Multi-strange Hadrons Research Articles

Core-corona procedure and microcanonical hadronization to understand strangeness enhancement in proton-proton and heavy ion collisions in the EPOS4 framework

The multiplicity dependence of multistrange hadron yields in proton-proton and lead-lead collisions at several TeV allows one to study the transition from very big to very small systems, in particular, concerning collective effects. I investigate this, employing a core-corona approach based on new microcanonical hadronization procedures in the 4 framework, as well as new methods allowing one to transform energy-momentum flow through freeze-out surfaces into invariant-mass elements. I try to disentangle effects due to “canonical suppression” and “core-corona separation”, which will both lead to a reduction of the yields at low multiplicity. Published by the American Physical Society 2024

Theoretical prediction of cosmic rays models for strange particles production at RHIC energy

This study conducts a comprehensive assessment of Monte Carlo models, including Sibyll, EPOS-LHC, and EPOS4, in the context of simulating strange and multi-strange hadron production within high-multiplicity proton–proton collisions at 200 GeV. The analysis reveals common trends across various particle types: models tend to overestimate low transverse momentum (pT) distributions and approach experimental data as pT increases. EPOS-LHC produce better predictions in the intermediate pT range. However, none of the models adequately reproduce pT distributions for Λ and Λ̄ particles, typically underpredicting the data. EPOS4_Hydro performs relatively better due to its ability to account for reduced particle multiplicity at high pT and energy redirection into flow. For Ξ and Ξ̄ particles, models underpredict distributions at high pT, except for EPOS4_Hydro, which consistently overpredicts. Additionally, the study delves into particle ratios, such as Λ̄/Λ and Ξ+/Ξ−, highlighting varying model performance. The mean transverse momentum increases with particle mass, and specific models demonstrate good fits for certain mass ranges. EPOS-LHC and EPOS4 with hydrodynamics were notably accurate for particles below 0.6 GeV. Within the mass range of 0.6 to 1.4 GeV, EPOS-LHC displayed the closest fit. However, particles surpassing 1.2 GeV showed higher accuracy with EPOS4 without hydrodynamics. These insights underscore the significance of selecting appropriate Monte Carlo models based on specific research requirements in high-energy physics.

Production of {textrm{K}}_{textrm{S}}^0 , Λ ( overline{Lambda} ), Ξ±, and Ω± in jets and in the underlying event in pp and p–Pb collisions

The production of strange hadrons ( {textrm{K}}_{textrm{S}}^0 , Λ, Ξ±, and Ω±), baryon-to-meson ratios (Λ/ {textrm{K}}_{textrm{S}}^0 , Ξ/ {textrm{K}}_{textrm{S}}^0 , and Ω/ {textrm{K}}_{textrm{S}}^0 ), and baryon-to-baryon ratios (Ξ/Λ, Ω/Λ, and Ω/Ξ) associated with jets and the underlying event were measured as a function of transverse momentum (pT) in pp collisions at sqrt{s} = 13 TeV and p Pb collisions at sqrt{s_{textrm{NN}}} = 5.02 TeV with the ALICE detector at the LHC. The inclusive production of the same particle species and the corresponding ratios are also reported. The production of multi-strange hadrons, Ξ± and Ω±, and their associated particle ratios in jets and in the underlying event are measured for the first time. In both pp and p–Pb collisions, the baryon-to-meson and baryon-to-baryon yield ratios measured in jets differ from the inclusive particle production for low and intermediate hadron pT (0.6–6 GeV/c). Ratios measured in the underlying event are in turn similar to those measured for inclusive particle production. In pp collisions, the particle production in jets is compared with Pythia 8 predictions with three colour-reconnection implementation modes. None of them fully reproduces the data in the measured hadron pT region. The maximum deviation is observed for Ξ± and Ω± which reaches a factor of about six. The event multiplicity dependence is further investigated in p−Pb collisions. In contrast to what is observed in the underlying event, there is no significant event-multiplicity dependence for particle production in jets. The presented measurements provide novel constraints on hadronisation and its Monte Carlo description. In particular, they demonstrate that the fragmentation of jets alone is insufficient to describe the strange and multi-strange particle production in hadronic collisions at LHC energies.

Production and enhancement of (multi-) strange hadrons in Au+Au collisions at sNN=200 GeV RHIC energy and Pb+Pb collisions at sNN=2.76 TeV LHC energy

In this article, we investigate $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Pb}+\mathrm{Pb}$ collision systems to understand the (multi-) strange hadron production at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies using the Monte Carlo $\mathrm{HYDJET}++$ model. We study the ${p}_{T}$ spectra, particle ratios, and strangeness enhancement factor for (multi-) strange hadrons. The ${p}_{T}$ spectra of ${K}^{+}({K}^{\ensuremath{-}})$, ${K}_{s}^{0}$, $\mathrm{\ensuremath{\Lambda}}(\overline{\mathrm{\ensuremath{\Lambda}}})$, ${\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}({\overline{\mathrm{\ensuremath{\Xi}}}}^{+})$, and ${\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}}({\overline{\mathrm{\ensuremath{\Omega}}}}^{+})$ are shown for both $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{Pb}+\mathrm{Pb}$ collision systems in various centrality intervals. We find that the strange quark thermalization might not be achieved by the model for multistrange baryons toward peripheral collisions. The ${p}_{T}$-differential particle ratios, focused on strange hadron-to-meson ratios, are reported for 0--5% and 40--60% centrality intervals for both the collision systems. We observe an enhancement in the particle ratios at intermediate ${p}_{T}$ region. ${p}_{T}$ integrated strange-to-nonstrange ratios suggest that chemical equilibrium might not be achieved for multistrange hadrons. We report the strangeness enhancement factor for $\mathrm{\ensuremath{\Lambda}}(\overline{\mathrm{\ensuremath{\Lambda}}})$, ${\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}({\overline{\mathrm{\ensuremath{\Xi}}}}^{+})$, and ${\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}}+{\overline{\mathrm{\ensuremath{\Omega}}}}^{+}$ at both RHIC and LHC energies. An increase in the enhancement factor is observed with the increase in strangeness content of the baryons. We also observe that enhancement is higher in $\mathrm{Au}+\mathrm{Au}$ collisions than in $\mathrm{Pb}+\mathrm{Pb}$ collisions. Further, we compare the $\mathrm{HYDJET}++$ results with the experimental data and various other simulation models, wherever possible.

Elliptic flow of strange and multi-strange hadrons in isobar collisions at √SNN = 200 GeV at RHIC

We report the elliptic flow (υ2) of Ks0, Λ, Ξ¯+, ϕ, Ξ−, and Ξ+ at midrapidity for Ru+Ru and Zr+Zr collisions at √SNN = 200 GeV. The transverse momentum (pT) and centrality dependence of υ2 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 υ2 (〈υ2〉) on centrality shows a deviation from unity indicating a difference in nuclear structure and deformation between the isobars. The results show a systematic size dependence when compared to Cu+Cu, Au+Au, and U+U collisions at similar beam energies.

Study of strange particle pT spectra in heavy-ion collisions at relativistic energies

The transverse momentum distributions of strange and multi-strange hadrons produced in most central Au+Au collisions at RHIC-BES energies were studied using the Boltzmann-Gibbs blast-wave model. The energy dependence of the kinetic freeze-out parameters is presented and discussed.

Highlights from the NA61/SHINE Experiment

The NA61/SHINE experiment is a fixed-target, broad acceptance facility at the CERN SPS. This contribution summarizes the most recent results from the strong interactions NA61/SHINE programme and presents news on the detector upgrade in preparation for the future data taking. The strong interactions programme consists in a two-dimensional scan in beam momentum (from 13A to 150A/158A GeV/c, \sqrt{s_{NN}} from 5.1 to 17.3 GeV) and system size (p + p, Be + Be, Ar + Sc, Xe + La reactions). The experiment searches for the second-order critical end-point in the temperature versus baryo-chemical potential phase diagram and studies the properties of the onset of deconfinement discovered by its predecessor, NA49 at the CERN SPS. The presented results include K/{\pi} multiplicity ratios as a function of energy and system size, singly and multi-strange hadron production in p + p reactions, multiplicity and net-charge fluctuations measured by higher order moments in p + p, Be + Be and Ar + Sc collisions, proton and charged hadron intermittency in Ar + Sc and Pb + Pb reactions, HBT measurements in Ar + Sc and collective electromagnetic effects in Ar + Sc collisions.

Production of strange hadrons in jets and underlying events in pp and p–Pb collisions with ALICE

The production of strange (, Λ) and multi-strange (Ξ± and Ω±) hadrons in jets and underlying events in pp and p–Pb collisions is studied with ALICE at the LHC. Transverse momentum (p T) differential density distribution of particles produced in a jet is compared to that of inclusive particle production and that in underlying events. The particle yield ratios of and as a function of p T are also investigated in jets and underlying events. The production of the multi-strange hadrons, Ξ± and Ω±, and the corresponding ratio in jets and underlying events are measured for the first time. The p T-differential density distribution of hadrons associated with hard scattering decreases slower than that for inclusive production. The baryon-to-meson and baryon-to-baryon ratios measured in jets exhibit clear differences from values obtained from the inclusive spectra in the intermediate p T range. The p T distribution of strange hadrons produced in jets is also studied in pp collisions at and and in p–Pb collisions at . The p T spectra of particle produced in jets are independent of collision systems and collision energies. No apparent collision energy and collision system dependence is observed for the particle yield ratios of and associated with energetic jets. These new results are compared to PYTHIA 8 event generator. The ratio are generally reproduced by the model, but large discrepancies between data and PYTHIA simulations are observed for .

Azimuthal anisotropy measurement of multi-strange hadrons in Au+Au collision at √SNN = 27 and 54.4 GeV at STAR

In these proceedings, we present the second order (ν2) and the third order (ν3) azimuthal anisotropy measurements of strange and multi-strange hadrons such as KS0, Λ, Λ¯, ϕ, Ξ−, Ξ¯+, Ω−, Ω¯+ in Au+Au collisions at √SNN = 27 and 54.4 GeV at STAR. The centrality dependence of ν2 and ν3 as well as the number of constituent quark scaling (NCQ scaling) for all the particles mentioned above are discussed. The ratio of ν2 of ϕ mesons to that of p¯ is presented at √SNN = 54.4 GeV which gives a hint of mass ordering violation at low pT.

Multi-strange hadron production in p+p interactions at √SNN= 17.3 GeV

The production of multi-strange hadrons in proton-proton interactions is currently studied with the NA61/SHINE experiment at the SPS. These particles are reconstructed via their weak decay typologies, exploiting the tracking and particle identification capabilities of NA61/SHINE. New measurements of rapidity and transverse momentum spectra of Ξ−and Ξ resonances and their antiparticles are shown. The results are compared to those observed in A+A collisions as well as to model predictions.

Azimuthal anisotropy of strange and multi-strange hadrons in U+U collisions at sNN = 193GeV at STAR

In this paper, we present systematic measurements of azimuthal anisotropy for strange hadrons ([Formula: see text], [Formula: see text] and [Formula: see text]) and multi-strange hadrons ([Formula: see text] and [Formula: see text]) at mid-rapidity ([Formula: see text]) in U[Formula: see text]U collisions at [Formula: see text] GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). Flow coefficients ([Formula: see text], [Formula: see text] and [Formula: see text]) are presented as a function of transverse momentum ([Formula: see text]) for minimum bias and three different centrality intervals. The [Formula: see text] sub-event plane method is used to obtain the results. These measurements are compared with the published results from Au[Formula: see text]Au collisions at [Formula: see text] GeV. Number of Constituent Quark (NCQ) scaling of the measured flow coefficients in U[Formula: see text]U collisions is discussed. We also present the ratio of [Formula: see text] scaled by the participant eccentricity ([Formula: see text]) to explore system size dependence and collectivity in U[Formula: see text]U collisions. The measured flow coefficients are compared with hydrodynamic and transport model calculations.

Azimuthal anisotropy measurements of strange and multistrange hadrons in U+U collisions at sNN=193 GeV at the BNL Relativistic Heavy Ion Collider

We present systematic measurements of azimuthal anisotropy for strange and multistrange hadrons (Ks0, Λ, Ξ, and Ω) and ϕ mesons at midrapidity (|y|< 1.0) in collisions of U+U nuclei at sNN=193 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. Transverse momentum (pT) dependence of flow coefficients (v2, v3, and v4) is presented for minimum bias collisions and three different centrality intervals. Number of constituent quark scaling of the measured flow coefficients in U+U collisions is discussed. We also present the ratio of vn scaled by the participant eccentricity (ɛn2) to explore system size dependence and collectivity in U+U collisions. The magnitude of v2/ɛ2 is found to be smaller in U+U collisions than that in central Au+Au collisions contradicting naive eccentricity scaling. Furthermore, the ratios between various flow harmonics (v3/v23/2, v4/v24/2) are studied and compared with hydrodynamic and transport model calculations.9 MoreReceived 18 March 2021Accepted 24 May 2021DOI:https://doi.org/10.1103/PhysRevC.103.064907©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective flowRelativistic heavy-ion collisionsNuclear Physics

Production of light-flavor hadrons in pp collisions at sqrt{s}~=~7text { and }sqrt{s} = 13 , text { TeV}

The production of pi ^{pm }, mathrm{K}^{pm }, mathrm{K}^{0}_{S}, mathrm{K}^{*}(892)^{0}, mathrm{p}, phi (1020), Lambda , Xi ^{-}, Omega ^{-}, and their antiparticles was measured in inelastic proton–proton (pp) collisions at a center-of-mass energy of sqrt{s} = 13 TeV at midrapidity (|y|<0.5) as a function of transverse momentum (p_{mathrm{T}}) using the ALICE detector at the CERN LHC. Furthermore, the single-particle p_{mathrm{T}} distributions of mathrm{K}^{0}_{S}, Lambda , and overline{Lambda } in inelastic pp collisions at sqrt{s} = 7 TeV are reported here for the first time. The p_{mathrm{T}} distributions are studied at midrapidity within the transverse momentum range 0le p_{mathrm{T}}le 20 GeV/c, depending on the particle species. The p_{mathrm{T}} spectra, integrated yields, and particle yield ratios are discussed as a function of collision energy and compared with measurements at lower sqrt{s} and with results from various general-purpose QCD-inspired Monte Carlo models. A hardening of the spectra at high p_{mathrm{T}} with increasing collision energy is observed, which is similar for all particle species under study. The transverse mass and x_{mathrm{T}}equiv 2p_{mathrm{T}}/sqrt{s} scaling properties of hadron production are also studied. As the collision energy increases from sqrt{s} = 7–13 TeV, the yields of non- and single-strange hadrons normalized to the pion yields remain approximately constant as a function of sqrt{s}, while ratios for multi-strange hadrons indicate enhancements. The p_mathrm{{T}}-differential cross sections of pi ^{pm }, mathrm {K}^{pm } and mathrm {p} (overline{mathrm{p}}) are compared with next-to-leading order perturbative QCD calculations, which are found to overestimate the cross sections for pi ^{pm } and mathrm{p} (overline{mathrm{p}}) at high p_mathrm{{T}}.

The Compressed Baryonic Matter Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment at FAIR aims to study the area of the QCD phase diagram at high net baryon densities and moderate temperatures using heavy-ion collisions. The FAIR accelerator will provide high-intensity heavy-ion beams up to Au ions in the beam momentum range 3.5A-12A GeV/c per nucleon. In order to achieve it's physics goals and to perform multi-differential measurements of rare probes such as multistrange hadrons or hypernuclei, CBM plans to operate at unprecedented peak interaction rates of up to 10 MHz.Following an introduction into the physics program of the CBM, recent developments related to the preparation of the experiment, physics performance studies, and detector components tests within the so-called FAIR PHASE-0 program are discussed. In particular, the status of the mCBM project at GSI, which operated with high-intensity beams for the first time last year and combines various CBM detector subsystems with a common data acquisition system (DAQ), are presented.

Light-flavour hadron production vs. multiplicity in pp and in p–Pb collisions with ALICE

The study of light-flavour hadron production plays an important role in understanding the dynamics of the strongly-interacting system created in high-multiplicity pp and p–Pb collisions at the LHC energies. Historically, it has been assumed that no QGP is formed in small collision systems, but this paradigm is challenged by the observation of collective-like behaviour and strangeness enhancement in high-multiplicity pp and p–Pb collisions. Exploiting its optimal particle identification capabilities, the ALICE experiment is able to measure pion, kaon, (anti-)proton, strange and multi-strange hadron production in a wide transverse momentum range. We report on the study of light-flavour hadron production as a function of multiplicity and center-of-mass energy in pp and p–Pb collisions using the ALICE apparatus. In addition, new multi-differential measurements are presented, comparing identified particle production in the underlying event to the one in jets.

Evidence of coalescence sum rule in elliptic flow of identified particles in high-energy heavy-ion collisions

The major goal of high-energy heavy-ion collisions is to study the properties of the deconfined quark gluon plasma (QGP), such as partonic collectivity. The collective motion of constituent quarks can be derived from the anisotropic flow measurements of identified hadrons within the coalescence framework. Based on published results of elliptic flow (v2), we shall test the coalescence sum rule using K±, p, p¯, Λ and Λ¯, and further extract v2 values for produced u(d, u¯, d¯), s and s¯ quarks, as well as transported u(d) quarks in 10-40% Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39 and 62.4 GeV. We also attempt to link the v2 difference between π− and π+ to the different numbers of u and d quarks in the initial gold ions, and to relate the v2 measurements of multi-strange hadrons to the formation times of ϕ, Ω± and Ξ+.

Through the looking-glass with ALICE into the quark-gluon plasma: A new test for hadronic interaction models used in air shower simulations

Recently, the ALICE Collaboration reported an enhancement of the yield ratio of strange and multi-strange hadrons to charged pions as a function of multiplicity at mid-rapidity in proton-proton, proton-lead, lead-lead, and xenon-xenon scattering. ALICE observations provide a strong indication that a quark-gluon plasma is partly formed in high multiplicity events of both small and large colliding systems. Motivated by ALICE's results, we propose a new test for hadronic interaction models used for analyzing ultra-high-energy-cosmic-ray (UHECR) collisions with air nuclei. The test is grounded in the almost equal column-energy density in UHECR-air collisions and lead-lead collisions at the LHC. We applied the test to post-LHC event generators describing hadronic phenomena of UHECR scattering and show that these QCD Monte Carlo-based codes must be retuned to accommodate the strangeness enhancement relative to pions observed in LHC data.

Evolution of strange and multi-strange hadron production with relative transverse multiplicity activity in underlying event

In this work, the relative Underlying event (UE) transverse multiplicity activity classifier (R_mathrm{{T}}) is used to study the strange and multi-strange hadron production in proton-proton collisions. Our study with R_mathrm{{T}} would allow to disentangle these particles, which are originating from the soft and hard QCD processes. We have used the PYTHIA 8 Monte-Carlo (MC) with a different implementation of color reconnection and rope hadronization models to demonstrate the proton-proton collisions data at sqrt{s}~= 13 TeV. The relative production of strange and multi-strange hadrons are discussed extensively in low and high transverse activity regions. In this contribution, the relative strange hadron production is enhanced with increasing R_mathrm{{T}}. This enhancement is significant for the strange baryons as compared to mesons. In addition, the particle ratios as a function of R_mathrm{{T}}~confirm the baryon enhancement in new Color Reconnection (newCR), whereas the Rope model confirms the baryon enhancement only with strange quark content. Experimental confirmation of such results will provide more insight into the soft physics in the transverse region, which will be useful to investigate various tunes based on hadronization and color reconnection schemes.

Multiplicity dependence of pi , K, and p production in pp collisions at sqrt{s} = 13\xa0TeV

This paper presents the measurements of pi ^{pm }, mathrm {K}^{pm }, text {p} and overline{mathrm{p}} transverse momentum (p_{text {T}}) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at sqrt{s} = 13 text {TeV} with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a p_{text {T}} range from 0.1 to 20 text {GeV}/c and are done in the rapidity interval |y|<0.5. The p_{text {T}}-differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at sqrt{s} = 7 text {TeV}, which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the p_{text {T}}-integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems.

Enhanced production of strange baryons in high-energy nuclear collisions from a multiphase transport model

We introduce additional coalescence factors for the production of strange baryons in a multiphase transport (AMPT) model in order to describe the enhanced production of multistrange hadrons observed in Pb-Pb collisions at $\rm \sqrt{s_{NN}}$ = 2.76 TeV at the Large hadron Collider (LHC) and Au+Au collisions at $\rm \sqrt{s_{NN}}$ = 200 GeV at Relativistic Heavy-Ion Collider (RHIC).This extended AMPT model is found to also give a reasonable description of the multiplicity dependence of the strangeness enhancement observed in high multiplicity events in $pp$ collisions at $\rm \sqrt{s}$ = 7 TeV and $p$-Pb collisions at $\rm \sqrt{s_{NN}}$ = 5.02 TeV. We find that the coalescence factors depend on the system size but not much on whether the system is produced from A+A or p+A collisions. The extended AMPT model thus provides a convenient way to model the mechanism underlying the observed strangeness enhancement in collisions of both small and large systems at RHIC and LHC energies.