Production of light nuclei at colliders – coalescence vs. thermal model

The production of light nuclei in relativistic heavy-ion collisions is well described by both the thermal model, where light nuclei are in equilibrium with hadrons of all species present in a fireball, and by the coalescence model, where light nuclei are formed due to final-state interactions after the fireball decays. We present and critically discuss the two models and further on we consider two proposals to falsify one of the models. The first proposal is to measure a yield of exotic nuclide 4Li and compare it to that of 4He. The ratio of yields of the nuclides is quite different in the thermal and coalescence models. The second proposal is to measure a hadron-deuteron correlation function which carries information whether a deuteron is emitted from a fireball together with all other hadrons, as assumed in the thermal model, or a deuteron is formed only after nucleons are emitted, as in the coalescence model. The p − 3He correlation function is of interest in context of both proposals: it is needed to obtain the yield of 4Li which decays into p and 3He, but the correlation function can also tell us about an origin of 3He.

Influence of final-state interaction on double spin asymmetries in incoherent π+-photoproduction on the deuteron near threshold

Incoherent [Formula: see text]-photoproduction on the deuteron is investigated for photon energies near threshold with particular focus on beam-target double spin asymmetries. The analysis is based on a [Formula: see text] reaction model in which realistic elementary amplitudes for [Formula: see text], [Formula: see text] and [Formula: see text] are incorporated. Numerical results on all possible beam-target double spin asymmetries of the differential and total cross-sections in the photon energy region near threshold are presented. Effects of [Formula: see text] and [Formula: see text] final-state interactions are investigated and their roles are found to be important.

Particle correlations from the initial state

The observation in small size collision systems, pp and pA, of strong correlations with long range in rapidity and a characteristic structure in azimuth, the ridge phenomenon, is one of the most interesting results obtained at the large hadron collider. Earlier observations of these correlations in heavy ion collisions at the relativistic heavy ion collider are standardly attributed to collective flow due to strong final state interactions, described in the framework of viscous relativistic hydrodynamics. Even though data for small size systems are well described in this framework, the applicability of hydrodynamics is less well grounded and initial state based mechanisms have been suggested to explain the ridge. In this review, we discuss particle correlations from the initial state point of view, with focus on the most recent theoretical developments.

Inelastic meson-meson scattering in hadronic matter

We review studies of inelastic meson-meson scattering. In nonperturbative schemes with chiral-perturbation-theory Lagrangians and in models based on effective meson Lagrangians, inelastic meson-meson scattering leads to the successful identification of resonances in meson-meson reactions, adequate inclusion of final state interactions in particle decays, and so on. For mesons of which each consists of a quark and an antiquark, inelastic meson-meson scattering may be caused by quark-antiquark annihilation, quark-antiquark creation, quark interchange, and quark-antiquark annihilation and creation. In transition amplitudes for meson-meson scattering mesonic quark-antiquark relative-motion wave functions depend on hadronic matter, and transition potentials are given in perturbative quantum chromodynamics. Via transition amplitudes the cross sections for inelastic meson-meson scattering depend on the temperature of hadronic matter. Some prominent temperature dependence of the cross sections has been found. Inelastic meson-meson scattering becomes even more significant in proton-proton collisions and lead-lead collisions at the Large Hadron Collider.

Unitarization Technics in Hadron Physics with Historical Remarks

We review a series of unitarization techniques that have been used during the last decades, many of them in connection with the advent and development of current algebra and later of Chiral Perturbation Theory. Several methods are discussed like the generalized effective-range expansion, K-matrix approach, Inverse Amplitude Method, Padé approximants and the N / D method. More details are given for the latter though. We also consider how to implement them in order to correct by final-state interactions. In connection with this some other methods are also introduced like the expansion of the inverse of the form factor, the Omnés solution, generalization to coupled channels and the Khuri-Treiman formalism, among others.

An accurate allowance for initial and final state interactions in the treatment of the alpha-alpha Bremsstrahlung

The alpha-alpha bremsstrahlung is studied using the generalization of the Siegert theorem. The corresponding amplitude is written in the gauge invariant form. Special attention is paid to taking into account the Coulomb interaction. Some correlation function is found and its dependence on the strong alpha-alpha interaction is discussed.

Study of the hyperon-nucleon interaction via final-state interactions in exclusive reactions

A novel approach that allows access to long-sought information on the Hyperon-Nucleon (YN) interaction was developed by producing a hyperon beam within a few-body nuclear system, and studying final-state interactions. The determination of polarisation observables, and specifically the beam spin asymmetry, in exclusive reactions allows a detailed study of the various final-state interactions and provides us with the tools needed to isolate kinematic regimes where the YN interaction dominates. High-statistics data collected using the CLAS detector housed in Hall-B of the Thomas Jefferson laboratory allows us to obtain a large set of polarisation observables and place stringent constraints on the underlying dynamics of the YN interaction.