In this paper, the first femtoscopic analysis of pion-kaon correlations at the LHC is reported. The analysis was performed on the Pb-Pb collision data at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV recorded with the ALICE detector. The non-identical particle correlations probe the spatio-temporal separation between sources of different particle species as well as the average source size of the emitting system. The sizes of the pion and kaon sources increase with centrality, and pions are emitted closer to the centre of the system and/or later than kaons. This is naturally expected in a system with strong radial flow and is qualitatively reproduced by hydrodynamic models. ALICE data on pion-kaon emission asymmetry are consistent with (3+1)-dimensional viscous hydrodynamics coupled to a statistical hadronization model, resonance propagation, and decay code THERMINATOR 2 calculation, with an additional time delay between 1 and 2 fm$/c$ for kaons. The delay can be interpreted as evidence for a significant hadronic rescattering phase in heavy-ion collisions at the LHC.
We report on the results of femtoscopic analyses of Pb-Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV and pp collisions at $\sqrt{s}$= 7 TeV with identical charged and neutral kaons. The femtoscopic correlations allow one to measure the space-time characteristics of particle production using particle correlations due to the effects of quantum statistics for identical particles and final state interaction for both identical and non-identical ones. Small contributions from resonance decays make kaon femtoscopy an ideal tool for the correlation studies. In conjunction with pion and proton femtoscopy, …
We present the results of three-dimensional femtoscopic analyses for charged and neutral kaons recorded by ALICE in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Femtoscopy is used to measure the space-time characteristics of particle production from the effects of quantum statistics and final-state interactions in two-particle correlations. Kaon femtoscopy is an important supplement to that of pions because it allows one to distinguish between different model scenarios working equally well for pions. In particular, we compare the measured 3D kaon radii with a purely hydrodynamical calc…
Femtoscopic correlations between charged pions and kaons for different charge combinations are measured in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV with ALICE at the LHC. The three-dimensional pion-kaon ($π-{\rm K}$) correlation functions and double ratios in the out-side-long pair rest frame are studied in different centrality bins. The $π-{\rm K}$ femtoscopic source size parameter ($R_{\rm out}$) and emission asymmetry ($μ_{\rm out}$) are extracted. It is observed that the average source size of the system and the emission asymmetry between pions and kaons increase from peripheral …
We provide, within the hydrokinetic model, a detailed investigation of kaon interferometry in $Pb+Pb$ collisions at LHC energy ($\sqrt{s_{NN}} = 2.76$ TeV). Predictions are presented for 1D interferometry radii of $K^0_SK^0_S$ and $K^{\pm}K^{\pm}$ pairs as well as for 3D femtoscopy scales in out, side and long directions. The results are compared with existing pion interferometry radii. We also make predictions for full LHC energy.
Non-identical particle femtoscopy measures the size of the system emitting particles ("radius") in heavy-ion collisions as well as the difference between mean emission space-time coordinates of two particle species ("emission asymmetry"). The system created in such collisions at the LHC behaves collectively and its dynamics is well described by hydrodynamic models. A significant emission asymmetry between pions and kaons, coming from collective flow, enhanced by contribution from flowing resonances is predicted. We present calculations within the (3+1)D viscous hydrodynamic model coupled to st…
The study of the strength and behaviour of the antikaon-nucleon ($\mathrm{\overline{K}N}$) interaction constitutes one of the key focuses of the strangeness sector in low-energy Quantum Chromodynamics (QCD). In this letter a unique high-precision measurement of the strong interaction between kaons and protons, close and above the kinematic threshold, is presented. The femtoscopic measurements of the correlation function at low pair-frame relative momentum of (K$^+$ p $\oplus$ K$^-$ $\overline{\mathrm{p}}$) and (K$^-$ p $\oplus$ K$^+$ $\overline{\mathrm{p}}$) pairs measured in pp collisions at …
The size of the particle emission region in high-energy collisions can be deduced using the femtoscopic correlations of particle pairs at low relative momentum. Such correlations arise due to quantum statistics and Coulomb and strong final state interactions. In this paper, results are presented from femtoscopic analyses of $π^{\pm}π^{\pm}$, ${\rm K}^{\pm}{\rm K}^{\pm}$, ${\rm K}^{0}_S{\rm K}^{0}_S$, ${\rm pp}$, and ${\rm \overline{p}}{\rm \overline{p}}$ correlations from Pb-Pb collisions at $\sqrt{s_{\mathrm {NN}}}=2.76$ TeV by the ALICE experiment at the LHC. One-dimensional radii of the sys…
Three-dimensional analyses of the pion source revealed a heavy, non-Gaussian tail in the direction of the pair transverse momentum. The interpretation of these pion sources in terms of pure hydrodynamical evolution is, however, complicated by the strong contribution of feed-down from long-lived resonances to the source. On the other hand, kaons provide a much cleaner probe of the expanding fireball. Here we present a recent three-dimensional kaon correlation analysis using Cartesian harmonics decomposition technique. In contrary to pions, the three-dimensional source function of kaons is large…
Femtoscopy is providing information on system size and its dynamics in heavy-ion collisions. At ultra-relativistic energies, such as those obtained at the LHC, significant production of pions, kaons and protons enables femtoscopic measurements for these particles. In particular the dependence of system size on pair momentum and particle type is interpreted as evidence for strong collective flow. Such phenomena are naturally modeled by hydrodynamics. We present calculations within the 3+1D hydrodynamic model coupled to statistical hadronization code THERMINATOR 2, corresponding to Pb--Pb collis…
In quantum scattering processes between two particles, aspects characterizing the strong and Coulomb forces can be observed in kinematic distributions of the particle pairs. The sensitivity to the interaction potential reaches a maximum at low relative momentum and vanishing distance between the two particles. Ultrarelativistic heavy-ion collisions at the LHC provide an abundant source of many hadron species and can be employed as a measurement method of scattering parameters that is complementary to scattering experiments. This study confirms that momentum correlations of particles produced i…
In these proceedings, we present the measurements of proton, light nuclei, and strange particle with neutral kaons correlation functions in Au+Au collisions at the BES program and top RHIC energy. The experimental results will be compared with model calculations to extract the size of emitting source and the properties of final state interactions. The collision energy and centrality dependence of the source size will be studied. Further, the implications for the production mechanism of light nuclei will be discussed.
We present femtoscopic results for proton and Lambda correlation functions measured by ALICE in sqrt(sNN) = 2.76 TeV Pb-Pb collisions. Femtoscopic radii are extracted from pp, pbarpbar, and ppbar pairs. Comparisons of these radii with those from pion and kaon analyses reveal an approximate transverse mass scaling that is consistent with explanations of radial flow. Inelastic final state interactions are explored in baryon-antibaryon correlations functions to investigate their relationship with reduced proton yields at LHC energies.
We report on the results of femtoscopic analysis of Pb-Pb collisions at sqrt(s_NN)=2.76 TeV and pp collisions at sqrt(s)=0.9, 2.76 and 7 TeV with identical pions and kaons. Detailed femtoscopy studies in heavy-ion collisions at SPS and RHIC have shown that emission region sizes ("HBT radii") decrease with increasing pair transverse momentum k_T, which is understood as a manifestation of the collective behavior of matter. The trend was predicted to persist at the LHC. The data from Pb-Pb collisions confirm the existence of a flowing medium and provide strict constraints on the dynamical models.…
We present results of femtoscopic analysis with K0s-K0s, Kch-Kch, p-p, pbar-pbar, p-pbar and lambda-antilambda in Pb-Pb collisions at sqrt{s_NN}=2.76 TeV and K0s-K0s in pp collisions at sqrt{s}=7 TeV registered by ALICE at the LHC. The femtoscopic radius is extracted from the one-dimensional correlation functions. The analysis reveals that the emission source sizes of pions, kaons and protons measured in heavy-ion collisions exhibit approximate transverse mass scaling which is consistent with hydrodynamic collectivity prediction. Furthermore, baryon-antibaryon correlations are investigated to …
We present new measurements of $Λ-Λ$ correlations, which are closely related to $H$-dibaryon: a six quark state predicted by Jaffe (1977), in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV from the STAR experiment. Fits to different potential models are discussed and extracted scattering length and effective range are also presented.We also present spherical harmonic decomposition of pion-kaon correlation function for 0-5% centrality in Au+Au collision at $\sqrt{s_{NN}} = 200$ GeV. In addition, we also discuss results from azimuthal HBT for beam energies 7.7-200 GeV.
The $m_T$-dependencies of the femto-scales, the so-called interferometry and source radii, are investigated within the hydrokinetic model for different types of particle pairs - pion-pion, kaon-kaon, proton-proton and proton-lambda, - produced in Pb+Pb and $p+p$ collisions at the LHC. In particular, such property of the femto-scales momentum behavior as $m_T$-scaling is studied for the systems with (w) and without (w/o) intensive transverse flow, and also w and w/o re-scattering at the final afterburner stage of the matter evolution. The detail spatiotemporal description obtained within hydrok…
Short range correlations of identified charged hadrons in pp (sqrt(s) = 0.9, 2.76, and 7 TeV), pPb (sqrt(sNN) = 5.02 TeV), and peripheral PbPb collisions (sqrt(sNN) = 2.76 TeV) are studied with the CMS detector at the LHC. Charged pions, kaons, and protons at low pT and in laboratory pseudorapidity |eta| < 1 are identified via their energy loss in the silicon tracker. The two-particle correlation functions show effects of quantum statistics, Coulomb interaction, and also indicate the role of multi-body resonance decays and mini-jets. The characteristics of the one-, two-, and three-dimensional…
Short range correlations of identified charged hadrons in pp ($\sqrt{s} =$ 0.9, 2.76, and 7 TeV), pPb ($\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV), and peripheral PbPb collisions ($\sqrt{s_{_\mathrm{NN}}} =$ 2.76 TeV) are studied with the CMS detector at the LHC. Charged pions, kaons, and protons at low momentum and in laboratory pseudorapidity $|η| < 1$ are identified via their energy loss in the silicon tracker. The two-particle correlation functions show effects of quantum statistics, Coulomb interaction, and also indicate the role of multi-body resonance decays and mini-jets. The characteristics…
The correlation function of two identical particles - pions or kaons - interacting via Coulomb potential is computed. The particles are emitted from an anisotropic particle's source of finite lifetime. In the case of pions, the effect of halo is taken into account as an additional particle's source of large spatial extension. The relativistic effects are discussed in detail. The Bowler-Sinyukov procedure to remove the Coulomb interaction is carefully tested. In the absence of halo the procedure is shown to work very well even for an extremely anisotropic source. When the halo is taken into acc…
The NA60 experiment at the CERN SPS studied phi meson production in In-In collisions at 158 A GeV via muon and kaon decay channels. Results in the hadronic channel are presented for the first time. These are discussed in the framework of the so-called phi puzzle through the comparison with the previous NA60 measurements in the muon channel. The yield and inverse m_T slopes observed in the two channels are compatible within errors, showing that the large discrepancies seen in Pb-Pb collisions between NA50 (muon pairs) and NA49 (kaon pairs) are not seen in the NA60 In-In data.
Identical neutral kaon pair correlations are measured in 7 TeV pp collisions in the ALICE experiment. K0s-K0s correlation functions are formed in 3 multiplicity X 4 kT bins. The femtoscopic kaon source parameters Rinv and lambda are extracted from these correlation functions by fitting a (femtoscopy) X (PYTHIA) model to them, PYTHIA accounting for the non-flat baseline found in pp collisions. Source parameters are obtained from a fit which includes quantum statistics and final-state interactions of the a0/f0 resonance. K0s-K0s correlations show a systematic increase in Rinv for increasing mult…
Particle correlations at small relative momenta can be used to measure the space$-$time characteristics of particle production on the femtoscopic (fm=10$^{-15}$ m) level in high-energy collisions. Such correlations arise due to quantum statistics and final state interactions. We report correlations of two charged identical kaons measured in p$-$Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV by the ALICE experiment at the LHC. The femtoscopic invariant radii and correlation strengths are extracted from the one-dimensional kaon correlation functions and are compared to those obtained in pp and Pb…
Ultra-relativistic gold-gold and proton-proton collisions are investigated in the experiments of the Relativistic Heavy Ion Collider (RHIC). In the last several years large amount of results were revealed about the matter created in these collisions. The latest PHENIX results for femtoscopy and correlations are reviewed in this paper. Bose-Einstein correlations of charged kaons in 200 GeV Au+Au collisions and of charged pions in 200 GeV p+p collisions are shown. They are both compatible with previous measurements of charged pions in gold-gold collisions, with respect to transverse mass or numb…
The results on the main bulk observables obtained in the simulations within the integrated hydrokinetic model (iHKM) of Au+Au collisions at the RHIC energy $\sqrt{s_{NN}}=200$ GeV are presented along with the corresponding experimental data from the STAR and the PHENIX collaborations. The simulations include all the stages of the collision process: formation of the initial state, its gradual thermalization and hydrodynamization, viscous relativistic hydro-evolution, system's hadronization and particlization, and, finally, an expansion of the interacting hadron-resonance gas. The model gives a …
Observation of the centrality-dependent difference in directed flow between charged kaons and $K^{*0}$ resonances in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 14.6, 19.6 and 27 GeV
We present measurements of three-dimensional correlation functions of like-sign low transverse momentum kaon pairs from sqrt(sNN)=200 GeV Au+Au collisions. A Cartesian surface-spherical harmonic decomposition technique was used to extract the kaon source function. The latter was found to have a three-dimensional Gaussian shape and can be adequately reproduced by Therminator event generator simulations with resonance contributions taken into account. Compared to the pion one, the kaon source function is generally narrower and does not have the long tail along the pair transverse momentum direct…
We describe expressions for pion and kaon dressed-quark distribution functions that incorporate contributions from gluons which bind quarks into these mesons and hence overcome a flaw of the commonly used handbag approximation. The distributions therewith obtained are purely valence in character, ensuring that dressed-quarks carry all a meson's momentum at a characteristic hadronic scale and vanishing as $(1-x)^2$ when Bjorken-$x\to 1$. Comparing such distributions within the pion and kaon, it is apparent that the size of SU(3)-flavour symmetry breaking in meson parton distribution functions i…
Hadronic interactions are crucial for the dynamical description of heavy-ion reactions at low collision energies and in the late dilute stages at high collision energies. In particular, the properties and decay channels of resonances are an essential ingredient of hadronic transport approaches. The HADES collaboration measured particle production in collisions of pions with carbon and tungsten nuclei at $E_\text{kin} = 1.7\,\text{GeV}$. Such reactions are of high interest, because they allow to probe the properties of baryonic resonances produced in a much cleaner environment than the usual nu…
Using the Ultra-relativistic Quantum Molecular Dynamics ({\tt UrQMD}) model, we investigate the azimuthal correlations in p--Pb collisions at $\sqrt{s_{_{\rm NN}}}=5.02$ TeV. It is shown that the simulated hadronic p--Pb system can not generate the collective flow signatures, but mainly behaves as a non-flow dominant system. However, the characteristic $v_{2}(p_{\rm T})$ mass-ordering of pions, kaons and protons is observed in {\tt UrQMD} simulations, which is the consequence of hadronic interactions and not necessarily associated with strong fluid-like expansions.
We calculate the cumulants and correlation functions of net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}} = 7.7$ GeV using a multiphase transport model (AMPT) with both a new coalescence mechanism and all charge conservation laws. The AMPT model can qualitatively describe the centrality dependences of the net-kaon cumulants and cumulant ratios measured by the STAR experiment. By focusing on the stage evolution of the cumulants, cumulant ratios, and correlation functions, we reveal several key effects on the fluctuations and correlations of strangeness during the dynamic…
