Dual Parton Model Research Articles

Comparing multiparticle production within a two-component dual parton model with collider data.

The dual parton model (DPM) is very successful in describing hadronic multiparticle production. The version of DPM presented includes both soft and hard mechanisms. The hard component is described according to the lowest-order perturbative QCD-parton-model cross section. The model is formulated in the form of a Monte Carlo event generator. Results obtained with this event generator are compared with data on inclusive reactions in the TeV energy range of the CERN and Fermilab hadron colliders.

New results in the dual parton model

New results in the dual parton model

Description of inelastic nucleus-nucleus interactions at medium energy using dual parton model

It is shown that the dual parton model taking into account the processes of diffraction dissociation to the low mass states and finite energy corrections to the asymptotic Abramovski-Gribov-Kancheli cutting rules allows satisfactory description of existing experimental data on hardon-nucleus and nucleus-nucleus interactions at medium energy.

Charge distribution in scattering off nuclei: a test of the production mechanism

In the dual parton model, the absolute value of the charge in the forward hemisphere in collisions of negative particles with nucleons increases with energy. This effect is strongly amplified in collisions with nuclei when the number of struck nucleons increases. It can provide a crucial test of the particle production mechanism.

Hadron production in hadron-nucleus and nucleus-nucleus collisions in a dual parton model modified by a formation zone intranuclear cascade

The concepts of the formation zone and formation zone intranuclear cascade are discussed. The dual parton Monte Carlo model is modified by the leading order formation zone cascade. The properties of the resulting model are presented and discussed. It is found that especially rapidity or pseudorapidity distributions change strongly with the value of the formation zone parameter. A comparison with data leads to a phenomenological value of the formation zone parameter of τ0 c≈5 to 10 fm. This corresponds roughly to an average formation zone of 1 fm in the rest frame of the secondary produced.

The dual parton model

The dual parton model

A Monte Carlo generator for cosmic-ray collisions

A MC generator incorporating the new features of hadronic multiproduction, observed at the CERN collider with the European hybrid spectrometer, has been developed using considerations based on the dual parton model. This semi-empirical model is especially efficient at reproducing the complex characteristics of semi-inclusive data under the principle of scaling in the central region for relative rapidity density against z, and violation of KNO scaling. Extended to include p-A collisions, such as a triple-Gaussian random generator, it has been inserted in a cosmic-ray cascade simulation.

Charge and energy flow in π+ p,K + p andpp interactions at 250 GeV/c

We present data on the flow of energy and charge in π+ p,K + p andpp interactions at 250 GeV/c. The energy and charge flow in the beam c.m. hemisphere is analysed in terms of the cluster-invariant Bialas-Ochs-Stodolsky variable λ=cot θ/E jet. The profile functionsdQ/dλ anddE/dλ indicate a widening inp T of jets between 32 and 250 GeV/c incident laboratory momentum, whereas the ratiodQ/dE is energy independent. The data are compared to μp deep-inelastic scattering resutls and to expectations from the single string LUND model, the Dual Parton Model and the two-string LUND model (FRITIOF).

Unusual phenomena in the rapidity distribution and the phase transition of the quark-gluon plasma.

Meson as well as baryon production as a phase transition of a quark-gluon plasma is discussed in the context of a two-dimensional (rapidity, proper time) model with Kadanoff scaling. Unusual features of the model, not met in perturbative QCD or in the dual parton model, are the possible appearance in the fragmentation region below an energy limit of events with exceptionally high-multiplicity, meson cluster production appearing as secondary maxima of the fixed-n central meson distribution, as well as sharp baryon spikes near the target and projectile-fragmentation regions.

High-energy p-A collisions and hadron-electron cascades

A Monte Carlo generator for p-A collisions has been developed which employs some concepts include in the dual-parton model and which has been adapted to reproduce some results obtained by the European Hybrid Spectrometer at CERN at 360 GeV/c. The important effect of the violation of KNO scaling which increases with A and with primary energy, on the behaviour of cascades in dense media is illustrated by a Monte Carlo simulation of hadron-electron showers and subsequent comparison with CERN results at 300 GeV. These effects are expected to be even more important at cosmic-ray energies.

The transverse-energy distributions of 32S-nucleus collisions at 200 GeV per nucleon

Transverse-energy distributions have been measured for the collisions of the 32S nucleus with Al, Ag, W, Pt, Pb, and U target nuclei, at an incident energy of 200 GeV per nucleon. The shapes of these distribution reflect the geometry of the collisions, including the deformation effects. For central collisions, the transverse-energy production in the region −0.1< η lab<2.9 increases approximately as A 0.5, where A is the atomic mass number of the target. This increase is accompanied by a relative depletion in the forward region η lab > 2.9. These results are compared with those obtained under similar conditions with incident 16O nuclei. A comparison is also made with the predictions of a Monte Carlo generator based on the dual parton model. Finally, we give estimates of the energy density reached and its dependence on the atomic mass number of the projectile.

Dynamical models of ultrarelativistic nuclear collisions

We discuss two dynamical models for nuclear collisions : the Dual parton model (DPM) and the Fritiof Lund model and their Monte Carlo implementations. The model predictions are compared with the CERN results obtained with Oxygen and Sulfur projectiles and agreement is generally found. Possible consequences of such an agreement on the issue of quark gluon plasma (QGP) formation are discussed.

Pp collisions at ISR energies: Rapidity distributions for fixed multiplicities

We report calculations on the rapidity distribution of charged particles for specified multiplicities, observed in proton-proton collisions for CM energies √ s=24–63 GeV. The analysis is done in the framework of the dual parton model; the predictions are compared to ISR experiments.

The transverse energy distribution in16O-nucleus collisions at 60 and 200 GeV per nucleon

Transverse-energy distributions have been measured in the pseudorapidity region −0.1<η lab<2.9 for oxygen-nucleus collisions at incident energies of 60 and 200 GeV per nucleon for Al, Ag, and W target nuclei. The cross-section for the heaviest target nuclei at the highest incident energy is measured over 5 orders of magnitude and out to a maximumE T of 200 GeV. Measurements of the differential densitydE T/dη lab as a function ofη lab are presented. In the pseudorapidity region −0.1<η lab<2.9 the transverse energy for an average central collision is proportional to ≈A 0.5, while the fraction of the total transverse energy measured in an extended region ofη lab>2.9 decreases with increasingA. The distributions are compared with the predictions of a dual parton model. Finally the question of the energy density is addressed.

Multiplicity dependence of the average transverse momentum in π + p, K + p and pp collisions at 250 GeV/c

The average transverse momentum 〈 P t 〉 has been studied as a function of the charge multiplicity n in π +p, K +p and pp collisions at 250 GeV/c ( s ≈ 22 GeV) and compared to that at other energies. The effect of cuts in rapidity and p T is demonstrated. A comparison to currently used low- p T models shows that the two-chain dual parton model underestimates the experimentally observed correlation at large p T. The new version of the two-chain LUND-FRITIOF model is better than the first version of this model, but still overestimates the correlation.

A unified approach for hadronic and nuclear collisions: The dual parton model

A unified approach for hadronic and nuclear collisions: The dual parton model

Two-particle correlations in 360 GeV/cp p interactions

Two particle correlations of hadrons produced in 360 GeV/cpp interactions are investigated in the transverse plane and in rapidity. The data were obtained at the European hybrid spectrometer equipped with a rapid cycling bubble chamber. The observed transverse and rapidity correlations are compared with the one string LUND-and a two string dual parton-model. These models predict in general stronger correlations in the transverse plane and much weaker correlations in rapidity than found in the data. The LUND-FRITIOF-and multichain dual parton models provide a better reproduction of the data, although the agreement is not yet satisfactory. Only the UA5 cluster model GENCL shows agreement with the data.

Leading baryon spectrum in high-energy nuclear collisions

We compute the leading baryon spectrum in high-energy nuclear collisions in the framework of the Dual parton model. Nucleus-nucleus collisions are treated in full detail. The average rapidity shift of the leading baryon (nuclear stopping power) is studied as a function of the degree of centrality of the collision and the cross-section of the selected events is given. Important differences are found here between proton-nucleus and nucleus-nucleus interactions. The agreement with existing data on proton-nucleus and α−α collisions is quite good.

Delayed thresholds and heavy-flavor production in the dual parton model.

It is shown that the two-chain structure of the cut Pomeron in the dual parton model for low-${p}_{T}$ multiparticle production provides a natural explanation for the phenomenon of delayed thresholds for heavy-flavor production in proton-proton collisions.

Minijets, QCD, and unitarity.

We introduce the minijet cross section, computed from QCD, together with a standard soft component, into a unitarization scheme (eikonal model) and show that most of the increase of the inelastic cross section between CERN ISR and SPS collider energies is due to the soft component. We also show that the main properties of minijet production, observed by the UA1 collaboration, can be understood by the introduction of semihard scattering in the dual parton model.