Next-to-leading order fragmentation functions for pions and kaons

Binnewies, J.; Knieh, B. A.; Krämer, G.

doi:10.1007/bf01556135

Cited by 160 publications

(181 citation statements)

References 37 publications

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“…This comparison is shown in figure 4. The NLO calculation combines a full next-to-leading order matrix element with the MRSA ′ parton densities (with Λ QCD = 230 MeV) and NLO fragmentation functions derived by Binnewies et al from fits to e + e − data [41]. The data and the NLO calculations are in good agreement, supporting the idea of universality of quark fragmentation.…”

Section: Discussionmentioning

confidence: 53%

Observation of scaling violations in scaled momentum distributions at HERA

Breitweg¹,

Derrick²,

Krakauer³

et al. 1997

Physics Letters B

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Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of x and Q 2 using the ZEUS detector. The evolution of the scaled momentum, x p , with Q 2 , in the range 10 to 1280 GeV 2 , has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of Q 2 .

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Section: Discussionmentioning

confidence: 53%

Observation of scaling violations in scaled momentum distributions at HERA

Breitweg¹,

Derrick²,

Krakauer³

et al. 1997

Physics Letters B

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“…Using the fragmentation functions of Ref. [28] for pions that are determined from e + e − , ep, and pp collisions, we find that the measured pion spectrum in pp collisions at √ s NN = 62 GeV [29] can be reproduced with a p T -dependent K NLO in Eq.(5). Similar p T dependence of the K NLO factor for pion and direct photon production in pp collisions has been previously found in Ref.…”

mentioning

confidence: 98%

“…Besides their contribution to pions using the fragmentation functions of Ref. [28] that are determined from e + e − , ep, and pp collisions, we evaluate that to baryons such as p andp based on a string-inspired parametrization of their fragmentation functions (see Refs. [35,36]).…”

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confidence: 99%

Hadron production from quark coalescence and jet fragmentation

Greco

Vitev

2005

Phys. Rev. C

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Transverse momentum spectra of pions, protons, and antiprotons in Au + Au collisions at intermediate RHIC energy √ s NN = 62 GeV are studied in a model that includes both quark coalescence from the dense partonic matter and fragmentation of the quenched perturbative minijet partons. The resulting baryon to meson ratio at intermediate transverse momenta is predicted to be larger than that seen in experiments at higher center of mass energies. Recently, there has been renewed interest in using the quark coalescence or recombination model to study hadron production in ultrarelativistic heavy ion reactions [1][2][3][4][5][6][7][8][9]. These studies were largely triggered by two surprising observations in measured hadron spectra from Au + Au collision at √ s NN = 200 GeV at the BNL Relativistic Heavy Ion Collider (RHIC) [1,[10][11][12]. The first was the nearly similar yield of protons and pions at intermediate transverse momentum (2 GeV < p T < 5 GeV), which is at variance with the expectation from the fragmentation of minijets produced from initial hard processes. The second was the so-called "quark number scaling" of hadron elliptic flow v 2h (p T ), i.e., the transverse momentum dependence becomes universal if both v 2h and transverse momentum p T are divided by the number of constituent quarks in the hadron. Both phenomena have a simple explanation if hadronization of the thermally equilibrated and collectively flowing partonic matter formed in these collisions proceeds through the coalescence of quarks of constituent masses [3][4][5][6].The description of hadronization of the quark-gluon plasma formed in heavy ion collision at relativistic energies by quark coalescence was first introduced in models such as ALCOR [13] and MICOR [14]. Emphases of these earlier studies were on particle yields and their ratios. Recent studies have been more concerned with observables that are related to collective dynamics and production of hadrons with relatively large transverse momenta. Furthermore, effects of minijet partons from initial hard processes have also been included through their independent fragmentation as well as coalescence with soft partons in the quark-gluon plasma [3,4]. The latter provides a new mechanism for the hadronization of minijet partons produced in relativistic heavy ion collisions. The interplay between quark coalescence and minijet fragmentation has been found to be essential for understanding measured inclusive hadron spectra at moderate and high transverse momenta. In particular, the observed jetlike features of these hadrons [15] seem to also support the scenario that they are produced from the coalescence of minijets with the thermal partons in the produced quark-gluon plasma. If confirmed by more exclusive data from experiments and by further theoretical studies, hadronization via quark coalescence then represents a new probe of the quark-gluon plasma formed in relativistic heavy ion collisions, and its hadronization mechanism, as well as that of the minijet partons produced in these collision...

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“…In e + e − collisions, the hadron production cross section (differential in incoming momentum fraction x) is given by [8] …”

mentioning

confidence: 99%

“…Through next-to-leading order (NLO), in the M S scheme, the partonic sub-process cross section for quark flavor i can be written as [8] …”

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confidence: 99%

Decisive Role of Fragmentation Functions in Hard Hadron Production

2002

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It is demonstrated that the fragmentation functions at large momentum fraction play a key role in hard hadron production from relativistic proton-proton collisions. We find that this region of the fragmentation functions is not strongly constrained by the electron-positron data. This freedom can be used (together with the transverse momentum distribution of partons) to reproduce hard pion-to-proton ratio data in relativistic proton-proton collisions.PACS 13.87.Fh Hadron spectra at large transverse momentum (p T ), where perturbative Quantum Chromodynamics (pQCD) has good predictive power, are very important for our understanding of the physics at the Relativistic Heavy Ion Collider (RHIC) and at the planned Large Hadron Collider (LHC). Various experiments at these colliders focus on hard (high p T ) hadron spectra. Jet "tomography" (the study of the strongly-interacting medium via energy loss of hard partons) has been proposed to detect the quark-gluon plasma (QGP), using high-p T hadron production [1,2].Suppression of total charged hadron production in Au + Au collisions relative to a nucleon-nucleon reference is reported at RHIC [3,4]. However, for the proton-to-pion (p/π) ratio the PHENIX experiment reports an anomalous enhancement in Au+Au collisions at √ s = 130 GeV [5]. An explanation for the p/π enhancement was proposed recently, combining pQCD with soft physics and jet quenching [6]. It should be kept in mind in this context that, while pQCD is quite successful for total charged hadron (h + + h − ) and pion production at large p T in pp collisions, proton production in pp is not well understood using the language of pQCD. In fact, pQCD underestimates the p/π + ratio by a factor of 3-10 in pp collisions (see Fig. 3(a) of this work for √ s = 27.4 GeV, and e.g. Ref.[6] for Tevatron energy).In this Letter we look into how pQCD is used to calculate p T spectra in pp collisions. We focus on the role of a non-perturbative ingredient, the fragmentation function (obtained by fitting data) in the production of hadronic final states. Most of the information included in the fits comes from h + + h − data. The fragmentation function (FF) of pions is studied in some detail. Less direct information is available on kaons, and the FF of protons is even less well-known. In the following, we concentrate on the proton FF as an example of the role of the FF in the hadroproduction of hard particles. We find (for all types of hadrons) that the value of the FF in a region of phase space where it is least constrained plays a decisive role for hadron production at RHIC and LHC.To predict the p T spectra of final state hadrons in the framework of pQCD, perturbative partonic cross sections need to be convoluted with parton distribution functions (PDF-s) and fragmentation functions (FF-s) according to the factorization theorem [7]. Perturbative QCD has nothing to say about the details of FF-s, apart from describing their scale evolution. The FF-s are assumed to be universal, meaning that once extracted from a limited set of data...

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Next-to-leading order fragmentation functions for pions and kaons

Cited by 160 publications

References 37 publications

Observation of scaling violations in scaled momentum distributions at HERA

Observation of scaling violations in scaled momentum distributions at HERA

Hadron production from quark coalescence and jet fragmentation

Decisive Role of Fragmentation Functions in Hard Hadron Production

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