Heavy-ion Data Research Articles

Energy dependence of ϕ(1020) production at mid-rapidity in pp collisions with ALICE at the LHC

Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects during the hadronization phase in heavy-ion collisions. Measurements in small collision systems provide a necessary baseline for heavy-ion data, help to tune pQCD inspired event generators and give insight into the search for the onset of collective effects. As the ϕ meson has a longer lifetime compared to other resonances, it is expected that its production would be much less affected by regeneration and re-scattering processes. We report on measurements of ϕ meson production in minimum bias pp collisions at different beam energies and as a function of charged particle multiplicity with the ALICE detector at the LHC. The results include the transverse momentum (pT) distributions of ϕ as well as the particle yield ratios. Finally, we have also studied the ϕ effective strangeness content by comparing our results to theoretical calculations.

QCD at high density: Equation of state for nuclear collisions and neutron stars

A unified chiral mean field approach is presented for QCD thermodynamics in a wide range of temperatures and densities. The model simultaneously gives a satisfactory description of lattice QCD thermodynamics and fulfills nuclear matter and astrophysical constraints. The resulting equation of state can be incorporated in relativistic fluid-dynamical simulations of heavy-ion collisions and neutron stars mergers. Access to different regions of the QCD phase diagram can be obtained in simulations of heavy-ion data and observations of neutron star mergers.

Qcrit-independent model method for proton SEU analysis

An improved model for device proton SEU cross section simulation is established totally based on heavy ion test data. The model is deduced from the assumption that an injecting heavy ion with a certain LET value will just generate a SEU cross section value corresponding to the LET value at the heavy ion test data. Based on the assumption, the model has special sub-volume collection efficiency, which makes the SEU cross section simulation result through the model independent of critical charge (Qcrit). The modeling method is verified by heavy ion and proton test data of Xilinx XC2V1000 and XC4VSX55 FPGA. The difference of proton SEU cross section between simulation result and test data is less than 69% above 40 MeV of proton.

Radiation Response of AlGaN-Channel HEMTs

We present heavy ion and proton data on AlGaN high-voltage HEMTs showing single event burnout (SEB), total ionizing dose, and displacement damage responses. These are the first such data for materials of this type. Two different designs of the epitaxial structure were tested for SEB. The default layout design showed burnout voltages that decreased rapidly with increasing LET, falling to about 25% of nominal breakdown voltage for ions with LET of about 34 MeV $\cdot $ cm2/mg for both structures. Samples of the device structure with lower AlN content were tested with varying gate–drain spacing and revealed an improved robustness to heavy ions, resulting in burnout voltages that did not decrease up to at least 33.9 MeV $\cdot $ cm2/mg. Failure analysis showed that there was consistently a point, location random, where gate and drain had been shorted. Oscilloscope traces of terminal voltages and currents during burnout events lend support to the hypothesis that burnout events begin with a heavy ion strike in the vulnerable region between gate and drain. This subsequently initiates a cascade of events resulting in damage that is largely manifested elsewhere in the device. This hypothesis also suggests a path for greatly improving the susceptibility to SEB as development of this technology goes forward. Testing with 2.5-MeV protons showed only minor changes in device characteristics.

Extrapolation Method of On-Orbit Soft Error Rates of EDAC SRAM Devices From Accelerator-Based Tests

Single-event upset sensitivity of 55- and 180-nm SRAM devices with error detection and correction (EDAC) exhibits obvious ion flux and scrubbing time dependence. On-orbit soft error rates (SERs) of EDAC SRAM devices are extrapolated from accelerator heavy-ion data and compared with rectangular parallelepiped-predicted SER, based on an experimentally verified formula. It is found that on-orbit SER of EDAC SRAM is contributed by both the memory array and the EDAC circuitry. This method can guide the optimization of EDAC SRAM hardening strategy and also the on-orbit hardness assurance.

GEANT4 simulation of nuclear interaction induced soft errors in digital nanoscale electronics: Interrelation between proton and heavy ion impacts

A simple and self-consistent approach has been proposed for simulation of the proton-induced soft error rate based on the heavy ion induced single event upset cross-section data and vice versa. The approach relies on the GEANT4 assisted Monte Carlo simulation of the secondary particle LET spectra produced by nuclear interactions. The method has been validated with the relevant in-flight soft error rate data for space protons and heavy ions. An approximate analytical relation is proposed and validated for a fast recalculation between two types of experimental data.

Effect of Transistor Variants on Single-Event Transients at the 14-/16-nm Bulk FinFET Technology Generation

Single-event transient (SET) data for the 14-/16-nm bulk finFET technology generation are presented and analyzed for variations in threshold voltage and number of fins in the transistor. The heavy-ion experimental data over a range of supply voltage allows for a comparison of the impact of drive current on the SET response of each transistor variant. The results show that the transistor drive current is a key factor for determining SET pulsewidths and cross sections for high linear energy transfer particle irradiation. Transistor variant data that result in matching transistor drive current show an excellent match for SET pulsewidths and cross sections.

A statistical analysis of two-dimensional patterns and its application to astrometry

Here we develop a general statistical procedure for the analysis of finite two-dimensional (2D) patterns inspired by the analysis of heavy-ion data. The method is used in the study of publicly available data obtained by the Gaia-ESA mission. We prove that the procedure can be sensitive to the limits of accuracy of measurement, and can also clearly identify the real physical effects on the large background of random distributions. As an example, the method confirms the presence of binary and ternary star systems in the studied data. At the same time, the possibility of the statistical detection of the gravitational microlensing effect is discussed.

Mechanisms of atmospheric neutron-induced single event upsets in nanometric SOI and bulk SRAM devices based on experiment-verified simulation tool**Project supported by the National Natural Science Foundation of China (Grant No. 11505033), the Science and Technology Research Project of Guangdong Province, China (Grant Nos. 2015B090901048 and 2017B090901068), and the Science and Technology Plan Project of Guangzhou, China (Grant No. 201707010186).

In this paper, a simulation tool named the neutron-induced single event effect predictive platform (NSEEP2) is proposed to reveal the mechanism of atmospheric neutron-induced single event effect (SEE) in an electronic device, based on heavy-ion data and Monte-Carlo neutron transport simulation. The detailed metallization architecture and sensitive volume topology of a nanometric static random access memory (SRAM) device can be considered to calculate the real-time soft error rate (RTSER) in the applied environment accurately. The validity of this tool is verified by real-time experimental results. In addition, based on the NSEEP2, RTSERs of 90 nm–32 nm silicon on insulator (SOI) and bulk SRAM device under various ambient conditions are predicted and analyzed to evaluate the neutron SEE sensitivity and reveal the underlying mechanism. It is found that as the feature size shrinks, the change trends of neutron SEE sensitivity of bulk and SOI technologies are opposite, which can be attributed to the different MBU performances. The RTSER of bulk technology is always 2.8–64 times higher than that of SOI technology, depending on the technology node, solar activity, and flight height.

Centrality determination of Au + Au collisions at 1.23A GeV with HADES

The centrality determination for Au+Au collisions at 1.23A GeV, as measured with HADES at the GSI-SIS18, is described. In order to extract collision geometry related quantities, such as the average impact parameter or number of participating nucleons, a Glauber Monte Carlo approach is employed. For the application of this model to collisions at this relatively low centre-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 2.42$ GeV special investigations were performed. As a result a well defined procedure to determine centrality classes for ongoing analyses of heavy-ion data is established.

Thermo-kinetic investigation of heavy metal ions adsorption onto lignin considering coupled adsorption–desorption mechanisms: Modeling and experimental validation

A coupled adsorption–desorption thermo-kinetic model is developed incorporating both adsorption and desorption reactions. A local pseudo-equilibrium condition at the interface of adsorbent and adsorbate bulk phases was used as isotherm equation which can even be applied for multi-pollutants scenarios. The developed model is then validated using collected experimental data of heavy metal ions (Pb, Cu, Cd, Zn, and Ni). Comparisons were made for a number of isotherm and kinetic models to examine the performance of the proposed model. The developed model revealed desirable accuracy and superiority over other models in predicting the adsorption behavior and can be used for other systems of concern. The model correlates the adsorption kinetic with an [Formula: see text] value of 0.9391 and desorption kinetic with an [Formula: see text] value of 0.9383. By application of the proposed model to any available adsorption datasets, the individual characteristics of adsorption and desorption can be determined.

Predicting Muon-Induced SEU Rates for a 28-nm SRAM Using Protons and Heavy Ions to Calibrate the Sensitive Volume Model

Muon-induced single-event upset cross sections are estimated for a 28-nm static random access memory (SRAM) using Monte Carlo simulations informed by ion test results. As an exercise in modeling with limited information, details of the 28-nm SRAM’s cell structure were not used (and not available) to inform choices of device model parameters such as sensitive volume dimensions and efficiencies. Instead, inferences were made based on heavy-ion and proton single event upset data. Volume dimensions were sufficiently small to resolve the charge collection profile resulting from highly localized low linear energy transfer particle strikes. Results are compared to muon experimental data taken at TRIUMF for validation. Rate predictions are made for the 28-nm SRAM using the calibrated model and compared to expected neutron rates. Muon-induced upset rates at sea level for both marginally reduced and significantly reduced electrical biases, as well as rates at 39 000 feet, are predicted to be significantly less than neutron rates in all these environments. This result is consistent with other authors’ efforts in similarly scaled bulk CMOS SRAMs, indicating that the modeling method used is reliable.

The Impact of Charge Collection Volume and Parasitic Capacitance on SEUs in SOI- and Bulk-FinFET D Flip-Flops

Measured single-event (SE) heavy-ion data for comparable silicon on insulator (SOI) and bulk silicon FinFET D flip-flop (DFF) designs demonstrate a notably greater difference between the SOI and bulk responses, which has commonly been observed. Data show greater than $30\times $ in SE upset (SEU) LET threshold and 3 orders of magnitude decrease in saturated SE cross section for SOI FinFETs when compared to bulk FinFETs. The difference in SEU threshold is shown to be due to the saturation of SE transient (SET) pulsewidths at values that are comparable to feedback-loop delays of DFF design in the SOI technology. The feedback-loop delays in FinFET technologies are significantly impacted by the inherent parasitic capacitance. For the bulk technology, SET pulsewidths do not saturate due to charge collection from the substrate region.

Statistical analysis of 2D patterns and its application to astrometry

A general statistical procedure for analysis of finite 2D patterns, inspired by analysis of heavy-ion data, is developed. The method is verified in the study of publicly available data obtained by the Gaia-ESA mission. We prove that the procedure can be sensitive to the limits of accuracy of measurement, but it can also clearly identify the real physical effects on the large background of random distributions. As an example, the method confirms presence of binary and ternary star systems in the studied data. At the same time the possibility of statistical detection of gravitational microlensing effect is discussed.

Angular power spectrum in publically released ALICE events

We study the particles emitted in the fireball following a Relativistic Heavy Ion Collision with the traditional angular analysis employed in cosmology and earth sciences, producing Mollweide plots of the number and pt distribution of a few actual, publically released ALICE-collaboration events and calculating their angular power spectrum. We also examine the angular spectrum of a simple two-particle correlation. While this may not be the optimal way of analyzing heavy ion data, our intention is to provide a one to one comparison to analysis in cosmology. With the limited statistics at hand, we do not find evidence for acoustic peaks but a decrease of Cl that is reminiscent of viscous attenuation, but subject to a strong effect from the rapidity acceptance which probably dominates (so we also subtract the m=0 component). As an exercise, we still extract a characteristic Silk damping length (proportional to the square root of the viscosity over entropy density ratio) to illustrate the method. The absence of acoustic-like peaks is also compatible with a crossover from the QGP to the hadron gas (because a surface tension at domain boundaries would effect a restoring force that could have driven acoustic oscillations). Presently we do not understand a depression of the l=6 multipole strength; perhaps ALICE could reexamine it with full statistics.

Flow harmonics from self-consistent particlization of a viscous fluid

The quantitative extraction of quark-gluon plasma (QGP) properties from heavy-ion data, such as its specific shear viscosity $\ensuremath{\eta}/s$, typically requires comparison to viscous hydrodynamic or ``hybrid'' hydrodynamics + transport simulations. In either case, one has to convert the fluid to hadrons, yet without additional theory input the conversion is ambiguous for dissipative fluids. Here, shear viscous phase-space corrections calculated using linearized transport theory are applied in Cooper-Frye freeze-out to quantify the effects on anisotropic flow coefficients ${v}_{n}({p}_{T})$ at the energies available at both the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider. Expanding upon our previous flow harmonics studies [D. Molnar and Z. Wolff, Phys. Rev. C 95, 024903 (2017); Z. Wolff and D. Molnar, J. Phys.: Conf. Ser. 535, 012020 (2014)], we calculate pion and proton ${v}_{2}({p}_{T})$, ${v}_{4}({p}_{T})$, and ${v}_{6}({p}_{T})$, but here we incorporate a hadron gas that is chemically frozen below a temperature of 175 MeV and use hypersurfaces from realistic viscous hydrodynamic simulations. For additive quark model cross sections and relative phase-space corrections with ${p}^{3/2}$ momentum dependence rather than the quadratic Grad form, we find at moderately high transverse momentum noticeably higher ${v}_{4}({p}_{T})$ and ${v}_{6}({p}_{T})$ for protons than for pions. In addition, the value of $\ensuremath{\eta}/s$ deduced from elliptic flow data differs by nearly 50% from the value extracted using the naive ``democratic Grad'' form of freeze-out distributions. To facilitate the use of the self-consistent viscous corrections calculated here in hydrodynamic and hybrid calculations, we also present convenient parametrizations of the corrections for the various hadron species.

Fission fragment yield distribution in the heavy-mass region from the Pu239 ( nth,f ) reaction

The fission fragment yield distribution has been measured in the $^{239}\mathrm{Pu}\left({n}_{\mathrm{th}},f\right)$ reaction in the mass region of $A=126$ to 150 using the Lohengrin recoil-mass spectrometer. Three independent experimental campaigns were performed, allowing a significant reduction of the uncertainties compared to evaluated nuclear data libraries. The long-standing discrepancy of around 10% for the relative yield of $A=134$ reported in JEF-2.2 and JEFF-3.1.1 data libraries is finally solved. Moreover, the measured mass distribution in thermal neutron-induced fission does not show any significant dip around the shell closure ($A=136$) as seen in heavy-ion fission data of $^{208}\mathrm{Pb}$($^{18}\mathrm{O}$, $f$) and $^{238}\mathrm{U}$($^{18}\mathrm{O}$, $f$) reactions. Lastly, comparisons between our experimental data and the predictions from Monte Carlo codes (gef and fifrelin) are presented and discussed.

Van der Waals Interactions in Hadron Resonance Gas: From Nuclear Matter to Lattice QCD.

An extension of the ideal hadron resonance gas (HRG) model is constructed which includes the attractive and repulsive van der Waals (VDW) interactions between baryons. This VDW-HRG model yields the nuclear liquid-gas transition at low temperatures and high baryon densities. The VDW parameters a and b are fixed by the ground state properties of nuclear matter, and the temperature dependence of various thermodynamic observables at zero chemical potential are calculated within the VDW-HRG model. Compared to the ideal HRG model, the inclusion of VDW interactions between baryons leads to a qualitatively different behavior of second and higher moments of fluctuations of conserved charges, in particular in the so-called crossover region T∼140-190 MeV. For many observables this behavior resembles closely the results obtained from lattice QCD simulations. This hadronic model also predicts nontrivial behavior of net-baryon fluctuations in the region of phase diagram probed by heavy-ion collision experiments. These results imply that VDW interactions play a crucial role in the thermodynamics of hadron gas. Thus, the commonly performed comparisons of the ideal HRG model with the lattice and heavy-ion data may lead to misconceptions and misleading conclusions.

Examination of the sensitivity of the thermal fits to heavy-ion hadron yield data to the modeling of the eigenvolume interactions

The hadron-resonance gas (HRG) model with the mass-proportional eigenvolume (EV) corrections is employed to fit the hadron yield data of the NA49 collaboration for central Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}} = 6.3, 7.6, 8.8, 12.3,$ and $17.3$ GeV, the hadron midrapidity yield data of the STAR collaboration for Au+Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV, and the hadron midrapidity yield data of the ALICE collaboration for Pb+Pb collisions at $\sqrt{s_{\rm NN}} = 2760$ GeV. At given bombarding energy, for a given set of radii, the EV HRG model fits do not just yield a single $T-\mu_B$ pair, but a whole range of $T-\mu_B$ pairs, each with similarly good fit quality. These pairs form a valley in the $T-\mu_B$ plane along a line of nearly constant entropy per baryon, $S/A$, which increases nearly linearly with bombarding energy $E_{\rm lab}$. The entropy per baryon values extracted from the data at the different energies are a robust observable: it is almost independent of the details of the modeling of the eigenvolume interactions and of the specific $T-\mu_B$ values obtained. These results show that the extraction of the chemical freeze-out temperature and chemical potential is extremely sensitive to the modeling of the short-range repulsion between the hadrons. This implies that the ideal point-particle HRG values are not unique. The wide range of the extracted $T$ and $\mu_B$ values suggested by the eigenvolume HRG fits, as well as the approximately constant $S/A$ at freeze-out, are consistent with a non-equilibrium scenario of continuous freeze-out, where hadrons can be chemically frozen-out throughout the extended space-time regions during the evolution of the system. Even when the EV HRG fits are restricted to modest temperatures suggested by lattice QCD, the strong systematic effects of EV interactions are observed.

Surprisingly large uncertainties in temperature extraction from thermal fits to hadron yield data at LHC

The conventional hadron-resonance gas (HRG) model with the Particle Data Group hadron input, full chemical equilibrium, and the hadron-type dependent eigenvolume interactions, is employed to fit the hadron midrapidity yield data of the ALICE collaboration for the most central Pb+Pb collisions. For the case of point-like hadrons, the well-known fit result is reproduced. However, the situation changes if the hadrons have different eigenvolumes. In the case when all the mesons are point-like while all the baryons have an effective hardcore radius of 0.3 fm, the temperature dependence of has a broad minimum in the temperature range of 155−210 MeV, with a fit quality comparable to the minimum in the point-particle case. A very similar result is obtained when only baryon–baryon eigenvolume interactions are considered, with the eigenvolume parameter taken from the previous fit to the ground state of nuclear matter. Finally, when we apply the eigenvolume corrections with a mass-proportional eigenvolume , fixed to a particular hardcore proton radius rp, we observe a second minimum in the temperature dependence of , located at significantly higher temperatures. For instance, at rp = 0.5 fm, the fit quality is better than in the point-particle HRG case in a very wide temperature range of 170−320 MeV, which creates uncertainty in the temperature determination from the fit to the data of 150 MeV. These results show that thermal fits to the heavy-ion hadron yield data are very sensitive to the modeling of the short-range repulsion eigenvolume between hadrons, and that the chemical freeze-out temperature can only be extracted from the LHC hadron yield data with sizable uncertainty.