Axel Drees, Stony Brook University
Rutgers NJ, January 12 2006
Nature of matter created at RHIC
Critical Point
Hadronization
Rapid thermalization
Status of key experimental probes limitations of progress and solutions with upgrades of RHIC
Time line, detector and accelerator upgrades (RHIC II)

T
r
Exploring the Phase Diagram of QCD
Quark Matter
Quark Matter: Many new phases of matter
Asymptotically free quarks & gluons
Strongly coupled plasma
Superconductors, CFL ….
Mostly uncharted territory sQGP
T
C
~170 MeV
Hadron
Resonance Gas
Experimental access to “high” T and moderate r region: heavy ion collisions
Pioneered at AGS and SPS
Ongoing program at RHIC
Nuclear
Matter baryon chemical potential
940 MeV
Overwhelming evidence:
Strongly coupled quark matter produced at RHIC
1200-1700 MeV m
B
Axel Drees

PHENIX
130 GeV
Bjorken estimate: t
0
~ 0.3 fm dN g /dy ~ 1100 central 2%

B j


1
R
2 c
1 t
0


 d E dy
T



Huovinen et al
Pt GeV/c

~ 10-20 GeV/fm 3
Initial conditions: t therm
~ 0.6 -1.0 fm/c

~15-25 GeV/fm 3
Heavy ion collisions provide the laboratory to study high T QCD!
Axel Drees

and our experimental approach at RHIC
Is the quark-gluon plasma the most perfect liquid? If not, what are its quasi particles?
Hard penetrating probes with highest possible luminosity at top
RHIC energies
Excitation function and flavor dependence of collective behavior
Is there a critical point in the QCD phase diagram and where is it located?
Low energy scan of hadron production
Low energy scan of dilepton production with highest possible luminosity
How does the deconfined matter transform into hadrons?
Flavor dependence of spectra and collective flow
How are colliding nuclei converted into thermal quark-gluon plasma so rapidly?
Hard probes at forward rapidity
Question formulated at QCD workshop, Washington DC 12/2006
Axel Drees

Is the quark-gluon plasma the most perfect liquid? If not, what are its quasi particles?
What are the properties of new state of matter?
Temperature, density, viscosity, speed of sound, diffusion coefficient, transport coefficients ….
If it’s a fluid: What is the nature a relativistic quantum fluid?
If not: What is it and what are the relevant degrees of freedom?
Key are precision measurements with hard probes and of collective behavior currently not accessible at RHIC
 RHIC upgrades: improved detectors and increased luminosity
Axel Drees

Rutherford experiment
SLAC electron scattering a  atom discovery of nucleus e
 proton discovery of quarks
QGP penetrating beam
(jets or heavy particles) absorption or scattering pattern
Penetrating beams created by parton scattering before QGP is formed
High transverse momentum particles
 jets
Heavy particles
 open and hidden charm or bottom
Calibrated probes calculable in pQCD
Probe QGP created in A-A collisions as transient state after ~ 1 fm
Axel Drees

R
AA

Yield
AA
N Yield coll pp
0-12%
STAR
Status
Calibrated probe
Strong medium effect
Jet quenching
Reaction of medium to probe
(Mach cones, recombination, etc. )
Matter is very opaque
Significant surface bias
Limited sensitivity to energy loss mechanism trigger 2.5-4 GeV, partner 1.0-2.5 GeV hydro reaction of medium
Answers will come from jet tomography ( g -jet): single, two and three particle analysis loss mechanism?
vacuum fragmentation statistics (p
T reach)  increase luminosity and/or rate capability energy density?
 increase acceptance & add pid
What phenomena relate to reaction of media to probe?
Axel Drees

Medium reacting hadron < 5 GeV
g or
 0 trigger
W.Vogelsang NLO
RHIC II L = 20nb -1
LHC: 1 month run without
RHIC II
<z> ~ 0.1 for particles in recoil jet with RHIC II
RHIC II luminosities will give jets up to 50 GeV
 separation of medium reaction and energy loss
 sufficient statistics for 3 particle correlations p
T
 2-3 particle correlations with identified particles
> 5 GeV
Axel Drees

Electrons from c/b hadron decays Status
Calibrated probe?
pQCD under predicts cross section by factor 2-5
Factor 2 experimental differences in pp must be resolved
Charm follows binary scaling
Strong medium effects
Significant charm suppression
Significant charm v2
Upper bound on viscosity ?
Little room for bottom production
Limited agreement with energy loss calculations
What is the energy loss mechanism?
Where are the B-mesons?
Answers expected from direct charm/beauty measurements
Progress limited by: no b-c separation  decay vertex with silicon vertex detectors statistics (B  J/  )  increase luminosity and/or rate capability
Axel Drees

Detection options with vertex detectors:
•
•
Beauty and low p
•
Beauty via displaced J/

High p
T
T charm through displaced e and/or m charm through D
 
K
D 0
D
± m c t
GeV m m
1865 125
1869 317
X
B 0
B
±
PHENIX VXT ~2 nb -1 e
5279 464
5279 496
D
Au
Au
D
B
K

J/ 
X e e
RHIC II increases statistics by factor >10
Axel Drees

R
AA
Status
J/
 production is suppressed
Similar at RHIC and SPS
Consistent with consecutive melting of c and
 ’
Consistent with melting J/
 followed by regeneration
Recent Lattice QCD developments
Quarkonium states do not melt at T
C
Is the J/
 screened or not?
Can we really extract screening length from data?
J/

Answers require “quarkconium” spectroscopy
Progress limited by: statistics (  ’,  )  increase luminosity and/or rate capability
Axel Drees

Compiled by T.Frawley
Signal
| h
| or h
RHIC II 20 nb -1
PHENIX
<0.35, 1.2-2.4
STAR
<1
ALICE
<0.9, 2.5-4
LHC on month
CMS
<2.4
ATLAS
<2.4
J/
Y → mm or ee 440,000
Y ’→ mm or ee 8000 c c
→ mmg or ee g
120,000 *
 → mm or ee 1400
-
220,000
4000
-
390,000
7,000
11000** 6000
-
40,000 8K-100K
700
8000
-
140-1800
15,000
B → J/ Y → mm
( ee)
D → K 
8000
8000****
2500
30,000***
12,900
8,000 -
-
Luminosity ~ 10%
Running time ~ 25%
~ similar yields!
* large background
** states maybe not resolved
*** min. bias trigger
**** pt > 3 GeV
Will be statistics limited at RHIC II (and LHC!)
Axel Drees

 with TOF barrel
How does the deconfined matter transform into hadrons?
STAR AuAu 62.4 GeV
Status:
Elliptic flow (v2) v
2 of mesons and baryons scale with constituent quark number
Evidence for deconfined quarks
Hadronisation via recombination of constituent quarks in QGP
Progress from  s and flavor dependence of collective flow
Limited by: flavor detection capabilities s, c, b mesons and baryons
 vertex detectors and extended particle ID
Axel Drees

How are colliding nuclei converted into thermal quark-gluon plasma so rapidly?
Initial state and entropy generation.
What is the low x cold nuclear matter phase?
Status:
Intriguing hints for CGC
(color glass condensate) at RHIC
Bulk particle multiplicities
“mono jets” at forward rapidity eRHIC
STAR
RHIC
LHC
FAIR
Answers at RHIC from hard probes at forward rapidity, ultimately EIC needed
Progress at RHIC limited by: detection capabilities  forward detector upgrades
Axel Drees

2006 2009 2012 2015
RHIC
PHENIX & STAR upgrades
Vertex tracking, large acceptance, rate capabilities electron cooling “RHIC II” electron injector/ring “e RHIC”
LHC
FAIR
Phase III: Heavy ion physics
Axel Drees

On going effort with projects in different stages
forward meson spectrometer
DAQ & TPC electronics full ToF barrel heavy flavor tracker barrel silicon tracker forward tracker
STAR
PHENIX
EBIS ion source
Electron cooling (x10 luminosity) by 2008 at 200 GeV extra x10
Au+Au ~40 KHz event rate hadron blind detector muon Trigger silicon vertex barrel (VTX) forward silicon forward EM calorimeter
Completed, on going, proposal submitted, in preparation
Electron cooling at <20 GeV
Additional factor of 10
Au+Au 20 GeV ~15 KHz event rate
Au+Au 2 GeV ~150 Hz event rate
Axel Drees

and our experimental approach at RHIC
Is the quark-gluon plasma the most perfect liquid? If not, what are
RHIC energies
Is there a critical point in the QCD phase diagram and where is it
Low energy scan of dilepton production with highest possible
Flavor dependence of spectra and collective flow lattice QCD (e.g. finite density) new approaches (e.g. gauge/gravity correspondence)
Question formulated at QCD workshop, Washington DC 12/2006
Axel Drees

Axel Drees

General comparison to LHC
LHC and RHIC (and FAIR) are complementary
They address different regimes (CGC vs sQGP vs hadronic matter)
Experimental issues: “Signals” at RHIC overwhelmed by “backgrounds” at LHC
Measurement specific (compared to LHC)
Jet tomography: measurements and capabilities complementary
RHIC: large calorimeter and tracking coverage with PID in few GeV range
Extended p
T range at LHC
Charm measurements: favorable at RHIC
Abundant thermal production of charm at LHC, no longer a penetrating probe
Large contribution from jet fragmentation and bottom decay
Charm is a “light quark” at LHC
Bottom may assume role of charm at LHC
Quarkonium spectroscopy: J/

,
 ’ , c c easier to interpreter at RHIC
Large background from bottom decays and thermal production at LHC
Rates about equal; LHC 10-50 s
, 10% luminosity, 25% running timer
Low mass dileptons: challenging at LHC
Huge irreducible background from charm production at LHC
Axel Drees

Do we need (a) new heavy ion experiment(s) at RHIC?
Likely, if it makes sense to continue program beyond 2020
Aged mostly 20 year old detectors
Capabilities and room for upgrades exhausted
Delivered luminosity leaves room for improvement
Nature of new experiments unclear at this point!
Specialized experiments or 4
 multipurpose detector ???
Key to future planning:
First results from RHIC upgrades
Detailed jet tomography, jet-jet and g
-jet
Heavy flavor (c- and b-production)
Quarkonium measurments (J/

,
 ’ , 
)
Electromagnetic radiation (e + e
pair continuum)
Status of low energy program
Tests of models that describe RHIC data at LHC
Validity of saturation picture
Does ideal hydrodynamics really work
Scaling of parton energy loss
Color screening and recombination
New insights and short comings of RHIC detectors will guide planning on time scale 2010-12
Axel Drees

Key probe: electromagnetic radiation:
No strong final state interaction
Carry information from time of emission to detectors g and dileptons sensitive to highest temperature of plasma
Dileptons sensitive to medium modifications of mesons
(only known potential handle on chiral symmetry restoration!) e g * e +
Status
First indication of thermal radiation at RHIC
Strong modification of meson properties
Precision data from SPS, emerging data from RHIC
Theoretical link to chiral symmetry restoration remains unclear
Can we measure the initial temperature?
Is there a quantitative link from dileptons to chiral symmetry resoration? g
NA60 g
Answers will come with more precision data  upgrades and low energy running
Axel Drees

EBIS ion source
~30% higher
 with U+U
Luminosity increase at 200 GeV x4 above design achieved by 2008
Electron cooling at 200 GeV extra x10
Au+Au ~40 KHz event rate
Electron cooling at <20GeV
Additional factor of 10
Au+Au 20 GeV ~15 KHz event rate
Au+Au 2 GeV ~150 Hz event rate
Increase by additional factor 10 with electron cooling
T. Roser, T. Satogata
Axel Drees

Signal
| h
| or h
J/
Y → mm or ee
Y ’→ mm or ee
PHENIX
<0.35, 1.2-2.4
440,000
8000
STAR
<1
220,000
4000
ALICE
<0.9, 2.5-4
390,000
7,000
CMS
<2.4
40,000
700
Compiled by T.Frawley
ATLAS
<2.4
8K-100K
140-1800 c c
→ mmg or ee g
 → mm or ee
120,000 *
1400
-
11000**
-
6000
-
8000
-
15,000
B → J/ Y → mm ( ee) 8000
D → K 
8000****
2500
30,000***
12,900
8,000 -
-
-
-
Potential improvements with dedicated experiment
4
 acceptance J/
Y, Y ’
10x

2-10x background rejection c c
????
Note: for B, D increase by factor 10 extends p
T by ~3-4 GeV
Will be statistics limited at RHIC II (and LHC!)
LHC relative to RHIC
Luminosity ~ 10%
Running time ~ 25%
Cross section ~ 10-50x
~ similar yields!
* large background
** states maybe not resolved
*** min. bias trigger

NCC
HBD
NCC
VTX & FVTX
-3 -2 -1 0 1 2 3 rapidity
(i)  0 and direct g with combination of all electromagnetic calorimeters
(ii) heavy flavor with precision vertex tracking with silicon detectors combine (i)&(ii) for jet tomography with g -jet
(iii) low mass dilepton measurments with HBD + PHENIX central arms
Axel Drees

Upgrades
PHENIX hadron blind detector (HBD)
Vertex tracker (VTX and FVTX) m trigger forward calorimeter (NCC)
High T QCD e+eheavy jet flavor tomography quarkonia W
Spin
D G/G
X
X X O
O
O
O
X
X
O
O
STAR time of flight (TOF)
Heavy flavor tracker (HFT) tracking upgrade
Forward calorimeter (FMS)
DAQ
RHIC luminosity
O
X
O
O
X
O
O
X
O
O
X
X
O
O
O
O
O O O X X
X upgrade critical for success
O upgrade significantly enhancements program
O
Low x
O
X
X
O
O
Axel Drees

Initial conditions FAIR: cold but dense baryon rich matter fixed target p to U
 s
NN
~ 1-8 GeV U+U
Intensity ~ 2 10 9 /s

~10 MHz
~ 20 weeks/year
FAIR

T
C LHC 3-4 T
C
RHIC: dense quark matter to hot quark matter
Collider p+p, d+A and A+A
 s ~ 5 – 200 GeV U+U
NN
Luminosity ~ 8 10 27 /cm 2 s

~50 kHz
~ 15 weeks/year
RHIC

2 T
C
RHIC is unique and at “sweet spot”
LHC: hot quark matter
Complementary programs with large overlap:
High T: LHC
High r
: FAIR
 adds new high energy probes
 test prediction based on RHIC data
 adds probes with ultra low cross section
Collider p+p and A+A
Energy ~ 5500 GeV Pb+Pb
Luminosity ~ 10 27 /cm 2 s

~5 kHz
~ 4 week/year
Axel Drees

Key measurements require upgrades of detectors and/or RHIC luminosity
Detectors:
Particle identification  reaction of medium to eloss, recombination
Displaced vertex detection
 open charm and bottom
Increased rate and acceptance

Jet tomography, quarkonium, heavy flavors
Dalitz rejection
 e + e
pair continuum
Forward detectors
 low x,
CGC
Accelerator:
EBIS

Systems up to U+U
Electron cooling
 increased luminosity
Axel Drees

Central arms:
Electron and Photon measurements
Electromagnetic calorimeter
Precision momentum determination
Dalitz/conversion rejection (HBD)
Precision vertex tracking (VTX)
Hadron identification
PID (k,

,p) to 10 GeV (Aerogel/TOF)
Muon arms:
Muon
Identification
Momentum determination
High rate trigger ( m trigger)
Precision vertex tracking (FVTX)
Electron and photon measurements
Muon arm acceptance (NCC)
Very forward (MPC)
Axel Drees

Full Barrel
Time-of-
Flight system
DAQ and
TPC-FEE upgrade
Forward
Meson
Spectrometer
Integrated
Tracking
Upgrade
HFT pixel detector
Barrel silicon tracker
Forward triple-
GEM EEMC tracker
Forward silicon tracker
Axel Drees

T
LHC
Orders of magnitude larger cross sections
~3 times larger p
T range
RHIC with current detectors (+ upgrades)
Sufficient p
T reach
Sufficient PID for associated particles
What is needed is integrated luminosity!
Region of interest for associated particles up to p
T
~ 5 GeV
Axel Drees