Low-energy Data Research Articles

Photoproduction of heavy QCD axions in supernovae

Compact stellar objects like supernovae and neutron stars are believed to cool by emitting axions predominantly via bremsstrahlung (NN→NNa), pion conversion (π−p+→Na), and photoproduction (γN→Na). In this paper, we study new contributions to the photoproduction channel pertaining to axions. We first point out the impact of anomaly-induced unavoidable Wess-Zumino-Witten term ∝εμναβFμν∂αaωβ in the photoproduction of such axions. We then perform a complementary data-driven study where the rate of photoproduction can be estimated from low-energy pion photoproduction data. We found that for such heavier axions, i.e., ma∼O(100) MeV, photoproduction processes can be dominant compared to the usual emission processes. In addition, the spectrum of these particles emitted in the process is significantly harder than those originating from bremsstrahlung. Published by the American Physical Society 2024

Thermally tuned on-chip optical memory

Phase-change materials, known as Chalcogenide alloys, are a promising alternative to traditional random-access memory. They possess characteristics that are particularly beneficial for non-volatile storage applications. The features of the Phase change material Ge-Sb-Te alloy (GST) used for substrate-integrated optical memory include scaling, quick switching times, minimal switching energy, and exceptional thermal stability. The material has two tuneable states, amorphous and crystalline, with the amorphous layer for loading data optically. In contrast, the crystalline state holds the data longer without significant loss. The study designed a classic thermally tuned optical memory on a silicon substrate. It demonstrated a dependency of lattice structure on external voltage and revealed a large storage capacity for information in the form of an optical signal. The heat transport simulation utilized the Heat Transport (HEAT) solver of the Finite Element Eigenmode (FEEM) solver. At the same time, the optical response analysis involved the Finite Difference Time Domain (FDTD) solver of Lumerical. The proposed structure exhibits a memory-switching phenomenon when a temperature shift of about 60 °C from room temperature is induced by a change in the external voltage of 147 mV. These findings have substantial implications for non-volatile storage memory development, providing a potential solution for high-capacity, low-energy data storage.

First detailed calculation of atmospheric neutrino foregrounds to the diffuse supernova neutrino background in Super-Kamiokande

The diffuse supernova neutrino background (DSNB)—a probe of the core-collapse mechanism and the cosmic star-formation history—has not been detected, but its discovery may be imminent. A significant obstacle for DSNB detection in Super-Kamiokande (Super-K) is detector backgrounds, especially due to atmospheric neutrinos (more precisely, these are foregrounds), which are not sufficiently understood. We perform the first detailed theoretical calculations of these foregrounds in the range 16–90 MeV in detected electron energy, taking into account several physical and detector effects, quantifying uncertainties, and comparing our predictions to the 15.9 live time years of pre-gadolinium data from Super-K stages I–IV. We show that our modeling reasonably reproduces this low-energy data as well as the usual high-energy atmospheric-neutrino data. To accelerate progress on detecting the DSNB, we outline key actions to be taken in future theoretical and experimental work. In a forthcoming paper, we use our modeling to detail how low-energy atmospheric-neutrino events register in Super-K and suggest new cuts to reduce their impact. Published by the American Physical Society 2024

New insight into the hard X-ray emission influenced by the type I bursts observed by Insight-HXMT during the outburst of 4U 1636–536

Context. Thermonuclear bursts, also known as type I X-ray bursts, result from unstable nuclear burning of H/He accreted to the surface of neutron stars, lasting from tens to hundreds of seconds. Thermonuclear bursts have an important impact on accretion environments around the neutron stars, such as their disks and coronas, and are therefore a subject of extensive research. Thermonuclear bursts can be used as probes to gain a deeper understanding of the properties of their disks and coronas. Aims. By analyzing the data from Insight-HXMT and NICER, we can determine the evolution of the significance of the hard shortage in 4U 1636–536 with its spectral state, as well as the evolution of the fraction of deficit with energy. Additionally, we investigate the possible geometry and evolution of the corona in 4U 1636–536 by combining our findings with the results of spectral analysis. Methods. We extracted the light curves from the Insight-HXMT low-energy, medium-energy, and high-energy data and subtracted their pre-burst emission, which allowed us to estimate the significance of the hard shortages during the bursts. By fitting the spectra, the correlation between the persistent spectral parameters and the significance of the hard shortages could be established. The bursts were then grouped according to the spectral state in which they occurred, and the significance of the hard shortages was estimated. These in turn helped to investigate the evolution of the fraction of deficit with energy. Results. We find that during the soft state the significance of possible hard X-ray shortage in bursts is almost zero. However, in the hard state, some bursts exhibit significant shortages (> 3σ), while others do not. We attempt to establish a correlation between the significance of the hard X-ray shortage and the spectral parameters, but the data quality and the limited number of bursts prevent us from finding a strong correlation. For bursts with insignificant shortages in the soft state, the fraction of the deficit remains small. However, in the hard state the fraction of deficit for all bursts increases with energy, regardless of the significance of the shortage of individual bursts. For bursts during the hard state, we investigated the evolution of the fraction of deficit during the bursts by stacking the peaks and decays of the bursts, and find that as the flux of the bursts decreases, the energy corresponding to the maximum of the fraction of deficit becomes progressively higher. Conclusions. We explore the possible geometry and evolution of the corona suggested by the evolution of the fraction of deficit, which is obtained from the spectral and temporal analysis.

Dual Interactive Mode Human-Machine Interfaces Based on Triboelectric Nanogenerator and IGZO/In2O3 Heterojunction Synaptic Transistor.

Imitating human neural networks via bio-inspired electronics advances human-machine interfaces (HMI), overcoming von Neumann limitations and enabling efficient, low-energy data processing in the big data era. However, single-contact mode HMIs have inherent limitations in terms of their capabilities and performances, such as constrained adaptability to dynamic environments, and reduced cognitive processing capabilities. Here, a dual-interactive-mode HMI system based on a triboelectric nanogenerator (TENG) and heterojunction synaptic transistor (HJST) is proposed for both contact and non-contact applications. The TENG incorporates a poly-methyl meth-acrylate (PMMA)-NiCo2S4/S film, in which the NiCo2S4/S composite traps and blocks electrons to optimize charge generation and storage. The heterojunction structure, mitigates the Debye screening effect, thereby improving transistor characteristics and reliability. The integrated TENG-HJST system exhibits synaptic functions, including excitatory/inhibitory postsynaptic current (EPSC/IPSC), paired-pulse facilitation/depression (PPF/PPD), and synaptic plasticity, enabling emulation of neural behavior and advanced information processing. Moreover, neural morphology manipulation is demonstrated in practical tasks, such as controlling international chess games. By integrating the TENG-HJST device with a robotic hand, conscious artificial responses are generated, enhancing event accuracy. This breakthrough in dual-interactive-mode interfacing holds promise for HMI systems and neural prostheses.

K + N Elastic Scatterings for Estimation of the In-Medium Quark Condensate with Strange Quarks

Abstract We revisit the low-energy K+N elastic scatterings in the context of the in-medium quark condensate with strange quarks. The chiral ward identity connects the in-medium quark condensate to the soft limit value of the pseudoscalar correlation function evaluated in nuclear matter. The in-medium correlation function of the pseudoscalar fields with strangeness describes in-medium kaon propagation and is obtained by kaon–nucleon scattering amplitudes in the low-density approximation. We construct the kaon–nucleon scattering amplitudes in chiral perturbation theory up to the next-to-leading order and add some terms of the next-to-next-to-leading order with the strange quark mass to improve expansion of the strange quark sector. We also consider the effect of a possible broad resonance state around Plab = 600 MeV/c for I = 0 reported in the previous study. The low-energy constants are determined by existing K+N scattering data. We obtain good reproduction of the K+p scattering amplitude by chiral perturbation theory, while the description of the KN amplitude with I = 0 is not so satisfactory due to the lack of low-energy data. Performing analytic continuation of the scattering amplitudes obtained by chiral perturbation theory to the soft limit, we estimate the in-medium strange quark condensate.

AC-FPSK modulation for low-energy and low data rate optical wireless communications

This article proposes an amalgam of phase-shift keying and asymmetrically clipped frequency-shift keying (i.e., AC-FPSK) for low-energy/low-data rate optical wireless communications. We design a near-optimal, low-complexity harmonic receiver by analyzing the AC-FPSK time-domain (TD) and frequency-domain (FD) waveforms. The Euclidean distance analysis between AC-FPSK waveform pairs yields lower and upper bounds for theoretical bit error probability. Using numerical simulations, we present an exhaustive evaluation of the optimal cardinality of PSK, which illustrates the superiority of AC-FPSK. We show that AC-FPSK provides better energy efficiency versus spectral efficiency trade-off than state-of-the-art AC-FSK, direct current-FPSK, pulse amplitude modulation, and asymmetrically clipped optical orthogonal frequency division multiplexing. We also demonstrate that by making a suitable choice for the cardinality of PSK, the proposed 2-tap harmonic receiver for AC-FPSK can reach a similar complexity as the AC-FSK harmonic receiver.

Bootstrapping high-energy observables

In this paper, we set up the numerical S-matrix bootstrap by using the crossing symmetric dispersion relation (CSDR) to write down Roy equations for the partial waves. As a motivation behind examining the local version of the CSDR, we derive a new crossing symmetric, 3-channels-plus-contact-terms representation of the Virasoro-Shapiro amplitude in string theory that converges everywhere except at the poles. We then focus on gapped theories and give novel analytic and semi-analytic derivations of several bounds on low-energy data. We examine the high-energy behaviour of the experimentally measurable rho-parameter, introduced by Khuri and Kinoshita and defined as the ratio of the real to the imaginary part of the amplitude in the forward limit. Contrary to expectations, we find numerical evidence that there could be multiple changes in the sign of this ratio before it asymptotes at high energies. We compare our approach with other existing numerical methods and find agreement, with improvement in convergence.

Experimental study of photoneutron spectra from tantalum, tungsten, and bismuth targets for 16.6 MeV polarized photons

ABSTRACT The double differential cross-sections (DDXs) of photoneutron production via the photonuclear reaction on tantalum, tungsten, and bismuth for 16.6 MeV linearly polarized photon beam were measured using the time-of-flight method at the NewSUBARU-BL01 facility. Polarized photons were obtained by the laser Compton backscattering (LCS) technique. Two distinct components were observed on the spectra: the low-energy component up to 4 MeV and the high-energy above 4 MeV. The angular distribution of the low-energy component was isotropic, whereas the high-energy was distributed anisotropically and affected by the polarized incident photons. These distributions were similar to the previous studies on the 197Au target. The low-energy component's data were fitted with the Maxwellian function. According to the fitting results, the slopes of low-energy neutrons’ distribution for natTa and natW are similar and steeper than that of 209Bi. The anisotropy of the high-energy component can be expressed as a function of cos 2 Θ , where Θ is the angle between the direction of the photon polarization and neutron emission.The DDX energy integrations of the high-energy component were calculated and compared between the three targets. These integration values on natTa and natW were comparable and around 1.5 times smaller than those on 209Bi, regardless of the detection angles.

Constraining the chirally motivated [formula omitted] models with the πΣ photoproduction mass spectra

The paper presents a first time attempt on a combined fit of the K−p low-energy data and the πΣ photoproduction mass spectra, performed without fixing the meson-baryon rescattering amplitudes to a specific πΣ−K¯N coupled channels model obtained from fitting exclusively the K−p data. The formalism adopted to describe the photoproduction process is based on chiral perturbation theory and employs a limited number of free parameters. The achieved description of the photoproduction mass distributions is not quite satisfactory, leaving a room for improving the photo-kernel construction. Although the presented models tend to constrain the positions of the Λ(1405) poles it is difficult to draw any conclusions before accomplishing better data reproduction.

Recent Advances in Functional Materials for Optical Data Storage.

In the current data age, the fundamental research related to optical applications has been rapidly developed. Countless new-born materials equipped with distinct optical properties have been widely explored, exhibiting tremendous values in practical applications. The optical data storage technique is one of the most significant topics of the optical applications, which is considered as the prominent solution for conquering the challenge of the explosive increase in mass data, to achieve the long-life, low-energy, and super high-capacity data storage. On this basis, our review outlines the representative reports for mainly introducing the functional systems based on the newly established materials applied in the optical storage field. According to the material categories, the representative functional systems are divided into rare-earth doped nanoparticles, graphene, and diarylethene. In terms of the difference of structural features and delicate properties among the three materials, the application in optical storage is comprehensively illustrated in the review. Meanwhile, the potential opportunities and critical challenges of optical storage are also discussed in detail.

High-performance real-world optical computing trained by in situ gradient-based model-free optimization.

Optical computing systems provide high-speed and low-energy data processing but face deficiencies in computationally demanding training and simulation-to-reality gaps. We propose a gradient-based model-free optimization (G-MFO) method based on a Monte Carlo gradient estimation algorithm for computationally efficient in situ training of optical computing systems. This approach treats an optical computing system as a black box and back-propagates the loss directly to the optical computing weights' probability distributions, circumventing the need for a computationally heavy and biased system simulation. Our experiments on diffractive optical computing systems show that G-MFO outperforms hybrid training on the MNIST and FMNIST datasets. Furthermore, we demonstrate image-free and high-speed classification of cells from their marker-free phase maps. Our method's model-free and high-performance nature, combined with its low demand for computational resources, paves the way for accelerating the transition of optical computing from laboratory demonstrations to practical, real-world applications.

Bagging ensemble mean-shift Gaussian kernelized clustering based D2D connectivity enabled communication for 5G networks

The advent of the fifth-generation (5 G) network integrates a spectrum of powerful technologies. Among these, Device-to-Device (D2D) communication stands as a focal point in research due to its expansive array of applications. Within the realm of 5 G, D2D communication offers support for high data rates and ultra-reliable, low-latency communications. While machine learning-based approaches have been devised to facilitate D2D communication in 5 G, ensuring robust connectivity and optimal network throughput remains a persisting challenge. Therefore, the bagging ensemble mean-shift Gaussian kernelized clustering-based D2D Connectivity (BEMSGKC-DC) algorithm is designed to enhance device-to-device communication in 5 G Cellular Networks with better packet delivery ratio and throughput. The proposed BEMSGKC-DC algorithm is proposed to enable massive device connectivity while improving the overall network performance. This can be achieved by employing bootstrap aggregating clustering where it clusters the devices via forming a set of base clusters i.e., Mean-Shift Gaussian kernelized clustering algorithm. To further enhance the performance of the algorithm, this paper also computes the resources of the devices in the clustering process using the Gaussian kernel function. All the weak cluster outcomes are merged to acquire the final clustering output with lower error. Through the resultant clustering of the device, the connectivity between D2D is ensured and thereby improves the data communication in the 5 G network. The result demonstrates that the BEMSGKC-DC algorithm optimizes the connectivity with lower energy, latency, and higher data delivery ratio and packet loss rate than the conventional algorithms.

Performance modeling and advanced exergy analysis for low-energy consumption data center with waste heat recovery, flexible cooling and hydrogen energy

Performance modeling and advanced exergy analysis for low-energy consumption data center with waste heat recovery, flexible cooling and hydrogen energy

FER-Restricted AUV-Relaying Data Collection in Underwater Acoustic Sensor Networks

Relaying is an effective method to achieve reliable and timely data collection, which is one of the most important parts of underwater acoustic sensor networks (UASNs). Considering that the relay position determines the reliability of relay communication, we study the problem of relay placement and place an autonomous underwater vehicle (AUV) to mobile relay data transmission and realize the reliable, low-latency, and low-energy data collection in UASNs. First, we formulate the relay positions that can meet a certain frame error rate (FER) requirement as the FER-restricted area (FRA), and approximate FRA with a three-dimensional geometry formula. The problem of reliable and timely data collection becomes planning a short AUV relaying trajectory under the FRA constraint. To this end, we propose a nearest-community (N-C) trajectory planning algorithm to design the AUV relay trajectory. A member grouping method and the necessity of position (NoP) concept are proposed to further reduce the relay positions and trajectory length of the AUV. Simulation results verify that the approximate FRA is more than 90% consistent with the real FRA and show that the N-C using NoP-based member grouping can successfully receive more packets per minute and consume fewer sensors’ energy than other algorithms.

Memristive behavior of UiO-66 metal-organic framework single crystal

Metal–organic frameworks (MOFs) have recently emerged as a new class of scalable and low energy consumptive materials for microelectronic applications. Here, we experimentally extend the list of MOFs with memristive behavior for electronic data storage. Using 15 µm single crystals of UiO-66 located in 10 µm gap between Au contacts, we demonstrate an electronic set/reset process upon 15 kV cm−1 of an electric field strength under normal conditions. Such low-energy data recording together with an endurance of more than 7 cycles for set/reset opens up prospects for the design of MOF-based electronic and opto-electronic devices.

Studying the impact of deuteron non-elastic breakup on 93Zr + d reaction cross sections measured at 28 MeV/nucleon

Abstract The deuteron is a loosely bound system that can easily break up into its constituent proton and neutron whilst in the presence of Coulomb and nuclear fields. Previous experimental studies have shown that this breakup process has a significant impact on residual-nucleus production from deuteron bombardment in the high-energy range of 50–210 MeV/nucleon. However, there remains a lack of cross-section data at energies below 50 MeV/nucleon. The current study determined 93Zr + d reaction cross sections under inverse kinematics at approximately 28 MeV/nucleon using the BigRIPS separator, OEDO beamline, and SHARAQ spectrometer. Cross sections from this research were compared with previous measurements and theoretical calculations. The experimental results show a large enhancement of the production cross sections of residual nuclei, especially those produced from a small number of particle emissions, compared to the proton-induced reaction data at similar bombarding energy. The DEURACS calculation, which quantitatively takes deuteron-breakup effects into account, reproduces the data well. As a long-lived fission product, 93Zr remains a challenge for nuclear-waste disposal and treatment. This study’s low-energy data may assist future consideration of nuclear-waste treatment facilities, where 93Zr + d may feasibly transmute the waste into short-lived/stable nuclei.

Theoretical cross sections for electron collisions relevant for ammonia discharges part 1: NH3, NH2, and NH

Besides being the worlds’ most important fertilizer precursor, ammonia could play an important role as hydrogen carrier in a decarbonized future. The efficient production and decomposition (or cracking) of ammonia are essential to this end. An electricity-driven technology of interest for both these processes are non-thermal plasmas. Plasma processes have the advantage of activating—even inert—molecules and initiating chemical reactions through electron collisions, rather than through conventional heating. However, a complete set of low-energy cross section data is not available for the electron collisions with ammonia (NH3) and its radicals, amidogen (NH2) and imidogen (NH). Here, we used the ab initio R-matrix method to determine theoretical cross sections for the low-energy electron collision processes with NH3, NH2, and NH. Additionally, we explored the contribution of the different processes towards dissociation (especially from electronic excited states). Where possible, we compared our theoretical cross section data with experimental data and/or previous recommendations. Lastly, our own recommended cross section data for the electron collisions are presented. Use of this complete set of electron collision data should contribute to a more accurate description of and better insights into the plasma-chemical kinetics behind plasma-assisted ammonia production and decomposition processes.

Higgs inflation at the pole

We propose a novel possibility for Higgs inflation where the perturbative unitarity below the Planck scale is ensured by construction and the successful predictions for inflation are accommodated. The conformal gravity coupling for the Higgs field leads to the proximity of the effective Planck mass to zero in the Jordan frame during inflation, corresponding to a pole in the Higgs kinetic term in the Einstein frame. Requiring the Higgs potential to vanish at the conformal pole in the effective theory in the Jordan frame, we make a robust prediction of the successful Higgs inflation. For a successful Higgs inflation at the pole, we take the running quartic coupling for the Higgs field to be small enough at the inflation scale, being consistent with the low-energy data, but we need a nontrivial extension of the SM with extra scalar or gauge fields in order to keep the running Higgs quartic coupling small during inflation. Performing the perturbative analysis of reheating with the known couplings of the SM particles to the Higgs boson, we show that a concrete realization of the Higgs pole inflation can be pinned down by the reheating processes with a general equation of state for the Higgs inflaton. We illustrate some extensions of the simple Higgs pole inflation to the general pole expansions, the running Higgs quartic coupling in the Standard Model and its extension with a singlet scalar field, a supergravity embedding of the Higgs pole inflation.

Neutrino flares of radio blazars observed from TeV to PeV

ABSTRACT Radio blazars have been linked both to individual high-energy neutrino events and to excesses in likelihood sky maps constructed from lower-energy neutrino data. However, the exact mechanism by which neutrinos are produced in these sources is still unknown. Here, we demonstrate that IceCube neutrinos with energies over 200 TeV, which were previously associated with bright radio blazars, are significantly more likely to be accompanied by flares of lower-energy events, compared to those lacking blazar counterparts. The parsec-scale core radio flux density of blazars, positioned within the error regions of energetic events, is strongly correlated with the likelihood of a day-scale lower-energy neutrino flare in directional and temporal coincidence with the high-energy event, reported by IceCube. The probability of a chance correlation is 3.6 × 10−4. This confirms the neutrino-blazar connection in a new and independent way, and provides valuable clues to understanding the origin of astrophysical neutrinos.