Strange hadrons, especially multi-strange hadrons are good probes for the early partonic stage of heavy ion collisions due to their small hadronic cross sections. In this paper, I give a brief review on the elliptic flow measurements of strange and multi-strange hadrons in relativistic heavy ion collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC).
Collective flow reflects dynamical evolution in high-energy heavy ion collisions. In particular, the strange hadron elliptic flow reflects early collision dynamics. We present results from a systematic analysis of the centrality dependence of strange hadron elliptic flow ($v_2$) measurement of $K_{S}^{0}$, $Λ$ and $Ξ$ for Cu + Cu collisions at 200 GeV. Results for Cu + Cu collisions are compared with results previously reported for Au + Au collisions. We will also compare our data with results from ideal hydrodynamic calculations.
Multi-strange baryon elliptic flow in Au+Au collisions at sqrt(s_NN)= 200 GeV
本文报道了多奇异重子椭圆流$v_2(p_T)$的首次测量结果。多奇异重子的$Ξ+\bar{Xi}$和$Ω+\bar{Omega} in heavy-ion collisions. In minimum bias Au+Au collisions at sqrt(s_NN) = 200 GeV, a significant amount of elliptic flow, comparable to other non-strange baryons, is observed for multi-strange baryons which are expected to be particularly sensitive to the dynamics of the partonic stage of heavy-ion collisions. The $ p_T $ dependence of $ v_2$证实了以前在轻强子中观察到的组分夸克标度数。这些结果支持的想法，观察到的集体运动的相当大的一部分是在RHIC的超相对论性核碰撞的早期部分子阶段开发。
The strange quark hadrons sit at an important crossroads between the light and heavy quark hadrons, but their spectrum is comparatively poorly known. The KLF experiment was recently approved to run in Hall D of Jefferson Lab, and will use an intense secondary beam of $K_L$ mesons with the existing GlueX spectrometer to collect data several orders of magnitude larger than existing dataset. In this talk, I will discuss the expected physics reach of this experiment and the status of its preparations.
The role played by baryonic resonances in the production of final states containing strangeness for proton-proton reactions at 3.5 GeV measured by HADES is discussed by means of several very different measurements. First the associate production of $Δ$ resonances accompanying final states with strange hadrons is presented, then the role of interferences among N$^*$ resonances, as measured by HADES for the first time, is summarised. Last but not least the role played by heavy resonances, with a mass larger than $2$ GeV/c$^2$ in the production of strange and non-strange hadrons is discussed. Exp…
In order to understand strangeness production mechanisms, one can study the correlations of hadrons with hidden strangeness (e.g. the $ϕ$ meson) and open strangeness ($\mathrm{K}^{0}_{\mathrm{S}}$, $Λ$ and $\barΛ$) 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 $ϕ$ mesons in p-Pb collisions allow both the jet and the underlying event components of strange particle production to be probed…
The measurement of the elliptic flow, $v_{2}$, provides a powerful tool for studying the properties of hot and dense medium created in high-energy nuclear collisions. We present the measurement of $v_{2}$ of multi-strange hadrons ($ϕ$, $Ξ$ and $Ω$) in $\sqrt{s_{NN}}$= 200 GeV Au + Au collisions at STAR. In minimum-bias Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, a significant amount of elliptic flow, almost identical to other mesons and baryons, is observed for multi-strange hadrons. Experimental observations of $p_{T}$ dependence of $v_{2}$ of identified particles at RHIC support partoni…
We present STAR measurements of K^{0}_{S}, ϕ, Λ, Ξ, and Ωat mid-rapidity from Au+Au collisions at \sqrt{s_{NN}} = 7.7, 11.5, 19.6, 27, and 39 GeV from the Beam Energy Scan (BES) program at the BNL Relativistic Heavy Ion Collider (RHIC). Nuclear modification factors and baryon-to-meson ratios are measured to understand recombination and parton energy loss mechanisms. Implications on partonic versus hadronic dynamics at low beam energies are discussed.
We present the results on elliptic flow with multi-strange baryons produced in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV. The analysis is performed with the ALICE detector at LHC. Multi-strange baryons are reconstructed via their decay topologies and the v_2 values are analyzed with the two-particle scalar product method. The p_T differential v_2 values are compared to the VISH2+1 model calculation and to the STAR measurements at 200 GeV in Au+Au collisions. We found that the model describes Ξand Ωv_2 measurements within experimental uncertainties. The differential flow of Ξand Ωis similar …
In this contribution, the production rates and the transverse momentum distributions of strange hadrons are reported as a function of charged particle multiplicity. In this analysis, the data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ALICE detector at the LHC are used. It is found that the production rate of $K_{S}^{0}$, $Λ$, $Ξ^{\pm}$, and $Ω$ increases with multiplicity faster than that for charged particles. The higher the strangeness content of the hadron, the more pronounced is the increase. Moreover, the energy and multiplicity dependence of charged particle p…
We present recent results of the mid-rapidity elliptic flow ($v_2$) for multi-strange hadrons and the $ϕ$ meson as a function of centrality in Au + Au collisions at the center of mass energy $\sqrt{s_{NN}}$ = 200 GeV. The transverse momentum dependence of $ϕ$ and $Ω$ $v_2$ is similar to that of pion and proton, indicating that the heavier strange ($s$) quark flows as strongly as the lighter up ($u$) and down ($d$) quarks. These observations constitute a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. In addition, the mass ord…
We report the elliptic flow ($v_{2}$) of $K_{s}^{0}$, $Λ$, $\barΛ$, $ϕ$, $Ξ^{-}$, and $\overlineΞ^{+}$ at mid-rapidity for Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. The transverse momentum ($p_{T}$) and centrality dependence of $v_{2}$ have been studied. The number of constituent quark (NCQ) scaling for all the (multi-)strange hadrons has also been tested. The dependence in the ratio of average $v_{2}$ ($\langle$$v_{2}$$\rangle$) on centrality shows a deviation from unity indicating a difference in nuclear structure and deformation between the isobars. The results show…
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 $\sqrt{s_{NN}}=5.44$ and $5.02$ TeV, respectively, by the ALICE collaboration at the LHC. Particle ratios are presented as a function of multiplicity for $K^{0}_{s}$, $Λ$, $Ξ^{-}$, $\barΞ^{+}$, $Ω^{-}$, $\barΩ^{+}$, $ρ(770)^{0}$, $K^{\ast}(892)^{0}$, $ϕ(1020)$ and $Λ(1520)$. Our results are discussed and compared with predictions of QCD-inspired event generators. Additionally, comparisons with lower energy measurements and smaller syste…
In this proceedings, we have presented the invariant yield measurements of strange and multi strange hadrons such as $K^{0}_{S}$, $Λ$, $\barΛ$, $ϕ$, $Ξ^{-}$, $\barΞ^{+}$, $Ω^{-}$, $\barΩ^{+}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV at midrapidity ($|y|<0.5$). The second and third-order azimuthal anisotropic flow of the above mentioned particles at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV are also discussed. Some of the important observables such as nuclear modification factor ($R_{CP}$), baryon to meson ratio ($Ω/ϕ$), transverse momentum dependence of $v_{2}$ and $v_{3}$ are measured. The n…
One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 7 and 5.02 TeV, respectively. The strangeness enhancement is investigated by measuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strange particles. A smooth increase of strange particle yields relative to the non-strange ones with event multiplicity has been observed in such systems. We report the latest results on multiplicity dependence of strange and mult…
The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity ($\ |y\ | < 0.5$) are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of $\rm{K}^{0}_{S}$, $Λ$, $Ξ$, and $Ω$ increase with the multiplicity faster than what is reported for inclusive charged particles. The increase is found to be more pronounced for hadrons with a larger strangeness content. Possible auto-correlations between the charged particles and the strange hadrons are eva…
In these proceedings, we present the second order ($v_{2}$) and the third order ($v_{3}$) azimuthal anisotropy measurements of strange and multi-strange hadrons such as $K^{0}_{S}$, $Λ$, $\barΛ$, $ϕ$, $Ξ^{-}$, $\barΞ^{+}$, $Ω^{-}$, $\barΩ^{+}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 27 and 54.4 GeV at STAR. The centrality dependence of $v_{2}$ and $v_{3}$ as well as the number of constituent quark scaling (NCQ scaling) for all the particles mentioned above are discussed. The ratio of $v_{2}$ of $ϕ$ mesons to that of $\bar{p}$ is presented at $\sqrt{s_{NN}}$ = 54.4 GeV which gives a hint of ma…
In these proceedings, we present the measurements of elliptic ($v_2$) and triangular ($v_3$) flow of (multi-)strange hadrons and $ϕ$ mesons in 19.6 and 14.6 GeV Au+Au collisions from STAR. The number of constituent quark (NCQ) scaling of $v_2$ and $v_3$ holds well at $\sqrt{ s_{\mathrm{ NN }} } $ = 19.6 GeV, which indicates the collective flow is built up in the partonic stage. At these energies, the anti-particles show better NCQ scaling than the particles for both $v_2$ and $v_3$, which may be caused by the different contributions from the produced and transported quarks.
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 the measurements of strange hadron elliptic flow at mid-rapidity in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 - 200 GeV using the STAR detector in the years 2010 and 2011. The transverse momentum and collision centrality dependence of elliptic flow is presented. At the intermediate transverse momentum $Ω$ baryon and $ϕ$-meson show baryon-meson separation effect similar to proton and pion for minimum-bias Au+Au collision at $\sqrt{s_{NN}}$ =200 GeV. This indicates formation of collective flow at the early partonic phase. The separation between baryons and mesons at intermediate tra…
We study effects of the hadronic rescattering on final observables especially for multi-strange hadrons such as $ϕ$, $Ξ$ and $Ω$ in high-energy heavy-ion collisions within an integrated dynamical approach. In this approach, (3+1)-dimensional ideal hydrodynamics is combined with a microscopic transport model, JAM. We simulate the collisions with or without hadronic rescatterings and compare observables between these two options so that we quantify the effects of the hadronic rescattering. We find that the mean transverse momentum and the elliptic flow parameter of multi-strange hadrons are less…
At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the Quark-Gluon Plasma (QGP) [1]. Such an extreme state of strongly-interacting QCD (Quantum Chromo-Dynamics) matter is produced in the laboratory with high-energy collisions of heavy nuclei, where an enhanced production of strange hadrons is observed [2-6]. Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions [7], is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenome…
The ALICE experiment at the LHC has measured the production of strange hadrons and resonances in Pb-Pb and pp collisions at unprecedented high beam energies. The study of strange hadrons and resonances helps us to understand the properties of the medium created in the heavy-ion collisions and its evolution. We present the yields ($dN/dy$) at mid-rapidity for strange hadrons ($Λ$, $Ξ^{-}$, $Ω^{-}$, their anti-particles and $K_{S}^{0}$) and resonances ($ϕ$ and $K^{*0}$) for several collision centrality intervals. The results from Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV are presented and c…
In these proceedings, we report the elliptic ($v_{2}$) and triangular ($v_{3}$) flow measurements of strange and multi-strange hadrons such as $K_{S}^{0}$, ~$Λ$($\barΛ$), ~$ϕ$, ~$Ξ^{-}$($\barΞ^{+}$), and $Ω^{-}$($\barΩ^{+}$) at mid-rapidity ($|y| < 1.0$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 GeV using high statistics Beam Energy Scan Phase-II (BES-II) data. The transverse momentum ($p_{T}$) dependence, centrality dependence, and the number of constituent quarks (NCQ) scaling of $v_{2}$ and $v_{3}$ are studied for all these particles. A better NCQ scaling is observed in the case of anti…
We present the measurement of centrality dependence of multi-strange hadron ($Ω$, $Ξ$ and $ϕ$) elliptic flow ($v_{2}$) at mid-rapidity in Au+Au collision at $\sqrt{s_{NN}}$ = 200 GeV. We investigate number-of-constituents quark (NCQ) scaling of identified hadrons $v_{2}$ for different collision centralities. Maximum deviation from ideal NCQ scaling observed at the level of 10% for centrality 30-80$%$ at $(m_{T} - m_{0})/n_{q}$ $>$ 0.6 GeV/$c^{2}$. This may indicate smaller contribution to the collectivity from the partonic phase in the peripheral collisions. We also observe the mass ordering o…
The properties of strange and charm mesons in nuclear matter and nuclei are reviewed. Different frameworks are presented and discussed paying a special attention to unitarized coupled-channel approaches. Possible experimental signatures of the in-medium properties of these mesons are also addressed, in particular in connection with the future FAIR facility at GSI.
We study the chemical freeze-out dynamics of strange particles ($K,\, Λ,\, Σ$) from a homogeneous and isotropically expanding hadronic system of $π, K, ρ, N, Λ$ and $Σ$ with zero net baryon density. We use the momentum integrated Boltzmann equation and study their evolution over the bulk hadronic matter, a condition being similar to the one created at top RHIC and LHC energies. The cross-sections, which are input to the equations, are taken either from phenomenological models or parameterized by comparing against experimental data. From this microscopic calculation we find that these strange p…
Ratio of the yield of strange hadrons to pions is considered as an important observable in studying the properties of the system produced in relativistic heavy ion collisions. Production of strange hadrons $K, \bar{K}, Λ, Σ, Ξ$ and $Ω$ have been evaluated microscopically using rate equations by considering their hadronic interaction cross sections in an expanding medium. The yields obtained from rate equations are normalized with thermal pions and compared with the measurements from Pb-Pb collisions at various multiplicities at LHC energy. The calculation has been done for various initial and …
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 investigate the mass spectra of exotic hadrons known as hexaquarks in the form of dibaryons. We use a phenomenological model based on an extended version of the Gürsey-Radicati mass formula for hadrons to include non-charmed baryons, charmed baryons, and non-strange dibaryons to be able to predict masses of potential dibaryon states. We perform six numerical fits of this model to input data for three different sets of masses of baryons and dibaryons. We find that the model can fit some of the data sets well, especially the sets including charmed baryons and non-strange dibaryons, and observ…
