The photino mass and γγ˜γ˜ production in e+e− annihilation

We present the exact calculation of the cross section for the process e⁺e^? → $\gamma \stackrel{?}{\gamma }\stackrel{?}{\gamma }$ with finite photino mass. The process is one of the best places to search for the stable photino at PETRA energy.     

Theoretical investigation of parity violation in p→α scattering

Calculations are presented of the parity-non-conserving (PNC) analyzing power A_z for longitudinally polarized incoming protons in elastic $\overrightarrow{p}\alpha$ scattering below ～50 MeV. The results are given in terms of the PNC as well as the regular, parity-conserving (PC) meson-nucleon coupling constants for single π-, ρ- and ω-exchange. The reliability and parameter dependence of the calculations are discussed in detail. The PC on-shell scattering parameters play an important role in particular for the angular dependence of A_z, which must be known for the actual analysis of measurements and are taken from experiments directly (phase analysis) rather than model calculations. The PNC scattering amplitudes are calculated in DWBA with optical-model wave functions properly antisymmetrized.Short-range correlations between nucleon pairs are taken into account by a Jastrow factor whose appropriate choice is discussed in detail. While absorption from the elastic channel is taken into account by the optical-model wave function, intermediate breakup channels are not included explicitly in the matrix elements.     

Relevance of inter-site Coulomb repulsion on high-Tc superconductivity within t−J−V model

The relevance of inter-site Coulomb repulsion (V) in the hole-doped cuprates is explored within $t?J?V$ model. An exact diagonalization (ED) technique is employed to investigate some ground state and thermodynamic properties of the model for various hole-doping. Results show that electron-electron ($e?e$) correlation is maximum between the next-nearest-neighbor (NNN) sites which decreases sharply at distances longer than √2 times the lattice spacing. Unlike hole-concentration, Coulomb repulsion reduces effective hopping amplitude. Our results suggest that in this hole-doped system, inter-site Coulomb repulsion favors d-wave pairing. Specific heat curves show characteristic single broad peaks where the peak-height decreases with doping concentration. From specific heat and entropy curves, one can expect a superconducting state at $<h>=0.25$.     

Search for new d0 half-metallic materials: theoretical investigation on KCaC1−xSix (x = 0; 0.25; 0.5; 0.75 and 1) compounds

In recent years, the investigations on d⁰ half-metallic materials have become the new trend in the search of novel materials for applications in spintronic devices. In this work, the structural, electronic and magnetic properties of KCaC${}_{1?x}$Si_x (x = 0; 0.25; 0.5; 0.75 and 1) compounds have been theoretically studied using the full-potential linearized augmented plane wave (FP-LAPW) method within framework of the density functional theory. The generalized gradient approximation scheme as proposed by Wu-Cohen (GGA-WC) and Tran-Blaha modified Becke-Johnson exchange potential with improved parameterization by Koller are adopted for the treatment of electron exchange-correlation. All considered materials show half-metallic characteristics with semiconducting majority spin channel and metallic minority one. The total spin magnetic moment is 1μ_B for ternary alloys and 4μ_B for quaternary compounds. Our obtained results suggest that these materials could be promising candidate for spintronic applications.     

The unified method for conformable time fractional Schro¨dinger equation with perturbation terms

The present study implements the unified method to the conformable time fractional non linear Schr$\ddot{\text{o}}$dinger equation with perturbation terms. Reduction of the governing equation to a simpler ODE by compatible complex transform is the first step of the procedure. The predicted solutions in finite series forms of various functions satisfying some particular ODEs are substituted into the reduced form of the governing equation. The algebra is resulted in forming the explicit exact solutions in optical solitary, periodic, elliptic and soliton wave forms represented in polynomial or rational functions.     

Baryon-charge transfer and production asymmetry of Λ0/ [`(L)] 0\bar \Lambda ^0 in hadron interactions

Predictions were made for asymmetry between production spectra of Λ⁰ and at the energy of LHC experiments. The value of A(s) should be situated in the corridor between two curves calculated in the quark-gluon string model with two possible values of intercept α _SJ(0) = 0.5 and 0.9. Both curves describe the asymmetries measured at lower energies up to RHIC experiments. The data of the H1 experiment can be fitted only with α _SJ(0) = 0.9. The text was submitted by the author in English.     

B0 ? ffB^0 \to \phi\phi decay in perturbative QCD approach

The rare decay can occur only via the penguin annihilation topology in the standard model. We calculate this channel in the perturbative QCD approach. The predicted branching ratio is very small: around 10^-8. We also give the polarization fractions, which show that the transverse polarization contribution is comparable to the longitudinal one, due to a big transverse contribution from factorizable diagrams. The small branching ratio in SM makes it sensitive to any new physics contributions.Received: 29 January 2005, Published online: 28 April 2005     

Logics from ?{￠}\sqrt{^{\prime}} Quasi-MV Algebras

The purpose of the present article is to extend the scope of some investigations about abstract logics arising quite naturally out of Quasi-MV algebras (for short, qMV algebras) also to ?{^￠}\sqrt{^{\prime}} qMV algebras. We will therefore introduce, mutually compare and (in some cases) axiomatise several logics arising out of the variety of ?{^￠}\sqrt{^{\prime}} qMV algebras and out of some important subclasses of such. Subsequently, we will investigate the same logics by resorting to the methods and techniques of abstract algebraic logic.     

Measurement of π0 and η mesons with PHENIX in ?[`(sNN )]\surd \overline {s_{NN} } 200 GeV Au+Au collisions at RHIC

The π ^o meson has been a crucial probe for observing jet quenching in ultrarelativistic heavy-ion collisions at RHIC. Measurements of the η meson in the same collisions have also shed light on a possible dependence of the observed suppression on the particle species. The preliminary π ⁰ nuclear modification factor R _AA from the 2004 RHIC run allowed a first systematic comparison between a precise measurement with high statistics and theoretical calculations, constraining model parameters such as the initial gluon density dN^g/dy, and the transport coefficient [^(q)]\hat q. The final π ⁰ spectra and R _AA are shown as well as the first η results obtained with both PHENIX electromagnetic calorimeters.     

Si中S0/Se0,S0/Te0和Se0/Te0对的电子结构

利用紧束缚近似下的格林函数方法,讨论了Si中硫属元素混对杂质(即S⁰/Se⁰,S⁰/Te⁰和Se⁰/Te⁰)基态的电子结构。混对杂质在Si禁带中引入两个A₁能级,其中成键性的A₁能级位置在反键性的A₁能级之上。数值计算得到的混对杂质能级与实验符合得相当好。理论分析表明,在Si中测到的那些未定的比最近邻混对杂质能级更浅的能级(S⁰/Se⁰(X₁),S⁰/Te⁰(X₁),Se⁰/Te⁰(X₁)…)不是由非最近邻位型的混对杂质引入的。本文还指出了一个极性分子放入Si晶体中,两个不同原子间s波函数的转移方向与通常极性分子相反,并讨论其物理原因。 关键词：     

GaN(100)表面结构的第一性原理计算

用全势缀加平面波加局域轨道(APW+lo)的方法计算了六方GaN及其非极性(1010)表面的原子及电子结构.计算出的六方GaN晶体结构参数晶格常数和体积弹性模量与实验值符合得很好.用平板超原胞模型来计算GaN(1010)表面的原子与电子结构,结果表明表面顶层原子发生键长收缩并扭转的弛豫特性.表面阳离子向体内移动,趋向于sp2平面构形;而表面阴离子向体外移动,趋向于锥形的p3构形.弛豫后,表面实现由半金属性向半导体性的转变.并且,表面电荷发生大的转移,参与表面键的重新杂化,使得表面原子的离子性减弱共价性增强,认为这就是表面原子键收缩并旋转的原因.