Final Decay 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.

Studying the Ξ(2030) as a predominantly K¯*Σ molecular state

Since its discovery in 1977, the spin parity of Ξ(2030) has not been fully determined experimentally. The latest Particle Data Group listing suggests it may be a baryon with J=5/2. Therefore, studying the mass spectrum and decay properties of Ξ(2030) has become a current hot topic to definitively establish its spin parity. As the three-quark model fails to explain Ξ(2030), we previously proposed it may be a molecule primarily composed of K¯*Σ with JP=5/2+, based on its mass spectrum study. To verify its molecular state interpretation, this work proposes studying the strong decays of Ξ(2030) assuming it is a P-wave JP=5/2+ meson-baryon molecule predominantly composed of K¯*Σ. We calculated all experimentally measured two-body and three-body final state decay widths of Ξ(2030), including Ξ(2030)→K¯Λ,K¯Σ,πΞ,πΞ*, and Ξ(2030)→ππΞ,πK¯Σ,πK¯Λ. The results indicate that both the total decay width and partial decay widths agree well with experimental values within the error margins. This supports that Ξ(2030) is a molecule with spin-parity JP=5/2+, predominantly composed of K¯*Σ. Compared to the experimental central values, our results are slightly smaller, which suggests that Ξ(2030) may contain additional components besides meson-baryon molecular components, such as three-quark structures. Published by the American Physical Society 2024

NMSSM explanation for excesses in the search for neutralinos and charginos and a 95 GeV Higgs boson

The observed excesses in the search for neutralinos and charginos by ATLAS and CMS can be fitted simultaneously in the minimal supersymmetric standard model (MSSM) assuming a light higgsino mass, of magnitude less than about 250 GeV, and a compressed higgsino dominated neutralino and chargino spectrum, with 5–10% mass splittings. However, light higgsinos as dark matter would have far too large direct detection cross sections. We consider the Next-to-MSSM (NMSSM) with an additional singlino-like lightest supersymmetric particle (LSP) a few GeV below the next-to-lightest supersymmetric particle (NLSP). Sparticles prefer to decay first into the NLSP and remnants from the final decay into the LSP are too soft to contribute to the observed signals. Co-annihilation in the higgsino-sector can generate a relic density in the WMAP/Planck window. The singlino-like LSP has automatically a direct detection cross section below present and future sensitivities: a direct detection signal in the near future would exclude this scenario. The singlet-like Higgs scalar of the NMSSM can have a mass around 95 GeV and signal cross sections in the bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$b\\bar{b}$$\\end{document} channel at LEP and in the γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma \\gamma $$\\end{document} channel at the LHC compatible with the respective observations.

Freely Decaying Saffman Turbulence Experimentally Generated by Magnetic Stirrers.

We investigate experimentally the decay of three-dimensional hydrodynamic turbulence, initially generated by the erratic motions of centimeter-size magnetic stirrers in a closed container. Such zero-mean-flow homogeneous isotropic turbulence is well suited to test Saffman's model and Batchelor's model of freely decaying turbulence. Here, we report a consistent set of experimental measurements (temporal decay of the turbulent kinetic energy, of the energy dissipation rate, and growth of the integral scale) strongly supporting the Saffman model. We also measure the conservation of the Saffman invariant at early times of the decay and show that the energy spectrum scales as k^{2} at large scales and keeps its self-similar shape during the decay. This Letter thus presents the first experimental evidence of the validity of the connection between the Saffman invariant and the k^{2}-energy spectrum of the large scales. The final decay regime closely corresponds to Saffman's model when the container size is sufficiently large.

Considerations on the relaxation time in shear-driven jamming.

We study the jamming transition in a model of elastic particles under shear at zero temperature, with a focus on the relaxation time τ_{1}. This relaxation time is from two-step simulations where the first step is the ordinary shearing simulation and the second step is the relaxation of the energy after stopping the shearing. τ_{1} is determined from the final exponential decay of the energy. Such relaxations are done with many different starting configurations generated by a long shearing simulation in which the shear variable γ slowly increases. We study the correlations of both τ_{1}, determined from the decay, and the pressure, p_{1}, from the starting configurations as a function of the difference in γ. We find that the correlations of p_{1} are longer lived than the ones of τ_{1} and find that the reason for this is that the individual τ_{1} is controlled both by p_{1} of the starting configuration and a random contribution which depends on the relaxation path length-the average distance moved by the particles during the relaxation. We further conclude that it is γ_{τ}, determined from the correlations of τ_{1}, which is the relevant one when the aim is to generate data that may be used for determining the critical exponent that characterizes the jamming transition.

Understanding the Origins of Quark Charges, Quantum of Magnetic Flux, Planck’s Radiation Constant and Celestial Magnetic Moments with the 4G Model of Nuclear Charge

Introduction: In our previous published papers, considering 3 large atomic gravitational constants assumed to be associated with weak, strong and electromagnetic interactions, we have proposed the existence of a nuclear charge of magnitude, en=2.95e and developed a nuclear mass formula associated with strong and weak interactions having 4 simple terms and only one energy coefficient. Methods: Two important assumptions are that there exists a weak fermion of rest energy 585 GeV and a strong coupling constant is the squared ratio of electromagnetic charge and nuclear charge. The aim of this paper is associated with understanding the mystery of the quantum of magnetic flux, Planck’s quantum radiation constant and Reduced Planck’s constant. Proceeding further, quark charges, strong coupling constant, nuclear stability, nuclear binding energy, medium and heavy atomic X-ray levels and celestial magnetic moments can be understood in a unified approach. It may also be noted that, by considering the integral nature of elementary particle masses, it seems possible to understand the discreteness of angular momentum. Results: Considering our proposed en=2.95e=3e as a characteristic nuclear charge, it seems possible to understand the integral nature of quarks electromagnetic charge. With this idea, neutron, proton and pion decay can be understood very easily. Conclusion: In all the cases, the up quark of charge (±2e) seems to play a crucial role in the internal transformation of the down quark of charge (±e) and external observable elementary basic elementary particles. It needs further study at the fundamental level.

Dark matter bound-state formation in the Sun

The Sun may capture asymmetric dark matter (DM), which can subsequently form bound-states through the radiative emission of a sub-GeV scalar. This process enables generation of scalars without requiring DM annihilation. In addition to DM capture on nucleons, the DM-scalar coupling responsible for bound-state formation also induces capture from self-scatterings of ambient DM particles with DM particles already captured, as well as with DM bound-states formed in-situ within the Sun. This scenario is studied in detail by solving Boltzmann equations numerically and analytically. In particular, we take into consideration that the DM self-capture rates require a treatment beyond the conventional Born approximation. We show that, thanks to DM scatterings on bound-states, the number of DM particles captured increases exponentially, leading to enhanced emission of relativistic scalars through bound-state formation, whose final decay products could be observable. We explore phenomenological signatures with the example that the scalar mediator decays to neutrinos. We find that the neutrino flux emitted can be comparable to atmospheric neutrino fluxes within the range of energies below one hundred MeV. Future facilities like Hyper-K, and direct DM detection experiments can further test such scenario.

Projected sensitivity to dimension-6 triple gauge couplings at the FCC-hh

In this study, we investigate the process pp→W±γ for the physics potential of the FCC-hh with s=100 TeV to examine the anomalous WWγ couplings defined by three CP-conserving and two CP-violating effective operators of dimension-6. The analysis containing the realistic detector effects is carried out in the mode where W± bosons in the final state decay into the leptonic channel. The best sensitivities obtained from the process pp→W±γ on the anomalous couplings CWWW/Λ2 and CW,B/Λ2 determined by CP-conserving effective Lagrangians are [−0.010;0.010] TeV−2 and [−0.40;0.41] TeV−2, while CW˜WW/Λ2 and CW˜/Λ2 couplings defined by CP-violating effective Lagrangian are obtained as [−0.003;0.003] TeV−2 and [−0.32;0.33] TeV−2 at the FCC-hh with Lint=30 ab−1. However, if the systematic uncertainty is included, we obtain reduced sensitivities on the anomalous WWγ coupling. The results are compared for assumed systematics of 5% and 10%.

Early Holocene thinning and final demise of the Scandinavian Ice Sheet across the main drainage divide of southern Norway

The thinning and final decay of the Scandinavian Ice Sheet in the Gudbrandsdalen area in central southern Norway is described, based on (1) cosmogenic 10Be surface exposure dating of 25 glacially transported boulders, (2) radiocarbon dating of plant remains in the basal strata in four lakes and (3) mapping of large ice-dammed lakes that formed at different elevations and at different times during the last deglacation. We complement the new chronology with previously published 10Be-ages from the same region. The dated samples are spread from mountain summits 1800 m a.s.l. to the valley floor at 250 m a.s.l. Our results suggest that the ice sheet surface remained well above 1800 m a.s.l. in northern Gudbrandsdalen throughout the Younger Dryas. During the Early Holocene the ice sheet thinned rapidly, at rates estimated to 1.7–5.8 m yr−1. The final phase of deglaciation involved formation of large ice-dammed lakes, most notably the Store Dølasjø which was formed after 10.4 ka BP and finally drained around 10.0 ka BP. The ice-marginal landforms that characterize the mountain region of northern Gudbrandsdalen, i.e., moraine ridges, lateral meltwater channels, as well as deposits and shorelines from ice-dammed lakes, thus collectively originate from a period of rapid ice sheet downwasting over ca. 1600 years.

Decay Dose Shielding Analysis with Hybrid Unstructured Mesh/Constructive Solid Geometry Monte Carlo Calculation and ADVANTG Acceleration

The target segments of the Oak Ridge National Laboratory Second Target Station (STS) neutron production facility become highly activated due to spallation reactions or nuclei transmutation by primary protons and emitted neutrons. Once the target segments are removed from their location within the core vessel, decay dose rates must be accurately quantified to determine the shielding configurations of remote-handling tools and transport casks and to aid in planning maintenance activities. For this analysis, we utilized a hybrid unstructured mesh (UM)/constructive solid geometry approach for calculating spallation products and neutron fluxes, activation calculations using the AARE package that includes the CINDER2008 activation code to calculate the decay photon source at different cooling times, and the ADVANTG code to accelerate the final decay photon transport calculation. Both Type 316 stainless steel (SS-316) and lead were investigated as candidates for shielding materials. The decay photon transport calculation through the thick SS-316 or lead shields exhibited between 25 and 30 orders-of-magnitude attenuations in the radial direction, depending on the shield. Such a difficult shielding calculation required advanced variance reduction. ADVANTG has some missing features, which limits its usability in spallation neutron source applications. It does not support volumetric sources created for MCNP6.2 UM capability. An approximate source was created for this problem. Not only was this approximate source needed for running the ADVANTG calculation to generate the weight windows, but also it was essential to develop source biasing (SB) parameters that were crucial for dramatically accelerating the decay photon transport in this problem. With this approximate source, the analysis was completed in a very reasonable computational time, and the design of the STS remote-handling equipment was finalized. This paper compares the efficiency of Monte Carlo simulations with different weight window and SB parameters calculated using different approximate ADVANTG calculations.

A Bayesian policy learning model of COVID-19 non-pharmaceutical interventions

ABSTRACT This article examines the impact of non-pharmaceutical interventions on the initial exponential growth of the infected population and the final exponential decay of the infected population. We employ a Bayesian dynamic model to test whether there is learning, a random walk pattern, or another type of learning with evolving epidemiological data over time across 168 countries and 41,706 country-date observations. Although we show that Bayesian learning is not taking place, most policy measures appear to assert some effect. In particular, we show that economic policy variables are of importance for the main epidemiological parameters derived from the policy learning model. In an empirical second-stage application, we further investigate the underlying dynamics between the epidemiological parameters and household debt repayments, a key economic variable, in the UK. Results show no Bayesian learning, although a higher transmission rate would increase household debt repayments, while the recovery rate would have a negative impact. Therefore, suboptimal learning is taking place.

The possible contribution of [formula omitted] meson decay into X(3872) and ϕ(1020)

In this paper, we present the branching ratio and polarization fraction of two body decay of Bs0 to the vector mesons ϕ(1020) and X(3872) in which the X(3872) meson can be considered as an intermediate resonance in the final decay Bs0→J/ψπ+π−ϕ(1020). For this aim, the naive factorization approach is used to calculate the decay amplitude with the different helicities due to the combination of polarization states of two mesons X(3872) and ϕ(1020). Within the framework of the factorization approach, we find the branching fraction for the two body channel of Bs0→X(3872)ϕ(1020)=(6.31±0.01)×10−5 and also Br(X(3872)→J/ψπ+π−) and Br(X(3872)→J/ψπ+π−)Br(Bs0→X(3872)ϕ(1020)) are calculated which are in well agreement with CMS collaboration data. Furthermore, we estimate the decay width of resonance X(3872) into final states J/ψπ+π− which is within the range of experimental data. By these results and available experimental data, we render the branching ratio of decays B+ and Bs0 into X(3872)K+ and X(3872)K0, respectively. Also, in the nonleptonic two body decay of Bs0→X(3872)ϕ(1020), the direct and indirect CP-violating asymmetries are estimated to indicate the potential role of the such decays to measure CP-violation.

Damping of surface waves by a floating viscoplastic plate

Surface waves have been observed to be brought to rest in finite time when a layer at the surface is impregnated with floating particles. A theoretical model is presented to explore whether a similar nonlinear damping process operates if the surface is covered by a thin plate of yield-stress fluid. The model demonstrates that the yield stress again arrests motion in finite time, although the final decay of the wave amplitude is faster than with floating particles.

Constructing micro-dynamic surface of boron-polyurethane with endurable anti-fouling properties

Self-polishing coatings (SPC) with renewable surfaces are widely used in the shipping industry and offshore installations to prevent unexpected costs and safety concerns from marine biofouling. However, self-polishing coatings still suffer from uncontrollable release of antifouling biocides which is called “initial burst and final decay” and poor mechanical properties. Herein, a series of controlled-release boron-polyurethane antifouling coatings (DBIT) were prepared with good mechanical properties and micro-dynamic surface. 2, 2-bis(hydroxymethyl)propionic acid (DMPA) and pyridine-diphenylborane (PDB) were used as reaction sites and antifouling functional side chain groups, respectively, which endowing the coatings with the controlled release ability and good performance. The results showed that the DBIT coatings had certain mechanical properties, up to an ultimate stress of 14.8 MPa. The DBIT75 coating could reduce 90.6 % settlement of Halamphora sp., 92.7 % settlement of Nitzschia closterium, and repel the settlement of mussels. More importantly, DBITx coatings displayed excellent antifouling performance for at least 4 months in the field test, which shows that the controlled-release polyurethane coatings provide a new choice for marine antifouling applications.

Interscale transfer of turbulent energy in grid-generated turbulence with low Reynolds numbers

Direct numerical simulations are performed for grid-generated turbulence with low Reynolds numbers to study the interscale transfer of turbulent energy. The Reynolds numbers based on the uniform velocity and grid mesh size, M, are set to ReM=5000, 9000, and 15000. The results show that, for ReM=9000 and ReM=15000, the turbulent dissipation constant increases in the upstream region but it becomes nearly constant in the region of x/M>15. In contrast, for ReM=5000, it continues to increase and do not level off even in the downstream region. Scale-by-scale analysis using the Karman–Howarth–Monin–Hill equation indicates that, the non-linear transfer term balances with the dissipation term for all the cases. Instead, it is found that, in the downstream region of the ReM=5000 case, where the turbulent Reynolds number becomes Reλ<25, the contribution of the advection term varies depending on the streamwise positions. Further analysis for the one-point statistics indicates that, in such conditions, the coherences among the advection term, dissipation term, and diffusion term become small at small scales, while they are generally large in the other cases including the upstream region for ReM=5000. These indicate that energy cascade mechanism in the downstream region for ReM=5000 is different from the cases of 30<Reλ<60, even though both of them are generally considered as small Reλ, and it is caused by the increase of the dissipation scale range appearing in the transition period to the final decay.

Damped perturbations in inviscid shear flows: van Kampen modes and Landau damping

We compare initial value and eigenvalue problems for two-dimensional perturbations of the inviscid shear flow in a channel. Singular solutions, known in plasma physics as van Kampen (vK) modes, are constructed. They form a complete set of eigenfunctions for decomposition of any initial perturbation for stable wavy perturbations. A pair of discrete modes appears to ensure completeness in the unstable case. Expansion coefficients for eigenmodes are found, and equivalence of temporal evolution obtained with the help of the evolutionary equation for vorticity and expansion over eigenmodes is presented. This alternative description of the evolution using vK modes is analogous to ones found earlier in plasma and in stellar dynamics. In particular, for stable wavy perturbations, an initial state decays first exponentially due to Landau damping, then algebraically. It has been established (numerically and analytically) that the final decay law is t−1. Also, we numerically demonstrate that Landau-damped perturbations are not true eigenmodes, but rather a superposition of vK-modes with a real frequency, which does not retain its shape over time. However, solution on contours in the complex plane may exhibit properties of a true eigenmode, that is, decay without changing its spatial form. Energy redistribution between perturbation and the flow, in stable and unstable regimes, is analyzed.

Rapid sea-level rise during the first phase of the Littorina transgression in the western Baltic Sea

Glacio-isostatic adjustment (GIA) corrected limiting non-marine and marine sea-level data from the western Baltic Sea indicate a rapid relative sea-level (RSL) rise of 18 m for the first phase of the Littorina transgression using a linear age-elevation model. This accelerated RSL rise occurred in the time period 8.57 to 8.0 ka before present (BP) with an RSL rise rate of 31.5 mm/year. RSL rose from 28 m to 10 m below the mean relative sea level (bmrsl) during the time period of less than 600 years. The first phase of Littorina transgression documents the last big meltwater pulse (MWP), which has been reported also from various other regions in the world as a consequence of the final decay of the Laurentide ice sheet and additional meltwater sources from Antarctica.

Bacteria Community Inhabiting Heterobasidion Fruiting Body and Associated Wood of Different Decay Classes.

The microbiome of Heterobasidion-induced wood decay of living trees has been previously studied; however, less is known about the bacteria biota of its perennial fruiting body and the adhering wood tissue. In this study, we investigated the bacteria biota of the Heterobasidion fruiting body and its adhering deadwood. Out of 7,462 operational taxonomic units (OTUs), about 5,918 OTUs were obtained from the fruiting body and 5,469 OTUs were obtained from the associated dead wood. Interestingly, an average of 52.6% of bacteria biota in the fruiting body was shared with the associated dead wood. The overall and unique OTUs had trends of decreasing from decay classes 1 to 3 but increasing in decay class 4. The fruiting body had the highest overall and unique OTUs number in the fourth decay class, whereas wood had the highest OTU in decay class 1. Sphingomonas spp. was significantly higher in the fruiting body, and phylum Firmicutes was more dominant in wood tissue. The FAPROTAX functional structure analysis revealed nutrition, energy, degradation, and plant-pathogen-related functions of the communities. Our results also showed that bacteria communities in both substrates experienced a process of a new community reconstruction through the various decay stages. The process was not synchronic in the two substrates, but the community structures and functions were well-differentiated in the final decay class. The bacteria community was highly dynamic; the microbiota activeness, community stability, and functions changed with the decay process. The third decay class was an important turning point for community restructuring. Host properties, environmental factors, and microbial interactions jointly influenced the final community structure. Bacteria community in the fruiting body attached to the living standing tree was suppressed compared with those associated with dead wood. Bacteria appear to spread from wood tissue of the standing living tree to the fruiting body, but after the tree is killed, bacteria moved from fruiting body to wood. It is most likely that some of the resident endophytic bacteria within the fruiting body are either parasitic, depending on it for their nutrition, or are mutualistic symbionts.

Universal Scaling for the Exit Dynamics of Block Copolymers from Micelles at Short and Long Time Scales.

The correlation function for the exit of poloxamer copolymers from equilibrated micelles is found to show up to four regimes depending on the chain flexibility: an initial fast reorganization, a logarithmic intermediate regime, followed by an exponential intermediate regime, and a final exponential decay. The logarithmic intermediate regime has been observed experimentally and attributed to the polydispersity of the polymer samples. However, we present dynamic single-chain mean-field theory simulations with chains of variable flexibility which show the same logarithmic relaxation but with strictly monodisperse systems. In agreement with our previous studies, we propose that this logarithmic response arises from a degeneracy of energy states of the hydrophobic block in the micelle core. For this to occur, a sufficiently large number of degenerate conformational states are required, which depend on the polymer flexibility and therefore should not be present for rigid polymers. Experimental results for monodisperse polymeric samples claiming the absence of such a logarithmic response may also lack a sufficient number of hydrophobic blocks for the required number of configurational states for this type of response to be seen. The insight gained from analyzing the simulation results allows us to propose a modified Eyring equation capable of reproducing the observed dynamic behavior. On scaling experimental results from different sources and systems according to this equation, we find a unique master curve showing a universal nature of the intermediate regimes: the logarithmic regime together with the secondary exponential decay. The terminal exponential regime at long times proposed by the standard Halperin and Alexander model is beyond the range of the data analyzed in this article. The universality observed suggests an entropic origin of the short-time dynamic response of this class of systems rather than the polydispersity.

Water- and Acid-Sensitive Cu2O@Cu-MOF Nano Sustained-Release Capsules with Superior Antifouling Behaviors.

Marine biofouling is one of the technical bottlenecks restricting the development of the global marine economy. Among the commercial self-polishing antifouling coatings, cuprous oxide is an irreplaceable component because of its efficiency and broad-spectrum antibacterial activity. However, one of the biggest obstacles to achieving long-term antifouling is the "initial burst and final decay" of cuprous oxide in the coating. Here, we lock the copper ions by establishing an antifouling unit composed of Cu2O (core) and Cu-based metal-organic framework (Cu-MOF, shell). Cu-MOF is densely grown in situ on the periphery of Cu2O by acid proton etching. The shell structure of Cu-MOF can effectively improve the stability of the internal Cu2O and thus achieve the stable and slow release of copper ions. Furthermore, Cu2O@Cu-MOF nanocapsules can also achieve active defense by rapid and complete dissolution of Cu2O@Cu-MOF at local acidic microenvironment (pH ≤ 5) where the adhesion of fouling organisms occurs. Super-resolution fluorescence microscopy is used to explain the sterilization mechanism. Relying on the water- and acid-sensitive properties of Cu-MOF shell, the stable, controlled and efficient release of copper ions has been achieved for the Cu2O@Cu-MOF nanocapsules in the self-polishing antifouling coatings. Thus, these controlled-release nanocapsules make long-term antifouling promising.