Transcript Heavy Ion Physics Overview

The Science with
RHIC and Its Upgrade
W.A. Zajc
Columbia University
IUPAP WG-9 Symposium
July 2-3, 2010, TRIUMF
02-Jul-10
With my explicit thanks to
E. Aschenauer, A. Deshpande,
J. Dunlop, W. Fischer, J. Nagle,
E. O’Brien, K. Rajagopal,
T. Roser, S. Vigdor ;
and implicit thanks to all my colleagues at RHIC
W.A. Zajc
Assertion
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Fact

QCD is our prototypical non-Abelian
gauge theory
Amenable to experimental study at both
strong and weak coupling
Deep connections to other gauge theories

RHIC is the only facility dedicated to
the study of QCD
In the thermal regime
Using perturbative probes to study
non-perturbative phenomena
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U.S. Long Range Planning in Nuclear Science

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A source of considerable community pride
Something we’re good at
The plans are ‘resource burdened’
We’ve been at it for a long time:
1983
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1989
1996
2002
2007
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We’re Good at It and Have Been For a Long Time


A case in point –
the Relativistic Heavy Ion Collider (RHIC)
1983 Plan:
“We identify a relativistic heavy ion collider as the
highest priority for the next major facility to be
constructed, with the potential for addressing
a new scientific frontier of fundamental importance.”


2000: RHIC begins operations
2005: Announcement of major discoveries
at RHIC
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Discovery 2005
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2007 Long Range Plan Recommendation #4
The experiments at the
Relativistic Heavy Ion Collider have
discovered a new state of matter
at extreme temperature and density —
a quark-gluon plasma that exhibits
unexpected, almost perfect liquid
dynamical behavior.
• We recommend implementation of the
RHIC II luminosity upgrade, together with
detector improvements, to determine the
properties of this new state of matter.
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The RHIC Discovery
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A RHIC Mission
The RHIC Discovery
RHIC’s Bounty
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A RHIC Mission
Understand the spin
structure of the proton
SqDq
SqLq
DG
Lg

f1T
dq
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RHIC Spin

RHIC is the world’s only polarized proton
collider:
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RHIC Spin

RHIC is the world’s only polarized proton
collider:
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RHIC Spin


RHIC is the world’s only polarized proton
collider.
Use pQCD to study how the proton spin
is distributed among its constituents:
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pQCD at RHIC (I)

Establishing the validity of pQCD at RHIC
energies essential to both the spin and
the heavy ion programs:
STAR: PRL97, 252001 (2006)
PHENIX: PRD76
051106 (2007)
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pQCD at RHIC (II)

Spin: pQCD is
absolutely essential for
reliable, quantitative extraction
of polarized distribution functions
(next slide)

Heavy ions: pQCD is
absolutely essential for
reliable, quantitative
measurement
of “jet quenching”
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Gluon Contribution DG to Proton Spin

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
Dg(x)  g+(x) – g-(x)
In global analysis, RHIC data already play
dominant role in constraining Dg(x) for x < 0.2 :
Future measurements
2001
2005
with > x10 increase in
2008
integrated luminosity
RHIC
Greatly reduced errors
in putative(?) negative Dg(x)
Photons, heavy flavor
Di-hadron, jet-jet, g-jet
to provide direct
measurement of Dg(x)
x-dependence
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2012 ?
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Angular Momentum Contributions to Proton Spin

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Observation of large single spin transverse
asymmetries at large |xF| at RHIC:
Potential to understand
orbital motion of partons
in the proton
In particular
Test “non-universality”
of Sivers function
Clear prediction of sign
change between DIS and Drell-Yan
(D-Y to be measured at RHIC, luminosity hungry!)
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Sea Quark Contribution to Proton Spin
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Via “self-analyzing” W production (!)
2009: 500 Gev run: proof of principle (~10 pb-1)
First spin results (!)
Future:
10 pb-1  300 pb-1
PHENIX m trigger
STAR GEM tracker
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A RHIC Mission
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A RHIC Mission
The RHIC Discovery
“Perfect Liquid” behavior of the
quark-gluon plasma
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Expectations circa 2000
• RHIC would create
a quark-gluon plasma;
a “gas” of weakly
interacting
quarks and gluons
• As encoded in the Nuclear Physics Wall Chart,
• http://www.lbl.gov/abc/wallchart/
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2010 – First Temperature Measurement


PHENIX, PRL 104:132301, 2010
Ti ~ 300-500 MeV
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Clearly in Deconfined Regime

Ti ~ 400 MeV  quark and gluon d.o.f. “dominant”
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But - The Quark-Gluon Plasma is Not a Gas

Prejudice circa 2000:
Protons and neutrons
would ‘sublimate’ to a gas
of quarks and gluons
Much like dry ice
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
Discovery circa 2005
The quark-gluon plasma
is a nearly perfect liquid
Something like regular
ice to water
W.A. Zajc
Long Range Plan Recommendation
The experiments at the
Relativistic Heavy Ion Collider have
discovered a new state of matter
at extreme temperature and density —
a quark-gluon plasma that exhibits
unexpected, almost perfect liquid
dynamical behavior.
• We recommend implementation of the
RHIC II luminosity upgrade, together with
detector improvements, to determine the
properties of this new state of matter.
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Perfect Fluids
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
Perfect fluids are characterized by low viscosity.
Low viscosity requires strong coupling.
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Perfect Fluids

Perfect fluids are characterized by low viscosity.
Low viscosity requires strong coupling.

Precisely the region studied with RHIC energies.

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RHIC and the Phases of Nuclear Matter
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Heavy Ions at the LHC

Offers an unprecedented increase in energy:
RHIC sNN = 0.2 TeV
LHC sNN = 5.5 TeV
5.5 / 0.2 = 27.5 (!)

Estimate for change in initial temperature Ti :
Ti(LHC) = (27.5)1/4 Ti(RHIC) ~ 2.3 Ti(RHIC)
N.B.: LHC matter will still evolve through
‘RHIC’ temperature regime
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RHIC and LHC
RHIC
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LHC
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Two Scenarios

Scenario 1: Matter at LHC similar to RHIC
LHC will study with much higher Q2 probes

New observables  new discoveries
RHIC will study with greater flexibility in
Running time, energies and species
 Baseline (p+p) measurements
 Control (p+A, d+A) measurements


Scenario 2: LHC weakly-coupled,
RHIC strongly-coupled
LHC will probe fundamentally new regime
RHIC uniquely able to study strongly-coupled QGP
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The Future RHIC Program

“We recommend implementation of the RHIC II
luminosity upgrade…
Underway! (technological breakthrough)

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
~1/7 the cost
~ 4 years early
…together with detector improvements …
Underway

…to determine the properties of this new state
of matter.”
Thermodynamics, equation of state of perfect liquid
Search for the critical point in its phase diagram
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The “RHIC II” Luminosity Upgrade
•Y h+v pickups
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1/7 the cost
and 4 years early ?
Yes !
•B h+v kickers
Breakthrough –
stochastic cooling in a
bunched collider
•B h+v pickups
•Y h+v kickers
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The “RHIC II” Luminosity Upgrade


1/7 the cost
and 4 years early ?
Yes !
•14 Jan 2010
Breakthrough –
stochastic cooling in a
bunched collider
2010: RHIC operates at
~ 10 x design luminosity
Full stochastic cooling (2012)
provides 20 x design luminosity
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Building On Success

First decade of
RHIC Operations:
dramatic successes
pb-1
Achieved peak luminosities (100 GeV, nucl.-pair):
Au–Au
1551030 cm-2 s -1
p–p
501030 cm-2 s -1
Other large hadron colliders (scaled to 100 GeV):
Tevatron (p – pbar) 351030 cm-2 s -1
LHC (p – p, design) 1401030 cm-2 s -1
Operated modes (beam energies):
Au–Au 3.8, 4.6, 5.8, 10, 32, 65, 100 GeV/n
d–Au* 100 GeV/n
Cu–Cu 11, 31, 100 GeV/n
p–p 11, 31, 100, 250 GeV
Planned or possible future modes:
Au – Au 2.5 GeV/n (~ AGS cm energy)
p – Au* 100 GeV/n
(*asymmetric rigidity)
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“… together with detector improvements …”


Underway.
Examples:
PHENIX
Muon trigger (W’s)
 VTX (central Si)
 FVTX (forward Si)

STAR
Forward GEM tracker (W’s)
 Heavy Flavor Tracker

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“… to determine the properties of this
new state of matter.”


Example: How strong is the coupling ?
Surprising discovery: heavy flavor
(charm, perhaps bottom)
Loses energy in medium
Flows with the medium
despite MHF >> TQGP

The Si Vertex upgrades
+ “RHIC II” luminosities
will separate
the contributions of
b and c quarks
to this result
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QCD Condensed Matter

“Perfect Liquid” – a new state of matter (energy)
One that emerges from a fundamental Lagrangian
1 ~ m a
L  i D  Fa F m  Mˆ 
4
The ultimate condensed matter physics
No (?) dependence on ‘accidental’ scales like me/mp .
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“RHIC II” goal: to measure medium properties
Examples:
Debye screening length
Equation of state
Jet quenching ( dE/dx )
Shear viscosity
Bulk viscosity
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Shear Viscosity
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The ultimate “outreach” of
the ultimate condensed matter physics
Conjectured
quantum bound
of 1 / 4p
We need to firmly
establish RHIC
point(s)
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Current Status of h/s Extraction
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
To do:
Vary
s
Mass
Probe
(c, b)
Shape
( 238U )

Chaudhuri, arXiv:010.0979
Chaudhuri, arXiv:0909.0391
Luzum and Romatschke, arXiv:0804:4015
All
enabled by
upgraded
RHIC
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The Phases of QCD
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Transition to
QGP at
highest RHIC
energy is
“infinite order”
First-order
phase
transition
expected at
lower energy.
WHERE ?
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The QCD Critical Point

The landscape’s
key feature .
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RHIC uniquely
bridges
GSI  LHC
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The QCD Critical Point
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The landscape’s
key feature .
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RHIC uniquely
bridges
GSI  LHC
Requires RHIC to
be run as
low energy collider
Search via
non-monotonic
trends in
fluctuations
Search underway
Precision may
await further
luminosity
upgrades
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A RHIC Mission
The RHIC Discovery
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A RHIC Mission
The RHIC Discovery
RHIC’s Bounty
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Potential to study even more than
what has been presented here.
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Gluon Saturation
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Glue dominates the low-x structure of nucleons:
In nuclei,
saturation scale
Qs2 ~ A1/3 Q02 .
Naturally studied in
p+A and/or d+A collisions
Upgrades to STAR and PHENIX enable
“3rd ” RHIC program dedicated to saturation physics

Natural connection to
Initial state in A+A at RHIC (and LHC)
Electron Ion Collider (see talk by A. Deshpande)
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QCD Surprises

Local strong parity violation ?
STAR PRL 103:251601,2009
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Local Strong Parity Violation?

Requires
Strong magnetic field (~1017 G)
Deconfined quarks (plausible)
QCD topological charge (TBD)

Discovery requires
Elimination of all
mundane effects
Excitation function
Study in
Isobaric pairs (e.g., 9644Ru and 9640Zr)
 Asymmetric collisions (e.g., Cu+Au)

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The Big Picture

The strongly-coupled fluid at RHIC has created
unique ties to other fields:
AdS/QCD
Perfect liquid
AdS/CFT
Prediction of
h/s bound
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AdS/CMT
Cold atomic gases
Strongly correlated electrons
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The Bigger Picture

The AdS/CFT correspondence forges a fascinating
link between
Semi-classical gravity
Strongly-coupled gauge theories

In some sense,
it ‘works best’ when
Coupling is as strong as possible
System is thermal

RHIC !
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Summary

RHIC’s unparalleled versatility
Has led to major discoveries
Provides a dedicated environment for study of
Thermal QCD
 Spin structure of proton
 Saturation physics


Recent advances in
Luminosity and accelerator capability
Detector upgrades
establish a future program of extraordinary
promise.
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Thank You !
With my explicit thanks to
E. Aschenauer, A. Deshpande,
J. Dunlop, W. Fischer, J. Nagle,
E. O’Brien, K. Rajagopal,
T. Roser, S. Vigdor ;
and implicit thanks to all my colleagues at RHIC
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W.A. Zajc