Correlation Femtoscopy Research Articles

Pion femtoscopy in p+Au and Au+Au collisions at using transport approach

Correlation femtoscopy provides information about the space-time structure and evolution of the fireball created in ultra-relativistic nucleus-nucleus collisions. The dependence of the femtoscopic radii on transverse pair momentum and charged particle multiplicity of an event reflects the mechanism of collective behavior. In this work, the femtoscopic radii of identical charged pions were calculated in the UrQMD model for Au+Au and p+Au collisions at and compared to each other at the same multiplicities. The physics implications of this comparison will be discussed.

Femtoscopy with Identified Charged Particles for the NICA Energy Range

The correlation femtoscopy allows one to measure the space-time characteristics of particle production processes due to the effects of quantum statistics (QS) and final state interactions (FSI). Femtoscopy at lower energies was intensively studied at AGS, SPS and in the Beam Energy Scan (BES) program at RHIC. In the work we discuss possibilities to observe a difference from the first-order phase transition expected, according some theoretical predictions, at low energies and the crossover one, to be occurred at high energies, with the femtoscopy observables using the hybrid model vHLLE + UrQMD. The possibilities to use kaon femtoscopy complementary to the usually used pion one are discussed.

Correlation Femtoscopy: Origins and Achievements

A short introduction to correlation femtoscopy is given on the occasion of the 100th Anniversary of the birthday of Mikhail Isaakovich Podgoretsky.

Averaging and the Shape of the Correlation Function

A brief pedagogical introduction to correlation femtoscopy is given. We then focus on the shape of the correlation function and discuss the possible reasons for its departure from the Gaussian form and better reproduction with a Lévy stable distribution. With the help of Monte Carlo simulations based on asymmetric extension of the Blast-Wave model with resonances we demonstrate possible influence of averaging over many events and integrating over wide momentum bins on the shape of the correlation function. We also show that the shape is strongly influenced by the use of the one-dimensional parametrisation in the q i n v variable.

Correlation femtoscopy at NICA energies

The space-time characteristics of particle production are measured by the correlation femtoscopy with use of quantum statistics (QS) and final state interactions (FSI) effects. Femtoscopy at lower energy was a key of importance at AGS, SPS and in the Beam Energy Scan (BES) physics program at RHIC. Using femtoscopy observables we investigate possibilities to observe a difference from the first-order phase transition expected, according to some theoretical predictions, at low energies and the cross over one, to be occurred at high energies. The hybrid model vHLLE+UrQM is used as a baseline for this study. The possibilities to use kaon femtoscopy complementary to the usually used pion one are discussed.

Recent STAR Results from Heavy-Ion and Polarized Proton Programs

We present recent physics results from the STAR experiment at Relativistic Heavy Ion Collider (RHIC). The proceedings cover studies of azimuthal anisotropy in small and large systems, global and local hyperon polarization, correlation femtoscopy, antideuteron and J/ψ production from heavyion program as well as the measurements of longitudinal spin asymmetry from polarized proton program.

Correlation femtoscopy study at energies available at the JINR Nuclotron-based Ion Collider fAcility and the BNL Relativistic Heavy Ion Collider within a viscous hydrodynamic plus cascade model

Correlation femtoscopy allows one to measure the space-time characteristics of particle production in relativistic heavy-ion collisions due to the effects of quantum statistics (QS) and final state interactions (FSI). The main features of the femtoscopy measurements at top RHIC and LHC energies are considered as a manifestation of strong collective flow and are well interpreted within hydrodynamic models employing equation of state (EoS) with a crossover type transition between Quark-Gluon Plasma (QGP) and hadron gas phases. The femtoscopy at lower energies was intensively studied at AGS and SPS accelerators and is being studied now in the Beam Energy Scan program (BES) at the BNL Relativistic Heavy Ion Collider in the context of exploration of the QCD phase diagram. In this article we present femtoscopic observables calculated for Au-Au collisions at $\sqrt{s_{NN}} = 7.7 - 62.4$ GeV in a viscous hydro + cascade model vHLLE+UrQMD and their dependence on the EoS of thermalized matter.

Quantum canonical ensemble and correlation femtoscopy at fixed multiplicities

Identical particle correlations at fixed multiplicity are considered by means of quantum canonical ensemble of finite systems. We calculate one-particle momentum spectra and two-particle Bose-Einstein correlation functions in the ideal gas by using a recurrence relation for the partition function. Within such a model we investigate the validity of the thermal Wick's theorem and its applicability for decomposition of the two-particle distribution function. The dependence of the Bose-Einstein correlation parameters on the average momentum of the particle pair is also investigated. Specifically, we present the analytical formulas that allow one to estimate the effect of suppressing the correlation functions in a finite canonical system. The results can be used for the femtoscopy analysis of the A+A and p+p collisions with selected (fixed) multiplicity.

Recent results of the femtoscopic measurements from RHIC and LHC

The two-particle correlations at low relative momenta (correlation femtoscopy) are sensitive to quantum statistics and allow to measure the space-time picture of the system evolution created in lieavy-ion (HI) and particle collisions. The spatio-temporal parameters extracted from HI collisions describe the system at the last moment of the collision evolution - kinetic freeze-out. and provide the essential information about the formation of the quark-gluon plasma. The measurements at many facilities showed the dependencies of the spacial scales from the event multiplicity and particle transverse mass,mT. In this paper we show recent results obtained at RHIC and LHC energies and compare them to the theoretical expectations.

Correlation femtoscopy of Kaons in the SELEX experiment

Preliminary results from the correlation femtoscopy of identical kaons in the SELEX experiment (Fermilab E781) are presented. Kaons are selected in inclusive reactions of Σ−C(Cu) interactions at an initial energy of 610 GeV. Kaon pairs are studied in all possible charged states: Ks0Ks0, Ks0K+, Ks0K−, K+K+, K+K− and K−K−. The source sizes of the hadronization region of neutral and charged kaon pairs are measured.

Correlation femtoscopy of small systems

The basic principles of the correlation femtoscopy, including its correspondence to the Hanbury Brown and Twiss intensity interferometry, are reexamined. The main subject of the paper is an analysis of the correlation femtoscopy when the source size is as small as the order of the uncertainty limit. It is about 1 fm for the current high energy experiments. Then the standard femtoscopy model of random sources is inapplicable. The uncertainty principle leads to the partial indistinguishability and coherence of closely located emitters that affect the observed femtoscopy scales. In thermal systems the role of corresponding coherent length is taken by the thermal de Broglie wavelength that also defines the size of a single emitter. The formalism of partially coherent phases in the amplitudes of closely located individual emitters is used for the quantitative analysis. The general approach is illustrated analytically for the case of the Gaussian approximation for emitting sources. A reduction of the interferometry radii and a suppression of the Bose-Einstein correlation functions for small sources due to the uncertainty principle are found. There is a positive correlation between the source size and the intercept of the correlation function. The peculiarities of the nonfemtoscopic correlations caused by minijets and fluctuations of the initial states of the systems formed in $pp$ and ${e}^{+}{e}^{\ensuremath{-}}$ collisions are also analyzed. The factorization property for the contributions of femtoscopic and nonfemtoscopic correlations into complete correlation function is observed in numerical calculations in a wide range of the model parameters.

Femtoscopic Correlations and Narrow Resonance Formation

Motivated by recent data on the effect of resonances on particle correlations in ultrarelativistic heavy ion collisions we present a correlation femtoscopy–based approach to narrow resonance formation via final state interaction. Since in this case relative momenta of the particles forming the pair are not negligible when compared to the widths of single particle spectra we have to generalize the usual form of the smoothness approximation. To illustrate this technique we calculate π + Ξ − and K + K − correlation function including Ξ ∗ (1530) and φ(1020) formation, respectively. We also analyze sensitivity of the final state resonance formation to the flow-induced position-momentum correlations.

Correlations of antiprotons with small relative momentumin the SELEX Experiment

The main results of the data processing and physical analysis of the SELEX experiment and the preliminary data on correlations of antiprotons with small relative momentum are presented. Correlation femtoscopy is a powerful tool for studying the spatial-temporal characteristics of the emission region of identical particles. The correlation functions obtained in the SELEX and STAR experiments are compared.

Notes on correlation femtoscopy

The particle correlations at small relative velocities are sensitive to the space—time characteristics of the production processes on a femtometer scale owing to the effects of quantum statistics and finalstate interaction. Though the final—state interaction complicates the correlation analysis, it is an important source of information allowing for coalescence femtoscopy, correlation femtoscopy with unlike particles including access to the relative space—time asymmetries in particle production, and a study of strong interactions between specific particles. I will briefly discuss the history and basics of correlation femtoscopy, some of the recent results from femtoscopy of relativistic heavy-ion collisions, and their consequences.

TWO-PARTICLE CORRELATION IN HEAVY-ION COLLISIONS AT CSR ENERGY

The predictions of the two-particle correlation by using the relativistic quantum molecular dynamics model are presented for the heavy-ion reactions at HIRFL-CSR energy. The two-proton correlation function with the final state interaction is calculated with the Lednicky code for the U + U collisions at beam energy 520 A MeV. Applying the imaging technique, the relationship between the freeze-out spatial distributions and the results of correlation femtoscopy is investigated. We find that one can reliably reconstruct the source functions from the two-particle correlation functions with ignoring the degree of space-momentum correlations at this energy. The results are useful to the designing the hadron detector at CSR.

Correlation femtoscopy

The basics of correlation femtoscopy, recent results from femtoscopy in relativistic heavy ion collisions and their consequences are shortly reviewed.

Correlation femtoscopy in neutron-carbon interactions at average neutron energy of 51 GeV

Correlations of pairs of Λ hyperons, neutral kaons, and charged pions having a low relative momentum are analyzed on the basis of data obtained at the EXCHARM facility in neutron-carbon interactions at an average neutron energy of 51 GeV. Preliminary results of this analysis are presented.

Erratum: “Correlation femtoscopy of multiparticle processes” [Physics of Atomic Nuclei 67, 72–82 (2004)

Erratum: “Correlation femtoscopy of multiparticle processes” [Physics of Atomic Nuclei 67, 72–82 (2004)

Correlation femtoscopy of multiparticle processes

Recent results on particle momentum and spin correlations are discussed in view of the role played by the effects of quantum statistics, including multiboson and coherence phenomena, and final state interaction. Particularly, it is demonstrated that the latter allows for (i) correlation femtoscopy with unlike particles; (ii) study of the relative space--time asymmetries in the production of different particle species (e.g., relative time delays or spatial shifts due to collective flows); (iii) study of the particle strong interaction hardly accessible by other means (e.g., in two-lambda system).