Transcript history of particle physics (PowerPoint 13.93MB)

Particle Physics and LHC Physics
David Krofcheck
Canterbury Teachers Workshop July 18th
D. Krofcheck
Canterbury Teachers Workshop
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The place to be for high energy physicists
Lac Léman
Jura
CMS
experiment
CERN (FR)
Geneva
airport
CERN (CH)
Thanks to Lucas Taylor, 2012
Large Hadron Collider
CMS
experiment
• 27 km (17 miles)
circumference
Large Hadron Collider
• 1600 superconducting
magnets at 1.9° K (271.3° C or – 459.7°
F)
• 120 tonnes of liquid
helium
• Accelerates beams of
protons to 99.9999991%
the speed of light
Thanks to Lucas Taylor, 2012
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The CMS detector at the Large Hadron Collider
Hadron Calorimeter
EM Calorimeter
New Zealand
Beam Scintillator Counters
Forward Calorimeter
CASTOR
Tracker
(Pixels and Strips)
ZDC
Muon Endcaps
Muon Barrel
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Pitt/CMU July 2011
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The really important CMS detectors
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Pitt/CMU July 2011
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What is matter?
Aristotle : all matter is made up of various
combinations of Earth, air, fire and water
solids
gases
liquids
change
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Canterbury Teachers Workshop
This
belief
about
the
nature of
matter
lasted
for 2000
years
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Development of
the Atomic
Theory
Aristotle
Democritus
John
Dalton
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Canterbury Teachers
Workshop
Lucretius
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Ideas about Atoms
1800’s
John Dalton
– meteorologist and teacher
- successfully explained
chemical
reactions by proposing all
matter is made up of atoms.
- BUT they had no direct
evidence!
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Canterbury Teachers Workshop
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Dmitri
Mendeleev
Russian
1834-1907
Periodic Table
Similar chemical properties
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Canterbury Teachers Workshop
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?
Periodic Table
Atoms
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Rutherford
Canterbury Teachers Workshop
(1909)
Bohr
(1913) 10
...
proton
neutron
electron
•
Are these the elementary particles, ?
•
Are they composed of even more elementary particles??
•
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Particle and Nuclear Physics are the studies to answer this question
Canterbury Teachers Workshop
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Matter Particles
1932
p, n, e
1937
μ
1940s
mesons π, K
1950s
particles Λ, Δ, Σ, ...
ν
…hundreds of new particles were discovered!
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Canterbury Teachers Workshop
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In 1964 the idea of quarks was
proposed…
quarks
These were elementary particle of,
fractional electric charge, different
flavours
Zweig
Gell-Mann
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u
u
d
d
d
u
proton
neutron
Canterbury Teachers Workshop
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What is the composition of the proton
d
u
u
q(u) = +2/3
q(d) = -1/3
q(p) = +1
...and of the neutron
d
u
d
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Canterbury Teachers Workshop
q(n) = -1/3 - 1/3 + 2/3= 0
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What glues the quarks together?
u
u
Gluons, of
course
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d
proton
Canterbury Teachers Workshop
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Elementary particles of matter
1897
1st family:
u, d, e- , e
2nd family:
c, s, - , 
leptons
3rd family:
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t, b, - , 
1995
Canterbury Teachers Workshop
4 July, 2012
Higgs16
Antimatter
Every particle has its antiparticle, of the same mass but
opposite quantum numbers
eg. electron, e- : q(e-) =-1 , spin = -1/2 , m(e-) = 9.110-28 gr.
positron, e+ : q(e+) =+1 , spin = +1/2 , m(e+) = 9.110-28 gr.
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Canterbury Teachers Workshop
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All these interactions are manifestations of only
..
.10-2.
. .
4 basic interactions
-40
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Gravitational Force
1
Electromagnetic Force
-5
10
nuclei
Strong Colour Force
átomo
Weak Force
n  p + e- +  e
d  u + e- +  e
Interaction Type
Mediating Particle
Electromagnetic
γ (photon)
Strong
g (gluon)
Weak
bosons W, Z
Gravitational
G (graviton)
Still not detected experimentally
Example: Electromagnetic interaction
p + + e-  p + + e-
http://www.cerimes.education.fr/
The Fundamental Interactions
are produced by the exchange of a particle mediator
http://www.cerimes.education.fr/
The particles of matter interact across a distance by
exchanging a “messenger” particle
The interaction range decreases as the mass of
the messenger particle increases.
Standard Model of Particle Physics
• Messengers
• interactions
leptons
In a quantum description of matter and the laws of interaction
between them still do not know how to incorporate gravitation, but the
rest of interactions are well described by a mathematical theory, the
Standard Model, able to make predictions that have been confirmed in
experiments.
Standard Model
(~1980)
Symmetry
Components of
matter
Interactions
This model requires that the particle messengers are massless,
But the W and Z are very heavy!!
 problem of the origin of mass
Higgs Boson
The British physicist Dr. Peter Higgs proposed (1964) the so-called
Higgs mechanism:
All the particles would be generated in the Big Bang without mass,
but by interacting with the field created by the Higgs particle, the
particles would acquire mass, the greater, the greater the
interaction. This field would fill the whole universe.
Interaction with the
Higgs field
≡
Friction with a
viscous liquid
Higgs Boson
The British physicist Dr. Peter Higgs proposed (1964) the so-called
Higgs mechanism:
All the particles would be generated in the Big Bang without mass,
but by interacting with the field created by the Higgs particle, the
particles would acquire mass, the greater, the greater the
interaction. This field would fill the whole universe.
Interaction with the
Higgs field
≡
Friction with a
viscous liquid
Unico “Higgs” observado hasta ahora en un
experimento…el propio Dr. Higgs!!
Higgs Boson
This particle predicted has not yet been unambiguously
.
detected in experiments, hopefully we are hot on the trail!
≡
A recent view of a Higgs at the CMS experiment
!!?? H  Z0 Z0  μ+ μ- μ+ μ-
Gauge Bosons – Z0 First detection in HI collisions!
First step is to find Z0
bosons in PbPb collisions
Z0 → μ+μ - observed for the first time
in HI collisions!
Z0 → e+e- event candidate
Z0 → e+e- observed for the first time
in HI collisions!
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lead + lead collisions may liberate quarks
Jet production in pp collisions
jet-jet correlation in QCD “vacuum”
Jet
Jet
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Dijet Probes of Hot Nuclear Matter at the LHC
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Jet production in PbPb collisions
jet-jet correlation in QCD “medium”
γ – jet correlation to probe the medium?
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Dijet Probes of Hot Nuclear Matter at the LHC
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E-ΔΕ1
Δφ
Dijet imbalance in PbPb collisions
E-ΔΕ2
Phys. Rev. C 84, 024906 (2011)
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Dijet Probes of Hot Nuclear Matter at the LHC
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Jet production in PbPb collisions
gamma-jet correlation in QCD “medium”
Gamma
Nuclear remnant
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Nuclear remnant
Dijet Probes of Hot Nuclear Matter at the LHC
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Observed momentum imbalance in γ – jet correlation
Submitted to PLB, arXiv:1205.0206
• Momentum ratio shifts/decreases with centrality
– jets shifting below the 30 GeV pT threshold not included
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Dijet Probes of Hot Nuclear Matter at the LHC
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Energy Units!
Electron Volt – Energy gained by an electron when accelerated in an electric field
through a potential difference of 1 volt.
1 eV
= 1 electron Volt
Energy to ionise hydrogen = 13.6 eV
1 keV(kilo)
= 1,000 eV
= 103 eV
Medical X-ray ~ 200 keV
1 MeV(Mega) = 1,000,000 eV
= 106 eV
Alpha particle decay of uranium 4.2 MeV
1 GeV(Giga) = 1,000,000,000 eV
= 109 eV
LEP collider beam (1989-2000) = 45 GeV
1 TeV(Tera)
= 1,000,000,000,000 eV
= 1012 eV
Highest energy accelerator in world = 1 TeV (Tevatron)
Highest energies
found in cosmic rays (>1020 eV)
Interactions between matter particles
Why are there so many different substances
in the world?
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Canterbury Teachers Workshop
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