Download The Search for the Critical Point

collisions at the highest RHIC energies will become discontinuous if the excess
Temperature
Figure'2.25'from'page'92'of'Exploring*the*Heart*of*Ma2er*
Early Universe
The Phases of QCD
LHC Experiments
RHIC Experiments
IC
RH
er
En
gy
Sc
a
~170 MeV
n
Crossover
Quark-Gluon Plasma
Future FAIR Experiments
1 st o
rder
ion
sit
Critical Point
pha
se
tra
n
Hadron Gas
Vacuum
Nuclear
Matter
Color
Superconductor
Neutron Stars
0 MeV
0 MeV
900 MeV
Baryon Chemical Potential
FIGURE 2.25 The phase diagram of QCD is shown as a function of baryon chemical potential (a
measure of the matter to antimatter excess) and temperature. A prominent feature in this landscape
2-25_QGP.5
FINAL
PRINT.eps
is the location of the critical
point, which indicates
the end
of the first-order phase transition line in
this plane. SOURCE: DOE/NSF, Nuclear Science Advisory Committee, 2007, The Frontiers of Nuclear
Science: A Long Range Plan.
QCD Phase Diagram
Big Bang
T
Quark Gluon Plasma
RHIC
SPS
Supernova
Hadron Gas
Nuclear Liquid
Color Superconductivity
Neutron Stars
µ
( ρ)
From'Thomas'Schaefer,'NC'State'
More'phase'diagrams'of'QCD'.'.'.'
What is QCD? What is a Phase of QCD?
What is a Phase Diagram?
Phase Diagram: Equilibrium state as a function of
thermodynamic (or other: mq , Nc , Nf , B) variables.
Here : Ω(T, µ, V ) = −V P (µ, T )
• Other choices of independent variables: G(P, T, N ), . . .
• At T = 0 have µ = E(Nq + 1) − E(Nq ).
• In real experiments control parameters are more complicated (beam energy Ecm , impact parameter b (→ Nch ),
system size A).
From'Thomas'Schaefer,'NC'State'
Pressure'vs.'Temperature'for'3'“substances”'
Thermodynamic'PotenFals'
•  Use'the'thermodynamic'potenFal'
appropriate'to'the'system:'what'is'held'
fixed?''If'S,V,N'then'use'internal'energy'U.'
•  At'equilibrium,'the'appropriate'
thermodynamic'potenFal'is'minimized,'
which'determines'the'phase;'e.g.,'S,V,N'
constant'!'U'minimized;'T,V,μ'constant'
!'Ω'minimized.'
•  For'the'grand'potenFal'Ω,'phase'
boundaries'have'equal'temperature'T'and'
chemical'potenFal(s)'μ'for'each'phase.'
What is QCD (Quantum Chromo Dynamics)?
Elementary fields:
Quarks
⎧
⎪
⎪
⎨ color a = 1, . . . , 3
(qα )af
spin α = 1, 2
⎪
⎪
⎩
flavor f = u, d, s, c, b, t
Gluons
Aaµ
⎧
⎨ color a = 1, . . . , 8
⎩ spin ϵ±
µ
Dynamics: Generalized Maxwell (Yang-Mills) + Dirac theory
1 a a
L = q̄f (iD
/ − mf )qf − Gµν Gµν
4
Gaµν = ∂µ Aaν − ∂ν Aaµ + gf abc Abµ Acν
&
%
µ
a a
iD
/ q = γ i∂µ + gAµ t q
From'Thomas'Schaefer,'NC'State'
“Seeing” Quarks and Gluons
ALEPH
Run=9063
Run=15768 Evt=5906
q
e+
q
g
e−
q
e−
Evt=7848
Made on 28-Aug-1996 13:39:06 by DREVERMANN with DALI_D7.
Filename: DC015768_005906_960828_1338.PS_2J_3J
e+
DALI
q
From'Thomas'Schaefer,'NC'State'
Jet'Quenching'in'RelaFvisFc'Heavy[Ion'Collisions'(at'LHC)'
•  LHC'usually'collides'protons'on'protons'
•  Four'weeks'each'year'switches'to'Pb[Pb'
•  Principal'component'of'ALICE'detector'is'a'Fme'
projecFon'chamber'(TPC).'Wikipedia:'“consists'
of'a'gas[filled'detecFon'volume'in'an'electric'
field'with'a'posiFon[sensiFve'electron'collecFon'
system.'The'original'design'(and'the'one'most'
commonly'used)'is'a'cylindrical'chamber'with'
mulF[wire'proporFonal'chambers'(MWPC)'as'
endplates.''
ALICE'detector'
•  RHIC:'Au'on'Au'at'100'GeV/A'
•  LHC:'Pb'on'Pb'at'2'TeV/A!'
•  Jets'lose'energy'traversing'the'
fireball'!'jet'quenching'
•  Amount'of'quenching'gives'
info'about'the'QGP'
Jet'Quenching'in'RelaFvisFc'Heavy[Ion'Collisions'(at'RHIC)'
From:'hfps://www.star.bnl.gov/central/focus/highPt/'