From RHIC to LHC The Little Bang Evolution Rene Bellwied Wayne State University

1
From RHIC to LHC The Little Bang EvolutionRene
Bellwied - Wayne State University
Why RHIC/LHC ? Discovery of the sQGP Puzzling
properties The role of the LHC in understanding
QCD
From RHIC to LHC The next 30 yearsRene
Bellwied - Wayne State University

• 10th Tamura Symposium
• Nov.20-22, 2008
• UT Austin

2
The first second of the universe
AP NP HEP

• from D.J. Schwarz, astro-ph/0303574

3
Going back in time

• Age Energy Matter in universe
• 0 1019 GeV grand unified theory of all
  forces
• 10-35 s 1014 GeV 1st phase transition
• (strong q,g electroweak g, l,n)
• 10-10 s 102 GeV 2nd phase transition
• (strong q,g electro g weak l,n)
• 10-5 s 0.2 GeV 3rd phase transition
• (stronghadrons electrog weak l,n)
• 3 min. 0.1 MeV nuclei
• 6105 years 0.3 eV atoms
• Now 310-4 eV 3 K
• (13.7 billion years)

LHC
RHIC, LHC FAIR
FRIB FAIR
4
The evolution of luminous matter
Standard model is symmetric. All degrees of
freedom are massless.
Electro-weak symmetry breaking via Higgs field
(Dm of W, Z, g) Mechanism to generate current
quark masses (but does not explain their
magnitude)
QCD phase transition (I) chiral symmetry
breaking via dynamical quarks. Mechanism to
generate constituent quark masses (but does not
explain hadronization)
QCD phase transition (II) Confinement to
hadrons. Mechanism to generate hadron properties
(but does not explain hadron masses)
5
The main features of Quantum Chromodynamics
(Nobel Prize 2004) how far are we in probing
them ?

• Confinement
• (Hidden) chiral
• symmetry

• Asymptotic
• freedom

B.Mueller (2004) New Discoveries at RHIC
6
Expectations from Lattice QCD
Chiral restoration (based on quark condensate
melting) deconfinement (based on Polyakov loop
calculation) occur at the same temperature
?/T4 degrees of freedom
Latest results TC 192-7 -4 MeV ?C ? 0.7
GeV/fm3
TC 2?1012 K 130,000?TSuns core
7
High-pT suppression (evidence for partonic medium)
Experimental evidence for a new state of matter
STAR, nucl-ex/0305015
pQCD Shadowing Cronin
energy loss
pQCD Shadowing Cronin Energy Loss

• Deduced initial gluon density at t0 0.2 fm/c
  dNglue/dy 800-1200
• 15 GeV/fm3, eloss 15cold nuclear matter
  (compared to HERMES eA)
  (e.g. X.N. Wang nucl-th/0307036)
• SYSTEM NEEDS TO BE PARTONIC

8
Anisotropic flow (evidence for strong coupling)
Strong collective flow elliptic expansion
with mass ordering
Hydrodynamics strong coupling, small mean free
path many interactions NOT plasma-like system
behaves liquid-like
9
Quark scaling (evidence for deconfinement) The
medium consists of constituent quarks
?Recombination of constituent quarks instead of
parton fragmentation ?
baryons
mesons
10
A multitude of hadronization scenarios
pQCD
Hydro
Medium modifiedfragmentation (jet quenching)
Parton recombinationandcoalescence
Fragmentation
Soft
11
How strong is the coupling ?
Simple pQCD processes do not generate sufficient
interaction strength. Navier-Stokes type
calculation of viscosity yield a near perfect
liquid Viscous force 0. We have made a sQGP,
not the anticipated wQGP.
RB, J.Phys.G35044504 (2008)
Lacey et al., PRL 98 (2007) 092301
The quantum limit has been reached at RHIC and
has been independently verified in several
measurements of collective effects
12
The evidence at hand

• We have produced a strongly coupled but
  deconfined state of matter.
• The degrees of freedom are not well understood.
• Its hadronization mechanism is dominated by
  recombination rather than fragmentation
• It is not a weakly coupled plasma.
• There is little evidence for chiral symmetry
  restoration.

13
Lessons from RHIC The Quark SoupAIP
ScienceStory of 2006
Hirano, Gyulassy (2006)
14
Learn more about the state of matter and its
differences at RHIC LHC

• There will be many studies of a more quantitative
  understanding of parton energy loss in a partonic
  medium (see J. Harris talk)
• There will be many studies of medium properties
  through medium response (see B. Muellers talk)
• Can we measure a change in coupling and thus a
  change in the degrees of freedom ?
• Can we measure chiral restoration ?

15
How strong is the sQGP ?
The temperature dependent running coupling
constant as
Polyakov Loop Calculation Perturbative QGP
(wQGP) is reached at 3Tc Different initial
conditions at RHIC and LHC !
Also resummed perturbative calculations
Blaizot, Iancu, Rebhan, hep-ph/0303185
16
If coupling stays strong, viscosity stays
low(test with heavy flavor v2 and RAA)
c/b quenching
W. Horowitz, arXiv0710.0595

• At RHIC heavy flavor quenches and flows like
  light flavor
• Taking the ratio cancels most normalization
  differences seen previously
• pQCD ratio asymptotically approaches
  unity,AdS/CFT ratio is flat and many times
  smaller than pQCD

17
What changes (I) the partonic lifetime

• S. Bass, Hydro-calculation
• I.Vitev, Bjorken expansion with lattice initial
  T.
• Upper limit based on longitudinal Bjorken
  expansion
• tQGP t0 (T0/Tc)3 with
• T0(t0, LHC) 713 MeV and Tc 180 MeV
• tQGP (LHC) 14 fm/c

from RHIC to LHC lifetime of QGP phase nearly
doubles
18
What changes (II) pT ranges for different model
scenarios

• Thermal recombination pushes to higher pT because
  of higher parton ltpTgt. (Fries, Mueller, EJP
  C34(2004)S279)
• Shower recombination (from overlapping or
  neighboring jets) pushes recombination out to 20
  GeV/c (Hwa, nucl-th/0603053)

• Hydrodynamics pushes to higher pT because of
  longer partonic lifetime and higher parton ltptgt
  (Ruuskanen, hep-ph/0510019)

19
What changes (III) Strangeness is oversaturated
charm is abundant
Kuznetsova Rafelski Oversaturated strange
binds to charm
Braun-Munzinger Abundant charm recombines to J/y
20
Fundamental QCD studiesx distributions
modified (AA) unmodified (pp)

• In AA Jet quenching populates lower pT hadron
  spectrum
• In pp QCD models predict particle mass ordering
  of mean x value, BABAR and STAR observe an
  inverse ltxgt ordering of K0s and L or p

Rlt0.4
LHC equiv.
RHIC equiv.
21
A QGP in pp at the LHC ?
60,000 MB events dNch/dh 50 !

• dNch/dh 50-100
• mid-central CuCu at RHIC
• E 5-10 GeV/fm3
• small but dense system
• QGP physics with protons
• Hadronic FS interaction
• Collectivity
• Maybe mini-QGP

22
Collectivity in pp at RHIC ? Radial and elliptic
expansion
HBT
spectra
Blastwave fits to spectra and HBT
v2
23
Could chiral symmetry restoration decouple from
deconfinement ?
In lattice QCD compare quark condensate to
Polyakov Loop evolution as a function of T. Shows
that deconfinement and chiral symmetry
restoration (CSR) happens at about the same
temperature (some 20-30 MeV uncertainty). But
does constituent quark scaling indicate
experimental evidence for decoupling ?
CSR
Peter Petreczky et al.
RB, N.Xu (2005)
23
24
Dependence of the quasi-particle mass on the
running coupling constant as
Levai Heinz (quasi-particles)
O.Kaczmarek et al. (Lattice QCD)
(hep-ph/9710463)
(hep-lat/0406036 hep-lat/0503017)
in an expanding system interplay
between distance and temperature
25
How to obtain evidence for CSR- a new idea (C.
Markert, RB, I.Vitev, arXiv0807.1509)

• Is it possible to have hadron production prior to
  hadronization, i.e. can there be a mixed phase of
  degrees of freedom (partons/hadrons) ?
• If these hadrons are resonances, can they also
  decay within the partonic phase or the dense
  hadronic phase and thus be medium modified ?
• Lattice QCD predicts a cross-over, thus no mixed
  phase in the thermal sense (e.g. water/steam),
  but the degrees of freedom could still be mixed
  if one dof is governed by thermalization and the
  other dof is governed by fragmentation
• Fragmentation is driven by fundamental formation
  time

hadrons/ resonances
partonic medium
partonic medium
hadrons/ resonances
a mixed d.o.f. system
26
Comparing resonance formation time to QGP
lifetime

• What is the proper t0 ?
• t0 requires thermalization which is an open issue
  at RHIC and LHC. Simple collision time tc 2RA/g
  is definitely too short.
• General approach t0 1/ltpTgt leads to
  t0(LHC)0.23 fm/c (with ltpTgt 850 MeV/c)
• What is the proper QGP lifetime ?
• Upper limit based on longitudinal Bjorken
  expansion
• tQGP t0 (T0/Tc)3 with T0(t0, LHC) 713 MeV
  Tc 180 MeV
• (see paper for more detail) tQGP (LHC) 14
  fm/c
• What is the proper hadronic formation time ?
• depends on boost and fractional momentum in light
  cone variables

arXiv 0807.1509
27
Formation Time of Resonances in LHC QGP
arXiv 0807.1509
28
Lifetime of hadronic resonances

• Problem if we want to measure medium
  modification of a hadronic resonances through the
  partonic medium the resonance does not only have
  to be formed but it also needs to decay in the
  partonic or the dense hadronic medium.
• No problem for very short-lived resonances (t lt 4
  fm/c)
• But these are ground state lifetimes.
• One has to assume that medium
• modification leads to lifetime shifts
• (e.g. Holt Haglin, J. Phys. G31 (2005))

• Short life time fm/c
• D lt ? lt K lt ? lt ?(1520) lt ?
• 1.2 lt 1.3 lt 4 lt 6 lt 13 lt 40

29
A dynamic problem

• The expanding system will drop in temperature and
  in parton-hadron interaction rate.
• The in-medium resonance lifetime will increase
  with dropping temperature.
• The resonance formation time will change with
  mass and momentum
• Bottomline there is no quantitative estimate on
  the best measurement to make
• Qualitatively short-lived resonances will more
  likely be modified. But too short a lifetime
  makes reconstruction difficult (broad states)
• modified K, L, S, f are the best candidates
• Qualitatively there must be a minimum momentum
  for fragmentation rather than bulk formation and
  there must be a maximum momentum to have
  resonances decay inside QGP
• suggestion pT-range for RHIC 3-10 GeV/c, for
  LHC 2-20 GeV/c

30
The principle measurementquadrant correlation
analysis
near side1 away side2
31
Measuring pp/AA in all LHC experiments

• ALICE
• Dedicated most versatile heavy ion detector
• Important for particle identified fragmentation
  measurements in pp
• CMS/ATLAS
• Dedicated most versatile pp detectors
• Important for calorimeter based jet measurements
  in AA.

32
New / future analysesAnalogy to the early
universe - evolution of the system
Heavy-ion Collisions Rapid Expansion
collision evolution
particle detectors
The Universe Slow Expansion
expansion and cooling
kinetic freeze-out
distributions and correlations of produced
particles
hadronization
lumpy initial energy density
QGP phase quark and gluon degrees of freedom
collision overlap zone
quantum fluctuations
credit NASA
? 0 fm/c
? 10 fm/c
?01 fm/c
particle distribution in h and f in STAR