Topological Event Research Articles

Evolution of multiple asymptotic grain face and volume distributions during grain growth- connection to the initial distribution and asymptotic stabilization of the topological event rates

There has long been a question concerning the existence of a single vs. multiple asymptotic grain size distributions in normal grain growth. The goal of this study has been to address this topic by investigating the underlying mechanisms by which grain face and volume distributions evolve from transient to asymptotic states during grain growth. This investigation employs 3D Monte Carlo simulations to quantify the topological mechanisms of this transition, i.e., grain separation, encounter and loss, and examine their mutual evolution with the distributions from a wide range of initial states towards their multiple final asymptotic states. In the initial transient growth stage, the topological event rates fluctuate markedly, seeking balance among themselves and with the face/volume distributions. In the asymptotic stage this balance is indicated by asymptotic behavior of the ratios of the rates, as well the mean face class 〈f〉, and normalized widths, CV, of the face and size distributions. It was found that a moderate range of initial distributions evolved through relatively short transient periods towards asymptotic states less spread from each other but with those same relative orders of width. Initial distributions much wider or narrower than these evolved through longer transient periods with trajectories crossing the paths of the more moderate ones, with the widest initial distributions becoming the narrowest and the initially narrowest becoming the widest. These behaviors are explained by their interactive evolution with the topological event rates.

Riptide: a proton-recoil track imaging detector for fast neutrons

Riptide is a detector concept aiming to track fast neutrons. It is based on neutron-proton elastic collisions inside a plastic scintillator, where the neutron momentum can be measured by imaging the scintillation light. More specifically, by stereoscopically imaging the recoil proton tracks, the proposed apparatus provides neutron spectrometry capability and enable the online analysis of the specific energy loss along the track. In principle, the spatial and topological event reconstruction enables particle discrimination, which is a crucial property for neutron detectors. In this contribution, we report the advances on the Riptide detector concept. In particular, we have developed a Geant4 optical simulation to demonstrate the possibility of reconstructing with sufficient precision the tracks and the vertices of neutron interactions inside a plastic scintillator. To realistically model the optics of the scintillation detector, mono-energetic protons were generated inside a 6 × 6 × 6 cm3 cubic BC-408 scintillator, and the produced optical photons were propagated and then recorded on a scoring plane corresponding to the surfaces of the cube. The photons were then transported through an optical system to a 2 × 2 cm2 photo sensitive area with 1 Megapixel. Moreover, we have developed two different analysis procedures to reconstruct 3D tracks: one based on data fitting and one on Principal Component Analysis. The main results of this study will be presented with a particular focus on the role of the optical system and the attainable spatial and energy resolution.

NEXT-CRAB-0: a high pressure gaseous xenon time projection chamber with a direct VUV camera based readout

The search for neutrinoless double beta decay (0νββ) remains one of the most compelling experimental avenues for the discovery in the neutrino sector. Electroluminescent gas-phase time projection chambers are well suited to 0νββ searches due to their intrinsically precise energy resolution and topological event identification capabilities. Scalability to ton- and multi-ton masses requires readout of large-area electroluminescent regions with fine spatial resolution, low radiogenic backgrounds, and a scalable data acquisition system. This paper presents a detector prototype that records event topology in an electroluminescent xenon gas TPC via VUV image-intensified cameras. This enables an extendable readout of large tracking planes with commercial devices that reside almost entirely outside of the active medium. Following further development in intermediate scale demonstrators, this technique may represent a novel and enlargeable method for topological event imaging in 0νββ.

Evaluation of the response of plastic scintillator bars and measurement of neutron capture time in non-reactor environment for the ISMRAN experiment

We present a detailed study on detector response to different radioactive sources and the measurements of non-reactor environmental backgrounds with the Indian Scintillator Matrix for Reactor Anti-Neutrinos (ISMRAN) detector setup consisting of 9 × 10 Plastic Scintillator Bars (PSBs) array at BARC, Mumbai. These measurements are useful in the context of the ISMRAN detector setup, which will be used to detect the reactor anti-neutrinos (ν¯e) and measure its energy spectra through the inverse beta decay (IBD) process. A GEANT4 based Monte Carlo (MC) simulation is used to understand the optical transmission, energy resolution and energy non-linearity of the ISMRAN detector. A detailed analysis procedure has been developed to understand the natural radioactive, cosmogenic and cosmic muon-induced backgrounds with the ISMRAN detector setup in a non-reactor environment, based on their energy deposition, number of bars hit as well as topological event selection criteria in position and time for triggered events. Data and MC simulated distributions of reconstructed sum energy and number of bars hit has been compared for the radioactive γ + positron source such as 22Na placed at the center of the ISMRAN array. Fast neutron energy response and capture time distribution in ISMRAN array has been studied using a novel technique involving Time of Flight (TOF) of the measured fast neutrons. The observed characteristic neutron capture time (τ) of 68.29±9.48μs is in good agreement with ∼65μs obtained from MC simulation. These experimentally measured results will be useful for discriminating the correlated and uncorrelated background events from the true IBD events in reactor ON and OFF conditions inside the reactor hall.

Data Compression in the NEXT-100 Data Acquisition System.

NEXT collaboration detectors are based on energy measured by an array of photomultipliers (PMT) and topological event filtering based on an array of silicon photomultipliers (SiPMs). The readout of the PMT sensors for low-frequency noise effects and detector safety issues requires a grounded cathode connection that makes the readout AC-couple with variations in the signal baseline. Strict detector requirements of energy resolution better than 1% FWHM require a precise baseline reconstruction that is performed offline for data analysis and detector performance characterization. Baseline variations make it inefficient to apply traditional lossy data compression techniques, such as zero-suppression, that help to minimize data throughput and, therefore, the dead time of the system. However, for the readout of the SiPM sensors with less demanding requirements in terms of accuracy, a traditional zero-suppression is currently applied with a configuration that allows for a compression ratio of around 71%. The third stage in the NEXT detectors program, the NEXT-100 detector, is a 100 kg detector that instruments approximately five times more PMT sensors and twice the number of SiPM sensors than its predecessor, the NEXT-White detector, putting more pressure in the DAQ throughput, expected to be over 900 MB/s with the current configuration, which will worsen the dead time of the acquisition data system. This paper describes the data compression techniques applied to the sensor data in the NEXT-100 detector, which reduces data throughput and minimizes dead time while maintaining the event rate to the level of its predecessor, around 50 Hz.

Measurements using a prototype array of plastic scintillator bars for reactor based electron anti-neutrino detection

We report measurement of reactor based electron anti-neutrinos from a prototype array of plastic scintillator bars (mini-ISMRAN) located inside Dhruva research reactor hall, BARC. The detector setup took data for 128 days for reactor on (RON) and 51 days for reactor off (ROFF) condition. A detailed analysis procedure is developed to select the anti-neutrino candidate events based on the energy deposition, number of bars hit as well as topological event selection criteria in position and time. Each of these selection criteria are compared with Monte Carlo based simulations and further an embedding technique is used to estimate the efficiencies from a data driven background study. The obtained anti-neutrino like events in RON condition are 218 ± 50 (stat) ± 37 (sys) after background subtraction. The obtained results are compared with theoretical estimation which yields 214 ± 32 (sys) anti-neutrino events for the RON condition.

RIPTIDE: a novel recoil-proton track imaging detector for fast neutrons

Neutron detectors are an essential tool for the development of many research fields, as nuclear, particle and astroparticle physics as well as radiotherapy and radiation safety. Since neutrons cannot directly ionize, their detection is only possible via nuclear reactions. Consequently, neutron-based experimental techniques are related to the detection of charged particle or electromagnetic radiation originating from neutron-induced reactions. The study of fast neutrons is often based on the neutron-proton elastic scattering reaction. In this case, the ionization induced by the recoil protons in a hydrogenous material constitutes the basic information for the design and development of neutron detectors. Although experimental techniques have continuously improved and refined, so far, proton-recoil track imaging is still weak in laboratory rate environments because of the extremely small detection efficiency. To address this deficiency, we propose a novel recoil-proton track imaging system in which the light deriving from a fast scintillation signal is used to perform a complete reconstruction in space and time of the event. In particular, we report the idea of RIPTIDE (RecoIl Proton Track Imaging DEtector): an innovative system which combines a plastic scintillator coupled to imaging devices, based on CMOS technology, or micro channel plate sensors. The proposed apparatus aims at providing neutron spectrometry capability by stereoscopically imaging the recoil-protons tracks, correlating the spatial information with the time information. RIPTIDE intrinsically enable the online analysis of the ionization track, thus retrieving the neutron direction and energy, without spoiling the overall efficiency of the detection system. Finally, the spatial and topological event reconstruction enables particle discrimination — a crucial requirement for neutron detection — by deducing the specific energy loss along the track.

Characterization of events in the Rössler system using singular value decomposition

Chaotic systems change their behavior through topological events such as creation/annihilation and bifurcation. These can be characterized by defining a tangent phase space which measures the first-order response of stable limit cycles to a change in an external variable. If the period of the limit cycle is constant, then the tangent phase space response can be formulated as a boundary-value problem, which is dependent upon a previously calculated limit cycle. If the period is not constant, the tangent phase space will contain an unknown linear drift in time. This can be analytically removed by transforming into a time-dependent coordinate system in which one variable points in the direction of the instantaneous velocity in phase space. The remaining variables can then be decoupled from this motion, and will satisfy a linear system of differential equations subject to periodic boundary conditions. The solutions of these equations at bifurcation events can be analyzed using singular value decomposition of two matrices, one of which contains interactions within the limit cycle, while the other contains interactions with the changing external variable. Collectively, these two decompositions allow us to uniquely characterize any topological event. The method is applied to period-doubling and turning-points of limit cycles in the Rössler system, where it confirms previous work done on the Zeeman Catastrophe Machine. It is also applied to bifurcations of equilibria in the Rössler system, where it allows us to distinguish between Andronov-Hopf and fold-Hopf bifurcations.

Topology-Aware Non-Rigid Point Cloud Registration.

In this paper, we introduce a non-rigid registration pipeline for pairs of unorganized point clouds that may be topologically different. Standard warp field estimation algorithms, even under robust, discontinuity-preserving regularization, tend to produce erratic motion estimates on boundaries associated with 'close-to-open' topology changes. We overcome this limitation by exploiting backward motion: in the opposite motion direction, a 'close-to-open' event becomes 'open-to-close', which is by default handled correctly. At the core of our approach lies a general, topology-agnostic warp field estimation algorithm, similar to those employed in recently introduced dynamic reconstruction systems from RGB-D input. We improve motion estimation on boundaries associated with topology changes in an efficient post-processing phase. Based on both forward and (inverted) backward warp hypotheses, we explicitly detect regions of the deformed geometry that undergo topological changes by means of local deformation criteria and broadly classify them as 'contacts' or 'separations'. Subsequently, the two motion hypotheses are seamlessly blended on a local basis, according to the type and proximity of detected events. Our method achieves state-of-the-art motion estimation accuracy on the MPI Sintel dataset. Experiments on a custom dataset with topological event annotations demonstrate the effectiveness of our pipeline in estimating motion on event boundaries, as well as promising performance in explicit topological event detection.

The Event Detection System in the NEXT-White Detector.

This article describes the event detection system of the NEXT-White detector, a 5 kg high pressure xenon TPC with electroluminescent amplification, located in the Laboratorio Subterráneo de Canfranc (LSC), Spain. The detector is based on a plane of photomultipliers (PMTs) for energy measurements and a silicon photomultiplier (SiPM) tracking plane for offline topological event filtering. The event detection system, based on the SRS-ATCA data acquisition system developed in the framework of the CERN RD51 collaboration, has been designed to detect multiple events based on online PMT signal energy measurements and a coincidence-detection algorithm. Implemented on FPGA, the system has been successfully running and evolving during NEXT-White operation. The event detection system brings some relevant and new functionalities in the field. A distributed double event processor has been implemented to detect simultaneously two different types of events thus allowing simultaneous calibration and physics runs. This special feature provides constant monitoring of the detector conditions, being especially relevant to the lifetime and geometrical map computations which are needed to correct high-energy physics events. Other features, like primary scintillation event rejection, or a double buffer associated with the type of event being searched, help reduce the unnecessary data throughput thus minimizing dead time and improving trigger efficiency.

Complex networks of marine heatwaves reveal abrupt transitions in the global ocean

Understanding how marine heatwaves (MHWs) unfold in space and time under anthropogenic climate change is key to anticipate future impacts on ecosystems and society. Yet, our knowledge of the spatiotemporal dynamics of MHWs is very limited. Here, I combine network theory with topological data analysis and event synchronization to high-resolution satellite data and to a set of Earth System Model simulations to reveal the dynamical organization of complex MHW networks. The analysis reveals that MHWs have already crossed a tipping point separating highly synchronized preindustrial MHWs from the more extreme, but less coherent warming events we experience today. This loose spatiotemporal organization persists under a reduced RCP 2.6 emission scenario, whereas a second abrupt transition towards a permanent state of highly synchronized MHWs is foreseen by 2075 under a business-as-usual RCP 8.5 scenario. These results highlight the risks of abrupt ocean transitions, which may dramatically affect marine life and humanity by eroding valuable time for adaptation to climate change.

Particle identification at MeV energies in JUNO

JUNO is a multi-purpose neutrino experiment currently under construction in Jiangmen, China. It is primarily aiming to determine the neutrino mass ordering. Moreover, its 20 kt target mass makes it an ideal detector to study neutrinos from various sources, including nuclear reactors, the Earth and its atmosphere, the Sun, and even supernovae. Due to the small cross section of neutrino interactions, the event rate of neutrino experiments is limited. In order to maximize the signal-to-noise ratio, it is extremely important to control the background levels. In this paper we discuss the potential of particle identification in JUNO, its underlying principles and possible areas of application in the experiment. While the presented concepts can be transferred to any large liquid scintillator detector, our methods are evaluated specifically for JUNO and the results are mainly driven by its high optical photon yield of 1,200 photo electrons per MeV of deposited energy. In order to investigate the potential of event discrimination, several event pairings are analysed, i.e. α/β, p/β, e+/e−, and e−/γ. We compare the discrimination performance of advanced analytical techniques based on neural networks and on the topological event reconstruction keeping the standard Gatti filter as a reference. We use the Monte Carlo samples generated in the physically motivated energy intervals. We study the dependence of our cuts on energy, radial position, PMT time resolution, and dark noise. The results show an excellent performance for α/β and p/β with the Gatti method and the neural network. Furthermore, e+/e− and e−/γ can partly be distinguished by means of neural network and topological reconstruction on a statistical basis. Especially in the latter case, the topological method proved very successful.

Topological event rates and the evolution of the grain face distribution in grain growth

A theory is formulated that relates the rates of the three topological events to the evolution of the face distribution function. Implementation of the theory requires introduction of the concept of participation probabilities which reflect the face distribution of those grains that are incident upon the events. The prediction of the evolving face distribution is tested with a 3-D Monte Carlo simulation of the grain growth process that permits evaluation of the topological event rates by face class and the participation probabilities. The theory also develops a relation between the average number of faces per grain and the topological rates as well as the asymptotic distribution function; these results are also tested using the simulation. The transient period prior to normal grain growth is explained in terms of the evolution of the event rates that control the creation of small grains and evolve the face distribution to its final shape.

Listening | the open – music as disruptive topological experience

This article reflects on the relation between music body(ies)1, body(ies) of music2 and notions of musical ‘space-time’ in the composition and performance process of Listening | the open, a trilogy for disruptive bodies, by Joana Sá.Bringing into discussion new possible notions of space of music as both intrinsic and extrinsic dimensions of music body(ies), and of the body(ies) of music, it proposes approaching music as a disruptive topology. Presentingstrategies that are beyond the dualities of control/out of control, self/other, it emphasizes the fragment or fragmentation as a crucial basic topological event for triggering the musical processes.

Evidence for the Associated Production of a Single Top Quark and a Photon in Proton-Proton Collisions at sqrt[s]=13 TeV.

The first evidence of events consistent with the production of a single top quark in association with a photon is reported. The analysis is based on proton-proton collisions at sqrt[s]=13 TeV and recorded by the CMS experiment in 2016, corresponding to an integrated luminosity of 35.9 fb^{-1}. Events are selected by requiring the presence of a muon (μ), a photon (γ), an imbalance in transverse momentum from an undetected neutrino (ν), and at least two jets (j) of which exactly one is identified as associated with the hadronization of a b quark. A multivariate discriminant based on topological and kinematic event properties is employed to separate signal from background processes. An excess above the background-only hypothesis is observed, with a significance of 4.4 standard deviations. A fiducial cross section is measured for isolated photons with transverse momentum greater than 25GeV in the central region of the detector. The measured product of the cross section and branching fraction is σ(pp→tγj)B(t→μνb)=115±17(stat)±30(syst) fb, which is consistent with the standard model prediction.

Construction and commissioning of the tracker module for the SuperNEMO experiment

The SuperNEMO experiment will search for neutrinoless double-beta decay in the Modane Underground Laboratory. This decay mode, if observed, confirms that neutrinos are Majorana fermions. It would be a new lepton violating process, and would provide a measurement of the absolute neutrino mass. The SuperNEMO experiment is designed to reach a half-life sensitivity of 1026 years corresponding to an effective Majorana neutrino mass of 50−100 meV. The SuperNEMO demonstrator module is the first stage of the experiment, containing 7kg of 82Se, with an expected sensitivity of T½ (0ν) > 6.5×1024 y after 2.5 years. Full topological event reconstruction is achieved through the use of a wire tracker operating in Geiger mode combined with scintillator calorimeter modules. Construction of the demonstrator module is well underway. We present the design of the tracker, and the current status of the construction and commissioning efforts.

The trigger system in the NEXT-DEMO detector

NEXT-DEMO is a prototype of NEXT (Neutrino Experiment with Xenon TPC), an experiment to search for neutrino-less double beta decay using a 100 kg radio-pure, 90 % enriched (136Xe isotope) high-pressure gaseous xenon TPC with electroluminescence readout. The detector is based on a PMT plane for energy measurements and a SiPM tracking plane for topological event filtering. The experiment will be located in the Canfranc Underground Laboratory in Spain.Front-end electronics, trigger and data-acquisition systems (DAQ) have been built. The DAQ is an implementation of the Scalable Readout System (RD51 collaboration) based on FPGA. Our approach for trigger is to have a distributed and reconfigurable system in the DAQ itself. Moreover, the trigger allows on-line triggering based on the detection of primary or secondary scintillation light, or a combination of both, that arrives to the PMT plane.

Topological Characteristics of Two-Dimensional Grain Growth-Simulation and Analysis

A two-dimensional (2-D) grain growth simulation, using a curvature-driven vertex model applied to an initially Monte Carlo (MC)–generated microstructure, has been developed for analysis of the topological characteristics of the process, including the rates of different topological events and the effect of these event frequencies on the evolving grain structure. Findings include a constant ratio of the number fraction of disappearing grains to the area fraction swept by the grain boundary of 4/3; constant fractions of boundary sweeping due to grain disappearance (~2 pct), boundary-switching events (~8 pct), and simple boundary motion (~90 pct); and a constant ratio of 1.34 boundary-switching events per grain disappearance. An affinity term was developed to describe the tendency of grains of different edge classes to contact each other or to be involved in different topological events, relative to random behavior. The highest and lowest edge classes, 3 and 12, respectively, exhibited the highest affinity for mutual contact, a 16 times random occurrence, but an affinity of ~0 for contact with themselves. Intermediate edge classes showed an affinity of ~1, random contact, with other classes or with themselves. Few-edged grains showed ~0 affinity for contacting a disappearing trigon or gaining an edge in an edge-switching event, but had a high affinity, approaching 6, for losing an edge in a switching event. Many-edged grains showed the opposite trends and intermediate edge classes showed a random or less tendency for participation in any topological event. It was shown statistically that the growth rate of individual grains is controlled solely by the edge class, with essentially no direct effect from the grain size. The evolution of the grain area and edge class distributions were monitored throughout the transition from transient to steady-state grain growth, with a steady state achieved after loss of approximately 1/3 of the initial grains. The steady-state values of the coefficients of variation (CVs) of the edge class and grain area distributions were ~0.2 and 0.7, respectively.

Chapter 7 Experimental Tests of QCD

The following sections are included: Inclusive Distributions Exclusive Cross Sections and Form Factors Multiplicity Distribution Kinematical and Dynamical Correlations Topological Event Shapes Bose-Einstein Correlations (BEC) Possible Fractal Structure of Final State Phase-Space

On the total absolute curvature of an immersed sphere

A recent result of Tobias Ekholm [T. Ekholm, Regular homotopy and total curvature II: Sphere immersions into 3-space, Alg. Geom. Topol. 6 (2006) 493–513] shows that for every ϵ > 0 it is possible to construct a sphere eversion such that the total absolute curvature of the immersed spheres are always less than 8 π + ϵ . It is an open question whether this is the best possible. The paper contains results relating to this conjecture. As an interesting consequence of these methods it is shown that if during an eversion the total absolute curvature does not exceed 12 π then a certain topological event must take place, namely the immersion must become non-simple at some point. An immersion f in general position is simple if for any irreducible self-intersection curve of f in 3-space, its two pre-image curves in the sphere are disjoint.