Strangeness Measurements Research Articles

Strangeness production in Au+Au collisions at √SNN = 14.6, 19.6, and 200 GeV with the STAR experiment

Strangeness production has been suggested as a sensitive probe to the early dynamics of the deconfined matter created in heavy-ion collisions. In this presentation, we report new measurements of strange hadron (Ks0, Λ ¯Λ, Ξ, ¯Ξ, ϕ) production in Au+Au collisions at √SNN = 14.6, 19.6 GeV from STAR BESII and Ω(¯Ω) production in Au+Au collisions at √SNN = 200 GeV, including rapidity spectra, nuclear modification factors RCP and Ω-to-ϕ ratios. Benefiting from the iTPC upgrade, the strangeness measurements are now extended from mid-rapidity (|y| < 0.5, BES-I) to a larger rapidity range (|y| < 1.0).

Updates on Flavor Production from STAR

In these proceedings, some of the latest results from the STAR experiment on heavy, strange and light flavor hadron production and their flow are summarized. Over the years STAR has collected heavy ion collision data over a wide range of collision energies from √SNN = 200 GeV down to √SNN = 3 GeV. In high energy heavy ion collisions, heavy flavor hadrons are a valuable probe to study properties of the Quark Gluon Plasma (QGP) created in these collisions. Measurements of strange and light flavor hadrons at lower collision energies help understand the properties of the QCD matter at finite baryon densities and the phase structure of the QCD matter. Furthermore, the high statistics data collected at √SNN = 3 GeV allows measurements of hypernuclei production and flow, which can provide insights into the hyperon - nucleon interactions and hyperon contribution to the nuclear equation of state.

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.

The strangeness program at GlueX

The GlueX experiment located at Jefferson Lab studies the spectrum of hadrons using photoproduction on a LH2 target in a wide variety of final states. With its detector system capable of measuring neutral and charged final state particles over almost the full solid angle, and very good particle identification capabilities, GlueX can measure many different hadrons containing strangeness. A linearly polarized photon beam allows the measurement of polarization observables, which contain information about the production mechanisms involved in generating strange particles in photoproduction. In addition, GlueX can perform precise cross-section measurements, which help to study the spectrum of strange hadrons. In this presentation, the GlueX experiment is introduced, and recent progress of its strangeness program is discussed. We present recent results on Σ0 beam asymmetries, Λ(1520) spin-density matrix elements and ongoing studies of the Λ(1405) lineshape. We also present our recent progress on measurements of ΛΛ̅ and Ξ(∗) photoproduction. Also, future prospects for strangeness measurements at GlueX are discussed.

Recent highlights on open heavy-flavour production from ALICE

This work presents the latest highlights of open heavy-flavour measurements by the ALICE Collaboration in pp, p–Pb, and Pb–Pb collisions from Run 2 of the LHC. The nuclear modification and flow measurements of charm and beauty particles in Pb–Pb collisions are shown, as well as the latest measurements of non-prompt strange and non-strange D mesons, the multiplicity dependence of Λ+c baryon production, and measurements of heavier charmed baryon states including Ξc and Σ0,++c baryons.

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

Hadronic resonances, strange and multi-strange particle production in Xe-Xe and Pb-Pb collisions with ALICE at the LHC

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 sNN=5.44and5.02TeV, respectively, by the ALICE collaboration at the LHC. Particle ratios are presented as a function of multiplicity for Ks0, Λ, Ξ−, Ξ‾+, Ω−, Ω‾+, ρ(770)0, K*(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 systems are also presented.

Complete strangeness measurements in heavy-ion collisions

We discuss strangeness production in heavy-ion collisions within and around the energy range of the planned NICA facility. We describe the minimal statistical model, in which the total strangeness yield is fixed by the observed or calculated $K^+$ multiplicity. We show how the exact strangeness conservation can be taken into account on the event-by-event basis in such a model. We argue that from strange particle yields one can reveal information about the collision dynamics and about possible modifications of particle properties in medium. This can be best achieved if the complete strangeness measurement is performed, i.e. kaons, anti-kaons, hyperons and multistrange hyperons are registered in the same experimental setup. In particular the production of hadrons containing two and more strange quarks, like $\Xi$ and $\Omega$ baryons could be of interest.

An Experimental Review on Elliptic Flow of Strange and Multistrange Hadrons in Relativistic Heavy Ion Collisions

Strange hadrons, especially multistrange 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 multistrange hadrons in relativistic heavy ion collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC).

Strangeness Production at LHC energies as measured with ALICE

The main objective of the ALICE experiment is to study the properties and the evolution of the high-energy density system created in relativistic heavy-ion collisions at the LHC. For that purpose, ALICE has unique particle identification capabilities that enable the detection of weakly-decaying particles in the high-multiplicity environment created in lead-lead (Pb-Pb) collisions.In this work, we discuss the systematic measurements of strange and multi-strange hadrons performed by ALICE for proton-proton (pp), proton-lead (p-Pb) and Pb-Pb collisions. Production rates measured for p-Pb and Pb-Pb are compared to predictions from statistical hadronization models and to measurements performed in pp collisions. These data are also used for a brief discussion on strangeness enhancement.

Strangeness measurements with HADES

Strangeness measurements with HADES

The Entropic Uncertainty Principle for Decaying Systems and \U0001d49e\U0001d4ab violation

Employing an effective formalism for decaying system we are able to investigate Heisenberg's uncertainty relation for observables measured at accelerator facilities. In particular we investigate the neutral K-meson system and show that, firstly, due to the time evolution an uncertainty between strangeness measurements at different times is introduced and, secondly, due to the imbalance of matter and antimatter (\U0001d49e\U0001d4ab violation) an uncertainty in the evolution of the eigenstates of the effective Hamiltonian of the system. Consequently, the existence of \U0001d49e\U0001d4ab violation is linked to uncertainties of observables, i.e. the outcomes cannot be predicted even in principle to arbitrary precisions.

Strangeness measurements at LHC with ALICE

A review of the first results obtained on strangeness production in pp collisions at 0.9 and 7 TeV cm. energy with the ALICE detector at LHC will be presented. About 250,000 minimum bias events recorded in 2009 during the very first LHC runs at 0.9 TeV were analyzed. Preliminary results on central rapidity production of mesons containing strange quarks (K±, Ks0, ϕ(1020)) as well as single and double strange baryons are reported. More than 400 million minimum bias events have been collected up to now at 7 TeV by the ALICE experiment. Using only a fraction of the collected events the signals of many strange mesons (Ks0), hyperons and resonances (K*(892)0, ϕ(1020) and Σ(1385)) have been extracted. The ϕ(1020) invariant mass and the raw yield of as a function of transverse momentum will be shown.

Strangeness measurements at the HADES experiment

We report on high acceptance di-electron spectrometer (HADES) measurements of strange hadrons in the collision systems Ar(1.756 AGeV)+KCl and p+p at 3.5 GeV. Comparisons of K0s transverse mass and rapidity spectra to IQMD transport model calculations give a strong hint to a repulsive kaon–nucleon potential. The effect of the potential shows up strongest at very low transverse momenta, which were measured by HADES with high statistics. Statistical model fits show a fair agreement to the particle yields measured in the heavy-ion data, apart from the Ξ− yield which is off by more than an order of magnitude. Furthermore, first results from the Σ(1385)+ reconstruction in p+p reactions are presented, showing an excellent agreement with published data.

Strangeness production as a function of system size and energy at RHIC

In this paper we report on strangeness measurements in p+p, Au+Au and Cu+Cu collisions at different energies in the STAR detector at RHIC. We will focus on two momentum regions in particular: Firstly we look at strangeness enhancement in A+A collisions with respect to p+p. These yields are dominated by low transverse momentum. We compare the enhancements from Au+Au and Cu+Cu data at s√SNN = 200 GeV with Pb+Pb data at s√SNN = 17.2 GeV and find that the enhancement does not scale with Npart as expected, but rather scales with N1/3part, where Npart represents the number of participants; We then examine Λ/K0S ratios at intermediate transverse momentum in both Au+Au and Cu+Cu data where we find a greater enhancement in Cu+Cu compared to Au+Au data when we compare integrated ratios between 1.5 < pT < 3.5 GeV/c.

Pentaquark searches at HERA

Searches and measurements of strange and charmed pentaquarks by the H1 and ZEUS experiments at the HERA ep collider are presented. The analyses were performed in the central region of the laboratory frame of inclusive deep-inelastic scattering at a center-of-mass energy of 300-318 GeV with the full HERA I luminosity. Some conclusions and prospects for future measurements with HERA II are also presented.

What can we learn from the energy dependence of strangeness production at RHIC?

Measurements of strange and multi-strange particles with the STAR detector at center of mass energies per nucleon pair ( $\sqrt{s_{NN}}$ ) of 62.4 GeV and 200 GeV in ultra-relativistic Au+Au collisions at RHIC are presented. The results are discussed in order to get insight into chemical and dynamical properties of the created medium. The former are obtained by comparison of transverse momentum (pT) integrated observables such as yields and particle ratios to statistical models, while the latter use pT dependent quantities such as single particle spectra and elliptic flow measurements to challenge hydrodynamical model calculations and parameterizations. The discussion is orientated towards the energy dependence of these properties by confronting the results at the different RHIC energies but also with the lower SPS energies.

Strangeness measurements with the PHOBOS experiment

Recent results on identified particle production from the PHOBOS experiment at the relativistic heavy-ion collider (RHIC) are summarized. Transverse momentum spectra of pions, kaons, protons and antiprotons from Au+Au collisions at are presented close to mid-rapidity. Baryons have been found to have substantially harder transverse momentum spectra than mesons. The p/π+ ratio reaches unity at high pT, which fits into a smooth trend together with measurements at lower and higher collision energies. At very low transverse momenta no significant excess of particle yield was found, compared to extrapolations from higher pT. The net proton yield at mid-rapidity appears to be proportional to the number of participant nucleons in Au+Au collisions. The PHOBOS acceptance and mass resolution for the ϕ meson at low pT were studied in detail.

New strangeness measurements from STAR

A review of the recent STAR strangeness measurements from and p+p collisions at RHIC is presented. We explore the systematics of the mean transverse momentum with particle mass and event multiplicity. Identified particle mT spectra from Au+Au and p+p collisions are compared. We conclude with some discussion of the canonical suppression picture and its implications for strangeness enhancement.

Strangeness at RHIC: recent results from STAR

In this article I will summarize the intermediate- to high-momentum strangeness measurements from STAR since SQM03. Some of the results shown here have been previously published in the QM04 proceedings. The focus is on dynamic measurements such as resonance production, elliptic flow and momentum-dependent particle suppression in central AA collisions. Resonance scattering and regeneration in the hadronic phase between chemical and kinetic freeze-out might yield a scale for the lifetime of this phase. I will show differences in the baryon to meson behaviour at intermediate transverse momentum that can be attributed to quark coalescence in AA and the Cronin effect in dA collisions. The canonical yield suppression, which is unique to strange particles when comparing pp to AA collisions, affects the compatibility of the nuclear suppression factors RCP and RAA. Particle identified two particle correlations in AA collisions show that at high transverse momentum the measurement might be dependent on the species of the trigger particle.