B→K transition form factor up to $\mathcal{O}(1/m^2_b)$ within the kT factorization approach

We apply the k_T factorization approach to deal with the B→K transition form factor F^B→K _+,0(q²) in the large recoil regions. The B-meson wave functions Ψ_B and Ψ̄_B that include the 3-particle Fock states’ contributions are adopted to give a consistent PQCD analysis of the form factor up to . It has been found that the two wave functions Ψ_B and Ψ̄_B can give sizable contributions to the form factor and should be kept for a better understanding of the B-meson decays. Next the contributions from different twist structures of the kaon wave function are discussed, including SU_f(3)-breaking effects. A sizable contribution from the twist-3 wave function Ψ_p is found, whose model dependence is discussed by taking two groups of parameters that are determined by different distribution amplitude moments obtained in the literature. It is also shown that F^B→K _+,0(0)=0.30±0.04 and [F^B→K _+,0(0)/F^B→π _+,0(0)]=1.13±0.02, which are more reasonable and consistent with the light-cone sum rule results in the large recoil regions. PACS  12.38.Aw; 12.38.Bx; 13.20.He; 14.40.Aq     

Flavor non-universal gauge interactions and anomalies in B-meson decays

Motivated by flavor non-universaity and anomalies in semi-leptonic B-meson decays, we present a general and systematic discussion about how to construct anomaly-free U(1)' gauge theories based on an extended standard model with only three right-handed neutrinos. If all standard model fermions are vector-like under this new gauge symmetry, the most general family non-universal charge assignments,(a,b,c) for three-generation quarks and(d,e,f)for leptons, need satisfy just one condition to be anomaly-free, 3(a+b+c) =-(d+e+f). Any assignment can be linear combinations of five independent anomaly-free solutions. We also illustrate how such models can generally lead to flavor-changing interactions and easily resolve the anomalies in B-meson decays. Probes with B_s-B_s mixing, decay into τ~±, dilepton and dijet searches at colliders are also discussed.     

Phenomenological applications of<Emphasis Type="Italic">k</Emphasis><Subscript>T</Subscript>factorization

We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two-bodyB-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approach. PQCD results are compatible with present experimental data for charmless B-meson decays. We predict the possibility of large direct CP asymmetry in B⁰ → π⁺π⁻ (23 +7%) and B⁰ →K ⁺π⁻ (− 17 ± 5%). We also investigate the branching ratios, CP asymmetry and isospin symmetry breaking in radiativeB →(K*/ρ)γ decays.     

W-exchange dominance in neutral B-meson decay

Tests of W-exchange dominance in neutral B-meson decay are developed from the isospin and SU(3) properties of the final state. For B⁰ (d), it is shown that the decay rates into (D⁺ plus anything) and into (F⁺ plus anything) are always equal to one another and never more than $\text{3}\text{2}$ times the rate for (D⁰ plus anything). A similar analysis is applied to B⁰(s), and it is suggested that any of the four possibilities {;ψ, η_c}+(φ, η′) would make a good signal for this meson.     

Effects of charged Higgs bosons on the processes b→sγ, b→sg1 and b→sℓ+ℓ−

Effects of charged Higgs bosons (H⁺) on various loop-induced processes in the B-meson system are discussed, within the framework of two Higgs doublet models (2HDMs). The H⁺ contribution to the magnetic moment form factor turns out to be very significant and it can distinguish between the two types of 2HDMs. Even with constraints from B_d mixing, both strong enhancements or strong suppressions (in b→sγ) of decay rates are possible. Thus, information from these modes is competitive with, and may soon surpass, restrictions on 2HDMs from B_d mixing. Since (inclusive) b→sγ and b→sg¹ at current limits are not excluded, continued effort to detect them is encouraged.     

Evolution effects in Z0 fragmentation into Charmonium

In Z⁰ decay into prompt charmonium, i.e. charmonium not originating from B-meson decays, the most important contribution is expected to come from colour-octet mechanisms. However, previous fixed-order calculations of the colour-octet contribution contain large logarithms which, in a more complete treatment, should be resummed to all orders. We study this resummation by using a Monte Carlo QCD cascade model and find that the fixed-order colouroctet result is diminished by 15%. We compare the Monte Carlo calculations with results obtained by using analytical evolution equations.     

Decay constants of the B and D mesons from QCD-duality sum rules

We show that various (non-) relativistic versions of QCD duality sum rules lead to a unique prediction ƒ_b ⋍ (1.38 ± 0.14) ƒ_π for the decay constant of the pseudoscalar B-meson. We also obtain ƒ_D ⋍(1.31 ± 0.12) ƒ_π from relativistic Laplace (Borel) sum rules and show that the SU (3)_F-breaking effects tend to increase the decay corresponding of the corresponding mesons containing a strange quark. In view of our results, we re-examine some qualitative arguments predicting the mass behaviour of the decay constant of heavy-light quark bound states.     

Loop induced flavor changing neutral decays of the top quark in a general two-Higgs-doublet model

Decays of the top quark induced by flavor changing neutral currents (FCNC) are known to be extremely rare events within the Standard Model. This is so not only for the decay modes into gauge bosons, but most notably in the case of the Higgs channels, e.g., t→H_SM+c, with a branching fraction of 10⁻¹³ at most. Therefore, detection of FCNC top quark decays in a future high-energy, and high-luminosity, machine like the LHC or the LC would be an indisputable signal of new physics. In this paper we show that within the simplest extension of the SM, namely the general two-Higgs-doublet model, the FCNC top quark decays into Higgs bosons, t→(h⁰,H⁰,A⁰)+c, can be the most favored FCNC modes — comparable or even more efficient than the gluon channel t→g+c. In both cases the optimal results are obtained for Type II models. However, only the Higgs channels can have rates reaching the detectable level (10⁻⁵), with a maximum of order 10⁻⁴ which is compatible with the charged Higgs bounds from radiative B-meson decays. We compare with the previous results obtained in the Higgs sector of the MSSM.     

Feasibility of similarity coefficient map in improving morphological evaluation of T2* weighted MRI for renal cancer

The purpose of this paper is to investigate the feasibility of similarity coefficient map (SCM) in improving morphological evaluation of T₂^* weighted (T₂^*W) magnatic resonance imaging (MRI) for renal cancer. Simulation studies and in vivo 12-echo T₂^*W experiments for renal cancers were performed for this purpose. The results of the first simulation study suggest that SCM can reveal small structures which are hard to be distinguished from the background tissue in T₂^*W images and the corresponding T₂^* map. The capability of improving morphological evaluation is likely due to the improvement in signal to noise ratio (SNR) and carrier to noise ratio (CNR) by SCM technique. Compared with T₂^*W images, SCM can improve SNR by a factor ranging from 1.87 to 2.47. Compared with T₂^* maps, SCM can improve SNR by a factor ranging from 3.85 to 33.31. Compared with T₂^*W images, SCM can improve CNR by a factor raging from 2.09 to 2.43. Compared with T₂^* maps SCM can improve CNR by a factor raging from 1.94 to 8.14. For a given noise level, the improvements of SNR and CNR depend mainly on the original SNRs and CNRs in T₂^*W images, respectively. In vivo experiments confirmed the results of the first simulation study. The results of the second simulation study suggest that more echoes are used to generate SCM, and higher SNR and CNR can be achieved in SCM. In conclusion, SCM can provide improved morphological evaluation of T₂^*W MR images for renal cancer by unveiling fine structures which are ambiguous or invisible in the corresponding T₂^*W MR images and T₂^* maps. What is more, in practical application, for a fixed total sampling time, one should increase the number of echoes as much as possible to achieve SCMs with better SNR and CNR.     

标准模型中两类中性玻色子混合圈链图传播子的重整化及其e+e-→μ+μ-反应截面

采用电弱统一标准模型, 对光子γ和中间玻色子Z₀ 混合圈链图传播子的构架方式及其重整化问题作了详细分析与讨论, 并完成了有关解析计算, 获得了由参与电弱相互作用的各种混合圈构成的γ和Z₀的重整化链图传播子的解析计算结果. 此外, 我们还将此结果应用于高能物理中备受关注的一类轻子反应e⁺e^-→μ⁺μ^-中, 获得了在γ和Z₀所构架出的重整化混合圈链图传播中e⁺e^-→μ⁺μ^-反应截面的解析计算结果, 并将本文所获得的这一理论计算结果与实验观测值作了对比分析, 发现本文理论计算结果与实验观测值符合非常好, 并由此也获得了有关辐射修正的重要信息. 本文研究结果也可为探讨一般复杂传播子的理论研究与应用提供某些参考. 关键词： 标准模型 链图传播子 重整化 辐射修正     

Influence of caged noble-gas atom on the superatomic and valence states of C60−

Using high-level ab initio coupled cluster methods, we have conducted a detailed study of two endofullerene anions, He@C^?₆₀ and Ne@C^?₆₀. The main focus was on elucidating the effect of the noble-gas atom on the energy and electronic structure of the stable anion states of the parent C^?₆₀. Our study revealed that the noble-gas atom has no influence on the valence-like states of C^?₆₀, but strongly affects the superatomic-like ²A_g state. The latter was found to undergo pronounced destabilisation in both the He@C^?₆₀ and Ne@C^?₆₀ species, losing more than 70% of its original electron binding energy. The observed destabilisation is due to perturbation of the excess electron density of the ²A_g state inside the C₆₀ cage by the caged noble-gas atom. We show how the results of our analysis can be used to predict the behaviour of the ²A_g state in other closed-shell endohedral complexes. Some possible implications of the observed features of the ²A_g state are discussed.     

Assessment of body composition and total energy expenditure in humans using stable isotope techniques; IAEA Human Health Series No. 3

During the last decade compound-specific deuterium (²H) analysis of plant leaf wax-derived n-alkanes has become a promising and popular tool in paleoclimate research. This is based on the widely accepted assumption that n-alkanes in soils and sediments generally reflect δ²H of precipitation (δ²H_prec). Recently, several authors suggested that δ²H of n-alkanes (δ²H_n-alkanes) can also be used as a proxy in paleoaltimetry studies. Here, we present results from a δ²H transect study (～1500 to 4000 m above sea level [a.s.l.]) carried out on precipitation and soil samples taken from the humid southern slopes of Mt. Kilimanjaro. Contrary to earlier suggestions, a distinct altitude effect in δ²H_prec is present above ～2000 m a.s.l., that is, δ²H_prec values become more negative with increasing altitude. The compound-specific δ²H values of nC₂₇ and nC₂₉ do not confirm this altitudinal trend, but rather become more positive both in the O-layers (organic layers) and the A_h-horizons (mineral topsoils). Although our δ²H_n-alkane results are in agreement with previously published results from the southern slopes of Mt. Kilimanjaro [Peterse F, van der Meer M, Schouten S, Jia G, Ossebaar J, Blokker J, Sinninghe Damsté J. Assessment of soil n-alkane δD and branched tetraether membrane lipid distributions as tools for paleoelevation reconstruction. Biogeosciences. 2009;6:2799–2807], a re-interpretation is required given that the δ²H_n-alkane results do not reflect the δ²H_prec results. The theoretical framework for this re-interpretation is based on the evaporative isotopic enrichment of leaf water associated with the transpiration process. Modelling results show that relative humidity, decreasing considerably along the southern slopes of Mt. Kilimanjaro (from 78?% in ～2000 m a.s.l. to 51?% in 4000 m a.s.l.), strongly controls δ²H_{leaf water}. The modelled ²H leaf water enrichment along the altitudinal transect matches well the measured ²H leaf water enrichment as assessed by using the δ²H_prec and δ²H_n-alkane results and biosynthetic fractionation during n-alkane biosynthesis in leaves. Given that our results clearly demonstrate that n-alkanes in soils do not simply reflect δ²H_prec but rather δ²H_{leaf water}, we conclude that care has to be taken not to over-interpret δ²H_n-alkane records from soils and sediments when reconstructing δ²H of paleoprecipitation. Both in paleoaltimetry and in paleoclimate studies changes in relative humidity and consequently in δ²H_n-alkane values can completely mask altitudinally or climatically controlled changes in δ²H_prec.     

Measurements of some reaction rates of importance in KrF lasers

A flowing afterglow method has been used to study a number of reactions of importance in KrF lasers using NF₃ as the fluorine donor. Total rate constants are reported for Kr^*(³ P ₂)+NF₃ and Kr⁺+NF₃. The thermal energy attachment coefficient has been measured for NF₃ and the cross section for the electron excitation process Kr^*(³ P ₂) +e→Kr^*(³ P ₁)+e has been estimated. The relevance of these results to discharge pumped KrF lasers is discussed.     

Modelling the quark propagator

We are interested in developing covariant, confining, and asymptotically free models of hadrons. With this goal in mind we have carried out a study of dynamical chiral symmetry breaking without imposing the frequently used approximation α_s(−(p−k)²) α₅(−p_>²), where p_>² ≡ max(p², k²) for the running coupling constant in the quark Schwinger-Dyson equation. We present numerical results in Landau gauge and compare these with earlier results obtained when using this approximation. We see in this context that a gluon propagator which has the form 1/q⁴ in the infrared is too singular and must be regulated. We derive a suitably generalized expression for the pion decay constant f_π. With essentially one free parameter we are able to reproduce reasonable results for various physical quantities of interest including , and Λ_QCD.     

Influence of covalence and anion symmetry on the structure of small metal hydroxide clusters: Sodium versus silver hydroxide

An ab initio study of the Na_n(OH)_n, Na_n(OH)_n-1 ⁺, Ag_n(OH)_n, and Ag_n(OH)_n-1 ⁺ clusters with n up to four is presented. The results of this study show that, in accordance with experimental observations, the sodium hydroxide clusters are almost purely ionic, while the Ag-O bond exhibits a significant covalent character. The perturbation caused by the non-spherical OH^- group relatively to an atomic anion, as well as the influence on structures and energies of the covalent character of the metal-oxygen bond are determined. The appearance of metal-metal bonds in the silver hydroxide clusters is also discussed. Finally, the theoretical results obtained on the Na-OH clusters are compared to experimental results available on the dissociation of the Na_n(OH)_n-1 ⁺ clusters. Received 9 August 1999 and Received in final form 1st December 1999     

Present and future of neutrino oscillation experiments

Results of a new study of the discovery potential within mSUGRA parameter space of inclusive searches for SUSY at ATLAS are presented. These results indicate that superior performance is provided by the jets + E_T^miss channel in which no requirements are placed upon lepton multiplicity. The sensitivity of this and other channels is mapped in m₀ - m_1/2 parameter space for four different values of tan(β) with similar performance being obtained in all cases. Inclusive measurements of the effective mass scale M_susy^eff and total production cross-section σ_susy of supersymmetric particles are also discussed and results presented of a study of the likely measurement precisions.     

Determination of 226Ra, 232Th and 40K in teeth by use of gamma spectroscopy

This study entails the measurement of the specific activity of natural radionuclides (²²⁶Ra, ⁴⁰K and ²³²Th) in 18 tooth samples obtained from the clinic of the Universiti Sains Malaysia (USM), Penang, by using an HPGe detector. The specific activity of ²²⁶Ra, ⁴⁰K and ²³²Th was measured to estimate the hazard index of the radionuclides, radium equivalent activities (Ra_eq), external, internal hazard indices (H_ex, H_in), and absorbed dose (D_out, D_in). The maximum values of concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in the tooth samples were found to be 60.82, 60.29 and 594.22?Bq kg^?1, respectively. Maximum values of Ra_eq, H_ex, H_in, D_out and D_in were found to be 192.78?Bq kg^?1, 0.520, 0.685, 89.29 and 169.81?nGy h^–1, Iγ and Iα as 0.702 and 0.304, respectively. The results were lower than the average world value (UNSCEAR). In addition, a strong correlation was found between the concentrations of ²²⁶Ra and Ra_eq, between energy and net area, as well as between radionuclides (²²⁶Ra, ⁴⁰K and ²³²Th) in tooth samples and age of volunteers. This study showed that the concentrations and hazard indices of tooth samples are below the recommended safe levels; therefore, the study area is considered safe in terms of radiological health hazards.     

碱金属双原子分子部分电子态的完全振动能谱和离解能

对大多数双原子分子电子态的高阶振动能谱,现代实验方法和量子力学理论计算都难以得到较精确的振动能级.文中应用基于二阶微扰理论的代数方法(AM)以及计算双原子分子离解能的新表达式研究了碱金属双原子分子Li₂的3³Σ⁺_g,1³Δ_g和2³Π_g,Na₂的B¹Π_u以及K₂的4¹Σ⁺_g电子态的完全振动能谱{E_υ^AM}和离解能,理论计算结果不仅与已有的实验值相符,而且还给出了实验尚未得到的高阶振动能级.这些结果为碱金属双原子分子精确振动能谱和离解能的科学研究提供了重要数据. 关键词： 碱金属分子 高阶振动能级 离解能 代数方法     

发光二极管用红色荧光粉Sr0.8-xBaxEu0.2WO4的制备和性质研究

采用化学共沉淀法制备了不同Ba²⁺掺杂浓度、 不同煅烧温度的Sr_0.8-xBa_xEu_0.2WO₄红色荧光粉. 研究了样品的晶体取向和晶格 畸变对发光性质的影响, 实验结果表明: 合成的Sr_0.8-xBa_xEu_0.2WO₄红色荧光粉为四方相, 样品中Eu³⁺的⁵D₀–⁷F₂跃迁的红光能被近紫外光和蓝光有效激发. 适量的Ba²⁺离子取代部分的Sr²⁺提高了Sr_0.8Eu_0.2WO₄荧光粉的发光强度, Ba²⁺掺杂浓度的改变对基质的晶格参数、晶体对称性和发光性能影响较大, Ba²⁺的最佳掺杂量为30%.