Dual Parton Model Research Articles

Multiplicity distributions in nuclear collisions.

Multiplicity distributions in nuclear collisions are calculated in the framework of the dual parton model. A comparison with experimental data is performed. The multiplicity distributions for /sup 16/O-/sup 207/Pb collisions at 200 Gev/c per nucleon is predicted. The fluctuations of the energy density in the central rapidity region for such collisions are estimated.

Nuclear collisions in the dual parton model

After a brief description of the Dual parton model and of the main results obtained in hadron-hadron, hadron-nucleus and nucleus-nucleus collisions, we present some recent results on the leading baryon and charged particle spectra in nuclear collisions.

Comments on nuclear stopping power

A new estimation is given of nuclear stopping power based on recent ACCMOR data and the dual parton model. In comparison with previous analyses weaker deceleration of nucleons by nuclear matter is found.

Event selection criteria in nucleus-nucleus collisions

Several event selection criteria in ultrarelativistic nucleus-nucleus collisions are analysed in the framework of the dual parton model. First, central and semicentral collisions are compared. We conclude that semicentral processes are more appropriate to observe high energy density events, where the formation of a quark-gluon plasma could take place. Secondly, the dependence of the achieved energy density on the degree of centrality of the collision is studied. We analyse the implications of our results for future experiments at CERN.

Symmetric fragmentation of jets and Regge behaviour

A new cascade model of hardron fragmentation is proposed, which satisfies the following properties of the multiperipheral model: i) symmetry under rapidity reversal; ii) strong cut-off in momentum transfer squared; iii) physical multi-Regge and triple-Regge limits. The model is applied to the dual cut pomeron. Improvements over the dual parton models are pointed out. The possibility of treating higher orders of the reggeon field theory, such as diffraction, exchange of several cut pomerons and enhanced diagrams, is discussed.

Transverse momenta in minimum-bias events at collider energies.

The origin of transverse momenta in minimum-bias events is investigated within the framework of the dual parton model. A Monte Carlo code nicely reproduces almost all available data in a purely soft framework. However, to obtain the multiplicity dependence of the average transverse momentum, it is necessary to attribute transverse momenta to the initial partons which exceed soft values. Without drastically changing the general picture of particle production, the scattering process has to contain a sizable ``semihard'' component.

High mass diffraction dissociation in the dual parton model

It is shown that, in the dual parton model, the final states produced in single diffractive dissociation at fixed mass M, are identical to those in non-diffractive inelastic π p collisions at √ s = M. This is striking agreement with recent data from the UA4 Collaboration at the SPS Collider.

Charged particle spectra in αα and αp collisions at the CERN ISR

Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentump T . The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty≃0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. Thep T distributions depend weakly on the multiplicity.

Leading proton and antiproton distributions in proton-nucleus and antiproton-nucleus interactions

We present a study of leading protons and antiprotons inp-nucleus and $$\bar p$$ -nucleus on Be, Cu, Ag, W, and U targets. The experiment was performed at the CERN-SPS at a beam energy of 120 GeV. For all targets a suppression of secondary antiprotons with respect to protons is observed. The difference between the $$\bar p$$ andp spectra increases with decreasing χ-values and the effect is stronger for heavier nuclei. The features of the data are qualitatively consistent with multiple-collisions modesls. The data are analysed in terms of a dual parton model which gives a satisfactory description of leadingp and $$\bar p$$ spectra.

On distributions of antibaryons in $$\bar p$$ -Nucleus inelastic collisions

In the framework of the dual parton model we calculate the spectra of secondary antibaryons in\(\bar p\)-nucleus non-annihilation inelastic interactions. We find that the number of antibaryons in the backward hemisphere in the\(\bar p\)-nucleon centre-of-mass frame can grow with the atomic number of the nucleus.

Broken KNO scaling in the multi-pomeron exchange model and multiplicity distributions at collider energy

Under the assumption that planar superclusters in the dual parton model obey the KNO scaling, we find that the production amplitude obtained by cutting a cylinder (pomeron) configuration breaks the KNO scaling badly. But it is also shown that contributions from multi-pomeron exchange configurations compensate or overcompensate this break and lead again an approximate or broken KNO scaling at SPS collider energy.

High energy nucleus-nucleus collisions in the dual parton model

Average multiplicities, rapidity densities and dispersion in high-energy nucleus-nucleus collisions are computed in the framework of the dual parton model. Particular attention is devoted to the case of central collision, especially in connection with the possible production of a quark-gluon plasma. Our results are compared with recent cosmic ray data. A comparison of the predictions of different models is also given.

High order moments of the $$\bar p$$ p multiplicity distribution in the dual parton model

The first four moments of the\(\bar p\)p multiplicity distribution are computed in the framework of the dual parton model at ISR, SPS collider and Tevatron energies, and for different rapidity intervals. Our results exhibit a striking dependence of the various moments on the size of the rapidity interval which is characteristic of the nature of the rescattering chains in the dual parton model. They also show a violation of KNO scaling throughout the considered energy range. Our results indicate that only light clusters (consistent with known resonances) are produced at all energies.

Long-range rapidity correlations in hadron-nucleus interactions

Long-range rapidity correlations between particles produced in proton-nucleus interactions at 200 GeV/c are studied in the multichain dual parton model. A large long-range correlation between particles produced in two rapidity intervals is predicted, provided these two rapidity intervals are properly chosen. The predicted effect is easily measurable. Predictions at 1 TeV are also given.

High order moments of the $$\bar pp$$ multiplicity distribution in the dual parton model

The first four moments of the $$\bar p$$ p multiplicity distribution are computed in the framework of the dual parton model at ISR, SPS collider and Tevatron energies, and for different rapidity intervals. Our results exhibit a striking dependence of the various moments on the size of the rapidity interval which is characteristic of the nature of the rescattering chains in the dual parton model. They also show a violation of KNO scaling throughout the considered energy range. Our results indicate that only light clusters (consistent with known resonances) are produced at all energies.

Particle production in hadron-hadron collisions at collider energies in an exclusive multi-string fragmentation model

Particle production in soft hadron-hadron collisions at collider energies is investigated in a two-step dual parton model. In the initial collision color-singlets or strings of hadronic matter are formed from constituents of the incident particles. These strings subsequently decay into chains of hadrons, analogously to the\(q\bar q\) system in low energye+e− physics. Relying on the Monte-Carlo method we generate exclusive events and evaluate quantities of interest which include inclusive and semi-inclusive pseudorapidity spectra, topological cross-section, correlations and charge transfer distributions.

Dynamical correlations in the Dual Parton Model

The effect of multiple ‘chain’ contributions to particle production, which appears in the Dual Parton Model at collider energies, is investigated in an exploratory model, in which other sources of correlations are largely neglected. Attention is given to the question of KNO scaling for the multiplicities observed in restricted or unrestricted rapidity ranges. The rapidity distribution associated with a fixed number of particles within a suitably chosen interval, is found to be sensitive to details of the mechanism of multiple chain production.

Correlations in the dual parton model

We show that the dual parton model with the help of the recursive cascade model for the fragmentation functions is able to describe rightly the single and two-particle inclusive distributions at ISR energies. No free parameter is needed in such a description.

Comparison of antiproton diffraction dissociation with inelastic $$\bar pp$$ interactions ande + e − annihilation into hadrons

Experimental multiplicity distributions of antiproton diffraction dissociation and inelastic antiproton-proton interactions at 22.4 GeV/c with leading particles removed are compared withe+e− annihilation into hadrons. We find agreement with the predictions of the dual parton model.

Forward-backward correlations at SPS energies and the nature of multiple-scattering

We study the forward-backward rapidity correlation slope in\(\bar p\)p interactions at high energies. We show that the measurement of this slope in different rapidity intervals, yields direct information on multiple-scattering. It turns out that the particles produced in inelastic rescattering are concentrated neary=0. This is a key feature of the multi-chain dual parton model, and leads to a simple explanation of the main features of multi-hadron production at very high energies, such as the energy dependence of the height and shape of the rapidity distribution, approximate K.N.O. scaling etc. We also show that the large values of the forward-backward correlation slope measured at ISR and SPS, are obtained in the model using the standard idea of short-range order in a single inelastic collision.