Comments on QCD Corrections to b + sγ Decay

We find some errors in the previous calculation of leading log QCD corrections to b + sγ decay, which include corrections from mto, to M_w in addition to corrections from M_w to m_b. The inclusive decay rate is found to be enhanced more than previous calculations. At m_t = 170 GeV, the running from m_top to M_w results in 13% enhancement, and for m_t = 250 GeV, 16% enhancement is found.     

镓原子的Stark能级结构

里德堡原子的Stark效应在偶极偶极相互作用、量子信息和量子调控等方面具有潜在的应用前景. 本文首先根据零场时镓原子的能级数据, 通过非线性拟合方法获得了镓原子各态的量子亏损, 仔细分析了量子亏损随主量子数的变化特征; 然后利用Numerov算法计算了镓原子的径向波函数; 最后采用矩阵对角化方法, 数值计算了镓原子高里德堡态在场强范围F=0-3000 V·cm^{- 1}时n=7和n=18附近的Stark能级结构. 结果显示在主量子数n=7多重态以上的能级结构中, (n+1)P态的能级接近并大于nD态的能级, 在n=7多重态以下的能级结构中, (n+1)P态的能级接近并小于nD态的能级. 这一现象不同于通常的碱金属原子的Stark结构, 论文对该现象及其他Stark能级结构特征进行了详细分析, 为相关研究工作提供了重要参考价值.     

构造纠缠目击的一般方法

量子纠缠作为量子通信和量子计算过程中不可缺少的资源,在量子信息领域中有着广泛的应用.如何判定一个给定的量子态是否为纠缠态仍然是一个重要的课题.纠缠目击是一种特殊的自伴算子,它可以用来判断一个量子态是否为纠缠态.本文首先从纠缠目击的定义入手,给出构造纠缠目击的一般方法,证明了当一个可测量A在可分纯态上的最大期望CA严格小于它的最大特征值λ_(max)(A)时,对任何满足条件C_A≤Cλ_(max)(A)的参数C,算子W_C=CI-A都是一个纠缠目击;然后,作为应用得到了利用图态的稳定子构造纠缠目击的一系列方法.     

The Signatures of the Neutral Top-Pion at the NLC and the Tevatron in Topcolor-Assisted MWTC Model

The neutral top-pion π_t⁰ can couple to the gluons and the photons through the top quark triangle-loop. we calculate the corrections of the neutral top-pion π_t⁰ to the tt production cross section in topcolor-assisted multiscale walking technicolor model. We find that, for a heavy neutral top-pion, the corrections are quite significant. For m_t = 175 GeV, 5 GeV ≤ m_t¹ ≤ 20 GeV and M_πt = 350 GeV, the relative correction Δσ/σ₀ is larger than 10% which might be observed at a high-luminosity Tevatron. We further estimate the production cross section of π_t⁰ at the NLC experiment. We find that the production rate is significantly large. The neutral top-pion π_t⁰ may be detected in future e⁺e^- linear collider experiments.     

Stark quantum beats under pulsed dye laser excitation

The method of quantum beat spectroscopy is extended to the study of pure electric field splittings. As an example Stark splittings of the 6s6p ¹P₁ term of Ba I are investigated by observing quantum beats after excitation by a short resonant dye-laser pulse. The derived value for the tensorial polarizability is in good agreement with previous work. Occurence and shapes of Stark quantum beat signals under different experimental conditions are discussed.     

On meson resonances and chiral symmetry

We study meson resonances with quantum numbers J^P=1⁺ in terms of the chiral SU(3) Lagrangian. At leading order a parameter-free prediction is obtained for the scattering of Goldstone bosons off vector mesons with J^P=1⁻ once we insist on approximate crossing symmetry of the unitarized scattering amplitude. A resonance spectrum arises that is remarkably close to the empirical pattern. In particular, we find that the strangeness-zero resonances h₁(1380), f₁(1285) and b₁(1235) are formed due to strong and channels. This leads to large coupling constants of those resonances to the latter states.     

THE POTENTIAL MODEL INVESTIGATION OF STARK EFFECT IN CAESIUM RYDBERG STATE ATOMS AND COMPARISON WITH EXPERIMENT

The potential model method for computation of Stark structure of Cs Rydberg states atoms and oscillator strength is described, for external electric fields varying from 0 to 600V/cm. Anticrossing, l-mixing and n-mixing phenomena are observed clearly from the map of Stark. Corresponding experiment is performed under the same condition, and the two results are in good agreement with each other within the experimental uncertainty.     

Supersymmetry for Fermion Masses

It is proposed that supersymmetry （SUSY） may be used to understand fermion mass hierarchies. A family symmetry ZSL is introduced, which is the cyclic symmetry among the three generation SU（2） doublets. SUSY breaks at a high energy scale - 10^11 GeV. The electroweak energy scale- 100 GeV is unnaturally small No additional global symmetry, like the R-parlty, is imposed. The Yukawa couplings and R-parity violating couplings all take their natural values, which are О（10^0 -10^-2）. Under the family symmetry, only the third generation charged ferrnions get their masses. This family symmetry is broken in the soft SUSY breaking terms, which result in a hierarchical pattern of the fermion masses. It turns out that for the charged leptons, the r mass is from the Higgs vacuum expectation value （VEV） and the sneutrino VEVs, the muon mass is due to the sneutrino VEVs, and the electron gains its mass due to both ZZL and SUSY hreaking. The large neutrino mixing are produced with neutralinos playing the partial role of right-handed neutrinos. │Ve3│, which is for Ve-Vr mixing, is expected to be about 0.1. For the quarks, the third generation masses are from the Higgs VEVs, the second generation masses are from quantum corrections, and the down quark mass due to the sneutrino VEVs. It explains me/ms, ms/me, md 〉 mu and so on. Other aspects of the model are discussed.     

由非绝热相关获得的形式量子数及其在高激发振动态的经典解释

我们利用非绝热相关方法 ,通过关闭所有的振动模式间的耦合项并追溯到零级本征态 ,以得到体系的形式量子数 ,将形式量子数对高激发振动态的能级谱图进行归属 ,并重构本征能级图谱 ,使本征能级以有序的方式排列。这有助于对高激发振动态的能级进行分类和归属。形式量子数是体现高激发振动态的重要特征 ,是高激发振动态的近似运动守恒量。我们将多维陪集相空间的经典方法应用于高激发态的研究 ,发现形式量子数对应的李雅普诺夫指数为零或最小 ,并且它对应于较大的相空间密度     

Detection of the 1pe series of doubly excited helium states below N=2 via the stark effect

The Stark effect on the doubly excited states of helium below the N=2 threshold has been studied by vacuum ultraviolet fluorescence yield spectroscopy. Two new series of states are observed at moderate fields (<10 kV/cm), and assigned to the previously unobserved even 1pe series, and a group of 1De series. The 1Se states are observed indirectly via their mixing with nearby 1 po states. The observations at moderate field contradict theoretical predictions that field strengths about an order of magnitude greater are necessary to observe the Stark effect on He doubly excited states at low quantum numbers.     

230—245nm范围内Cl原子共振增强多光子电离光谱

利用共振增强多光子电离－－时间飞行质谱技术获得了Ｃｌ原子在２３０－２４５ｎｍ范围内的代振增强多光子电离光谱,共观察到２６条谱线,其中５条是作者新观察到的,这些谱线对应从Ｃｌ原子基态到激发态的双光子跃迁。从中还观察到Ｃｌ原子在强电场中的Ｓｔａｒｋ效应,发现在强场条件下,Ｃｌｄ原子绵基太＾２Ｐ１／２＾０和＾２Ｐ３／２＾０两能级之间的能工位移１．３５ｃｍ＾＝１。而各电子激发态的Ｓｔａｒｋ位移则大致相等,     

Charge transfer of Rydberg H atoms at a metal surface

The charge transfer of Rydberg hydrogen atoms at a metal surface is investigated for the first time. The surface ionization of Stark states with various electron density distributions with respect to the surface is examined. Unlike the nonhydrogenic species studied previously, genuine control over the orientation of the electronic wave function in the surface-ionization process is demonstrated. A comparison of the results for a range of collisional velocities for the most redshifted Stark state with principal quantum numbers n=20-36 with the classical over-the-barrier approach shows a good agreement for the onset of the ion signal, but the shallow rise in signal is not accounted for. An excellent fit of the experimental results can be achieved using a simple semiempirical model.     

Geometry of skew information-based quantum coherence

We study the skew information-based coherence of quantum states and derive explicit formulas for Werner states and isotropic states in a set of autotensors of mutually unbiased bases (MUBs). We also give surfaces of skew information-based coherence for Bell-diagonal states and a special class of X states in both computational basis and in MUBs. Moreover, we depict the surfaces of the skew information-based coherence for Bell-diagonal states under various types of local nondissipative quantum channels. The results show similar as well as different features compared with relative entropy of coherence and l₁ norm of coherence.     

铯离子/原子与金属表面电荷交换的计算

用Ｎｅｗｎｓ－Ａｎｄｅｒｓｏｎ量子模型，计算了低能铯离子与涂有铯原子的钨表面（Ｃｓ／ｗ（１１０））碰撞时，由于电荷交换引起的末态电荷态的分布与Ｃｓ／Ｗ（１１０）表面功函数及表面温度的关系，计算结果与相应的实验符合得较好。同时，也给出了铯离子和原子与Ｃｓ／Ｗ（１１０）表面相互作用过程中粒子电荷态变化的全过程，并对两者作了比较． 关键词：     

用于铯原子内态操控的双光子拉曼激光的产生及应用

双光子拉曼过程是一种有效制备和控制原子内态的方法, 在原子内态操控和基于原子的量子信息处理中具有重要意义. 研制用于特定原子的拉曼激光是实现该过程的重要一步. 报道了利用光纤波导相位调制器及滤波器等实现用于铯原子内态操控的拉曼激光的方法, 并成功用于单个铯原子的内态精密操控. 通过4.6 GHz的微波信号源直接驱动波导相位调制器高效地获得光场的调制边带, 并利用自由光谱区为9.19 GHz的法布里-珀罗腔将载波及二阶边带滤掉, 获得了频率精确、相差9.19 GHz的拉曼激光. 经过基于光纤振幅调制器的功率稳定系统, 最终可以获得总功率为73 μupW、长时间内波动为2.2%的拉曼激光束, 并将此光束用于激发单个铯原子, 实现了|6S_1/2, F=4, mF=0和|6S_1/2, F=3, mF=0 之间的可控拉比操作.     

铯原子nP_(3/2)(n=70—94)里德伯态的紫外单光子激发及量子亏损测量

基于成熟的光纤激光器、光纤放大器及高效激光频率转换技术,我们在实验中研制了一套瓦级输出的窄线宽连续波单频可调谐318.6 nm紫外激光系统,并在室温铯原子气室中实现了6S_(1/2)—nP_(3/2)(n=70—94)单光子跃迁里德伯激发.借助由铯原子6S_(1/2)(F=4)基态、6P_(3/2)(F′=5)激发态和nP_(3/2)(n=70—94)里德伯态构成的V型三能级系统,通过频率锁定于铯原子6S_(1/2)(F=4)—6P_(3/2)(F′=5)超精细跃迁的852.3 nm探测光束的吸收减弱信号获得了里德伯态的信息,并利用高精度波长计测量了铯原子nP_(3/2)(n=70—94)里德伯态的量子亏损值.经过与理论计算值的变化趋势进行对比,我们认为由于原子气室的里德伯屏蔽效应并不能完全屏蔽外部直流电场,铯原子气室内存在残余的直流电场,影响了对里德伯态的量子亏损值的实验测量.利用残余直流电场的Stark效应理论模型及其与有效主量子数n*的依赖关系,对铯原子里德伯态的量子亏损实验测量值进行了修正.修正后的铯原子nP_(3/2)(n=70—94)态量子亏损测量值为3.5591±0.0007,与理论计算值相吻合.     

用B样条函数方法研究碱金属原子里德堡态在静电场中的性质

由原子的模型势出发,利用B样条函数方法研究了钾和铯原子的里德堡态在静电场中Stark态能级反交叉位置以及微波场中钾原子的多光子共振吸收谱.研究表明我们的结果与实验和其他理论结果符合得很好.     

Sufficient Conditions of the Same State Order Induced by Coherence

In this paper, we study coherence-induced state ordering with Tsallis relative entropy of coherence, relative entropy of coherence and l₁ norm of coherence, and give the sufficient conditions of the same state order induced by above coherence measures. First, we show that the above measures give the same ordering for single-qubit states in some special cases. Second, we consider some special states in a d-dimensional quantum system. We show that the above measures generate the same ordering for these special states. Finally, we discuss dynamics of coherence-induced state ordering under Markovian channels. We find amplitude damping channel changes the coherence-induced ordering even though for single-qubit states with fixed mixedness.     

Stark spectra of Rydberg states in atomic cesium in the vicinity of n=18

The Stark structures in a cesium atom around n=18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and those with a large |m| shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in ultracold atomic cesium. Atoms initially in 6P3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to the field, and Stark spectra with |m|=1/2,3/2,5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.     

Statistical and dynamic intensities of atomic spectral lines in plasma

Based on the quasi-classical approach, we solve the problem of a radiative cascade between Rydberg states in the space of parabolic quantum numbers that correspond to atom (or ion) quantization in a plasma microfield. We consider the level population source associated with the dielectronic recombination of electrons on ions with the cores in an external electric field. We determine the populations of states and the intensities of transitions between levels with a small change in principal quantum number. These “dynamic” intensities are compared with the “ statistical” intensities that correspond to an equidistribution in Stark sublevels. An appreciable discrepancy was found between the two types of intensities in plasma of low density that corresponds to the dominance of radiative transitions over collisional transitions.