Heavy Experiments Research Articles

A Neural-Network-Based Competition between Short-Lived Particle Candidates in the CBM Experiment at FAIR

Fast and efficient algorithms optimized for high performance computers are crucial for the real-time analysis of data in heavy-ion physics experiments. Furthermore, the application of neural networks and other machine learning techniques has become more popular in physics experiments over the last years. For that reason, a fast neural network package called ANN4FLES is developed in C++, which will be optimized to be used on a high performance computer farm for the future Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR, Darmstadt, Germany). This paper describes the first application of ANN4FLES used in the reconstruction chain of the CBM experiment to replace the existing particle competition between Ks-mesons and Λ-hyperons in the KF Particle Finder by a neural network based approach. The raw classification performance of the neural network reaches over 98% on the testing set. Furthermore, it is shown that the background noise was reduced by the neural network-based competition and therefore improved the quality of the physics analysis.

Neural-Network-Based Quark–Gluon Plasma Trigger for the CBM Experiment at FAIR

Algorithms optimized for high-performance computing, which ensure both speed and accuracy, are crucial for real-time data analysis in heavy-ion physics experiments. The application of neural networks and other machine learning methodologies, which are fast and have high accuracy, in physics experiments has become increasingly popular over recent years. This paper introduces a fast neural network package named ANN4FLES developed in C++, which has been optimized for use on a high-performance computing cluster for the future Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR, Darmstadt, Germany). The use of neural networks for classifying events during heavy-ion collisions in the CBM experiment is under investigation. This paper provides a detailed description of the application of ANN4FLES in identifying collisions where a quark–gluon plasma (QGP) was produced. The methodology detailed here will be used in the development of a QGP trigger for event selection within the First Level Event Selection (FLES) package for the CBM experiment. Fully-connected and convolutional neural networks have been created for the identification of events containing QGP, which are simulated with the Parton–Hadron–String Dynamics (PHSD) microscopic off-shell transport approach, for central Au + Au collisions at an energy of 31.2 A GeV. The results show that the convolutional neural network outperforms the fully-connected networks and achieves over 95% accuracy on the testing dataset.

Electromagnetic pulse protective shielding for digital x-ray detectors.

Laser-driven x-ray backlighting can be used to image fast dynamic processes like the propagation of laser-driven shock waves in matter. We demonstrate and evaluate the feasibility of operating the JUNGFRAU detector designed by PSI, a direct detecting x-ray detector, in environments with extreme electromagnetic pulses. The electromagnetic pulse-protective housing is specifically designed for this detector and optimized for pump-probe experiments at the Petawatt High-Energy Laser for Heavy Ion EXperiments (PHELIX) facility at the GSI Helmholtzzentrum für Schwerionenforschung GmbH. The beryllium x-ray entrance window of the protective housing has a high x-ray transmission of 94% at 8keV. Measurements have shown that the housing simultaneously provides a relative damping of the electromagnetic field on average higher than 1000 in the frequency range of 100MHz to 5GHz. The results demonstrate the feasibility of operating digital detectors in experiments where strong electromagnetic pulses are present.

The Fast Readout Unit for General Control and Data Acquisition in Heavy-Ion Experiments

The Fast Readout Unit for General Control and Data Acquisition in Heavy-Ion Experiments

Properties of quark-matter cores in massive hybrid stars

Using the constraints from astrophysical observations and heavy-ion experiments, we investigate the equation of state (EOS) of hybrid star matter and the properties of quark-matter cores in hybrid stars. The quark matter interactions in hybrid stars are described based on 3-flavor Nambu-Jona-Lasinio model with various vector and vector-isovector coupling constants. In this work, we find that the hybrid star matter EOS is more sensitive to the strength of the vector interaction, and the EOS becomes stiffer with increasing vector strength $R_V$. The vector-isovector interaction characterized by the coupling constant $R_{IV}$ make main contribution to the hadron-quark mixed phase. Meanwhile, we note that a step change of both the sound velocity and the polytropic index $\gamma$ occurs in the hadron-quark phase transition, and it is restored with the decrease of nucleon and lepton degrees of freedom in the high density quark phase. Although the coupling constants increase the hybrid star maximum mass up to $2.08M_{\odot}$, they also decrease the mass and radius of the quark core and the mixed core. With different quark coupling constants, we also find that the maximum mass and radius of the quark matter core in a stable hybrid star can reach $0.80M_{\odot}$ and 6.95 km, which are close to half of the maximum mass and radius of the complete star. However, properties of quark matter have no effect on the $M = 1.4M_{\odot}$ hybrid star as a result of no quark matter inner core, which can also be confirmed by the criterion of the polytropic index, and thus our results also indicate that the quark interactions have no effect on the tidal deformability $\Lambda_{1.4}$ of hybrid stars.

Determination of energy-dependent neutron backgrounds using shadow bars

Understanding the neutron background is essential for determining the neutron yield from nuclear reactions. The neutron backgrounds were determined for heavy-ion collision experiment using the shadow-bar method, where beams of 40,48Ca at 56, 140 MeV/u impinged on targets of 58,64Ni and 112,124Sn. In the analysis presented here, brass shadow bars are placed in front of organic liquid scintillator neutron detectors to determine the energy-dependent neutron background fractions. The measurement of neutron spectra with and without shadow bars is important to determine the neutron background more accurately. The neutron background, along with its sources and systematic uncertainties, are explored with a focus on the impact of background models and their dependence on neutron energy.

Probing the Hot QCD Matter via Quarkonia at the Next-Generation Heavy-Ion Experiment at LHC

Quarkonia represent one of the most valuable probes of the deconfined quark–gluon hot medium since the very first experimental studies with ultrarelativistic heavy-ion collisions. A significant step forward in characterizing the QCD matter via systematic studies of quarkonia production will be performed by the next-generation heavy-ion experiment ALICE 3, a successor of the ongoing ALICE experiment at the Large Hadron Collider. The new advanced detector of ALICE 3 will allow for exploring the production of S- and P-state quarkonia at high statistics, at low and moderate transverse momenta ranges. The performance of ALICE 3 for quarkonia measurements and the requirements for the detectors are discussed.

Seebeck and Nernst coefficients of a magnetized hot QCD medium with a number conserving kernel

We study the thermoelectric response of a hot and magnetized QCD medium created in the noncentral events at heavy-ion collider experiments. The collisional aspects of the medium have been embedded in the relativistic Boltzmann transport equation (RBTE) using the Bhatnagar-Gross-Krook (BGK) collision integral, which insures the particle number conservation, unlike the commonly used relaxation time approximation (RTA). We have incorporated the thermal medium effects in the guise of a quasiparticle model, where the interaction among the quarks and gluons is assimilated in the medium dependent masses of the quarks, which have been evaluated using imaginary-time formalism of thermal QCD with a background magnetic field. In the absence of $B$, the Seebeck coefficient for individual quark flavors gets slightly reduced in the BGK term in comparison to naive RTA, while it gets enhanced for the composite partonic medium. In the strong magnetic field ($B$), the BGK term enhances the Seebeck coefficient for the individual flavors, as well as that for the medium. The medium Seebeck coefficient rises with the strength of quark chemical potential ($\ensuremath{\mu}$) in the absence, as well as that in the strong $B$. We observe chirality dependence in the transport coefficients in the weak $B$ as the masses of chiral modes become nondegenerate. In the case of the $L$ modes, the BGK collision term causes a slight reduction in the Seebeck coefficient, while for $R$ modes both the collision integrals produce the same results. The Nernst coefficient gets reduced (enhanced) for $L$ ($R$) chiral modes in the BGK term.

Impact of Heavy-Ion Range on Single-Event Effects in Silicon Carbide Power Junction Barrier Schottky Diodes

Experimental heavy-ion responses of SiC Junction Barrier Schottky (JBS) diodes are presented. Measured data indicate that heavy ions having range less than the epitaxial thickness do not cause degradation or catastrophic failure, even with the device biased above the rated breakdown voltage. Measured data also indicate that when the heavy ions have range longer than the epitaxial layer thickness, the devices exhibit degradation as single-event leakage current (SELC), as well as catastrophic single-event burnout (SEB) at biases less than half of the rated breakdown voltage. Device failure was observed when irradiating with high-energy ions having long ranges, but not when irradiating with low-energy ions that stop in the epitaxial layer. Mechanisms of observed heavy-ion effects are examined with TCAD device modeling.

Analysis and Hardening of SEGR in Trench VDMOS with Termination Structure

Single-event gate-rupture (SEGR) in the trench vertical double-diffused power MOSFET (VDMOS) occurs at a critical bias voltage during heavy-ion experiments. Fault analysis demonstrates that the hot spot is located at the termination of the VDMOS, and the gate oxide in the termination region has been damaged. The SEGR-hardened termination with multiple implantation regions is proposed and simulated using the Sentaurus TCAD. The multiple implantation regions are introduced, leading to an increase in the distance between the gate oxide and the hole accumulation region, as well as a decrease in the resistivity of the hole conductive path. This approach is effective in reducing the electric field of the gate oxide to below the calculated critical field, and results in a lower electric field than the conventional termination.

Heavy quarkonia in a baryon asymmetric strongly magnetized hot quark matter

Recently there is a resurrection in the study of heavy quark bound states in a hot and baryonless matter with an ambient magnetic field but the matter produced at heavy-ion collider experiments is not perfectly baryonless, so we wish to explore the effect of small baryon asymmetry on the in-medium properties of the heavy quark bound states submerged in a strongly magnetized hot quark matter. Therefore, we have first given a revisit to the general covariant tensor structure of gluon self-energy in the above environment to compute the resummed propagator for gluons. This resummed propagator embodies the properties of medium, which gets translated into the (complex) potential between Q and Q¯ placed in the medium. We observe that the baryon asymmetry makes the real-part of potential slightly more attractive and weakens the imaginary-part. This opposing effects thus lead to the enhancement of binding energies and the reduction of thermal widths of QQ¯ ground states, respectively. Finally, the properties of quarkonia thus deciphered facilitate to compute the dissociation points of J/ψ and ϒ, which are found to have slightly larger values in the presence of baryon asymmetry. For example, J/ψ gets dissociated at 1.64Tc, 1.69Tc, and 1.75Tc, whereas ϒ is dissociated at 1.95Tc, 1.97Tc and 2.00Tc, for μ=0,60 and 100 MeV, respectively. This observation prevents early dissociation of quarkonia in the matter produced at ultrarelativistic heavy ion collisions with a small net baryon number, compared to the ideal baryonless matter.

Charge-dependent anisotropic flow in high-energy heavy-ion collisions from a relativistic resistive magneto-hydrodynamic expansion

We have investigated the charge-dependent anisotropic flow in high-energy heavy-ion collisions, using relativistic resistive magneto-hydrodynamics (RRMHD). We consider the optical Glauber model as an initial model of the quark-gluon plasma (QGP) and the solution of the Maxwell equations with source term of the charged particles in two colliding nuclei as initial electromagnetic fields. The RRMHD simulation is performed with these initial conditions in Au-Au and Cu-Au collisions at $\sqrt{s_{\mathrm{NN}}} = 200$ GeV. We have calculated the charge-odd contribution to the directed flow $\Delta v_1$ and elliptic flow $\Delta v_2$ in both collisions based on electric charge distributions as a consequence of RRMHD. Our results show that the $\Delta v_1$ and $\Delta v_2$ are approximately proportional to the electrical conductivity ($\sigma$) of the medium. In the $\sigma=0.023~\mathrm{fm}^{-1}$ case, our result of $\Delta v_1$ is consistent with STAR data in Au-Au collisions. Furthermore, in Cu-Au collisions, $\Delta v_1$ has a non-zero value at $\eta = 0$. We conclude that the charge-dependent anisotropic flow is a good probe to extract the electrical conductivity of the QGP medium in high-energy heavy-ion experiments.

Feasibility Studies for the Measurement of Open-Charm Mesons at ALICE-3 Using Decay Channels with Neutral Mesons and Photons in the Final State

ALICE-3 is being designed as a next-generation heavy-ion experiment to be operated at the high-luminosity Large Hadron Collider. With luminosities higher by a factor of fifty, ALICE-3 will be able to study5 properties of quark–gluon matter with probes and precision which were previously unavailable due to small cross sections, high background levels, and insufficient detector sensitivity. In particular, the properties of hot and dense QCD matter will be studied by measuring production cross sections, flow coefficients, azimuthal angular correlations and nuclear modification factors for open-charm hadrons. In this contribution, we present the results of feasibility studies for the measurement of ground and excited states of open-charm mesons in decay channels D0 → K− + π+ + π0, D*(2007)0 → D0 + γ and D*(2010)± → D0 + π± in pp, p-Pb and Pb-Pb collisions at LHC energies using the ALICE-3 experimental setup. We formulate the main requirements for the selection of particles and their combinations to ensure reliable signal extraction in a wide transverse momentum range and estimate the minimum size of the required data samples. The results obtained are also compared to previous findings for the open-charm measurements in different decay channels.

SEE and TID characterization of an 8 Gbps SST transmitter in a 28 nm bulk CMOS technology

Single-event effect (SEE) and total ionizing dose effect (TID) characterization of an 8 Gbps transmitter is investigated in the heavy ion and Co60 experiments. Source-series-terminated (SST) transmitter with T-coil and 3-tap feed-forward equalization (FFE) is adopted in the design and fabricated in a 28 nm commercial bulk CMOS technology. Single-event transient (SET) and single-event function interruption (SEFI) were observed in the heavy ion experiment, but the deterministic jitter (DJ) and random jitter (RJ) of the eye diagram were almost unchanged after 1.2 Mrad(Si) Co60 irradiation. The experimental results indicate that SEE is significant in the transmitter, and SET and SEFI need to be mitigated. While the TID effects are almost negligible, showing minor changes in the deterministic jitter. The most sensitive regions of SEEs are further identified by the pulsed laser experiment for the transmitter, which provides useful information for SEE-hardened design.

Unsupervised machine learning application to identify single-event transients (SETs) from noise events in MOSFET transistor ionizing radiation effects

This article presents a novel application of the k-means unsupervised machine learning algorithm to the problem of identifying single event transient (SET) events from noise during heavy-ion irradiation experiments of an electronic device. We explore the performance of the k-means algorithm by analyzing experimental datasets of SET events produced by several heavy-ions irradiations of a MOSFET transistor. Data anomalies and effectiveness of the chosen features (mean, standard deviation, skewness, and kurtosis) were investigated using the Isolation Forest and Random Forest algorithms, respectively. The results show a high capability of the K-means algorithm to identify SET events from noise using the first four statistical moments as features, allowing in the future the use of this method for in situ event detection and diagnosis without previous algorithm training or pre-analysis of the experimental data.

Versatile, compact chirped pulse amplifier pump system for ultrafast optical parametric amplifiers.

We report on the development of a pump system for ultrafast optical parametric amplifiers (uOPA) as an upgrade for the existing uOPA at the Petawatt High Energy Laser for heavy Ion eXperiments (PHELIX) and the new Petawatt ENergy-Efficient Laser for Optical Plasma Experiments (PEnELOPE). The system consists of a two-stage chirped pulse amplifier, centered around a high energy Yb:YAG regenerative amplifier that delivers 108 mJ uncompressed output energy, resulting in 92 mJ at 1030 nm after compression, pulse durations of 1.4 ps, a high beam quality of Mx/y2 = 1.02 / 1.16 and a relative energy stability of 0.35 %. A second harmonic generation (SHG) efficiency of up to 70 % is achievable and a maximum pulse energy of 43 mJ at 515 nm has been obtained, which is only limited by the damage threshold of the SHG crystal. A self-phase modulation stage makes this system a widely applicable, self-seedable pump module for uOPA without placing strong requirements on its seed oscillator.

Examination of promising reactions with Am241 and Cm244 targets for the synthesis of new superheavy elements within the dinuclear system model with a dynamical potential energy surface

Two actinide isotopes, $^{241}$Am and $^{244}$Cm, produced and chemically purified by the HFIR/REDC complex at ORNL are candidates for target materials of heavy-ion fusion reaction experiments for the synthesis of new superheavy elements (SHEs) with $Z>118$. In the framework of the dinuclear system model with a dynamical potential energy surface (DNS-DyPES model), we systematically study the $^{48}$Ca-induced reactions that have been applied to synthesize SHEs with $Z=112$--118, as well as the hot-fusion reactions with $^{241}$Am and $^{244}$Cm as targets which are promising for synthesizing new SHEs with $Z=119$--122. Detailed results including the maximal evaporation residue cross section and the optimal incident energy for each reaction are presented and discussed.

Measuring deformed neutron skin with free spectator nucleons in relativistic heavy-ion collisions

The neutron skin in deformed nuclei is generally not uniformly distributed but has an angular distribution, depending on both the spin-dependent nuclear interaction and the nuclear symmetry energy. To extract the information of the deformed neutron skin, we have explored the possibility of using free spectator nucleons in central tip-tip and body-body collisions at top RHIC energy with four typical deformed nuclei. The density distributions of neutrons and protons are consistently obtained from the Skyrme-Hartree-Fock-Bogolyubov calculation, and the angular distribution of the neutron skin can be varied by adjusting the strength of the nuclear spin-orbit coupling. With the information of spectator nucleons obtained based on a Monte-Carlo Glauber model, the free spectator nucleons are generated from a multifragmentation process. By investigating the results from different systems and with different collision configurations, we found that although it is difficult to probe the deformed neutron skin in 96Zr and 238U by their collisions, it is promising to extract the polar angular distributions of the neutron skin in 96Ru and 197Au by comparing the yield ratios of free spectator neutrons to protons in their central tip-tip and body-body collisions. The proposed observables can be measured by dedicated zero-degree calorimeters in heavy-ion collision experiments that have been carried out in recent years by RHIC.

Measuring the Speed of Sound Using Cumulants of Baryon Number

We show that the values of the first three cumulants of the baryon number distribution can be used to calculate the isothermal speed of sound and its logarithmic derivative with respect to the baryon number density. We discuss applications of this result to heavy-ion collision experiments and address possible challenges, including effects due to baryon number conservation, differences between proton and baryon cumulants, and the influence of finite number statistics on fluctuation observables in both experiment and hadronic transport simulations. In particular, we investigate the relation between quantities calculated in infinite, continuous matter and observables obtained in simulations using a finite number of particles.

Retraction Note: Constraining Neutron-Star Matter — Combination of heavy-ion experiments, astronomy and theory

This paper has been formally retracted because it has been accidentally published twice in the same volume. Request approved by the proceedings Editor and the Publisher on January 29, 2024.