Looking for the gluonic EMC effect in associated J/ψ+γ production

Gavai, Rajiv V.; Godbole, Rohini M.; Sridhar, K.

doi:10.1016/0370-2693(93)90897-q

Cited by 8 publications

(8 citation statements)

References 21 publications

(23 reference statements)

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“…Recently, Drees and Kim advocated [5] the study of associated production of J/ψ and a photon at large p T as a clean probe of the gluon density in pp and ep collisions. We extended [6] their considerations to pA and AA collisions for the fixed target experiments at FNAL and the collider experiments at RHIC. We found that the rates for these processes at both FNAL and RHIC are substantial and a large range of x is covered by combining them, thus enabling a cleaner and better determination of ρ g .…”

Section: Introductionmentioning

confidence: 99%

Sizing up the nuclear glue in -production

Gavai¹,

Godbole

1994

Nuclear Physics A

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Nuclear gluon densities are of great importance to the physics of relativistic heavy ion collisions, in particular, in assessing the origin of J/ψ-suppression. We describe our attempts to distinguish various models of the gluonic EMC-effect, using the existing J/ψ-production data in proton-nucleus collisions. We find that no model is capable of explaining all the features of the high precision E772 data although the overall trend suggests this to be more a matter of fine-tuning the models than the presence of new physical effects.

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Section: Introductionmentioning

confidence: 99%

Sizing up the nuclear glue in -production

Gavai¹,

Godbole

1994

Nuclear Physics A

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“…In this letter, we suggest that the production of a photon in association with the quarkonium will help to clearly distinguish between these two models of quarkonium formation. The associated production of J/ψ and photon at large p T has been studied in the context of collider [8], fixed-target [9] and polarised pp scattering experiments [10], in the framework of the colour-singlet model; it has been shown to be a very sensitive probe of gluon distributions. This is so because, in the colour-singlet model, the only subprocess that contributes to J/ψ + γ production, with the J/ψ and γ produced back-to-back at large p T , is the following:…”

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confidence: 99%

Shedding light on quarkonium formation by associated photon production

Sridhar

1993

Phys. Rev. Lett.

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The process AB ->-quarkonium +7 -h X ^ for a heavy quarkonium state such as J/xj; or T, is considered. The ratio of the cross sections for this process in pp and pp collisions is shown to be a very sensitive probe of models of quarkonium formation.PACS numbers: 13.85.Ni, 13.85.Qk, 14.40.Gx Over the years, there has been considerable interest in the study of heavy quarkonia because the leptonic decay channels of these resonances provide the cleanest signals of heavy quark formation. The production of quarkonia takes place through subprocesses that are dominated by gluons. These processes have, therefore, been used to study gluon distributions in the hadron.The cross section for the production of a QQ bound state factorizes into two parts: a short-distance part, which corresponds to the production of a heavy quark pair from a hard collision of the incident particles, while the other part specifies how the QQ pair produced in the collision forms a quarkonium bound state. The shortdistance part is, of course, computable in perturbative QCD but the formation of the bound state from the QQ pair can be specified only in the context of some phenomenological model of hadronization. In particular, it is not known whether the hard scattering subprocess is sensitive to the quantum numbers of the bound state, or whether this information is completely screened by the subsequent hadronization.For several years now, two models of quarkonium formation have been used to describe J/T/? and T production in high energy collisions: the color-singlet model [1] and the semilocal duality model [2]. The latter model has also been referred to as the color-evaporation model in the literature. In the color-singlet model, one starts with the full QQ production amplitude and then projects out the state with the proper spin, parity, and chargeconjugation assignments to describe a '^^'^^Lj quarkonium state. This state is required to be a color singlet, which is achieved by the radiation of a hard parton in the final state. The matrix element so obtained is then convoluted with the modulus squared of the wave function at the origin, |i^oP {ox its derivative, in the case of P-wave quarkonia), which finally yields the matrix element for the quarkonium production process. The wave function and its derivative are fixed from the leptonic or hadronic decay widths of the quarkonia. In this model, because the amplitude for the production of a state with definite J^^ are computed, it is possible to predict the production cross section for different resonances in a given family of quarkonia. It is also important to note that the hard scattering vertex is governed by selection rules that involve the quantum numbers of the quarkonium. For example, in leptoproduction of charmonia, the ^^i state (the J/ip) is produced in the subprocess 7^ -> ^Sig, but the production of the corresponding P states (the x's) is disallowed.In the semilocal duality model, the hard scattering vertex is completely blind to the quantum numbers of the quarkonium resonance. The quant...

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“…There has been much interest recently in associated production of a J/ψ and a photon (γ) in collider [1] and fixed-target experiments [2,3]. In the framework of the coloursinglet model [4,5], the QCD subprocess that contributes to the production of a J/ψ and a photon is:…”

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confidence: 99%

“…The photoproduction process and the process in Eq. ( 1) are gluon-initiated, and have been suggested as sensitive probes of gluon densities in lepton-nucleon experiments [4], and in hadron-nucleon experiments [1,2], respectively. The J/ψ + γ mode is also the decay mode in which the P -state charmonia are detected [6,7].…”

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confidence: 99%