Soft and hard QCD dynamics in hadroproduction of charmonium

Mariotto, C. Brenner; Ingelman, G.

doi:10.1007/s100520100881

Cited by 33 publications

(33 citation statements)

References 27 publications

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“…Especially the unexpectedly large cross sections for J/ψ and ψ(2S) at large transverse momenta observed by the CDF experiment [3] renewed this interest and led to the development of the non-relativistic QCD (NRQCD) approach [4], which extends the color-singlet model by including color-octet contributions [5,6,7]. A different approach to charmonium production is based on the color evaporation model [8,9]. Both models predict the energy dependence of J/ψ production.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the J/ψ production cross section in 920 GeV/c fixed-target proton–nucleus interactions

Abt¹,

Adams²,

Albrecht³

et al. 2006

Physics Letters B

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The mid-rapidity (dσ pN /dy at y=0) and total (σ pN ) production cross sections of J/ψ mesons are measured in proton-nucleus interactions. Data collected by the HERA-B experiment in interactions of 920 GeV/c protons with carbon, titanium and tungsten targets are used for this analysis. The J/ψ mesons are reconstructed by their decay into lepton pairs. The total production cross section obtained is 3 σ J/ψ pN = 663 ± 74 ± 46 nb/nucleon. In addition, our result is compared with previous measurements.

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Section: Introductionmentioning

confidence: 99%

Measurement of the J/ψ production cross section in 920 GeV/c fixed-target proton–nucleus interactions

Abt¹,

Adams²,

Albrecht³

et al. 2006

Physics Letters B

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“…A comparison made in [1] shows that all models account quite well for the shape of the distributions. The proper normalization of CEM is obtained by chosing ρ ψ ′ = 0.066.…”

mentioning

confidence: 99%

“…Detailed comparisons between the models have been done as well as extensive comparison with data, both from fixed target experiments and the Tevatron collider [1]. Here we limit ourselves to proton beams.…”

mentioning

confidence: 99%

“…The spin statistics used in SCI predicts only a factor two suppression of ψ ′ , and must be lowered by an additional factor four in order to reproduce the data. This has prompted us to develop a more elaborate model for turning cc pairs into different charmonium resonances [1], which is briefly described here.…”

mentioning

confidence: 99%

“…Thus, we first consider the perturbative production of a cc pair at the parton level and then the non-perturbative formation of a bound charmonium state [1].…”

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confidence: 99%

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Soft and Hard QCD in Charmonium Production

Mariotto¹,

Ingelman²

2002

AIP Conference Proceedings

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Abstract. Hard and soft QCD dynamics are both important in charmonium hadroproduction, as presented here through a next-to-leading order QCD matrix element calculation combined with the colour evaporation model. Observed x F and p ⊥ distributions of J/ψ in hadroproduction are reproduced. Quite similar results can also be obtained with a Monte Carlo event generator where cc pairs are instead produced through leading order matrix elements and the parton shower approximation of higher order processes. The soft dynamics may alternatively be described by the soft colour interaction model. We also discuss the relative rates of different charmonium states and introduce an improved model for mapping the continuous cc mass spectrum on the physical charmonium resonances.The theoretical description of charmonium production separates the hard and soft parts of the process based on the factorisation theorem in QCD. Thus, we first consider the perturbative production of a cc pair at the parton level and then the non-perturbative formation of a bound charmonium state [1].Perturbative QCD (pQCD) should be applicable for cc production, since the charm quark mass m c is large enough to make α s (m 2 c ) a small expansion parameter. The leading order (LO) processes are gg → cc and qq → cc. The next-to-leading order (NLO) processes, i.e. O(α 3 s ), include the emission of a third parton and virtual corrections (where divergences are properly cancelled). The full NLO matrix elements, with explicit charm quark mass, are available in a computer program [2] giving total and differential cross sections.An alternative description of the pQCD production of cc pairs is given by the PYTHIA [3] Monte Carlo, where all LO QCD 2 → 2 processes are included with their corresponding matrix elements and the incoming and outgoing partons may branch as described by the DGLAP equations. A cc pair can then be produced as described by the LO matrix elements for qq → cc and gg → cc (with explicit m c dependence) or in a gluon splitting g → cc in the parton shower.The main free parameter is the charm quark mass m c , taken as m c = 1.5 GeV in the NLO program and m c = 1.35 GeV in PYTHIA. In both approaches, the factorization and renormalization scales are taken as the average transverse mass of the c andc.The formation of bound hadron states occurs through processes with small momentum transfers such that α s is large and prevents the use of perturbation theory. The lack of an appropriate method to calculate non-perturbative processes, forces us to use phe-

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Associated production of a quarkonium and a Z boson at one loop in a quark-hadron-duality approach

Lansberg

Shao

2016

J. High Energ. Phys.

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In view of the large discrepancy about the associated production of a prompt J/ψ and a Z boson between the ATLAS data at √ s = 8 TeV and theoretical predictions for Single Parton Scattering (SPS) contributions, we perform an evaluation of the corresponding cross section at one loop accuracy (Next-to-Leading Order, NLO) in a quarkhadron-duality approach, also known as the Colour-Evaporation Model (CEM). This work is motivated by (i) the extremely disparate predictions based on the existing NRQCD fits conjugated with the absence of a full NLO NRQCD computation and (ii) the fact that we believe that such an evaluation provides a likely upper limit of the SPS cross section. In addition to these theory improvements, we argue that the ATLAS estimation of the Double Parton Scattering (DPS) yield may be underestimated by a factor as large as 3 which then reduces the size of the SPS yield extracted from the ATLAS data. Our NLO SPS evaluation also allows us to set an upper limit on σ eff driving the size of the DPS yield. Overall, the discrepancy between theory and experiment may be smaller than expected, which calls for further analyses by ATLAS and CMS, for which we provide predictions, and for full NLO computations in other models. As an interesting side product of our analysis, we have performed the first NLO computation of dσ/dP T for prompt single-J/ψ production in the CEM from which we have fit the CEM non-pertubative parameter at NLO using the most recent ATLAS data.

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Soft and hard QCD dynamics in hadroproduction of charmonium

Cited by 33 publications

References 27 publications

Measurement of the J/ψ production cross section in 920 GeV/c fixed-target proton–nucleus interactions

Measurement of the J/ψ production cross section in 920 GeV/c fixed-target proton–nucleus interactions

Soft and Hard QCD in Charmonium Production

Associated production of a quarkonium and a Z boson at one loop in a quark-hadron-duality approach

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