particle physics past and future h.arfaei ipm 26/2/86
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Particle Physics
Past and FutureH.Arfaei
IPM26/2/86
• Ancient view : Earth, Air, Fire,
Water• By 1900, nearly 100
elements• By 1936, back to three
particles: proton, neutron, electron
• Ancient Principles• Symmetry • Geometrical pictures • Theory for the four elements!• Platonic Polyhedra• Search for the fifth element!
• Still Valid
History of Constituents of Matter
AD
mx 10101
mx 15101
mx 15107.0
mx 18107.0
Thomson (1897): Discovers electron
• From the particle garden to the jungle :In 1937, Anderson discovered the muon μ. The μ proved to be some sort
of heavier electron (lepton).
I.I Rabi, Nobel 1944
Who ordered THAT ?
The muon decays into through β decay:
μ νμ + e- +¯νe
In 1947, pions (mesons) were detected in cosmic rays. They were thought of as Yukawa’s mediator particle for the strong interaction. The Universe was in order again, except for the muon, which played no visible role.
In December 1947, new mesons were found : the kaons. The place got crowded again…
With the use of particle accelerators in the 50’s, many new particles were discovered. Some of them were « strange » because they were produced by the strong force but decayed through the weak force.
• 1932 : Chadwick discovers the neutron, which is not stable when isolated, and decays as follows : n p + e- (+ ¯νe) . The proton, electron and neutron account for all the atoms of all the elements in the Universe.
This was the “simplest” elementary particle set ever described. A small number of particles, a small number of interactions. LEPTON (leptos = light) : e-
BARYONS (baryos = heavy) : p , n
2. Which particles were considered elementary throughout History?
• Antiquity : Four elements. Unsuccessful attempt at an atomistic theory during the 5th century BC (Democritus).
• 18th century : Lavoisier and Dalton verify experimentally the validity of the atomic structure.
• 1868 : Mendeleev proposes his chart of elements, containing the 63 atoms known at the time. The “empty cases” he left were soon filed. By 1896, 77 atoms have been discovered, and are considered elementary.
• 1897 : Discovery of the first subatomic particle by J.J Thompson : the electron. The search for its positive counterpart begins, until…
• 1911 : Rutherford discovers the nucleus. Transmutation reactions showed that the hydrogen nucleus played a specific role (4
2He + 147N --> 18
9F --> 178O + 1
1p) . Rutherford named it proton (protos = first)
• Moreover, some rules seemed to be missing to predict if a decay could occur or not :
• Why is π- + p+ K+ + Σ- possible ,• When π- + p+ K0 + n is impossible ?
• In 1953, Gell-Mann and Nishijima came with a simple and elegant idea. Each particle was to be assigned a «strangeness », and the overall strangeness had to be conserved during a collision (not through decay).
• There were then THREE laws of conservations for reactions :
• Charge• Baryonic number (proton like particles)• Strangeness
Ancient times People think that earth, air, fire, and water are the fundamental elements.
1802 Dalton’s Atomic theory began forming.
1897 J. J. Thompson discovered the electron.
1911 Rutherford discovered positive nucleus.
1930 Pauli invented the neutrino particle.
1932 James Chadwick discovered the neutron.
1937 The muon was discovered by J. C. Street and E. C. Stevenson.
1956 First discovery of the neutrino by an experiment: the electron neutrino.
1962 Discovery of an other type of neutrino: the muon neutrino.
1969 Friedman, Kendall, and Taylor found the first evidence of quarks.
1974 The charmed quark was observed.
1976 The tau lepton was discovered at SPEAR.
1977 Experimenters found proof of the bottom quark.
1983 Carlo Rubbia and Simon Van der Meer discovered the W and Z bosons.
1991 LEP experiments show that there are only three light neutrinos.
1995 The top quark was found at Fermilab.
1998 Neutrino oscillations may have been seen in LSND and Super-Kamiokande.
2000 The tau neutrino was observed at Fermilab.
2003 A Five-Quark State has been discovered.
A short summary of events
p
چه جنگلی•
1. What makes a particle “elementary” ?
• A particle is elementary if it has no inner structure (i.e not “made” of some even smaller entities).
Orders of magnitude for distances
3. New particles again, but some symmetry and order gained...
• Quark dynamics was understood later, and brought 8 photon like mediator particles : gluons.
• After a few years of quiet, the November Revolution (1974) brought a new quark (charm quark) through the discovery of the J/ψ meson (c ¯c).
• In 1975, the Τ lepton was discovered.• In 1977, the Υ meson (b ¯b) was
discovered, introducing the bottom quark.
• In 1983, the mediators for the weak interaction were discovered at CERN : W+- and Z0
• The symmetry of six quarks and six leptons was completed with the top quark in 1995.
Unifying Principle
• Symmetry, Gauge Invariance
Generalization from EM
and Breaking the symmetry!!!
by Giving nonzero VEV to Higgs Field
• Responsible for mass of the
Quarks, Leptons and gauge Bosons
The Four Fundamental Forces
Symmetry Breaking
1. The Nobel Prize winners
1979 Nobel Prize-- GLASHOW, SALAM and WEINBERG
the theory of the unified weak and electromagnetic interaction.
1984 Nobel Prize-- RUBBIA and VAN DER MEER the discovery of the field particles W and Z, communicators of weak interaction.
Present activitiesnews in 2006 and 2007
sky Dark matter accelerators CP violation, mixings WZ pair production Single top events Proton and strangeness Pentaquark Quark Gluon Plasma
underground activities Neutrino vanishing ! Opera
• Single top event,
What next?• Theory Supersymmetry, Extra dimensions, String Theory, Unification with gravity.. M-theory……
•Experiment
LHC
3. Science needs advanced technology and vice versa
How to Obtain Particles Accelerator
Modern Detectors Bubble Chamber
The LHC tunnel
The large hadron collider
• The large hadron collider (LHC) uses the same tunnel as LEP, at Cern in Geneva
• The machine is a 14 TeV proton-proton collider, so each stored beam will have an energy of 7 TeV
• It is being built now, and shall start operation sometime in 2007
• There are a number of experiments
What to look for?
HIGGS SUSY Particles ( Candidate for Dark Matter?) Hierarchy problem
Extra dimensions CP violation Quark gluon Plasma
What to look for?
• Higgs
• Top quark Physics
• Susy particles (candidates for dark matter?)
• Hierarchy problem
• Extra dimensions
• CP violation, Flavor Mixing
• Quark gluon Plasma
• UNEXPECTED NEW PHYSICS checkmating the Theorists!
Maybe
HIGGS
expected around 115 GEV
Guides us to the origin of mass
• Decays in to two Z bosons that decay into pair of Muons
• If it is not seen up to 1TEV we have to find a way out, though life!
Susy particles
• Candidate for Dark matter
May be seen as missing mass
• Hierarchy problem
• If susy is seen we may have a justification for protection of different scales
• Extra dimensions
• Predicts strong gravity at short distance
• And tower of massive particles, maybe not very massive!
• Quark gluon Plasma
• The Observations from LHC will tell us what to do next, ILC
• Particle Physics is expecting 20 years of excitement
Spinn offs from Particle Physics• Modern Technology,• Superconducting Technology• Strong and precise magnets• Fast detectors• Fast programming
• GRID COMPUTATION
• Peace and Collaboration among nations
The International Linear Collider
• The International Linear Collider (ILC) is a proposed machine, to complement the LHC
• It shall collider electron and positrons together at a centre-of-mass energy of 1 TeV
• The anticipated cost is a cool $8,000,000,000!• Currently, a detailed physics case and
accelerator design is being formulated, in an attempt to get someone to pay for it!
Implications for Cosmology
CERN
These are some of the early creators of modern physics, at the 7th Solvay Physics Congress in Brussels, 1933. Even though Max Born said at the
time, "Physics as we know it will be over in six months," virtually all of
particle physics followed this meeting.JJ Thomson
The Beginning of Particle
PhysicsErnestWalton
As an outsider, you may refer to us as "CERN, the European Laboratory for Particle Physics near Geneva", but for legal reasons we will always communicate with you as the "European Organization for Nuclear Research".
What is CERN?
About CERN's Name from the Web
CERN staff must use the official name in all CERN published materials.
CERN does pure scientific research into the laws of nature. We are not involved with nuclear weapons.
The CERN convention states:
The Organization shall provide for collaboration among European States in nuclear research of a pure scientific and fundamental character, and in research essentially related thereto. The Organization shall have no concern with work for military requirements and the results of its experimental and theoretical work shall be published or otherwise made generally available.
What is CERN?
Data Processing
"DataGrid" is a project funded by European Union. The objective is to enable next generation scientific exploration which requires intensive computation and analysis of shared large-scale databases, from hundreds of TeraBytes to PetaBytes, across widely distributed scientific communities.
The DataGrid Project
The EU-DataGrid initiative is led by CERN
The "Web" as it is affectionately called, was originally conceived and developed for the large high-energy physics collaborations which have a demand for instantaneous information sharing between physicists working in different universities and institutes all over the world. Now it has millions of academic and commercial users.
The World Wide Web
1990:Tim Berners-Lee, a CERN computer scientist invented the World Wide Web.
Tim together with Robert Cailliau, another CERN computer scientist, wrote the first WWW client (a browser-editor running under NeXTStep) and the first WWW server along with most of the communications software, defining URLs, HTTP and HTML.
In December 1993 WWW Tim received the IMA award and in 1995 Tim and Robert shared the Association for Computing (ACM) Software System Award for developing the World-Wide Web.
WWW
1 The Particles and their Properties.
There are two types of particles that are thought to be fundamental. That
is, they cannot be broken down into any smaller constituent particles. These two types of particles are the leptons and the quarks.
However, these can, under the right conditions, be converted into energy, or be formed from bundles of energy. Also, the heavier ones can decay into
lighter ones, with the release of some of their energy.
As the regions of the universe near us are now in a much lower-energy state than they were shortly after the big bang, only the lightest particles in
each family are now very commonly observed.
Others can be re-created by high-energy collisions, such as those produced in particle accelerators.
The most familiar member of this group is the electron, but there are also similar, heavier (and hence more energetic) particles called the muon and the tau.
1.1 The Leptons
For each one of these, there is a smaller “partner” called a neutrino – the electron neutrino, the muon neutrino and the tau neutrino.
Each of these 6 also has an antiparticle, for example, the anti-electron or positron.
The leptons are all capable of independent existence.
1.2 Properties of the Leptons
The electron, muon and tau all have mass. The neutrinos have no mass, according to the Standard Model. However, there is some evidence that neutrinos do have an actual, very small mass.
The electron, muon and tau all have electric charges of –1, and their anti-particles have electric charges of +1. The neutrinos have no electric charge.
All of the leptons have another property called “spin”. Their spins can be +½ or -½.
Table of Leptons
Flavour Mass (GeV/c2)
Electric Charge
First Generation
υ e electron
neutrino
e electron
< 1 x 10-8
0.000511
0
-1
Second Generation
υμ muon
neutrino
μ muon
< 0.0002
0.106
0
-1Third Generation
υτ tau
neutrino
τ tau
< 0.02
1.7771
0
-1
The anti-lepton symbols are: e+, μ+, τ+, υ e, υμ, υτ.
1.3 The Quarks
The quarks are not capable of independent existence, and are found only as groups, making up larger particles (called “bound states”).
The quarks have mass and electric charge. The electric charges are either +⅔ or -⅓ for quarks, and -⅔ or +⅓ for the matching anti-quarks.
There are 6 quarks, called up, down, charm, strange, bottom and top. The “everyday” quarks are the up and down quarks. For each quark there is an anti-quark.
They also have spin of ±½. There is also another property called “colour” charge, which comes in 3 varieties, red, green and blue. The anti-quarks have anti-colours: anti-red, anti-green and anti-blue.
Table of Quarks
Flavour Mass (GeV/c2)
Electric Charge
First Generation
u upd down
0.0030.006
+⅔-⅓
Second Generation
c charms strange
1.30.1
+⅔-⅓
Third Generation
t topb bottom
1754.3
+⅔-⅓
The symbols for the anti-quarks are: u, d, c, s, t, b.
2 Rules That The Particles Follow
There are also other rules, for example about spin, which must also be obeyed.
This relates particularly to the grouping together of quarks.
The “bound states” must be colour-neutral.
This means that only two types of groupings are possible; 3 quarks (or 3 anti-quarks), or a quark-antiquark pair. The particles of the first type are called baryons, and the most familiar examples are the proton and the neutron. The second type is the mesons. Together they are called hadrons.
As a consequence of this, the bound states can only have integral charges (0, ±1, ±2).
3 Some Familiar Particles
Example: The proton has a charge of +1. It is a baryon, so it is made up of 3 quarks.
Since the up quark has a charge of +⅔ and the down quark has a charge of -⅓, the only way to make up a proton is uud. (⅔ + ⅔ - ⅓ = 1).
The quarks will be one each of rgb, making the proton colour-neutral, and all the rules are satisfied.
u +⅔
u +⅔
d -⅓
Discussion Questions
1. Determine the quark composition of the neutron, which is a neutral baryon.
2. Under normal (low-energy) conditions, the combinations uuu and ddd are not found. Why not?
3. The delta particles are first generation particles (They are similar to the proton and neutron, but have different spin arrangements.) Given that their names are Δ++, Δ+, Δo, and Δ-, find the quark composition of each one.
4. The п+ is a meson with a charge of +1. Which first generation quark and anti-quark does it contain?
5. Now complete the chart of Generation 1 particles, by filling in the symbols.
1 The Particles and their Properties.
There are two types of particles that are thought to be fundamental. That
is, they cannot be broken down into any smaller constituent particles. These two types of particles are the leptons and the quarks.
However, these can, under the right conditions, be converted into energy, or be formed from bundles of energy. Also, the heavier ones can decay into
lighter ones, with the release of some of their energy.
As the regions of the universe near us are now in a much lower-energy state than they were shortly after the big bang, only the lightest particles in
each family are now very commonly observed.
Others can be re-created by high-energy collisions, such as those produced in particle accelerators.
The most familiar member of this group is the electron, but there are also similar, heavier (and hence more energetic) particles called the muon and the tau.
1.1 The Leptons
For each one of these, there is a smaller “partner” called a neutrino – the electron neutrino, the muon neutrino and the tau neutrino.
Each of these 6 also has an antiparticle, for example, the anti-electron or positron.
The leptons are all capable of independent existence.
1.2 Properties of the Leptons
The electron, muon and tau all have mass. The neutrinos have no mass, according to the Standard Model. However, there is some evidence that neutrinos do have an actual, very small mass.
The electron, muon and tau all have electric charges of –1, and their anti-particles have electric charges of +1. The neutrinos have no electric charge.
All of the leptons have another property called “spin”. Their spins can be +½ or -½.
Table of Leptons
Flavour Mass (GeV/c2)
Electric Charge
First Generation
υ e electron
neutrino
e electron
< 1 x 10-8
0.000511
0
-1
Second Generation
υμ muon
neutrino
μ muon
< 0.0002
0.106
0
-1Third Generation
υτ tau
neutrino
τ tau
< 0.02
1.7771
0
-1
The anti-lepton symbols are: e+, μ+, τ+, υ e, υμ, υτ.
1.3 The Quarks
The quarks are not capable of independent existence, and are found only as groups, making up larger particles (called “bound states”).
The quarks have mass and electric charge. The electric charges are either +⅔ or -⅓ for quarks, and -⅔ or +⅓ for the matching anti-quarks.
There are 6 quarks, called up, down, charm, strange, bottom and top. The “everyday” quarks are the up and down quarks. For each quark there is an anti-quark.
They also have spin of ±½. There is also another property called “colour” charge, which comes in 3 varieties, red, green and blue. The anti-quarks have anti-colours: anti-red, anti-green and anti-blue.
Table of Quarks
Flavour Mass (GeV/c2)
Electric Charge
First Generation
u upd down
0.0030.006
+⅔-⅓
Second Generation
c charms strange
1.30.1
+⅔-⅓
Third Generation
t topb bottom
1754.3
+⅔-⅓
The symbols for the anti-quarks are: u, d, c, s, t, b.
2 Rules That The Particles Follow
There are also other rules, for example about spin, which must also be obeyed.
This relates particularly to the grouping together of quarks.
The “bound states” must be colour-neutral.
This means that only two types of groupings are possible; 3 quarks (or 3 anti-quarks), or a quark-antiquark pair. The particles of the first type are called baryons, and the most familiar examples are the proton and the neutron. The second type is the mesons. Together they are called hadrons.
As a consequence of this, the bound states can only have integral charges (0, ±1, ±2).
3 Some Familiar Particles
Example: The proton has a charge of +1. It is a baryon, so it is made up of 3 quarks.
Since the up quark has a charge of +⅔ and the down quark has a charge of -⅓, the only way to make up a proton is uud. (⅔ + ⅔ - ⅓ = 1).
The quarks will be one each of rgb, making the proton colour-neutral, and all the rules are satisfied.
u +⅔
u +⅔
d -⅓
13
1
3
2
3
2
03
1
3
1
3
2
3
2
3
1
Elementary particles today
Top quark discovery (Fermilab 1995)
