REVIEW
Universality of the Collins-Soper-Sterman nonperturbative function in gauge boson production
High Energy Physics - Phenomenology · Submitted 23 Jun 2005 · 15 references
Pith's verdict: A real, useful revision of the b_* model — the Z-mass nonperturbative correction drops to about a third of BLNY — but the abstract's 'closely agrees' is stated at a precision the quoted errors don't support.
T0 · AI review
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Referee report
The paper
The paper claims
One nonperturbative function is enough to fit Drell-Yan and Z data
The reading
What carries the argument
The carrying device is the $b_*$ model with a raised cutoff: $b_* = b(1+b^2/b_{max}^2)^{-1/2}$, so that the leading-power form factor is the exact perturbative one, $W_{LP}(b) = W_{pert}(b_*)$, for $b$ up to roughly $b_{max}$ and only saturates beyond it. The full form factor is written $W(b) = W_{LP}(b)e^{-F_{NP}(b,Q)}$, which isolates the power-suppressed terms in the exponent while keeping the logarithmic terms in the perturbative piece. Because the choice of factorization scale $a_2 = 0.184$ GeV$^2$ is tied to $b_*$, the authors also prescribe $a_2 = C_3/b_*(b, b_0/Q_{ini})$ once $b_{max}$ exceeds $b_0/Q_{ini} = 0.86$ GeV$^{-1}$, so that the CTEQ6M densities are never evaluated below their starting scale.
Extended reading notes
Core claim
The paper's central claim is that the nonperturbative function of Collins-Soper-Sterman resummation, $F_{NP}(b,Q)$, is universal across Drell-Yan and $Z$ production and depends quasi-linearly on $a_2 = 0.184$ GeV$^2$ per unit of $a_2$.
Load-bearing premise
The functional form $F_{NP}=b^2(a_1+a_2a_2 = 0.184$ GeV$^2$.
Editorial extensions
If this is right
- The same nonperturbative function, with its fitted $a_2 = 0.184\pm0.018$ GeV$^2$, describes fixed-target Drell-Yan data near $Q\approx5$-$10$ GeV and Tevatron $Z$ data at $Q=M_Z$ without retuning.
- The nonperturbative correction at the $Z$ pole, $a(M_Z) = 0.85\pm0.10$ GeV$^2$, is about a third of the $2.7$ GeV$^2$ assumed in the earlier fit, which shrinks a leading theory uncertainty in the extraction of the $W$ mass.
- The fitted slope agrees numerically with the infrared-renormalon estimate of $0.19^{+0.12}_{-0.09}$ GeV$^2$, giving the soft-gluon interpretation of the dominant nonperturbative term direct empirical support.
- The coefficient $a_3$ that measures departure from pure $\ln Q$ dependence comes out below $0.05$ GeV$^2$, so the quasi-linear form is preferred by the data once the leading-power piece is modelled with a larger $b_{max}$.
- The quality of the fit is flat for $b_{max}$ between $1$ and $2$ GeV$^{-1}$ and degrades outside that window, which localizes where the perturbative and nonperturbative regions may be joined.
Reading between the lines
- If the slope really is the renormalon slope, then the same two-parameter description should carry over to $W$ production at the LHC without new fitting, which is a sharp test the paper does not perform here.
- The dependence on the factorization-scale parameter $C_3$ (from $0.184$ to $0.158$ GeV$^2$) is comparable to the quoted statistical error, so an extraction with higher-order coefficient functions would be the natural way to tell whether the renormalon agreement is coincidence or content.
- The paper notes that two E605 points contribute $15$-$25$ units of $\chi^2$ at any $b_{max}$ and that $\chi^2/\mathrm{d.o.f.}\approx1$ follows if they are dropped; a reader should treat the absolute fit quality as partly hostage to those two points rather than to the model.
- Because the linear $\ln Q$ form is imposed by renormalization-group invariance rather than discovered, the genuinely empirical statements are the magnitude of $a_2$ and the smallness of $a_3$; a future fit that leaves the $Q$ dependence free would be the cleanest confirmation of universality.
Original abstract
We revise the $b_*$ model for the Collins-Soper-Sterman resummed form factor to improve description of the leading-power contribution at nearly nonperturbative impact parameters. This revision leads to excellent agreement of the transverse momentum resummation with the data in a global analysis of Drell-Yan lepton pair and Z boson production. The nonperturbative contributions are found to follow universal quasi-linear dependence on the logarithm of the heavy boson invariant mass, which closely agrees with an estimate from the infrared renormalon analysis.
The compiled record
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.
The abstract, sentence by sentence
We revise the $b_*$ model for the Collins-Soper-Sterman resummed form factor to improve description of the leading-power contribution at nearly nonperturbative impact parameters. This revision leads to excellent agreement of the transverse momentum resummation with the data in a global analysis of Drell-Yan lepton pair and Z boson production. The nonperturbative contributions are found to follow universal quasi-linear dependence on the logarithm of the heavy boson invariant mass, which closely agrees with an estimate from the infrared renormalon analysis.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We revise the $b_*$ model for the Collins-Soper-Sterman resummed form factor to improve description of the leading-power contribution at nearly nonperturbative impact parameters. | contribution 0.74 | 0.93 | 0.09 | asserted 0.96 |
| s1 | This revision leads to excellent agreement of the transverse momentum resummation with the data in a global analysis of Drell-Yan lepton pair and Z boson production. | result 0.99 | 0.87 | 0.28 | asserted 1.00 |
| s2 | The nonperturbative contributions are found to follow universal quasi-linear dependence on the logarithm of the heavy boson invariant mass, which closely agrees with an estimate from the infrared renormalon analysis. | result 0.97 | 0.93 | 0.64 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v3
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
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- R cross-paper relations
Figures
Figures reproduced from arXiv:hep-ph/0506225 by the authors.
References
How the literature uses it
44 arXiv papers cite this in 72 sentences
Papers citing it · 42 sentences without a confident label
Contests it 1 paper
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This suggests the following hypothesis: The fits in Refs. [ref] determine $g_K$ and $g_j/H$ in a range of relatively low $b$, say between about 0.5 and $[2]GeV^-1$, but their extrapolation to larger $b$ is wrong.
Understanding the large-distance behavior of transverse-momentum-dependent parton densities and the Collins-Soper evolution kernel · Fits to Drell-Yan data with CSS formalism · contest 0.75
Uses its method or tool 3 papers
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To account for non-perturbative effects that dominate at large impact parameters $b$, we introduce a non-perturbative Sudakov form factor, $S_NP$ [ref] .
Resummed azimuthal decorrelation and transverse momentum imbalance of dijets at the LHC · Azimuthal decorrelation · 0.94
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At leading order of $C_a/i$, the evolved TMD reduces to [equation] where the Sudakov factor is [ref] [equation] The functions $A$ and $B$ have a perturbative expansions of the form [equation] To NLL accuracy, one has [ref] [equation] Following Refs. [ref] , the non-perturbative Sudakov factor in Eq. ([ref]) is modeled as [equation] with $g_2$ a free parameter.
Transvese momentum dependent parton distributions of pion at leading twist · The generalized Boer-Mulders shift · 0.87
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However, in the integration, we encounter an issues in the region where $μ_b ∼Λ_QCD$, which is avoided using the $b_*$-prescription [ref] .
Precision three-dimensional imaging of nuclei using recoil-free jets · Parameterization · 0.90
Uses its data or values 5 papers
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[equation] In this work, the universality of the CSS kernel is tested by verifying that the observables are well described across several resolution parameters $R$, grooming settings, and intervals with the same parameters in $g_K(b_⊥;b_⊥^max)$ corresponding to $b_⊥^max = 1.5 (GeV/c)^-1$ and $g_2(b_⊥^max) = 0.18$ from a global data analysis to Drell–Yan lepton pair and Z$^0$-boson production [ref] .
Measurement of the angle between jet axes in pp collisions at $\sqrt{s} = 5.02$ TeV · Comparison to analytical calculations · 0.92
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The analysis in Ref. [ref] has found that $b_max = 1.5$ GeV$^-1$ is preferred, and the parameters for the BLNY fit in Eq. ([ref]) become $g_1 = 0.201$ GeV$^2$, $g_2 = 0.184$ GeV$^2$ and $g_3 = -0.129$.
TMD Parton Distribution and Fragmentation Functions with QCD Evolution · TMD PDFs · 0.89
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This justifies the use of the following expression: [equation] employed and fitted to data in Ref. [ref] (BLNY in the following) and in Ref. [ref] (KN) where they found, respectively, a value of $g_2 = 0.68 GeV^2$, with $b_max = 0.5 GeV^-1$, and a value of $g_2 = 0.18 GeV^2$, with $b_max = 1.5 GeV^-1$.
Transverse $\Lambda$ polarization in $e^+e^-$ processes within a TMD factorization approach and the polarizing fragmentation function · $g_K(b_T;b_max)$ · 0.88
Compares with it 1 paper
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By contrast, the Drell-Yan fits in Refs. [ref] give results in terms of the TMD factorization formula in the particular CSS1 form given in Eq. ([ref]).
Connecting Different TMD Factorization Formalisms in QCD · TMD functions from fits with CSS1 · 0.88
Cites it as support 1 paper
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Confirmations are given both at perturbative level (the coefficients of perturbative expansion are known up to four loops [ref] , and also in the non-perturbative regime, where both phenomenological extractions [ref] and lattice computations [ref] agree on considering $g_K$ as a positive-definite monotonically increasing function of $b_T$.
Full treatment of the thrust distribution in single inclusive $e^+ e^- \to h \, X$ processes · Rapidity regulator as a function of thrust · 0.96
Cites it as background 15 papers
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The original CSS formula [ref] , as used in the fits in [ref] , was obtained starting from a TMD factorization formula, using the specific definitions of TMD parton densities that had been given by Collins and Soper (CS) [ref] .
Connecting Different TMD Factorization Formalisms in QCD · Original CSS formalism · 0.83
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In previous work on CSS resummation, the $b_*$-prescription was introduced along with non-perturbative Sudakov factors, which were modeled through various functional forms and obtained by fitting to experimental data [ref] .
QCD resummation of dijet azimuthal decorrelations in pp and pA collisions · Parameterization · 0.99
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The presence, at low lepton-pair transverse momenta, of large logarithmically enhanced QCD corrections and the role, in the same kinematic region, of non-perturbative effects have been discussed in Refs. [ref] , but the dependence of the resulting model on the acceptance cuts has never been investigated in detail and will deserve a dedicated study.
Prospects for improving the LHC W boson mass measurement with forward muons · Uncertainties stemming from the modelling · 0.94
Discussion
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