Evidence for BFKL and saturation dynamics from di-hadron spectra at the LHC

Kevin Dusling; Raju Venugopalan

REVIEW

Evidence for BFKL and saturation dynamics from di-hadron spectra at the LHC

Kevin Dusling, Raju Venugopalan

High Energy Physics - Phenomenology · Submitted 15 Oct 2012 · 51 references

Pith's verdict: The fullest statement of the Dusling–Venugopalan Glasma+BFKL program; the p+p agreement is a shape result with a fitted normalization, but the p+Pb predictions are the real content and they were falsifiable.

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arXiv ID1210.3890 (version 3)

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CitationKevin Dusling, Raju Venugopalan. "Evidence for BFKL and saturation dynamics from di-hadron spectra at the LHC." arXiv:1210.3890 (2012). https://pith.science/paper/RYWO4TGI

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Editor's note

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The thing to know: this is the fullest statement of the Dusling–Venugopalan Glasma+BFKL program for the p+p ridge, and the part worth your time is not the p+p agreement but the p+Pb predictions in Figs. 3 and 5, which were made before the data existed and can be checked against it. That is the paper's real content, and it is why the paper has legs regardless of how the p+p fit is judged. On what is new: Eq. (3) adds the subleading Glasma diagrams, which drop the required K-factor from 2.3 to 1. That matters, because K=1 with ζ fixed elsewhere is a prediction rather than a fit. Eq. (5) applies the BFKL Green's function across the full pTtrig/pTasc matrix, well beyond the Mueller–Navelet regime where it is usually deployed. On the soft spots, in proportion: the impact-factor-equals-UGD identification in Eq. (5) is stated as an ansatz, not derived, and it sets the away-side normalization. The near-side BFKL piece is conjectured flat (fn. 34), and the authors say outright they do not trust BFKL there. ζ ~ 1/6 is non-perturbative and borrowed. The treatment is LLx only, with the NLLx argument resting on C1, C2 ratios from Colferai et al. And the Ntrig ≥ 2 caveat is honest but consequential: they admit the theory undershoots at high pTtrig and that imposing the cut would push it the right way, which means the high-pT end is not really tested. On the stress test: the K=1 vs K=2.3 point is real but narrower than it sounds. Fig. 2 is the near-side yield at K=1, which is the prediction. Fig. 4 uses K_Glasma=2.3 because the small near-side BFKL anticollimation has to be compensated to hold the near-side total fixed; fn. 39 says exactly that. So it is one prediction plus one display choice, not two contradictory normalizations of the same calculation. And Fig. 3 inherits the K=1 normalization, not the 2.3, so the min-bias-versus-central p+Pb ratio is not hostage to that shift. The stress test's extension to Fig. 3 does not land. Who it is for: small-x and CGC people, and anyone who wants the initial-state alternative to hydro on record for the ridge. It is a Letter; the machinery lives in Refs. [11] and [13]. Recommendation: send it out. It is a serious paper with acknowledged gaps, and the predictions have already earned it a hearing.

Referee report

Significance

If it holds, the result is important: it would tie two of the most-discussed LHC small-system observables to a single weak-coupling CGC framework, with no hydrodynamic medium, and it makes concrete, falsifiable predictions for p+Pb that the LHC could test shortly after publication. The paper is also commendably explicit about its own soft spots — the impact-factor ansatz below Eq. (5), the flat near-side BFKL conjecture in footnote 34, the ζ uncertainty in footnote 33, and the missing N_trig >= 2 cut — which makes the argument assessable rather than rhetorical. The reduction of the previously required K = 2.3 to K = 1 by adding the subleading Glasma diagrams is a genuine, checkable improvement over Ref. [11], and the p+Pb predictions in Figs. 3 and 5 are the kind of statement that can be confirmed or excluded.

Major objections (4)

[Figs. 2 and 4, footnotes 34 and 39] The same Glasma contribution carries two different normalizations within this Letter: the text below Eq. (3) states that including Eq. (3) 'lowers the K-factor from K = 2.3 required previously in [11] to K = 1', and Fig. 2 is presented on that basis, whereas the Fig. 4 caption uses K_Glasma = 2.3 together with K_BFKL = 1.1. Footnote 39 attributes the shift to a 'small nearside anticollimation' from BFKL, and footnote 34 concedes that 'BFKL predictions are not of this accuracy' and that a flat near-side BFKL contribution is a conjecture. As it stands, the near-side agreement in Fig. 2 and the away-side agreement in Fig. 4 rest on normalizations of the same Glasma term that differ by a factor 2.3, with the choice between them controlled by a piece the authors say they cannot compute reliably. The manuscript should state explicitly, in the main text rather than only in footnotes, which K-factor applies to which figure and why, and should quantify the size of the near-side BFKL anticollimation that drives the change. Without that, the word 'quantitatively' in abstract:s0 describes a shape agreement with a fitted, non-unique normalization.
[Eq. (5) and the ansatz below it] The identification of the BFKL impact factors Φ in Eq. (5) with the BK-evolved unintegrated gluon distributions of Eqs. (1) and (3) is stated as an ansatz ('we will make the ansatz here that the Φ's are equivalent to the unintegrated gluon distributions'), and this identification fixes both the normalization and the shape of the entire away-side contribution in Fig. 4. The agreement in Fig. 4 is therefore a consistency check of the ansatz, not an independent confirmation of BFKL dynamics. The manuscript should either provide a parametric argument for why the impact factors reduce to the UGDs at the kinematics probed (x ~ 10^-4 to 10^-5, p_T of a few GeV), or show the sensitivity of Fig. 4 to a modest variation of the impact factor — for example a different scale choice or a different UGD set — so the reader can judge how much of the agreement is carried by the ansatz. A short sensitivity panel or a stated fractional uncertainty would materially strengthen the central claim.
[Fig. 3, footnotes 36 and 37] The p+Pb predictions inherit the full normalization freedom of the p+p calculation, and the central qualitative message of Fig. 3 — that the minimum-bias p+Pb ridge is smaller than the central p+p ridge, and that the central p+Pb ridge is smaller still — is a ratio of Glasma yields computed with Q_0^2 = 0.504 and 1.008 GeV^2 for lead. Footnote 36 describes these values as '(imperfectly) constrained'. Because the predicted ordering is a ratio of quantities that scale with Q_0, the manuscript should show how the ordering in Fig. 3 responds to a reasonable variation of Q_0 (say a factor of two either way) and of ζ. If the ordering survives such variation, the prediction is much stronger; if it does not, the text should say so. As written, the reader cannot tell whether the ordering is a robust prediction or a consequence of the specific Q_0 choices.
[Fig. 4 and the surrounding text] The statement that 'the BFKL result gives a good agreement with awayside data in the entire matrix' is made for a curve that is the sum of BFKL and Glasma contributions with K_BFKL = 1.1 and K_Glasma = 2.3. The text asserts that the Glasma awayside contribution 'is small' but does not quantify it. Since the away-side agreement is one of the two pillars of the paper, the manuscript should state, per p_T bin or at least for representative bins, what fraction of the away-side yield comes from the Glasma term, and should show the BFKL-only curve alongside the sum. Otherwise the reader cannot separate the BFKL success from the Glasma normalization.

Minor objections (7)

[Footnote 39] The footnote ends with the dangling cross-reference 'See footnote .' with no number; this should be completed or removed.
[Eq. (1) and footnote 33] The non-perturbative constant ζ enters the overall normalization C_2 of Eq. (1) but its value and allowed range are deferred entirely to Ref. [11] and footnote 33. Since ζ ~ 1/6 is a factor in the same normalization that the K-factors absorb, it would help to state the numerical value used and the range over which the results are stable, so that the reader can see how much of the K-factor is really ζ.
[Footnote 16] The smearing δ(φ_pq) -> (1/√(2π)σ) exp(-φ_pq^2/2σ^2) with σ = 3 GeV/p_T should be stated to be dimensionless (i.e., in radians), and the claim that the associated yield is insensitive to the smearing details should be supported by at least one quoted number, for example the change in the integrated near-side yield for σ varied by a factor of two.
[Text below Eq. (3) and Fig. 2] The authors note that they cannot impose N_trig >= 2 as the CMS analysis does, and argue that imposing it 'would harden the spectrum in the correct direction'. This is plausible but should be made quantitative if possible, for example by reweighting the calculated spectrum with a measured multiplicity distribution, since the systematic under-prediction at high p_T^{trig} is one of the few visible discrepancies in Fig. 2.
[Figs. 2, 3, 4, 5] None of the theory curves carries an uncertainty band. Given the acknowledged freedom in ζ, Q_0, and the renormalization and energy scales entering the running coupling, a shaded band from a modest parameter variation would communicate the theory status far better than single curves, and would also make the p+Pb predictions in Figs. 3 and 5 more useful to experimentalists.
[General notation] The transverse momentum labels appear inconsistently through the manuscript (p_T^{trig}, p_trigT, p_T^{asc}, p_ascT). A single consistent notation in the final version, matching the CMS conventions, would make the figures and the p_T matrix easier to follow.
[Text below Eq. (6)] The argument that LLx is adequate because the NLLx corrections to C_1 and C_2 are only ~10% and ~30% is reasonable, but it is drawn from Ref. [23] at ΔY >= 6 whereas the CMS kinematics here extend to |Δη| <= 4. The manuscript should state explicitly the ΔY range over which the quoted NLLx/LLx comparison was made and why it applies here.

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The paper

The paper claims

High-multiplicity proton-proton collisions show both a near-side ridge and an away-side angular decorrelation; the paper argues that gluon saturation plus BFKL gluon-ladder resummation together reproduce the measured di-hadron spectra with,

The reading

When the LHC collides protons at high multiplicity, it produces two features in pairs of hadrons separated by two to four units of rapidity: a narrow near-side collimation called the ridge, and an away-side peak whose angular correlation is more washed out than simple two-body scattering would give. This paper argues that both follow from perturbative QCD at small momentum fraction $x$ with no medium at all. The ridge comes from Glasma graphs, the leading two-gluon correlations of the Color Glass Condensate effective theory; the away side comes from back-to-back partons joined by a ladder of rapidity-ordered gluon emissions resummed by the BFKL equation. Adding the two and comparing to the full CMS associated-yield matrix in trigger and associated transverse momentum, the authors find agreement with normalization factors of order one once the sub-leading Glasma diagrams are included. If that reading holds, the same machinery should say what happens when a proton hits a lead nucleus, and the paper turns that into concrete predictions for the forthcoming proton-lead run.

What carries the argument

Two objects carry the argument. The first is the Glasma graph: the leading-power expression for correlated two-gluon production in the Color Glass Condensate, written as a convolution of unintegrated gluon distributions $Phi(y,k_T)$ taken from the same hadron at two rapidities, with $Phi$ obtained by solving the Balitsky-Kovchegov equation. The second is the BFKL Green's function $G(q_a,q_b,Delta y)$ of Eq. (6), which sums leading logarithms in $x$ between the two tagged partons and so converts a fixed-order back-to-back cross-section into one that decorrelates in azimuth as the rapidity gap grows. The bridge between them is an explicit ansatz: the BFKL impact factors are taken to equal the same BK-evolved unintegrated gluon distributions used in the Glasma graphs, so that one set of distributions, evolved from a single initial scale $Q_0^2$, fixes both the near-side and the away-side normalizations. The comparison is done in the zero-yield-at-minimum associated yield per trigger, a ratio in which the transverse overlap area cancels and azimuth-independent backgrounds drop out.

Extended reading notes

Core claim

The claim is that a single perturbative framework, saturation plus BFKL, quantitatively reproduces the rapidity-separated di-hadron spectra measured by CMS in high-multiplicity $p+p$ collisions at $7$ TeV, on both the near side and the away side. On the near side, the Glasma graphs of Eqs. (1) and (3) carry the ridge; adding the formally sub-leading diagrams of Eq. (3) lowers the previously needed normalization from $K=2.3$ to $K=1$, which the authors present as the main improvement over their earlier letter. On the away side, the back-to-back contribution of Eq. (5), built from a BFKL Green's function that resums logarithms of $x$ between the tagged partons, describes the measured associated yield across the whole trigger and associated $p_T$ matrix with $K_{BFKL}=1.1$ and $K_{Glasma}=2.3$, and does visibly better than the same calculation with the gluon radiation switched off (multi-Regge kinematics) or with only the $gg o gggg$ quasi-multi-Regge matrix element. From this the authors predict that minimum-bias $p+Pb$ collisions at $5.02$ TeV will show a ridge smaller than that in central $p+p$, that central $p+Pb$ will show a larger ridge than minimum-bias $p+Pb$ but still a smaller one than central $p+p$, and that the away-side yield per trigger in $p+Pb$ will follow the BFKL systematics they plot.

Load-bearing premise

The away-side argument rests on an explicitly stated ansatz, that the BFKL impact factors are the same objects as the BK-evolved unintegrated gluon distributions used in the Glasma graphs, so if those two quantities differ in shape or normalization the away-side agreement across the transverse-momentum matrix is not actually grounded.

Editorial extensions

If this is right

Minimum-bias $p+Pb$ collisions at $sqrt{s}=5.02$ TeV should show a near-side ridge, smaller than the central $p+p$ ridge in the same associated-$p_T$ windows.
Central $p+Pb$ collisions should show a larger ridge than minimum-bias $p+Pb$ but still a smaller one than central $p+p$, with the ordering controlled only by the initial scale $Q_0^2$ of the BK evolution.
The away-side yield per trigger in $p+Pb$ should follow the BFKL-driven systematics of Fig. 5, so that the same ladder resummation that fits $p+p$ transfers to a nuclear target.
Extending the comparison to dijet rather than dihadron production, where the rapidity acceptance at the LHC is wider, should sharpen the separation between BFKL evolution and fixed-order multi-Regge descriptions.
If the description holds, the ridge in small systems needs no collective medium: saturation-driven two-gluon correlations plus BFKL bremsstrahlung between the tagged partons suffice.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The same bookkeeping suggests a clean experimental discriminator against medium-based pictures: the ridge yield should scale with the saturation scale of the colliding objects rather than with any final-state density, so a systematic scan across proton, minimum-bias lead, and central lead is a sharper test than any single collision species.
Because the away-side agreement runs the BFKL ladder over rapidity gaps far beyond the Mueller-Navelet regime, the calculation doubles as an indirect probe of whether leading-log BFKL is still adequate at rapidity separations of three to four units, which dijet measurements at wider acceptance could check independently.
The non-perturbative constant $zeta$ and the smearing of the near-side delta function are the two places where a genuinely non-perturbative number enters an otherwise weak-coupling calculation; a sharper determination of $zeta$ would convert the order-unity normalizations quoted here into a parameter-free comparison.
If the impact-factor-equals-unintegrated-gluon-distribution ansatz is the weak link, a future next-to-leading-log impact factor calculation would shift the away-side normalization without touching the near side, showing up as an inconsistency between the two normalizations extracted from the same data set.

Original abstract

We demonstrate that rapidity separated di-hadron spectra in high multiplicity proton-proton collisions at the LHC can be quantitatively described by a combination of BFKL and saturation dynamics. Based on these results, we predict the systematics of di-hadron spectra in proton-nucleus collisions at the LHC.

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The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 2,304 input tokens, $0.0001 reported.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.05 · human participants 0.02 · controlled comparison 0.05 · randomized assignment 0.01 · states quantitative result 0.09 · compares with prior results 0.12 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v3. Results and the main claim are underlined; show every role.

We demonstrate that rapidity separated di-hadron spectra in high multiplicity proton-proton collisions at the LHC can be quantitatively described by a combination of BFKL and saturation dynamics. Based on these results, we predict the systematics of di-hadron spectra in proton-nucleus collisions at the LHC.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We demonstrate that rapidity separated di-hadron spectra in high multiplicity proton-proton collisions at the LHC can be quantitatively described by a combination of BFKL and saturation dynamics.	result 0.96	0.92	0.92	asserted 1.00
s1	Based on these results, we predict the systematics of di-hadron spectra in proton-nucleus collisions at the LHC.	contribution 0.33	0.71	0.11	asserted 0.93

What kind of paper the classifier reports this is: theoretical result 0.70 · evidence from analysis of existing data 0.81.

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sources read

arXiv listing abstract v3

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full text
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relations to other papers

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T body sentences
C citations
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Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures

**Figure 1.** FIG. 1. Anatomy of di-hadron correlations. The glasma graph

**Figure 2.** FIG. 2. The integrated associated nearside yield per trigge

**Figure 3.** FIG. 3. The associated yield per trigger as a function of

**Figure 4.** FIG. 4. CMS data after the removal of the underlying event in e

**Figure 5.** FIG. 5. BFKL prediction for the away-side yield in minimum bi

Figures reproduced from arXiv:1210.3890 by the authors.

References

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Forward citations

Cited by 33 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

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hep-ph 2017-05 conditional novelty 7.0 of 10

Initial-state scattering of projectile quarks off color domains in the target reproduces the ordering and energy behavior of two-, four-, six- and eight-particle azimuthal harmonics measured in proton-nucleus collisions.
Azimuthal anisotropies in p+Pb collisions from classical Yang-Mills dynamics
hep-ph 2015-02 conditional novelty 7.0 of 10

In classical Yang-Mills simulations of p+Pb, gluon v2 is present at the initial time from color-field domain structure, v3 is generated dynamically within 0.4 fm/c, and neither tracks the global collision geometry.
Observation of long-range near-side angular correlations in proton-lead collisions at the LHC
nucl-ex 2012-10 accept novelty 7.0 of 10

High-multiplicity proton-lead collisions at the LHC show a long-range near-side ridge correlation, the first such observation in a proton-nucleus system.
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hep-ph 2016-07 conditional novelty 6.0 of 10

The mass ordering of mean transverse momentum and elliptic flow in high-multiplicity proton-proton collisions emerges from initial-state gluon correlations plus string fragmentation, without hydrodynamic flow.
Evidence for collectivity in pp collisions at the LHC
nucl-ex 2016-06 accept novelty 6.0 of 10

High-multiplicity proton-proton collisions at 5, 7 and 13 TeV show azimuthal anisotropy harmonics whose four- and six-particle cumulants match the two-particle values, the pattern expected if a collective fluid forms.

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hep-ph 2015-09 conditional novelty 6.0 of 10

The color field domain model used to explain azimuthal correlations in proton-nucleus collisions is shown to be equivalent to non-Gaussian correlations of color electric fields in the color glass condensate.
Evidence for collective multi-particle correlations in pPb collisions
nucl-ex 2015-02 conditional novelty 6.0 of 10

Six- and eight-particle cumulants and Lee-Yang zeros give v2 values in pPb collisions that agree with the four-particle result within 10%, supporting a collective origin for long-range correlations.
Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies
nucl-ex 2014-09 accept novelty 6.0 of 10

In high-multiplicity proton-lead collisions, K0S mesons show larger elliptic and triangular flow than Lambda baryons below 2 GeV, and both species fall on a common curve once divided by constituent quark number and pl...
The shape of the proton at high energies
hep-ph 2014-07 conditional novelty 6.0 of 10

Impact-parameter-dependent JIMWLK evolution of a finite proton shows that the three-valence-quark large-x shape persists in the small-x gluon distribution, with the saturation scale growing exponentially and the proto...
Eccentric protons? Sensitivity of flow to system size and shape in p+p, p+Pb and Pb+Pb collisions
nucl-th 2014-05 conditional novelty 6.0 of 10

A model that reproduces lead-lead flow data out to peripheral collisions underpredicts proton-lead flow by up to a factor of four, so either the proton's gluon shape is non-spherical or initial-state correlations domi...
Multiplicity distributions in p+p, p+A and A+A collisions from Yang-Mills dynamics
hep-ph 2013-11 conditional novelty 6.0 of 10

The IP-Glasma model, with color charge fluctuations constrained by HERA data, reproduces charged-particle multiplicity distributions across p+p, p+A and A+A collisions once an energy-dependent normalization and a tune...
Long-range angular correlations of $\rm \pi$, K and p in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV
nucl-ex 2013-07 accept novelty 6.0 of 10

In proton-lead collisions at 5.02 TeV, the second-order azimuthal coefficient v2 is smaller for protons than for pions below about 2 GeV/c and larger above it, a mass ordering that resembles heavy-ion elliptic flow.
Multiplicity and transverse-momentum dependence of two- and four-particle correlations in pPb and PbPb collisions
nucl-ex 2013-05 conditional novelty 6.0 of 10

In 5.02 TeV proton-lead collisions the third-order azimuthal harmonic v3 rises with particle multiplicity and reaches the same magnitude as in lead-lead collisions at the same multiplicity, while v2 remains roughly 30...
Measurement with the ATLAS detector of multi-particle azimuthal correlations in p+Pb collisions at sqrt(s_NN)=5.02 TeV
hep-ex 2013-03 accept novelty 6.0 of 10

Four-particle cumulants give v2 approximately 0.06 in p+Pb collisions at 5.02 TeV, roughly constant with event activity above a threshold, consistent with collective flow and with hydrodynamic predictions.
Long-range angular correlations on the near and away side in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV
nucl-ex 2012-12 accept novelty 6.0 of 10

In high-multiplicity proton-lead collisions, ALICE observes two long-range ridges, near-side and away-side, with equal yields and similar widths, the away-side ridge reported for the first time.
Hydrodynamic Collectivity in Proton--Proton Collisions at 13 TeV
nucl-th 2017-12 conditional novelty 5.0 of 10

Hydrodynamics with HIJING initial conditions describes two-particle flow in 13 TeV proton-proton collisions but yields positive c2{4}, opposite to the measured negative value, because HIJING's eccentricity fluctuation...
Parton model description of multiparticle azimuthal correlations in $pA$ collisions
hep-ph 2017-06 conditional novelty 5.0 of 10

Coherent multiple scattering of otherwise uncorrelated quarks off a nuclear target reproduces the multiparticle azimuthal cumulants previously attributed to hydrodynamic flow in proton-nucleus collisions.
Collectivity and electromagnetic radiation in small systems
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A hydrodynamics plus hadron-cascade model reproduces measured collective flow in small collision systems and predicts a factor-of-two thermal photon excess at low transverse momentum in central p+Pb and (p,d,3He)+Au c...
D-meson production in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV and in pp collisions at $\sqrt{s}=7$ TeV
nucl-ex 2016-05 accept novelty 5.0 of 10

D-meson yields per nucleon in proton-lead collisions at 5.02 TeV agree with proton-proton collisions within uncertainties from transverse momentum 0 to 24 GeV/c.
Measurements of long-range near-side angular correlations in $\sqrt{s_{\text{NN}}}=5$TeV proton-lead collisions in the forward region
nucl-ex 2015-12 accept novelty 5.0 of 10

A long-range near-side angular correlation (the ridge) is observed in proton-lead collisions at 5 TeV over 2.0 < eta < 4.9, growing with event activity and matching between beam directions at equal absolute activity.
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nucl-ex 2015-10 accept novelty 5.0 of 10

In proton-proton collisions at 13 TeV, CMS observes a long-range near-side two-particle angular correlation whose strength rises roughly linearly with charged-particle multiplicity up to N about 180, with no visible e...
Initial state geometry and the role of hydrodynamics in proton-proton, proton-nucleus and deuteron-nucleus collisions
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In small collision systems the initial geometry is strongly model dependent, yet the resulting elliptic and triangular flow differ much less, and viscous corrections stay large for roughly half the system's lifetime.
Long-Range Rapidity Correlations in Heavy-Light Ion Collisions
hep-ph 2012-12 conditional novelty 5.0 of 10

Two-gluon production in heavy-light ion collisions generates near-side and away-side long-range rapidity correlations of identical azimuthal shape, contributing only even harmonics to the di-gluon correlator.
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hep-ph 2012-11 conditional novelty 5.0 of 10

The Color Glass Condensate framework, with parameters fixed from proton-proton fits, reproduces the centrality and transverse-momentum systematics of CMS proton-lead di-hadron correlations.
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The Color Glass Condensate framework, with one normalization per collision system, reproduces the long-range di-hadron ridge in p+p and p+Pb data from CMS, ALICE and ATLAS, supporting a gluon-saturation origin.
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How the literature uses it

80 arXiv papers cite this in 137 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 89 sentences without a confident label

Contests it 1 paper

While our result is valid only for the dense-dilute scattering, we can conclude that the extrapolation suggested in [ref] does not work in the dense-dilute case, and is, therefore, unlikely to be valid in the dense-dense scattering case either.

Two-Gluon Correlations in Heavy-Light Ion Collisions: Energy and Geometry Dependence, IR Divergences, and $k_T$-Factorization · Derivation of the Factorized Forms · contest 0.87

Uses its method or tool 2 papers

The main ingredient of this computation is the so-called “dipole-dipole” correlator of light-like Wilson lines and we will compute this quantity in the following approximations: i) the Gaussian two gluon exchange (“Glasma graph”) approximation [ref] and ii) the nonlinear Gaussian approximation [ref] .

Tracing the origin of azimuthal gluon correlations in the color glass condensate · Introduction · 0.83
One way to test this within our framework is to employ the Glasma graph approximation [ref] , valid for $p_⊥> Q_s,T$.

Multiparticle collectivity from initial state correlations in high energy proton-nucleus collisions · Introduction · 0.93

Compares with it 2 papers

In this section, we show how our present calculation fundamentally differs from the so-called “Glasma graph" result [ref] .

Parton model description of multiparticle azimuthal correlations in $pA$ collisions · Appendix: Glasma graph approximation · 0.82
Unlike the Glasma graph approximation [ref] or expansions based on large-$N_c$-closed form expression [ref] , which are related to the dilute-dilute scattering regime, the Dipole Approximation provides an avenue to isolate the dominant contributions analytically when the target is dense.

First saturation correction in high energy proton-nucleus collisions: Part III. Ensemble averaging · Conclusions and Outlooks · 0.86

Cites it as support 1 paper

Indeed, there is gowing evidence that the saturation really takes place [ref] .

Numerical solution of the integral form of the resummed Balitsky-Kovchegov equation · Introduction · 0.99

Cites it as background 36 papers

This discussion will hew closely to those in Refs. [ref] with many details to be found in those papers and the papers cited therein.

Comparison of the Color Glass Condensate to di-hadron correlations in proton-proton and proton-nucleus collisions · Introduction · 0.92
The azimuthal structure of the two particle correlations results from an interplay between mini-jet (more generically di-jet) production along with glasma graph contributions at high gluon densities [ref] .

Energy dependence of the ridge in high multiplicity proton-proton collisions · Introduction · 0.93
Hydrodynamic models based on final state interactions [ref] and the Color Glass Condensate (CGC) model based on initial state correlations [ref] can both qualitatively describe the collective flow in the low transverse momentum region.

Exploring the partonic collectivity in small systems at the LHC · Introduction · 0.92

What it cites · 22 sentences without a confident label

Builds on 1 paper

We extend our previous calculation by evaluating additional diagrams that are formally subleading in $/$, as listed in appendix A of Ref. [ref] .

Long range two-particle rapidity correlations in A+A collisions from high energy QCD evolution · Introduction · 0.99

Uses the method or tool of 2 papers

The unintegrated gluon distribution (UGD) per unit transverse area $Φ$ in these expressions is a universal quantity determined by solving the Balitsky-Kovchegov (BK) equation [ref] as a function of the rapidity $y=log(x_0/x)$.

Operator expansion for high-energy scattering · Introduction · 0.85
The unintegrated gluon distribution (UGD) per unit transverse area $Φ$ in these expressions is a universal quantity determined by solving the Balitsky-Kovchegov (BK) equation [ref] as a function of the rapidity $y=log(x_0/x)$.

Small-x F_2 Structure Function of a Nucleus Including Multiple Pomeron Exchanges · Introduction · 0.85

Uses data or values from 4 papers

These spectra were measured by the CMS collaboration [ref] in events with a high charged hadron multiplicity ($N>110$) trigger in the rapidity range of $2≤|Δη| ≤4$.

Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC · Introduction · 0.99
One important source of uncertainty is due to the non-perturbative constant[$ζ$ is constrained by numerical computations [ref] and fits to the n-particle p+p multiplicity distribution [ref] to be $ζ∼1/6$.

Saturation models of HERA DIS data and inclusive hadron distributions in p+p collisions at the LHC · Introduction · 0.95
One important source of uncertainty is due to the non-perturbative constant[$ζ$ is constrained by numerical computations [ref] and fits to the n-particle p+p multiplicity distribution [ref] to be $ζ∼1/6$.

QCD saturation at the LHC: comparisons of models to p+p and A+A data and predictions for p+Pb collisions · Introduction · 0.95

Compares with 2 papers

This agreement can be contrasted with the result from the MRK expression in Eq. ([ref]), as well as the result of a computation in quasi-multi-Regge-kinematics (QMRK) that includes the $gg→gggg$ matrix element in this kinematics [ref] .

Gluon Pair Production in the Quasi-Multi-Regge Kinematics · Introduction · 0.99
This agreement can be contrasted with the result from the MRK expression in Eq. ([ref]), as well as the result of a computation in quasi-multi-Regge-kinematics (QMRK) that includes the $gg→gggg$ matrix element in this kinematics [ref] .

Angular and momentum asymmetry in particle production at high energies · Introduction · 0.99

Cites as background 9 papers

In small $x$ asymptotics, both the growth of gluon distributions via BFKL evolution and the onset and properties of the saturation regime are described by the Color Glass Condensate effective field theory (CGC-EFT) [ref] .

The Color Glass Condensate · Introduction · 0.93
The $Φ$'s in the derivation of Eq. ([ref]) are known as impact factors and, to next-to-leading-logarithmic (NLLx) accuracy in $x$, satisfy an integral equation where the kernel is the real part of the leading-logs in $x$ (LLx) BFKL kernel [ref] .

Mueller Navelet jets at LHC - complete NLL BFKL calculation · Introduction · 0.88
The $Φ$'s in the derivation of Eq. ([ref]) are known as impact factors and, to next-to-leading-logarithmic (NLLx) accuracy in $x$, satisfy an integral equation where the kernel is the real part of the leading-logs in $x$ (LLx) BFKL kernel [ref] .

The NLO Jet Vertex for Mueller-Navelet and Forward Jets: the Gluon Part · Introduction · 0.88

Discussion

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