The Bethe-Heitler formula describes bremsstrahlung and it's a typical and important example in quantum electromagnetic dynamics (QED). This formula is widely applied in many branches of physics and astrophysics. We find that the integrated bremsstrahlung cross section at the static approximation and high energy limit has an unexpected big increment, which is missed by previous bremsstrahlung theory. This anomalous effect also exists in electron-positron pair creation. We derive the relating formulas and point out that electromagnetic cascades at the top of atmosphere can test this effect.
The bremsstrahlung cross section of electron in the atomic electric field is re-derived using the time ordered perturbative theory. The results are compared with the Bethe-Heitler formula. We indicate that both the TOPT-description and a soft version for the bremsstrahlung process predict a strong screening parameter-dependent cross section, which is missed by previous bremsstrahlung theory.
We calculate the Bethe-Heitler cross section for the production of lepton pairs in the field of a longitudinally polarized nucleon, taking into account the lepton masses and the target mass. This process is a dominant background to the detection of open charm from semi-leptonic decay modes, which is a potential probe of the polarized gluon distribution in the nucleon.
We derived analytic formulae for the polarization single--spin asymmetries (SSA) in the Bethe--Heitler process $e^- + p \to e^- + γ+ p$. The asymmetries arise due to one-loop QED radiative corrections to the leptonic part of the interaction and present a systematic correction for the studies of virtual Compton Scattering on a proton through interference with the Bethe-Heitler amplitude. Considered are SSA with either longitudinally polarized electron beam or a polarized proton target. The computed effect appears to be small, not exceeding 0.1 per cent for kinematics of current virtual Compton …
We present prospects and requirements for the study at HERA of hard photon processes which generate high $p_T$ photons in the final state, and processes which generate Drell-Yan lepton pairs.
I describe a five-dimensional, polarised, Bethe-Heitler event generator of $γ$-ray conversions to $μ^+μ^-$, based on a generator for conversion to $e^+e^-$ developed in the past. Verifications are performed from close-to-threshold to high energies.
Nonlinear Bethe-Heitler process in a bichromatic laser field is investigated using strong-field QED formalism. Symmetry properties of angular distributions of created $e^-e^+$ pairs are analyzed. These properties are showed to be governed by a behavior of the vector potential characterizing the laser field, rather than by the respective electric field component.
We develop the full finite lepton mass formalism for the production of real photons via the Bethe-Heitler reaction of unpolarized leptons off unpolarized nucleons. Genuine lepton mass effects are described, in particular their dependence upon the lepton mass and the initial beam energy, as well as their sensitivity to the nucleon isospin. In the minimum momentum transfer region, these effects dominate the muon induced proton cross section and become significant for electron scattering at small $x_B$.
The cross-section for the process $γ+ A \to μ^+ + μ^- + X$ is studied where the photon energy is of the order of several hundreds of GeV and where one of the leptons is scattered to large angles. This is of practical importance for muon shielding calculations at future linear electron colliders. In addition to the photon pole contribution which was previously considered especially by Y.S.Tsai, we identify another component due to the muon pole (equivalent photon and equivalent muon approximation). This is discussed following the usual Bethe-Heitler formula. Then we give practically useful form…
We study the electromagnetic Bethe-Heitler type contribution to neutrino-induced deeply virtual meson production (\nuDVMP). Such O(α_{em})-corrections decrease with Q^{2} in the Bjorken regime less steeply than the standard \nuDVMP handbag contribution. Therefore, they are relatively enhanced at high Q^{2}. The Bethe-Heitler terms give rise to an angular correlation between the lepton and hadron scattering planes with harmonics sensitive to the real and imaginary parts of the DVMP amplitude. These corrections constitute a few percent effect in the kinematics of the forthcoming Minerva experime…
The creation of lepton pairs ($e^+e^-$ and $μ^+μ^-$) via multiphoton absorption in collisions of ultrarelativistic ion beams with ultrashort high-frequency laser pulses is considered. Both the free and the bound-free production channels are addressed, where in the latter case the negatively charged lepton is created in a bound atomic state. It is shown that these nonlinear QED processes are observable when a table-top source of intense xuv or x-ray laser radiation is operated in conjunction with the LHC. We discuss the relative effectiveness of protons versus Pb ions and specify for each pair …
The nonperturbative regime of electron-positron pair creation by a relativistic proton beam colliding with a highly intense bichromatic laser field is studied. The laser wave is composed of a strong low-frequency and a weak high-frequency mode, with mutually orthogonal polarization vectors. We show that the presence of the high-frequency field component can strongly enhance the pair-creation rate. Besides, a characteristic influence of the high-frequency mode on the angular and energy distributions of the created particles is demonstrated, both in the nuclear rest frame and the laboratory fram…
We study the creation of electron-positron pairs in the superposition of a nuclear Coulomb field and a two-color laser field of high intensity. Our focus lies on quantum interference effects, which may arise if the two laser frequencies are commensurable. We show that the interference manifests in the angular distributions of the created particles, which are discussed in the nuclear rest frame and the laboratory frame. Additionally, we demonstrate that the total pair-production rates can be affected by interference and identify the relative phase between the two laser modes, which optimizes th…
We describe a new version of the 5D, exact, polarised, Bethe-Heitler event generator of $γ$-ray conversions to $e^+e^-$, developed in the context of the HARPO project, that is able to simulate successive events with different photon energies and on different atomic targets without any substantial CPU overhead. The strong correlation between kinematic variables in the divergence of the five-dimensional differential cross section are mitigated by performing each step of the conversion in the appropriate Lorentz frame. We extend the verification range down to 1 keV above threshold and up to 1 EeV…
We investigate electron-positron pair creation in the interaction of a nuclear Coulomb field and a highly intense two-mode laser field. For bichromatic laser fields, we examine the differences arising for commensurable and incommensurable frequencies in a continuous variation of the laser frequency ratio and the quantum interference effects, which may occur in the commensurable case. We show that the interference manifests in the angular distributions and the total pair-production rates of the created particles. Additionally, by varying the amplitudes of the two modes we study pair creation in…
Three-qubit entanglement in the Bethe-Heitler process
Northwestern University（西北大学）；Stony Brook University（纽约州立大学石溪分校）；Brookhaven National Laboratory（布鲁克海文国家实验室）；RIKEN BNL Research Center（理化学研究所布鲁克海文研究中心）；Technische Universität München（慕尼黑工业大学）
We report on the calculation of first-order QED corrections for the $γp\rightarrow l^+l^-p^{\prime}$ process. An upcoming experiment at MAMI (Mainz) aims to compare the cross sections of muon- and electron-pair production in this reaction to test lepton universality. Precise knowledge of the electromagnetic radiative corrections is needed for these measurements. As a first step, we present the leading QED radiative corrections in the soft-photon approximation when accounting for the finite lepton mass. For the kinematics at MAMI, we find corrections of the percent level for muons, and of order…
The ratio of di-lepton production cross sections on a proton, using the $γp\rightarrow l^+ l^- p$ process, above and below di-muon production threshold allows to extract the effective lepton-proton interaction, which is required to be identical for electrons and muons if lepton universality is exact. To test for a scenario of broken universality at the percent level, of the size which could explain the different proton charge radii extracted from electron scattering and from muonic hydrogen spectroscopy, we evaluate all one-loop QED corrections to this process, including the full lepton mass d…
A precise measurement of the spectrum of the photons from $ep$ bremsstrahlung with the ZEUS luminosity monitor at HERA is reported. The measurement shows a reduced rate compared to the Bethe-Heitler spectrum for photon energies below 5~GeV. This suppression, called the beam-size effect, is explained by the finite transverse size of the beam overlap relative to the typical impact parameter in the process of $ep$ bremsstrahlung at HERA energies.
Based on the proposed representation of the Mott corrections to the Bethe stopping formula in the form of rapidly convergent series of quantities bilinear in the Mott partial amplitudes, the numerical calculations were performed for these corrections over a wide range of nuclear charge number of the incident particles at various values of their relative velocity.
Understanding the physical world is a continuous process of trial and error. It requires theoretical background and tools to find out the theory's accuracy. Particles motion through matter, and their energy loss is one such process. Testing the energy loss requires the development of a tool capable of simulating and testing theoretical predictions using data. For this very reason, researchers developed a Monte-Carlo based simulation toolkit, the Geant4 project. A multi-purpose toolkit to explore the nature of collisions and energy loss of particles. Uses of Geant4 are in fields where particle …
Induced soft gluon bremsstrahlung associated with multiple collisions is calculated via perturbative QCD. We derive the non-abelian analog of the Landau-Pomeranchuk effect that suppresses induced soft radiation with formation times exceeding the mean free path, $λ$. The dependence of the suppression effect on the $SU(N)$ representation of the jet parton as well as the kinematic variables is expressed through a radiation formation factor. Unlike in QED, the finite contribution from the small $x$ regime in QCD leads to an approximately constant radiative energy loss per unit length, $dE/dz\propt…
