process produces more heat.
• In the next step the star uses 12C and
the available hydrogen to go through the
CNO cycle which produces the elements
between 12C and 16O. This heats the
star up further.
• One there is sufficient 16O around the
star will produce still heavier elements
by using available H and 4He to fuse
with the 16O.
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• This process continues until the elements
that are produced reach the peak of the
nuclear binding energy, at Fe/Ni.
• Then the star cools (Red Giant). Gravitation takes over compressing the star. The
heaviest elements accumulate at the core
in layers of density. Compression reheats
the star & it explodes as a Supernova.
• Nuclear reactions occurring during this
violent phase produce many neutrons.
These are rapidly captured into the Fe/Ni
core to produce the heavier nuclei (rprocess). Beta decay changing n  p
inside the nuclei “moves” the neutronrich nuclei toward the valley of stability.
• The final explosive phase spews these
heavy elements into the interstellar
medium. They are then incorporated into
new stellar objects
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What have we learned last time II
• The known “zoo” of strongly interacting
particles (hadrons) was found naturally
divided into very heavy particles
(Baryons) and medium heavy particles
(mesons).
• It became clear from the formation and
decay of these particles that several
hidden quantum numbers play a role, in
addition to the conservation of electric
charge.
• Strangeness S and Baryon number B are
always conserved in reactions that
involve the strong interaction.
• A concept of elemental building blocks,
called up, down and strange quarks,
could explain all aspects of the
construction of the hadrons.
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• The quarks have electric changes in
units of 1/3 of the electron charge,
Baryon number 1/3. and spin-1/2 .
• All known Baryons could be
constructed combining 3 quarks; all
mesons could be constructed with one
quark and an anti-quark.
• The discovery of the  particle, a combination of 3 s quarks, showed that there
was reality behind the quark concept.
• Deep inelastic electron scattering from
the proton showed that there were hard
objects inside the proton. These are
called partons, but are in fact quarks.
• Later, three heavier quarks, the charm,
top and bottom quarks were discovered.
• The total of 6 quarks and 6 antiquarks
group into three “families”.
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The three quark families
• Today we know 3 families of quarks, and 3 antiquark families.
Spin
Charge
First family
Second family
Third family
1/2
+3/2
up
(3 MeV)
charm
(1300 MeV)
top
(175,000 MeV)
1/2
-1/2
down
(6 MeV)
strange
(100 MeV)
bottom
(4,300 MeV)
Note that the neutron and proton and the light mesons
are all build up of the lightest quarks, the u and d.
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html
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The dynamics of quarks
• In addition to their regular quantum
numbers quarks must have other
property that differentiates them from
each other. This property is called Color.
(See e.g. the proton = uud
• There are 3 colors : Red, Green and
Blue (these are just stand-in names).
Thus the proton looks like this = uud or
any other color combination)
• The colored Quarks interact with each
other through the exchange of gluons.
These gluons exchange color between
the quarks (Color interaction).
• There are 9 color combinations but only
8 gluons.
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greenanti-green
greenanti-red
greenanti-blue
redanti-red
redanti-blue
redanti-green
blueanti-blue
blueanti-red
blueanti-green
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Quark Confinement
• The color interaction between quarks
binds the quarks such that no single
quark can ever be free.
• This is different from two charged
bodies bound by the Coulomb force,
but similar to the binding of a
magnetic north-pole and a south-pole
• Thus any quark that emerges forma
proton will “dress itself with other
quarks or anti-quarks and emerge as a
jet.
• The binding force between quarks
relatively weak when they are close
together but grows stronger as they are
pulled apart.
• At close distances they can almost be
treated as free: Asymptotic freedom
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Hidden color, hidden charm
• The J/ particle is made up of a c quark
•All quarks carry one of 3 colors so
and an antiquark. This combination
that the Pauli principle is satisfied.
cancels out the “charmed” character of
However, any real elementary
this particle. The charm is hidden inside.
particle, like p and n, cannot have any
color, or lese we would have seen it in • Trying to break up the bond between the
c and cbar does not free them, but as
earlier experiments. The color is
the bond breaks the released energy
hidden inside. The total object must
produces non-charmed quarks. Thus the
be “white” i.e. colorless.
c and cbar quarks in the final products
•This requirement puts a restriction
also on the gluons and is responsible
for the fact that there are only 8
gluons, the 9th would be colorless and
could not effect any color
transformation.
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no longer cancel each other and the
charm character is now apparent
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Neutrinos: the last Frontier
• Neutrinos are today the least
understood particles: They carry no
electric charge and they only feel
the weak interaction.
• The weak force is much weaker than
the EM force
• EM 
e2
1

• Weak
c 137
g2
 0.6  106
c
• Thus the weak force is about weaker
by a factor of 10,000
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• Neutrinos have spin ½, similar to
electrons and muons.
• Neutrinos are part of the Lepton
(light particle) Family
• There are 3 neutrino species:
– e, μ , 
Species
Symbol
Mass
electrons
e+, e-
511 keV
muons
μ +, μ -
105.7 MeV
tau
+, -
1,500 MeV
neutrinos
e, μ
Very small
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Types of weak decays
•
•
•
•
•
•
•
n  p+ + e- + vebar
+  0 + e+ + 
+  μ + e+ + 
μ+ e+ + 
-  
-  n + e + 
K+  0 + e+
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• The rules of the game are clear:
1. Charge is conserved in the decay.
2. Baryon number is conserved.
3. Strangeness is conserved.
4. Lepton number is conserved for
each lepton family.
• The latter means that on each side.
of the decay we must have the same
number of leptons. Anti-leptons
cancel out leptons.
• The positron is the anti-particle to
the electron. The μ+ is the
antiparticle to the μ-.
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History of the neutrino
•
•
•
•
1930
1956
1965
1966
• 1967
• 1970
• 1976
• 2000
• 2000
• 2004
W. Pauli stipulates existence the neutrino
F. Reines detects the first neutrinos from a nuclear reactor
Schwartz discovers the muon neutrino
It is proven by Goldhaber and Sunyar that muon and electron
neutrinos are different
Ray Davis starts to look for neutrinos from the sun
Solar neutrinos show a large deficiency, only about 25 to 45% of
expected neutrino flux is detected.
The first direct observations of neutrinos from a supernova explosion
The tau neutrino is detected
It is shown that solar electron neutrinos change their “flavor” as they
travel from sun to earth, thus explaining the flux discrepancy
The Kamiokande experiment shows muon neutrinos also change
flavor.
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How do we measure the barely measurable
• We need a huge mass of detection
medium to give the neutrinos ample
opportunity to interact.
• The detectors need to be deep
underground to shield against cosmic
muons. The neutrinos will go through
all the rock, even through the earth from
the other side
• The first experiment was a chemical
experiment done by Ray Davis who was
looking for solar neutrinos in tye
Homestake mine in SD
• The second experiment was done with a
huge Cerenkov water detector in the
Kamiokande mine in Japan
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Nobel Prizes in 2000
The first detection of solar neutrinos by Ray Davis’s chlorine
experiment, and the subsequent confirmation by Kamiokande
using real-time directional information and the first detection
of supernova neutrinos opened up a new exciting field of
neutrino astronomy. For these great achievements Ray Davis
and Masatoshi Koshiba shared a Nobel Prize with Riccardo
Giaconni who is the founding father of x-ray astronomy.
Ray Davis
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Masatoshi Koshiba
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Riccardo Giocconi
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Big Underground Detectors
Ray Davis experiment detected
the first solar neutrinos using
Chlorine Cl at Homestake
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Kamiokande detected the first
neutrinos from a supernova using
water (3,000 tons).
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neutrinos
HowDetecting
do we detect neutrinos?
Ray Davis Homestake Experiment:
615 tons
Counts the number of 37Ar
using a chemical methods
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Kamiokande,Super-Kamiokande:
3,000 tons , 50,000 tons
- Detect the recoil electron which is kicked by
a solar neutrino out of a water molecule.
- Can measure the energy and direction of the
recoil electron.
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Physicists having fun in a boat in Super-Kamiokande
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Physicist checking installed photomultipliers
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Atmospheric Neutrinos How does a water Cherenkov detector work?
Water Cherenkov Detector: Kamiokande,IMB,Super-Kamiokande,SNO
Water is cheap and easy to handle!
When the speed of a charged
particle exceeds that of light
IN WATER, electric shock
waves in form of light are
generated similar to sonic boom
sound by super-sonic jet plane .
These light waves form a cone
and are detected as a ring by
a plane equipped by photosensors.
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An event produced by an atmospheric
muon neutrino
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Differentiating atmospheric muon and electron neutrinos
Simulated events
muon-like ring
Major interactions:
e + n -> p + em + n -> p + m
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invisible
electron-like ring
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Neutrinos from a Supernova
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A Supernova evolves into a black hole
Will we be
able to see
’s from a
black hole?
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Neutrinos from this SN were
observed by Kamiokande and IMB
12 events
8 events
SN 1987A, Feb.23, 1987 in Large Magellanic Cloud
At about 170,000 light years away
Before
After
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Supernova How do we know detected neutrinos are from a supernova?
Birth of a supernova witnessed with neutrinos
Number of photomultipliers fired
A few hours before optical observation
Kamiokande
Background level
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Taken by Hubble Space Telescope
( 1990)
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Can we How
see does
thethe
neutrinos
from the sun?
Sun shine?
• The sun produces very energetic neutrinos (> 1 MeV) in
the processes that go from 4He to 8B
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Kamiokande
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Seeing the sun 4000 ft underground
Image of Sun by Super-Kamiokande
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Solar Neutrinos
Seeing the Earth’s Orbit Underground!
Distance Earth-Sun
Summer: 4 Jul. 156 million km
Winter : 3 Jan. 146 million km
Solar neutrino flux ~ (1/distance)2
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Note: Flux less than half of
expected (deficit)!!! 27
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The solar neutrino problem in 1994
Ray Davis
Observation over many years shows that only
about 25% of the expected number is observed!
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2002 Nobel Prize
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Discovery of Muon Neutrinos
•
http://hyperphysics.pastr.gsu.edu/hbase/particles
/neutrino2.html
Beginning in 1965 Schwartz et al. at
BNL bombarded a Be target with 15
GeV protons from the AGS. They
produced copious  which decayed
into μ and neutrinos. The μ was
different from the e
  m  m


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Discovery of the -lepton in 1975
• The data were taken at the e+-ecolliding beam target. The reaction
would be
e+ + e-  + +  • Note that this reaction satisfies all
lepton conservation laws since e+
and + are both antiparticles.
• The search was for
events where only one
electron and one muon would
be detected
• The  has a mass
3000 x that of the
electron!
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Martin Perl
receiving the
Nobel Prize
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Discovery of the -neutrino
• In 2000 the -neutrino was
finally discovered at
Fermilab. A proton beam
produced a intense shower
of neutrinos that should
contain -neutrino.
• The dector is layers of iron
separated by layers of plastic
scintillator
• One in a million-million (10
-12) neutrinos would
intercat in the iron plates and
produce a -lepton which
decayed leaving characteristic tracks. Four such tracks
were isolated.
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This completes the lepton family below 1 TeV
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The weak interaction: W and Z bosons
• The force carriers of the weak interaction are the W+- (for “weak”) and the
Z bosons.
• The carriers of the weak force are very
heavy. That is the reason for the very
short range of the force. The mass of
the W is 80.4 GeV; the mass of the Z0
is 91.2 MeV.
• The W+ is the antiparticle to the W-;
the Z0 is its own antiparticle
• Note on the right how the W is able to
change the quarks from one flavor to
another.
• Example: The beta decay of 60Co
60
Co28
Ni  e  e
60
27
• Inside the Co nucleus one of its 33
neutrons changes into a proton:
n  p  e  e
• Looking inside the neutron, at the
quark level the reaction is the change
of a d-quark into a u-quark:
d  u W 
W   e   e
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Neutron beta decay at the quark level
Fundamental Force
An example of weak interaction
-
Free neutron decay: n -> p + e-  e
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How many neutrino families are there?
 
e e Z  f f
At the e+-e- collider at SLAC the Z boson was
produced in the reaction below where ffbar are
any ½ spin particles. The mass energy was
determined with high precision. The width
relates to the number of neutrino families that
are emitted in the decay. More families shorten
the life time and increase the width. There is
excellent agreement with 3 families.
0
(MZ=91.1882±0.0022 GeV)
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The BuildingWhat
Blocks
of the Standard Model
is matter made of?
• With the assurance that we have seen all
3 families of leptons, and having 3
families of quarks, a unified picture
emerges:
1. There are the 6 basic weakly interacting
particles (leptons). They all have spin 1/2
hbar.
2. There are 6 building blocks for strongly
interacting particles (hadrons).
3. There are 4 basic force carriers (Bosons).
They all have spin 1 hbar. There are 8
gluons, 2 W’s one Z and one 
4. This scheme unifies the EM and the weak
interaction: The Z and the  have the
same heritage but split into a heavy and a
light twin.
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Unification of Forces
Grand Unified Theories (GUTs)
Strong
Electric
Electromagnetic
Magnetic
GUTs
19th c.
Electroweak
Weak
20th c.
21st c.?
GUTs predict:
hard
Proton must decay
Neutrino must have mass
Gravitational
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Seventh Homework Set, due March 17, 2005
1. Quarks have spin ½, like electrons, and thus must obey the Pauli principle. What
property of quarks makes it possible to put two u quarks into a proton?
2. Gluons are the force carriers of the strong interaction. How many of them are
there, how do they differ from each other, and what is their mass?
3. What are the names and properties of the three heavy quarks that have been
detected experimentally.
4. How can we detect the elusive neutrinos: Give two characteristics of a
successful detector.
5. What neutrinos can we expect to see from the sun? Why is the prediction of the
neutrino flux that we expect so solid?
6. How many different neutrinos are there and what are the force carriers of the
weak interaction?
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Do neutrinos have mass?
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Long baseline neutrino oscillation
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The SNO experiment
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Particle Physics
What is neutrino oscillation?
Neutrino Oscillation
There are three kinds of neutrinos: e
m

(flavours)
If neutrinos have mass, they can change their identities (flavours)
e
m

oscillation
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Atmospheric Neutrinos
Super-Kamiokande: The successor of highly successful Kamiokande
40 m height
50,000 tons of pure water equipped with 12,000 50 cm photomultipliers
and 2,800 20 cm photomultipliers (PMTs).
1,000 m deep
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Atmospheric Neutrinos
Source of atmospheric neutrinos
Earth’s atmosphere is constantly
bombarded by cosmic rays.
Energetic cosmic rays (mostly
protons) interact with atoms in
the air.
These interactions produce many
particles-air showers.
Neutrinos are produced in decays
of pions and muons.
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Atmospheric Neutrinos
Evidence of neutrino oscillation/mass
with oscillation
without oscillation
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low energy e
low energy m
high energy e
high energy m
First
crack
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in the Standard Model!!!
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Solar Neutrinos How do we see neutrino oscillation with solar neutrinos?
Flux: measured/expected
Homestake
: 0.27
Neutrino deficit!!!
Kamiokande
: 0.44 Not enough neutrinos
Super-Kamiokande : 0.47
Should be 1
Neutrino oscillations
m is not visible to all
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Solar Neutrinos How can we prove it’s neutrino oscillation?
Neutral current
SNO
D2O instead
Peter experiment
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Solar Neutrinos How does the neutral current confirm neutrino oscillation?
Elastic scattering
-This reaction is available only for  e .
Neutral current interaction
-This reaction is flavour blind and is
available for all kinds of neutrinos.
-Available for both water and heavy
- Available
water.
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Solar Neutrinos
Confirmation of solar neutrino oscillation by SNO
m is visible only to SNO
But NOT to Homestake,
Kamiokande or SuperKamiokande.
Even if solar neutrino e
changes its flavour to m
or  total flux of solar
neutrino can be measured
by SNO
Solar flux measured: 6.4+-1.6 x 106 cm-2 s-1
Good agreement!
Solar flux predicted : 5.1+-1.0 x 106 cm-2 s-1
Solar neutrinos oscillate!!!!
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Supernova Why is detection of supernova neutrinos important?
We learn:
- Properties of neutrinos: its mass (or limit of it), magnetic
moment,electric charge, etc.
- Details of supernova explosion: how a star dies
- How a neutron star or a black hole is formed if it happens
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