Quantum correlations in two-particle Anderson localization

We predict quantum correlations between noninteracting particles evolving simultaneously in a disordered medium. While the particle density follows the single-particle dynamics and exhibits Anderson localization, the two-particle correlation develops unique features that depend on the quantum statistics of the particles and their initial separation. On short time scales, the localization of one particle becomes dependent on whether or not the other particle is localized. On long time scales, the localized particles show oscillatory correlations within the localization length. These effects can be observed in Anderson localization of nonclassical light and ultracold atoms.     

Hydrodynamics: Fluctuating initial conditions and two-particle correlations

Event-by-event hydrodynamics (or hydrodynamics with fluctuating initial conditions) has been developed in the past few years. Here we discuss how it may help to understand the various structures observed in two-particle correlations.     

Azimuthal dependence of two-particle transverse momentum current correlations

The European Physical Journal C - We present a study on inclusive emissions of a double $$\Lambda _c$$ or of a $$\Lambda _c$$ plus a light-flavored jet system as probe channels in the semi-hard...     

Inclusive two-particle rapidity correlations at ISR energies and fireball production

ISR data on two-particle rapidity correlations in the region y₁ ≈ y₂ can be understood in terms of the multiperipheral fireball model and indicate an energy independent upper limit of the average fireball mass. The diffractive contribution to the fireball production leads to characteristic shapes of long range correlations. Data on long range rapidity correlations may be used to determine the fractions of non-diffractive and diffractive one- and two-fireball production.     

Effect of Bose-Einstein statistics on two-particle azimuthal and rapidity correlations

The short-range effect in azimuthal and rapidity correlations can be explained within the independent cluster model taking into account the cluster transverse momentum and the Bose-effect (identical particle effect) in the single as well as the two-cluster term. Good agreement with data from Dubna, NAL and ISR is obtained. From the data we determine parameters related to the longitudinal and transverse dimensions of the clusters.     

Semiinclusive two-particle correlations and independent cluster emission at ISR energies

Semiinclusive two-particle correlations are calculated in the independent cluster emission model. The resulting semi-inclusive correlation functions ?₂ⁿ(y₁ = y₂ = 0) agree rather than well experimental data, esp. with respect to the multiplicity dependence. The average number of charged particles per cluster found from comparison with semiinclusive data is 2.5 charged particles per cluster, a value found earlier also from analysis of inclusive correlations.     

Charge dependent effects in azimuthal two-particle correlations and cluster production

It is shown that neutral heavy cluster models provide a natural explanation of the recently observed charged dependent effects in azimuthal correlations between produced pions. This may be interpreted as evidence for identical particle effect and π⁺π^? resonance production in clusters.     

The possibility of describing a two-particle quantum system and interparticle correlations in the self-consistent field approximation

The possibility of determining the energy spectrum and the wave function structure of the stationary states of a model two-particle system is examined in the self-consistent field approximation. The results of exact calculations are compared with the data obtained in the self-consistent field approximation with the use of orthogonal and nonorthogonal orbitals. The possibility of using these approximations for describing the interparticle quantum correlations is discussed.     

Diffusion and spatial correlations in suspensions of swimming particles

Populations of swimming micro-organisms produce fluid motions that lead to dramatically enhanced diffusion of tracer particles. Using simulations of suspensions of swimming particles in a periodic domain, we capture this effect and show that it depends qualitatively on the mode of swimming: swimmers "pushed" from behind by their flagella show greater enhancement than swimmers that are "pulled" from the front. The difference is manifested by an increase, that only occurs for pushers, of the diffusivity of passive tracers and the velocity correlation length with the size of the periodic domain. A physical argument supported by a mean field theory sheds light on the origin of these effects.     

The influence of final state interaction on two-particle correlations in multiple production of particles and resonances

The structure of pair correlations of interacting particle moving with nearby velocities is analysed. A general formalism of the two-particle space-time density matrix, taking into account the space-time coherence of the production process, is developed. The influence of strong final state interaction on two-particle correlations in the case of the production of a systemresonance+particle is investigated in detail. It is shown that in the limit of small distances between the resonance and particle production points the effect of final state interaction is enhanced due to logarithmic singularity of the triangle diagram. Numerical estimates indicate that, in this limit, the effect of strong final state interaction becomes important even for two-pion correlations.     

A comparison of two-particle rapidity correlations in antiproton-proton and proton-proton interactions at 31 GeV centre-of-mass energy

We investigated correlations between pairs of charged secondaries produced in antiproton-proton and proton-proton interactions at a centre-of-mass energy of 31 GeV using the pseudorapidity variable η=?ln (tanθ/2). Positive, short-range correlations were observed in both reactions. In the antiproton-proton case, however, there is a stronger correlation at very short range when both particles are produced in the central region and when the charged multiplicity of the event is about 30% higher than the mean. A simple Monte Carlo calculation indicates that quark-antiquark annihilation into two hadronic jets could account for the observed effect.     

One- and two-particle microrheology

We study the dynamics of rigid spheres embedded in viscoelastic media and address two questions of importance to microrheology. First, we calculate the complete response to an external force of a single bead in a homogeneous elastic network viscously coupled to an incompressible fluid. From this response function we find the frequency range where the standard assumptions of microrheology are valid. Second, we study fluctuations when embedded spheres perturb the media around them and show that mutual fluctuations of two separated spheres provide a more accurate determination of the complex shear modulus than do the fluctuations of a single sphere.     

Parton model predictions for two-particle correlations in e+e− annihilation

The parton model predicts a jet structure for e⁺e^? annihilation into hadrons. This is obscured at low energies by the presence of finite transverse momentum effects. We suggest studying e+⁺e^? → h₁+h₂+X, where at least one hadron is near the kinematical boundary; this defines a jet axis. Numerous predictions for correlations among mesons follow from Feynman's parton fragmentation suggestion. We also give sum rules which check for the quantum numbers of the partons.     

Gauge symmetry and supersymmetric two-particle problem

An analogy between the removal of nonphysical relative time (or relative energy) in the supersymmetric two-particle problem and the account of local gauge invariance in supersymmetric quantum field theory is discussed. A group of gauge transformations for the Bethe-Salpeter amplitudes is suggested, the invariants of which are the relativistic three-dimensional (quasipotential) wave functions in the Logunov-Tavkhelidze approach. Subsidiary conditions imposed on the Bethe-Salpeter amplitudes in the Todorov approach are shown to be equivalent to appropriate gauge fixing.     

Inclusive two-particle correlations in 40 GeV/c π−p collisions and particle production mechanisms

Inclusive two-particle correlations in rapidity variables between π⁺π^?, π⁺π⁺ and π^?π^? obtained in 40 GeV π^?p collisions are discussed in the framework of the Mueller Regge model and the multiperipheral cluster model. The data show features similar to the data reported at much higher energies from the CERN ISR. This behaviour is more easily understood from the multiperipheral cluster model. Data on transverse momentum correlations in the same reactions can be qualitatively understood from the same model.