Transverse jets in high-mass diffractive excitation

The particle production from a diffractively excited proton is similar to that in DIS. A model is proposed in which transverse jets are obtained from gluon bremsstrahlung in a way similar to the emission in DIS. Such jets have been observed by the UA8 collaboration. Qualitative agreement is obtained between the model and the uncorrected data published by the UA8 collaboration. The model can be tested in an experiment with a larger acceptance than that of the UA8 detector.     

400GeV/c pp碰撞多粒子产生的不稳定性分析

对400GeV/c pp碰撞多粒子产生的实验数据作了不稳定性分析.计算了新的不稳定性参数.将它们与曹珍和华家照利用软相互作用模型ECOMB模拟NA22能量范围的强子一强子碰撞实验所得到的结果相比较,相似性清楚可见.这表明ECOMB模型是一个软相互作用多粒子产生模型.它能重现高能强子碰撞末态事例结构的涨落.     

高能多粒子产生:实验综述

本文综述了欧洲核子研究中心P(?)对撞机上多粒子产生的性质、实验数据以及截面、多重数分布、赝快度分布、横动量分布、关联、粒子产额和衍射分解等。     

Fragmentation models and unitarity

We use the diffractive excitation model to evaluate the inelastic part of the proton-proton unitarity equation. Conventional assumptions about the phase of the vacuum singularity, and an experimentally motivated choice of mass dependence for the diffractive slope, lead to an upper bound for the proportion of diffractively excited inelastic processes. We also discuss the apparent breakdown of factorization.     

Multiparticle unitarity and diffractive amplitudes

Generalizing the results of previous work, an explicit construction of elastic and inelastic diffractive amplitudes through multiparticle unitarity is given starting from a simple parametrization of non-diffractive production amplitudes. The energy dependent interference mechanism which has been previously shown to be essential to produce the diffraction peak in the elastic process is now seen to be also responsible, in a natural way, for the leading particle effect which dominates production yields.     

Diffraction dissociation,the deck mechanism and diffractive resonance production

We have constructed a model amplitude for the diffractive production of resonant states in the presence of Deck amplitudes: rescattering corrections to the Deck amplitudes are included. We have found that gross distortion of the resonance may occur and also that the phase of the diffractively produced system may vary very slowly, despite the existence of resonances: the only requirement is that the phase of the Deck amplitude leads the production phase of the resonance by ≈40°. Our model simultaneously accommodates the well established lack of phase variation in the diffractively produced 1⁺ s-wave (A1) ?π system and the details of the variation of intensity with mass, with resonance parameters M_A1 ≈ 1.3 GeV/c² and Γ_A1 ≈ 240 MeV/c². The analogous Kππ (Q) diffractive enhancement fits satisfactorily into the same framework. Our model also accounts for a number of features of diffractive N¹ production.     

Diffractive particle production and anisotropic fireball decay

A model is considered for the diffractive component of particle production with anisotropically decaying fireballs. Application of this model to recent data on diffractive proton production gives favourable results. For these data the fragmentation model with isotropically decaying fireballs cannot account. The behaviour of inclusive single particle, two-particle and multiplicity distributions are studied.     

Experimental results on strong interactions in the NAL hydrogen bubble chamber

This report presents a review of the data obtained on high-energy hadronic interactions in the 30-in. hydrogen bubble chamber at the National Accelerator Laboratory. The emphasis is on a presentation of the experimental results that have been acquired during the Laboratory's first year of operation. The five main topics discussed are (a) topological cross sections and multiplicity distributions, (b) studies of the diffraction process observed in some low multiplicity final states, (c) single particle inclusive spectra, (d) neutral particle production, and (e) multiparticle correlations.

While most of the data come from pp collisions and may be compared to results from the ISR, some of the more recent results from πp interactions are included and are compared to πp data at lower energies as well as to the pp results. The comparison between the πp and pp data indicates the striking result that many of the properties of high energy collisions seem almost independent of the nature of the projectile and target particles and depend primarily on the available center-of-mass energy.     

On the coalescence model for high energy nuclear reactions

The coalescence model for composite particle spectra from high energy collisions is formulated in a way which clarifies the underlying assumptions and the meaning of the parameters in the model. A density matrix formalism is used to describe a highly excited part formed by a collision and the coalescence volume is found to be related to the internal wave function of the composite particle and the spatial distribution of nucleons in the highly excited part.     

Roles of survival probability and barrier reduction in heavy ion fusion induced by break up

Shadowing effects in deep-inelastic lepton-nucleus scattering probe the mass spectrum of diffractive leptoproduction from individual nucleons. We explore this relationship using current experimental information on both processes. In recent data from the NMC and E665 collaboration, taken at small x ? 0.1 and Q ² ? 1 GeV ², shadowing is dominated by the diffractive excitation and coherent interaction of low mass vector mesons. If shadowing is explored at small x ? 0.1 but large Q ² ? 1 GeV ² as discussed at HERA, the situation is different. Here dominant contributions come from the coherent interaction of diffractively produced heavy mass states. Furthermore we observe that the energy dependence of shadowing is directly related to the mass dependence of the diffractive production cross section for free nucleon targets.     

Two-dimensional discrete wavelet analysis of multiparticle event topology in heavy ion collisions

The event-by-event analysis of multiparticle production in high energy hadron and nuclei collisions can be performed using the discrete wavelet transformation. The ring-like and jet-like structures in two-dimensional angular histograms are well extracted by wavelet analysis. For the first time the method is applied to the jet-like events. The jet positions are located quite well by the discrete wavelet transformation of angular particle distribution even in the presence of soft process background in nucleus-nucleus collisions at LHC energies.     

The Excited Nucleon Model for High Energy N-N Collisions

Based on the quark model, we propose a new version for a detailed analysis of the energy exchange relation in multiparticle production of high energy hadron-hadron collisions. The multiplicities of various final state hadrons are calculated in the N-N collisions for a wide energy range (s=12 ～ 485 GeV²). The result predicts an energy dependence of various multiplicities and agrees with the experimental data quite well. It can be taken as a more reliable foundation to study the increase of the K/π ratio in pA and A-A collisions.     

Projectile fragmentation in hadron-nucleus collisions at high energies

Particle production in hadron-nucleus collisions at high energies is discussed in the projectile fragmentation region. The predictions of the constituent quark model are analyzed. The contribution of diffractive interactions is explicitly taken into account. Comparison with the recent Fermilab measurements shows good agreement with the quark model and strong effects of diffractive collisions in some of the analyzed reactions.     

Multiparticle correlations in a two component dual parton model

The dual parton model (DPM) describes soft and semihard multiparticle production. The presented version of the DPM includes soft and hard mechanisms as well as diffractive processes. The model is formulated as a Monte-Carlo event generator. We calculate, in the energy range of the hadron colliders, particle ratios as function of the transverse momentum, the rise of the average transverse momenta with the charged multiplicity, forward-backward correlations, short range correlations and factorial moments as function of the size of the pseudorapidity bins. For most of these quantities we find a reasonable agreement with experimental data.     

Construction of diffractive amplitudes

Starting from a simple parametrization of production amplitudes an explicit construction of the diffractive elastic amplitude through multiparticle unitarity is given. It is shown that the phase cancellation effect is essential in order to obtain an elastic amplitude which display a diffractive peak in qualitative agreement with the data.     

Multiplicity structure of inclusive diffraction in À+ p andK + p interactions at 250 GeV/c

Results on the multiplicity structure of diffractively excited meson and proton systems in À⁺/K⁺ p interactions at 250 GeV/c are presented for diffractive masses up to about 9 GeV. The energy dependence of the average charge multiplicity and the shape of the multiplicity distribution in terms of KNO-scaling and negative binomial distribution are investigated. The diffractive systems are compared toe ⁺ e ^–,lh and non-diffractivehh final states as suggested by modern approaches of the Pomeron-hadron collision. Systematic differences are found between diffractive meson and proton systems but also between diffraction and the reactions compared to.     

Observation of diffractive b-quark production at the fermilab tevatron

We report a measurement of the fraction of b quarks produced diffractively in &pmacr;p collisions at sqrt[s] = 1.8 TeV. Diffraction is identified by the absence of particles in a forward pseudorapidity region. From events with an electron of transverse momentum 9.5相似文献