Two-particle Inclusive Distributions Research Articles

Soft-gluon resummation for the fragmentation of light and heavy quarks at large x

We present a QCD study of fragmentation processes for light and heavy quarks in the semi-inclusive region of large x. Large logarithmic terms, due to soft-gluon radiation, are evaluated and resummed to all perturbative orders in the QCD coupling α S. Complete analytical results to next-to-leading logarithmic accuracy are given for one-particle and two-particle inclusive distributions in e + e − annihilation and DIS. Factorization of parton radiation at low transverse momenta is exploited to identify the universal (process-independent) perturbative fragmentation function that controls heavy-quark processes, and to perform next-to-leading logarithmic resummation of its soft-gluon contributions. To gauge the quantitative impact of resummation, we perform numerical studies of light- and heavy-quark fragmentation in e + e − collisions.

One- and two-particle inclusive distributions in pion- and proton-nucleus interactions at 300 GeV

We report the data on 300 GeV pion-emulsion-nucleus reactions and compare the results to proton-emulsion-nucleus reactions at the same energy. In particular we present results on the one- and two-particle inclusive pseudorapidity distributions. Two-particle distributions are investigated by using the correlation function formalism. The dependence of one-particle inclusive spectra on the projectile and nuclear excitation obeys scaling. Short-range correlations are observed for pairs of charged particles. No differences are observed between the analogous correlations in pion- and proton-nucleus interactions.

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.

QCD three-jet production in large- p⊥ processes

The contribution of the hard scattering subprocess quark + quark → quark + quark + gluon to two-particle inclusive distributions at large p ⊥ is studied. It is shown to be accessible experimentally, and agrees with recent data on azimuthal distributions in the adequate kinematical region.

Asymptotic Behavior of an Analytically Solvable Nova Model

We formulate an analytically solvable version of the nova model and obtain the $s$ dependence of single- and two-particle inclusive distributions. The nature of the singularity in the two-particle distribution at ${x}_{1}={x}_{2}=0$ and numerical predictions for National Accelerator Laboratory energies are discussed.

Two-Particle Correlations in Inclusive Reactions

Two-particle inclusive distributions and correlation functions are computed from a model which emphasizes single production of resonance-like hadrons (novas) which cascade decay through pion emission. Strong positive correlations are predicted at small values of the center-of-mass rapidity of the final pions. The magnitude and energy dependence of $〈{n}_{{\ensuremath{\pi}}^{\ensuremath{-}}}〉$ and $〈{n}_{{\ensuremath{\pi}}^{\ensuremath{-}}}({n}_{{\ensuremath{\pi}}^{\ensuremath{-}}}\ensuremath{-}1)〉$ are reproduced correctly. Good agreement is obtained with experimental $\frac{d\ensuremath{\sigma}}{\mathrm{dy}}$, $\frac{{d}^{2}\ensuremath{\sigma}}{d{y}_{1}d{y}_{2}}$, and $C({y}_{1}, {y}_{2})$ from data on ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}X$ at 18.5 GeV/c.

On two-particle correlations in high energy production experiments

One-particle and two-particle inclusive distributions are considered in the light of future production experiments at CERN Intersecting Storage Rings machine. We discuss the general properties of those models which are based on factorized approximations to the production amplitudes and are in agreement with some general hypotheses like the Feynman scaling law. First the role of phase space arguments is clarified and the importance of detecting correlations in high energy production experiments as an hint for understanding the underlying dynamics is emphasized. Then two peculiar (and, in a sense, complementary) kinds of correlation in two-particle inclusive distributions are examined: the one coming from multiperipheral dynamics with Lorentz pole exchanges, the other due to “direct channel” resonances. Some general properties of inclusive distributions are expressed in terms of quantities which are suitable for direct measurement.