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
Office Physics D-143
www.physics.sunysb.edu PHY313
Peter Paul 03/17/05
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What have we learned last time
• This leads to the Standard Model
• The six quarks that are the building
blocks of strongly interacting matter
have six equivalent particles that are
responsible for the weak interaction.
• These are the three lepton families:
–  lepton and  neutrino
– μ lepton and μ neutrino
– electron and e- neutrino
• The strong interaction is mediated by the
gluons which transfer “color” between
quarks. There are 8 gluons.
• The weak interaction is mediated by the
W± and the Z0 bosons. These are VERY
massive particles which is why the very
weak interaction. has very short range.
The EM interaction is mediated by the
photon
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What have we learned last time II
• We can prove that Leptons come
in only 3 families. Thus it is
suggestive that quarks also have
only 3 families.
• Quarks all have masses. Some leptons
have masses, but neutrinos may not.
Why should they not have mass?
• The Standard model divides particles
into fundamental building blocks
which have spin ½ or 3/2. and are
called Fermions. The second group are
the force carriers. They have spin 0 or
(mostly) spin 1 and are called Bosons.
• Why do we have these two groups?
Are they distinct and separate?
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The puzzle of the masses of the
quarks:
• The proton is made up of 2 up
quarks and one down quark: uud.
• Each bare quark has a mass of only
about ~ 2 MeV,
• Yet the proton has a mass of 938
MeV: Where is all that additional
mass coming from?
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The three quark families
Spin
Charge
First family
Second family
Third family
1/2
+2/3
up
(3 MeV)
charm
(1300 MeV)
top
(175,000 MeV)
1/2
-1/3
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
(and their anti-quarks in the meson case).
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html
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Evolution of the Universe
~ 10 ms after Big Bang
Hadron Synthesis
T = 1.7 1012 K
(~ 170 MeV)
strong force binds quarks and gluons in
massive objects: p & n; mass ~ 1 GeV
~ 100 s after Big Bang
T = 109 K
Nucleon Synthesis
strong force binds protons and neutrons
into nuclei
QCD: Quantum Chromo Dynamics
the theory of the strong interaction
Confinement & Chiral Symmetry
• Unbound quark has ~1 MeV
• The bound (Constituent) quarks ~ 300 MeV
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QCD Matter at High Temperature and Density
nuclear matter
p, n
Quark-Gluon Plasma
q, g
density or temperature
QCD potential that binds quarks
1. in vacuum:
• linear increase with distance
• strong attractive force
• confinement of quarks to hadrons :
baryons (qqq) and mesons (qq-bar)
2. in dense and hot matter
• screening of color charges; Debye screening
•potential vanishes for large distance
• deconfinement of quarks  QGP
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The Phases of Water as Model for Quark Matter
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QCD predictions from exact calculations
Results from lattice QCD establish the QCD phase transition and chiral
symmetry transition at T~ 270 MeV
Karsch, Laermann, Peikert (99)
eC = 0.6 GeV/fm3
TC ~ 170 MeV
Calculation indicates a big jump in energy density: At temperature…
TC ~ 170 MeV
eC = 0.6 GeV/fm3
T ~ 220 MeV
e = 3.5 GeV/fm3
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The QCD Phase Diagram
Line of phase transition
• Hadronic matter can be plotted in a phase diagram which plots the matter
temperature versus the matter density  (“Baryon chemical potential”).
•At high temperature (170 MeV for  = 0) or high density ( ~ 5 – 1- times
nuclear density) normal hadronic matter turns into a quark-gluon plasma.
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Energetic Gold collisions simulate early Universe
• Create QGP as transient state in heavy ion collisions  up to 400
nucleons in close proximity
– verify experimentally existence of QGP
– study QCD confinement of quarks to hadrons
– study how hadrons get their masses
• Retrace spontaneous breaking of chiral symmetry
Turn “chiral quarks ( ~ 5 MeV for u,d ) into constituent quarks ( ~ 300 MeV
for u,d)
• Exploration of QCD many-body states using p-A and e-A collisions
– Discover Color Spin Glass (saturated gluonic matter)
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Schematic View of a Heavy Ion Collision
b~0
projectile
p
J/
target
K
p
cc
p
p
p
p
p
e-
p
p
e+
Several 1000 particles are
produced in central collisions, i.e. when projectile and target hit head on
• Lots of hadrons ( p, K, p ) are produced when particles stop to
interact (freeze-out), i.e. at the end of the collision
• A few quanta of EM radiation or lepton pairs are emitted from the hot
collision zone
• http://www.bnl.gov/rhic/heavy_ion.htm
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Violent collisions free up lots of particles
The particles are tracked in
large detectors at RHIC such
as STAR (left) and PHENIX
(right)
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Relativistic Heavy Ion Collider (RHIC)
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Evolution of nuclear accelerators
• Use of particle accelerators for NP began in the 1920’s
with Cockcroft and Walton and advanced in the 1930’s
with invention of the cyclotron by Lawrence.
• Cyclotrons were the workhorses in the 1950’s because
of their ruggedness.
• In 1960 the first high-energy synchrotron was
invented. It is still working today as the AGS at BNL
• In the 1960’s electrostatic accelerators became widely
used with the introduction of the Van de Graaf
accelerators.
• In the 1970’s linacs came into wider use with
superconducting technology.
• In the 1970’s colliders were invented which pushed the
collision energy much higher
• Today the LHC at CERN is being completed as the
world’s largest accelerator
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Acceleration with DC or AC Electric Fields
• Acceleration is done by the Coulomb
force acting on the positive or
negative charge of the accelerated
particle.
• These can be electrons, protons or
heavy ions. For example RHIC uses
Au beams stripped bare (q = 79 x e )
• Acceleration principle is very simple:
E= q V where q = n x e. V can be a
positive or negative voltage
depending on what charge is being
accelerated .
• Typical voltages can be 1 MV/m or
even 70 MV/m
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• Acceleration in a DC field produces
a steady beam.
• Acceleration in an AC or radio
frequency (rf) field produces beam
bunches.
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Electrostatic fields and focusing
• Just like light beams in a
microscope particle beams must
(and can) be focused along their
way.
• Electric fields widely used for
beam focusing (picture tubes!).
• It is weak focusing because one
cannot achieve very high electric
DC fields: ~ 1 MV/m
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Modern electrostatic accelerators
Beams of heavy ions are
accelerated by a DC voltage from
the top down to the base
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The high-voltage terminal
of this escalator is at 18
MV! The column is inside
a tank that is filled with
insulating gas at high
pressure
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Beam deflection in magnets
• The Lorentz Force from a magnetic field B
acts on charged particles with charge q and
velocity v:
FL  qBv
• This force deflects the beam but does not
accelerate it.
• The force acts perpendicular to the
direction of flight. The bending power is
directly proportional to the magnetic field
strength B.
• This can be used in particle accelerators to
bend and/or focus beams
• It is also used to deflect charged particles
in detectors
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Strong focusing with magnetic quadrupoles
• A magnetic quadrupole lens focuses
in one transverse direction but
defocuses in the other.
• However a sequence of two lenses
with a drift space in between has a
net focusing effect in two
transverse dimensions.
• Focal length of a single lens is
given by
fx  -
X-focusing
mv
 - fy
qBL
fx  -
Y-focusing
p
 - fy
qBL
• Since B can be large magnetic
lenses can be very powerful.
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Beam transports using strong focusing lenses
• Magnetic Quadrupole fields are
the work horse of all modern
accelerators .
• A single quadrupole focuses in
one direction, defocuses in the
orthogonal direction. Thus two
lenses must always be paired
• The strongest lenses can be
made with superconductors.
These can have very mall
dimensions
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• Below shows the beam transport
system with several quadrupole
pairs for the electron accelerator at
Jefferson Laboratory
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Bunch Compression and Phase Stability see lecture 6
• In an r.f. accelerator beam need to be bunched in time and then the
bunches must be kept together as they travel through the accelerator
E/E
E/E
z
E/E
z
E/E
z
E/E
z
z
RF
dispersive section
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Linear accelerators (LINACs)
• Linacs are accelerators for high
currents and for electrons at very high
energies (synchrotron radiation!).
• They use either traveling or standing
EM waves with multiple acceleration
gaps in resonators.
• As a beam bunch travels from one gap
in the resonator to the next it must
stay “in phase” with the r.f. wave.
• Accelerating field levels achieved can
be as high as 70 MV/m!
• For a 1000 GeV accelerator at 30
MV/m this means a length of ~100
km or 62 miles. In practice it requires
about twice that much!
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• Resonance condition for Linac structure
beam
v
• Length of each drift tube L = vT
  t  2p  f  T  p ;
1
T
;
2f
L v/2f
• Thus as v increases L must increase
• For ultra-relativistic beams with v ~ c
(like electrons) L can remain constant.
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Electromagnetic Resonators
see lectures 3-4
on linac
This is a traveling wave
resonator structure. The
EM wave travels with the
beam particles and the
beam particles are riding
the wave.
This is a standing wave structure.
The beam enters each resonator
section as the r.f. wave in that
section has a high field and the
correct polarity
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Superconducting Resonators
• Superconducting resonators made
from Nb have achieved the highest
quality and highest electric field.
• Quality = stored energy/dissipated
energy
• The stored energy is proportional to
the square of the accelerating field
• A high-quality resonator achieves a
high electric field with very little
power loss.
• Q-factors of 1011 have been achieved
up to accelerating fields of 30 MV/m !
• This requires extreme cleanliness and
very smooth surfaces
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Stanford Linear Accelerator
• Stanford University pioneered the
large electron LINAC since 1960.
This is the 30 GeV SLAC facility
which is ~ 2 miles long.
• For the electrons travelling through
the resonators the acclertor is Lorentz
contracted and only ~ 20 cm long!
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The Energy Frontier is provided by Colliders
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LEP at CERN, CH
Ecm = 180 GeV
PRF = 30 MW
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Synchrotrons
• Synchrotrons are essentially linacs curled
• Synchtroron beams use the same
in a circle using powerful magnets to
accelerating resonator over and
bend the beam.
over again: Very cost efficient
• On its circular path the beam bunches
travels through a few resonators millions • Below shown the reosnators of the
RHIC rings.
of time. They must satisfy a resonance
condition:
• The beam bunch must always get to the
resonators when the r.f. field has the right
amplitude and polarity
• This condition requires that the r.f.
frequency f and magnetic field B must
both be changed as the beam energy
increases. B must be “ramped up” until the
beam reaches its final energy.
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RHIC produces ultra-relativistic heavy ions
12:00 o’clock
PHOBOS
10:00 o’clock
RHIC
PHENIX
8:00 o’clock
STAR
6:00 o’clock
U-line
High Int. Proton Source
BAF (NASA)
LINAC
BRAHMS
2:00 o’clock
Design Parameters:
Beam Energy = 100 GeV/u
No. Bunches = 57
No. Ions /Bunch = 1  109
Tstore = 10 hours
Lave = 2  1026 cm-2 sec-1
BOOSTER
Pol. Proton Source
AGS
HEP/NP
1 MeV/u
Q = +32
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Four detectors
4:00 o’clock
9 GeV/u
Q = +79
m g-2
Six collision
regions
TANDEMS
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RHIC Pictures (1)
Two rings of superconducting magnets
bend a clockwise and a counter clockwise circling beam on circular paths.
The magnets are cooled to 2 degrees K
above absolute zero
At this point the Gold beams send over
from the AGS are divided into clockwise and a counterclockwise beams that
are then accelerated and stored
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RHIC Pictures (2)
Rf storage cavities serve maintain
the energy of the circulating beam
and to keep the beam particles well
bunched. Bunches in one ring will
then intersect with bunches from
the other ring.
Installation of final focussing
Triplets. These are superconducting
quadrupole lenses that focus the two
beam to a very small size at the
intersection points
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Artful bunch manipulation for maximal intensity
Time during AGS cycle
– 4  6 bunches injected from Booster
– Debunch / rebunch into 4 bunches
at AGS injection
– Final longitudinal emittance:
0.3 eVs/nuc./bunch
– Achieved 4  109 Au ions in 4
bunches at AGS extraction
AGS circumference
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RHIC extremely well understood:
beam measurements and theory
Measured beam width (red circles)
agrees well with prediction (line).
Successfully used to diagnose problems
in the accelerator system .
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Bringing beams into collision
Beam in blue ring
Beam in yellow ring
200 ns (60 m)
Beams in collision at the
interaction regions
200 ns (60 m)
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Coll. rate / Blue Ions / Yellow Ions [Hz/1018]
Summer 2000 first run shows stored beam
The beams circle around for many hours but slowly lose
intensity due to scattering among beam particles
Expected: 1.1 for PHENIX and BRAHMS
0.4 for STAR and PHOBOS
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The LHC at CERN under Construction
• The LHC is the largest accelerator
construction project in the world
today.
• https://www.CERN.org
LHC is a proton collider (2 beams
in one magnet) deep under the
suburbs of Geneva (Switzerland)
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Detectors surround the collision point at RHIC
– 2 central
spectrometers
West
Collision point
– 2 forward
spectrometers
South
East
North
– 3 global
detectors
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Detection of charged particles
• Charged particle ionize gases.
The degree of ionization
depends on the charge of the
particle and its velocity.
• The particle ionizes most
heavily at the end of its path.
• The ionization products than be
deflected by an electric or
magnetic field toward a
recording device.
• Such detectors are wire
Bragg Curve of an Iron beam shows the
chambers or time projection
degree of ionization as the particle
chambers (TPC)
penetrates into a plastic material
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The STAR TPC Detector
This detector consists of a huge
solenoid magnet and all particles
produced in the nuclear reaction
move in and are bend by the
magnetic field.
This detector can record thousands
of particle tracks simultaneously
The ionization products
produced by charged
particles drift to the end of the
magnetic field. From the drift
time the path of the ionizing
partcle can be reconstructed
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Big Time Projection Chamber STAR
First Events June 12 - 15 2000
first Au-Au collisions at STAR June 12
Brookhaven Science Associates
U.S. Department of Energy
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The PHENIX Detector Drift Chambers
PHENIX has a pole magnet
to bend charged particles
and detects them in drift
chambers, where ionization
products drift to many
thousands of wires.
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Drift chamber + Pad chamber 1
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PHENIX Detector Configuration
• Two central arms
– Mechanically
~complete
– Roughly half of aperture instrumented
• Global detectors
– Zero-degree Calorimeters (ZDCs)
– Beam-Beam Counters (BBCs)
– Multiplicity and Vertex Detector
(MVD, engineering run)
www.phenix.bnl.gov
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Hadron Identification in PHENIX
Combined
– Tracking
– Beam-Beam Counter
– Time-of-Flight array
These detector can separate particle species,
both negative and positive, very cleanly by
use of the time of flight (TOF)
provides excellent hadron
identification over broad
momentum band:
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The ATLAS Detector for the LHC
http://pdg.lbl.gov/atlas/
• The LHC will have three large
detectors: CMS, ATLAS and ALICE.
• Because the energies will be so much
larger than at RHIC these detectors
will be larger than the RHIC
detectors, but they follow the same
principles.
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The central part of the ATLAS detector
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Detention of Gamma rays
• Gamma rays can be detected with
very high efficiency and resolution by
use of semiconductor detectors, such
as Germanium crystals.
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Eighth Homework Set, due April 7, 2005
1. Describe briefly how one attempts to “free up” (deconfine) individual
quarks and what temperatures are required to achieve that goal.
2. How long after the initial Big Bang did the quarks freeze into nucleons
and mesons?
3. What force is used to accelerate charged particles? Can we build
accelerators for negatively charged particles (electrons) and for
positively charge particles (protons)?
4. What are the properties of a “Synchrotron” that are the basis for its
name?
5. How can we use magnetic fields to focus charged particles in space?
6. What property of charged particles is used to detected them and measure
their charge and velocity?
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