arXiv subjects
Publications and source records attributed to K. Zalewski.
It is observed that the finite size of hadrons produced in high energy collisions implies that their positions are correlated, since the probability of finding two hadrons on top of each other is highly reduced. It is then shown that this effect can naturally explain the values of the correlation function below one, observed at LEP and LHC for pairs of identical pions.
It is pointed out that the size of the interaction region, as determined from HBT analyses, is increased due to the transition time necessary the convert the quarks and gluons into hadrons. A rough estimate yields an increase of R_HBT by about 15%.
Interpretation of long-range rapidity correlations in terms of the fluctuating rapidity density distribution of the system created in high-energy collisions is proposed. When applied to recent data of the STAR coll., it shows a substantial asymmetric component in the shape of this system in central Au-Au collisions, implying that boost invariance is violated on the event-by-event basis even at central rapidity. This effect may seriously influence the hydrodynamic expansion of the system.
It is shown that the recently proposed method of studying the long-range correlations in multiparticle production can be effectively used to verify the hydrodynamic nature of the longitudinal expansion of the partonic system created in the collision. The case of ALICE detector is explicitly considered.
A new method to study the long-range correlations in multiparticle production is developped. It is proposed to study the joint factorial moments or cumulants of multiplicity distributions in several (more than two) bins. It is shown that this step dramatically increases the discriminative power of data.
A model-independent method of studying the forward-backward correlations in symmetric high energy processes is developed. The method allows a systematic study of properties of various particle sources and to uncover asymmetric structures hidden in symmetric hadron-hadron and nucleus-nucleus inelastic reactions.
The HBT method is used to get information about the sizes, shapes and sometimes also about the time evolution of the homogeneity regions in hadroproduction processes. Homogeneity region K is the region where the hadrons with momentum K are produced. The size and shape of he homogeneity region is described by the Wigner function W(K,X) evaluated in the interaction picture after all the hadrons had been produced. Additional information about the interaction region is contained in the emission functio S(K,X). A theorem is presented and discussed which specifies which of the parameters characterizing the Wigner functin can and which cannot be obtained using the HBT method. In order to obtain the complete Wigner fuction additional assumptions are needed. For instance, it is enough to know the distribution of the centers of the homogeneity regions _K. In order to find the emission function further assumptions are required. No systematic analysis is available, but some instructive examples are discussed.
Let us denote p(x|K) the space density of the points where identical particles of some kind, e.g. pi+ mesons, with momentum K are produced. When using the HBT method to determine p(x|K) one encounters ambiguities. We show that these ambiguities do not affect the even cumulants of the distribution p(x|K). In particular, the HBT radii of the homogeneity regions, which are given by the second order cumulants, and the distribution of distances between the pairs of production points for particles with momentum K can be reliably measured. The odd cumulants are ambiguous. The are, however, correlated. In particular, when the average position (K) is known as a function of K there is no further ambiguity.
An approximate formula connecting the true and the HBT homogeneity regions in multiparticle production processes is derived. It implies that when calculating the HBT radii one should use the ceter of mass systems of the pairs rather than the now popular LCMS system. A discussion of several examples clarifies the potential and limitations of the HBT method. The even cumulants of the X-distribution, inculding the HBT radii, can be determined for each homogeneity region, but the relative positions of the homogeneity regions are unconstrained. This makes the HBT radii of little use for calculating quantities dependent on the interparticle interactions in coordinate space.
The effects of interpreting classical phase space distributions as Wigner functions, which is common in models of multiparticle production, are discussed. The temperature for the classical description is always higher than that for its Wigner function interpretation. A rough estimate shows that the corresponding correction is proportional to R^(-2), where R is the radius of the interaction region, and that it is negligible for heavy ion scattering, but at the few percent level for e^+e^- annihilations.
Recently suggested method of measuring Renyi entropies of multiparticle systems produced in high-energy collisions is presented in the form of a "do-list", explaining explicitely how to perform the measurement and suggesting improvements in the treatment of the data.
Determinations of the size and shape of the interaction region from k-particle (k=1,2,...) momentum distributions of identical particles are analyzed. The full group of transformations changing the single particle density matrix without affecting any of the measurable momentum distributions is identified. The corresponding uncertainties in the inferred parameters of the interaction region are discussed.
The evolution of the experimental knowledge and of the theoretical ideas about Bose-Einstein correlations in multiple particle production processes, during the first thirty years from their discovery, is reviewed.
A model-independent lower bound on the entropy S of the multiparticle system produced in high energy collisions, provided by the Renyi entropy H_2, is shown to be very effective. Estimates show that the ratio H_2/S remains close to one half for all realistic values of the parameters.
It is pointed out that the average semi-inclusive particle phase-space density at freeze-out can be determined from the coincidence probability of the events observed in multiparticle production. The method of measurement is described and its accuracy examined.
Recent improvements in the method of estimating Renyi entropies from measurements of coincidences between the events observed in high energy collisions are reviewed. A new, more precise, formulation of the method is presented and its accuracy analysed.
Relation between Renyi entropies and moments of the Wigner function, representing the quantum mechanical description of the M-particle semi-inclusive distribution at freeze-out, is investigated. It is shown that in the limit of infinite volume of the system, the classical and quantum descriptions are equivalent. Finite volume corrections are derived and shown to be small for systems encountered in relativistic heavy ion collisions.
Coincidence probabilities, which yield Renyi entropies, are investigated in a generalized Gaussian model, which includes interparticle correlations