hunting for free quarks
DESCRIPTION
Helen Caines Relativistic Heavy Ion Group WNSL - West. Hunting for Free Quarks. The RHI Physics Group. The Actors Faculty : Helen Caines John Harris Thomas Ullrich 1 Research Scientists: Jaroslav Bielcik 2 Jana Bielcikova - PowerPoint PPT PresentationTRANSCRIPT
Pizza Talk – Yale - Jan 2005
Hunting for Free Quarks
Helen CainesRelativistic Heavy Ion Group
WNSL - West
Helen Caines
Pizza Talk – Jan 2005 2
The RHI Physics Group
The ActorsFaculty : Helen Caines
John Harris
Thomas Ullrich1
Research Scientists: Jaroslav Bielcik2
Jana Bielcikova
Matthew Lamont
Nikolai Smirnov
Richard Witt3
Grad. Students: Stephen Baumgardt (1)
Betty Bezverkhny (5)
Oana Catu (3)
Jonathan Gans (Ph.D 04)
Michael Miller (Ph,D 04)
Christine Nattrasse (2)
Sevil Salur (5)
1 – Adjunct, Scientist at BNL
2 – Joint appointment with BNL
3 – Visiting, Scientist at University of Bern, Switzerland
Helen Caines
Pizza Talk – Jan 2005 3
quarkshadrons
mesons baryons
pions,kaons,
..
protons,neutrons,
...
nucleons
protons neutrons
partons
quarks gluons
Some Terminology
Helen Caines
Pizza Talk – Jan 2005 4
More About QuarksOrdinary matter made
of up and down quarks
• Quarks interact by exchanging gluons• Nucleons are held together by gluons• Free quarks have never been seen - distinctive non-integer
charge
Helen Caines
Pizza Talk – Jan 2005 5
Why We Don’t See Free Quarks
Compare to gravitational force at Earth’s surface
Quarks exert 16 metric tons of force on each other!
quark quarkgluons The size of a nucleus is 1.2A1/3 fm
where A is the mass number and a fm is 10-15 m
Helen Caines
Pizza Talk – Jan 2005 6
Evolution of the Universe
Reheating Matter ?
?Need temperatures
around1.5·1012 K
(200 MeV)
The universe gets cooler !10-44 sec Quantum Gravity Unification of all 4
forces 1032 K
10-35 sec Grand Unification E-M/Weak = Strong forces
1027 K
10-35 sec ? Inflation universe exponentially expands by 1026
1027 K
2 10-10 sec Electroweak unification
E-M = weak force 1015 K
2·10-6 sec Proton-Antiproton pairs
creation of nucleons 1013 K
6 sec Electron-Positron pairs
creation of electrons 6 x 109 K
3 min Nucleosynthesis light elements formed 109 K
106 yrs Microwave Background
recombination - transparent to photons
3000 K
109 yrs ? Galaxy formation bulges and halos of normal galaxies form
20 K
Helen Caines
Pizza Talk – Jan 2005 7
RHIC @ Brookhaven National Lab
Long Island
Long Island
• 2 concentric rings of 1740 superconducting magnets• 3.8 km circumference• counter-rotating beams of ions from p to Au
STAR
PHENIX
PHOBOSBRAHMS
• Au+Au @ sNN= 200 GeV • p+p @ s = 200 GeV
Helen Caines
Pizza Talk – Jan 2005 8
What Do Those Numbers Mean?
• Energies are measured in electron volts– 1 eV is the energy acquired by a particle with charge 1 accelerated
across a voltage of 1 volt• keV - 1000 eV• MeV - 1,000,000 eV, 1 million eV• GeV - 1,000,000,000 eV, 1 billion eV
• The binding energy of a nucleus is about 8 MeV/nucleon
• Beam energies are often given in GeV/nucleon– RHIC is one nucleus with 100 GeV/nucleon colliding with another
nucleus with 100 GeV/nucleon going the opposite direction
Helen Caines
Pizza Talk – Jan 2005 9
• Central Au+Au Collision:
NColl. sNN = 40 TeV ~ 6 Joule
How Much Is That?
Sensitivity of human ear:
10-11 erg = 10-18 Joule = 10-12 Joule
Indeed a pretty “Loud Bang“ if E Sound
Most goes into particle creation
Helen Caines
Pizza Talk – Jan 2005 10
Aftermath of a Collision
As seen by STAR experiment at RHIC
End-on view of high energy gold-gold
collision
• >5000 particles
• Only charged particles seen here (there are also lots of neutral particles)
• Neutrals don’t ionise the gas so are not “seen” by the detector.
Helen Caines
Pizza Talk – Jan 2005 11
Blackbody Radiation
Planck distributiondescribes intensityas a function of thewavelength of theemitted radiation
“Blackbody” radiation is the spectrum of radiation
emitted by an object attemperature T
1/Wavelength Frequency E p
Helen Caines
Pizza Talk – Jan 2005 12
inte
nsity
transverse momentum
Systematic Errors not shown
Phobos Preliminary
Determining the Temperature
From transverse momentum distribution deduce temperature ~
120 MeV
Close to Temperature we needed
Helen Caines
Pizza Talk – Jan 2005 13
What’s the Energy Density?• A typical approach
– use calorimeters to measure energy emitted from collision
– estimate the volume of the collisionThe PHENIX
CalorimeterIn Central Collision:
E ~ 650 GeV
R2
Time it takes to thermalize system (0 ~ 1 fm/c)
R~6.5 fm
dydz 0V ~ 130 fm3
BJ 5.0 GeV/fm3
~30 times normal nuclear density
~ 5 times above critical from
lattice QCD
Helen Caines
Pizza Talk – Jan 2005 14
5 GeV/fm3. Is that a lot?
Last year, the U.S. used about 100 quadrillion BTUs of energy:
At 5 GeV/fm3, this would fit in a volume of:
Or, in other words, in a box of the following dimensions:
mfmfm 5105103.1 93 329
Helen Caines
Pizza Talk – Jan 2005 15
Helen Caines
Pizza Talk – Jan 2005 16
One Way To Dig Even Deeper - Jets
hadron
hadron
• Possible for “knock-on” collisions of partons
• Seen in high-energy physics experiments since mid-1970’s
• A real particle physics phenomenon that can be used to probe the trillion degree material we create
Helen Caines
Pizza Talk – Jan 2005 17
Creating a “jet” of particles
• As connection between quarks breaks up, most of the motion stays close to direction of the original quarks
kaon
pion
pion
pion
• The fragmented “bits” appear as “normal” subatomic particles–pions, kaons,etc
pionpion
kaon
• Jets commonly come in
pairs
Helen Caines
Pizza Talk – Jan 2005 18
Case study: opacity of fog
• “is this thing on?”• First beam - least know the
source is on.• Second beam intensity tells you a
lot about matter passed through
Predictions
QGP: the “backwards” jet will be absorbed by the medium
Hadron gas: the “backwards” jet be less affected by the medium
?
Helen Caines
Pizza Talk – Jan 2005 19
Jets in Heavy Ion Collisions?
ee q q (OPAL@LEP)
p-p jet+jet (STAR@RHIC)
Au-Au ??? (STAR@RHIC)
No, but a bit tricky…
Jets in Au-Au hopeless Task?
Helen Caines
Pizza Talk – Jan 2005 20
central Au+Au collisions
trigger Phys Rev Lett 90, 082302
min. bias p+p collisions
Jets & 2-particle Azimuthal Distributions
p+p dijet
• Trigger: highest pT track
• Δ distribution:
0: central Au+Au similar to p+p : strong suppression of back-to-back correlations in central Au+Au
?
Helen Caines
Pizza Talk – Jan 2005 21
Have we found the Quark Gluon Plasma?
• We now know that Au+Au collisions generate a medium that is dense (pQCD theory: many times cold nuclear matter density)
• exhibits behaviour of very hot, thermalized source that is dissipative
• We have yet to prove that:• Dissipation occurs at the partonic stage• The system is deconfined and thermalized • A transition occurs: can we turn the effects off ?
This represents significant progress in our understanding of strongly interacting matter
Not yet, still work to do … (but getting closer)