Energy Distribution Of Particles Research Articles

Dark fluxes from electromagnetic cascades

We study dark sector production in electromagnetic (EM) cascades. This problem requires accurate simulations of Standard Model (SM) and dark sector processes, both of which impact angular and energy distributions of emitted particles that ultimately determine flux predictions in a downstream detector. We describe the minimal set of QED processes which must be included to faithfully reproduce a SM cascade, and identify a universal algorithm to generate a dark sector flux given a Monte-Carlo simulation of a SM shower. We provide a new tool, , which simulates EM cascades with associated dark vector production, and compare it against existing literature and “off the shelf” tools. The signal predictions at downstream detectors can strongly depend on the nontrivial interplay (and modelling) of SM and dark sector processes, in particular multiple Coulomb scattering and positron annihilation. We comment on potential impacts of these effects for realistic experimental setups.

Universality of kappa distributions

This paper reveals the universality of the particle energy distribution function, despite the arbitrariness that characterizes the generalized thermodynamic entropic function. We show that the canonical distribution, that is, the distribution function that maximizes this entropy under the constraints of canonical ensemble, is always the same and given by the kappa distribution function. We use the recently developed entropy defect to express the generalized entropic formulation. The entropy defect is a thermodynamic concept that describes the loss of entropy due to the order induced by the presence of correlations. Then we carry out functional analysis to maximize the implicit expression of the generalized entropy. Critically, we show that the Lagrange multipliers have the same exact arbitrariness as the generalized entropic function, allowing us to cancel it out and proving the universality of canonical distribution as the kappa distribution function.

Linear to circular conversion in the polarized radio emission of a magnetar

AbstractRadio emission from magnetars provides a unique probe of the relativistic, magnetized plasma within the near-field environment of these ultra-magnetic neutron stars. The transmitted waves can undergo birefringent and dispersive propagation effects that result in frequency-dependent conversions of linear to circularly polarized radiation and vice versa, thus necessitating classification when relating the measured polarization to the intrinsic properties of neutron star and fast radio burst emission sites. We report the detection of such behaviour in 0.7–4 GHz observations of the P = 5.54 s radio magnetar XTE J1810−197 following its 2018 outburst. The phenomenon is restricted to a narrow range of pulse phase centred around the magnetic meridian. Its temporal evolution is closely coupled to large-scale variations in magnetic topology that originate from either plastic motion of an active region on the magnetar surface or free precession of the neutron star crust. Our model of the effect deviates from simple theoretical expectations for radio waves propagating through a magnetized plasma. Birefringent self-coupling between the transmitted wave modes, line-of-sight variations in the magnetic field direction and differences in particle charge or energy distributions above the magnetic pole are explored as possible explanations. We discuss potential links between the immediate magneto-ionic environments of magnetars and those of fast radio burst progenitors.

CR-39 track detector calibration with H and He beams for applications in the p-11B fusion reaction

The 11B(p,α)2α reaction, generating three alpha particles, emerges as a promising alternative or complementary route for clean and efficient energy generation. A comprehensive understanding of reaction dynamics, energy distribution of emitted particles, and optimization of fusion efficiency requires precise diagnostic methods. CR39 detectors, being highly sensitive to ions and neutrons while remaining transparent to low fluxes of electrons and gammas, are extensively utilized as primary Solid State Nuclear Track Detector devices in laser-plasma environments. This study presents the CR-39 track detector calibration to low-energy protons and alpha particles. CR-39 irradiation took place at INFN-LNL (Istituto Nazionale di Fisica Nucleare — Laboratori Nazionali di Legnaro, Legnaro, Italy) across a range of energies (≥ 80 keV) up to a few MeV, employing various etching times with a NaOH solution. The observed discrepancy in particle diameters, related to a specific etching time, presents a promising avenue for distinguishing alpha particles from proton contributions. This finding holds potential for future practical applications in the study of 11B(p,α)2α fusion reactions.

Phase space distribution functions and energy distributions of dark matter particles in haloes

ABSTRACT For a spherical dark matter halo with isotropic velocity distribution, the phase space distribution function (DF), the energy distribution, and the density profile form a set of self-consistent description of its equilibrium state, and knowing one is sufficient to determine the other two. The Navarro–Frenk–White density profile (NFW profile) is known to be a good approximation to the spherically averaged density distribution in simulated haloes. The DARKexp energy distribution is also known to compare well with the simulated energy distribution. We present a quantitative assessment of the NFW and DARKexp fits to the simulated DF and energy distribution for a wide range of haloes in a dark-matter-only simulation from the IllustrisTNG Project. As expected, we find that the NFW fits work well except at low energy when the density at small radii deviates from the NFW profile. Further, the NFW and DARKexp fits have comparable accuracy in the region where both fit well, but the DARKexp fits are better at low energy because they require matching of the central gravitational potential. We also find an approximate relation between the energy scale parametrizing the DARKexp energy distribution and that defined by the characteristic density and radius of the NFW profile. This relation may be linked to the relaxation process during halo formation.

Estimating the jet power from Broadband SED modelling of Mkn 501 for different particle distributions

ABSTRACT We consider the broad-band spectral energy distribution of the high-energy-peaked blazar Mkn 501 using Swift-XRT/UVOT, NuSTAR and Fermi-LAT observations taken between 2013 and 2022. The spectra were fitted with a one-zone leptonic model using synchrotron and synchrotron self-Compton emission from different particle energy distributions such as a broken power law, log-parabola, as well as distributions expected when the diffusion or the acceleration time-scale are energy-dependent. The jet power estimated for a broken power-law distribution was ∼1047(1044) erg s−1 for a minimum electron energy γmin ∼ 10(103). However, for electron energy distributions with intrinsic curvature (such as the log-parabola form), the jet power is significantly lower at a few times 1042 erg s−1 which is a few per cent of the Eddington luminosity of a 107 M⊙ black hole, suggesting that the jet may be powered by accretion processes. We discuss the implications of these results.

Partial- and full-tunneling processes across potential barriers

We introduce the concept of partial-tunneling and full-tunneling processes to explain the seemingly contradictory non-zero and vanishing tunneling times often reported in the literature. Our analysis starts by considering the traversal time of a quantum particle through a potential barrier, including both above- and below-barrier traversals, using the theory of time-of-arrival operators. We then show that there are three traversal processes corresponding to non-tunneling, full tunneling, and partial tunneling. The distinction among the three depends on the support of the incident wave packet's energy distribution in relation to the shape of the barrier. Non-tunneling happens when the energy distribution of the quantum particle lies above the maximum of the potential barrier. Otherwise, full-tunneling process occurs when the energy distribution of the particle is below the minimum of the potential barrier. For this process, the obtained traversal time is interpreted as the tunneling time. Finally, the partial-tunneling process occurs when the energy distribution lies between the minimum and maximum of the potential barrier. This signifies that the quantum particle tunneled only through some portions of the potential barrier. We argue that the duration for a partial-tunneling process should not be interpreted as the tunneling time but instead as a partial traversal time to differentiate it from the full-tunneling process. We then show that a full-tunneling process is always instantaneous, while a partial-tunneling process takes a non-zero amount of time. We are then led to the hypothesis that experimentally measured non-zero and vanishing tunneling times correspond to partial- and full-tunneling processes, respectively.

Energy mapping of Jupiter's auroral electrons from Juno/UVS data using a new H2 UV emission model

Juno, which studies the Jovian system, continues to expand our knowledge of Jupiter's magnetosphere and its environment. Thanks to onboard instruments such as Jupiter Energetic Particle Detector Instrument (JEDI) and Jovian Auroral Distributions Experiment (JADE), in situ measurements have allowed us to derive a realistic representation of charged particle energy distributions precipitating in the auroral regions. Because of the distance between Juno's measurement location and the position of impact of the charged particles, where auroral emissions are produced, these energetic distributions of magnetospheric particles are likely to be affected by various phenomena such as wave-particle interactions on their way from Juno to the atmosphere. These processes can accelerate or decelerate the particles, changing their average energies. Hence, the energy distributions of particles measured at Juno's altitude are likely different from those at auroral altitudes. In this study we develop a UV emission model, combined with an electron transport model, that allows us to relate the auroral emission spectra of H$_ $ molecules with the energy distribution of impinging electrons. Thanks to observations of the Jovian aurora by the Ultraviolet Spectrograph (UVS) on board Juno, we determined the characteristic energies of electrons precipitating in auroral regions during perijove 32. We modeled the relationship between color ratio (CR) and the characteristic energy of precipitating electrons. Initially, we considered mono-energetic electron fluxes. In a second step, we considered fluxes governed by a kappa distribution. We derived characteristic energy maps for electrons precipitating in Jupiter's auroral regions. In comparison with similar previous studies based on Space Telescope Imaging Spectrograph on board Hubble Space Telescope (HST/STIS) observations, we find that modeling the CR with a mono-energetic distribution leads to a systematic underestimation of the average energy of electrons precipitating in the auroral regions by a factor of 3-5. In this study we show that it is possible to derive a more realistic estimate of electron energy flux distributions at auroral altitudes.

Energy correlations in heavy states

We study energy correlations in states created by a heavy operator acting on the vacuum in a conformal field theory. We argue that the energy correlations in such states exhibit two characteristic regimes as functions of the angular separations between the calorimeters: power-like growth at small angles described by the light-ray OPE and slowly varying, or “flat”, function at larger angles. The transition between the two regimes is controlled by the scaling dimension of the heavy operator and the dynamics of the theory. We analyze this phenomenon in detail in the planar mathcal{N} = 4 SYM theory both at weak and strong coupling. An analogous transition was previously observed in QCD in the measurement of the angular energy distribution of particles belonging to the same energetic jet. In that case it corresponds to the transition from the light-ray OPE, perturbative regime described in terms of correlations between quarks and gluons to the flat, non-perturbative regime described in terms of correlations between hadrons.

The case of the missing entropy

Abstract The free expansion of an ideal gas into a vacuum is commonly used to illustrate a spontaneous process; however, what is often overlooked for this process is that there is no change in temperature (inherently isothermal), no exchange of heat into or out of the system (adiabatic), and no work done on or by the system. That is, for the expansion of an ideal gas into a vacuum, there are no changes in the energetic states of the particles in the system and, thus, no change in the energetic entropy, ΔS E = 0. But, if ΔS E = 0, then why is the process spontaneous? The answer is because the number of positional microstates increases. This paper describes the “missing entropy” originating from the distribution of particles in a system, as measured by ΔS D. A positive ΔS D is the only change associated with processes that are inherently isothermal, adiabatic, and include no external work. The entropy of the distribution of particles, S D, was not included in Boltzmann’s distribution of energy in particles, S E, which is used to explain the second law of thermodynamics. In Gibbs development of statistical thermodynamics, Gibbs included both particle distribution and energy distribution in his ensembles but only included energy distribution in deriving the macroscopic laws of thermodynamics. Consequently, thermodynamics cannot explain why spontaneous processes occur in inherently isothermal systems where heat and work are zero, (Q = W = 0) and ΔU = ΔS E = 0. Examples of such processes include free expansion of an ideal gas, mixing of ideal gases, diffusion of an ideal solute, mixing of ideal solutes, osmosis with ideal solutions, and free discharge of a concentration battery with ideal solutions. This paper uses a combinatorial model of positional microstates to develop a statistical description of the entropy of the distribution of particles, S D, and applies the model to calculate ΔS D for these six examples of inherently isothermal processes in ideal systems. ΔS D has implications for correctly understanding processes in systems that do no work on the surroundings, for understanding colligative properties, and for understanding biological evolution and other information-driven, inherently isothermal systems.

Hierarchical high-point Energy Flow Network for jet tagging

Jet substructure observable basis is a systematic and powerful tool for analyzing the internal energy distribution of constituent particles within a jet. In this work, we propose a novel method to insert neural networks into jet substructure basis as a simple yet efficient interpretable IRC-safe deep learning framework to discover discriminative jet observables. The Energy Flow Polynomial (EFP) could be computed with a certain summation order, resulting in a reorganized form which exhibits hierarchical IRC-safety. Thus inserting non-linear functions after the separate summation could significantly extend the scope of IRC-safe jet substructure observables, where neural networks can come into play as an important role. Based on the structure of the simplest class of EFPs which corresponds to path graphs, we propose the Hierarchical Energy Flow Networks and the Local Hierarchical Energy Flow Networks. These two architectures exhibit remarkable discrimination performance on the top tagging dataset and quark-gluon dataset compared to other benchmark algorithms even only utilizing the kinematic information of constituent particles.

Hydrothermal signature on episodic deflation/inflation ground tilt at Aso Volcano

Ground deformation in volcanic areas induced by geothermal fluid circulation can reveal useful information about the dynamical processes occurring in the subsurface hydrothermal system. In the present work, we investigate tiltmeter time-series recorded at Aso Volcano during 2011–2016, a time interval during which different phases of volcanic activity occurred. We performed polarization analysis of the data and identified peculiar long-lasting (hours) transients, defined as Very-Long-period Tilt Pulses. The transients were further characterized in terms of waveform cross-correlation, particle tilt pattern, energy, and time distributions. The analyses indicate that such signals, which appear like deflation–inflation (DI) events, are associated with a Poissonian process whose underlying dynamics evolves over time always driven by a Poissonian mechanism. The obtained results have been interpreted in light of the available geophysical, geochemical and volcanological information. In this framework, the Very-Long-period Tilt Pulses may be ascribed to the depressurization/pressurization of the shallow hydrothermal system according to a fault-valve mechanism, which was active with different efficiency throughout eruptive and inter-eruptive phases.Graphical

A Model for Nonthermal Particle Acceleration in Relativistic Magnetic Reconnection

The past decade has seen an outstanding development of nonthermal particle acceleration in magnetic reconnection in magnetically dominated systems, with clear signatures of power-law energy distributions as a common outcome of first-principles kinetic simulations. Here we propose a semianalytical model for systematically investigating nonthermal particle acceleration in reconnection. We show particle energy distributions are well determined by particle injection, acceleration, and escape processes. Using a series of kinetic simulations, we accurately evaluate the energy- and time-dependent model coefficients. The resulting spectral characteristics, including the spectral index and lower and upper bounds of the power-law distribution, agree well with the simulation results. Finally, we apply the model to predict the power-law indices and break energies in astrophysical reconnection systems.

Study of the erosion and redeposition of W considering the kinetic energy distribution of incident ions through a semi-analytical model

In today’s nuclear fusion devices, erosion of high-Z metallic plasma-facing materials (PFMs) is mainly caused by physical sputtering. That is, by the exchange of energy between plasma ions and the atoms in the walls. In most of the numerical codes currently in use impinging plasma is approximated as a fluid. By averaging the incident particles’ energy distribution the high-energy population of the eroded material is underestimated. For heavy materials such as W, high-energy eroded particles tend to ionize far from the wall and they are less affected by the sheath electric field hence, not being attracted back to the wall, they have a higher chance to contaminate the core plasma. This could in turn result in an underestimation of the net erosion sources. In this work, a semi-analytical model was developed to include the energy distribution of the incident particles. Then, by Monte Carlo method, the net erosion of tungsten from a smooth PFM was calculated. The results show that the kinetic description in energy is important only for incident particles ionized once. For instance, it is particularly important for plasma ions such as Deuterium. It is seen that Deuterium contribution to the W net sources is not always negligible if compared to light impurities or to tungsten self-sputtering in the range of plasma parameters tested. Finally, results show that the difference between the fluid and kinetic models becomes more pronounced for high-screening plasma conditions.

Extracting clean low-energy spectra from silicon strip detector telescopes around punch through energies

The response of detector telescopes becomes complex around their relevant punch through energies: For some deposited energies the corresponding particle kinetic energies cannot be uniquely assigned, and these spurious energy regions can span several hundreds of keV if the telescopes are employed in close geometry. We present methods for producing clean low-energy spectra of light ions from detector telescopes consisting of thin double-sided silicon strip detectors (DSSSDs) backed by thick silicon pad detectors. By following these methods, the spectra of several such detector telescopes can be combined to span the entire relevant particle energy spectrum, above as well as below the punch through thresholds of the individual telescopes. The total energy spectrum resulting from the combination of all telescope spectra thus encompass the entire particle energy distribution in conjunction with the energy-dependent, setup-specific solid angle coverage. Energy spectra of beta-delayed proton emission from 21Mg are used to illustrate the methods.

Particles in Relativistic MHD Jets. I. Role of Jet Dynamics in Particle Acceleration

Relativistic jets from (supermassive) black holes are typically observed in nonthermal emission, caused by highly relativistic electrons. Here, we study the interrelation between three-dimensional (special) relativistic magnetohydrodynamics, and particle acceleration in these jets. We inject Lagrangian particles into the jet that are accelerated through diffusive shock acceleration and radiate energy via synchrotron and inverse Compton processes. We investigate the impact of different injection nozzles on the jet dynamics, propagation, and the spectral energy distribution of relativistic particles. We consider three different injection nozzles—injecting steady, variable, and precessing jets. These jets evolve with substantially different dynamics, driving different levels of turbulence and shock structures. The steady jet shows a strong, stationary shock feature, resulting from a head-on collision with an inner back-flow along the jet axis—a jet inside a jet. This shock represents a site for highly efficient particle acceleration for electrons up to a few tens of TeV and should be visible in emission as a jet knot. Overall, we find that the total number of shocks is more essential for particle acceleration than the strength of the shocks. The precessing jet is most efficient in accelerating electrons to high energies reaching even few hundred TeVs, with power-law index ranging from 2.3 to 3.1. We compare different outflow components, such as the jet and the entrained material concerning particle acceleration. For the precessing nozzle, the particle acceleration in the entrained material is as efficient as that in the jet stream. This is due to the higher level of turbulence induced by the precession motion.

Multiwavelength variability and broad-band SED modelling of BL Lac during a bright flaring period MJD 59000–59943

ABSTRACT We carried out a detailed temporal and spectral study of the BL Lacertae (BL Lac) by using the long-term Fermi-Large Area Telescope (LAT) and Swift-X-ray Telescope (XRT)/Ultraviolet Optical Telescope (UVOT) observations, during the period MJD 59000–59943. The daily-binned γ-ray light curve displays a maximum flux of $1.74\pm 0.09\times 10^{-5} \,\rm photons\, cm^{-2}\, s^{-1}$ on MJD 59868, which is the highest daily γ-ray flux observed from BL Lac. The γ-ray variability is characterized by power spectral density (PSD), rms–flux relation, and flux distribution study. We find that the power-law model fits the PSD with index ∼1, which suggests a long-memory process at work. The observed rms–flux relation exhibits a linear trend, which indicates that the γ-ray flux distribution follows a lognormal distribution. The skewness/Anderson–Darling test and histogram fit reject the normality of flux distribution, and instead suggest that the flux distribution is a lognormal distribution. The fractional variability amplitude shows that the source is more variable in the X-ray band than in optical/ultraviolet/γ-ray bands. In order to obtain an insight into the underlying physical process, we extracted broad-band spectra from different time periods of the light curve. The broad-band spectra are statistically fitted with the convolved one-zone leptonic model with different forms of the particle energy distribution. We found that spectral energy distribution during different flux states can be reproduced well with the synchrotron, synchrotron self-Compton, and external Compton emissions from a broken power-law electron distribution, ensuring equipartition condition. A comparison between the best-fitting physical parameters shows that the variation in different flux states is mostly related to an increase in the bulk Lorentz factor and spectral hardening of the particle distribution.

Hybrid deep learning for blazar classification and correlation search with neutrinos

ABSTRACT Since the successful discovery of neutrinos, their origin is still a mystery until the association with TXS 0506+056. More messengers are achievable to study the intrinsic mechanism of extreme phenomena. Recently, Fermi-LAT Collaboration published the fourth catalogue of active galactic nuclei (4LAC), together with Data Release 2 later, including totally 3148 sources. The majority of these objects are blazars, which are classified into flat-spectrum radio quasars (FSRQs), BL Lac-type objects (BLLs), and blazars of uncertain type (BCUs) according to their optical observation feature. The BCUs take up to 38.2 per cent of total, whose classification is quite challenging and manpower consuming. However with the remarkable advances of technology, deep learning has been widely applied in astronomy. In this work, we take the advantage of 11 machine learning algorithms plus the convolutional neural network (CNN)-based deep learning algorithm to classify BCUs based on 10 parameters and the broad-band spectral energy distribution of each object obtained with vou-blazars. On average, this method has impressive performance, reaching above 95 per cent of balanced accuracy for the training sample, best among the studies so far. We correlate the IceCube neutrinos and blazars in 4LAC, found a few possible associations. With the machine learning prediction, we later elaborate the association of these BCUs with neutrinos samples and find out most of the BCUs associated with neutrinos are with low synchrotron peak frequency, which may be due to the energy distribution of high-energy particles. We propose neutrinos might be another feature for objects classification in the future.

{B}_c^{-}to J/psi left(to {mu}^{+}{mu}^{-}right){tau}^{-}left(to {pi}^{-}{nu}_{tau },{rho}^{-}{nu}_{tau },{ell}^{-}{overline{nu}}_{ell }{nu}_{tau}right){overline{nu}}_{tau } decays with visible final-state kinematics

The semitauonic {B}_c^{-}to J/psi {tau}^{-}{overline{nu}}_{tau } decay provides an ideal and clean mode to scrutinize possible new physics effects in bto c{tau}^{-}{overline{nu}}_{tau } transitions as indicated by the current data on R(D(*)) anomalies. In this work, we use the spin density matrix method to obtain the maximum information on the underlying physics of {B}_c^{-}to J/psi {tau}^{-}{overline{nu}}_{tau } decay with both polarized τ lepton and J/ψ meson. Their subsequent decays, with J/ψ → μ+μ− as well as τ− → π−ντ, τ− → ρ−ντ and {tau}^{-}to {ell}^{-}{overline{nu}}_{ell }{nu}_{tau } , are exploited to extract the energy and angular distributions of the charged final-state particles in the processes. Starting with the most general effective Hamiltonian relevant for the bto c{tau}^{-}{overline{nu}}_{tau } transitions, including all possible Lorentz structures of the dimension-six operators with both left- and right-handed neutrinos, we first derive the five-fold differential decay rate in terms of the visible final-state kinematics. From this distribution, we then construct in total 34 normalized observables, among which nine refer to the CP-violating triple product asymmetries that vanish within the Standard Model. We also construct five new observables based on the combinations of these normalized observables that can only be attributed to the right-handed neutrinos. On the other hand, considering the low statistics of the fully differential distribution, we introduce some integrated observables with only one kinematic variable left, which are more promising to be measured due to the largely increased statistics. The sensitivities of all these observables to the different new physics scenarios are investigated in detail. Finally, assuming an ideal circumstance, we give an estimate of the statistical uncertainties of the nine CP-conserving observables at LHCb and found that τ− → π−ντ has the highest analyzing power among the three τ decay channels.

CLEAN imaging systematics of M87 radio jet

ABSTRACT The spectral index images of the jet in the nearby radio galaxy M87 have previously been shown with Very Long Baseline Interferometric arrays at 2–43 GHz. They exhibit flattening of the spectra at a location of inner (central) spine and towards outer ridges. This could imply optical depth effects, lower energy cut-off, or stratification of the emitting particles energy distribution. In this paper, we employ simulations of multifrequency VLBI observations of M87 radio jet with various model brightness distributions. CLEAN deconvolution errors produce significant features in the observed images. For intensity images, they result in the appearance of the inner ridge line in the intrinsically edge brightened jet models. For spectral index images, they flatten the spectra in a series of stripes along the jet. Another bias encountered in our simulations is steepening of the spectra in a low surface brightness jet regions. These types of the imaging artefacts do not depend on the model considered. We propose a method for the compensation of the systematics using only the observed data.