Color glass condensate and its relation to HERA physics

Iancu, Edmond

doi:10.1016/j.nuclphysbps.2009.03.135

Cited by 14 publications

(13 citation statements)

References 94 publications

(99 reference statements)

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“…The terms linear in A(Y, k) in this equation represent the BFKL equation, whereas the last, quadratic, term is responsible for gluon saturation. One can roughly think about this last term as describing the recombination of two gluons into one, but this picture is quite crude: the actual non-linear phenomena responsible for gluon saturation are much more complex and should be rather viewed as the blocking of new gluon emissions by strong color fields [29]. Since this equation is non-linear, we should be more specific about the normalization of the function A(Y, k).…”

Section: Unitarity and Saturation Momentummentioning

confidence: 99%

“…The BFKL formalism, properly generalized to include the non-linear effects responsible for gluon saturation [11,12,27,28,29], is specially tailored to describe the evolution of the unintegrated gluon distribution with increasing energy and its approach towards saturation. As such, this is well-suited to study the high-energy evolution of inclusive cross-sections, and it is able to accommodate important phenomena, like the geometric scaling at HERA [16,22,23], or the turnover in the DIS structure function F 2 (x, Q 2 ) at semi-hard Q 2 [17,18].…”

Section: Introductionmentioning

confidence: 99%

“…The dependence of Qs(Y ) upon Y is such that the physical occupation number at k Qs(Y ) grows linearly with Y ; that is, what saturates is the rate for gluon emission[29] 8. In particular, for extremely high k ≫ Qs(Y ), the BFKL distribution approaches the bremsstrahlung spectrum, A(Y, k) ∼ 1/k 2 , whereas at moderate k this is modified by the BFKL 'anomalous dimension' 9.…”

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confidence: 99%

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CCFM evolution with unitarity corrections

Avsar

Iancu

2009

Nuclear Physics A

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We considerably extend our previous analysis of the implementation of an absorptive boundary condition, which mimics saturation effects, on the linear CCFM evolution. We present detailed results for the evolution of the unintegrated gluon density in the presence of saturation and extract the energy dependence of the emerging saturation momentum. We show that CCFM and BFKL evolution lead to almost identical predictions after including the effects of gluon saturation and of the running of the coupling. We moreover elucidate several important and subtle aspects of the CCFM formalism, such as its relation to BFKL, the structure of the angular ordered cascade, and the derivation of more inclusive versions of CCFM. We also propose non-leading modifications of the standard CCFM evolution which may play an important role for phenomenological studies.

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Section: Unitarity and Saturation Momentummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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CCFM evolution with unitarity corrections

Avsar

Iancu

2009

Nuclear Physics A

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“…Once the density is too large however, one needs to take into account the non-linear effects. The BFKL evolution is modified in the high density limit by the so-called Color Glass Condensate (CGC) [9,10] (for a review see [11][12][13][14][15]) formalism where the strong color fields are treated semi-classically, and where their presence leads to the saturation of the gluon emission rate. 1 The BFKL evolution equation is then generalized to either the Balitsky-Kovchegov (BK) [16,17] equation or to the more complete JIMWLK [18][19][20][21][22][23][24][25] equation.…”

Section: Introductionmentioning

confidence: 99%

Non-linear evolution in CCFM: the interplay between coherence and saturation

Avsar

Staśto

2010

J. High Energ. Phys.

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Abstract:We solve the CCFM equation numerically in the presence of a boundary condition which effectively incorporates the non-linear dynamics. We retain the full dependence of the unintegrated gluon distribution on the coherence scale, and extract the saturation momentum. The resulting saturation scale is a function of both rapidity and the coherence momentum. In Deep Inelastic Scattering this will lead to a dependence of the saturation scale on the photon virtuality in addition to the usual x Bj dependence. At asymptotic energies the interplay between the perturbative non-linear physics, and that of the QCD coherence, leads to an interesting and novel dynamics where the saturation momentum itself eventually saturates. We also investigate various implementations of the "non-Sudakov" form factor. It is shown that the non-linear dynamics leads to almost identical results for different form factors. Finally, different choices of the scale of the running coupling are analyzed and implications for the phenomenology are discussed.

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“…Recently, we have suggested that highly resolved and cold string with a number of quanta N ≡ 1/x can be used to account for low-x non-perturbative physics [9]. Perturbative low-x physics based on the color glass condensate has been discussed by many [24][25][26][27][28][29][30][31][32][33][34][35][36].One of the most remarkable feature of free strings is the exponential growth with their mass of the degeneracy in their spectra, which translates to a constant entropy to mass ratio [37,38]. Excited strings offer a very efficient way to scramble information and create entropy.…”

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confidence: 99%

Stretched string with self-interaction at the Hagedorn point: Spatial sizes and black holes

Qian

Zahed

2015

Phys. Rev. D

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We analyze the length, mass and spatial distribution of a discretized transverse string in D ⊥ dimensions with fixed end-points near its Hagedorn temperature. We suggest that such a string may dominate the (holographic) Pomeron kinematics for dipole-dipole scattering at intermediate and small impact parameters. Attractive self-string interactions cause the transverse string size to contract away from its diffusive size, a mechanism reminiscent of the string-black-hole transmutation. The string shows sizable asymmetries in the transverse plane that translate to primordial azimuthal asymmetries in the stringy particle production in the Pomeron kinematics for current pp and pA collisions at collider energies. I. INTRODUCTIONRecent high multiplicity events in pA and pp collisions at the LHC [1-3] have revealed some similarities with heavy ion collisions at ultra-relativistic energies: 1) a prompt and large entropy deposition; 2) a large radial and elliptic flow. The results have renewed the interest in the formation of a fireball and the relevance of hydrodynamics in small hadronic collisions at high energy [4][5][6][7][8]. The purpose of this paper is to explore this idea further by using self-interacting strings close to their Hagedorn point. This study complements our recent investigation of cold and self-interacting strings at low-x [9].Hadron collisions at high energies are dominated by soft Pomeron and Reggeon exchanges. The Pomeron is an effective 0 ++ exchange corresponding to the highest Regge trajectory. Its small intercept α P (0) − 1 ≈ 0.08 is used to explain the small growth of the hadron-hadron cross section at large √ s with the rapidity interval χ = ln(s/s 0 ) in the context of Reggeon calculus [10][11][12][13]. First principle perturbative QCD calculations describes a harder Pomeron by re-summing the soft collinear Bremshtralung with a larger intercept and zero slope [14,15].Non-perturbative arguments based on duality suggests that the soft Pomeron involves a closed string exchange in the t-channel. The string world-sheet could be thought as a fishnet of planar gluon diagrams in QCD in the large number of colors limit. The quantum theory of planar diagrams in the double limit of strong coupling and large number of colors is tractable in supersymmetric theories using the holographic principle [16]. Many descriptions of the soft Pomeron in holographic duals to QCD have been suggested without supersymmetry, reproducing a number of results in both DIS and diffractive scattering [4,9,[17][18][19][20][21][22][23]. Recently, we have suggested that highly resolved and cold string with a number of quanta N ≡ 1/x can be used to account for low-x non-perturbative physics [9]. Perturbative low-x physics based on the color glass condensate has been discussed by many [24][25][26][27][28][29][30][31][32][33][34][35][36].One of the most remarkable feature of free strings is the exponential growth with their mass of the degeneracy in their spectra, which translates to a constant entropy to mass ratio [37,38]. Excited...

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Color glass condensate and its relation to HERA physics

Cited by 14 publications

References 94 publications

CCFM evolution with unitarity corrections

CCFM evolution with unitarity corrections

Non-linear evolution in CCFM: the interplay between coherence and saturation

Stretched string with self-interaction at the Hagedorn point: Spatial sizes and black holes

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