Decay Products Research Articles

PASCL: supervised contrastive learning with perturbative augmentation for particle decay reconstruction

Abstract In high-energy physics, particles produced in collision events decay in a format of a hierarchical tree structure, where only the final decay products can be observed using detectors. However, the large combinatorial space of possible tree structures makes it challenging to recover the actual decay process given a set of final particles. To better analyse the hierarchical tree structure, we propose a graph-based deep learning model to infer the tree structure to reconstruct collision events. In particular, we use a compact matrix representation termed as lowest common ancestor generations matrix, to encode the particle decay tree structure. Then, we introduce a perturbative augmentation technique applied to node features, aiming to mimic experimental uncertainties and increase data diversity. We further propose a supervised graph contrastive learning algorithm to utilize the information of inter-particle relations from multiple decay processes. Extensive experiments show that our proposed supervised graph contrastive learning with perturbative augmentation method outperforms state-of-the-art baseline models on an existing physics-based dataset, significantly improving the reconstruction accuracy. This method provides a more effective training strategy for models with the same parameters and makes way for more accurate and efficient high-energy particle physics data analysis.

Mathematical Modeling Unveils Optimization Strategies for Targeted Radionuclide Therapy of Blood Cancers.

Targeted radionuclide therapy is based on injections of cancer-specific molecules conjugated with radioactive nuclides. Despite the specificity of this treatment, it is not devoid of side-effects limiting its use and is especially harmful for rapidly proliferating organs well perfused by blood, like bone marrow. Optimization of radioconjugates administration accounting for toxicity constraints can increase treatment efficacy. Based on our experiments on disseminated multiple myeloma mouse model treated by 225Ac-DOTA-daratumumab, we developed a mathematical model which investigation highlighted the following principles for optimization of targeted radionuclide therapy. 1) Nuclide to antibody ratio importance. The density of radioconjugates on cancer cells determines the density of radiation energy deposited in them. Low labeling ratio as well as accumulation of unlabeled antibodies and antibodies attached to decay products in the bloodstream can mitigate cancer radiation damage due to excessive occupation of specific receptors by antibodies devoid of radioactive nuclides. 2) Cancer binding capacity-based dosing. The total number of specific receptors on cancer cells is a critical factor for treatment optimization, which estimation may allow increasing treatment efficacy close to its theoretical limit. Injection of doses significantly exceeding cancer binding capacity should be avoided since radioconjugates remaining in the bloodstream have negligible efficacy to toxicity ratio. 3) Particle range-guided multi-dosing. The use of short-range particle emitters and high-affinity antibodies can allow for robust treatment optimization via initial saturation of cancer binding capacity, enabling redistribution of further injected radioconjugates and deposited dose towards still viable cells that continue expressing specific receptors.

U and Th zonation in apatite observed by synchrotron X-ray fluorescence tomography and implications for the (U–Th) ∕ He system

Abstract. Synchrotron X-ray fluorescence microtomography can non-destructively image the three-dimensional distribution of several trace elements in whole apatite crystals at the resolution of 1 µm3. This allows for precise determination of the physical geometry of a crystal and the quantification of the relative abundance of the radioactive parent nuclides uranium and thorium with high fidelity. We use these data to develop a more precise alpha ejection correction for (U–Th) / He thermochronology and high-resolution models of apatite crystals that are the foundation for a new generation of three-dimensional diffusion modeling. The application of synchrotron radiation to non-destructive imaging of minerals used for geochronology sheds light on causes of long-standing unresolved problems in the field that are rooted in previously unmeasurable parent nuclide zonation, especially the pervasive overdispersion of single-crystal ages.

Ultra-high frequency gravitational waves from scattering, Bremsstrahlung and decay during reheating

We investigate ultra-high frequency gravitational waves (GWs) from gravitons generated during inflationary reheating. Specifically, we study inflaton scattering with its decay product, where the couplings involved in this 2 → 2 scattering are the same as those in the 1 → 3 graviton Bremsstrahlung process. We compute the graviton production rate via such 2 → 2 scattering. Additionally, we compare the resulting GW spectrum with that from Bremsstrahlung as well as that from pure 2 → 2 inflaton scatterings. For completeness, the GW spectrum from graviton pair production through one-loop induced 1 → 2 inflaton decay is also analyzed. With a systematic comparison among the four sources of GWs, we find that 2 → 2 inflaton scattering with its decay product can dominate over Bremsstrahlung if the reheating temperature is larger than the inflaton mass. Pure inflaton 2 → 2 scattering is typically subdominant compared to Bremsstrahlung except in the high-frequency tail. The contribution from one-loop induced 1 → 2 inflaton decay is shown to be suppressed compared to Bremsstrahlung and pure inflaton 2 → 2 scattering.

Determination of the Radon Progeny Activity Size Distribution in Laboratory Conditions

Knowledge of the active size distribution of radon daughters is one of the main parameters for determining the effective dose from inhalation of short-term radon decay products. However, this parameter is crucial for accurately determining an effective dose; there are currently very limited possibilities for determining it. This paper describes the laboratory validation of a method for determining the activity size distribution of radon decay products using the Dekati ELPI+ cascade impactor and the Graded Screen Array Diffusion Battery (GSA DB). Using nuclear track detectors placed on individual impaction plates of the cascade impactor, the equivalent equilibrium activity concentration of individual size classes can be determined in the range from 17 nm to 10 μm. A diffusion battery was used to detect smaller particles in the unattached fraction area. The presented method can further refine the knowledge of the activity size distribution of radon decay products in different types of workplace atmospheres. Workplaces with higher radon concentrations differ significantly in the size distribution of aerosol particles, radon activity concentration, and equilibrium equivalent activity concentration.

Features, reasons, and significance of radon and thoron attributable radiological dose in the indoor environment

Humans receive around 50% of natural radiation dose due to 222Rn (radon), 220Rn (thoron) and their decay products. Several field campaigns measuring these gases and the decay products in different regions of India have been conducted in the recent past. Some of these studies measured indoor activity concentration and/or dose due to these gases and the associated decay products. This work compares the fraction of 222Rn and decay products and 220Rn and decay products in inhalation dose for 10 studies conducted in Uttarakhand state. It is seen that AEDT (annual effective dose due to 220Rn and decay products) for these regions varies between 21 and 48% and it is significantly higher than the averaged worldwide reference value of 6%. Based on elaborative measurements performed in the Bageshwar district (present work), Almora and Nainital districts (our previous campaigns); the reasons for this high value have been explored. It was observed that a higher source term for mud houses could be the main reason for the high AEDT range. Interestingly, preliminary analysis revealed that the fraction is higher for the dwellings situated at higher altitudes thus indicating the role of the unavailability of modern building construction materials at remote locations. The study highlights the significant contribution of thoron in the Indian Himalayas.

The Ways of Forming and the Erosion/Decay/Aging of Bioapatites in the Context of the Reversibility of Apatites

This study primarily focused on the acid erosion of enamel and dentin. A detailed examination of the X-ray diffraction data proves that the products of the acid-caused decay of enamel belong to the family of isomorphic bioapatites, especially calcium-deficient hydroxyapatites. They are on a trajectory towards less and less crystallized substances. The increase in Bragg’s parameter d and the decrease in the energy necessary for the changes were coupled with variability in the pH. This was valid for the corrosive action of acid solutions with a pH greater than 3.5. When the processes of natural tooth aging were studied by X-ray diffraction, a clear similarity to the processes of the erosion of teeth was revealed. Scarce data on osteoporotic bones seemed to confirm the conclusions derived for teeth. The data concerning the bioapatite decays were confronted with the cycles of apatite synthesis/decay. The chemical studies, mainly concerning the Ca/P ratio in relation to the pH range of durability of popular compounds engaged in the synthesis/decay of apatites, suggested that the process of the formation of erosion under the influence of acids was much inverted in relation to the process of the formation of apatites, starting from brushite up to apatite, in an alkaline environment. Our simulations showed the shift between the family of bioapatites versus the family of apatites concerning the pH of the reaction environment. The detailed model stoichiometric equations associated with the particular stages of relevant processes were derived. The synthesis processes were alkalization reactions coupled with dehydration. The erosion processes were acid hydrolysis reactions. Formally, the alkalization of the environment during apatite synthesis is presented by introducing Ca(OH)2 to stoichiometric equations.

Investigation on preparation and properties of gel type 188W/188Re generator

As one of the most important integrated nuclides for diagnosis and treatment in recent years, rhenium-188 (188Re) has a broad scope in the clinical application. Due to the specific properties of such radionuclide, it was mainly provided by the chromatographic 188W-188Re generators. There is no doubt that the application of 188Re in the treatment of various diseases depended on the development of 188W-188Re generator. Considering the high standards of such technology on radioactive activity of 188W and impurity content, a 188W-188Re generator filled with the zirconium tungstate gel has been prepared in this work. The effects of molar ratio of chemical agents, pH, reaction temperature, drying methods, rinsing methods and other conditions on the synthesis of gel particles have been studied. Furthermore, a variety of characterization techniques were used to observe the macro-/micro-morphology and chemical structure of gel particles. It can be concluded that vacuum freeze-dried method could significantly increase the specific surface area, pore size and tungsten content of gel particle. In order to decrease the content of 188W in the elute, a handful of acidic alumina was filled in the bottom of our 188W-188Re generator, an elution and purification integrated-generator was formed. During the first five processes, the nuclear purity of 188Re solution was above 99.99%, the radiochemical purity was approximately 99.5%, the pH value was 5.0–7.0 and the average elution efficiency reached up to 82.7%. In addition, the leakage rate of 188W was low as 1.60 × 10−6, and the peak of elute curve was located at 2 mL without the trailing phenomenon. This work lays a solid foundation for the domestic demand of daughter nuclide 188Re, further makes an outstanding contribution to the application of the radiation therapy technology and the protection of people's health.

Search for the Exclusive W Boson Hadronic Decays W±→π±γ , W±→K±γ and W±→ρ±γ with the ATLAS Detector

A search for the exclusive hadronic decays W±→π±γ, W±→K±γ, and W±→ρ±γ is performed using up to 140 fb−1 of proton-proton collisions recorded with the ATLAS detector at a center-of-mass energy of s=13 TeV. If observed, these rare processes would provide a unique test bench for the quantum chromodynamics factorization formalism used to calculate cross sections at colliders. Additionally, at future colliders, these decays could offer a new way to measure the W boson mass through fully reconstructed decay products. The search results in the most stringent upper limits to date on the branching fractions B(W±→π±γ)<1.9×10−6, B(W±→K±γ)<1.7×10−6, B(W±→ρ±γ)<5.2×10−6 at 95% confidence level. © 2024 CERN, for the ATLAS Collaboration 2024 CERN

Simulation and Performance of 99Mo/99mTc Radioisotope Separation by Modified Extraction Method

Abstract Technetium-99m (99mTc) is a nuclide in nuclear medicine, commonly derived as a decay product from molybdenum-99 (99Mo). Unfortunately, Japan and Indonesia rely entirely on imports for their 99Mo/99mTc supply. This study aims to determine the distribution coefficient (Kd) for the 99Mo/99mTc production process and assess the efficiency of Methyl Ethyl Ketone (MEK) as a solvent in the extraction process. The method Initial tests using Rhenium (Re) as a substitute for 99mTc, conducted in collaboration with the Japan Atomic Energy Agency (JAEA), revealed optimal conditions: a standing time of 5 to 15 minutes, a mixing time of 3 minutes with a motor speed of 250 rpm, and a MEK volume exceeding 20 ml. These conditions yielded a Re extraction efficiency exceeding 85.14%, with a Re elution yield of up to 98.73%. These findings served as a database for experiments involving 99Mo/99mTc conducted at the National Research and Innovation Agency (BRIN). In hot experiments, the 99mTc recovery rate through MEK exceeded 100%, while the elution process achieved a recovery rate of 97.81%. Through simulation and facility enhancements in the hot cell, the 99mTc extraction recovery increased to 44.86%, and elution recovery ranged from 90.62%. From the calculation results, the distribution coefficient value database (Kd-99mTc) was 0.45. Radionuclide and radiochemistry purity of the 99mTc solution were assessed using the Gamma Spectrometer and TLC Scanner, resulting in purity of 99.90% and 99.80%, respectively. These results underscore the potential for domestic production 99mTc, reducing reliance on imports.

Verification on Molybdenum-99 (99Mo) Breakthrough from Non-Fission 99Mo/99mTc Generator to Produce Technetium-99m (99mTc) Medical Radionuclide

Abstract The medical radionuclide 99mTc is the most widely used type of radionuclide in the field of nuclear medicine. 99mTc is the decay product of 99Mo. One of the quality control parameters of 99mTc is the 99Mo breakthrough limit. It is important to know the 99Mo breakthrough so that the quality of 99mTc produced can be optimal for diagnosis in nuclear medicine. This study aims to verify the 99Mo breakthrough activity from a non-fission 99Mo/99mTc generator whether they meet the established international limit standard. This research used a non-fission 99Mo/99mTc generator produced in multipurpose reactor G.A. Siwabessy, Indonesia. Gamma Spectrometer measurement of 99Mo and two 5 mL liquid standard sources of mix 133Ba and 152Eu used the same geometry. First standard as a calibration and efficiency identification function while the second standard is used to verify the measurement each at 3, 5, 7, 9 and 11 cm source to detector distance respectively. The 99Mo breakthrough activity (µCi) then devided to the activity of 99mTc (mCi) for the six eluted product from each days elution process of the generator. The results obtained showed that the 99Mo elution in the first elution had the highest breakthrough of 0.233 uCi 99Mo /mCi 99mTc, which exceeded the set limit of 0.15 uCi 99Mo /mCi 99mTc. While in the second, third, fourth, and fifth elution still have the 99Mo breakthrough, but these breakthrough did not exceed the limit and met one of the requirements of the 99mTc medical radionuclide parameter.

The Independence of Magnetic Turbulent Power Spectra to the Presence of Switchbacks in the Inner Heliosphere

An outstanding gap in our knowledge of the solar wind is the relationship between switchbacks and solar wind turbulence. Switchbacks are large fluctuations, even reversals, of the background magnetic field embedded in the solar wind flow. It has been proposed that switchbacks may form as a product of turbulence and decay via coupling with the turbulent cascade. In this work, we examine how properties of solar wind magnetic field turbulence vary in the presence or absence of switchbacks. Specifically, we use in situ particle and fields measurements from Parker Solar Probe to measure magnetic field turbulent wave power, separately in the inertial and kinetic ranges, as a function of switchback magnetic deflection angle. We demonstrate that the angle between the background magnetic field and the solar wind velocity in the spacecraft frame (θ vB ) strongly determines whether Parker Solar Probe samples wave power parallel or perpendicular to the background magnetic field. Further, we show that θ vB is strongly modulated by the switchback magnetic deflection angle. In this analysis, we demonstrate that switchback deflection angle does not correspond to any significant increase in wave power in either the inertial range or at kinetic scales. This result implies that switchbacks do not strongly couple to the turbulent cascade in the inertial or kinetic ranges via turbulent wave–particle interactions. Therefore, we do not expect switchbacks to contribute significantly to solar wind heating through this type of energy conversion pathway although contributions via other mechanisms, such as magnetic reconnection, may still be significant.

Radiogenic 32P as a new dating tool to determine groundwater ages of 50–1000 years

Groundwater age has significant hydrogeological implication for groundwater renewal and solute transport. The period between 50 to 1000 years, marked by increased human activity, which is also a gap of groundwater dating. Cosmogenic 32Si with a half-life of 144±11 a, is the only viable dating tool for this range but is seldom used due to complex pretreatment and time-consuming and expensive detection. Radiogenic 32P, as a daughter isotope of 32Si, decays by emitting high-energy β- particles and is easily detected. 32Si and 32P reaches radioactive equilibrium within 3 months, meaning they maintain consistent activity levels in groundwater aged between 50 and 1000 years. Therefore, 32P can be used to date groundwater in the range of 50–1000 a. 32P is enriched and extracted using Mg(OH)2 co-precipitation method. The 32P solution is then mixed with a solvent mixture containing Triton X-100 and Permafluor and detected using an ultra-low background liquid scintillation spectrometer. The counting time ranges from 2500 to 3000 min with an efficiency of 65 %, and the 32P count peak surface is observed between channels 600 and 900. Comparing the 32P ages with the 14C and 32Si ages of groundwater samples from the Jianghan Plain, Central China, reveals that 32P ages and 14C ages exhibit similar trends, and the 32P ages and 32Si ages are approximately consistent in the range of 50–1000 a. Therefore, radiogenic 32P dating groundwater in the range of 50–1000 a is feasible, convenient and reliable.

Using 26Al to detect ongoing self-enrichment in young massive star clusters

Abstract Self-enrichment is one of the leading explanations for chemical anomalies in globular clusters. In this scenario, various candidate polluter stars have been proposed to eject gas with altered chemical composition during the self-enrichment process. Most of the proposed polluters will also eject radioactive 26Al into the surroundings. Hence, any detection of 26Al in young massive star clusters (YMCs) would support the self-enrichment scenario if YMCs were indeed the progenitors of globular clusters. Observations of gamma-ray data from COMPTEL and INTEGRAL, as well as detections of 26AlF molecules by the Atacama Large Millimeter-submillimeter Array (ALMA), indicate the maturing of 26Al detection methods. Detection possibilities will be enhanced in the short- to mid-term by the upcoming launch of the Compton Spectrometer and Imager (COSI). The Square Kilometer Array (SKA) could in principle also detect radio recombination lines of the positronium formed from the decay products of 26Al. Here, we show for a sample of YMCs in the nearby Universe, where self-enrichment could plausibly take place. For some nearby galaxies, this could enhance 26Al by an order of one magnitude. Detecting 26AlF with ALMA appears feasible for many candidate self-enrichment clusters, although significant challenges remain with other detection methods. The Large Magellanic Cloud, with its YMC R136, stands out as the most promising candidate. Detecting a 1.8 MeV radioactive decay line of 26Al here would require at least 15 months of targeted observation with COSI, assuming ongoing self-enrichment in R136.

Manifestation of relativistic effects in the chemical properties of nihonium and moscovium revealed by gas chromatography studies.

Chemical reactivity of the superheavy elements nihonium (Nh, element 113) and moscovium (Mc, element 115) has been studied by the gas-solid chromatography method using a new combined chromatography and detection setup. The Mc isotope, 288Mc, was produced in the nuclear fusion reaction of 48Ca ions with 243Am targets at the GSI Helmholtzzentrum Darmstadt, Germany. After isolating 288Mc ions in the gas-filled separator TASCA, adsorption of 288Mc and its decay product 284Nh on silicon oxide and gold surfaces was investigated. As a result of this work, the values of the adsorption enthalpy of Nh and Mc on the silicon oxide surface were determined for the first time, kJ/mol and kJ/mol (68% c.i.). The obtained -ΔH ads values are in good agreement with results of advanced relativistic calculations. Both elements, Nh and Mc, were shown to interact more weakly with the silicon oxide surface than their lighter homologues Tl and Bi, respectively. However, Nh and Mc turned out to be more reactive than the neighbouring closed-shell and quasi-closed-shell elements copernicium (Cn, element 112) and flerovium (Fl, element 114), respectively. The established trend is explained by the influence of strong relativistic effects on the valence atomic orbitals of these elements.

PAIReD jet: A multi-pronged resonance tagging strategy across all Lorentz boosts

We propose a new approach of jet-based event reconstruction that aims to optimally exploit correlations between the products of a hadronic multi-pronged decay across all Lorentz boost regimes. The new approach utilizes clustered small-radius jets as seeds to define unconventional jets, referred to as PAIReD jets. The constituents of these jets are subsequently used as inputs to machine learning-based algorithms to identify the flavor content of the jet. We demonstrate that this approach achieves higher efficiencies in the reconstruction of signal events containing heavy-flavor jets compared to other event reconstruction strategies at all Lorentz boost regimes. Classifiers trained on PAIReD jets also have significantly better background rejections compared to those based on traditional event reconstruction approaches using small-radius jets at low Lorentz boost regimes. The combined effect of a higher signal reconstruction efficiency and better classification performance results in a two to four times stronger rejection of light-flavor jets compared to conventional strategies at low Lorentz-boosts, and rejection rates similar to classifiers based on large-radius multi-pronged jets at high Lorentz-boost regimes.

Radon Equilibrium Factor and the Assessment of the Annual Effective Dose at Underground Workplaces

The equilibrium factor F is one of the parameters that should be considered when assessing the effective dose based on radon activity concentration. Since the equilibrium factor in various environments ranges theoretically from a value close to 0 to 1, it is expected that dose assessment based on one recommended coefficient value may lead to an underestimation or overestimation of the dose. That is why it is essential to measure this quantity if the basis for dose assessment is the radon concentration and not the concentration of radon decay products. The equilibrium factors were determined based on measurements of radon activity concentration and potential alpha energy concentration and varied from 0.15 to 0.94, with an arithmetic mean of 0.55. The average effective dose calculated for the employee taking into account these values was 31 mSv, assuming an annual working time of 1800 h. In turn, the average effective dose calculated for the equilibrium factor of 0.2 as recommended by the International Commission on Radiological Protection (ICRP) was equal to 13 mSv.

Comprehensive analysis of local and nonlocal amplitudes in the B0→ K*0μ+μ− decay

A comprehensive study of the local and nonlocal amplitudes contributing to the decay B0 → K*0(→ K+π−)μ+μ− is performed by analysing the phase-space distribution of the decay products. The analysis is based on pp collision data corresponding to an integrated luminosity of 8.4 fb−1 collected by the LHCb experiment. This measurement employs for the first time a model of both one-particle and two-particle nonlocal amplitudes, and utilises the complete dimuon mass spectrum without any veto regions around the narrow charmonium resonances. In this way it is possible to explicitly isolate the local and nonlocal contributions and capture the interference between them. The results show that interference with nonlocal contributions, although larger than predicted, only has a minor impact on the Wilson Coefficients determined from the fit to the data. For the local contributions, the Wilson Coefficient C9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{C}}_9 $$\\end{document}, responsible for vector dimuon currents, exhibits a 2.1σ deviation from the Standard Model expectation. The Wilson Coefficients C10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{C}}_{10} $$\\end{document}, C9′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{C}}_9^{\\prime } $$\\end{document} and C10′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{C}}_{10}^{\\prime } $$\\end{document} are all in better agreement than C9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{C}}_9 $$\\end{document} with the Standard Model and the global significance is at the level of 1.5σ. The model used also accounts for nonlocal contributions from B0→ K*0[τ+τ−→ μ+μ−] rescattering, resulting in the first direct measurement of the bsττ vector effective-coupling C9τ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mathcal{C}}_{9\ au } $$\\end{document}.

Investigating generalized minimal supergravity in the MSSM through the long-lived bino NLSP at the HL-LHC

The axino, the supersymmetric partner of the axion, is a well-motivated warm/hot dark/cold matter candidate and provides a natural solution to the relic density problem for the binolike neutralino if it is the lightest supersymmetric particle (LSP). With the generalized minimal supergravity, we study such kind of the viable parameter space where the binolike neutralino is the next-to-LSP (NLSP) and the axino is the LSP. In addition, we consider a scenario where the bino is a long-lived NLSP with the lifetime varying from 10−6 to 10−4 s and then propose a new signal searching scheme involving one displaced photon together with the large missing transverse momentum at the HL-LHC. The binolike lightest neutralino lies under or around 100 GeV and is produced as a decay product of the right-handed sleptons. The relevant axion coupling fa can be probed up to O(109) GeV at 2σ level for the right-handed slepton mass under 800 GeV. Published by the American Physical Society 2024

Gravitational wave signatures of post-fragmentation reheating

After cosmic inflation, coherent oscillations of the inflaton field about a monomial potential V(ϕ) ∼ ϕ k result in an expansion phase characterized by a stiff equation-of-state w ≃ (k-2)/(k+2). Sourced by the oscillating inflaton condensate, parametric (self)resonant effects can induce the exponential growth of inhomogeneities eventually backreacting and leading to the fragmentation of the condensate. In this work, we investigate realizations of inflation giving rise to such dynamics, assuming an inflaton weakly coupled to its decay products. As a result, the transition to a radiation-dominated universe, i.e. reheating, occurs after fragmentation. We estimate the consequences on the production of gravitational waves by computing the contribution induced by the stiff equation-of-state era in addition to the signal generated by the fragmentation process for k = 4,6,8,10. We find that the signal generated during the fragmentation process gives a larger contribution than the one induced by the stiff equation-of-state era in given frequency ranges for all values of k. Our results are independent of the reheating temperature provided that reheating is achieved posterior to fragmentation. Our work shows that the dynamics of such weakly-coupled inflaton scenario can actually result in characteristic gravitational wave spectra with frequencies from Hz to GHz, in the reach of future gravitational wave observatories, in addition to the complementarity between upcoming detectors in discriminating (post)inflation scenarios. We advocate the need of developing high-frequency gravitational wave detectors to gain insight into the dynamics of inflation and reheating.