New extraction of color-octet NRQCD matrix elements from charmonium hadroproduction

Sanchis-Lozano, Miguel-Angel

doi:10.1016/s0920-5632(00)00620-4

Cited by 9 publications

(19 citation statements)

References 15 publications

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“…using PYTHIA machinery whenever possible. In fact, it provides an energy depletion of the fragmenting gluon in agreement with previous work on charmonium hadroproduction [20,12]. In Figure 8 the x AP factor is plotted as a function of the transverse momentum of the resonance for the Tevatron event generation.…”

supporting

confidence: 85%

“…A p T lower cut-off was set equal to 1 GeV (by default in PYTHIA) throughout the generation since some of the contributing channels are singular at vanishing transverse momentum [12]. Furthermore, all fits of Tevatron data were performed using p T values above 2 GeV.…”

Section: Appendicesmentioning

confidence: 99%

“…Also gluon quark scattering gq→g * q followed by g * →Υ(nS)X, can give a sizeable contribution (about 20% at p T > 20 GeV, see table 6 in appendix A). Consequently, the expression (12) for the ratio of gluon densities has to be modified to include the quark distribution q(x, µ 2 ) in protons:…”

Section: Introducing the Gluon Quark Contributionmentioning

confidence: 99%

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Results from bottomonia production at the Tevatron and prospects for the LHC

Domenech-Garret

Sanchis-Lozano

2001

Nuclear Physics B

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We extend our previous analysis on inclusive heavy quarkonia hadroproduction to the whole Υ(nS) (n=1,2,3) resonance family. We use a Monte Carlo framework with the colour-octet mechanism implemented in the PYTHIA event generator. We include in our study higher order QCD effects such as initial-state emission of gluons and Altarelli-Parisi evolution of final-state gluons. We extract some NRQCD colour-octet matrix elements relevant for Υ(nS) (n=1,2,3) hadroproduction from CDF data at the Fermilab Tevatron. Then we extrapolate to LHC energies to predict prompt bottomonia production rates. Finally, we examine the prospect to probe the gluon density in protons from heavy quarkonia inclusive hadroproduction at high transverse momentum and its feasibility in LHC general-purpose experiments.

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supporting

confidence: 85%

Section: Appendicesmentioning

confidence: 99%

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Results from bottomonia production at the Tevatron and prospects for the LHC

Domenech-Garret

Sanchis-Lozano

2001

Nuclear Physics B

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“…We have implemented COM in the event generator PYTHIA with initial-state radiation of gluons [5,6] and Altarelli-Parisi evolution of final-state gluons in the same way that earlier.…”

Section: Higher Order Qcd Effects; Generating υ(Ns)mentioning

confidence: 99%

“…Nevertheless, it is reasonable to assume that, on the average, the virtual g * should evolve at high p T similarly to the other final-state gluon -which actually is evolved by the PYTHIA machinery. We used this fact to simulate the (expected) evolution of the (ungenerated) g * whose momentum was assumed to coincide with that of the resonance (neglecting the effect of emission/absorption of soft gluons by the intermediate coloured state bleeding off colour [6]). …”

Section: Higher Order Qcd Effects; Generating υ(Ns)mentioning

confidence: 99%

Bottomonia hadroproduction

Garret

Sanchis-Lozano

2001

Nuclear Physics B - Proceedings Supplements

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We analyze Tevatron data of bottomonium hadroproduction in the framework of the colour-octet model (COM) implemented in the event generator PYTHIA [1] using CTEQ4L PDF taking into account initial-state radiation of gluons and Altarelli-Parisi evolution of final-state gluons. We obtain new values for the colour-octet matrix elements (Me's) relevant to this production process for the Υ(nS) family (n=1,2,3), finding that 1 S (8) 0contributions are not needed in the fit. We show the different contributions to Υ(1S) production at Tevatron for PT > 8 GeV, comparing them with CDF data. Remarkably we find a quite small contribution (compatible with zero) from feeddown of χ bJ states produced through the colour-octet mechanism: Υ(1S) indirect production via χ bJ decays should be mainly ascribed to the colour-singlet model. Finally we extrapolate to LHC energies to predict Υ(nS) production rates. HIGHER ORDER QCD EFFECTS; GENERATING Υ(nS)In a previous work [2], we extracted colouroctet Me's for Υ(1S) hadroproduction using CTEQ2L parton distribution funcion (PDF) [3]; in this work we extend this study to the upper resonances Υ(2S) and Υ(3S), using the improved CTEQ4L PDF [4]. We have implemented COM in the event generator PYTHIA with initial-state radiation of gluons [5,6] and Altarelli-Parisi evolution of final-state gluons in the same way that earlier.First we repeat our fit of the Υ(1S) differential cross section with CTEQ4L PDF. We generated separately each source: direct Υ(1S) production from both Colour Singlet Model (CSM) and COM. Indirect source comes from electromagnetic decays of χ bJ (1P ) and χ bJ (2P ) and contributions from strong and electromagnetic decays of Υ(2S) and Υ(3S); the M 5 = 5× m 2 b + * Work partially supported by CICYT under contract AEN99-0692 † E-mail:domenech@evalo1.ific.uv.es mas@evalo1.ific.uv.escombination is also taken into account (although later we shall see that actually this contribution is not needed). For the CSM Me's we take the values from the Buchmuller and Tye QCD potencial [7]. We make use of the Heavy Quark Spin Symmetry in order to relate the different matrix elements. We set the Υ(1S) mass as 9.46 GeV (the mass of the coloured intermediate state was set as 2M b = 9.76 GeV, the difference is accounted for by soft gluon emission) whereas for χ bJ (nP ) we took a weighted mean of their real masses [8]. For Υ(2S) we consider direct CSM contribution and the decay from Υ(3S) and χ bJ (2P ). COM contribution also is taken into account. For χ bJ (2P ) we set its real mass. Regarding the Υ(3S) state we consider only direct production for both CSM and COM contributions; we set its real mass, excluding any χ bJ (3P ) decays.We have included the higher order QCD effects on the partonic cross sections caused by:• Intrinsic Fermi motion of partons inside the hadrons. This non perturbative effect is relevant at small P t values.

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Quarkonium production at high-energy colliders

Krämer¹

2001

Progress in Particle and Nuclear Physics

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The theoretical description of heavy quarkonium production at high-energy pp and ep colliders is reviewed. Predictions based on non-relativistic QCD factorisation are confronted with recent charmonium and bottomonium data from the Tevatron and HERA. Potential shortcomings of the present theoretical analyses are discussed, and the prospects for quarkonium physics at the upgraded Tevatron and HERA colliders and at the LHC are summarised.

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New extraction of color-octet NRQCD matrix elements from charmonium hadroproduction

Cited by 9 publications

References 15 publications

Results from bottomonia production at the Tevatron and prospects for the LHC

Results from bottomonia production at the Tevatron and prospects for the LHC

Bottomonia hadroproduction

Quarkonium production at high-energy colliders

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