Transcript The Long Range Plan for QCD

The Long Range Plan for QCD
Peter Jacobs, LBNL
DOE/NSF Charge to NSAC
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DOE/NSF Charge to NSAC cont’d
a.k.a. American Competitiveness Initiative (2006 State of the Union
Address)
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NSAC charge to DNP: Town Meetings
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QCD and Hadron Physics
S. Capstick L. Cardman, A.Deshpande, X. Ji,
C.Keppel, C. Meyer, Z. Meziani, J. Negele,
J.-C. Peng
Phases of QCD Matter
P. Jacobs, D. Kharzeev, B. Mueller, J. Nagle,
K. Rajagopal, S. Vigdor
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Background White Papers
Posted at: http://www.physics.rutgers.edu/np/2007lrp-home.html
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•
•
•
RHIC II
Electron Ion Collider
RHIC Theory Upgrade
LHC:
– ATLAS Heavy Ions
– CMS Heavy Ions
– ALICE-US
– LHeC (new proposal for electron ring in LHC tunnel)
• Accelerator R&D
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Summary of RHIC thus far
The
hottest (T~200-400 MeV)
densest (jet quenching: ei~30-60e0)
Matter (thermal yields)
W. Zajc
ever studied in the laboratory
Flows (large elliptic flow)
as a (nearly) perfect fluid
with systematic patterns consistent with
quark degrees of freedom (valence quark scaling)
and a viscosity to entropy-density ratio
lower (?) than any other known fluid, with a value near (?) a
conjectured quantum bound (h/s~2-3 x 1/4p)
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So are we done?
U. Heinz
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U. Heinz
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AdS/CFT: a startling development from string theory
Zajc, Kaplan
Conjecture: hidden within every non-Abelian gauge theory, even
within the weak and strong nuclear interactions, is a theory of
quantum gravity. (Horowitz and Polchinski, gr-qc/0602037 )
Has stimulated new directions in theory (e.g. lower bound on h/s
arises from basic quantum mechanics but was first derived in string
theory)
Potential connections to RHIC/LHC heavy ion physics: shear
viscosity, jet quenching, J/ suppression,…
But speculative at present: no testable calculations or predictions yet
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The interplay of RHIC and LHC
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•
U. Wiedemann
Together, RHIC and LHC span an energy range of more than
3 units of magnitude (say 50 GeV - 5.5 TeV).
How do the properties of hot and dense QCD matter evolve with
energy from RHIC to LHC?
Don’t trust the argument, that the high-temperature phase of QCD is featureless
above Tc. This may be true for the energy density, but:
- Measurable quantities related to 1st principle calculations, such as
qˆ
are likely to satisfy non-linear small-x evolution equations (similar to Qs)
- QCD measures of deviations from conformality
e  3p
change strongly from Tc to 3Tc. This may provide
crucial input for fundamental theoretical approaches
(e.g. string theory), which start from perturbations of a conformal framework

I advocate to identify this question now as a major scientific challenge of the
next decade, to be explored in an interplay of RHIC and LHC. Consequence:
RHIC luminosity upgrade also motivated by increasing kinematical reach for
comparison with LHC.
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
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Big Questions for an e+p/A collider
Vogelsang, Ent, Kovchegov, Surrow,…
EIC: polarized e+p, unpolarized e+A
Broad theme: precision studies of emergent features of QCD
What are the momentum distributions of quarks, anti-quarks and gluons in
the nucleon?
What symmetries (flavor, isospin) hold or are broken in the nucleon?
How are quarks and gluons distributed spatially in the nucleon?
What is the nature of glue at high density?
– How do strong fields appear in hadronic or nuclear wave functions at
high energies?
– What are the appropriate degrees of freedom?
– How do they respond to external probes or scattering?
– Is this response universal (ep, pp, eA, pA, AA)?
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Proposed EIC Designs
eRHIC
L = 2.6x1033 cm-2s-1
Ecm = 140 GeV
ELIC (JLab)
L = 7.7x1034 cm-2s-1
Ecm = 65 GeV
L. Merminga
LHeC
L = 1.1x1033 cm-2s-1
Ecm = 1.4 TeV
L = 0.47x1033 cm-2s-1
Ecm = 100 GeV
Luminosities are for e-p collisions
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Summary of EIC candidates
L. Merminga
eRHIC ERL
eRHIC R-R
ELIC
LHeC
25-140
30-100
20-65
1400
p,.., 238U
positrons
p,.., 238U
positrons
p, .., 40Ca
positrons
p,
positrons
yes
yes
yes
Not
planned
Up to 4
1 (2*)
4
1
IR free space
[m]
±5
±1
±2 (up to ±3)
1.2
Lpeak
[cm-2 sec-1]
2.6x1033 **
0.47x1033
7.7x1034
1.1x1033
ECM [GeV]
Species
Polarization
p,D,3He,e-,e+
Number of
IR’s
*Requires second ring **one IR
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Physics reach of eRHIC: F2(x,Q2)
sea quarks generated by glue
Th. Ullrich
2

d 2 epeX 4p 2 
y2 
y
2
2
1  y   F2 ( x, Q )  FL ( x, Q )

2
4 
2
2
dxdQ
xQ 

• F2 will be one of the first
measurements at EIC
• nDS, EKS, FGS: pQCD
models with different
amounts of shadowing
EIC will distinguish between
pQCD and saturation model
predictions
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FL at eRHIC: direct measurement of glue
Th. Ullrich
EIC: (10+100) GeV
Ldt = 2/A fb-1

d 2 epeX 4p 2 
y2 
y2
2
2



1

y

F
(
x
,
Q
)

F
(
x
,
Q
)


2
L
2 
2
dxdQ2
xQ4 

Q2/xs = y
Needs s scan
2
EIC will
G(x,Q
Themeasure
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for QCD) precisely
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Phases of QCD: Recommendation #1
1. Our central goal is a dramatic advance in our understanding of QCD
Matter, through quantitative comparison of theory and experiment to
determine the properties of the strongly interacting Quark-Gluon
Plasma discovered in the initial phase of RHIC operations, and through
further exploration of the QCD phase diagram at non-zero baryon
density where a critical point has been predicted. The essential
requirements for the success of this scientific program are therefore our
highest priorities:
• Effective utilization of the RHIC facility and completion of the ongoing
detector upgrade program;
• The RHIC II luminosity upgrade, which will enable quantitative study of rare
processes;
• Strong support for the ongoing theoretical studies of QCD matter, including
finite temperature and finite baryon density lattice QCD studies and
phenomenological modeling, and an increase of funding to support new initiatives
enabled by experimental and theoretical breakthroughs.
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Phases of QCD Recommendation #2: LHC
2. We strongly recommend significant and timely participation of
U.S. groups in the LHC heavy ion program, which will study QCD
matter at the highest energy densities and temperatures available in
the laboratory. This program will test and extend the insights
reached in the RHIC program, and has the potential to make
important new discoveries about QCD Matter.
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Phases of QCD Recommendation #3: EIC
Same EIC bullet will appear in “Phases of QCD Matter” and
“Hadronic Physics” Summary White Papers (minor modifications
not yet finalized)
3. An Electron-Ion Collider (EIC) facility is the highest priority of
the QCD community for new construction after the JLab 12 GeV
and the RHIC II luminosity upgrades. EIC will address compelling
physics questions essential for understanding the fundamental
structure of matter:
• Precision imaging of sea-quarks and gluons to determine the
full spin, flavor and spatial structure of the nucleon;
• Definitive study of the universal nature of strong gluon fields
manifest in nuclei.
This goal requires that R&D resources be allocated for expeditious
development of collider and
experimental design.
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Further recommendations
Still to be written:
4. Common theory bullet (the bullet is common, not the theory)
5. Education and Outreach
6. Accelerator R&D
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What happens next?
Summary White Paper from each Town Meeting,
• presents and justifies priorities (bullets)
• first draft in early March
Status reports and discussion at NSAC meeting March 8-9
Status reports at Spring APS Meeting, Jacksonville, April 14-17
(session U2, Monday p.m.)
The smoke-filled room: Long Range Plan “Resolution
Meeting”, Galveston TX, April 30-May 4
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