Charm and bottom production: theoretical results versus experimental data

Frixione, Stefano; Mangano, M.; Nason, Paolo; Ridolfi, Giovanni

doi:10.1016/0550-3213(94)90213-5

Cited by 128 publications

(166 citation statements)

References 70 publications

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“…Neither leading-order nor next-to-leading-order perturbative QCD calculations of charm quark production can account for the observed asymmetries [10,11]. The phenomenon is due either to unexpected contributions to charm quark production or to features of the hadronization process.…”

Section: Introductionmentioning

confidence: 95%

Asymmetries between the production of D− and D+ mesons from 500 GeV/c π− nucleon interaction as functions of x and p2

et al. 1997

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We present measurements of the production of D s − mesons relative to D s + mesons as functions of x F and of p t 2 for a sample of 2445 D s decays to φπ. The D s mesons were produced in Fermilab experiment E791 with 500 GeV/c π − mesons incident on one platinum and four carbon foil targets. The acceptance-corrected integrated asymmetry in the x F range −0.1 to 0.5 for D s ∓ mesons is 0.032 ± 0.022 ± 0.022, consistent with no net asymmetry. We compare the results as functions of x F and p t 2 to predictions and to the large production asymmetry observed for D ± mesons in the same experiment. These comparisons support the hypothesis that production asymmetries come from the fragmentation process and not from the charm quark production itself.2 Previous studies of charm particle production in hadron beams [1][2][3][4][5][6][7][8][9] have shown large enhancements in the forward production of charm particles that contain a quark or di-quark in common with the beam (leading particles) relative to those that do not (non-leading particles). Neither leading-order nor next-to-leading-order perturbative QCD calculations of charm quark production can account for the observed asymmetries [10,11]. The phenomenon is due either to unexpected contributions to charm quark production or to features of the hadronization process.Three classes of models have been proposed to account for hadronization in the beam fragmentation region: coalescence of produced charm quarks with valence quarks or diquarks from the beam [12][13][14], coalescence of charm and valence quarks when both originate in the beam particle [15][16][17], and string fragmentation as implemented in the Lund Model of the PYTHIA Monte Carlo program [18] and by Piskounova [19]. All these models involve a mechanism of attachment between the produced charm quarks and the valence quarks in the beam, and include a varying amount of actual coalescence. This coalescence is the dominant mechanism for the leading particle effect in the first two classes of models. They include no mechanism which will lead to a significant production asymmetry between particles except when one of them has a quark in common with the beam and the other does not. Since the probability of coalescence between two quarks is larger when they have similiar velocities, the production asymmetry between leading and nonleading charm mesons is expected to grow larger with increasing x F and smaller with increasing p t 2 . While D ± data from Fermilab experiment E791 do show the expected increase in asymmetry with increasing x F , they do not support the prediction of decreasing asymmetry withIn string fragmentation models, specifically the PYTHIA/LUND implementation, a produced charm quark is always initially connected via color strings to valence quarks or diquarks in the beam and the target. A leading particle can be produced by a meson beam in cases where the string attaches a charm quark to a beam antiquark and/or an anticharm quark to a beam quark. Some fraction of the time, the 3 string invaria...

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Section: Introductionmentioning

confidence: 95%

Asymmetries between the production of D− and D+ mesons from 500 GeV/c π− nucleon interaction as functions of x and p2

et al. 1997

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“…The total cross section is strongly dependent on QCD parameters such as the heavyquark mass, parton distributions, and factorization and renormalization scales. It is not our aim here to present theoretical limits and errors -this has been done elsewhere [13]. However, Fig.…”

Section: Properties Of the Perturbative Productionmentioning

confidence: 99%

“…Depending on the choice of cut-off parameters, the latter may give negative differential cross sections in some regions of phase space. The divergences disappear in sufficiently inclusive distributions, so much phenomenological insight can be gained [13]. However, with our currently available set of calculational tools, the NLO approach is not so well suited for the exclusive Monte Carlo studies we have in mind here, where hadronization is to be added on to the partonic picture.…”

Section: Perturbative Aspects 211 Production Mechanismsmentioning

confidence: 99%

Production and hadronization of heavy quarks

2000

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Heavy long-lived quarks, i.e. charm and bottom, are frequently studied both as tests of QCD and as probes for other physics aspects within and beyond the standard model. The long life-time implies that charm and bottom hadrons are formed and observed. This hadronization process cannot be studied in isolation, but depends on the production environment. Within the framework of the string model, a major effect is the drag from the other end of the string that the c/b quark belongs to. In extreme cases, a small-mass string can collapse to a single hadron, thereby giving a nonuniversal flavour composition to the produced hadrons. We here develop and present a detailed model for the charm/bottom hadronization process, involving the various aspects of string fragmentation and collapse, and put it in the context of several heavy-flavour production sources. Applications are presented from fixed-target to LHC energies.

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“…Other data also suggest k T values larger than those expected from NLO PQCD calculations. Recent comparisons of p T spectra from charm-particle hadroproduction to NLO PQCD results provide evidence that supplemental k T may be required to properly describe the data [6]. Likewise, it has been suggested that the observed pattern of discrepancies between data from various direct-photon experiments and results from NLO PQCD calculations could be related to k T effects [7].…”

mentioning

confidence: 99%

Evidence for PartonkTEffects in High-pTParticle Production

Apanasevich¹,

Bacigalupi²,

Baker³

et al. 1998

Phys. Rev. Lett.

116

139

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Inclusive π 0 and direct-photon cross sections in the kinematic range 3.5< p T <12 GeV/c with central rapidities (y cm ) are presented for 530 and 800 GeV/c proton beams and a 515 GeV/c π − beam incident on Be targets. Current Next-to-Leading-Order perturbative QCD calculations fail to adequately describe the data for conventional choices of scales. Kinematic distributions from these hard scattering events provide evidence that the interacting partons carry significant initial-state parton transverse momentum (k T ). Incorporating these k T effects phenomenologically greatly improves the agreement between calculations and the measured cross sections.

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Charm and bottom production: theoretical results versus experimental data

Cited by 128 publications

References 70 publications

Asymmetries between the production of D− and D+ mesons from 500 GeV/c π− nucleon interaction as functions of x and p2

Asymmetries between the production of D− and D+ mesons from 500 GeV/c π− nucleon interaction as functions of x and p2

Production and hadronization of heavy quarks

Evidence for PartonkTEffects in High-pTParticle Production

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