[en] We study the weak decays of anti B_(_s_) and B_c into D-wave heavy-light mesons, including J"P = 2"- (D_(_s_)_2, D_(_s_)_2"', B_(_s_)_2, B_(_s_)_2"') and 3"- (D"*_(_s_)_3, B"*_(_s_)_3) states. The weak decay hadronic matrix elements are obtained based on the instantaneous Bethe-Salpeter method. The branching ratios for the anti B decays are B[ anti B → D_2e anti ν_e] = 1.1"-"0"."3_+_0_._3 x 10"-"3, B[ anti B → D_2"'e anti ν_e] = 4.1"-"0"."8_+_0_._9 x 10"-"4, and B[ anti B → D_3"*e anti ν_e] = 1.0"-"0"."2_+_0_._2 x 10"-"3, respectively. For the semi-electronic decays of anti B_s to D_s_2, D_s_2"', and D"*_s_3, the corresponding branching ratios are 1.7"-"0"."5_+_0_._5 x 10"-"3, 5.2"-"1"."5_+_1_._6 x 10"-"4, and 1.5"-"0"."4_+_0_._4 x 10"-"3, respectively. The branching ratios of the semi-electronic decays of B_c to D-wave D mesons are in the order of 10"-"5. We also obtained the forward-backward asymmetry, angular spectra, and lepton momentum spectra. In particular the distribution of decay widths for the 2"- states D_2 and D_2"' varying along with mixing angle are presented. (orig.)

[en] We study the semileptonic and nonleptonic decays of B_c meson to D-wave charmonia, namely, η_c_2(1"1D_2), ψ_2(1"3D_2), and ψ_3(1"3D_3). In our calculations, the instantaneous Bethe-Salpeter method is applied to obtain the hadronic matrix elements. This method includes relativistic corrections which are important especially for the higher orbital excited states. For the semileptonic decay channels with electron as the final lepton, we get the branching ratios B[B_c → η_c_2e anti ν_e] = 5.9_+_1_._0"-"0"."8 x 10"-"4, B[B_c → ψ_2e anti ν_e] = 1.5_+_0_._3"-"0"."2 x 10"-"4, and B[B_c → ψ_3e anti ν_e] = 3.5_+_0_._8"-"0"."6 x 10"-"4. The transition form factors, forward-backward asymmetries, and lepton spectra in these processes are also presented. For the nonleptonic decay channels, those with ρ as the lighter meson have the largest branching ratios, B[B_c → η_c_2ρ] = 8.1_+_1_._0"-"1"."0 x 10"-"4, B[B_c → ψ_2ρ] = 9.6_+_1_._0"-"1"."0 x 10"-"5, and B[B_c → ψ_3ρ] = 4.1_+_0_._8"-"0"."7 x 10"-"4. (orig.)

[en] We investigate the plasmonic-field-enhanced high-order harmonic generation (HHG) of H atom driven by few-cycle laser pulses, by solving the time-dependent Schrödinger equation (TDSE). Compared with the homogeneous field, HHG spectra generated by inhomogeneous field exhibit two-plateau structure. We analyze the origin of the two plateaus by using the semiclassical trajectory method. Our results from both classical and TDSE simulations show that the cutoffs of the two plateaus are dramatically affected by the carrier-envelope phase (CEP) of laser pulse in the inhomogeneous field, even for a little longer pulse. Thus, we can determine the CEP of driving laser based on the cutoff position of HHG generated in the inhomogeneous field. (paper)

[en] In this paper, the dilepton electromagnetic decays χ${}_{cJ}$(1P)→J/ψe${}^{+}$e${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$ and χ${}_{cJ}$(1P)→Jψμ${}^{+}$μ${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$, where χ${}_{cJ}$ denotes χ${}_{c0}$, χ${}_{c1}$ and χ${}_{c2}$, are calculated systematically in the improved Bethe–Salpeter method. The numerical results of decay widths and the invariant mass distributions of the final lepton pairs are given. The comparison is made with the recently measured experimental data of BESIII. It is shown that for the cases including e${}^{+}$e${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$, the gauge invariance is decisive and should be considered carefully. For the processes of χ${}_{cJ}$(1P)→J/ψe${}^{+}$e${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$, the branching fraction are: B[χ${}_{c0}$(1P)→J/ψe${}^{+}$e${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$]=1.06${}_{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}0.18}^{+0.16}$×10${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}4}$, B[χ${}_{c1}$(1P)→J/ψe${}^{+}$e${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$]=2.88${}_{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}0.53}^{+0.50}$×10${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}3}$, and B[χ${}_{c2}$(1P)→J/ψe${}^{+}$e${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$]=1.74${}_{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}0.21}^{+0.22}$×10${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}3}$. The calculated branching fractions of χ${}_{cJ}$(1P)→J/ψμ${}^{+}$μ${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$ channels are: B[χ${}_{c0}$(1P)→J/ψμ${}^{+}$μ${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$]=3.80${}_{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}0.64}^{+0.59}$×10${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}6}$, B[χ${}_{c1}$(1P)→J/ψμ${}^{+}$μ${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$]=2.04${}_{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}0.38}^{+0.36}$×10${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}4}$, and B[χ${}_{c2}$(1P)→J/ψμ${}^{+}$μ${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}$]=1.66${}_{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}0.19}^{+0.19}$×10${}^{\text{â<!-- ?? -->}\text{ˆ<!-- ?? -->}\text{’<!-- ??? -->}4}$.

[en] We investigate how the intensity and duration of an attosecond pulse generated from high-order harmonic generation are affected by the pressure and thickness of the gas jet by taking into account the macroscopic propagation of both fundamental and harmonic fields. Our simulations show that, limited by the propagation effects, especially the absorption of harmonics, the intensity of an attosecond pulse cannot be improved by just independently increasing the gas pressure or the medium length. On the other hand, due to good phase-matching conditions, the duration of a generated attosecond pulse can be improved by changing the gas pressure. (atomic and molecular physics)

[en] With the same constituents of quark and antiquark, the p-wave state has a higher mass than the corresponding s-wave state, but the relativistic corrections are much larger in the processes of which p-wave mesons are involved. Considering this, the relativistic Bethe—Salpeter method is applied to estimate the branching fractions of semileptonic decays B_(s) → D*_(sJ)lν (J = 0,2).

[en] In this paper, we use the instantaneous Bethe–Salpeter method to calculate the semi-leptonic and non-leptonic production of the orbitally excited scalar D${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}{\text{—<!-- ??? -->}}_0$ in B meson decays. When the final state is 1P state D${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}{\text{—<!-- ??? -->}}_0$(2400), our theoretical decay rate is consistent with experimental data. For D${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}{\text{—<!-- ??? -->}}_J$(3000) final state, which was observed by LHCb collaboration recently and here treated as the orbitally excited scalar D${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}{\text{—<!-- ??? -->}}_0$(2P), its rate is in the order of 10${}^{-<!--\; ???\; -->4}$∼10${}^{-<!--\; ???\; -->6}$. We find the special node structure of D${}^{\text{â<!-- ?? -->}}\text{ˆ<!-- ?? -->}{\text{—<!-- ??? -->}}_0$(2P) wave function possibly results in the suppression of its branching ratio and the abnormal uncertainty. The 3P states production rate is in the order of 10${}^{-<!--\; ???\; -->5}$.

[en] We calculate the electromagnetic (EM) decay widths of the B_c"±(2S) meson, which is observed recently by the ATLAS Collaboration. The main EM decay channels of this particle are 1"3S_1γ and 1Pγ, which, in literature, are estimated to have the branching ratio of about 1/10. In this work, we get the partial decay widths: Γ(2"1S_0→1"3S_1γ)=0.192 keV, Γ(2"1S_0→1P_1γ)=2.24 keV and Γ(2"1S_0→1P_1"′γ)=11.4 keV. In the calculation, the instantaneous approximated Bethe-Salpeter method is used. For the P-wave B_c mesons, the wave functions are given by mixing the "3P_1 and "1P_1 states. Within the Mandelstam formalism, the decay amplitude is given, which includes the relativistic corrections.

[en] We study the semi-leptonic and non-leptonic B weak decays that are governed by the B → D^(*) transitions. The branching ratios, CP asymmetries (CPAs) and polarization fractions of non-leptonic decays are investigated in the factorization approximation (FA). The B → D^(*) form factors are estimated in the Salpeter method. Our estimation on branching ratios is in general agreement with existing experimental data. For CPAs and polarizations, comparisons among the FA results, the perturbative QCD predictions and experimental data are presented. (the physics of elementary particles and fields)

[en] We propose a promising way to generate chirp-controllable circularly polarized terahertz waves from a magnetized Ar plasma driven by a linearly polarized laser. With an inhomogeneous static magnetic field, the local electrons are subjected to different strengths of the Lorentz force and emit terahertz waves with different cyclotron frequencies. In addition, the chirp rate and the temporal waveform of this chirped terahertz field can be adjusted by varying the gradient of the static magnetic field and the gas-density distribution. (paper)