We report an overview of strangeness production in Cu+Cu and Au+Au collisions at the energies $\sqrt{s_{NN}} =$ 62.4 and 200 GeV. We show new mid-rapidly $dN/dy$ results for the $K^{0}_{S}$, $Λ$, $Ξ$, $Ω$ particles in Cu+Cu \sNN{62} collisions and compare to results in Au+Au \sNN{62} collisions. We show new results for mid-$p_T$ $Λ/K^{0}_{S}$ ratios in Cu+Cu \sNN{62} collisions and again compare to ratios in Au+Au \sNN{62} collisions. Finally, we show the high-$p_{T}$ ($\sim 6.2$ GeV/c) $R_{AA}(K^{0}_{S})$ as a function of system size in Au+Au \sNN{200} collisions and compare to $R_{AA}(π)$.
We report recent results of strangeness and heavy flavor measurements from PHENIX. The topics are: Elliptic flow of strangeness and heavy flavor electron production comparing to the other hadrons, $ϕ$ meson production, and an exotic particle search.
The role of Strangeness as a signal of the Quark Gluon Plasma in relativistic heavy ion experiments is discussed. The current experimental status is briefly presented. Several scenarios which explain the CERN data are discussed.
This talk reviews the physics of dense, strongly interacting matter. The newly acquired experimental data on strangeness production in heavy-ion reactions from 1-10 AGeV is used to probe the physics of in-medium properties of kaons, multi-body collisions, and the search for the baryon-rich quark-gluon plasma.
In this paper I highlight a few selected topics on strange particle production in heavy-ion collisions. By studying the yield and spectra of strange particles we hope to gain understanding of the conditions reached in, and the ensuing dynamics of, the systems produced when ultra-relativistic heavy-ions are collided.
Open questions concerning strangeness production in heavy-ion collisions are discussed with a focus on the experimental aspects. The open points are presented in the context of recent measurements.
Strangeness production has long been proposed as a diagnostic tool for understanding the dynamics of relativistic heavy ion collisions. In this presentation we review the traditional picture of strangeness enhancement as a signature for quark-gluon plasma formation. We then review, in order, some experimental data on strange particle production in $e^{+}e^{-}$, $pp$, $p\bar{p}$, proton-nucleus and nucleus-nucleus collisions. This is not a comprehensive review, but rather an emphasis of a few significant points. Any clear interpretation of strange particle yields measured in heavy ion reactions…
Properties of the hadronic phase of high-energy heavy-ion collisions can be studied by measuring the ratios of hadronic resonance yields to the yields of longer-lived particles. These ratios can be used to study the strength of re-scattering effects, the chemical freeze-out temperature, and the lifetime between chemical and kinetic freeze-out. The restoration of chiral symmetry during the early hadronic phase or near the phase transition may lead to shifts in the masses and increases in the widths of hadronic resonances. The ALICE collaboration has measured the spectra, masses, and widths of t…
We review the experimental results on strangeness and antibaryon production in heavy-ion collisions at the AGS and SPS. We argue that the observed enhancement in kaon production at the AGS is consistent with hadronic description, while the multistrange baryon and antibaryon results at the SPS may need physics beyond hadronic nature. We call the need for measurements of low energy antilambda-proton annihilation cross-section in the modeling of antilambda to antiproton ratio; large value of this ratio is observed in central heavy-ion collisions at the AGS and SPS. We speculate the importance of …
An experimental overview of the energy dependence of strangeness production is presented. The strange hadrons are considered a good probe to study the QCD matter created in relativistic nucleus-nucleus collisions. The heavy-ion experiments at SPS, RHIC, and LHC have recorded a wealth of data in proton-proton, proton-nucleus and nucleus-nucleus collisions at several beam energies. In this proceeding, I discuss the invariant yield and azimuthal anisotropy measurement of strange hadrons in nucleus-nucleus collisions at SPS, RHIC, and LHC.
A study of the yields of strange particles produced in heavy-ion and elementary collisions is presented using preliminary results from the STAR experiment at RHIC. The strange particle production rates, relative to those of p+p, have been proposed as a means of determining an enhancement of strangeness production in heavy-ion collisions. Analysis of results from STAR show that this enhancement measure is reduced, or comparable, when contrasted to that at top CERN SPS energies. A smaller suppression in the p+p yields at RHIC energies due to finite volume effects could be the cause of such a res…
We present an overview of recent STAR results on strangeness production in p+p and heavy-ion collisions at RHIC. In both Cu+Cu and Au+Au collisions we show the centrality dependencies of bulk yield and mid-$p_{T}$ spectrum measurements with new comparisons to theory. The latest $v_{2}$ results for strange particles are presented and prospects for strangeness production in the low energy scan program will be outlined. Finally, we report new measurements of strangeness fragmentation functions for jets in p+p collisions.
With the advent of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), Heavy Ion Physics will enter a new energy regime. The question is whether the signatures proposed for the discovery of a phase transition from hadronic matter to a Quark Gluon Plasma (QGP), that were established on the basis of collisions at the BEVALAC, the AGS, and the SPS, respectively, are still useful and detectable at these high incident energies. In the past two decades, measurements related to strangeness formation in the collision were advocated as potential signatures and were teste…
Strangeness measurement at RHIC energies constitutes one of the favorite theme of the STAR Collaboration. Besides the fact that strangeness enhancement has been proposed as a quark gluon plasma signature, its production provides various and relevant information about the collision evolution and especially on the hadronization process. The investigation of short-lived strange particles as well as their anti-particles and resonances allows an attempt of characterization of the matter created in RHIC heavy ion collisions.
Double strangeness $Ξ^{-}$ production in Au+Au collisions at 2, 4, and 6 GeV/nucleon incident beam energies is studied with the pure hadron cascade version of a multi-phase transport model. It is found that due to larger nuclear compression, the model with the soft equation of state (EoS) gives larger yields of both single strangeness ($K^{+}$ and $Λ+Σ^{0}$) and double strangeness $Ξ^{-}$. The sensitivity of the double strangeness $Ξ^{-}$ to the EoS is evidently larger than that of $K^{+}$ or $Λ+Σ^{0}$ since the phase-space distribution of produced $Ξ^{-}$ is more compact compared to those of …
We report measurements of diagonal susceptibilities for the baryon number, chi_B, electrical charge, chi_Q, third component of isospin, chi_I, strangeness, chi_S, and hypercharge, chi_Y, as well as the off-diagonal chi_BQ, chi_BY, chi_BS, etc. We show that the ratios of susceptibilities in the high temperature phase are robust variables, independent of lattice spacing, and therefore give predictions for experiments. We also investigate strangeness production and flavour symmetry breaking matrix elements at finite temperature. Finally, we present evidence that in the high temperature phase of Q…
We present preliminary STAR results on measurements of multi-strange particles $Ξ$, $Ω$ and their anti-particles from Au+Au and Cu+Cu at $\sqrt{s_{NN}}=62.4$ GeV collisions. In order to better understand the role of strangeness enhancement in nucleus-nucleus collisions and its scaling properties with system size, we compare the results from Au+Au and Cu+Cu reactions for different event centrality classes. Strangeness enhancement is discussed in the context of multi-strange to pion ratios. Finally, $Ω/ϕ$ ratio is shown for different systems and energies for a systematic study.
The experimental data on hadron yields and ratios in central Pb+Pb and Au+Au collisions at SPS and RHIC energies, respectively, are analysed within a two-source statistical model of an ideal hadron gas. These two sources represent the expanding system of colliding heavy ions, where the hot central fireball is embedded in a larger but cooler fireball. The volume of the central source increases with rising bombarding energy. Results of the two-source model fit to RHIC experimental data at midrapidity coincide with the results of the one-source thermal model fit, indicating the formation of an ex…
Measurements of strangeness production in jets help illuminate the QCD mechanisms in fragmentation. Furthermore, they provide a crucial baseline for heavy-ion studies where modifications in jet chemistry have recently been observed by the STAR experiment. We present new results on strange particle production in jets from p+p $\sqrt{s}$ = 200 GeV collisions measured by the STAR experiment. The fragmentation functions of the Λ, \barΛ and K0Short particles are obtained using various jet finding algorithms, and then compared to various models. Strange particle ratios in jets will be obtained and c…
We explore the feasibility of the measurement of charm-jet cross sections in charged-current deep-inelastic scattering at the future Electron-Ion Collider. This channel provides clean sensitivity to the strangeness content of the nucleon in the high-$x$ region. We estimate charm-jet tagging performance with parametrized detector simulations. We show the expected sensitivity to various scenarios for strange parton distribution functions. We argue that this measurement will be key to future QCD global analyses, so it should inform EIC detector designs and luminosity requirements.
Measurements of strangeness production in jets help illuminate the QCD mechanisms in fragmentation. Furthermore, they provide a crucial baseline for heavy-ion studies where modifications in jet chemistry have recently been predicted. We present new results on strange particle production in jets from p+p \sqrt{s} = 200 GeV collisions measured by the STAR experiment. The momentum distributions of the Λ, \barΛ and K0Short particles are obtained using various jet finding algorithms, and then compared to various models. Strange particle ratios in jets are obtained and compared to values obtained fr…
In the frame work of a nuclear overlap model, we estimate the number of nucleon and quark participants in proton-proton, proton-nucleus and nucleus-nucleus collisions. We observe the number of nucleon ($N_{N-part}$)-normalized enhancement of multi-strange particles which show a monotonic increase with centrality, turns out to be a centrality independent scaling behavior when normalized to number of constituent quarks participating in the collision ($N_{q-part}$). In addition, we observe that the $N_{q-part}$-normalized enhancement, when further normalized to the strangeness content, shows a st…
Preliminary results on strange particle production versus collision centrality are presented. STAR measurements from \sqrts = 200 GeV heavy-ion and \pp collisions are compared to SPS measurements. A systematic study of strange particle production is presented with the aim of establishing how the correlation volume of the produced source affects the scale of strange particle creation, including that of the multi-strange baryons. A linear increase of strangeness production with volume has been suggested by thermal models as an indication that the collision region has reached sufficient size such…
>A review of meson emission in heavy ion collisions at incident energies around 1 -- 2 $A\cdot$GeV is presented. It is shown how the shape of the spectra and the various particle yields vary with system size, with centrality and with incident energy. A statistical model assuming thermal and chemical equilibrium and exact strangeness conservation (i.e. strangeness conservation per collision) explains most of the observed features. Emphasis is put onto the study of $K^+$ and $K^-$ emission. In the framework of this statistical model it is shown that the experimentally observed equality of $K^+$ …
Identified charged kaon, pion, and proton spectra and ratios from sqrt(s_NN) = 200 and 62.4 GeV Cu+Cu collisions are studied with a hydro-motivated blast-wave and a statistical model framework in order to explore the strangeness production at RHIC and characterize the bulk freeze-out properties of the created system. The spectra are measured at mid-rapidity |y|<0.1 over the transverse momentum range of 0.25 < p_T < 1.2 GeV/c with particle identification derived from the ionization energy loss in the STAR Time Projection Chamber. The multi-dimensional systematic study of pi(+/-), K(+/-), p and …
The vacuum parton creation in quickly varying external fields is studied at the time scale of order 1 fm/$c$ typical for the quark-gluon plasma formation and thermalization. To describe the pre-equilibrium evolution of the system the transport kinetic equation is employed. It is shown that the dynamics of production process at times comparable with particle inverse masses can deviate considerably from that based on classical Schwinger-like estimates for homogeneous and constant fields. One of the effects caused by non-stationary chromoelectric fields is the enhancement of the yield of $s\bar{s…
Strangeness production in heavy-ion collisions, when compared to proton proton collisions, is potentially a sensitive probe for collective energy deposition and therefore for reaction mechanisms in general. It may therefore provide insight into possible QGP formation in dense nuclear matter. To establish an understanding of the observed yields, a systematic study of high density baryon matter at different beam energies is essential. This might also reveal possible discontinuities in the energy dependence of the reaction mechanism. We present preliminary results for kaon production in Au+Au col…
We study the in-medium effects in strangeness production in heavy-ion collisions at (sub-)\-threshold energies of 1 - 2 A GeV based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach. The in-medium modifications of the antikaon $(\bar K = K^-, \bar K^0)$ properties are described via the self-consistent coupled-channel unitarized scheme based on a SU(3) chiral Lagrangian which incorporates explicitly the $s-$ and $p-$ waves of the kaon-nucleon interaction. This scheme provides the antikaon potential, spectral functions and reaction cross sections as well as their depende…
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…
Fluctuations of conserved quantities, such as baryon, electric charge and strangeness number, are sensitive observables in heavy-ion collisions to search for the QCD phase transition and critical point. In this paper, we performed a systematical analysis on the various cumulants and cumulant ratios of event-by-event net-strangeness distributions in Au+Au collisions at $\sqrt{s_{NN}}$=7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV from UrQMD model. We performed a systematical study on the contributions from various strange baryons and mesons to the net-strangeness fluctuations. The results demonstra…
We construct the QCD equation of state at finite chemical potentials including net baryon, electric charge, and strangeness, based on the conserved charge susceptibilities determined from lattice QCD simulations and the equation of state of the hadron resonance gas model. For the application to relativistic heavy ion collisions we consider the situation of strangeness neutrality and matter with a fixed electric charge-to-baryon ratio, resembling that of heavy nuclei. The importance of finite electric charge and strangeness chemical potentials for particle production in heavy ion collisions is …
Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects in the hadronic phase of heavy-ion collisions. As the $ϕ$ meson has a longer lifetime compared to other resonances, it is expected that its production will not be affected by regeneration and re-scattering processes. Measurements in small collision systems such as proton-proton (pp) collisions provide a necessary baseline for heavy-ion data and help to tune pQCD inspired event generators. Given that the $ϕ$ is a bound state of strange-antistrange quark pair (s$\bar{\rm{s}}$), measurement…
The centrality dependence of (multi-)strange hadron abundances is studied for Pb(158 AGeV)Pb reactions and compared to p(158 GeV)Pb collisions. The microscopic transport model UrQMD is used for this analysis. The predicted Lambda/pi-, Xi-/pi- and Omega-/pi- ratios are enhanced due to rescattering in central Pb-Pb collisions as compared to peripheral Pb-Pb or p-Pb collisions. A reduction of the constituent quark masses to the current quark masses m_s \sim 230 MeV, m_q \sim 10 MeV, as motivated by chiral symmetry restoration, enhances the hyperon yields to the experimentally observed high values…
Probing strangeness with event topology classifiers in pp collisions at energies available at the CERN Large Hadron Collider with the rope hadronization mechanism in PYTHIA
We construct the QCD equation of state at finite chemical potentials including net baryon, electric charge, and strangeness based on the results of lattice QCD simulations and the hadron resonance gas model. The situation of strangeness neutrality and a fixed charge-to-baryon ratio, which resembles that of heavy nuclei, is considered for the application to relativistic heavy-ion collisions. This increases the values of baryon chemical potential compared to the case of vanishing strangeness and electric charge chemical potentials, modifying the fireball trajectory in the phase diagram. We perfo…
Fluctuations and correlations of conserved charges are sensitive observables for studying the QCD phase transition and critical point in high-energy heavy-ion collisions. We have studied the centrality and energy dependence of mixed-cumulants (up to fourth order) between net-baryon and net-strangeness in Au+Au collisions at $\sqrt{s_{NN}}$= 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV from UrQMD model. To compare with other theoretical calculations, we normalize these mixed-cumulants by various order cumulants of net-strangeness distributions. We found that the results obtained from UrQMD calculatio…
New experimental data on transverse momentum spectra of strange particles (KS0, K-, K*, phi,...) produced in pp collisions at sqrt s = 200 GeV obtained by the STAR and PHENIX collaborations at RHIC are analysed in the framework of z-scaling approach. Scaling properties of the data z-presentation are illustrated. Self-similarity of strange particle production is discussed. A microscopic scenario of constituent interactions developed within the z-scaling approach is used to study constituent energy loss, proton momentum fraction and recoil mass in dependence on the transverse momentum, strangene…
These are the proceedings of the experimental overview of the production of open heavy flavor at the international conference Strangeness in Quark Matter 2016. Instead of a comprehensive overview, I focus on a few topics which the reader might find particularly interesting.
The main goal of the ALICE experiment is to study the properties of the hot and dense medium created in ultra-relativistic heavy-ion collisions. The measurement of the (multi-)strange particles is an important tool to understand particle production mechanisms and the dynamics of the quark-gluon plasma (QGP). We report on the production of K$^{0}_{S}$, $Λ$($\overlineΛ$), $Ξ^{-}$($\overlineΞ^{+}$) and $Ω^{-}$($\overlineΩ^{+}$) in proton-lead (p-Pb) collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and lead-lead (Pb-Pb) collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV measured by ALICE at the LHC. The com…
