Download - A CLASSICAL ODDERON IN HIGH ENEGY QCD
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A CLASSICAL ODDERON IN HIGH ENEGY QCD
A CLASSICAL ODDERON IN HIGH ENEGY QCD
Raju VenugopalanBNL
RBRC Workshop, Sept. 27th-29th, 2005
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Outline of talk:
The ground state of a large nucleus at high energies
Random walks & Path Integrals for SU(N) quarks
A “classical’’ Odderon
Results
Summary and Outlook
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Work in collaboration with Sangyong Jeon (McGill/RBRC)
A CLASSICAL ODDERON IN QCD AT HIGH ENERGIES. Sangyong Jeon, Raju Venugopalan Phys.Rev.D71:125003,2005
RANDOM WALKS OF PARTONS IN SU(N(C)) AND CLASSICAL REPRESENTATIONS OF COLOR CHARGES IN QCD AT SMALL X. Sangyong Jeon, Raju Venugopalan Phys.Rev.D70:105012,2004
Odderon paper inspired by
ODDERON IN THE COLOR GLASS CONDENSATE. Y. Hatta, E. Iancu, K. Itakura, L. McLerran Nucl.Phys.A760:172-207,2005
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ground state of a nucleus at high energies
Consider large nucleus in the IMF frame:
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Born-Oppenheimer: separation of large x and small x modes
Valence modes-are static sources for wee modes
DynamicalWee modes
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The effective action
Generating functional:
Gauge invariant weight functional describing distribution of the sources- W obeys RG ( B-JIMWLK) equations with
changing scale
Scale separating sources and fields
with
Focus in this talk on weight functional - for large nuclei
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Coarse grained field theory:
# of random quarks in box of size
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Well defined math problem:
Given k non-interacting quarks belonging the the fundamental SU(N) representation:
a) What is the distribution of degenerate irreducible representations?
b) What is the most likely representation?
c) Is it a classical representation ? N_c = Infinity is classical even for k=1
Random walk problem in space spanned by the n_c -1 Casimirs of SU(N)
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QCD IN THE LARGE A ASYMPTOTICS:
Evolution effects small =>
Kinematic region of applicability:
Kovchegov: Extend discussion to
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An SU(2) Random walk
Random walk of spin 1/2 partons:
In general,
= Multiplicity of representation s when k fundamental reps. are multiplied
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Binomial Coefficients satisfy:
Multiplicity satisfies:
with
Using Stirling’s formula, k >> s >> 1:
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Probability:
degeneracyof state
Mult. ofrepresentation
# degreesof freedom
Analogous to Maxwell-Boltzmann distribution
Casimir: Average value:
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PATH INTEGRAL:
Coarse graining -> Box of size 1/p_t in transverse plane
Sum over spins in box:
Classical color/spin density:
=>
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Summing over all boxes -> Classical path integral over SU(2) color charge density
Color charge squared per unit area- closely related to saturation scale.
For A >> 1, coupling runs as a function of this scale
McLerran, RVKovchegov
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Random walk of SU(3) Color charges
Denote SU(3) representations by (m, n) :
Recursion relation for SU(3) :
=
+ +
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= multiplicity of (m, n) state in the kth iteration
Trinomial coefficients:
Solution:
Again, use Stirling’s formula…
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Quadratic Casimir
Cubic Casimir
Probability:
Dimension of representation
Note:
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Prove:
Classical color charge:
Proof:
For any SU(3) representation,
Canonically conjugate “Darboux” variables
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Canonical phase space volume of SU(3): Johnson; Marinov;Alexeev,Fadeev,Shatashvilli
Hence,
Measure of probability integral has identical argument in m & n to RHS- hence can express in terms of LHS.
End of Proof.
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Path Integrals:
As in SU(2), with
MV Path integral measure for SU(3):
Generates Odderon excitations!
Path integral approach reproduces diagrammatic computations of dipole and baryon C= -1 operators
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Representations of order dominate for k >> 1
These representations are classical - can be represented by an SU(3) classical path integral
Can repeat analysis for gluon and quark-anti-quark pairs - only quadratic Casimir contributes…
Can add glue representations to quarks-result as for valence quarks - with larger weight.
To summarize…
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On to the Odderon…
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DIS:
IN CGC:
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Dipole Odderon operator:
Hatta et al.
To lowest order
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Can compute < O > with “SU(3) measure”
To lowest order,
To all orders (in the parton density)
Kovchegov, Szymanowski, Wallon
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3-quark Baryon state scattering off CGC
Dosch, Ewerz, Schatz
To lowest order,
All order result feasible, but tedious…
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Conclusions
The ground state of a large nucleus contains configurations that generate Odderon excitations - these can be traced to the random walk of valence partons in color space.
These results represent a “rigorous” proof in the large A asymptotics of QCD at high energies
Dipole Odderon and Baryon Odderon operators are computed
Phenomenological consequences - to be investigated further
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Why are higher dim. Reps. classical?
Invariance group or higher dim. rep.
Yaffe
For a system prepared in this state, uncertainity in mom. & position vanishes in this limit -> Coherent States
Gitman, Shelepin
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SU(N)
Can follow same recursion procedure…
Quadratic Casimir dominates: successive N-2 Casimirs parametrically suppressed by