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Dynamically assisted pair production for scalar QED by two fields

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Frontiers of physics 2015年第2期10卷 35-40页

作者： Zi-Liang Li Ding Lu bai-song xie Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education and College of Nuclear Science and Technology Beijing Normal University Beijing 100875 China Beijing Radiation Center Beijing 100875 China

By solving the quantum Vlasov equation, the dynamically assisted pair production for scalar quantum electrodynamics （QED） is investigated. It is verified that this mechanism still holds true for boson pair production. Two combinations of two electric fields having different time scales under various time delays are considered; it is found that the oscillations of the momentum spectrum and the number density of created bosons decrease with increasing time delay, and the latter has a maximum value when the time delay equals zero. Furthermore, the differences in vacuum pair production between bosons and fermions are also studied, and they are helpful for distinguishing the created bosons from fermions.

关键词： quantum Vlasov equation dynamically assisted pair production scalar QED

Electron-positron pair production in a strong asymmetric laser electric field

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Frontiers of physics 2014年第2期9卷 157-163,F0004页

作者： Obulkasim Oluk bai-song xie Muhmmad Ali Bake SayipjamalDulat School of Physics Science and Technology Xinjiang University Urumqi 830046 China College of Nuclear Science and Technology Beijing Normal University Beijing 100875 China

By solving the quantum Vlasov equation, electron positron pair production in a strong electric field with asymmetric laser pulses has been investigated. We consider three different situations of subcycle, cycle and supercycle laser pulses. It is found that in asymmetric laser pulse field, i.e.. when the pulse length of one rising or falling side is fixed while the pulse length of the other side is changed, the pair production rate and mnnber density can be significantly modified comparable to symmetric situation. For each ca,se of these three different cycle pulses, when one side pulse length is constant and the other side pulse length becomes shorter, i.e., the whole pulse is compressed, the more pairs can be produced than that in tile vice versa case, i.e., the whole pulse is elongated. In compressed pulse case there exists an optimum pulse length ratio of asylnmetric pulse lengths which makes the pair number density maximunn. Moreover, the created maximum pair number density by subcycle pulse is larger than that by cycle or/and supercycle pulse. In elongated pulse case, however, only for supercycle laser pulse the created pairs is enhanced and there exists also an optimum asymmetric pulse length ratio that maximizes the pair number density. On the other hand. surprisingly, in both cases of subcycle and cycle elongated laser pulses, the pair number density is monotonically decreasing as the asymmetry of pulse increases.

关键词： electron-positron pair production quantum Vlasov equation (QVE) asymmetric laserelectric field

Enhanced electron–positron pair production by frequency chirping in one-and two-color laser pulse fields

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Chinese Physics B 2017年第2期26卷 48-55页

作者： Nuriman Abdukerim Zi-Liang Li bai-song xie College of Nuclear Science and Technology Beijing Normal University Beijing 100875 China School of Physics and Technology Xinjiang University Urumqi 830046 China School of Science China University of Mining and Technology Beijing 100083 China Beijing Radiation Center Beijing 100875 China

Enhanced electron–positron pair production by frequency chirping in one- and two-color laser pulse fields is investigated by solving the quantum Vlasov equation. A small frequency chirp shifts the momentum spectrum along the momentum axis. The positive and negative frequency chirp parameters play the same role in increasing the pair number density. The sign change of the frequency chirp parameter at the moment t = 0 leads the pulse shape and momentum spectrum to be symmetric, and the number density to be increased. The number density of produced pairs in the two-color pulse field is much higher than that in the one-color pulse field and the larger frequency chirp pulse field dominates more strongly. In the two-color pulse fields, the relation between the frequency ratio of two colors and the number density is not sensitive to the parameters of small frequency chirp added in either a low frequency strong field or a high frequency weak field but sensitive to the parameters of large frequency chirp added in a high frequency weak field.

关键词： electron–positron quantum nonlocalization quantum Vlasov equation frequency chirping

Effect of symmetrical frequency chirp on pair production

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Chinese Physics B 2021年第6期30卷 96-105页

作者： Kun Wang Xuehua Hu Sayipjamal Dulat bai-song xie School of Physics and Technology Xinjiang UniversityUrumqi 830046China Key Laboratory of Beam Technology of the Ministry of Education and College of Nuclear Science and TechnologyBeijing Normal UniversityBeijing 100875China Beijing Radiation Center Beijing 100875China

By using Dirac–Heisenberg–Wigner formalism we study electron–positron pair production for linear, elliptic, nearly circular, and circular polarizations of electric fields with symmetrical frequency chirp, and we obtain momentum spectra and pair yield. The difference of results among polarized fields is obvious for the small chirp. When the chirp parameter increases, the momentum spectra tend to exhibit the multiphoton pair generation that is characterized by the multi-concentric ring structure. The increase of the number density is also remarkable compared to the case of asymmetrical frequency chirp. Note that the dynamically assisted Schwinger mechanism plays an important role for the enhanced pair production in the symmetrical frequency chirp.

关键词： pair production Dirac–Heisenberg–Wigner formalism symmetrical frequency chirp

Pair production in strong SU（2） background fields

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Frontiers of physics 2017年第5期12卷 143-150页

作者： Mo-Ran Jia Zi-Liang Li Chong Lv Feng Wan bai-song xie College of Nuclear Science and Technology Beijing Normal University Beijing 100875 China Beijing Radiation Center Beijing 100875 China

Fermion particle pair production in strong SU（2）-gauge chromoelectric fields is studied using the Boltzmann-Vlasov equation in a classical way. The existence of a preproduction process in a classical description is shown using the distribution evolution of non-Abelian particle production. It is interesting to find that the distribution of the particle number density is centered on two islands and shows a split on the color charge sphere as it evolves, ultimately reaching a steady state that is related to the amplitude and variation of the field.

关键词： pair production SU(2)-gauge chromoelectric field classical and semiclassical technique Boltzmann-Vlasov equation

Pair Production in Chromoelectric Field with Back Reaction

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Communications in Theoretical Physics 2018年第10期70卷 430-438页

作者： Mo-Ran Jia Feng Wan Chong Lv bai-song xie College of Nuclear Science and Technology Beijing Normal University Beijing 100875 China Beijing Radiation Center Beijing 100875 China

Massless quark pair production in SU(2) gauge chromoelectric field is investigated by solving the Wigner function with back reaction. The temporal evolution of specific field and its current are obtained self consistently. For the quark distribution function, both its time and momentum dependence are studied. In particular, some interesting phenomena are found, for example, the more abundant symmetry or/and antisymmetry characteristics, the existence of the attractive basin structure and the existence of the momentum "gap" in the quark distribution and so on. All the phenomena are associated with the quark-gluon plasma oscillation, which due to the back reaction effect. The study and analysis qualitatively about the components of the Wigner function are expected to be helpful to deepen the understanding of the QCD vacuum.

关键词： particle production in Non-Abelian gauge covariant Wigner function in Non-Abelian gauge Schwinger mechanism

Spatial Characteristics of Thomson Scattering Spectra in Laser and Magnetic Fields

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Chinese Physics Letters 2019年第7期36卷 34-38页

作者： Li Zhao Zhi-Jing Chen Hai-Bo Sang bai-song xie Key Laboratory of Beam Technology of the Ministry of Education and College of Nuclear Science and Technology Beijing Normal University Beijing 100875 Beijing Radiation Center Beijing 100875

Spatial characteristics of Thomson scattering spectra are studied for an electron moving in the circularly polarized laser field in the presence of a strong uniform magnetic field. The results show that the angular distributions of the spectra with respect to the azimuthal and polar angles exhibit different symmetries, respectively, which depend on the fields and electron parameters sensitively and significantly. Moreover, for relatively large parameters such as high laser intensity, high magnetic resonance parameter as well as large initial momentum of electron, the two lobes in spectra tend to the laser-propagating direction so that the radiation can be collimated in the forward direction. Furthermore, an important finding is that by choosing the appropriate fields and initial momentum of electron, the high frequency part of the Thomson scattering spectra can reach the frequency range of soft x-ray,in which a high radiation power per solid angle as ~10^11 a.u. can be obtained.

关键词： Spatial characteristics studied for an electron can be obtained

Reversed rotation of limit cycle oscillation and dynamics of low-intermediate-high confinement transition

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Chinese Physics B 2018年第6期27卷 292-297页

作者： Dan-Dan Cao Feng Wan Ya-Juan Hou Hai-Bo Sang bai-song xie College of Nuclear Science and Technology Beijing Normal UniversityBeijing 100875China Beijing Radiation Center Beijing 100875China

The dynamics of the confinement transition from L mode to H mode（LH） is investigated in detail theoretically via the extended three-wave coupling model describing the interaction of turbulence and zonal flow（ZF） for the first ***, turbulence is divided into a positive-frequency（PF） wave and a negative-frequency（NF） one, and the gradient of pressure is added as the auxiliary energy for the system. The LH confinement transition is observed for a sufficiently high input energy. Moreover, it is found that the rotation direction of the limit cycle oscillation（LCO） of PF wave and pressure gradient is reversed during the transition. The mechanism is illustrated by exploring the wave phases. The results presented here provide a new insight into the analysis of the LH transition, which is helpful for the experiments on the fusion devices.

关键词： limit cycle oscillation three-wave interaction confinement transition turbulence

Asymmetric pulse effects on pair production in polarized electric fields

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High Power Laser Science and Engineering 2020年第4期8卷 68-78页

作者： Obulkasim Olugh Zi-Liang Li bai-song xie Key Laboratory of Beam Technology of the Ministry of Education and College of Nuclear Science and TechnologyBeijing Normal UniversityBeijing 100875China Xinjiang Police College Urumqi 830011China School of Science China University of Mining and TechnologyBeijing 100083China Beijing Radiation Center Beijing 100875China

Using the Dirac–Heisenberg–Wigner formalism,effects of the asymmetric pulse shape on the generation of electronpositron pairs in three typical polarized fields,i.e.,linear,middle elliptical and circular fields,are *** kinds of asymmetries for the falling pulse length,short and elongated,are *** find that the interference effect disappears with the shorter pulse length and that the peak value of the momentum spectrum is concentrated in the center of the momentum *** the case of the extending falling pulse length,a multiring structure without interference appears in the momentum *** results show that the momentum spectrum is very sensitive to the asymmetry of the pulse as well as to the polarization of the *** also find that the number density of electronpositron pairs under different polarizations is sensitive to the asymmetry of the electric *** the short falling pulse,the number density can be significantly enhanced by over two orders of *** results could be useful in planning high-power and/or high-intensity laser experiments.

关键词： asymmetric pulse electron-positron pair production polarized fields