共查询到20条相似文献,搜索用时 609 毫秒
1.
Zhi-Gang Luo Xiao-Lin Chen Xiang Liu Shi-Lin Zhu 《The European Physical Journal C - Particles and Fields》2009,60(3):403-411
Stimulated by recent observations of the excited bottom–strange mesons B
s1 and B
s2*, we calculate the semileptonic decays
, which is relevant for the exploration of the potential of searching these semileptonic decays in experiment. 相似文献
2.
3.
Study of electron drift velocity caused by Etimes B motion is done with the help of a Mach probe in a dc cylindrical magnetron sputtering system at different plasma discharge parameters like discharge voltage, gas pressure and applied magnetic field strength. The interplay of the electron drift with the different discharge parameters has been investigated. Strong radial variation of the electron drift velocity is observed and is found to be maximum near the cathode and it decreases slowly with the increase of radial distance from the cathode. The sheath electric field, E measured experimentally from potential profile curve using an emissive probe is contributed to the observed radial variation of the electron drift velocity. The measured values of the drift velocities are also compared with the values from the conventional theory using the experimental values of electric and magnetic fields. This study of the drift velocity variation is helpful in providing a useful insight for determining the discharge conditions and parameters for sputter deposition of thin film. 相似文献
4.
A.S.A. Alamir 《Optik》2009,120(18):984-986
Both radial and spiral distortion of magnetic lens with the field distribution in the form B(z)αzn are analyzed by means of Scherzer's formula. To estimate the performance of the image in electron microscope the dimensionless quality factors (F.Z. Marai, T. Mulvey, Sherzer's formula and the correction of spiral distortion in the electron microscope, Ultramicroscopy 2 (1977) 187–192.), for both radial and spiral distortion is calculated. The results have been compared with different projector lenses. 相似文献
5.
Reinvestigating B → PV decays by including contributions from ?B2 with the perturbative QCD approach
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Considering the B mesonic wave function \begin{document}$ {\phi}_{B2} $\end{document} ![]()
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, \begin{document}$ B {\to} PV $\end{document} ![]()
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decays are restudied in the leading order for three scenarios using the perturbative QCD approach within the standard model, where \begin{document}$ P = {\pi} $\end{document} ![]()
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and K, and V denotes the ground \begin{document}$S U(3)$\end{document} ![]()
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vector mesons. It is found that contributions from \begin{document}$ {\phi}_{B2} $\end{document} ![]()
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can enhance most branching ratios and are helpful for improving the overall consistency of branching ratios between the updated calculations and available data, although there are still several discrepancies between the experimental and theoretical results. 相似文献
6.
Junfeng Sun Dongsheng Du Yueling Yang 《The European Physical Journal C - Particles and Fields》2009,60(1):107-117
The B
c
→J/ψ
π, η
c
π decays are studied with the perturbative QCD approach. It is found that the form factors
and
for the B
c
→J/ψ, η
c
transitions and the branching ratios are sensitive to the parameters ω, v, f
J/ψ
and
, where ω and v are the parameters of the charmonium wave functions for a Coulomb potential and the harmonic-oscillator potential, respectively,
and f
J/ψ
and
are the decay constants of the J/ψ and η
c
mesons, respectively. The large branching ratios and the clear signals of the final states make the B
c
→J/ψ
π, η
c
π decays the prospective channels for measurements at the hadron colliders. 相似文献
7.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2008,58(2):245-250
We study the final-state rescattering effects in the decay B
0→η
c
K
*. The numerical results indicate that the corrections are comparable with the contribution from the naive factorizable amplitude,
and the total amplitudes can accommodate the experimental data. 相似文献
8.
Within the framework of perturbative QCD factorization, we investigate the nonfactorizable contributions to the factorization-forbidden quasi-two-body decays \begin{document}$ B_{(s)}\rightarrow h\chi_{c0}\rightarrow h\pi^+\pi^-(K^+K^-) $\end{document} ![]()
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with \begin{document}$ h=\pi, K $\end{document} ![]()
![]()
. We compare our predicted branching ratios for the \begin{document}$ B_{(s)}\rightarrow K\chi_{c0}\rightarrow K\pi^+\pi^-(K^+K^-) $\end{document} ![]()
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decay with available experiment data as well as predictions by other theoretical studies. The branching ratios of these decays are consistent with data and other theoretical predictions. However, in the Cabibbo-suppressed decays \begin{document}$ B_{(s)}\rightarrow h\chi_{c0}\rightarrow h\pi^+\pi^-(K^+K^-) $\end{document} ![]()
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with \begin{document}$ h=\bar{K}^0,\pi $\end{document} ![]()
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, the values of the branching ratios are of the order of \begin{document}$ 10^{-7} $\end{document} ![]()
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and \begin{document}$ 10^{-8} $\end{document} ![]()
![]()
. The ratio \begin{document}$ R_{\chi_{c0}} $\end{document} ![]()
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between the decays \begin{document}$B^+\rightarrow $\end{document} ![]()
![]()
\begin{document}$ \pi^+\chi_{c0}\rightarrow \pi^+\pi^+\pi^-$\end{document} ![]()
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and \begin{document}$ B^+\rightarrow K^+\chi_{c0}\rightarrow K^+\pi^+\pi^- $\end{document} ![]()
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and the distribution of branching ratios for different decay modes in invariant mass are considered in this study. 相似文献
9.
Fang Su Yue-Liang Wu Yi-Bo Yang Ci Zhuang 《The European Physical Journal C - Particles and Fields》2012,72(3):1914
We provide a systematic study of charmless B
s
→PP, PV, VV decays (P and V denote pseudoscalar and vector mesons, respectively) based on an approximate six-quark operator effective Hamiltonian from
QCD. The calculation of the relevant hard-scattering kernels is carried out, the resulting transition form factors are consistent
with the results of QCD sum-rule calculations. By taking into account important classes of power corrections involving “chirally
enhanced” terms and the vertex corrections as well as weak annihilation contributions with non-trivial strong phase, we present
predictions for the branching ratios and CP asymmetries of B
s
decays into PP, PV and VV final states, and also for the corresponding polarization observables in VV final states. It is
found that the weak annihilation contributions with non-trivial strong phase have remarkable effects on the observables in
the color-suppressed and penguin-dominated decay modes. In addition, we discuss the SU(3) flavor symmetry and show that the
symmetry relations are generally respected. 相似文献
10.
V. A. Kovalchuk 《Physics of Atomic Nuclei》2007,70(4):722-731
A method for determining the angle γ and the ratio of the amplitudes A
λ(B
− →
K
*−) and A
λ)B
− → D
*0
K
*−), r
Bλ, for all three vector-meson polarization states by using the decays B
∓ → D
*
K
*∓ is proposed. This method relies on the interference between the decays B
− → D
*0
K
*− and B
− →
K
*−, which arises if D
*0 and
decay to D
0/
π
0 and D
0/
γ, whereupon D
0 and
mesons decay to common final hadron states. The doubly Cabibbo-suppressed modes of D
0-meson decay are chosen here to specify such final states.
Original Russian Text ? V.A. Kovalchuk, 2007, published in Yadernaya Fizika, 2007, Vol. 70, No. 4, pp. 754–763. 相似文献
11.
12.
An X-ray method has been considered for determining the volume fraction of the B19′ martensite in semi-product NiTi alloys, which is based on comparing the total integrated intensity of its strongest reflections
with the total integrated intensity of reflections from the matrix B2 phase. It has been shown that the method enables one to determine the volume fraction of martensite with an error of about
1% both in textured and textureless samples. 相似文献
13.
基于代数方法(algebraic method)可以获得双原子分子的包含最高振动能级在内的所有高阶振动能级的精确数值这一事实,又提出了一种新的代数方法(algebraic method 2)来精确研究双原子分子电子态的振转能谱和转动常数. 以HF分子的B1Σ电子态为例,应用algebraic method 2方法研究了该电子态的振动量子数从ν=0到ν=10的所有振转能谱,获得了与实验值符合得非常好的理论结果.
关键词:
代数方法
双原子分子
振转能级 相似文献
14.
The lattice vibration spectrum, rf permittivity, and dynamic Born charges have been calculated for ordered Pb2
B′B″O3 (B′=Ga, In, Lu; B″=Nb, Ta) solid solutions in terms of the generalized Gordon—Kim model. It has been shown that all compounds exhibit a ferroelectric
instability and that the frequencies of “soft” ferroelectric modes are close in magnitude. The ferroelectric phase-transition
temperatures and the spontaneous polarization in the ferroelectric phase of the solid solutions under consideration have been
calculated by the Monte Carlo method using the model Hamiltonian in the local mode approximation. The transition temperature
is found to increase with increasing atomic number of the B′ ion. 相似文献
15.
S. Rai Choudhury A. S. Cornell Naveen Gaur 《The European Physical Journal C - Particles and Fields》2008,58(2):251-259
Flavor changing neutral current (FCNC) decays of the B-meson are a very useful tool for studying possible physics scenarios beyond the standard model (SM), where of the many FCNC
modes radiative, purely leptonic and semi-leptonic decays of the B-meson are relatively clean tests. Within this context, the BELLE collaboration has measured the process B→K
*
γ and also searched for the B→K
1(1270)γ process. Theoretical analyses of these processes are yielding similar values of the relevant form factors. In this work we
have used this upper bound in studying the angular correlations for the related semi-leptonic decay mode B
−→K
1−(1270)(→ρ
0
K
−)ℓ
+
ℓ
−, where we have used the form factors that have already been estimated for the B→K
1(1270)γ mode. Note that the additional form factors that are required were calculated using large energy effective theory (LEET). 相似文献
16.
Ying Li Juan Hua Kwei-Chou Yang 《The European Physical Journal C - Particles and Fields》2011,71(10):1775
The implications of the family non-universal Z′ model in the B→K
1(1270,1400)ℓ
+
ℓ
−(ℓ=e ,μ ,τ) decays are explored, where the mass eigenstates K
1(1270, 1400) are the mixtures of 1
P
1 and 3
P
1 states with the mixing angle θ. In this work, considering the Z′ boson and setting the mixing angle θ=(−34±13)○, we analyze the branching ratio, the dilepton invariant mass spectrum, the normalized forward–backward asymmetry and lepton
polarization asymmetries of each decay mode. We find that all observables of B→K
1(1270)μ
+
μ
− are sensitive to the Z′ contribution. Moreover, the observables of B→K
1(1400)μ
+
μ
− have a relatively strong θ-dependence; thus, the Z′ contribution will be buried by the uncertainty of the mixing angle θ. Furthermore, the zero crossing position in the FBA spectrum of B→K
1(1270)μ
+
μ
− at low dilepton mass will move to the positive direction with Z′ contribution. For the tau modes, the effects of Z′ are not remarkable due to the small phase space. These results could be tested in the running LHC-b experiment and Super-B
factory. 相似文献
17.
采用了传统的固相烧结工艺,制备了不同Zr和Hf掺杂量的SrBi4Ti4-xZrxO15(x=000,003, 006,010,020)和SrBi4Ti4-xHfxO15(x=000,0005, 0015,0030,0060)的陶瓷
关键词:
4Ti4-xZrxO15')" href="#">SrBi4Ti4-xZrxO15
4Ti4-xHfxO15')" href="#">SrBi4Ti4-xHfxO15
铁电性能
介电性能 相似文献
18.
采用基于第一性原理的赝势平面波方法系统地计算了LiBX2 (B= Ga, In; X= S,Se,Te) 晶体的光学性质与力学性质. 由禁带宽度推断出晶体抗激光损伤阈值的大小顺序为LiGaS2 > LiInS2 > LiGaSe2 > LiInSe2 > LiGaTe2 > LiInTe2. 六种晶体在常压下均满足机械力学稳定性要求, 且铟化合物可塑性及延展性强于镓化合物. 这些晶体的静态电介电常数 ε1(0)、静态折射率n(0)和双折射率Δn 理论计算值与实验值相符. LiGaS2, LiInS2, LiGaSe2, LiInSe2和LiGaTe2五种化合物双折射率较高, 并且它们的吸收谱与反射谱在中远红外区是透过的, 因此可推断出这五种化合物可以成为优异的中远红外非线性光学材料. 相似文献
19.
Yu-Ming Wang M. Jamil Aslam Cai-Dian Lü 《The European Physical Journal C - Particles and Fields》2009,59(4):847-860
The exclusive weak decay of Λ
b
→Λ
γ and Λ
b
→Λ
l
+
l
− are investigated in the Appelquist–Cheng–Dobrescu model, which is an extension of the standard model in the presence of universal
extra dimensions. Employing the transition form factors obtained in the light-cone sum rules, we analyze how the invariant-mass
distribution, the forward–backward asymmetry and the polarization asymmetry of the Λ baryon of these decay modes can be used to constrain the only additional free parameter with respect to the standard model,
namely, the radius, R, of the extra dimension. Our results indicate that the Kaluza–Klein modes can lead to approximately 25% suppression of the
branching ratio of Λ
b
→Λ
γ; however, their contributions can bring about 10% enhancement to the decay rate of Λ
b
→Λ
l
+
l
−. It is shown that in the present scenario the zero position of the forward–backward asymmetry of Λ
b
→Λ
μ
+
μ
− is sensitive to the compactification parameter R, while the measurement of polarizations of Λ baryon in the Λ
b
decays are not a useful tool to provide any valuable information for the universal extra-dimension model. 相似文献
20.
The polarization of a bremsstrahlung photon during the processes ee
± → (eγ)e
± and ep → (eγ)p is calculated for peripheral kinematics in the high-energy limit, where the cross section does not decrease with the incident
energy. When the initial electron is unpolarized (longitudinally polarized), the final photon can be linearly (circularly)
polarized. The Stokes parameters of the photon polarization are calculated as a function of the kinematical variables of the
process: the energy of the recoil particle, the energy fraction of the scattered electron, and the polar and azimuthal angles
of the photon. The numerical results are given in the form of tables for typical values of the relevant kinematic variables.
The text was submitted by the authors in English. 相似文献