REVIEW
Fragmentation Functions for Pions, Kaons, and Protons at Next-to-Leading Order
High Energy Physics - Phenomenology · Submitted 25 Oct 2000 · 40 references
Pith's verdict: The KKP fragmentation functions: a solid, unusually honest global fit that became a standard reference, with one real soft spot in how flavour-tagged charged-hadron data are kept or dropped.
T0 · AI review
Why Pith says this
Highlight any text to comment on it.
Referee report
The paper
The paper claims
A single set of fragmentation functions, fitted at the Z peak, also reproduces hadron production at five lower energies and pins down the strong coupling.
The reading
What carries the argument
The machinery is a global fit in which the $x$ dependence of each fragmentation function is fixed by a three-parameter form $N x^alpha (1-x)^beta$ at a flavour-dependent starting scale ($sqrt{2}$ GeV for light quarks and the gluon, the $eta_c$ mass for charm, the $Upsilon$ mass for bottom), and the scale dependence is generated by the timelike Altarelli-Parisi evolution equations solved in Mellin space. What carries the argument is the flavour separation: light-, charm-, and bottom-enriched samples plus gluon-tagged three-jet events let the fit treat each parton independently, subject only to the symmetry relations $D_u^{pi^pm} = D_d^{pi^pm}$, $D_u^{K^pm} = D_s^{K^pm}$, and $D_u^{p/bar p} = 2 D_d^{p/bar p}$ suggested by valence content. The two-energy fit, with $29$ GeV data included alongside the Z peak, is what converts the fit from a description of one energy into a measurement of scaling violation and hence of $alpha_s$.
Extended reading notes
Core claim
The paper reports new leading-order and next-to-leading-order sets of fragmentation functions for $h = $ sum over $h$ of $D_a^h(x,Q^2)$, with $h$ standing for the charge-summed $h$, $K^pm$, and $p/bar p$, parameterized at three starting scales as $D_a^h(x,Q_0^2) = N x^alpha (1-x)^beta$. With 46 free parameters, including the QCD scale parameter, the fit achieves an overall $chi^2$ per degree of freedom of $0.98$ at NLO and $0.97$ at LO across the ALEPH, DELPHI, OPAL, SLD, and TPC samples used as input. Because data at $29$ GeV and $91.2$ GeV enter together, the fit is sensitive to the running of the coupling and returns $Lambda_{overline{MS}}^{(5)} = 213^{+75}_{-73}$ MeV and $alpha_s(M_Z) = 0.1170^{+0.005}_{-0.007}$ at NLO, values the authors note agree with the then-current world average. The authors treat the agreement with the longitudinal cross section, where the gluon function already enters at leading order, as an independent confirmation of the gluon fragmentation function, and they check that the momentum sum rule, which they did not impose, comes out reasonably close to unity over the range $0.05 le x le 1$.
Load-bearing premise
The fit's light-quark and bottom-quark fragmentation functions are fixed by keeping the DELPHI and SLD flavour-tagged samples and discarding the ALEPH and OPAL ones, on the belief that an unmeasured population of charged hadrons other than pions, kaons, and protons explains why those discarded samples sit far above the predictions.
Editorial extensions
If this is right
- The extracted functions can be inserted into predictions for single-hadron production in $p bar p$, $e p$, $gamma p$, and $gamma gamma$ scattering, since the factorization theorem makes them process-independent.
- The NLO value $alpha_s(M_Z) = 0.1170^{+0.005}_{-0.007}$ from a single class of observables provides an independent cross-check on averages built from many different measurements.
- The agreement with DORIS and PETRA data at $5.4$ to $34$ GeV supports the assumption that power corrections suppressed by $1/Q$ are negligible over the energy range of the fit.
- The gluon fragmentation function, constrained by gluon-tagged three-jet events and tested by the longitudinal cross section, is made available for use in other processes where gluon fragmentation dominates.
- The public FORTRAN routine released with the paper lets other analyses evaluate $D_a^h(x,Q^2)$ directly, which is what makes the set usable outside this paper.
Reading between the lines
- The decision to exclude the ALEPH and OPAL flavour-tagged charged-hadron samples, which give chi-squared per degree of freedom of order $100$ against these predictions, is the hinge on which the light- and bottom-quark functions turn; a future measurement of the yield of charged hadrons beyond $pi^pm$, $K^pm$, and $p/bar p$ in tagged Z decays would either vindicate or overturn it.
- Because the fit does not impose the momentum sum rule, the shortfall in Table 4 (the $s$-quark entry sits near $0.6$ and the gluon above unity at low scales) is a diagnostic of how weakly the individual light-quark flavours are constrained rather than a refutation; the imbalance is traced to the $d$-quark component of the kaon behaving unlike a sea quark.
- The parameterization $N x^alpha (1-x)^beta$ is bound to fail at very small $x$, where the authors themselves point to modified leading-logarithmic resummation; a natural extension is to refit with an MLLA-motivated form and see whether the gluon function and the extracted $alpha_s$ shift.
- Since the same functions should describe fragmentation in hadron-hadron and lepton-hadron collisions, the sharpest external test is a prediction for inclusive identified-hadron cross sections at a scale far from the Z peak, where the evolution rather than the fit dominates.
Original abstract
We present new sets of fragmentation functions for charged pions, charged kaons, and protons, both at the leading and next-to-leading orders. They are fitted to the scaled-momentum distributions of these hadrons measured in e+e- annihilation on the Z-boson resonance at CERN LEP1 and SLAC SLC. These data partly come as light-, charm-, bottom-quark-enriched and gluon-jet samples, which allows us to treat all partons independently, after imposing the SU(2) flavour symmetry relations. In order to gain sensitivity to the scaling violation in fragmentation, we also include data from SLAC PEP, with center-of-mass energy root(s)=29 GeV, in our fits. This allows us to also determine the strong-coupling constant, with a competitive error. LEP1 data on the longitudinal cross section as well as DESY DORIS and PETRA data at lower energies nicely agree with theoretical predictions based on our fragmentation functions.
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 present new sets of fragmentation functions for charged pions, charged kaons, and protons, both at the leading and next-to-leading orders. They are fitted to the scaled-momentum distributions of these hadrons measured in e+e- annihilation on the Z-boson resonance at CERN LEP1 and SLAC SLC. These data partly come as light-, charm-, bottom-quark-enriched and gluon-jet samples, which allows us to treat all partons independently, after imposing the SU(2) flavour symmetry relations. In order to gain sensitivity to the scaling violation in fragmentation, we also include data from SLAC PEP, with center-of-mass energy root(s)=29 GeV, in our fits. This allows us to also determine the strong-coupling constant, with a competitive error. LEP1 data on the longitudinal cross section as well as DESY DORIS and PETRA data at lower energies nicely agree with theoretical predictions based on our fragmentation functions.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present new sets of fragmentation functions for charged pions, charged kaons, and protons, both at the leading and next-to-leading orders. | contribution 1.00 | 0.95 | 0.60 | asserted 1.00 |
| s1 | They are fitted to the scaled-momentum distributions of these hadrons measured in e+e- annihilation on the Z-boson resonance at CERN LEP1 and SLAC SLC. | method 0.96 | 0.80 | 0.07 | asserted 1.00 |
| s2 | These data partly come as light-, charm-, bottom-quark-enriched and gluon-jet samples, which allows us to treat all partons independently, after imposing the SU(2) flavour symmetry relations. | method 0.99 | 0.40 | 0.05 | asserted 0.99 |
| s3 | In order to gain sensitivity to the scaling violation in fragmentation, we also include data from SLAC PEP, with center-of-mass energy root(s)=29 GeV, in our fits. | method 0.96 | 0.78 | 0.03 | asserted 0.96 |
| s4 | This allows us to also determine the strong-coupling constant, with a competitive error. | result 0.97 | 0.92 | 0.12 | asserted 0.99 |
| s5 | LEP1 data on the longitudinal cross section as well as DESY DORIS and PETRA data at lower energies nicely agree with theoretical predictions based on our fragmentation functions. | result 0.91 | 0.55 | 0.19 | asserted 0.95 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
Figures
Figures reproduced from arXiv:hep-ph/0010289 by the authors.
References
How later papers used it
80 later papers cite it
10 later papers by other authors are listed below: 8 used its method or tool, 1 used its data or values and 1 compared its own results with it.
Uses its method or tool 8 of 14 papers with this label
-
Employed the next-to-leading order KKP fragmentation functions from this paper to obtain the charged hadron pseudo-rapidity density from the gluon spectrum.
Accessing subnuclear fluctuations and saturation with multiplicity dependent $J/\psi$ production in p+p and p+Pb collisions (2021) · 0.94 · paraphrased: the licence does not allow quoting
-
Used the fragmentation functions from this paper to obtain the pionic R_AA from the partonic one, neglecting the gluon contribution.
Holographic light quark jet quenching at RHIC and LHC via the shooting strings (2014) · 0.95 · paraphrased: the licence does not allow quoting
-
Computed charged hadron production in p+p(A) collisions by convoluting the inclusive gluon production cross-section with the KKP fragmentation function from this paper.
Unified framework for heavy flavor and quarkonium production in high multiplicity p+p and p+A collisions at RHIC and LHC (2018) · 1.00 · paraphrased: the licence does not allow quoting
-
We convoluted the parton spectra with Binnewies-Kniehl-Kramer (BKK) [ref] and Kniehl-Kramer-Potter (KKP) [ref] fragmentation functions (FFs) using the program [ref] [<http://lapth.cnrs.fr/PHOX_FAMILY/readme_inc.html>] modified to use LHAPDF grids [ref] .
Discovering partonic rescattering in light nucleus collisions (2020) · Introduction · 0.97
-
Computed the charged hadron distribution from the gluon distribution using the next-to-leading order KKP fragmentation functions from this paper.
Multiplicity distributions in p+p, p+A and A+A collisions from Yang-Mills dynamics (2013) · 0.98 · paraphrased: the licence does not allow quoting
-
Generated partonic spectra and used the KKP fragmentation function from this paper to generate leading hadron spectra.
Event-by-Event Simulations of Jet Modification Using the MATTER Event Generator (2017) · 0.94 · paraphrased: the licence does not allow quoting
-
Showed results using the NLO KKP parameterization from this paper of fragmentation functions for gluon to charged hadrons.
Novel Collective Phenomena in High-Energy Proton-Proton and Proton-Nucleus Collisions (2015) · 0.89 · paraphrased: the licence does not allow quoting
-
Set up grids for inclusive pion production in DAu collisions at RHIC using the INCNLO code with the KKP fragmentation functions from this paper.
EPPS16: Nuclear parton distributions with LHC data (2016) · 0.97 · paraphrased: the licence does not allow quoting
Uses its data or values 1 of 6 papers with this label
-
Employed the NLO parametrization of the KKP fragmentation function from this paper for charged hadron production at mu=2 GeV.
Event engineering studies for heavy flavor production and hadronization in high multiplicity hadron-hadron and hadron-nucleus collisions (2018) · 0.95 · paraphrased: the licence does not allow quoting
Compares with it 1 of 2 papers with this label
-
Found that its own microcanonical Tsallis fragmentation function differs from the HKNS and KKP fragmentation functions from this paper at lower energy scales and momenta.
Non-extensive Motivated Parton Fragmentation Functions (2018) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
75 arXiv papers cite this in 92 sentences
Papers citing it · 59 sentences without a confident label
Uses its method or tool 13 papers
-
KRE [ref] , KKP [ref] , HKNS [ref] , AKK08 [ref] , and DSS [ref] FFs are used with the same scale $μ= 1.2 p_T$ for single hadrons and $μ= 1.2 M$ for dihadrons, respectively.
Extracting the jet transport coefficient from hadron suppressions by confronting current NLO parton fragmentation functions · Extracting $q̂_0$ in central $Au+Au$ collisions at $√(s_NN)=200$ GeV · 0.86
-
We compute gluon production using $k_T$-factorized cross sections [ref] and hadronize using KKP fragmentation functions [ref] .
Accessing subnuclear fluctuations and saturation with multiplicity dependent $J/\psi$ production in p+p and p+Pb collisions · Introduction · 0.98
-
Finally, we use the fragmentation functions [ref] to obtain the pionic $R_AA$ from the partonic one (neglecting the gluon contribution).
Holographic light quark jet quenching at RHIC and LHC via the shooting strings · Calculation of $R_AA$ · 0.95
Uses its data or values 5 papers
-
The parton distribution functions are denoted by $f_i/p (x_1, μ^2 )$ and are given by the CTEQ6 parameterization [ref] . $D^0_h/i(z_i,μ^2)$ are the unmodified fragmentation functions given by the KKP parameterization [ref] .
Three and two-hadron correlations in \sqrt{s_{NN}}=200 GeV proton-proton and nucleus-nucleus collisions · Introduction · 0.81
-
For the vacuum FFs $D_h/j(z,Q_0)$ we use the KKP [ref] parametrization with $Q_0=2$ GeV.
Updated analysis of jet quenching at RHIC and LHC within the light cone path integral approach · Nuclear modification factor · 0.83
-
Using Refs. [ref] for the integrated FFs, we can then calculate the TMD FF using Eq. [ref].
TMD Parton Distribution and Fragmentation Functions with QCD Evolution · TMD FFs · 0.96
Compares with it 2 papers
-
We obtained that our microcanonical Tsallis FF differs from the HKNS [ref] and KKP [ref] FFs at lower energy scales and momenta, which could affect the low momentum calculations of proton-proton collisions.
Non-extensive Motivated Parton Fragmentation Functions · Conclusion · 1.00
-
This may explain why, despite the very different theoretical constraints on the KKP [ref] and Kretzer [ref] sets, the values for this FF from these sets are very similar in the fit range of $x$, except at large $z$ because the data at large $x$ are scarce (see Fig. [ref]).
The hadronization of partons · Global fitting of fragmentation functions from $e^+ e^-$ reaction data · 0.96
Cites it as background 10 papers
-
Recent determinations of the pion FFs include results by several groups such as HKNS [ref] , NNFF [ref] , JAM [ref] , SGKS [ref] , SGK [ref] , and other studies available in the literature including KKP [ref] , BKK [ref] , and KLC [ref]
QCD analysis of pion fragmentation functions in the xFitter framework · Introduction · 0.96
-
Gluon fragmentation functions from different authors are available for the use in perturbative QCD calculations, e.g., KRE [ref] , BKK [ref] , KKP [ref] , AKK [ref] , DSS [ref] .
Production of Neutral Pions and Eta-mesons in pp Collisions Measured with ALICE · Introduction · 0.85
-
Fragmentation functions have first been determined from global fits of data (e.g. BFGW [ref] , KKP [ref] , Kretzer [ref] ), at LEP and other facilities at lower energies.
Probing fragmentation functions from same-side hadron-jet momentum correlations in p-p collisions · Introduction · 1.00
Discussion
Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.