Search

Study of the strangeness production in heavy-ion collisions is one of the most important parts of the physics program of the BM@N and MPD experiments at the NICA accelerator complex. With collision energies sNN of 2.3–3.3 GeV in the fixed target mode at BM@N and 4–11 GeV in the collider mode at MPD, the experiments will cover the region of the maximum net baryon density and provide high-statistics complementary data on different physics probes. In this paper, some results of Monte Carlo studies of hyperon production with the BM@N and MPD experiments are presented, demonstrating their performance for investigation of the objects with strangeness.

The study of strangeness production is among the main tasks in the physics program of the MPD experiment at the NICA accelerator complex. In this paper, the results of the detector performance study for the measurements of the energy dependence of the yields of charged kaons and pions as well as the strangeness-to-entropy ratio are reported.

We review the predicted properties of short-lived resonances produced in heavy-ion collisions at NICA energies and discuss their sensitivity to strangeness production, the hadronization mechanisms, rescattering and regeneration effects in the hadronic phase of nucleus-nucleus collisions. Results of feasibility studies for the reconstruction of resonances in the MPD experimental setup are also presented and discussed.

One of the main tasks of the NICA/MPD physics program is the study of strangeness production in nuclear collisions. In this paper, results of the Monte Carlo investigation of the MPD detector performance for reconstruction of light hypernuclei in central Au + Au collisions are presented.

Strangeness production in heavy-ion collisions is one of the main goals of the scientific program at the NICA accelerator complex. The MPD detector is designed to study the properties of strongly interacting matter at extreme baryon densities. In this article, the MPD performance to measure the excitation function of the strangeness to entropy ratio in central Au + Au collisions is reported. The investigation has been performed at the Laboratory of High Energy Physics, JINR.

The future heavy-ion NICA collider (JINR, Dubna) will provide a variety of beam types with the range of collision energies from 4 to 11A GeV. New experimental data on event-by-event fluctuations and strangeness production allow addressing important QCD properties such as nature of deconfinement phase transition and the existence of the Critical End Point (CEP). Heavy-ion collisions at NICA will be measured with the multi-purpose detector—MPD, which provides precise reconstruction of multiple physics channels. NICA physics goals and the MPD concept are described with the emphasis on the detector performance in the study of the excitation function for high order moments of net-proton event-by-event multiplicity distributions. The results of a feasibility study for measuring at NICA spectra and yields of kaons and pions, and the strangeness-to-entropy ratio are presented as well.

Heavy-ion collisions provide information about the properties of the matter under extreme conditions. Measurement of strangeness production properties provides important information about the collision region evolution. The spatial and temporal characteristics of particle emission can be extracted using femtoscopy technique. The collision energy, centrality, and transverse mass dependence of the three-dimensional charged kaon femtoscopic radii for Au + Au collisions in the Beam Energy Scan program is presented.

NICA is a new flagship project in Dubna aimed at constructing a new accelerator complex for heavy ions. The main goal of the project is experimental exploration of the still poorly known region of the nuclear matter phase diagram of the highest net-baryon density. The MPD detector is a multi-purpose large acceptance spectrometer for studying heavy-ion collisions. An overview is presented of the NICA physics program for studying strangeness production and present MPD performance for reconstructing hyperons and hypernuclei.

One of the main tasks of the NICA/MPD physics program is a study of strangeness production in nuclear collisions. In this paper the MPD detector performance for measurements of multistrange hyperons in Au + Au collisions at NICA energies is presented based on the analysis of realistically simulated data samples. Perspectives of the studies on the strangeness production at the experiment start-up are evaluated.

Two-particle correlations in ∆η and ∆φ are used to study jets, in particular, their particle com- position. While in Pb-Pb collisions this is done to characterize the quark-gluon Plasma, pp and p-Pb collisions serve as a reference and are of interest on their own for their input into the under- standing of particle production mechanisms. Recent ALICE results on the production of strange particles in small systems (pp and p-Pb collisions) reveal the possibility of having similar strange hadron production mechanisms in all collision systems. We study the production mechanism of hidden strangeness ($\phi$ meson) and open strangeness ( $K_S^0$ meson) in jets via two-particle correlations between the strange hadrons and charged primary hadrons in pp collisions at $\sqrt{s}$ = 13 TeV and p-Pb at $\sqrt{s_{NN}}$ = 5.02 TeV collected with the ALICE experiment at the LHC. In this paper, the dependence of the per-trigger yields of strange hadrons on the transverse mo- menta of the trigger and associated particles, as well as on the event multiplicity, is presented on both the near-side and away-side of the h-$K_S^0$, $K_S^0$-h and h-$\phi$ correlation functions. Moreover, the ratios of these yields to the yields extracted from the h-h correlation function are shown. In addition, a comparison to different MC generators is presented.

In this paper we analyze in detail the production of strangeness in proton-proton collisions in the kinematics of large transverse momenta $p_{T}$ of produced hadrons. Using the color dipole framework, we estimated the production cross-sections for kaons, and demonstrated that the shapes of the $p_{T}$-dependence are in agreement with available experimental data. We also analyzed the self-normalized yields of strange hadrons as a function of multiplicity of co-produced hadrons, and found that the predictions are in agreement with the faster-than-linear growth seen in experimental data. Our description is largely parameter-free and complements our previous studies dedicated to the explanation of multiplicity enhancement of quarkonia, as well as $D$- and $B$-mesons., Comment: 12 pages, 6 figures. This paper is a sequel to our earlier publications arXiv:1910.13579, arXiv:2003.13768, arXiv:2008.12446 and arXiv:2012.08284 dedicated to multiplicity dependence of high energy production cross-sections

We investigate $S=-2$ production from the $\Lambda p\to K^+X$ reactions within the effective Lagrangian approach. The $\Lambda p\to K^+\Lambda\Lambda$ and $\Lambda p\to K^+\Xi^-p$ reactions are considered to find the lightest $S=-2$ system, which is $H$-dibaryon. We assume that the $H(2250)\to\Lambda\Lambda$, and $H(2270)\to\Xi^-p$ decays with the intrinsic decay width of 1 MeV. According to our calculations, the total cross-sections for $\Lambda p\to K^+\Lambda\Lambda$ and $\Lambda p\to K^+\Xi^-p$ reactions were found to be of the order of a few $\mu$b in the $\Lambda$ beam momentum range of up to 5 GeV$/c$. Furthermore, the direct access of information regarding the interference patterns between the $H$-dibaryon and non-resonant contributions was demonstrated.

Orientador: Jun Takahashi Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin Resumo: Neste trabalho, estudamos a produção de hádrons estranhos em colisões próton-próton (pp) a energias de (s)^(1/2)= 7 TeV medidas pelo experimento ALICE no acelerador LHC. São resentadas medidas inéditas das taxas de produção em rapidez central do méson (K) também dos bárions ?,? e O- e suas antipartículas correspondentes. As taxas totais de produção excedem significativamente as previsões de modelos que utilizam a Cromodinâmica Quântica Perturbativa (pQCD). Em particular, comparamos as medidas com previsões do simulador de eventos PYTHIA, onde é observado que as previsões concordam com as medidas apenas para momentos transversais (Pt) acima de 6- 7 GcV / c. Este resultado indica que os processos de primeira ordem não-nula implementados no PYTHIA estão bem ajustados, mas a implementação de um cálculo que descreva os dados em baixo Pt ainda é um problema em aberto. Os resultados aqui apresentados devem contribuir para melhorar o entendimento dos mecanismos de produção de partículas na região de baixo Pt¿ Colisões pp são também utilizadas como referência para colisões nucleares de diferentes multiplicidades no estudo da formação do Quark-Gluon Plasma (QGP). Em particular, o aumento da produção de estranheza é considerado um importante observável do QGP. Neste contexto, estudamos a dependência da produção de partículas estranhas com a multiplicidade de partículas carregadas e comprovamos que não há indício de aumento da produção relativa de estranheza cm eventos pp. Isto é um importante resultado, pois complementa os estudos que consideram a possibilidade de formação de QGP em colisões pp Abstract: In this work, we study the production of strange hadrons in proton-proton (pp) collisions at energies of (s)^(1/2)= 7 TeV measured by the ALICE experiment at the LHC. We present the first measurements of particle yields at central rapidities for the (K)meson as well as for the ?, ? e O- baryon and their antiparticles. Total particle production rates exceed predictions by models that use Perturbative Quantum Chromodynamics (pQCD). In particular, we compare our measurements to predictions by the PYTHIA event generator and find that predictions agree with data only at transverse momenta (Pt) higher than 6- 7 GeV / c. This result indicates that the leading order processes implemented in PYTHIA are well adjusted, but the implementation of a calculation that describes the data at low Pt is still an open issue. The results presented here should contribute to improve our understanding of particle production mechanisms at low Pt ¿ Proton-proton collisions are also used as a reference for nuclear collisions of different multiplicities in the study of Quark-Gluon Plasma (QGP) formation. The increase of strangeness production is considered an important observable of the QGP. In this context, we study the dependence of strange particle production with charged particle multiplicity and find that there is no indication of an increase strangeness production rate in pp collisions. This is an important result that contributes to the studies that consider the possibility of QGP formation in pp collisions Doutorado Física Doutor em Ciências

The increase in strangeness production with charged particle multiplicity, as seen by the ALICE collaboration at CERN in p-p, p-Pb and Pb-Pb collisions, is investigated in the hadron resonance gas model taking into account interactions among hadrons using S-matrix corrections based on known phase shift analyses. Strangeness conservation is taken into account in the framework of the canonical strangeness ensemble. A very good description is obtained for the variation of the strangeness content in the final state as a function of the number of charged hadrons in the mid-rapidity region using the same fixed temperature value as obtained in the most central Pb-Pb collisions. It is shown that the number of charged hadrons is linearly proportional to the volume of the system. For small multiplicities the canonical ensemble with local strangeness conservation restricted to mid-rapidity leads to a stronger suppression of (multi-)strange baryons than seen in the data. This is compensated by introducing a global conservation of strangeness in the whole phase-space which is parameterized by the canonical correlation volume larger than the fireball volume at the mid-rapidity. The results on comparing the hadron resonance gas model with and without S-matrix corrections, are presented in detail. It is shown that the interactions introduced by the phase shift analysis via the S-matrix formalism are essential for a better description of the yields data., Comment: 15 pages, 10 figures

Strangeness enhancement is proposed as a signature of QGP formation in high-energy nuclear collisions. The observed relative yield enhancements of hadrons increase with the strangeness content but not with the mass and baryon number of the hadron. To understand this behavior, we have studied on the simulation models. We have found the models EPOS and AMPT are not able to explain simultaneously the effect of strangeness canonical suppression in low-multiplicity events and QGP-like effect in high-multiplicity pp collisions at LHC energies.

A Large Ion Collider Experiment (ALICE) is one of the four big experiments installed at the CERN Large Hadron Collider (LHC) and it is suited to study pp, p--Pb and Pb--Pb collisions. It aims to study the strongly interacting matter at extreme conditions of temperature and density under which the quarks decouple to form a new state of matter called the Quark Gluon Plasma (QGP). Such a state of matter existed a few microseconds after the Big Bang in which the universe was created. Several experimental observables, sensitive to the evolution of the system after the nuclear collisions, reveal important information about the properties of the QGP. Among such observables is the production rate of strange quarks. It is now confirmed that the strange quarks would be produced with higher probability in a QGP scenario with respect to that expected in a pure hadron gas scenario. Therefore, studies of strangeness production can help to determine the properties of the created system. The studies are now revised at much higher LHC energies and are compared with the lower energy measurements to clarify the full picture. The work which will be presented here is related to the strangeness production in p--Pb collisions with ALICE detector. These collisions in particular, can contribute to the understanding of the differences between small and large interacting systems. The excellent tracking and particle identification capabilities of ALICE can be used to reconstruct the strange hadrons by means of the tracks of their weak decays. The analysis status of strange ($K^{0}_{s}$ and $\Lambda$) hadrons in p--Pb at $8.16\text{ TeV}$ at mid-rapidity as a function of $p_{\rm T}$ and centrality will be presented. The comparison of the experimental results with the EPOS and DPMJet predictions will be also discussed., Comment: 4 pages, 6 figures, XXIII DAE-BRNS High Energy Physics Symposium 2018

We present a systematic study of the strange and multistrange particle production in Pb $+$ Pb collisions at $\sqrt{{s}_{NN}}=2.76$ TeV based on paciae model simulations. Two different mechanisms, namely the single string structure variations and multiple string interactions, are implemented in the simulations. These modifications give rise to an enhancement of the string tension value involved in the Lund string fragmentation framework and generate more strange particles in the hadronic final state. By comparing the simulation results with the ALICE experimental data, it turns out that the inclusion of the variable effective string tension in the paciae model results in an improved agreement between theory and experiment on the strangeness production in Pb $+$ Pb collisions.

We present STAR measurements of strange hadron (KS0, Λ, Λ¯, Ξ−, Ξ¯+, Ω−, Ω¯+, and ϕ) production at midrapidity (|y

In this paper, we present the results of the transport, coalescence and statistical model calculations to describe the production of hypernuclei and study their properties in relativistic nucleus-nucleus collisions. Such hypernuclei and low-temperature hypermatter can be produced as a result of hyperon capture by nuclear residues and free nucleons. The dynamical reaction stage leading to the strangeness production is described within the transport cascade and UrQMD models. Large excited hypernuclear species can be formed from target and projectile residues in peripheral collisions. To describe its following evolution at high excitation energies we have generalized the statistical multifragmentation model (SMM) on hypernuclei, as well as the evaporation, fission and Fermi-break-up models at low energies. We calculated the yields, the mass with isotopic distributions of produced nuclei and hypernuclei, and found important regularities and correlations. We have also established how the binding energies of hypernuclei can be evaluated via the comparison of isotope yields. Our approach can be used also for multistrange nuclei. We have extended the coalescence model for the formation of excited hyperclusters from individual baryons in the central collisions. De-excitation of hot coalescence clusters presents a novel mechanism for the hypernuclei production and shows new possibilities for their investigation.

The High Acceptance DiElecton Spectrometer (HADES), installed at the heavy-ion synchrotron SIS18 at the GSI Helmholtzzentrum fur Schwerionenforschung (Germany) and investigates the microscopic properties of resonance matter formed in heavy-ion collision in the 1–2A GeV energy regime. Important topics of the research program are the mechanisms of strangeness production, the emissivity of resonance matter and the role of baryonic resonances herein. The latter topic is also addressed through investigations of exclusive channels in proton and pion beam induced reactions, both for hadronic and semi-leptonic final states. Recent HADES results on electromagnetic radiation and rare (multi-)strange hadron production provided the encouraging prospects for studying QCD matter in the region of nonzero net-baryon density. Hadron and dilepton spectra are confronted with results of other experiments as well as with available model calculations. The future experimental program at SIS18 during FAIR Phase-0 will also be discussed.

Strange particles and hyperfragments in collisions of antiprotons and protons on nuclei have been investigated systematically within a microscopic transport model. The hyperons are produced from the annihilation in antibaryon-baryon collisions and strangeness exchange process in antiproton induced reactions. A coalescence approach is used for constructing the primary hyperfragments in phase space and the statistical model is modified for describing the decay of hyperfragments via evaporating hyperon, neutron, charged particles etc, in which the shell effect, binding energy and root-mean-square radii are taken into account. It is found that the influence of the hyperon-nucleon interaction on the free $\Lambda$ and $\Xi^{-}$ production is negligible. However, the large hyperfragment yields are obvious with the attractive potential. The production of double strangeness hyperfragments are reduced below 1$\mu b$ in comparison to the yields of $\Lambda$-hyperfragments with the cross sections of 0.05-0.1 mb in the antiproton induced reactions on $^{63}$Cu at the incident momenta of 1-5 GeV/c. The light hyperfragments are formed in the dynamical fragmentation process. The energy dependence of hyperfragment formation is weak once the incident energy above the threshold energy for the hyperon production., Comment: 10 pages, 9 figures

A new release of the Monte Carlo event generator Herwig (version 7.2) is now available. This version introduces a number of improvements, notably: improvements to the simulation of multiple-parton interactions, including diffractive processes; a new model for baryonic colour re-connection; spin correlations in both the dipole and angular-ordered parton showers; improvements to strangeness production; an improved choice of evolution variable in the angular-ordered parton shower; support for generic Lorentz structures in BSM models., Comment: 7 pages, 5 figures. Herwig is available from https://herwig.hepforge.org. arXiv admin note: text overlap with arXiv:1705.06919

The capabilities of the new version of the Li\`ege intranuclear cascade model (labeled $\mathrm{INCL}++6$ from now on) are presented in detail. This new version of INCL is able to handle strange particles, such as kaons and the $\mathrm{\ensuremath{\Lambda}}$ and $\mathrm{\ensuremath{\Sigma}}$ hyperons, and the associated reactions and also allows extending nucleon-nucleon collisions up to about $15\text{--}20$ GeV incident energy. Compared to the previous version, new observables can be studied, e.g., kaon, hyperon, and hypernuclei production cross sections (with the use of a suitable de-excitation code) as well as aspects of kaon-induced spallation reactions. The main purpose of this paper is to present the specific ingredients of the new INCL version and its new features, notably the newly implemented variance reduction scheme. We also compare, for some illustrative strangeness production cases, theoretical results calculated using this version of INCL with experimental data.

The dynamics of exotic hypernuclei in heavy-ion collisions has been investigated thoroughly with a microscopic transport model. All possible channels on hyperon ($\Lambda$, $\Sigma$ and $\Xi$) production near threshold energies are implemented in the transport model. The light complex fragments (Z$\leq$2) are constructed with the Wigner-function method. The classical phase-space coalescence is used for recognizing heavy nuclear and hyperfragments and the statistical model is taken for describing the decay process. The nuclear fragmentation reactions of the available experimental data from the ALADIN collaboration are well reproduced by the combined approach. It is found that the in-medium potentials of strange particles influence the strangeness production and fragment formation. The hyperfragments are mainly created in the projectile or target-like rapidity region and the yields are reduced about the 3-order magnitude in comparison to the nuclear fragments. The hypernuclear dynamics of HypHI data is well described with the model. The possible experiments for producing the neutron-rich hyperfragments at the high-intensity heavy-ion accelerator facility (HIAF) are discussed., Comment: 8 pages, 8 figures

HADES measured Au+Au collisions at \(\sqrt{s_{NN}}=2.4\) GeV, which probe very similar temperature and density regions during their time evolution as neutron star merger. Measurements of light nuclei, which contribute to the bulk of the created matter at this energy, as well as rare and penetrating probes like dilepton radiation and strangeness production are presented. In addition, with the start of the FAIR Phase-0 program, new high-statistic data of Ag+Ag collisions at \(\sqrt{s_{NN}}=2.55\) GeV have been collected in March 2019.

In order to understand strangeness production mechanisms, one can study the correlations of hadrons with hidden strangeness (e.g. the $\phi$ meson) and open strangeness ($\mathrm{K}^{0}_{\mathrm{S}}$, $\Lambda$ and $\bar{\Lambda}$) in hard (jet) processes and in soft (bulk) processes. Two-particle angular correlations with $\mathrm{K}^{0}_{\mathrm{S}}$ triggers allow for the study of fragmentation in pp collisions as a function of multiplicity. Similarly, correlations with associated $\phi$ mesons in p-Pb collisions allow both the jet and the underlying event components of strange particle production to be probed. Presented are $\mathrm{K}^{0}_{\mathrm{S}}$-h correlations measured by ALICE in pp collisions at $\sqrt{s} = 13$ TeV, and h-$\phi$ correlations measured in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV., Comment: 5 pages, 3 figues, Proceedings for Strangeness in Quark Matter (SQM 2019)

The nuclear matter at supra-saturation densities might be created in medium and high energy heavy-ion collisions. The strangeness ingredient in dense nuclear matter impacts the equation of state and maybe exists in the neutron stars. On the other hand, heavy-ion collisions provide a unique way for producing the neutron-rich hypernuclides. In this article, the new progress on strangeness physics in heavy-ion collisions is reviewed. Possible experiments at the high-intensity heavy-ion accelerator facility (HIAF) are to be discussed, in particular on the topics of the high-density nuclear equation of state and hypernuclide in the neutron-rich domain. Within the framework of the Lanzhou quantum molecular dynamics (LQMD) model, the strangeness production and high-density nuclear equation of state in heavy-ion collisions near threshold energies has been investigated, i.e., for the reactions of $^{58}$Ni+$^{58}$Ni and $^{197}$Au+$^{197}$Au. The formation mechanism of $\Lambda$-hyperfragments in heavy-ion collisions is to be investigated. A coalescence approach is developed for constructing the primary fragments in phase space. The secondary decay process of the fragments is described by the well-known statistical code. The impacts of nuclear equation of state on the hyperfragment formation are discussed. The mass, charge and kinetic energy spectra of hypernuclides produced in heavy-ion collisions are thoroughly analyzed. It is found that the kaon yields in the high kinetic energy domain are useful for extracting the high-density nuclear equation of state. The $K^{+}$ yields are strongly suppressed with a hard equation of state. However, the hyperon production is weakly influenced by the incompressibility of nuclear matter. The $\Lambda$-nucleon potential impacts the hypernuclide formation, i.e., the attractive potential enhancing the hypernuclide yields. The heavy-ion collisions are available to produce the light mass neutron-rich hypernuclides and the mid-central collisions are favorable for the medium mass hypernuclide formation. Free hyperons are captured by nucleonic fragments to form hypernuclides in the domain of lower kinetic energies and narrower rapidities. A soft equation of state is available for producing the hyperfragments. The results are very valuable for the forthcoming hypernuclide physics at HIAF.

HADES is a multi-purpose charged-particle detector operated at the SIS18 synchrotron located at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany. The provided ion beam energies of 1-2 A GeV are the lowest of all currently running heavy-ion experiments and result in the highest baryo-chemical potentials at freeze-out in case of Au+Au collisions. At this Quark Matter conference we presented results from Au+Au collisions at s NN = 2.4 GeV . The created system exhibits a very clear hierarchy in hadron yields, with about 100 protons, 10 pions, 10 −2 kaons and 10 −4 antikaons per event. The HADES program focuses on four main observables: (subthreshold) strangeness production, particle flow and its anisotropies, virtual photon emission and net-proton number fluctuations.

Strangeness production is a key tool to understand the properties of the medium formed in heavy-ion collisions: an enhanced production of strange particles was early proposed as one of the signatures of the Quark-Gluon Plasma. The ϕ meson, due to its s s ‾ valence quark content, provides insight into strangeness production. The ALICE experiment has measured ϕ meson production in the dimuon channel in the forward rapidity region 2.5 y 4 in Pb–Pb collisions at s NN = 5.02 TeV . The preliminary ϕ meson pT spectra for different centrality classes and the yield as a function of the collision centrality in the transverse momentum range 2 p T 7 GeV / c are presented. These results are also compared with the ones previously obtained in Pb–Pb collisions at s NN = 2.76 TeV .

We present first data on centrality dependent K + , K − and ϕ production in Au+Au collisions at a kinetic beam energy of 1.23 A GeV measured with HADES. We observe no significant increase of the K + / K − and ϕ / K − multiplicity ratios with centrality of the collision. The measured ϕ / K − ratio is found to be larger than results at higher energies. The significant ϕ feed-down contribution to the K − yield substantially softens the measured transverse mass spectrum of K − , explaining its lower observed effective temperature in comparison to the one of K + .

To create conditions which ruled one billionth of a second after the Big Bang, it is necessary to heat and compact the nuclear matter. During the first microseconds after the Big Bang the universe went through such a phase transition at very high temperatures but very low net baryon density. At very high temperatures or densities, the hadrons melt and their constituents, the quarks and gluons, form a new phase of matter, the so called quark-gluon plasma. Relativistic heavy ion collisions aim to create a quark gluon plasma where quarks and gluons can move freely over volumes that are large in comparison to the typical size of a hadron. When the particles collide at high energies, it leads to the conversion of particle collision participants in a much heavier particle. If the energy density is large enough, after a collision occurs the formation of quark-gluon plasma. In the dense nuclear medium, it comes to collective phenomena such as increased production of strangeness, damping charmonium and collective motion of particles. In nuclear medium, it comes to individual collision of quarks, which also hadronize. Using simulation package Pythia, we analyzed the reaction system that results in individual collisions of quarks and antiquarks, and emergence of collective phenomena.

We report results on strangeness production in Pb–Pb collisions at s NN = 2.76 TeV , p-Pb collisions at s NN = 5.02 TeV and pp collisions at s = 7 TeV from the ALICE collaboration. In heavy-ion collisions, the nuclear modification factor RAA of charged pions, kaons and protons shows a strong, centrality dependent suppression with respect to pp collisions. RAA for Ξ is similar to the one for protons. In 0–10% central collisions, RAA for Ω is significantly higher than RAA for Ξ and exceeds unity. The hyperon-to-pion yields measured in pp collisions as a function of the pseudorapidity density of primary charged particles at midrapidity exhibit a pronounced multiplicity dependence similar to p–Pb collisions. The production rate of strange particles increases faster with multiplicity than that of non-strange hadrons. No enhancement is observed for particles with no strange quark content, demonstrating that the observed effect is strangeness rather than mass related.

It is suggested that the recently observed enhancement of the relative yield in $e^+e^-$ annihilation of states with hidden charm and hidden strangeness above 4.43\,GeV is associated with the $S$ wave production of the charmed strange meson pairs $D_{s0}(2317) \bar D_s^* + {\rm c.c.}$ and $D_{s1}^*(2460) \bar D_s+ {\rm c.c.}$. This mechanism implies a pattern of breaking of the Heavy Quark Spin Symmetry (HQSS) that can be tested in the final channels such as $\eta_c(1S) \phi$, $h_c(1P) \eta $, $h_c(1P) \eta' $ produced in the same energy range., Comment: 6 pages, 3 figures

The production of $\mathrm{K^0_S}$, $\Lambda$ and $\Xi$ is measured in jets and underlying events in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE detectors. The corresponding $\Lambda/\mathrm{K^0_S}$ and $\Xi/\Lambda$ ratios are presented as a function of transverse momentum. The hard scatterings are tagged by charged-particle jets ,which are reconstructed with the anti-$k_\mathrm{T}$ algorithm using a resolution parameter $R$ = 0.4. The flow-like correlations and the enhanced production of multi-strange hadrons in small colliding systems may be described by soft components., Comment: 4 pages, 5 figures

Author(s): Steinberg, V; Staudenmaier, J; Oliinychenko, D; Li, F; Erkiner, O; Elfner, H | Abstract: Production of strange hadrons in elementary and heavy-ion reactions is studied with the hadronic transport approach called simulating many accelerated strongly interacting hadrons. The poorly known branching ratios of the relevant hadronic resonances are constrained from the known elementary hadronic cross sections and from invariant mass spectra of dileptons. The constrained model is employed as a baseline to compare to heavy-ion-collision experiments at low energies [Ekin=(1-2)AGeV] and to predict some of the upcoming pion-beam results at the High-Acceptance Di-Electron Spectrometer, which are expected to be sensitive to the resonance properties. The employed vacuum-resonance approach proves to be viable for small systems at these energies, but for large systems additional in-medium effects might be required.

We look from a theoretical perspective at the new phase of matter, quark-gluon plasma (QGP), the new form of nuclear matter created at high temperature and pressure. Here I retrace the path to QGP discovery and its exploration in terms of strangeness production and strange particle signatures. We will see the theoretical arguments that have been advanced to create interest in this determining signature of QGP. We explore the procedure used by several experimental groups making strangeness production an important tool in the search and discovery of this primordial state of matter present in the Universe before matter in its present form was formed. We close by looking at both the ongoing research that increases the reach of this observable to LHC energy scale $pp$ collisions, and propose an interpretation of these unexpected results., Comment: 142 pages, 46 graphic displays, accepted for publication in EPJ-ST

Agradecimentos: This work was supported by CNPq (Conselho Nacional de Desenvolvimento Cient'?fico e Tecnologico) ' grant number 141186/2015-1 Abstract: We present measurements of hadronic resonance, strange and multi-strange particle production in collisions of Xe-Xe and Pb-Pb at the center-of-mass energies of root s(NN) = 5.44 and 5.02 TeV, respectively, by the ALICE collaboration at the LHC. Particle ratios are presented as a function of multiplicity for K-s(0), Lambda, Xi(-), (Xi) over bar (+), Omega(-), (Omega) over bar (+), rho(770)(0), K*(892)(0), phi(1020) and Lambda(1520). Our results are discussed and compared with predictions of QCD-inspired event generators. Additionally, comparisons with lower energy measurements and smaller systems are also presented CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Aberto

The 13th International Conference on Hypernuclear and Strange Particle Physics (HYP2018) is summarized based on plenary talks given in the conference. It covers recent results and future prospects of theoretical and experimental studies on baryon-baryon interactions, hypernuclei, strangeness production, hadrons and nuclei with heavy flavors, and related subjects.

Formation mechanism of hyperfragments with strangeness s=-1 and s=-2 in collisions of antikaons on nuclei has been investigated within a microscopic transport model. Dynamics of pseudoscalar mesons and hyperons is modeled within the transport model, in which all possible reaction channels for creating hyperons such as the elastic scattering, resonance production and decay, strangeness exchange reaction and direct strangeness production in meson-baryon and baryon-baryon collisions have been included. A coalescence approach is developed for constructing hyperfragments in phase space and the decay process is described with a statistical approach. It is found that the $\Xi^{-}$ production is correlated to the K$^{+}$ formation and the hyperons $\Lambda$ and $\Sigma$ are created within a broad rapidity region. The production cross sections of nucleonic fragments and hyperfragments weakly depends on the incident momentum. The yields of $\Lambda-$ hyperfragments are the six order of magnitude of $\Xi^{-}-$ hyperfragments., Comment: 10 pages, 6 figures

Agradecimentos: ST acknowledges the financial support by DST-INSPIRE program of Government of India Abstract: Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects during the hadronization phase in heavy-ion collisions. Measurements in small collision systems provide a necessary baseline for heavy-ion data, help to tune pQCD inspired event generators and give insight into the search for the onset of collective effects. As the phi meson has a longer lifetime compared to other resonances, it is expected that its production would be much less affected by regeneration and re-scattering processes. We report on measurements of phi meson production in minimum bias pp collisions at different beam energies and as a function of charged particle multiplicity with the ALICE detector at the LHC, The results include the transverse momentum (p(T)) distributions of phi as well as the particle yield ratios. Finally, we have also studied the effective strangeness content by comparing our results to theoretical calculations Aberto

We propose a new reaction mechanism for the study of strange and charmed baryon productions. In this mechanism we consider the correlation of two quarks in baryons, so it can be called the two-quark process. As in the previously studied one-quark process, we find large production rates for charmed baryons in comparison with strange baryons. Moreover, the new mechanism causes the excitation of both the $\rho$ mode and the $\lambda$ mode. Using the wave functions for baryons from a quark model, we compute the production rates of various baryon states. We find that the production rates reflect the structure of the wave functions that imply the usefulness of the reactions for the study of baryon structures., Comment: 15 pages, 4 figures. Final version for publication in PTEP

Orientador: Jun Takahashi Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin Resumo: Um estado da matéria altamente interagente, conhecido como o Plasma de Quarks e Glúons (QGP, do inglês Quark-Gluon Plasma), é produzido nas condições de alta temperatura e densidade de energia atingidas em colisões de íons pesados ultra-relativísticos, como as colisões de Pb¿Pb medidas no Grande Colisor de Hádrons (LHC, do inglês Large Hadron Collider). Uma medida chave para a compreensão das propriedades do QGP produzido nestas colisões é taxa de produção de bárions estranhos e multi-estranhos. ALICE (do inglês, A Large Ion Collider Experiment) é um dos quatros principais experimentos em atividade no LHC e tem detectores especialmente projetados para estudar taxas de produção de partículas identificadas em colisões de íons pesados. A excelente capacidade para reconstrução de trajetórias e identificação de partículas permite a reconstrução de bárions multi-estranhos (??, ?+, ?? e ?+), através de canais de decaimentos fracos, em uma larga faixa de momento transversal. Nesta tese, estudamos a produção de partículas multi-estranhas na região de rapidez central em colisões de Pb¿Pb medidas pelo ALICE na nova energia de 5.02 TeV e em 2.76 TeV. As taxas de produção obtidas são normalizadas pelas medidas correspondentes para píons na mesma classe de centralidade para estudar o aumento relativo da produção de bárions multi-estranhos, que é um dos sinais propostos do QGP. Comparações da razão de híperons para píons entre diversos sistemas, como colisões de pp, p¿Pb e Pb¿Pb, mostram que a taxa produção de bárions multi-estranhos em relação a píons segue uma evolução contínua desde colisões pp de baixa multiplicidade até colisões centrais de Pb¿Pb Abstract: A strongly interacting state of matter known as the Quark-Gluon Plasma (QGP) is formed in the high temperature and high energy density conditions reached in ultra-relativistic heavy-ion collisions, such as the Pb¿Pb collisions measured at the Large Hadron Collider (LHC). One of the key measurements for the understanding of the properties of the QGP medium created in these collisions is the production of strange and multi-strange hadrons. ALICE is one of the four major experiments of the LHC and has a detector designed to study identified particle production rates from heavy-ion collisions. The excellent tracking and particle identification capabilities allow the reconstruction of multi-strange baryons (??, ?+, ?? and ?+) via their weak decay channels over a large range in transverse momentum. In this thesis, we study the multi-strange particle production at central rapidity Pb¿Pb collisions measured by ALICE at the unprecedented energy of 5.02 TeV and 2.76 TeV. The yields are normalized by the corresponding measurement of pion production in the same centrality class in order to study the strangeness enhancement, effect predicted as a probe of the QGP. Comparison of hyperon-to-pion ratio between different systems, such as pp, p¿Pb and Pb¿Pb collisions, shows that production of multi-strange baryons relative to pions follows a continuously increasing trend from low multiplicity pp to central Pb¿Pb collisions Doutorado Física Doutor em Ciências CNPQ 141186/2015

We argue for a continuous (dynamical) kinetic freeze-out of K &plusmn, ϕ observed at midrapidity in collisions of Au(1.23 A GeV) + Au. The simulations, by means of a transport model of Boltzmann-&Uuml, hling-Uhlenbeck (BUU) type, point to time independent transverse momentum slope parameters after 20 fm/c. The complex interplay of expansion dynamics and strangeness production/exchange/absorption as well as elastic scatterings involved in the reaction network does not support the previous interpretation of a late freeze-out of K &minus, due to larger cross sections.

We report recent results of strangeness production in Au+Au collisions at s NN = 54.4 GeV and Al+Au fixed-target collisions at s NN = 4.9 GeV from the STAR experiment at RHIC. The collision-energy dependence of strange hadron yields is presented. The pT dependance of nuclear modification factor (RCP) and baryon to meson ratio ( Λ ‾ / K S 0 ) are measured to study the recombination and parton energy loss mechanisms. The STAR fixed-target data are compared to the previous published data from different AGS experiments. The physics implications for collision dynamics are discussed.

We discuss in detail the formation and propagation of multi-strangeness particles in reactions induced by hadron beams relevant for the forthcoming experiments at FAIR. We focus the discussion on the production of the decuplet-particle $\Omega$ and study for the first time the production and propagation mechanism of this heavy hyperon inside hadronic environments. The transport calculations show the possibility of $\Omega$-production in the forthcoming \panda-experiment, which can be achieved with measurable probabilities using high-energy secondary $\Xi$-beams. We predict cross sections for $\Omega$-production. The theoretical results are important in understanding the hyperon-nucleon and, in particular, the hyperon-hyperon interactions also in the high-strangeness sector. We emphasize the importance of our studies for the research plans at FAIR., Comment: 18 pages, 7 figures. Revised version (updated literature list, more text added, typos corrected) accepted for publication in Nuclear Physics A

The Nuclotron-based Ion Collider facility (NICA) is a new high luminosity machine which is under construction in Dubna (Russia). Heavy-ion collisions at the NICA are well suitable to investigate multiple problems of strongly interacting matter, including its Equation of State, phase transformations, modifications of hadron properties in dense medium, as well as critical phenomena. The MPD detector is a spectrometer with a large uniform acceptance capable of momentum measurement and particle identification in the high multiplicity environment of heavy-ion interactions. In this paper, the MPD performance to measure the hyperon production and the excitation function of the kaon-to-pion ratio in Au[Formula: see text]Au collisions at NICA energies is reported.

FAIRNESS 2019, Genova, Italy, 20 May 2019 - 25 May 2019; Journal of physics / Conference series 1667, 012041 (2020). doi:10.1088/1742-6596/1667/1/012041, Published by IOP Publ.39969, Bristol

ALICE has observed that the relative fraction of strange hadrons grows strongly with multiplicity in small collision systems (proton-proton and proton-lead collisions) at LHC energies, in particular for multi-strange baryons. This implies that a proton-proton collision cannot be described as an incoherent sum of parton-parton collisions, an idea that has been central in most proton-proton generators, for example PYTHIA. To accommodate the new ALICE results, models have to introduce significant final-state interactions. These final-state effects can have very different phenomenological origin. To be able to eventually discriminate experimentally between different final-state models, new experimental tools are required and in this paper different multi-differential observables will be tested with this goal in mind. Transverse Spherocity (SO ) is an observable that allows a topological selection of events that are “isotropic” (dominated by multiple soft processes) and “jetty” (where a single hard process is responsible for a significant part of the multiplicity). The underlying event activity is another observable that can be used to vary the amount of soft processes. It can be estimated by measuring the charged-particle multiplicity in the Transverse region (RT ). Using these new observables, ALICE has obtained results for π, K, φ, p, and Ξ production at mid-rapidity ( | η | < 0.8 ) as a function of event shape and underlying event activity in proton-proton collisions at ( S N N ) = 13 TeV . Finally, this contribution will report on how these new multi-differential measurements compare to predictions from PYTHIA and EPOS-LHC.