Chirped dynamically assisted pair production in spatial inhomogeneous electric fields is studied by the Dirac-Heisenberg-Wigner formalism. The effects of the chirp parameter on the reduced momentum spectrum, the reduced total yield of the created pairs for either low or high frequency one-color field and two-color dynamically assisted combinational fields are investigated in detail. Also, the enhancement factor is obtained in the later two-color field case. It is found that for the low frequency field, no matter whether it is accompanied by the other high frequency field, its chirping has a little effect on the pair production. For the one-color high frequency field or/and two-color fields, the momentum spectrum exhibits incomplete interference and the interference effect becomes more and more remarkable as chirp increases. We also find that in the chirped dynamically assisted field, the reduced total yield is enhanced significantly when the chirps are acting on the two fields, compared with that the chirp is acting only for the low frequency strong field. Specifically, by the chirping, it is found the reduced pair number is increased by more than one order of magnitude in the field with a relative narrow spatial scale, while it is enhanced at least two times in other case of field with larger spatial scales or even in the quasi-homogeneous region. We also obtain some optimal chirp parameters and spatial scales for the total yield and enhancement factor in different scenarios of the studied external field. These results may provide a theoretical basis for possible experiments in the future.

The momentum spectrum and number density of created bosons for two types of arbitrarily polarized electric fields are calculated and compared with those of created fermions, employing the equal-time Feshbach-Villars-Heisenberg-Wigner formalism which is confirmed that for an uniform and time-varying electric field it is completely equivalent to the quantum Vlasov equation in scalar QED. For an elliptically polarized field, it is found that the number density of created bosons is a square root of the number density of spin-up electrons times that of spin-down ones for a circularly polarized multicycle field. Moreover, the degree of spin polarization roughly grows as the Keldysh adiabaticity parameter increases for arbitrarily polarized multicycle fields. For a field constituted of two circularly polarized fields with a time delay, it is shown that momentum vortices also exist in boson pair creation and are induced only by the orbital angular momentum of particles. However, the vortices can reproduce the quantum statistic effect due to the effect of spin of particles. These results further deepen the understanding of some significant signatures in pair production.

The axion-like particle (ALP) is a well motivated new particle candidate of beyond the Standard Model. In this work, we propose to probe the ALP through the photon fusion scattering at the upcoming Electron-Ion Collider (EIC) with electron and proton energy $E_e=20~{\rm GeV}$ and $E_p=250~{\rm GeV}$. It shows that we could constrain the effective coupling strength between ALP and photons to be $0.2~{\rm TeV}^{-1}$ at $2\sigma$ confidence level with the integrated luminosity of $300~{\rm fb}^{-1}$ for the mass range $m_a\in [5,40]~{\rm GeV}$. Such bound could be much improved if we consider the nucleus beam at the EIC. We also demonstrate that the limits from the EIC could be stronger than the off $Z$-pole measurement at the LEP and the Light-by-Light scattering with pp collision at the LHC.

We analyzed the security of the multiparty quantum secret sharing (MQSS) protocol recently proposed by Zhang, Li and Man [Phys. Rev. A \textbf{71}, 044301 (2005)] and found that this protocol is secure for any other eavesdropper except for the agent Bob who prepares the quantum signals as he can attack the quantum communication with a Trojan horse. That is, Bob replaces the single-photon signal with a multi-photon one and the other agent Charlie cannot find this cheating as she does not measure the photons before they runs back from the boss Alice, which reveals that this MQSS protocol is not secure for Bob. Finally, we present a possible improvement of the MQSS protocol security with two single-photon measurements and six unitary operations.

Multiple isotopes of samarium element are the isotopes produced by the s process, and 154Sm is produced by the r process. In addition, 144Sm is p nuclei in nuclear astrophysics. The measurement of these can help us to better understand the results of relevant photonuclear reaction experiments. On the other hand, 149Sm is a 235U fission product with a 1% yield, its cross sections are important to reactor neutronics. In this work, the neutron capture yield of the natural samarium target was measured at the back-streaming white neutron beamline (Back-n) of the China Spallation Neutron Source (CSNS), and the resonance parameters were analyzed by SAMMY code. The resonance peaks and the neutron separation energies contributed by the different isotopes are considered individually. The results of the capture yield found signs of the possibility of two resonance peaks at 8 eV, which awaits further experimental examination. Cross-section was calculated according to resonance parameters and was compared with other experimental results and evaluation databases of ENDF/B-VIII.0 and CENDL-3.2. A clear difference between ENDF/B VIII.0 and CENDL-3.2 database appears at 23.2 eV, the experimental result at this energy is smaller than data of ENDF/B VIII.0 database but CENDL-3.2 database. Most of the controversial experimental results invariably come from the samarium 149 isotope.

Electron-positron pair production in frequency modulated Sauter potential wells is investigated in the framework of the computational quantum field theory. In combined potential wells with a static Sauter potential well and a frequency modulated oscillating one, the modulated amplitude has a large effect on the number of created pairs. The optimal modulation amplitude of frequency at different center frequencies is obtained, which increases the number of electrons at about two times. However, for a single oscillating potential well with frequency modulation, chirp effect is sensitive to the center frequency, and the number of electrons can be enhanced even to four orders of magnitude at a regime of low center frequency. It implies that for a slowly oscillating Sauter potential well, the chirp effect through the frequency modulation is better than adding a static potential well to improve the pair production.

Simulations by transport codes are indispensable to extract valuable physics information from heavy ion collisions. In order to understand the origins of discrepancies between different widely used transport codes, we compare 15 such codes under controlled conditions of a system confined to a box with periodic boundary, initialized with Fermi-Dirac distributions at saturation density and temperatures of either 0 or 5 MeV. In such calculations, one is able to check separately the different ingredients of a transport code. In this second publication of the code evaluation project, we only consider the two-body collision term, i.e. we perform cascade calculations. When the Pauli blocking is artificially suppressed, the collision rates are found to be consistent for most codes (to within $1\%$ or better) with analytical results, or completely controlled results of a basic cascade code after eliminating the correlations within the same pair of colliding particles. In calculations with active Pauli blocking, the blocking probability was found to deviate from the expected reference values. The reason is found in substantial phase-space fluctuations and smearing tied to numerical algorithms and model assumptions in the representation of phase space. This results in the reduction of the blocking probability in most transport codes, so that the simulated system gradually evolves away from the Fermi-Dirac towards a Boltzmann distribution. As a result of this investigation, we are able to make judgements about the most effective strategies in transport simulations for determining the collision probabilities and the Pauli blocking. Investigation in a similar vein of other ingredients in transport calculations, like the mean field propagation or the production of nucleon resonances and mesons, will be discussed in the future publications.

Fine structure in the $\alpha$ decay of $^{223}$U was observed in the fusion-evaporation reaction $^{187}$Re($^{40}$Ar, p3n) by using fast digital pulse processing technique. Two $\alpha$-decay branches of $^{223}$U feeding the ground state and 244 keV excited state of $^{219}$Th were identified by establishing the decay chain $^{223}$U $\xrightarrow{\alpha_{1}}$ $^{219}$Th $\xrightarrow{\alpha_{2}}$ $^{215}$Ra $\xrightarrow{\alpha_{3}}$ $^{211}$Rn. The $\alpha$-particle energy for the ground-state to ground-state transition of $^{223}$U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62$^{+14}_{-10}$ $\mu$s. Evolution of nuclear structure for $N$ = 131 even-$Z$ isotones from Po to U was discussed in the frameworks of nuclear mass and reduced $\alpha$-decay width, a weakening octupole deformation in the ground state of $^{223}$U relative to its lighter isotones $^{219}$Ra and $^{221}$Th was suggested.

The fermion particle pair production in strong SU(2) gauged chromoelectric fields is studied by using Boltzmann-Vlasov equation in a classical way. The existence of pre-production process in a classical description is shown with the distribution evolution of non-Abelian particle production. It is interesting to find that the distribution center of particle number density is on two islands and has a split on color charge sphere as it evolutes and reaches a steady state at last, which is related to the amplitude and the varying of the field.

The effect of the frequency chirping on momentum spectrum and pair production rate 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 frequency chirp parameter at the moment $t=0$ leads 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 low frequency strong field or high frequency weak field but sensitive to the parameters of large frequency chirp added in high frequency weak field.

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 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.

Electron-positron pair production, in combined Sauter potential wells and an oscillating one is imposed on a static Sauter potential, is investigated by using the computational quantum field theory. We find that the gain number (the difference of pair number under combined potentials to the simple addition of pair number for each potential) of the created pairs depends strongly on the depth of static potential and the frequency of oscillating potential. In particular, it is more sensitive to the frequency compared with the depth. For the low-frequency multiphoton regime, the gaining is almost positive and exhibits interesting nonlinear characteristics on both depth and frequency. For the single-photon regime, however, the gaining is almost negative and decreases near linearly with depth while it exhibits an oscillation characteristic with frequency. Furthermore, the optimal frequency and depth of gain number are found and discussed.

Electron-positron pair production in an oscillating Sauter potential is investigated in the framework of the computational quantum field theory. It is found that for a Sauter potential well with oscillating width and depth simultaneously, the phase difference between them has a great impact on the number of created electron-positron pairs. Optimal values of the phase difference corresponding to different oscillation frequencies are obtained. The optimal phase difference has a strong nonlinear dependence on oscillating frequency. When the potential well changes slowly, our results can be explained by the instantaneous bound states. For the higher frequency case, however, multiphoton effect is enhanced and the Pauli blocking effect has a strong inhibitory effect on pair creations. These results can provide a theoretical reference for the experimental creation of the electron-positron pairs.

Pair production in inhomogeneous electric fields with symmetrical frequency chirp is studied numerically using the Dirac-Heisenberg-Wigner formalism. We investigate high- and low-frequency modes and consider two carrier envelope phases. Momentum spectrum is sensitive to chirp causing different interference effect for different spatial scales as well as the carrier phase of the external field. The reduced particle number is in general enhanced with increasing chirp. The effect of spatial scale of the field on the reduced particle number is also examined. It is found that it is enhanced at small spatial scale but is almost unchangeable at large spatial scales for the considered field parameters. On the other hand, at small spatial scale, the reduced particle number is enhanced by one or two orders when chirp is applied with the exception of cosine low-frequency field which is only a few times larger. Moreover it is found that the reduced particle number is further increased by symmetrical chirp at about two times by comparing to the usual asymmetrical chirp in high frequency field.

Electron-positron pair production from vacuum in external electric fields with space and time dependencies is studied numerically using real time Dirac-Heisenberg-Wigner formalism. The influence of spatial focusing scale of the electric field on momentum distribution and the total yield of the particles is examined by considering standing wave mode of the electric field with different temporal configurations. With the decrease of spatial extent of the external field, signatures of the temporal field are weaken in the momentum spectrum. Moreover, in the extremely small spatial extent, novel features emerge due to the combined effects of both temporal and spatial variations. We also find that for dynamically assisted particle production, while the total particle yield drops significantly in small spatial extents, the assistance mechanism tends to increase in these highly inhomogeneous regimes, where the slow and fast pulses are affected differently by the overall spatial inhomogeneity.

Electron-positron pair production in strong electric fields, i.e., the Sauter-Schwinger effect, is studied using the real-time Dirac-Heisenberg-Wigner formalism. Hereby, the electric field is modeled to be a homogeneous, single-pulse field with subcritical peak field strength. Momentum spectra are calculated for four different polarizations - linear, elliptic, near-circular elliptic or circular - as well as a number of linear frequency chirps. With details depending on the chosen polarization the frequency chirps lead to strong interference effects and thus quite substantial changes in the momentum spectra. The resulting produced pairs' number densities depend non-linearly on the parameter characterizing the polarization and are very sensitive to variations of the chirp parameter. For some of the investigated frequency chirps this can provide an enhancement of the number density by three to four orders of magnitude.

In this paper, we give formal results of Schwinger pair production correction in thermal systems with external background field by using the evolution operator method of thermo field dynamics, where especially tree level correction of thermal photons is considered with linear response approaches by an effective mass shift. We consider initial systems in two types of vacuums as zero temperature and thermal vacuum, respectively, with correction of thermal photons is or not included. As an example we give results of these corrections to pair production for a constant external background electric field.

The mechanism of multinucleon transfer (MNT) reactions for producing neutron-rich heavy nuclei around N = 126 is investigated within two different theoretical frameworks: dinuclear system (DNS) model and isospin-dependent quantum molecular dynamics (IQMD) model. The effects of mass asymmetry relaxation, N=Z equilibration, and shell closures on production cross sections of neutron-rich heavy nuclei are investigated. For the first time, the advantages for producing neutron-rich heavy nuclei around N = 126 is found in MNT reactions based on 238U target. We propose the reactions with 238U target for producing unknown neutron-rich heavy nuclei around N = 126 in the future.

An efficient quantum cryptography network protocol is proposed with d-dimension polarized photons, without resorting to entanglement and quantum memory. A server on the network, say Alice, provides the service for preparing and measuring single photons whose initial state are |0>. The users code the information on the single photons with some unitary operations. For preventing the untrustworthy server Alice from eavesdropping the quantum lines, a nonorthogonal-coding technique (decoy-photon technique) is used in the process that the quantum signal is transmitted between the users. This protocol does not require the servers and the users to store the quantum state and almost all of the single photons can be used for carrying the information, which makes it more convenient for application than others with present technology. We also discuss the case with a faint laser pulse.

Using the Dirac-Heisenberg-Wigner (DHW) formalism, e?ects of asymmetric pulse shape on the generation of electron-positron pairs in three typical polarized fields, i.e., the linear, middle elliptical and circular ones, are investigated. Two kinds of asymmetries for the falling pulse length, one is compressed and the other is elongated, are studied. It is found that the interference e?ect disappears with the compression of the pulse length, and finally the peak value of the momentum spectrum is concentrated in the center of the momentum space. For the opposite situation by extending the falling pulse length, a multi-ring structure without interference appears in the momentum spectrum. Research results exhibit that the momentum spectrum is very sensitive to the asymmetry of the pulse as well as to the polarization of the fields. It is also found that the number density of electron-positron pairs under di?erent polarizations is sensitive to the asymmetry of electric field. For the compressed falling pulse, the number density can be enhanced significantly over 2 orders of magnitude. These results could be useful in planning high power or/and high-intensity laser experiments.