No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
On the Stopping of Fast Particle and on the Creation of Positive Electrons
Proceedings of the Royal Society A
... Minimal nuclei displacement is expected given orbital protons' high kinetic energy and limited attenuations when they reach the top device layer of SOI, but little is known about the optoelectronic device response to the charged particle interactions with the bounded electrons. Especially, the charged particles' inelastic scattering with bounded electrons takes place at much higher kinetic energy (up to 100MeV) [38] compared to nuclei (k-MeV). ...
... The nonlinear optical response does not change after heating up to 300 o C for an hour (Fig. S5). The reduced is attributed to the dangling bonds formed by the high energy protons swift through the 220nm thick Si layer on SOI (Fig. 4C) [38], while the proton with low kinetic energy (slowed down cosmic radiation in bulk device) leads to more extensive damage of nuclei displacement (or DDD) (Fig. 4D). Those displaced nuclei and vacancies act as carrier scattering centers and reduce the carrier mobility. ...
... The intrinsic region is lightly p-doped (10 16 cm -3 ). Heavily doped p++ and n++ regions (1×10 20 cm -3 ) were used to form Ohmic contact[38][39]. Vertical vias are patterned and etched on top of cladding oxide for the contact regions, followed by standard aluminum metallization for direct contact with the heavily doped Si regions.The photonic structures were defined by 248 nm deep-ultraviolet photolithography on an 8-inch SOI wafer with a 220 nm device layer, followed by reactive ion etching. ...
Reducing the form factor while retaining the radiation hardness and performance matrix is the goal of avionics. While a compromise between a transistor’s size and its radiation hardness has reached consensus in microelectronics, the size-performance balance for their optical counterparts has not been quested but eventually will limit the spaceborne photonic instruments’ capacity to weight ratio. Here, we performed space experiments of photonic integrated circuits (PICs), revealing the critical roles of energetic charged particles. The year-long cosmic radiation exposure does not change carrier mobility but reduces free carrier lifetime, resulting in unchanged electro-optic modulation efficiency and well-expanded optoelectronic bandwidth. The diversity and statistics of the tested PIC modulator indicate the minimal requirement of shielding for PIC transmitters with small footprint modulators and complexed routing waveguides toward lightweight space terminals for terabits communications and intersatellite ranging.
... Following the original Bethe and Heitler calculation [19], we consider scattering of a charged fermion off a heavy nucleus of mass M, electric charge eZ and magnetic moment M. The differential cross section for photon radiation is given by the familiar expression ...
... The bremsstrahlung cross section is obtained by substituting (19) into (1) ...
... In the anomaly-free medium b 0 ¼ 0 (26) reduces to the well-known Bethe-Heitler expression for the bremsstrahlung cross section on a heavy nucleus [19,40], ...
We study electromagnetic radiation by a fast particle carrying electric charge in chiral medium. The medium is homogeneous and isotropic and supports the chiral magnetic current which renders the fermion and photon states unstable. The instability manifests as the chirality-dependent resonances in the bremsstrahlung cross section, which enhance the energy loss in the chiral medium. We compute the corresponding cross sections in the single scattering approximation and derive the energy loss in the high-energy approximation.
... where: K = 4πN A m e c 2 r 2 e Z 2Aβ 2 and B = (1 − β 2 ) − 2γ−1 γ 2 ln 2 + 1 8 ( γ−1 γ ) 2 − δ In addition to the collision-related energy loss, there is an energy loss due to radiation emission (Bremsstrahlung) when the electron is accelerated in the Coulomb field of a nucleus. The average energy loss due to radiation emission is given by the Bethe-Heitler formula (see Eq. 1.25, (Bethe and Heitler, 1934)) in the region between mc 2 << E << 137mc 2 Z − 1 3 , showing that the energy loss increases quadratically with increasing atomic number (Z): From this equation, it can be noticed that the Bremsstrahlung yield is inversely proportional to the square of the particle's mass (m), so for heavy particles this effect is almost negligible for lower energies. The other conclusion is that for relatively small energies, the loss is independent of the kinetic energy of the incident electron, while for large energies, it increases proportionally to (E). ...
... This value corresponds to the so-called critical energy defined as the energy value at which collision energy loss equals Bremsstrahlung loss.(Patrignani, 2016;Bethe and Heitler, 1934). ...
The work carried out in this thesis was part of three National Institute of Nuclear Physics (INFN) projects called: Modeling and Verification for Ion beam Treatment planning (MoVe-IT), Superconducting Ion Gantry (SIG), and Flash Radiotherapy with hIgh Dose-rate particle beAms (FRIDA). Within the MoVe-IT project, two prototypes of silicon sensors were developed. The first one is a proton counter to be used as an online monitor of the fluence rate of clinical proton beams (Vignati et al., 2017; Sacchi et al., 2020; Fausti et al., 2021) and the second is a device able to measure the beam energy using Time-of-Flight technique (Marti Villarreal et al., 2021; Vignati et al., 2020a). The sensors used in these two prototypes represent an evolution of the n-on-p planar silicon sensor where a thin (1 micrometer) p+ gain layer is implanted under the n++ cathode. As a result of the doping profile, characterized by a large doping concentration at the n++/p+ junction, a local increase of the electric field up to 300 kV/cm in this region creates a controlled moderate electron/hole avalanche multiplication without a complete breakdown. This effect leads to a proportional signal enhancement with a noise level similar to that of a traditional silicon sensor of the same geometry. In 2020, we designed several sensors with diverse characteristics tailored to the needs of the two devices developed. The production is called MoVe-IT-2020. They are segmented into strips to reduce the particle rate per channel and minimize the signal pile-up. Chapter 2 describes the laboratory characterization of all the sensors used in this thesis. Additionally, the signals obtained in a preliminary test with proton beams at the National Centre for
Oncological Hadrontherapy (CNAO, Pavia, Italy) are presented, using a sensor with a large area from the MoVe-IT-2020 production. In chapter 3, the results of the telescope system proposed by the University of Turin and the National Institute of Nuclear Physics (Turin Section) in two Italian particle therapy centers are presented and discussed. Developments similar to the MoVe-IT project for clinical carbon ion beams are in progress within the SIG project. Chapter 4 reports the measurements
of individual carbon ions in the CNAO clinical beam with 60 μm thick silicon sensors.
Within the FRIDA project, the University and INFN of Turin are studying thin silicon sensors, recently designed and produced for single particle tracking in proton therapy, for electron beam monitoring in high dose-rate regimes. Chapter 5 describes the results of testing thin silicon sensors at Ultra-High dose rate (UHDR). In addition, the partial results of the first attempt to upgrade the LINAC (Elekta SL 25 MV) installed in the Physics Department of the University of Turin, dedicated entirely to research, is presented, which will allow in the near future experiments to study the FLASH effect. During my PhD, I wrote the following papers: Marti Villarreal et al., 2021; Villarreal et al., 2023; Villarreal et al., 2022, which reported the same results
presented in this thesis. The content of chapter 2 has been described in Villarreal et al., 2023; Villarreal et al., 2022 and a summary of the content of chapter 3 has been published in Marti Villarreal et al., 2021. Additionally, my work along my PhD contributed also to the following papers: Vignati et al., 2020c; Vignati et al., 2020a; Vignati et al., 2022b; Croci et al., 2023; Mohammadian-Behbahani et al., 2022; Giordanengo et al., 2022; Pennazio et al., 2022; Vignati et al., 2022a; Vignati et al., 2020b.
... The no-recoil regime we focus on here exists thanks to the large mass ratio between electron and nucleus, which for ionized hydrogen is m p /m e ≈ 2 · 10 3 . In this range an especially simple analytic expression for the cross section is available, through use of the leading Born approximation, which was computed by Bethe and Heitler, and Sauter in 1934 [26,27]. The explicit formula in the proton frame is given in App. ...
... Working in the rest frame of the orbiter, particle I, we explicitly compute the emission properties discussed in Sec. IV for the process e − p + → e − p + γ using the simple analytical expressions of [26,27]; see Fig. 4 for results. The energy range we focus on in the numerical evaluation of the emission characteristics is 1 ≪ γ ≪ m p /m e , which is ultrarelativistic on one hand, but allows us to neglect the nucleus' recoil, or momentum transfer, on the other hand. ...
Finite-energy particles in free fall can collide with diverging center-of-mass energy near rapidly rotating black holes. What are the most salient observational signatures of this remarkable geometric effect? Here we revisit the problem from the standpoint of the near-horizon extreme Kerr geometry, where these collisions naturally take place. It is shown that the ingoing particle kinematics admits a simple, universal form. Given a scattering cross section, determination of emission properties is reduced to evaluation of particular integrals on the sky of a near-horizon orbiting particle. We subsequently apply this scheme to the example of single-photon bremsstrahlung, substantiating past results which indicate that ejected particles are observable, but their energies are bounded by the rest masses of the colliding particles. Our framework is readily applicable for any scattering process.
... a result due to Bethe and Heitler [26] which relies on Born perturbation theory (plane waves for the incoming/outgoing electron), on whose general form we will comment below. If the target is an unshielded charge Ze, one has ...
... Eq. (26) illustrates that the ratio x ≡ε/m e controls the photon energy change, so that unless the energy of the photon in the electron rest-frame is comparable to or larger than the mass of the electron m e , the photon energy is only slightly altered. If the electron has a velocity β (Lorentz factor γ) in the Lab frame, eq. ...
The main goal of the present lectures is to outline the key particle interactions and energy loss mechanisms in the Galactic medium that high-energy particles are subject to. These interactions are an important ingredient entering the cosmic ray propagation equation, contributing to shape cosmic ray spectra. They also source the so-called secondary species, like gamma rays, neutrinos, "fragile" nuclei not synthesised in stars, and antiparticles, all routinely used as diagnostic tools in a multi-messenger context. These lectures are complementary to Denise Boncioli's ones, focusing instead on processes happening at ultra-high energies in the extragalactic environment. They include propaedeutic material to Felix Aharonian's and, to some extent, Stefano Gabici's and Carmelo Evoli's lectures.
... Positrons can be generated through three main processes: the Bethe-Heitler (BH) process [1][2][3][4][5][6], the trident process [7][8][9], and the Breit-Wheeler (BW) process [10]. The trident process is the direct interaction of electrons with the Coulomb field or laser field, while the BW process describes the generation of electron-positron pairs through collisions between photons, which implies that pure light can be turned into matter. ...
... In Eqs. (1) and (2), m e is the mass of electron/positron, E ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi m 2 e þ p 2 p and n ¼ p=p are the total energy and the propagation direction of a positron, σ are the Pauli matrices and η s is the spin state in the rest frame of the particle, respectively. We consider the positron propagating along the quantization z-axis of the overall system. ...
According to the conservation of angular momentum, when a plane-wave polarized photon splits into a pair of electron-positron under the influence of the Coulomb field, the spin angular momentum (SAM) of the photon is converted into the angular momentum of the leptons. We investigate this process (the Bethe-Heitler process) by describing the final electron and positron with twisted states and find that the SAM of the incident photon is not only converted into SAM of the produced pair, but also into their orbital angular momentum (OAM), which has not been considered previously. The average OAM gained by the leptons surpasses the average SAM, while their orientations coincide. Both properties depend on the energy and open angle of the emitted leptons. The demonstrated spin-orbit transfer shown in the Bethe-Heitler process may exist in a large group of QED scattering processes.
... production processes when sufficiently energetic γ rays (E γ ≥ 2m e c 2 = 1.022 MeV) interact with charged nuclei (so-called Trident and Bethe-Heitler processes 22 ), with the highest cross-section in high-Z materials. In the coming decade, it is proposed to use magnetic chicanes at FACET-II (SLAC) to combine the accelerator's e + and e − beams into a quasi-neutral jet 23 . ...
Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN’s Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations.
... Finally, relativistic effects also become non-negligible when the plasma temperature is above 10 8 K [15], which coincides with helium ignition in stars. The corresponding corrections to the Gaunt factors can be evaluated by use of the relativistic cross section of Bethe and Heitler [25], as was done in refs. [15] and [22]. ...
We revisit stellar constraints on dark photons. We undertake dynamical stellar evolution simulations which incorporate the resonant and off-resonant production of transverse and longitudinal dark photons. We compare our results with observables derived from measurements of globular cluster populations, obtaining new constraints based on the luminosity of the tip of the red-giant branch (RGB), the ratio of populations of RGB to horizontal branch (HB) stars (the R-parameter), and the ratio of asymptotic giant branch to HB stars (the R 2-parameter). We find that previous bounds derived from static stellar models do not capture the effects of the resonant production of light dark photons leading to overly conservative constraints, and that they over-estimate the effects of heavier dark photons on the RGB-tip luminosity. This leads to differences in the constraints of up to an order of magnitude in the kinetic mixing parameter.
... For instance, irradiating a thin, high-atomic number target with an intense laser pulse can energize a population of electrons. The bremsstrahlung photons emitted by the electrons subsequently decay into pairs through the Bethe-Heitler process [29,30,38]. As another example, the combined fields of a plasma and laser pulse channeling through a thin, dense target can rapidly accelerate electrons, resulting in both forward and backward photon emission. ...
Electron-positron pair creation occurs throughout the universe in the environments of extreme astrophysical objects, such as pulsar magnetospheres and black hole accretion disks. The difficulty of emulating these environments in the laboratory has motivated the use of ultrahigh-intensity laser pulses for pair creation. Here we show that the phase offset between a laser pulse and its second harmonic can be used to control the relative transverse motion of electrons and positrons created in the nonlinear Breit-Wheeler process. Analytic theory and particle-in-cell simulations of a head-on collision between a two-color laser pulse and electron beam predict that with an appropriate phase offset, the electrons will drift in one direction and the positrons in the other. The resulting current may provide a collective signature of nonlinear Breit-Wheeler, while the spatial separation resulting from the relative motion may facilitate isolation of positrons for subsequent applications or detection.
Published by the American Physical Society 2024
... All these approaches involve pair production processes when sufficiently energetic γ-rays (E γ ≥ 2m e c 2 = 1.022 MeV) interact with charged nuclei (so-called Trident and Bethe-Heitler processes [22]), with the highest cross-section in high-Z materials. In the coming decade, it is proposed to use magnetic chicanes at FACET-II (SLAC) to combine the accelerator's e + and e − beams into a quasi-neutral jet [23]. ...
... Another possibility is demonstrated for the Compton scattering process, in which the helical wavefront is transferred from the initial vortex photon to the final vortex γ photon, if the final electron is scattered along the collision axis [27]. Lepton-antilepton pairs can be created through the conversion of light into matter, as demonstrated in the Breit-Wheeler or Bethe-Heitler scattering processes [35][36][37][38][39][40][41][42]. However, the possibility of generating vortex leptons through a feasible post-selection scenario in pair creation dynamics with a substantial probability remains unknown. ...
Ultrarelativistic vortex leptons with intrinsic orbital angular momenta (OAM) have important applications in high energy particle physics, nuclear physics, astrophysics, etc. However, unfortunately, their generation still poses a great challenge. Here, we put forward a novel method for generating ultrarelativistic vortex positrons and electrons through nonlinear Breit-Wheeler (NBW) scattering of vortex γ photons. For the first time, a complete angular momentum-resolved scattering theory has been formulated, introducing the angular momentum of laser photons and vortex particles into the conventional NBW scattering framework. We find that vortex positron (electron) can be produced when the outgoing electron (positron) is generated along the collision axis. By unveiling the angular momentum transfer mechanism, we clarify that OAM of the γ photon and angular momenta of multiple laser photons are entirely transferred to the generated pairs, leading to the production of ultrarelativistic vortex positrons or electrons with large OAM. Furthermore, we find that the cone opening angle and superposition state of the vortex γ photon, distinct characteristics aside from its intrinsic OAM, can be determined via the angular distribution of created pairs in NBW processes. Our method paves the way for investigating strong-field quantum electrodynamics processes concerning the generation and detection of vortex particle beams in intense lasers.
... We emphasize that, while one can look for electronpositron pairs and muon-antimuon pairs from decay processes, the same final states can arise through the splitting process, also known as the Bethe-Heitler scattering process [26]. Owing to its energy-dependent nature, these final states can also be produced from a mediator with a keVrange mass, which is not kinematically allowed for decay processes. ...
Since many of the dark-sector particles interact with Standard Model (SM) particles in multiple ways, they can appear in experimental facilities where SM particles appear in abundance. In this study, we explore a particular class of longer-lived mediators that are dominantly produced from photons and charged mesons that arise in proton-beam fixed-target-type neutrino experiments. This class of mediators encompasses light scalars that appear in theories like extended Higgs sectors, muon(electro)philic scalars, etc. We evaluate the sensitivities of these mediators at beam-based neutrino experiments such as the finished ArgoNeuT, ongoing MicroBooNE, SBND, ICARUS, and the upcoming DUNE experiment. We find that muonphilic scalars are more enhanced while produced from three-body decay of charged mesons. The above-mentioned experiments can probe unexplored regions of parameter space that can explain the current discrepancy in the anomalous magnetic moment of muons. We further find that Compton-like scattering of photons is the largest source of electrophilic scalars. By utilizing this, the DUNE Near Detector can explore new regions in the sensitivity space of electrophilic scalars. We also show that Bethe-Heitler scattering processes can be used to probe flavor-specific lepton final states even for the mediator masses below twice the lepton mass.
... The analytical approximation for the typical differential positron track-length distribution TðE e þ Þ was studied in detail [68][69][70][71][72]. For the thick target it was shown that TðE e þ Þ depends, at first order, on a specific type of target material through the multiplicative factor TðE e þ Þ ∝ X 0 , where X 0 is the radiation length. ...
We discuss the thermal target curves of Majorana, Dirac, scalar, and vector light dark matter (DM) that are associated with the freeze-out mechanism via the annihilation into the e+e− pair through the electron-specific spin-0 mediator of dark matter. We also discuss the mechanism to produce the regarded DM mediator in the electron (positron) fixed-target experiments such as NA64e and LDMX. We derive the corresponding experimental reaches of NA64e and LDMX that are complementary to the DM thermal target parameter space.
... Especially for the light particles with low velocities, TDDFT has shown strong applicability, and precisely estimated the energy loss caused by electronic stopping [37]. This avoids the limitation of other models in low-energy applications, such as the Bethe's theory [4,38,39]. ...
The studies for the interaction of energetic particles with matter have greatly contributed to the exploration of material properties under irradiation conditions, such as nuclear safety, medical physics and aerospace applications. In this work, we theoretically simulate the non-adiabatic process for GaAs upon proton irradiation using time-dependent density functional theory, and find that the radial propagation of force on atoms and the excitation of electron in GaAs are non-synchronous process. We calculated the electronic stopping power on proton with the velocity of 0.1–0.6 a.u., agreement with the previous empirical results. After further analyzing the force on atoms and the population of excited electrons, we find that under proton irradiation, the electrons around the host atoms at different distances from the proton trajectories are excited almost simultaneously, especially those regions with relatively high charge density. However, the distant atoms have a significant hysteresis in force, which occurs after the surrounding electrons are excited. In addition, hysteresis in force and electron excitation behavior at different positions are closely related to the velocity of proton. This non-synchronous propagation reveals the microscopic dynamic mechanism of energy deposition into the target material under ion irradiation.
... where Δ W ¼ 1.1mm and Δ emu: ¼ 0.34mm are the widths of the tungsten and film layers, respectively. In addition to the propagation distance, we expect the photon angle distribution emitted from high-energy muons to be peaked around This can be easily seen by examining the bremsstrahlung differential cross section [54], where terms of the form sin 2 θ=ðE − jpj cos θÞ 2 are maximized for cos θ ¼ p E . After taking the small-angle and high-energy limits, one recovers Eq. (B2). ...
Only two types of Standard Model particles are able to propagate the 480meters separating the ATLAS interaction point and FASER: neutrinos and muons. Furthermore, muons are copiously produced in proton collisions. We propose to use FASERν as a muon fixed target experiment in order to search for new bosonic degrees of freedom coupled predominantly to muons. These muon force carriers are particularly interesting in light of the recent measurement of the muon anomalous magnetic moment. Using a novel analysis technique, we show that even in the current LHC run, FASERν could potentially probe previously unexplored parts of the parameter space. In the high-luminosity phase of the LHC, we find that the improved sensitivity of FASERν2 will probe unexplored parameter space and may be competitive with dedicated search proposals.
... When photons with energies greater than 10 MeV pass through a high-Z material, pair production starts to predominate over other interaction processes between photons and atoms. In Bethe-Heitler processes, electronpositron pairs are created with a nearly symmetrical energy distribution 35 , and the stopping powers of the two particles are almost identical 36 , resulting in similar changes in their energy spectra over a wide range of converter thicknesses. ...
Matter-antimatter plasmas, such as electron-positron pair plasmas, are frequently observed in various astrophysical phenomena. In laboratory settings, electron-positron pairs have often been generated using high-Z converters irradiated by either direct laser pulses or laser-driven electron beams. Here we generate charge-neutral electron-positron beams with energies in the GeV range, utilizing bremsstrahlung gamma rays. Specifically, intense high-energy gamma rays produced electron-positron pair particles in a lead converter via the Bethe-Heitler process. The produced pair beams exhibited neutrality across all converter thicknesses throughout the energy spectrum spanning from 10 MeV to 1.8 GeV. Pairs with energies surpassing 1 GeV constituted up to 26% of the total kinetic energy within the spectrum. The experimental results were in good agreement with our Geant4 Monte Carlo simulations. These GeV-scale neutral pair particle beams have potential applications for understanding energetic astrophysical phenomena and high-energy particle physics.
... The Bethe-Heitler process [38] consists of the creation of an electron-positron pair by the decay of an energetic photon in the Coulomb field of a nucleus: ...
In this paper we analyze the production of high energy synchrotron gamma photons in laser-plasma interaction for a laser intensity in 10 ²² −5·10 ²³ W/cm ² and a near-critical density target using 2D Particle-in-Cell simulations. In the optimum configuration to maximize the conversion efficiency of the laser energy to γ-photons, we studied the production of electron-positron pairs by the linear Breit-Wheeler process in the collision of two identical γ-photon beams using a dedicated photon-photon collision simulation code. A maximum laser energy conversion coefficient of 33% in high energy photons was obtained and a photon beam intensity, with energies above 1 MeV, of 2·10 ²⁰ W/cm ² at 150 μm distance from the initial position of the target (for the highest laser intensity considered). We show that the optimum case to detect the linear Breit-Wheeler pairs corresponds to a laser intensity of 10 ²³ W/cm ² . Our results can be used for the preparation of experimental campaigns for the detection of linear Breit-Wheeler pairs at the Apollon and ELI laser facilities.
... (2) Bethe-Heitler process. Gamma rays can be attenuated due to pair production upon interaction with relativistic ions in the ejecta (Bethe & Heitler 1934). The corresponding optical depth is given by Chodorowski et al. (1992), The scattering cross section can be approximated as (Zdziarski & Svensson 1989 where α = 1/137 is the fine structure constant, and Z is the atomic charge of the nuclei (we assume Z ; 1 for hydrogendominated composition). ...
Hypernebulae are inflated by accretion-powered winds accompanying hyper-Eddington mass transfer from an evolved post-main-sequence star onto a black hole or neutron star companion. The ions accelerated at the termination shock—where the collimated fast disk winds and/or jet collide with the slower, wide-angled wind-fed shell—can generate high-energy neutrinos via hadronic proton–proton reactions, and photohadronic ( p γ ) interactions with the disk thermal and Comptonized nonthermal background photons. It has been suggested that some fast radio bursts (FRBs) may be powered by such short-lived jetted hyper-accreting engines. Although neutrino emission associated with the millisecond duration bursts themselves is challenging to detect, the persistent radio counterparts of some FRB sources—if associated with hypernebulae—could contribute to the high-energy neutrino diffuse background flux. If the hypernebula birth rate follows that of stellar-merger transients and common envelope events, we find that their volume-integrated neutrino emission—depending on the population-averaged mass-transfer rates—could explain up to ∼25% of the high-energy diffuse neutrino flux observed by the IceCube Observatory and the Baikal Gigaton Volume Detector Telescope. The time-averaged neutrino spectrum from hypernebula—depending on the population parameters—can also reproduce the observed diffuse neutrino spectrum. The neutrino emission could in some cases furthermore extend to >100 PeV, detectable by future ultra-high-energy neutrino observatories. The large optical depth through the nebula to Breit–Wheeler ( γ γ ) interaction attenuates the escape of GeV–PeV gamma rays coproduced with the neutrinos, rendering these gamma-ray-faint neutrino sources, consistent with the Fermi observations of the isotropic gamma-ray background.
... O transporte é implementando por um algoritmo original para o cálculo de espalhamentos múltiplos (Ferrari et al., 1992), baseado na teoria de Moliére melhorada por Bethe (1953), suplementado por um algoritmo para o cálculo de espalhamento simples, baseado na fórmula de Rutherford. O tratamento das perdas de energia por ionização é baseado na teoria de Bethe-Block (Bethe;Heitler, 1934), suplementada com potenciais de ionização e parâmetros de efeitos de densidade determinados de acordo com a compilação de Sternheimer, Berger e Seltzer (1984) e com correções de camada derivadas da fórmula de Ziegler e Andersen (1977). ...
A modelagem de espectros de emissão de raios-y observados em explosões solares é geralmente realizada via melhor ajuste de dados utilizando-se um conjunto de templates e funções independentes para as componentes espectrais produzidas pelos vários processos relevantes (bremsstrahlung de elétrons e pósitrons, desexcitação nuclear, captura de nêutrons, aniquilação de pósitrons e decaimento de píons). Trabalhos recentes têm demonstrado o potencial do pacote Monte Carlo FLUKA como ferramenta efetiva para a simulação de processos nucleares no contexto de explosões solares, bem como sua capacidade de implementar um tratamento auto-consistente de todas as componentes típicas de espectros de emissão de raios-y observados. Neste trabalho, implementamos uma nova estratégia de simulação com o FLUKA que permite melhorar a estatística e a resolução em energia dos espectros de emissão de raios-y gerados. Utilizando essa estratégia, calculamos espectros de linhas de desexcitação nuclear que apresentam boa concordância com os calculados com o código desenvolvido por Murphy et al. (2009) considerando os mesmos parâmetros de modelo. A partir desses espectros, construímos templates que podem ser incorporados ao programa Objective Spectral Executive (OSPEX) e utilizados na análise de dados de emissão de raios-y de eventos observados com instrumentos tais como o Gamma-ray Burst Monitor (GBM) e o Large Area Telescope (LAT), ambos a bordo do satélite FERMI, e o Reuven Ramaty High Energy Spectroscopic Imager (RHESSI).
... The background signal comes from the Trident [52], Bethe-Heitler [53], and Triplet [54] processes. The noise from the Trident process is nearly perpendicular to the signal direction, and only the noise produced in the collision region will enter our detector [16]. ...
We report a proposal to observe the two-photon Breit-Wheeler process in plasma driven by compact lasers. A high-charge electron bunch can be generated from laser plasma wakefield acceleration when a tightly focused laser pulse propagates in a subcritical density plasma. The electron bunch scatters with the laser pulse coming from the opposite direction and resulting in the emission of high brilliance x-ray pulses. In a three-dimensional particle-in-cell simulation with a laser pulse of ∼10 J, one could produce an x-ray pulse with a photon number higher than 3×1011 and brilliance above 1.6×1023 photons/s/mm2/mrad2/0.1%BW at 1 MeV. The x-ray pulses collide in the plasma and create more than 1.1×105 electron-positron pairs per shot. It is also found that the positrons can be accelerated transversely by a transverse electric field generated in the plasma, which enables the safe detection in the direction away from the laser pulses. This proposal enables the observation of the linear Breit-Wheeler process in a compact device with a single shot.
... Laser-solid pair creation by QED processes mediated in Coulombic fields such as Bethe-Heitler (BH) [54] and Here, a region in time is identified as T boa which starts at the onset of transparency and extends till the enhanced ion acceleration slows down (after which the slope of maximum ion-energy begins to change to a smaller value). ...
The impact of radiation reaction and Breit–Wheeler pair production on the acceleration of fully ionized carbon ions driven by an intense linearly polarized laser pulse has been investigated in the ultra-relativistic transparency regime. Against initial expectations, the radiation reaction and pair production at ultra-high laser intensities are found to enhance the energy gained by the ions. The electrons lose most of their transverse momentum, and the additionally produced pair plasma of Breit–Wheeler electrons and positrons co-streams in the forward direction as opposed to the existing electrons streaming at an angle above zero degree. We discuss how these observations could be explained by the changes in the phase velocity of the Buneman instability, which is known to aid ion acceleration in the breakout afterburner regime, by tapping the free energy in the relative electron and ion streams. We present evidence that these non-classical effects can further improve the highest carbon ion energies in this transparency regime.
... 12 Dirac also theorized that electron/positron pairs could spontaneously arise out of the "Dirac sea." 13 Following on Dirac's work, Hans Bette and Walter Heitler theorized that electron/positron pairs could be generated by high energies of electromagnetism interacting with a nucleus. 14 The process of electron/positron generation near nuclei is usually called the Bethe-Heitler Process. ...
It has been theorized that, at the Universe's inception, there were equal amounts of matter and antimatter. One of the great mysteries of modern physics is the asymmetry between the amount of matter apparent in the Universe and the amount of antimatter apparent here. As has been understood for decades, hadrons (i.e., protons and neutrons) consist of up quarks and down quarks. Based on laser experiments conducted in the United States, it has been hypothesized that hadrons can also be composed of up antiquarks and down antiquarks, in conjunction with a positron, to form protons and neutrons. Here it is shown that experiments at the Texas Petawatt Laser Facility involving a high-energy laser striking a gold target demonstrate that, when positrons are ejected from protons in the gold target, the gold is transmutated to platinum. That experimental result indicates that hadrons are actually composite particles containing both matter and antimatter. The implications of this new model of hadron structure, called the Symmetry Model by the author, are significant, impacting our understanding of cosmology, proton-proton chain reactions in stars, the expansion of the Universe, and beta decay in radioactive isotopes, among other key topics in physics.
... The bremsstrahlung photons emitted by the electrons subsequently decay into pairs through the Bethe-Heitler process. 23,24,31 As another example, the combined fields of a plasma and laser pulse channeling through a thin, dense target can rapidly accelerate electrons, resulting in both forward and backward photon emission. The collision of the counter-propagating photons can produce pairs through the linear Breit-Wheeler process. ...
Electron-positron pair creation occurs throughout the universe in the environments of extreme astrophysical objects, such as pulsar magnetospheres and black hole accretion disks. The difficulty of emulating these environments in the laboratory has motivated the use of ultrahigh-intensity laser pulses for pair creation. Here we show that the phase offset between a laser pulse and its second harmonic can be used to control the relative transverse motion of electrons and positrons created in the nonlinear Breit-Wheeler process. Analytic theory and particle-in-cell simulations of a head-on collision between a two-color laser pulse and electron beam predict that with an appropriate phase offset, the electrons will drift in one direction and the positrons in the other. The resulting current may provide a collective signature of nonlinear Breit-Wheeler, while the spatial separation resulting from the relative motion may facilitate isolation of positrons for subsequent applications or detection.
... Although there have been several investigations [46][47][48][49][50][51] that were devoted to these laser-nucleus configurations, a complete description of this problem is still a challenge, and the resonant situation in particular is far from complete. The resonant laser-assisted Bethe-Heitler process [52] for the case of a weak monochromatic [53,54] and pulsed [55,56] plane-wave field was also examined. ...
We examine the electron-positron pair-creation process from the quantum vacuum triggered by two colliding laser beams in the presence of a nuclear binding potential. Once the two pulses overlap, they form a standing-wave pattern with nodes or antinodes in the region where the nucleus is placed. As the resulting spatial intensity pattern depends on the phase between both fields, it can be used to control the pair-creation yield. It turns out that the ground-state capture of the created electrons can actually be largest for those laser phases that lead to nodes (dark intensity regions) where the nucleus is located and not for those that lead to antinodes (bright intensity regions). Furthermore, this phase can be used to control selectively into which excited state the created electrons are predominately captured.
... For the synthesis of optically thick lines (Hα, Lyα, He II 304), we have run a few simulations of HYDRAD using its NLTE chromosphere ) and synthesized the emission with the RH1.5D 5 radiative transfer code (Pereira & Uitenbroek 2015). In the calculations of X-ray spectra, we additionally synthesize the nonthermal free-free emission directly, using the assumed electron beam parameters and the full Bethe-Heitler cross section (Bethe & Heitler 1934) with the Elwert correction factor (Elwert 1939) that accurately captures the cross section across both nonrelativistic and relativistic energies (Koch & Motz 1959). We additionally synthesize nonthermal free-bound emission for beam electrons recombining onto Fe XXII through Fe XXVI ions, based on the derivation in Brown & Mallik (2008) and corrections in Reep & Brown (2016). ...
Recent irradiance measurements from numerous heliophysics and astrophysics missions including SDO, GOES, Kepler, TESS, Chandra, XMM-Newton, and NICER have provided critical input in understanding the physics of the most powerful transient events on the Sun and magnetically active stars, solar and stellar flares. The light curves of flare events from the Sun and stars show remarkably similar shapes, typically with a sharp rise and protracted decay phase. The duration of solar and stellar flares has been found to be correlated with the intensity of the event in some wavelengths, such as white light, but not in other wavelengths, such as soft X-rays, but it is not evident why this is the case. In this study, we use a radiative hydrodynamics code to examine factors affecting the duration of flare emission at various wavelengths. The duration of a light curve depends on the temperature of the plasma, the height in the atmosphere at which the emission forms, and the relative importance of cooling due to radiation, thermal conduction, and enthalpy flux. We find that there is a clear distinction between emission that forms low in the atmosphere and responds directly to heating, and emission that forms in the corona, indirectly responding to heating-induced chromospheric evaporation, a facet of the Neupert effect. We discuss the implications of our results to a wide range of flare energies.
... Sommerfeld [19] developed a theory for the production of EB by the interaction of nonrelativistic electrons with the Coulomb field of the nucleus (of the target material). Sauter [20], Racah [21], and Bethe and Heitler [22] independently developed theories for EB produced by relativistic incident electrons. However, Tseng and Pratt [23] have found an exact theory using Coulomb field wave function, and it has been extended to an atomic electron field by Seltzer and Berger [24]. ...
The development of high-Z (high atomic number) radiation shielding materials is vital in order to protect personnel who work with harmful gamma radiation sources. At the same time, the emission of external bremsstrahlung (EB) radiation in those shielding materials when the radiation source emits beta particles as well as gamma radiation is also of prime concern.The production of EB in films of lead monoxide (PbO) loaded polycarbonate (PC) composite at eleven different filler levels (FLs) varying, in terms of weight fraction, from 0.0 % up to 10.0 % were investigated experimentally by using beta particles from strontium-90/yttrium-90 (90Sr/90Y) radioactive source. A nonlinear relation is observed between EB intensity and target thickness. The effective atomic numbers of the prepared PbO-filled PC composite films (at different FLs) were determined via EB measurements, followed by calculations, and the values obtained were compared with the modified atomic numbers which were determined for the same composite films (at different FLs) using the Markowicz and Van Grieken equation, and it was found that they are in good agreement. Finally, the atomic number dependence of EB in these composite films (PbO-filled PC composites) has been studied. It is obtained that the intensity of EB spectra depends on the square of the atomic number of the target material.
... The one area that is substantially affected at the HALHF is the measurement of luminosity, vital for the calculation of any cross sections. At HERA, this was achieved by the measurement of the ep → epγ bremsstrahlung process, known as Bethe-Heitler scattering [74]. This is a quantum-electrodynamics (QED) process with a large and accurately calculable cross section in which both electron and photon are emitted at small angles to the incident electron direction. ...
The construction of an electron–positron collider “Higgs factory” has been stalled for a decade, not because of feasibility but because of the cost of conventional radio-frequency (RF) acceleration. Plasma-wakefield acceleration promises to alleviate this problem via significant cost reduction based on its orders-of-magnitude higher accelerating gradients. However, plasma-based acceleration of positrons is much more difficult than for el ectrons. We propose a collider scheme that avoids positron acceleration in plasma, using a mixture of beam-driven plasma-wakefield acceleration to high energy for the electrons and conventional RF acceleration to low energy for the positrons. We emphasise the benefits o f a symmetric e nergies, a symmetric b unch charges a nd a symmetric t ransverse emittances. The implications for luminosity and experimentation at such an asymmetric facility are explored and found to be comparable to conventional facilities; the cost is found to be much lower. Some of the areas in which R&D is necessary to make HALHF a reality are highlighted, including estimates for the improvement required in key technologies. These range from a factor of 10 to a factor of 1000.
... The theoretical foundations of the former were laid in the late 1990's, by Zakharov, Baier, Dokshitzer, Mueller, Peigné, Schiff, [1][2][3][4][5][6][7] who showed that not only can an energetic parton passing through dense QCD matter lose energy elastically but also by medium-induced gluon radiation triggered coherently by multiple scatterings during the quantum mechanical formation time of the fluctuation. The resulting radiative spectrum is suppressed at high JHEP05(2023)091 gluon frequency due to the so-called Landau-Pomeranchuk-Migdal effect [8] as compared to incoherent Bethe-Heitler radiation [9]. As a result, the average energy loss was shown to scale quadratically with medium size in contrast with the linear growth of elastic energy loss and therefore becomes the dominant energy loss mechanisms for large QCD media. ...
A bstract
We perform numerical studies in the framework of QCD kinetic theory to investigate the energy and angular profiles of a high energy parton — as a proxy for a jet produced in heavy ion collisions — passing through a Quark-Gluon Plasma (QGP). We find that the fast parton loses energy to the plasma mainly via a radiative turbulent quark and gluon cascade that transports energy locally from the jet down to the temperature scale where dissipation takes place. In this first stage of the system time evolution, the angular structure of the turbulent cascade is found to be relatively collimated. However, when the lost energy reaches the plasma temperature it is rapidly transported to large angles w.r.t. the jet axis and thermalizes. We investigate the contribution of the soft jet constituents to the total jet energy. We show that for jet opening angles of about 0.3 rad or smaller, the effect is negligible. Conversely, larger opening angles become more and more sensitive to the thermal component of the jet and thus to medium response. Our result showcases the importance of the jet cone size in mitigating or enhancing the details of dissipation in jet quenching observables.
... at an outer mass column density , assuming that heat is efficiently redistributed between the tidally locked companion's day and night hemispheres (this assumption holds for high-energy photons that are deposited deep enough in the atmosphere; see GQ21). We choose = 180 g cm −2 , given by the pair production cross section, which dominates the interaction of the pulsar's energetic GeV photons with the companion's atmosphere (Bethe & Heitler 1934 ). ...
Black widows and redbacks are binary millisecond pulsars with close low-mass companions that are irradiated and gradually ablated by the pulsar’s high-energy luminosity Lirr. These binaries evolve primarily through magnetic braking, which extracts orbital angular momentum and pushes the companion to overflow its Roche lobe. Here, we use the stellar evolution code mesa to examine how the irradiation modifies the companion’s structure. Strong Lirr inhibits convection to the extent that otherwise fully convective stars become almost fully radiative. By computing the convective velocities and assuming a dynamo mechanism, we find that the thin convective envelopes of such strongly irradiated companions (Lirr ≳ 3 L⊙) generate much weaker magnetic fields than previously thought – halting binary evolution. With our improved magnetic braking model, we explain most observed black widow and redback companions as remnants of main-sequence stars. We also apply our model (with Lirr) to evolved companions that overflow their Roche lobe close to the end of their main-sequence phase. The evolutionary tracks of such companions bifurcate, explaining the shortest period systems (which are potential gravitational wave sources) as well as the longest period ones (which are the progenitors of common pulsar–white dwarf binaries). The variety of black widow structures and evolutionary trajectories may be utilized to calibrate the dependence of magnetic braking on the size of the convective layer and on the existence of a radiative–convective boundary, with implications for single stars as well as other binaries, such as cataclysmic variables and AM Canum Venaticorum stars.
... We emphasize that while one can look for electronpositron pairs and muon-antimuon pairs from decay processes, the same final states can arise through the splitting process, also known as the Bethe-Heitler scattering process [26]. Owing to its energy-dependent nature, these final states can also be produced from a mediator with a keV-range mass, which is not kinematically allowed for decay processes. ...
Since many of the dark-sector particles interact with Standard Model (SM) particles in multiple ways, they can appear in experimental facilities where SM particles appear in abundance. In this study, we explore a particular class of longer-lived mediators that are produced from photons, charged mesons, neutral mesons, and $e^\pm$ that arise in proton-beam fixed-target-type neutrino experiments. This class of mediators encompasses light scalars that appear in theories like extended Higgs sectors, muon(electro)philic scalars, etc. We evaluate the sensitivities of these mediators at beam-based neutrino experiments such as the finished ArgoNeuT, ongoing MicroBooNE, SBND, ICARUS, and the upcoming DUNE experiment. We realize that scalars are more enhanced while produced from three-body decay of charged mesons, especially if they are muonphilic in nature. For scenarios that contain muonphilic scalars, these experiments can probe unexplored regions of parameter space that can explain the current discrepancy in the anomalous magnetic moment of muons. The sensitivity of electrophilic scalars at the DUNE Near Detector can explore new regions. We also show that Bethe-Heitler scattering processes can be used to probe flavor-specific lepton final states even for the mediator masses below twice the lepton mass.
Background
In preparation of future clinical trials employing the Mobetron electron linear accelerator to deliver FLASH Intraoperative Radiation Therapy (IORT), the development of a Monte Carlo (MC)‐based framework for dose calculation was required.
Purpose
To extend and validate the in‐house developed fast MC dose engine MonteRay (MR) for future clinical applications in IORT.
Methods
MR is a CPU MC dose calculation engine written in C++ that is capable of simulating therapeutic proton, helium, and carbon ion beams. In this work, development steps are taken to include electrons and photons in MR are presented. To assess MRs accuracy, MR generated simulation results were compared against FLUKA predictions in water, in presence of heterogeneities as well as in an anthropomorphic phantom. Additionally, dosimetric data has been acquired to evaluate MRs accuracy in predicting dose‐distributions generated by the Mobetron accelerator. Runtimes of MR were evaluated against those of the general‐purpose MC code FLUKA on standard benchmark problems.
Results
MR generated dose distributions for electron beams incident on a water phantom match corresponding FLUKA calculated distributions within 2.3% with range values matching within 0.01 mm. In terms of dosimetric validation, differences between MR calculated and measured dose values were below 3% for almost all investigated positions within the water phantom. Gamma passing rate (1%/1 mm) for the scenarios with inhomogeneities and gamma passing rate (3%/2 mm) with the anthropomorphic phantom, were > 99.8% and 99.4%, respectively. The average dose differences between MR (FLUKA) and the measurements was 1.26% (1.09%). Deviations between MR and FLUKA were well within 1.5% for all investigated depths and 0.6% on average. In terms of runtime, MR achieved a speedup against reference FLUKA simulations of about 13 for 10 MeV electrons.
Conclusions
Validations against general purpose MC code FLUKA predictions and experimental dosimetric data have proven the validity of the physical models implemented in MR for IORT applications. Extending the work presented here, MR will be interfaced with external biophysical models to allow accurate FLASH biological dose predictions in IORT.
Quantum electrodynamic (QED) plasmas, describing the intricate interplay of strong-field QED and collective pair plasma effects, play pivotal roles in astrophysical settings like those near black holes or magnetars. However, the creation of observable QED plasmas in laboratory conditions was thought to require ultra-intense lasers beyond the capabilities of existing technologies, hindering experimental verification of QED plasma theories. This paper provides a comprehensive review of recent studies outlining a viable approach to create and detect observable QED plasmas by combining existing electron beam facilities with state-of-the-art lasers. The collision between a high-density 30 GeV electron beam and a 3 PW laser initiates a QED cascade, resulting in a pair plasma with increasing density and decreasing energy. These conditions contribute to a higher plasma frequency, enabling the observation of ∼0.2% laser frequency upshift. This solution of the joint production-observation problem should facilitate the near-term construction of ultra-intense laser facilities both to access and to observe the realm of strong-field QED plasmas.
The advent of high-power ultra-short laser pulses opens up new frontiers of relativistic non-linear optics, high energy density physics and laboratory astrophysics. As the laser electric field in the particle rest frame approaches the Schwinger field $$E_{cr} = 1.3 \times 10^{18}\,\textrm{V} \textrm{m}^{-1}$$ E cr = 1.3 × 10 18 V m - 1 , the laser interaction with matter enters into the quantum electrodynamics (QED) dominated regime, where extremely rich non-linear phenomena take place, such as a violent acceleration of charged particles, copious lepton pair production, and ultra-brilliant X/ $$\gamma$$ γ -ray emission. Among them, X/ $$\gamma$$ γ -ray emission based on the laser-plasma is generally characterized by large photon flux, high brilliance, small source size, and high photon energy, which can even annihilate into lepton pairs by colliding with photons. Though various schemes have been proposed for bright high-energy photon emission and lepton generation and acceleration, many predictions remain to be confirmed and thoroughly tested in experiments. In this review, we introduce recent advances in bright X/ $$\gamma$$ γ -ray radiation and lepton pair generation in the QED regime by the interaction of relativistic intense lasers with various plasma targets. The characteristics of the radiation and secondary particles generated via these schemes are summarized, and the experimental progresses are elaborated.
Обобщаются и дополняются результаты оригинальной работы полувековой давности с участием автора, в которой впервые был описан нелинейный эффект излучения фотонов переменным электромагнитным полем.
In the quasistatic regimes of nonlinear Breit-Wheeler and trident pair creation, the rates can exhibit a nonanalytic dependency on the fundamental coupling of quantum electrodynamics, in a form similar to Schwinger vacuum pair creation. To reach this tunneling regime requires satisfying competing requirements: a high-intensity but low quantum strong-field parameter with sufficient pair creation to be observed. Using a locally monochromatic approach, we identify the parameter regime where tunneling pair creation could be measured in experiment. Studying several scenarios of collisions with focused Gaussian pulses, including a bremsstrahlung and an inverse Compton source for nonlinear Breit-Wheeler and a Gaussian electron beam for nonlinear trident, we find the position of the tunneling parameter regime to be well defined and robust.
During the ultraintense laser interaction with solids (overdense plasmas), the competition between two possible quantum electrodynamics (QED) mechanisms responsible for e± pair production, i.e., linear and nonlinear Breit-Wheeler (BW) processes, remains to be studied. Here, we have implemented the linear BW process via a Monte Carlo algorithm into the QED particle-in-cell (PIC) code yunic, enabling us to self-consistently investigate both pair production mechanisms in the plasma environment. By a series of two-dimensional QED-PIC simulations, the transition from the linear to the nonlinear BW process is observed with the increase of laser intensities in the typical configuration of a linearly polarized laser interaction with solid targets. A critical normalized laser amplitude about a0∼400–500 is found under a large range of preplasma scale lengths, below which the linear BW process dominates over the nonlinear BW process. This work provides a practicable technique to model linear QED processes via integrated QED-PIC simulations. Moreover, it calls for more attention to be paid to linear BW pair production in near future 10-PW-class laser-solid interactions.
High energy photons, or \(\gamma \)-rays, were among the very first probes used to induce fission. Their significant impact in this field is due to particular properties of the \(\gamma \)-rays, such as the lack of a Coulomb barrier and the low, well-defined angular momentum transfer, but also to the variety of \(\gamma \)-ray sources developed over the years. This variety, going from simple but intense bremsstrahlung beams, through complex virtual photon excitations, to high resolution monochromatic sources of several types, gave rise to extensive photo-fission research programs. The review presents the evolution over more than 80 years of the methodology and instrumentation used in photo-fission experiments. The most important developments in fundamental and applied science are summarized and discussed. The main improvements necessary for the progression of this field into the age of nuclear photonics are outlined.
Finite-energy particles in free fall can collide with diverging center-of-mass energy near rapidly rotating black holes. What are the most salient observational signatures of this remarkable geometric effect? Here we revisit the problem from the standpoint of the near-horizon extreme Kerr geometry, where these collisions naturally take place. It is shown that the ingoing particle kinematics admits a simple, universal form. Given a scattering cross section, determination of emission properties is reduced to evaluation of particular integrals on the sky of a near-horizon orbiting particle. We subsequently apply this scheme to the example of single-photon bremsstrahlung, substantiating past results which indicate that ejected particles are observable, but their energies are bounded by the rest masses of the colliding particles. Our framework is readily applicable for any scattering process.
The bremsstrahlung cross section is calculated at leading order for polarized beams of electrons and ions, which is needed for luminosity measurements at the upcoming Electron Ion Collider (EIC). Analytic expressions, differential in the emitted photon energy and polar angle, are derived. The component of the cross section which depends on the beam polarizations is found to be highly suppressed with respect to the unpolarized Bethe–Heitler component, owing to the low \(q^2\) that characterizes the bremsstrahlung process.
The transformation of electromagnetic energy into matter represents a fascinating prediction of relativistic quantum electrodynamics that is paradigmatically exemplified by the creation of electron-positron pairs out of light. However, this phenomenon has a very low probability, so positron sources rely instead on beta decay, which demands elaborate monochromatization and trapping schemes to achieve high-quality beams. Here, we propose to use intense, strongly confined optical near fields supported by a nanostructured material in combination with high-energy photons to create electron-positron pairs. Specifically, we show that the interaction between near-threshold γ-rays and polaritons yields higher pair-production cross sections, largely exceeding those associated with free-space photons. Our work opens an unexplored avenue toward generating tunable pulsed positrons from nanoscale regions at the intersection between particle physics and nanophotonics.
Precisely determining the energy and species of charged particles is fundamental to the field of high energy physics. Technical breakthroughs, ingenuity, and improved detector designs have led to remarkable achievements. High energy physics detectors are advanced composite devices with millions of channels of different detector technologies often positioned in strong magnetic fields. While exquisite in design and measurement capabilities, these detection platforms require significant investments in electrical, technical and engineering resources. This design paradigm is not feasible for space applications where size, weight, and power resources are extremely limited. During the infancy of space exploration, many anomalies and even total mission failures of operational satellites were observed. Although it is hard to be certain, it is believed that many of these were the victims of the harsh radiation environment surrounding the Earth. Therefore, an understanding of the natural space radiation environment is not only a scientific endeavor, but a necessity for successful operations of space systems. While the particles in space are like those measured with colliders on Earth, the task of measuring them faces significantly harsher restrictions. Although the access to space has improved in recent times and the cost per kilogram to orbit is lower, about $3000 per kilogram compared to about $60,000 per kilogram during shuttle times, it is still a significant factor to consider when designing detectors. A brief history of particle detection in space, its miniaturization overcoming weight and power restrictions culminating in the usage of pixel detectors will be discussed in the following chapter.
Most of the realistic kinetic calculations for tokamak plasmas require now to incorporate the effect of partially ionized high-Z elements arising either from uncontrolled influxes of metallic impurities like tungsten in high input power regimes or from mitigation of runaway electrons generated after possible major disruptions by massive gas injection. The usual electron-ion Fokker-Planck collision operator must be therefore modified, since all atoms in the plasma are not fully ionized, as it can be considered for light elements. This represents a challenge, in order to perform fast but also accurate calculations, regardless the types of elements present in the plasma, but also their local levels of ionization, while covering a wide range of electron energies in a consistent way, from keV to tens of MeV in plasmas whose electron temperature may itself vary from few eV to several keV. In this context, a unified description of the atomic models is proposed, based on a multi-Yukawa representation of the electrostatic potential calibrated against results obtained by advanced quantum calculations. Besides the possibility to improve the description of inner and outer atomic shells in the determination of the atomic form factor, this model allows to derive analytical formulations for both elastic and inelastic scattering which can be then easily incorporated in kinetic calculations. The impact of the number of exponentials in the description of the atomic potential is discussed, and the comparison with simple or advanced atomic models is also performed.
The meteorological conditions required for the production of Terrestrial Gamma‐ray Flashes (TGFs) are not well understood. Particularly, the link between TGF production, meteorology, and weather severity is poorly characterized with most works focusing on only a small set of TGF events or isolated storms. This work is a further step toward understanding the general context of the meteorological conditions required for TGF production and if it differs from regular lightning production. We use TGFs observed from AGILE, ASIM, Fermi, and RHESSI to generate the largest catalog of TGFs with associated lightning sferics from either the World Wide Lightning Location Network (WWLLN) or Global Lightning Detection (GLD) combined with geostationary satellite images and meteorological conditions derived from ERA5 reanalysis data. In total we analyze 1582 TGF events and contextualize them in comparison to lightning flashes as characterized by ASIM. In our analysis we consider the proportion of TGFs and lightning coming from systems with overshooting tops as well as the Cloud Top Temperature (CTT) and the Convective Available Potential Energy (CAPE). Our results are consistent with previous studies, finding that TGFs observed from space come from primarily higher cloud tops than regular lightning flashes do. We find that CAPE and the proportion of cells with overshooting tops is similar for both TGF and lightning producing cells. It suggests that TGF observations from space are biased toward systems with higher cloud tops because the attenuation of the gamma‐rays from lower altitude TGFs reduce their intensity below the detection level of LEO instruments.
ResearchGate has not been able to resolve any references for this publication.