SPS Energies Research Articles

The study of hadronic rescattering on K*0 resonance yield in baryon-rich QCD matter

Abstract The effect of hadronic rescattering on $K^{*0}$ resonance yield can be studied by measuring $K^{*0}/K$ ratio as a function of centrality or multiplicity. This study investigates how the size of the system and the chemical composition (meson-meson versus meson-baryon interaction) of the matter formed in heavy-ion collisions impact the process of hadronic rescattering. It is shown that existing calculation of $K^{*0}/K$ ratio, which considers the interaction of $K^{*0}$ and $K$ mesons with only light mesons in the hadronic medium (neglecting interactions with baryons), fails to explain the measured $K^{*0}/K$ ratio at RHIC BES energies. To understand the multiplicity dependence of the $K^{*0}/K$ ratio at RHIC BES and SPS energies ($\sqrt{s_{NN}}$ $<$ 20 GeV), the Ultra Relativistic Quantum Molecular Dynamics (UrQMD) model is employed. UrQMD calculations suggest that for a given multiplicity, $K^{*0}/K$ is more suppressed in Au+Au collision at $\sqrt{s_{NN}}$ =7.7 GeV, compared to that in $\sqrt{s_{NN}}$ =200 GeV. This is possibly because of formation different type of QCD medium at 200 GeV and 7.7 GeV, and change in interaction cross-section between hadrons with change in particle type and energy.

An appropriate statistical approach for non-equilibrium particle production

The incapability of thermal models to accurately reproduce the horn-like structure of the Kaon-to-pion ratio measured at AGS, SPS, and low RHIC energies, as well as confirmed in the beam energy scan program, has long been a persistent problem. This issue is believed to have arisen due to the inappropriate application of statistics, particularly the extensive additive Boltzmann–Gibbs (BG) statistics. The assumption that the analysis of particle production, a dynamic non-equilibrium process, should be primarily conducted using extensive BG or non-extensive Tsallis statistics, has proven to be an unsuccessful approach that has been followed for several decades. By employing generic (non)extensive statistics, two equivalence classes [Formula: see text] emerge, thereby undermining the validity of any ad hoc assumption. Consequently, the degree of (non)extensivity exhibited by the statistical ensemble is determined by its own characteristics. This encompasses both extensive BG statistics, characterized by [Formula: see text], and non-extensive Tsallis statistics, characterized by [Formula: see text]. The energy dependence of light-, [Formula: see text], and strange-quark occupation factor, [Formula: see text], suggests that the produced particles are most appropriately described as a non-equilibrium ensemble. This is evidenced by a remarkable non-monotonic behavior observed in the [Formula: see text] horn, for instance. On the other hand, the resulting equivalence classes [Formula: see text] are associated with a generic non-extensivity related to extended exponential and Lambert-[Formula: see text] exponentially generating distribution function, which evidently arise from free, short- and long-range correlations. The incorporation of generic non-extensive statistics into the hadron resonance gas model yields an impressive ability to rightfully reproduce the non-monotonic [Formula: see text] ratio.

A review on correlations among the multiplicities of charge particles at SPS, RHIC and LHC energies

A review on correlations among the multiplicities of charge particles at SPS, RHIC and LHC energies

Centrality dependence of multistrange baryon production in high-energy heavy-ion collisions

We consider the experimental data on the production of strange \Lambda^{\prime}Λ′s, and multistrange baryons (\XiΞ, \OmegaΩ), and antibaryons, on nuclear targets, at the energy region from SPS up to LHC, in the framework of the Quark-Gluon String Model. One remarkable result of this analysis is the significant dependence on the centrality of the collision of the experimental \overline{\Xi}^+/\overline{\Lambda}Ξ¯+/Λ¯ and \overline{\Omega}^+/\overline{\Lambda}Ω¯+/Λ¯ ratios in heavy-ion collisions, at SPS energies.

Simple Lévy α-Stable Model Analysis of Elastic pp and pp¯ Low-|t| Data from SPS to LHC Energies

A simple Lévy α-stable (SL) model is used to describe the data on elastic pp and pp¯ scattering at low-|t| from SPS energies up to LHC energies. The SL model is demonstrated to describe the data with a strong non-exponential feature in a statistically acceptable manner. The energy dependence of the parameters of the model is determined and analyzed. The Lévy α parameter of the model has an energy-independent value of 1.959 ± 0.002 following from the strong non-exponential behavior of the data. We strengthen the conclusion that the discrepancy between TOTEM and ATLAS elastic pp differential cross section measurements arises only in the normalization and not in the shape of the distribution of the data as a function of t. We find that the slope parameter has different values for pp and pp¯ elastic scattering at LHC energies. This may be the effect of the odderon exchange or the jump in the energy dependence of the slope parameter in the energy interval 3 GeV ≲s≲ 4 GeV.

Overview of the NA60+ experiment at the CERN SPS

NA60+ is a new experiment designed to study the phase diagram of the strongly interacting matter at CERN SPS energies, where the values of the baryochemical potential μB approximately range between 200 and 550 MeV. It is focused on precision studies of thermal dimuons, heavy quarks, and strangeness production in Pb–Pb collisions at center of mass energies ranging from 6 to 17 GeV per nucleon pair. In this paper the apparatus concept and the physics reach will be discussed.

Correction: String-based models analysis of proton, π± and K± production in central 7Be + 9Be collisions at CERN SPS energies

Correction: String-based models analysis of proton, π± and K± production in central 7Be + 9Be collisions at CERN SPS energies

Particle Ratios in a Multicomponent Nonideal Hadron Resonance Gas

We have considered formation of a multicomponent nonideal hot and dense gas of hadronic resonances in the ultrarelativistic heavy ion collisions. In the statistical thermal model approach, the equation of state (EoS) of the noninteracting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short-range repulsive part of the baryonic interaction. On the other hand, in the nonideal hadron resonance gas (NIHRG) model, we can incorporate these interactions using the van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper, we have attempted to understand the effect of such van der Waals-type interactions on the relative particle yields and also studied their dependences on the system’s thermal parameters, such as the temperature and baryon chemical potential μ B . We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the point-like, i.e., noninteracting IHRG model. It is found that the particle ratios get modified by incorporating the van der Waals-type interactions, especially in a baryon-rich system which is expected to be formed at lower RHIC energies, SPS energies, and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.

Limiting fragmentation in heavy-ion stopping?

Based on a nonequilibrium–statistical relativistic diffusion model that is consistent with quantum chromodynamics (QCD), we investigate baryon stopping in relativistic heavy-ion collisions at SPS, RHIC, and LHC energies. The net-proton rapidity distributions of the individual fragments exhibit a scaling behaviour similar to limiting fragmentation (LF) that is related to geometric scaling in the colour-glass condensate (CGC) and depends upon the gluon saturation scale. Forward-angle net-proton data at energies reached at the LHC are required to verify the prediction.

Results on system size dependence of strangeness production in the CERN SPS energy range from NA61/SHINE

NA61/SHINE is a multipurpose fixed-target facility at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE strong interactions program are to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. To reach these goals, hadron production measurements are performed in the form of a two-dimensional scan by varying collision energy and system size. The Collaboration has recently finished data acquisition for its original program on strong interactions, accumulating broad data samples on hadron production in various systems in the SPS energy range. In this contribution, the NA61/SHINE results on identified charged kaon and pion production in p+p, Be+Be and Ar+Sc collisions at the SPS energy range (√SNN = 5.1 - 17.3 GeV) are presented. The NA61/SHINE measurements of small and intermediate-mass ion collisions establish an interesting system size dependence, showing a rapid change of hadron production properties that starts when moving from Be+Be to Ar+Sc system. In particular, Ar+Sc is the smallest system for which a significant enhancement of K+/π+ ratio with respect to p+p collisions is observed. Obtained energy and system size dependence of the measured charged hadron multiplicities are compared with available world data and various theoretical models.

Investigation of dynamical pseudorapidity fluctuations using strongly intensive quantities on event-by-event basis in nucleus–nucleus interactions at CERN SPS energies

The event-by-event pseudorapidity and multiplicity fluctuations have been investigated for relativistic charged particles produced in [Formula: see text]O–AgBr at 60[Formula: see text]A[Formula: see text]GeV/c and 200[Formula: see text]A[Formula: see text]GeV/c, and [Formula: see text]S–AgBr at 200[Formula: see text]A[Formula: see text]GeV/c. The strongly intensive measures ([Formula: see text], [Formula: see text] and [Formula: see text]) have been studied to unravel the underlying dynamics of multiparticle production. The multiplicity and pseudorapidity dependence of these fluctuation measures has been investigated and significant deviations from the expected reference values of independent particle production model have been observed, implying the presence of genuine dynamical fluctuations and correlations in these interactions. These deviations are due to the correlated particle production and not the modifications in single-particle spectrum. The hadronic rescatterings present within the framework of a multi-phase transport (AMPT) model are found to have no significant impact on the behavior of these observables. Both default and string melting AMPT generally show the same qualitative behavior as that of the experimental data. However, the string melting AMPT exhibits slightly better quantitative agreement with the experimental results.

A comprehensive study of energy dependence of particle ratios in pp collisions from SPS to LHC energies

A comprehensive study has been performed to estimate the kaon to pion ($K^\pm$/$\pi^\pm$) yield ratio and total kaon to total pion ($K$/$\pi$) yield ratio as a function of centre of mass energy in $pp$ collisions at different energies i.e., \sqrts~= 6.3, 17.3, 62.4, 200, 900 GeV, 2.76 TeV, 7 TeV, 13 TeV and 14 TeV using EPOS1.99, EPOS-LHC, HIJING, QGSJETII-03 and Sibyll2.3d model simulations. NA61/SHINE experiment reported that $K^+/\pi^+$ yield ratio exhibits rapid changes at the SPS energy range. A horn like structure appears in $K/\pi$ yield ratio as a function of collision energy. Significant presence of horn in $K^+$/$\pi^+$ and $K^-$/$\pi^-$ yield ratio is suggested by experimental data at lower energies, which is confirmed by HIJING and EPOS-LHC models. A smooth increase in $K/\pi$ yield ratio is also seen at higher energies. The model simulations predict similar increase in yield ratio with increasing energies. On the basis of previous available measurements, we also study model predictions of these yield ratios at \sqrts~= 13 and 14 TeV where no data is available. Almost all models suggest a saturation in the yield ratio within statistical fluctuations at these energies except EPOS1.99 and QGSJETII-03 which slightly over predict the yield ratio. These systematic comparisons are helpful to apply possible constraints on various hadronic event generators to significantly improve the predictions of Standard Model physics as well as for the understanding of underlying physics mechanisms in high energy collisions.

Impact of Baryon anti-Baryon annihilation on hyperon ($$\Lambda $$, $$\bar{\Lambda }$$) production and apparent strangeness enhancement in $$\bar{\Lambda }/\bar{p}$$ in heavy ion collisions at SPS energy

Impact of Baryon anti-Baryon annihilation on hyperon ($$\Lambda $$, $$\bar{\Lambda }$$) production and apparent strangeness enhancement in $$\bar{\Lambda }/\bar{p}$$ in heavy ion collisions at SPS energy

String-based models analysis of proton, $$\pi ^{\pm }$$ and $$K^{\pm }$$ production in central $$^{7}\text {Be}+ ^{9}\text {Be}$$ collisions at CERN SPS energies

String-based models analysis of proton, $$\pi ^{\pm }$$ and $$K^{\pm }$$ production in central $$^{7}\text {Be}+ ^{9}\text {Be}$$ collisions at CERN SPS energies

Rapidity distribution within Landau hydrodynamical model and EPOS event-generator at AGS, SPS, and RHIC energies

The rapidity distribution of well-identified particles such as pions, kaons, protons and their antiparticles measured in AGS, SPS, and BRAHMS experiments (Au+Au collisions), at various energies spanning from higher energies = 200 down to lower energies 2 GeV, are compared with that obtained from huge statistical ensembles of 100, 000 events generated from the Cosmic Ray Monte Carlo (CRMC) EPOS event-generator. All these data are then compared to the results calculated in the frame work of Landau hydrodynamical model. The EPOS event-generator can describe the experimental data of the rapidity distribution for all mentioned particles at all considered energies. This leads to use the EPOS event-generator to produce the rapidity distribution for various particles at energies where there are no experimental data yet to compare with. Such a prediction might serve as an input for future experiments such as FAIR and NICA for instance. A successful comparison between the Landau hydrodynamical approach and the computational CRMC EPOS 1.99 model in describing the rapidity distribution for the mentioned particles is shown in the presence of the experimental data. We conclude that the Landau hydrodynamical model is capable of describing both experimental data and EPOS 1.99 event-generator results, and they are in a good agreement.

Multiplicity and Net-Charge Fluctuations in Ion $$\mathbf{+}$$ Ion Collisions at the SPS Energies

Multiplicity and Net-Charge Fluctuations in Ion $$\mathbf{+}$$ Ion Collisions at the SPS Energies

Transverse Momentum and Multiplicity Correlations in NICA and SPS Energy Range

Transverse Momentum and Multiplicity Correlations in NICA and SPS Energy Range

Effects of thermal string fragmentation in inelastic pp collisions at the CERN Super Proton Synchrotron with beam momenta from 20 to 158 GeV/ c

The proton stopping behavior in proton-proton ($\mathit{pp}$) collisions at beam momentum of 20, 31, 40, 80, 158 GeV/$c$ suggests that more physics mechanisms are at play than traditionally assumed in Monte Carlo event generators. It is shown that the thermal string fragmentation model of pythia 8.303 is able to provide a good description of the observables in inelastic $\mathit{pp}$ collisions such as the rapidity and transverse momentum spectra of protons, charged pions, and charged kaons at the whole CERN SPS energies.

On Asymptotic Regge Trajectories of Heavy Meson Resonances

We performed the analysis of the asymptotic behavior of Regge trajectories of nonstrange and strange mesons and found that thewidth of heavy hadrons for these trajectories cannot linearly depend on their mass. Such a finding clearly demonstrates that a widely spread belief on the linear mass dependence of the resonance width contradicts the linearity of Regge trajectories on theMandelstam variable s. Using the data on masses and widths for ρJ––, ωJ––, aJ++,, and fJ++ mesons with the spin values J ≤ 6 and for K*J mesons with J ≤ 5, we extracted the parameters of the asymptotically linear Regge trajectories predicted by the finite-width model of quark gluon bags. It is shown that the parameters obtained for the data sets B and D are consistent with the cross-over temperaturedetermined by the lattice QCD simulations at the vanishing baryonic density and with the kinetic freeze-out temperature of early hadronizing particles found in relativistic heavy ion collisions at and above the highest SPS energy. Comparing the resonance width of sets B and D evaluated at the masses of Z and W bosons, respectively, we discovered that the calculated width values match that of the gauge bosons. We argue that such matches provide us with indirect, but the first experimental evidence for the compositeness of Z and W bosons. Based on these findings, we assume that Z, W, and Higgs bosons have the Regge trajectories which are similar to the asymptotic trajectories of the studied mesons. The predictions for the masses and widths of the Regge partners of Z and W bosons and for the mass dependence of the widths of Higgs boson Regge partners along with the values for the mass and width of the scalar Higgs mesons are made as well.

Multiplicity fluctuations and correlations in $$^{16}$$O–AgBr collisions at AGS and SPS energies

Multiplicity fluctuations and correlations in $$^{16}$$O–AgBr collisions at AGS and SPS energies