Diffractive production of Drell–Yan pairs and heavy flavors

Kopeliovich, B. Z.

doi:10.1016/s0370-2693(99)00011-8

Cited by 8 publications

(21 citation statements)

References 15 publications

(28 reference statements)

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“…By resumming higher twist terms we obtained an answer which is effectively leading twist. This result agrees with the previous predictions of [11,21]. Eq.…”

Section: Diffractive Structure Functionsupporting

confidence: 93%

“…That way we prove that due to the multiple rescattering effects diffraction becomes a leading twist effect [11], in the sense that diffractive structure function is not suppressed by extra powers of Q 2 with respect to the total structure function. At large enough Q 2 diffractive structure function should depend on center of mass energy for deep inelastic scattering, or, equivalently, on Bjorken x Bj , in the same way as the structure function F 2 .…”

Section: Introductionmentioning

confidence: 53%

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Diffractive structure function in a quasiclassical approximation

1999

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We derive an expression for diffractive F2 structure function which should be valid at small x for quasi-elastic scattering on a hadron and for quasi-elastic scattering on a large nucleus. This expression includes multiple rescatterings of the quark-antiquark pair produced by the virtual photon off the sources of color charge in a quasi-classical approximation. We find that there is a relation between such diffractive production and inclusive processes. In the former, one averages over all colors of sources before squaring the amplitude, and in the latter one first squares the amplitude and then averages it in the hadron's or nuclear wave function. We show that in the limit of a large virtuality of the photon Q 2 the diffractive structure function becomes linearly proportional to the gluon distribution of the hadron or nucleus, therefore proving that in this sense diffraction is a leading twist effect.

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“…By resumming higher twist terms we obtained an answer which is effectively leading twist. This result agrees with the previous predictions of [11,21]. Eq.…”

Section: Diffractive Structure Functionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 53%

Diffractive structure function in a quasiclassical approximation

1999

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“…It is shown that no radiation occurs without transverse momentum transfer to the quark (in contrast to gluon radiation). Therefore, the cross section for diffractive production of Drell-Yan pairs is suppressed compared to the expectation of [20] which is also based on an improper application of Eq. (A.6) to an exclusive channel.…”

Section: Introductionmentioning

confidence: 98%

“…Note that the q −q interaction emerges in (18)- (19) through the parameter λ defined in (20). In the limit λ → 0 (i.e.…”

Section: Introductionmentioning

confidence: 99%

Nonperturbative effects in gluon radiation and photoproduction of quark pairs

2000

Self Cite

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We introduce a nonperturbative interaction for light-cone fluctuations containing quarks and gluons. Theqq interaction squeezes the transverse size of these fluctuations in the photon and one does not need to simulate this effect via effective quark masses. The strength of this interaction is fixed by data. Data on diffractive dissociation of hadrons and photons show that the nonperturbative interaction of gluons is much stronger. We fix the parameters for the nonperturbative quark-gluon interaction by data for diffractive dissociation to large masses (triple-Pomeron coupling). This allows us to predict nuclear shadowing for gluons which turns out to be not as strong as perturbative QCD predicts. We expect a delayed onset of shadowing at x ≤ 10 −2 due to the fact that photon fluctuations (containing a gluon) are heavier than in the case of quark shadowing. We use the same concept to improve our description of gluon bremsstrahlung which is related to the distribution function for a quark-gluon fluctuation and the interaction cross section of aqqG fluctuation with a nucleon. We expect the nonperturbative interaction to suppress dramatically the gluon radiation at small transverse momenta. Also the Landau-Pomeranchuk suppression for gluon radiation of a quark propagating through a nucleus turns out to be smaller than predicted by perturbative QCD.

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“…These distribution are flat in x ( e −y in rapidity ) for a single collision as observed at SPS energies. Already an analysis of the ISR data in pp collisions [2,3], and later data from HERA that shows a non-zero baryon asymmetry of ≈ 8% in γp reaction at more than 7 units of rapidity from the incident baryon [4] has demonstrated that additional mechanisms with a slower x and …”

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confidence: 99%

Stopping and Baryon Transport in Heavy Ion Reactions

Videbæk

2006

J. Phys.: Conf. Ser.

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Abstract. In this report I will give an experimental overview on nuclear stopping in hadron collisions, and relate observations to understanding of baryon transport. Baryon number transport is not only evidenced via net-proton distributions but also by the enhancement of strange baryons near mid-rapidity. Although the focus is on high-energy data obtained from pp and heavy ions from RHIC, relevant data from SPS and ISR will be considered. A discussion how the available data at higher energy relates and gives information on baryon junction, quarkdiquark breaking will be made. IntroductionA major goal for relativistic heavy ion reactions is to form hot nuclear matter at energy densities in clear excess over the value (≈ 1GeV/fm 3 ) predicted from Lattice QCD needed to make the phase transition or cross over to matter dominated by degrees of freedom of quarks and gluons rather than of hadrons. The next goal is to study and quantify the properties to confront those with properties of non-perturbative QCD. Such experiments has been carried out at RHIC with considerable progress and remarkable results from the first 3 years of experiments. Please refer to the white-papers from the 4 experiments in Refs. [1]. The deposited energy is essential to understand the formation of this medium. Because baryon number is conserved, and rapidity distributions are only slightly affected by rescattering in the later stages of the collisions, the measured baryon distribution retains information about energy loss and allows the degree of nuclear stopping to be determined. Such measurements may also help distinguish between different mechanism for transporting baryons to mid-rapidity.At very low energies 1 − 15 AGeV the hadrons preserve their identity with multiple collisions and excitation to resonances being important ingredient in the description of both stopping, transverse momentum spectra as well as strange particle production. At the higher energies partonic degrees become important, and many features can be described using a string picture. At these higher energies it have long be thought that the dominant mechanism for transport of baryon number is that of quark-diquark breaking (of the strings) where the baryon number is carried(associated) with the valence quarks. I.e. the distribution will reflect the distribution q(x) −q(x). Such a mechanism is not able to move the net-baryon number over a large range of x . These distribution are flat in x ( e −y in rapidity ) for a single collision as observed at SPS energies. Already an analysis of the ISR data in pp collisions [2,3], and later data from HERA that shows a non-zero baryon asymmetry of ≈ 8% in γp reaction at more than 7 units of rapidity from the incident baryon [4] has demonstrated that additional mechanisms with a slower x and

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Diffractive production of Drell–Yan pairs and heavy flavors

Cited by 8 publications

References 15 publications

Diffractive structure function in a quasiclassical approximation

Diffractive structure function in a quasiclassical approximation

Nonperturbative effects in gluon radiation and photoproduction of quark pairs

Stopping and Baryon Transport in Heavy Ion Reactions

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