Relating multihadron production in hadronic and nuclear collisions

The energy-dependence of charged particle mean multiplicity and pseudorapidity density at midrapidity measured in nucleus–nucleus and (anti)proton–proton collisions are studied in the entire available energy range. The study is performed using a model, which considers the multiparticle production process according to the dissipating energy of the participants and their types, namely a combination of the constituent quark picture together with Landau relativistic hydrodynamics. The model reveals interrelations between the variables under study measured in nucleus–nucleus and nucleon–nucleon collisions. Measurements in nuclear reactions are shown to be well reproduced by the measurements in pp/[`(p)]p{\bar{\mathrm{p}}}{\mathrm{p}} interactions and the corresponding fits are presented. Different observations in other types of collisions are discussed in the framework of the proposed model. Predictions are made for measurements at the forthcoming LHC energies.     

Fluctuations of single-particle density in nuclear collisions

In order to incorporate fluctuations into the extended TDHF, a new approach is proposed. The evolution of the single-particle density is considered as a “generalized Langevin process” in which the correlated part of the two-body collisions acts as a “random force”. In the semi-classical approximation, the correlation function of the random force is calculated. A possible algorithm for the numerical solution is discussed.     

Physics of non-Abelian matter in high energy hadronic and nuclear collisions

A brief review of the recent studies of the properties of dense non-Abelian matter is given. A particular emphasis is made on collective effects such as Cherenkov gluon radiation, ridge structure in proton-proton collisions and modification of QCD cascades in dense matter.     

Quark dynamics in soft hadronic collisions and fragmentation on nuclear targets

Additive and collective pictures of quark dynamics in hadron-hadron collisions lead to different predictions for attenuation effects on nuclear targets and can be distinguished experimentally.     

Radiative corrections in hadronic collisions

A general treatment of radiative corrections to any two-body hadronic reaction is presented and applied to specific collisions of pions, kaons and protons with nuclei. The results are found to be significant compared to the accuracies of available data.     

Charge distributions in hadronic collisions

The distribution of charge versus rapidity is examined in the framework of available parton models for multiparticle production in hadron-hadron collisions. Fragmentation models with a twochain Pomeron contribution (based on the dual topological unitarization scheme) are shown to describe rather well the recently measured data on charge distributions in high energypp and πp collisions (140 GeV/c≦p _LAB≦360 GeV/c). Carefully measured charge distributions at still higher energies which will be accessible in the near future offer a possibility of distinguishing between some of the current theoretical approaches.     

Strangeness distributions in hadronic collisions

The distribution of strangeness versus rapidity is studied in the multichain fragmentation model and in the one chain fragmentation model. It is shown that the multichain model describes rightly theK ⁺ p strangeness distribution data.     

Limiting fragmentation in hadronic collisions

I discuss the phenomenon of the limiting fragmentation in the hadronic collisions. The calculation of the multiplicities is presented, based on the inclusive gluon production within the kT$k_T$ factorization framework using the gluon distributions obtained from the nonlinear equation at small x.     

Prospects of technicolor-signatures in hadronic collisions

Within the context of the Dimopoulos' one family model, we consider possible technicolor signatures in hadronic reactions at high energies. For the single-production of light color-singlet states (P ⁰,P ³,P ^±) in \(p\bar p\) annihilation, we find the Compton-scattering processgc→P ⁰ c most promising. In case of PGB-pair-production, the reaction in \(p\bar p \to P^ + P^ - \) via the subprocess \(q\bar q\xrightarrow{{\gamma ,Z^0 }}P^ + P^ - \) , as well as the production of heavy color-triplets (P ₃) via \(p\bar p \to P_3 \bar P_3 \) via \(q\bar q\) andgg-fusion at Tevatron-energies, appear to be best suited for detecting these objects.     

Forward jets and energy flow in hadronic collisions

We observe that at the Large Hadron Collider, using forward + central detectors, it becomes possible for the first time to carry out calorimetric measurements of the transverse energy flow due to “mini-jets” accompanying production of two jets separated by a large rapidity interval. We present parton-shower calculations of energy flow observables in a high-energy factorized Monte Carlo framework, designed to take into account QCD logarithmic corrections both in the large rapidity interval and for hard transverse momentum. Considering events with a forward and a central jet, we examine the energy flow in the interjet region and in the region away from the jets. We discuss the role of these observables to analyze multiple parton collision effects.     

Coherence and self-induced transparency in high-energy hadronic collisions

Two consequences of coherence of mesonic fields have been tested in proton-nucleus collisions. Multiplicity fluctuations measured in finite rapidity intervals are found to obey a Poisson distribution at large rapidities where nuclear transparency occurs. In close analogy to quantum optics we present a quark-parton model in which this link between coherence and transparency is realized via the phenomenon of self-induced transparency.     

Multijet events in soft and semihard hadronic collisions

Various phenomena suggest the importance of a hard component in soft hadronic collisions with large cross sections already at moderate energies below \(\sqrt s \sim 30 GeV\) which involve the valence quarks. We consider Born term models based on one gluon exchange and hadron quark couplings either pointlike or with additional largep _T damping. A resolution dependent multijet analysis-performed in a way similar toe ⁺ e ^?-annihilation-can yield important information about the elements of a perturbative approach. Predictions are presented for multijet rates and properties of 2 and 3 jet events in the low resolution regime. Some results for 2 jet events do also apply for higher energies and high resolution.     

Asymmetric di-jet production in polarized hadronic collisions

Using the collinear QCD factorization approach, we study the single-transverse-spin dependent cross section Δσ(S) for the hadronic production of two jets of momenta P₁=P+q/2 and P₂=−P+q/2. We consider the kinematic region where the transverse components of the momentum vectors satisfy PqΛ_QCD. For the case of initial-state gluon radiation, we show that at the leading power in q/P and at the lowest non-trivial perturbative order, the dependence of Δσ(S) on q decouples from that on P, so that the cross section can be factorized into a hard part that is a function only of the single scale P, and into perturbatively generated transverse-momentum dependent (TMD) parton distributions with transverse momenta .