Fragmentation functions from semi-inclusive DIS pion production and implications for the polarized parton densities

Christova, Ekaterina; Kretzer, S.; Leader, Elliot

doi:10.1007/s100520100815

Cited by 77 publications

(74 citation statements)

References 14 publications

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“…2 that taking β = 0.8β KKP does not change the quality of the fit to the e + e − data at this energy. It is also clear from the above discussion, how different parameterizations of FF-s [8][9][10][11] can be rather different in the large z region even for h + + h − fragmentation (the FF-s studied in most detail).…”

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confidence: 94%

“…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 via a fitting procedure, they can then be used with predictive power in other reactions [8][9][10][11]. The situation is conceptually identical to that of the PDF-s. We will work with this formalism in the present paper.…”

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confidence: 99%

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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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confidence: 94%

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confidence: 99%

Decisive Role of Fragmentation Functions in Hard Hadron Production

2002

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“…However, the situation has now been changed because the HERMES collaboration has published results of charge separated data for π ± production on the proton target [2]. By combining the HER-MES data on semi-inclusive DIS (SIDIS) π ± -production with the singlet fragmentation function D π + Σ , which is well determined from e + e − data, Kretzer, Leader, and Christova [3] …”

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confidence: 99%

Fragmentation functions of mesons in the Field-Feynman model

Hua

2003

Eur. Phys. J. C

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“…We are aware of only one set of proton FF-s from global fitting to date [18]. Compared to proton FF-s, FF-s for charged hadron and pion production are better studied, supported by more experimental information [19,20]. At the same time, the RHIC data for the p/π ratio are only available for p T ≤ 5 GeV, while h ± /π ratios are available for p T to about 10 GeV.…”

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confidence: 99%

“…In this paper, we use CTEQ5L [24] PDF-s and a set of FF-s [19] which were determined relying also on semi-inclusive data. the calculated charged hadron and pion spectra to RHIC data [2,25] for p T ≥ 2 GeV, where the pQCD calculation can be used.…”

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The charged-hadron/pion ratio at the Relativistic Heavy Ion Collider

Zhang¹,

Fái

2004

J. Phys. G: Nucl. Part. Phys.

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The hadron/pion ratio is calculated in 200 GeV AuAu collisions at midrapidity, applying pQCD and non-universal transverse-momentum broadening. Arguments are presented for such non-universality, and the idea is implemented in a model, which reproduces the main features of the centrality dependence of the hadron/pion ratio in AuAu collisions. The model also reasonably describes the qualitative difference between the recently-measured dAu nuclear enhancement factors for pions and charged hadrons.

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Fragmentation functions from semi-inclusive DIS pion production and implications for the polarized parton densities

Cited by 77 publications

References 14 publications

Decisive Role of Fragmentation Functions in Hard Hadron Production

Decisive Role of Fragmentation Functions in Hard Hadron Production

Fragmentation functions of mesons in the Field-Feynman model

The charged-hadron/pion ratio at the Relativistic Heavy Ion Collider

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