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.     

Fluctuations in hadronic and nuclear collisions

We investigate several fluctuation effects in high-energy hadronic and nuclear collisions through the analysis of different observables. To introduce fluctuations in the initial stage of collisions, we use the interacting gluon model (IGM) modified by the inclusion of the impact parameter. The inelasticity and leading-particle distributions follow directly from this model. The fluctuation effects on rapidity distributions are then studied using Landau's hydrodynamic model in one dimension. To investigage further the effects of the multiplicity fluctuation, we use the longitudinal phase-space model, with the multiplicity distribution calculated within the hydrodynamic model, and the initial conditions given by the IGM. Forward-backward correlation is obtained in this way.     

Angular distribution of dileptons in hadronic collisions

The polar and azimuthal angular distributions of the lepton pair produced in hadron-hadron collisions are studied. For large Q_T these are calculated from lowest-order QCD diagrams. For low Q_T we present simple expressions which take into account the effect of primordial quark transverse momentum on the angular distributions.     

Pion interferometry of ultra-relativistic hadronic collisions

Pion interferometry of ultra-relativistic hadronic collisions is described in the context of the inside-outside cascade model using a current ensemble method. In contrast to the usual gaussian and Kopylov parameterizations involving only geometrical variables, the correlation function in this model depends on a special combination of dynamical as well as geometrical parameters.     

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 .     

Seeing the B mesons in hadronic collisions

The weak decays B→ψ(J) + X are investigated. It is argued that these decays are dominated by B→ψ(J)Kπ (branching ratio of about 1%). Detailed predictions for these decays are made.     

QCD expectations for high-energy hadronic collisions

It is argued that perturbative QCD effects could be important in low-momentum transfer hadronic collisions at very high energies and should then give rise to several distinctive phenomena.     

Scaling of single photon production in hadronic collisions

Scaling of single photon production in pp and collisions is studied. It is empirically observed that the available data scales for and for larger . The NLO pQCD predictions for pp collisions at an of 200 and 5500 GeV, relevant for RHIC and LHC energies are seen to closely follow this scaling behavior. Implications for single photon production in heavy ion collisions are discussed. Received: 2 February 2001 / Revised version: 28 May 2001 / Published online: 5 October 2001     

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.     

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.