Pair Production Rate Research Articles

Numerical approach to the semiclassical method of pair production for arbitrary spins and photon polarization

In this paper we show how to recast the results of the semiclassical method of Baier, Katkov & Strakhovenko for pair production, including the possibility of specifying all the spin states and photon polarization, in a form that is suitable for numerical implementation. In this case, a new type of integral appears in addition to the ones required for the radiation emission process. We compare the resulting formulas with those obtained for a short pulse plane wave external field by using the Volkov state. We investigate the applicability of the local constant field approximation for the proposed upcoming experiments at FACET II at SLAC and LUXE at DESY. Finally, we provide results on the dependence of the pair production rate on the relative polarization between a linearly polarized laser pulse and a linearly polarized incoming high energy photon. We observe that even in the somewhat intermediate intensity regime of these experiments, there is roughly a factor of $2$ difference between the pair production rates corresponding to the two relative photon polarizations, which is of interest in light of the vacuum birefringence of QED.

Dimensionality-Driven Photoproduction of Massive Dirac Pairs near Threshold in Gapped Graphene Monolayers.

Generation of quasiparticle-hole pairs in gapped graphene monolayers in the combined field of two counterpropagating light waves is studied. The process represents an analog of electron-positron pair production from the vacuum of quantum electrodynamics (QED) by the Breit-Wheeler effect. We show, however, that the two-dimensional structure of graphene causes some striking differences between both scenarios. In particular, contrary to the QED case, it allows for nonzero pair production rates at the energy threshold when the Breit-Wheeler reaction proceeds nonlinearly with absorption of three photons.

Lefschetz-thimble inspired analysis of the Dykhne–Davis–Pechukas method and an application for the Schwinger Mechanism

Dykhne–Davis–Pechukas (DDP) method is a common approximation scheme for the transition probability in two-level quantum systems, as realized in the Landau–Zener effect, leading to an exponentially damping form comparable to the Schwinger pair production rate. We analyze the foundation of the DDP method using a modern complex technique inspired by the Lefschetz-thimble method. We derive an alternative and more adaptive formula that is useful even when the DDP method is inapplicable. As a benchmark, we study the modified Landau–Zener model and compare results from the DDP and our methods. We then revisit a derivation of the Schwinger Mechanism of particle production under electric fields using the DDP and our methods. We find that the DDP method gets worse for the Sauter type of short-lived electric pulse, while our method is still a reasonable approximation. We also study the Dynamically Assisted Schwinger Mechanism in two methods.

On D-brane interaction & its related properties

We compute the closed-string cylinder amplitude between one Dp brane and the other Dp′ brane, placed parallel at a separation, with each carrying a general constant worldvolume flux and with p−p′=0,2,4,6 and p≤6. For the p=p′, we show that the main part of the amplitude for p=p′<5 is a special case of that for p=p′=5 or 6 case. For all other p−p′=2,4,6 cases, we show that the amplitude is just a special case of the corresponding one for p=p′ case. Combined both, we obtain the general formula for the amplitude, which is valid for each of the cases considered and for arbitrary constant worldvolume fluxes. The corresponding general open string one-loop annulus amplitude is also obtained by a Jacobi transformation of the general cylinder one. We give also the general open string pair production rate. We study the properties of the amplitude such as the nature of the interaction, the open string tachyonic instability, and the possible open string pair production and its potential enhancement. In particular, in the presence of pure magnetic fluxes or magnetic-like fluxes, we find that the nature of interaction is correlated with the existence of potential open string tachyonic instability. When the interaction is attractive, there always exists an open string tachyonic instability when the brane separation reaches the minimum determined by the so-called tachyonic shift. When the interaction is repulsive, there is no such instability for any brane separation. We also find that the enhancement of open string pair production, in the presence of pure electric fluxes, can occur only for the p−p′=2 case.

Schwinger pair production from Padé-Borel reconstruction

In this work, we show how the knowledge of the first few terms of the Euler-Heisenberg Lagrangian's weak-field expansion in a magnetic field background is enough to reconstruct the pair-production rate in a strong electric field background. To this end, we study its associated truncated Borel sum using Pad\'e approximants, as advocated in a recent work by Costin and Dunne, J. Phys. A52, 445205 (2019).

Lifetime and polarization for real and virtual correlated Stokes-anti-Stokes Raman scattering in diamond

The production of correlated Stokes (S) and anti-Stokes (aS) photons (SaS process) mediated by real or virtual phonon exchange has been reported in many transparent materials. In this work, we investigate the polarization and time correlations of SaS photon pairs produced in a diamond sample. We demonstrate that both S and aS photons have mainly the same polarization of the excitation laser. We also perform a pump-and-probe experiment to measure the decay rate of the SaS pair production, evidencing the fundamental diference between the real and virtual (phonon exchange) processes. In real processes, the rate of SaS pair production is governed by the phonon lifetime of $(2.8 \pm 0.3)$ ps, while virtual processes only take place within the time width of the pump laser pulses of approximately 0.2 ps. We explain the diference between real and virtual SaS processes by a phenomenological model, based on probabilities of phonon creation and decay.

Conditions for Vacuum Instability in Holographic Theories with Dilaton Field

We investigate the vacuum instability in the presence of dilaton field in a holographic setup. Although the dilaton is a bulk field, it leads to the vacuum instability on the boundary. We show that the whole process crucially depends on the probe brane position and as well on the radial coordinate so that the effects of dilaton scale parameter in different regions of the bulk or for different probe brane positions are different. We also observe that in our study, the temperature can strengthen the effect of scale parameter in reducing the potential barrier. Finally, we show that this Schwinger-like effect, although is interesting by itself, does not produce a considerable pair production rate.

D-brane interaction, the open string pair production and its enhancement plus its possible detection

This review article reports the recent studies, based on a series of publications by one of the present authors along with his collaborators, regarding the interaction between two D-branes, the open string pair production and its possible enhancement in Type II superstring theories. Specifically, computed is the interaction amplitude between two D-branes, placed parallel at a separation, with each carrying a general worldvolume constant flux, and discussed are the amplitude properties, say, the repulsive or attractive nature of the interaction. When at least one of the D-branes carries an electric flux, the interaction amplitude can have an imaginary part, reflecting the instability of the underlying system via the open string pair production. The decay rate and the pair production rate are both computed. In addition, the enhancement of the latter is found when the added electric and magnetic fluxes are correlated in both magnitude and direction in a certain manner. In particular, when one of the branes is D3 and the other is D1, the corresponding pair production rate becomes large enough to be tested in an earthbound laboratory. Note that the pair production rate is related to the brane separation along the direction transverse to both branes, therefore, to the extra-dimensions with respect to the brane observer. So if the underlying string theory is relevant and the D3 can be taken as our own 4-dimensional world, measuring, say, the electric current due to the pair production and comparing it against the added electric and magnetic fields to see if the measurements agree with the prediction of the computations. This can be used to verify the existence of extra-dimensions. Further, this provides also a potential new means to test the underlying string theory without the need of compactifying it to four dimensions.

Search for Physics beyond the Standard Model in Events with Overlapping Photons and Jets.

Results are reported from a search for new particles that decay into a photon and two gluons, in events with jets. Novel jet substructure techniques are developed that allow photons to be identified in an environment densely populated with hadrons. The analyzed proton-proton collision data were collected by the CMS experiment at the LHC, in 2016 at sqrt[s]=13 TeV, and correspond to an integrated luminosity of 35.9 fb^{-1}. The spectra of total transverse hadronic energy of candidate events are examined for deviations from the standard model predictions. No statistically significant excess is observed over the expected background. The first cross section limits on new physics processes resulting in such events are set. The results are interpreted as upper limits on the rate of gluino pair production, utilizing a simplified stealth supersymmetry model. The excluded gluino masses extend up to 1.7TeV, for a neutralino mass of 200GeV and exceed previous mass constraints set by analyses targeting events with isolated photons.

On‐the‐Fly Calculation of Absorbed and Equivalent Atmospheric Radiation Dose in A Water Phantom with the Atmospheric Radiation Interaction Simulator (AtRIS)

AbstractComputation of the ionization and radiation dose in arbitrary (exo‐) planetary atmospheres due to energetic particles is recently becoming more important due to several reasons that are either correlated with the detection of trace gases for life on exoplanets or with computing dose rates at arbitrary altitudes in the Earth atmosphere. We previously presented Atmospheric Radiation Interaction Simulator, a new Geant4‐based code tailored specifically to enable parametric studies of radiation propagation through exoplanetary atmospheres (Banjac et al., 2019 https://doi.org/10.1029/2018JA026042). Therein, the calculation of ion‐electron pair production rates, which are a mandatory input for chemical and atmospheric modeling, has been presented and validated against Earth measurements and also other, similar, but solar‐system‐specific Geant4‐based codes (PLANETOCOSMICS). In addition to providing input for atmospheric modeling of exoplanets, with AtRIS we aim to directly characterize the habitability by calculating the absorbed dose. In this technical validation study, after showing a detailed analysis of the secondary particles contributing to the atmospheric radiation, we describe a feature of the code which makes direct parametric studies of the interrelation of incident radiation and the resulting absorbed dose throughout the atmosphere possible. In a validation case study configured using an atmospheric model obtained with NRLMSISE‐00 and a primary proton and helium GCR flux calculated using a recent improvement of the force‐field approach, we have compared simulation results with measurements obtained with the Flight Radiation Environment Detector (FRED). We show that Atmospheric Radiation Interaction Simulator (AtRIS) can reproduce the measured dose rate dependence on altitude.

Transient and pretransient stages in a field induced phase transition of the vacuum state

Evolution of modulus and phase of complex order parameter associated with field induced phase transition (FIPT) of the vacuum state interacting with time dependent Sauter pulse is studied to analyse different evolution stages of the order parameter e.g., quasi electron positron plasma (QEPP), transient, and residual electron-positron plasma (REPP) stages. By revisiting FIPT in presence of single-sheeted and multi-sheeted pulses, we attribute the transient stage to the nonlinear coupling in the differential equations governing the dynamics of the phase and the modulus of the order parameter. The appearance of the rapid oscillations in the modulus is shown to be associated with the abrupt change in the phase of the order parameter in the transient stage. FIPT is also studied for multi-sheeted Sauter pulse with linear and quadratic frequency chirp. QEEP stage is found to show complex dynamical behaviour with fast and irregular oscillations due to the frequency chirp. The formation of pre-transient region due to the quadratic frequency chirping is observed in the accelerating part of the QEPP stage before the electric field attains the maximum value. As the quadratic chirp is increased the pre-transient and transient stages move closer to the electric field maximum which leads to a decrease in temporal separation between the two stages. The early appearance of the transient stage and hence of the following REPP stage results in the enhancement of pair production rate.

Magnetic field and curvature effects on pair production. II. Vectors and implications for chromodynamics

We calculate the pair production rates for spin-$1$ or vector particles on spaces of the form $M \times {\mathbb R}^{1,1}$ with $M$ corresponding to ${\mathbb R}^2$ (flat), $S^2$ (positive curvature) and $H^2$ (negative curvature), with and without a background (chromo)magnetic field on $M$. Beyond highlighting the effects of curvature and background magnetic field, this is particularly interesting since vector particles are known to suffer from the Nielsen-Olesen instability, which can dramatically increase pair production rates. The form of this instability for $S^2$ and $H^2$ is obtained. We also give a brief discussion of how our results relate to ideas about confinement in nonabelian theories.

Magnetic field and curvature effects on pair production. I. Scalars and spinors

The pair production rates for spin-zero and spin-$\frac{1}{2}$ particles are calculated on spaces of the form $M \times {\mathbb R}^{1,1}$ with $M$ corresponding to ${\mathbb R}^2$ (flat), $T^2$ (flat, compactified), $S^2$ (positive curvature) and $H^2$ (negative curvature), with and without a background magnetic field on $M$. The motivation is to elucidate the effects of curvature and background magnetic field. Contrasting effects for positive and negative curvature on the two cases of spin are obtained. For positive curvature, we find enhancement for spin-zero and suppression for spin-$\frac{1}{2}$, with the opposite effect for negative curvature.

Calculating non-perturbative quantities through the world-line formalism

We present two applications of the world-line formalism to the calculation of non-perturbative quantities in QCD. The first quantity is the free energy of the gluon plasma in the high-temperature limit; the second quantity is the pair-production rate in the chromo-electric field of a flux tube. In the first case, where effects of spatial confinement in the dimensionally-reduced 3D Yang-Mills theory are primarily important, we calculate the free-energy density of a gluon propagating in the stochastic background fields through a suitable parametrization of the area-and the perimeter laws of the Wilson loop, which enters the corresponding one-loop effective action. In this way, we find that the order of the leading correction to the Stefan-Boltzmann free energy changes from for N ∼ 1 to for N ≫ 1, where λ is the finite-temperature’t Hooft coupling, and N is the number of colors. In the second case, we find that, in the London limit of the dual superconductor, the Schwinger pair-production rate, ∼ e−const·m2, goes over to e−const·m. Given that the flux-tube field is static, we find such a conversion of the Gaussian distribution into an exponential one, remarkable.

Quantum Electrodynamics Actions in Supercritical Fields

In the in-out formalism, we advance a new method to represent the gamma function for quantum electrodynamics (QED) actions in supercritical fields, which is complementary to the proper-time integral representation in Phys. Rev. D 78, 105013 (2008) and Phys. Rev. D 84, 065004 (2011). The new method directly yields the QED action in terms of the Hurwitz zeta function in a constant magnetic field and the complex QED action in a constant electric field. The complex action exactly gives the vacuum polarization and the vacuum persistence and thereby the pair-production rate in the electric field. The QED actions exhibit electromagnetic duality.

Wigner function and pair production in parallel electric and magnetic fields

We derive analytical formulas for the equal-time Wigner function in an electromagnetic field of arbitrary strength. While the magnetic field is assumed to be constant, the electric field is assumed to be space-independent and oriented parallel to the magnetic field. The Wigner function is first decomposed in terms of the so-called Dirac-Heisenberg-Wigner (DHW) functions and then the transverse-momentum dependence is separated using a new set of basis functions which depend on the quantum number $n$ of the Landau levels. Equations for the coefficients are derived and then solved for the case of a constant electric field. The pair-production rate for each Landau level is calculated. In the case of finite temperature and chemical potential, the pair-production rate is suppressed by Pauli's exclusion principle.

Observation of nonlinear interference on a silicon photonic chip.

Photonic integrated circuits represent a promising platform for applying quantum information science to areas such as quantum computation, quantum communication, and quantum metrology. While the linear optical approach has greatly contributed to this field, it is often possible to improve the functionality and scalability by making use of nonlinear processes. One interesting phenomenon is the interference between two nonlinear optical processes, where the interference occurs by removing the information as to which of two processes have occurred. In this Letter, we demonstrate a nonlinear interferometer in the pair-photon generation regime by using spontaneous four-wave mixing in an integrated silicon photonic chip. We observe a nonlinear interference in the production rate of photon pairs generated from two different four-wave mixing waveguides. We obtain an interference visibility of 96.8%. This work shows the possibility of integrating and controlling nonlinear-optical-interference components for silicon quantum photonics.

Measuring the boiling point of the vacuum of quantum electrodynamics

It is a long-standing non-trivial prediction of quantum electrodynamics that its vacuum is unstable in the background of a static, spatially uniform electric field and, in principle, sparks with spontaneous emission of electron-positron pairs. However, an experimental verification of this prediction seems out of reach because a sizeable rate for spontaneous pair production requires an extraordinarily strong electric field strength $|\mathbf E|$ of order the Schwinger critical field, ${\rm E}_c=m_e^2/e\simeq 1.3\times 10^{18}\ {\rm V/m}$, where $m_e$ is the electron mass and $e$ is its charge. Here, we show that the measurement of the rate of pair production due to the decays of high-energy bremsstrahlung photons in a high-intensity laser field allows for the experimental determination of the Schwinger critical field and thus the boiling point of the vacuum of quantum electrodynamics.

Remark on the open string pair production enhancement

Recent studies by one of the present authors along with his collaborators in [1–4] show that there exist the so-called open string pair production for a possible simplest system of two Dp branes, placed parallel at a separation and with each carrying different electric flux, in Type II superstring theories. Further this pair production can be greatly enhanced when a magnetic flux, sharing no common field strength index with the electric one, is added, implying then p≥3. Given this, one may wonder if further enhancement can be achieved by adding more magnetic flux(es) in a similar fashion. In this paper, we explore this possibility. It turns out that adding more such magnetic flux diminishes rather than enhances the pair production rate. This actually implies that the largest enhancement occurs at p=3 when the same realistic electric and magnetic fluxes are applied for all p≥3. Curiously one of D3 branes may be our own world and if so, the enhancement gives a possible opportunity to detect the pair production, therefore to test the underlying string theories.

The Atmospheric Radiation Interaction Simulator (AtRIS): Description and Validation

AbstractWe present the Atmospheric Radiation Interaction Simulator (AtRIS), a newly developed GEANT4‐based code tailored specifically to enable parametric studies of radiation propagation through various (exo)planetary atmospheres. Its main purpose is to model the altitude‐dependent atmospheric secondary particle environment and to calculate the ion pair production rates, which are a mandatory input for atmospheric chemistry models in order to, for example, directly characterize the habitability of the modeled planet. Similar codes have been developed previously (e.g., PLANETOCOSMICS; Desorgher, et al., ); however, until now, none possesses the necessary flexibility in the specification of the atmosphere and the regolith that is necessary to model planets outside our solar system. Here we provide a detailed description of AtRIS and its validation against earthbound measurements. For validation, we show comparisons against Earth measurements. Thereby, the focus is on the atmospheric altitude‐dependent ionization, the surface muon, and the neutron fluxes, as well as the primary proton fluxes. Furthermore, a comparison of the computed energy losses of monoenergetic protons based on AtRIS and PLANETOCOSMICS is shown. Our aim is to demonstrate the validity of AtRIS and its importance for future studies on, for example, potential (Earth‐like) exoplanets.