Improved measurement of the form factors in the decay lambda+c-->lambda + nue

Using the CLEO detector at the Cornell Electron Storage Ring, we have studied the distribution of kinematic variables in the decay lambda(+)(c)lambda--> e(+)nu(e). By performing a four-dimensional maximum likelihood fit, we determine the form factor ratio, R= f(2)/f(1) = -0.31 +/- 0.05(stat) +/- 0.04(syst), the pole mass, M(pole) = [2.21 +/- 0.08(stat) +/- 0.14(syst)] GeV/c(2), and the decay asymmetry parameter of the lambda(+)(c), alpha (lambda(c)) = -0.86 +/-0.03(stat) +/- 0.02(syst), for q(2) = 0.67 (GeV/c(2))(2). We compare the angular distributions of the lambda(+)(c) and lambda(-)(c) and find no evidence for CP violation: A(lambda(c)) = (alpha(lambda(c)) + alpha (lambda(c)))/(alpha(lambda(c))-alpha(lambda(c))) = 0.00 +/- 0.03(stat) +/- 0.01(syst) +/- 0.02, where the third error is from the uncertainty in the world average of the CP-violating parameter, A(lambda), for ppi(-).     

Relaxation length of a polymer chain in a quenched disordered medium

Using Monte Carlo simulations, we study the relaxation and short-time diffusion of polymer chains in two-dimensional periodic arrays of obstacles with random point defects. The displacement of the center of mass follows the anomalous scaling law r(c.m.)(t)(2)=4D(*)t(beta), with beta<1, for times t相似文献   

Solving the bound-state Schrodinger equation by reproducing kernel interpolation

Based on reproducing kernel Hilbert space theory and radial basis approximation theory, a grid method is developed for numerically solving the N-dimensional bound-state Schrodinger equation. Central to the method is the construction of an appropriate bounded reproducing kernel (RK) Lambda(alpha)( ||r ||) from the linear operator -nabla(2)(r)+lambda(2) where nabla(2)(r) is the N-dimensional Laplacian, lambda>0 is a parameter related to the binding energy of the system under study, and the real number alpha>N. The proposed (Sobolev) RK Lambda(alpha)(r,r(')) is shown to be a positive-definite radial basis function, and it matches the asymptotic solutions of the bound-state Schrodinger equation. Numerical tests for the one-dimensional (1D) Morse potential and 2D Henon-Heiles potential reveal that the method can accurately and efficiently yield all the energy levels up to the dissociation limit. Comparisons are also made with the results based on the distributed Gaussian basis method in the 1D case as well as the distributed approximating functional method in both 1D and 2D cases.     

Maximal height scaling of kinetically growing surfaces

The scaling properties of the maximal height of a growing self-affine surface with a lateral extent L are considered. In the late-time regime its value measured relative to the evolving average height scales like the roughness: h*(L) approximately L alpha. For large values its distribution obeys logP(h*(L)) approximately (-)A(h*(L)/L(alpha))(a). In the early-time regime where the roughness grows as t(beta), we find h*(L) approximately t(beta)[lnL-(beta/alpha)lnt+C](1/b), where either b = a or b is the corresponding exponent of the velocity distribution. These properties are derived from scaling and extreme-value arguments. They are corroborated by numerical simulations and supported by exact results for surfaces in 1D with the asymptotic behavior of a Brownian path.     

Scaling of atmosphere and ocean temperature correlations in observations and climate models

Power-law scaling of near surface air temperature fluctuations and its geographical distribution is analyzed in 100-yr observations and in a 1000-yr simulation of the present-day climate with a complex atmosphere-ocean model. In observations and simulation detrended fluctuation analysis leads to the scaling exponent alpha approximately 1 over the oceans, alpha approximately 0.5 over the inner continents, and alpha approximately 0.65 in transition regions [spectrum S(f) approximately f(-beta),beta=2alpha-1]. Scaling up to decades is demonstrated in observations and coupled atmosphere-ocean models with complex and mixed-layer oceans. Only with the complex ocean model the simulated power laws extend up to centuries.     

Defect production in nonlinear quench across a quantum critical point

We show that the defect density n, for a slow nonlinear power-law quench with a rate tau(-1) and an exponent alpha>0, which takes the system through a critical point characterized by correlation length and dynamical critical exponents nu and z, scales as n approximately tau(-alphanud/(alphaznu+1)) [n approximately (alphag((alpha-1)/alpha)/tau)(nud/(znu+1))] if the quench takes the system across the critical point at time t=0 [t=t(0) not = 0], where g is a nonuniversal constant and d is the system dimension. These scaling laws constitute the first theoretical results for defect production in nonlinear quenches across quantum critical points and reproduce their well-known counterpart for a linear quench (alpha=1) as a special case. We supplement our results with numerical studies of well-known models and suggest experiments to test our theory.     

红外杂化单光束谱的性质

同一样品不同厚度(b₁和b₂)的两单光束谱ø_b1和ø_b2经线性组合得到杂化单光束谱ø_α=αø_b1+(1-α)ø_b2=αø₀e-Kb₁+(1-α)ø₀e-Kb₂,α为杂化系数。通过改变杂化系数α,就可获得任意强度的杂化谱ø_α。系统研究了杂化光谱ø_α的性质。研究表明,只要控制合适的条件,则厚度为(b₂-αb₂+αb₁)的真实样品的单光束谱ø_b(b=b₂-αb₂+αb₁)与杂化谱ø_α高度相似,ø_α的失真程度可忽略不计。也就是说,厚度在b₁～b₂间任一厚度b的真实样品的单光束谱都可用杂化谱ø_α来表达,ø_α≈ø_b。因此,不需制备厚度为b的样品,通过改变杂化系数α就可获得研究者所希望强度的单光束谱ø_b。杂化谱方法有望在扣除背景干扰等方面得到广泛应用。     

New scaling law for the decay exponent of bimolecular reactions in unbounded transitional flows

We propose a new scaling law for global kinetics of the stoichiometric reaction A+B-->P in unsteady, transitional flows. We find in the nonlinear flow regime the decay as approximately t(-alpha) where alpha is related to a space-time scaling parameter psi as alpha proportional, variant psi(m), for the considered parameter range m=0.067. In the linear flow regime, we find that the maximum is alpha approximately 2/3 for psi approximately 1. The proposed scaling law should be useful for linking dynamical subgrid processes with reaction kinetics in a variety of transitional flow systems.     

E expansion for a Fermi gas at infinite scattering length

We show that there exists a systematic expansion around four spatial dimensions for Fermi gas in the unitarity regime. We perform the calculations to leading and next-to-leading orders in the expansion over E = 4-d, where d is the dimensionality of space. We find the ratio of chemical potential and Fermi energy to be mu/epsilon(F) =1/2 (E 3/2) + 1/16 (E 5/2) lnE -0.0246E (5/2) + ... and the ratio of the gap in the fermion quasiparticle spectrum and the chemical potential to be Delta/mu =2E(-1) - 0.691 + ... . The minimum of the fermion dispersion curve is located at |p|=(2mepsilon(0))(1/2), where epsilon_(0)/mu=2+O(E). Extrapolation to d=3 gives results consistent with Monte Carlo simulations.     

Spectral properties of one dimensional quasi-crystals

In this paper we prove that the one dimensional Schrödinger operator onl ²(?) with potential given by: $$\upsilon (n) = \lambda \chi _{[1 - \alpha , 1[} (x + n\alpha )\alpha \notin \mathbb{Q}$$ has a Cantor spectrum of zero Lebesgue measure for any irrationalα and any λ>0. We can thus extend the Kotani result on the absence of absolutely continuous spectrum for this model, to all .     

Inertial mass of the Abrikosov vortex

We show that a large contribution to the inertial mass of the Abrikosov vortex comes from transversal displacements of the crystal lattice. The corresponding part of the mass per unit length of the vortex line is M(l)=(m(2)(e)c(2)/64 pi alpha(2)mu lambda(4)(L))ln((lambda(L)/xi), where m(e) is the bare electron mass, c is the speed of light, alpha=e(2)/Planck's over 2 pi c approximately 1/137 is the fine structure constant, mu is the shear modulus of the solid, lambda(L) is the London penetration length, and xi is the coherence length. In conventional superconductors, this mass can be comparable to or even greater than the vortex core mass computed by Suhl [Phys. Rev. Lett. 14, 226 (1965)]].     

Current relaxation in nonlinear random media

We study the current relaxation of a wave packet in a nonlinear random sample coupled to the continuum and show that the survival probability decays as P(t) approximately 1/t(alpha). For intermediate times tt(*) and chi>chi(cr) we find a universal decay with alpha=2/3 which is a signature of the nonlinearity-induced delocalization. Experimental evidence should be observable in coupled nonlinear optical waveguides.     

Light-induced giant softening of network glasses observed near the mean-field rigidity transition

The longitudinal acoustic (LA) mode of bulk GexSe1-x glasses is examined in Brillouin scattering (BS) over the 0.15相似文献   

The critical behavior of φ 1 4

The eigenvalues, eigenfunctions, and Schwinger functions of the ordinary differential operator $$H(\lambda ,m) = \tfrac{1}{2}\{ p^2 + \lambda q^4 + (m^2 - \lambda m^{ - 2} )q^2 \} $$ are studied as λ → ∞. It is shown that the scaling limit of the Schwinger functions equals the scaling limit of a one dimensional Ising model. Critical exponents ofH(λ,m) are shown to equal critical exponents of the Ising model, while critical exponents of the renormalized theory are shown to agree with those of a harmonic oscillator.     

In situ deuteron NMR investigations of sheared liquid crystalline polymers

The flow behavior of nematic liquid crystalline polysiloxanes of the side-chain type is studied by in situ 2H NMR spectroscopy on samples under shear in a cone-and-plate cell. The director orientation as a function of applied shear rate is determined from the quadrupole splitting of the spectra. The data analysis yields the two Leslie viscosity coefficients alpha2 and alpha3 and the flow-alignment parameter lambda = -(alpha3 + alpha2)/(alpha3 - alpha2). The values of lambda were determined for several homopolymers with only one type of side chain and random copolymers containing two different side chains. The results show that the flow behavior is related to the phase structure of the polymers, which varies with their composition. Only polymers with large amounts of smectic clusters in the nematic state show the tumbling instability (absolute value(lambda) < 1); other polymers are flow aligning (absolute value(lambda) > or = 1). For some polymers, a transition from tumbling at low temperature to flow aligning at high temperatures was observed.     

基于Raman激光雷达反演大气污染气体浓度几种方法

筊aman激光雷达是探测大气污染气体的一种重要方法,雷达回波反演是其中的重要步骤,反演的关键在于正确得到透过率指数因子。以消光系数为中心的三个方案,介绍了目前已普遍采用的方法、应用532 nm大气消光系数间接求取α(λ₁,z)和α(λ_２,z)。提出了两种新方法：(1) 采用拉曼波长与待测气体相近的参考气体,α(λ₁,z)＝α(λ_２,z);(2) 借助λ₁和λ₂的Mie-Rayleigh散射回波求取指数因子。     

Bound States in a Locally Deformed Waveguide: The Critical Case

We consider the Dirichlet Laplacian for astrip in with one straight boundary and a width , where $f$ is a smooth function of acompact support with a length 2b. We show that in the criticalcase, , the operator has nobound statesfor small .On the otherhand, a weakly bound state existsprovided . In thatcase, there are positive c ₁,c ₂ suchthat the corresponding eigenvalue satisfies for all sufficiently small.     

Random walks on a ( 2+1)-dimensional deformable medium

A model of random walks on a deformable medium is proposed in 2+1 dimensions. The behavior of the walk is characterized by the stability parameter beta and the stiffness exponent alpha. The average square end-to-end distance l approximately equals (2nu) and the average number of visited sites approximately equals (k) are calculated. As beta increases, for each alpha there exists a critical transition point beta(c) from purely random walks ( nu = 1/2 and k approximate to 1) to compact growth ( nu = 1/3 and k = 2/3). The relationship between beta(c) and alpha can be expressed as beta(c) = e(alpha). The landscape generated by a walk is also investigated by means of the visit-number distribution N(n)(beta). There exists a scaling relationship of the form N(n)(beta)approximately n(-2)f(n/beta(z)).     

First experimental measurements of the plasma potential throughout the presheath and sheath at a boundary in a weakly collisional plasma

Experimental data obtained with emissive probes and Langmuir probes show that the plasma potential profile in the presheath scales as -ephi /T(e)= sqrt[(x(0) -x)/lambda ], consistent with ion flux conservation, and that the sheath consists of a transition region and an electron-free collisionless sheath with thicknesses scaling as lambda( 1/5)lambda (4/5 )(D) and lambda(D )(ephi/ T(e))(3 /4), respectively, where lambda is the ion-neutral collision length. Results support Rieman's presheath and transitional region model [Phys. Plasmas 4, 4158 (1997)]]. The potential drop over the presheath and transition sheath region were the order of T(e) /e and 2T(e )/3e, respectively, increasing with increasing pressure.