Femtoscopy is traditionally used to determine the size of the particle
emitting region in heavy-ion collisions. The non-identical particle
femtoscopy is additionally able to measure the difference in average
emission points (so-called emission asymmetry) between two types of
particles. This asymmetry is sensitive to details of the dynamics of
the system created in the collision, and...
The ϕ meson is a resonance particle and the lightest particle with hidden strangeness, containing both s and s̅ quarks. Strangeness enhancement is considered to be related to Quark-Gluon Plasma formation, making the ϕ meson a valuable probe due to its "double strangeness" in a partonic and zero net strangeness in a hadronic medium. Previous studies, such as EPJC 80 (2020) 199, demonstrated...
A study of the Bose–Einstein correlations for same-sign charged pions originating from proton-proton and proton-lead collisions recorded in the LHCb experiment at √s = 7 TeV centre-of-mass energy and √sNN = 5.02 TeV centre-of-mass energy per nucleon will be presented. Both measurements are the first of this type performed in the forward region at LHC energies and are complementary to studies...
Femtoscopy is a technique that connects measured particle correlation functions to the properties of hadron emission and final-state interaction. Recent advancements in modelling the emission source function in pp collisions have revealed a common hadron source for primordial particles. This discovery has been instrumental in achieving a better understanding of the source function, leading to...
One of the main goals of today's heavy-ion physics research is to explore the phase diagram of strongly interacting matter and search for signs of the possible critical endpoint on the QCD phase diagram. Femtoscopy is among the important tools used for this endeavor; there have been indications that combinations of femtoscopic radii parameters (referred to as HBT radii for identical boson...
We investigate the appearance of dynamical attractors in 3+1D systems by means of a Relativistic Full Boltzmann Transport approach. We look at the distribution function and its momentum moments and at the anisotropic flows $v_n$ and at how they lose memory about their initial conditions. Our analysis is performed in a wide range of system size and interaction strength, starting from typical...
The focus of this work is the tilt of the pion emission source in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7 to 27 GeV, based on data from the STAR experiment. The tilt is known to originate from the 3D structure of the initial collision geometry, such as the geometric overlap of two nuclei, and is important for understanding phenomena such as directed flow and polarization.
Using...
The study of femtoscopic correlations between photon pairs, although challenging from an experimental standpoint, can serve as a complemen- tary approach to traditional hadron femtoscopy. Owing to the penetrative nature of photons, which are unaffected by strong or electromagnetic in- teractions, such measurements can be used to probe the early stages of heavy-ion collisions, prior to...
The PHENIX experiment measured the centrality dependence of two-pion Bose-Einstein correlation functions in $\sqrt{s_{NN}}=200$ GeV Au
+
+Au collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The data are well represented by Lévy-stable source distributions. The extracted source parameters are the correlation-strength parameter $\lambda$
, the Lévy index of...
We present the first studies of charge-balance functions using the broad rapidity coverage of the CMS experiment. This larger phase space region is essential for studying the system time evolution. The width of the balance function, both in relative $|\eta|$ and relative azimuthal angle, is found to decrease with multiplicity for low particle transverse momentum ($p_{T} < 2$ GeV/c). The...
Balance functions have been used extensively to elucidate the time evolution of quark production in heavy-ion collisions. Early models predicted two stages of quark production, one for light quarks and one for the heavier strange quark, separated by a period of isentropic expansion. This led to the notion of clocking particle production and tracking radial flow effects, which drive the...
Two particle correlations have shown the presence of long-range rapidity correlations in small collision systems. Several other measurements provided insight into the unexpected collective beahviour similar to the one exhibited in heavy-ion collisions. These properties can be explained by several models, which consider a microscopic description like PYTHIA 8 and a macroscopic treatment as...
This talk presents recent correlation measurements involving Λ, Ξ, kaons and pions created in nucleus-nucleus collisions. Such measurements have been made available in the past few years, constituting new experimental constraints on the S = −1, −2 meson-baryon interactions and the nature of exotic states. The strong interactions involving mesons and baryons with strangeness content deliver a...
Particle correlations have traditionally been used to study collective phenomena in hadronic and heavy ion collisions through azimuthal distributions. In contrast, femtoscopic correlations offer valuable insights into quantum statistical effects and final-state interactions. This talk presents the first results from the CMS experiment on femtoscopic correlations of strange particles...
The MEG-II experiment, at the Paul Scherrer Institute in Switzerland, is searching for the charged lepton flavour violating (CLFV) μ+ → e+γ decay. After its second year of data taking only, it can reach the world’s best sensitivity on the branching ratio of the decay, below 10^(−13). Beyond its primary objective, MEG-II’s adaptability enables it to probe the recent Atomki anomalies. These...
Three significant anomalies have been observed in the emission of electron- positron pairs in the 7Li(p,e+e−)8Be, 3H(p,e+e−)4He and 11B(p,e+e−)12C nuclear reactions [1-3]. These anomalies have been interpreted as the signature of the existence of a boson (hereafter referred to as X17) of mass MX17 = 16.8 MeV/c2 that could be a mediator of a fifth force, characterised by a strong coupling...
Since the Rose model was published in 1949 [1,2], several laboratories worldwide have started experimental campaigns to measure the angular distribution of the Internal Pair Creation (IPC) process in light nuclei to study electromagnetic multipole transitions. In the 1950s, Devons et al. reported the experiments' results in $^{16}$O, $^{8}$Be, and $^8$Be [3,4]. The angular correlations...
The High-Acceptance Di-Electron Spectrometer (HADES) operates at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt with pion, proton and heavy-ion beams provided by the synchrotron SIS-18 [1]. In February 2022, the HADES Collaboration measured proton-proton collisions at 4.5 GeV momenta using the upgraded setup within the FAIR-Phase0 programme. One of the goals of the physics...
Femtoscopic correlations of light nuclei, such as proton-deuteron or deuteron-deuteron, are sensitive to a production mechanism of the nuclei. Therefore, one can distinguish whether nuclei are directly emitted from a fireball, as one assumes within the thermodynamic approach, or whether nuclei are formed later on due to final-state interactions, as the coalescence model assumes. The...
Strong interactions between particles are fundamental to understanding the properties of matter. One way to study these interactions is through femtoscopic correlation measurements of particle pairs, extracting information using available theoretical models. In this work, we examine two approaches for describing proton-deuteron (p-d) correlations: the Lednicky-Luboshyts formalism and full...
Alpha clustering is a crucial concept to understand nuclear
structures. Alpha particles, which are tightly bound with no excited
states up to Ex ~ 20 MeV, often behave as well established subunits
in nuclei, forming what are known as alpha cluster states.
Of particular interest are alpha condensed states where all alpha
clusters are condensed into the lowest s orbit. Due to this...
Wheeler and Wong predicted the possibility of toroidally-deformed nuclear configurations in the 1960s and 1970s. In the last decade, renewed interest has spurred further calculations exploring the possible structure, energetics, and disassembly of these nuclear configurations. Analysis of experimental data obtained with NIMROD at Texas A&M University showed hints that such structures may exist...
In recent years, experimental efforts have been dedicated to exploring the extent of clustering in excited nuclei. Of these, a particular emphasis in $\alpha$-clustering has been fostered due to its various influences, such as those in astrophysical processes. A series of measurements of every $\alpha$-conjugate nucleus in the mass range $16 \leq A \leq 36$ impinged on ${}^{12}\mathrm{C}$ at...
Nuclear structure evolves dramatically in asymmetric systems, particularly near the drip lines. A notable example is the “Island of Inversion”, where the magic neutron number N=20 breaks down, as established for proton number Z=10-13. We study the structure of the most neutron-rich Fluorine (Z=9) isotopes around N=20 using the SAMURAI spectrometer at RIBF/RIKEN. Measurements were performed in...
The process of Lévy walk, i.e., movement patterns described by heavy-tailed random walks, play a role in many different phenomena, from chemical and microbiological systems through marine predators to climate change. Recent experiments have suggested that this phenomenon also appears in heavy-ion collisions. However, the theoretical background is not yet well understood. In high-energy...
Femtoscopic measurements explore the strongly interacting Quark-Gluon-Plasma
(sQGP) via examining the space-time characteristics of heavy-ion collisions using cor-
relation functions of observed particles. This talk reports on an investigation of the
space-time geometry of heavy-ion collisions based on the EPOS model, a state-of-the-
art event generator. Based on its success with reliably...
In this work, we present new results on the three-dimensional pion-pion femtoscopic correlation measurements and their Lévy parameters in heavy-ion collisions, utilizing data from the STAR experiment at RHIC in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. These measurements aim to deepen our understanding on the space-time structure of hadron emission sources and their role in the behavior...
The VERITAS array consists of four Air Imaging Cherenkov Telescopes, measuring showers generated by extremely high-energy cosmic rays. During full-moon intervals, VERITAS is used for Stellar Intensity Interferometry (SII). This technique, pioneered by Hanbury Brown in the 1950s, probes the spatial distribution of intensity at the sub-milliarcsecond scale. Quite recently, groups around the...
Stellar Intensity Interferometry (SII) is a second observing mode of Imaging Atmospheric Cherenkov telescopes (IACTs), where the large collecting area and ultra-fast data acquisition electronics of these instruments can be used to reconstruct images of stars at optical blue wavelengths. IACTs composed of several telescopes distributed over an area of hundreds of meters, such as the ASTRI...
Accretion flows around black-holes, neutron stars or white dwarfs are studied since almost 60 years. Although they are ubiquitous and somewhat similar over scales reaching billions in mass and size, their study has been limited because they remain unresolved point like sources in the optical/ultraviolet and X-rays, where they emit. Two main modes of accretion have been identified in Active...
The ground-state 2-proton radioactivity is a rare decay mode that can occur for few nuclei, beyond the proton drip-line and with an even number of protons. The phenomenon is possible due to the pairing interaction that lowers the mass and to the Coulomb and centrifugal barrier, which keeps the last proton pair inside the nucleus, until its tunneling through this barrier. The emission of a...
The s-wave neutron-nucleus scattering length $a_s$ characterizes the low-energy neutron scattering off nuclei. In the effective-range approximation, the neutron-nucleus scattering cross-section at very low energies tends to $4πa^2_s$, giving to the scattering length a sense of nuclear apparent size experienced by a neutron approaching at low energy. Its specific value is the result of a...
The isospin-dependent equation of state of nuclear matter, i.e. symmetry energy $E_{sym}(\rho)$ plays an important role in the study of nuclear physics and astrophysics. The calculation of transport model has shown the $E_{sym}(\rho)$ affects significantly the nucleon emission times in HIC, leading to significant variation of two-nucleon correlation functions.
Recent years, a compact...
Relativistic heavy-ion collisions provide a way to study the properties of nuclear matter under extreme conditions. One method for investigating the characteristics of bulk matter is the femtoscopy technique. This method allows for the extraction of the space-time characteristics of the expanding fireball produced in heavy-ion collisions and to collect information on the interaction between...
Recently, the Richardson-Lucy (RL) algorithm has been successfully applied to extract the source function from the deuteron-$\alpha$ correlation function using the Koonin-Pratt (KP) equation as the forward model. To avoid overfitting to the noise in the data, the total-variation (TV) regularization method was employed. Similarly to Lasso regularization, it is derived from introducing L1-norm...
Two-particle correlations play a pivotal role in understanding the space-time characteristics of particle emission in Heavy-ion collisions. These characteristics are typically represented by a relative emission source and can be obtained using transport model simulations such as the Boltzmann-Uehling-Uhlenbeck (BUU) transport model. We utilize the BUU transport model to simulate the p-p...
The measurement of charged particle pseudorapidity distributions using the STAR Event Plane Detector (EPD) in gold-gold collisions at Beam Energy Scan II energies is presented. Charged particles are detected by the EPD in the $2.15<|\eta|<5.09$ pseudorapidity interval. To account for the detector's response to primary particles, directly measured pseudorapidity distributions are unfolded using...
Multiparticle correlation measurements at the LHC have revealed striking evidence of collective behavior in small collision systems, such as pp and pPb, mirroring phenomena typically observed in heavy-ion (AA) collisions. However, conclusive evidence for jet quenching in pPb collisions remains elusive. This presents a puzzling scenario where the medium described by hydrodynamics, which...
Nucleon-nucleon correlations are essential for understanding the structure of nuclei. They are responsible for the depletion of quantum states below the Fermi level and population of the states above it, that is a characteristic feature of dense many-body systems of strongly interacting fermions. The NN correlations are often distinguished into long- and short-range types depending on their...
The increase in the relative fraction of high-momentum protons in short-range correlated NN pairs with the neutron excess in the nucleus, measured by the CLAS collaboration at the Thomas Jefferson National Accelerator Facility, has stimulated interest in investigating the presence of SRC NN pairs in nuclei far from stability. The GSI/FAIR facility, as the only worldwide facility providing...
Femtoscopy studies of pion radiation in heavy-ion collisions have been conducted extensively at all available collider energies, both theoretically and experimentally. In all these studies a special interest is given to $m_{T}$ dependency of pion femtoscopy radii, usually approximated by a power-law function at transverse momenta above 200~MeV/$c$. However, the radii behaviour has been much...
The study of the reaction mechanisms and of the emission probability of Intermediate Mass Fragments (IMFs) in non-central Heavy Ion collisions was the main aim of the CHIFAR experiment, carried out at LNS-INFN. The CHIMERA collaboration investigated nuclear reactions at the incident beam energy of 20 AMeV using different combination of three beams: $\mathrm{^{124}Sn}$, $\mathrm{^{112}Sn}$ and...
FAZIA is a detector array designed to detect and identify charged fragments produced in heavy-ion collisions in the Fermi energy domain. It is the result of a R&D activity aimed at improving the (Z, A) identification capabilities, which are crucial for investigating the nuclear equation of state (EOS).
Since 2019, FAZIA has been performing experiments at GANIL, coupled with the INDRA array,...
Shared interest in heavy-ion collisions has driven our joint research projects with Scott Pratt. Our projects have ranged from those focused on low relative-velocity correlations through time delays in interactions to balance functions testing correlations induced by pair production. Projects discussed in detail will include imaging of emission sources and the development and growth in...
easurements of Balance Functions were proposed more than two decades ago to probe the evolution of particle production in relativistic heavy ion collisions by Pratt et al.. It subsequently emerged that Balance Functions can also be used to probe the susceptibility of QCD matter near the phase transition and the light quark diffusivity. I will briefly review the theoretical work done in the...
Fluctuations between charged and neutral kaons measured by the ALICE Collaboration in Pb-Pb collisions at the LHC exceed conventional explanations. Previously it was shown that if the scalar condensate is accompanied by an electrically neutral isospin–1 field then the combination can produce large equilibrium fluctuations where $\langle \overline u u \rangle \neq \langle \overline d d...
In this presentation recent extractions of the speed of sound in hot QCD matter are discussed. The measurements are performed using two different analysis techniques, which are applied in PbPb collisions at the LHC with center-of-mass energy per nucleon pair of 2.76 and 5.02 TeV. Special focus to the experimental techniques and prospects for future measurements will be given.
Heavy quarks are produced in hard partonic scatterings at the very early stage of heavy-ion collisions and they experience the whole evolution of the Quark-Gluon Plasma medium. Femtoscopic correlations, i.e. two-particle correlations at low relative momentum, are sensitive to the final-state interactions as well as to the extent of the region from which the correlated particles are emitted. A...
Preliminary data from the Beam-Energy Scan II measurements by the STAR Collaboration at the Relativistic Heavy Ion Collider suggest a dip in the fourth-to-second-order cumulant ratio when plotted vs. beam energy. At the same energy range where the structure appears, a transition from hadrons to quarks is expected, the deconfinement transition. In this paper, the role of quark deconfinement in...
Multiplicity distributions in e+e- and proton-proton collisions analyzed via the combinants method exhibit oscillatory behavior of the modified combinants. The possible sources of these oscillations and their impact on our understanding of the multiparticle production mechanism were discussed [1-5]. The set of combinants, Cj provides a similar measure of fluctuations as the set of cumulant...
The LHCb experiment was originally designed to perform flavour physics observations, however over the years proved to be also an excellent general purpose detector with unique forward acceptance of pseudorapidity from 2.0 to 5.0. One of the areas of interest are the two-particle angular correlations studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of ...
One of the most effective techniques for investigating the mechanism of baryon production is the study of angular correlations between two particles. Angular correlations represent a convolution of various physical processes, such as mini-jets, Bose-Einstein quantum statistics, conservation of momentum, resonances, and other phenomena that contribute to the unique behavior observed for...
The analysis of two-particle angular correlation(s) is a state-of-the-art method developed to probe hadron production mechanisms in the pp collisions at ultra-relativistic energies. It characterizes the likelihood of observing a pair of particles emerging from the collision as a function of their relative emission angle and provides new insight(s) into the underlying physical mechanisms....
The angular correlation function is a powerful tool for exploring hadronization mechanisms. The effects contributing to the angular correlation functions include quantum statistics, nuclear force, energy and momentum conservation, resonance decays, and Coulomb interactions. The angular correlation function can take different forms depending on the quark composition.
The results obtained by...
The current theoretical prediction of the anomalous magnetic moment of
the muon (aμ) in the Standard Model reveals ~5σ discrepancy when
compared to experimental results. The primary source of uncertainty in
the muon anomaly lies in the leading hadronic contribution to the
theoretical prediction of aμ and is expected to be the main limitation
in any potential discovery. The MUonE...
The Compressed Baryonic Matter (CBM) experiment is currently under construction at the Facility for Antiproton and Ion Research (FAIR). Its goal is to explore the phase structure of strongly interacting (QCD) matter at high net-baryon densities and moderate temperatures through heavy-ion and hadron collisions in the energy range of \sqrt{s_{NN}} = 2.9 - 4.9 GeV using the SIS100 beams. As a...
Our current understanding of the dense QCD matter EOS at supra-saturation densities ($> 2 \rho_0$) is currently dominated by valuable yet statistically limited astrophysical observations. This density range is particularly interesting, with evidence suggesting the emergence of deconfined quark matter phases, supported by effective QCD models (ChEFT and pQCD calculations) and astrophysical...
The study of the nuclear equation of state (EoS) plays a pivotal role in the quest of understanding the core of neutron stars. For this, a comprehensive knowledge of the strong interaction among hadrons is crucial, especially those which contain strange quarks. Indeed, recent model calculations show that both two-body and three-body forces between hyperons and nucleons are important for the...
The availability of multidimensional and multivariate data on femtoscopic radii in heavy-ion collisions (HIC) is marginal at centre-of-mass energies of a few GeV. It impairs the development of theoretical models that describe the particle dynamics of HIC at those energies. The currently available femtoscopic radii were primarily extracted from the measurement of identically charged pions,...
The first measurements of femtoscopic correlations with the particle-pair combinations
$\pi^{\pm}$ $K^0_S$ in pp collisions at $\sqrt{s}$ = 13 TeV are reported by ALICE. It is
shown that it is possible to study the elusive $K^*_0(700)$ particle that has been
considered a tetraquark candidate for over forty years. Boson source parameters and final-state interaction parameters are...
The statistical hadronization model is known to describe very well the yields of particles produced in heavy-ion collisions at LHC, RHIC, and SPS over many orders of magnitude. Recently, we have shown [1,2] that at lower energies, not just yields but also spectra of the most abundant particles containing u and d quarks can be reproduced in the thermal model.
Strangeness, heavy compared to...
Identifying products of ultrarelativisitc collisions, such as the ones delivered by the LHC and RHIC, is one of the crucial objectives of experiments such as ALICE and STAR, which are spedicifally dedicated to this task with a number of detectors allowing particle identification (PID) over a broad momentum range. In the case of correlation studies, high purity of the sample is frequently...
Femtoscopy provides a means to explore the space-time structure of the particle emitting source in heavy-ion collisions, and had a fundamental role in the discovery of the Quark-Gluon-Plasma (QGP) created in such collisions. Work continues on the ever-increasing data sets to infer more and more details about the source function. In the past years a novel method was developed that enables the...
