Measurements of CP-violating asymmetries in the decay B0-->K+K-K0

We analyze the decay B0-->K+K-K0 using 383 x 10(6) BB events collected by the BABAR detector at SLAC to extract CP violation parameter values over the Dalitz plot. Combining all K+K-K0 events, we find ACP=-0.015+/-0.077+/-0.053 and beta eff = 0.352+/-0.076+/-0.026 rad, corresponding to a CP violation significance of 4.8 sigma. A second solution near pi/2-beta eff is disfavored with a significance of 4.5 sigma. We also report ACP and beta eff separately for decays to phi(1020)K0, f0(980)K0, and K+K-K0 with mK+K- > 1.1 GeV/c2.     

Electron impact ionization of sodium Rydberg atoms below 2 eV

We have observed electron impact ionization of highly excited sodium Rydberg atoms in ns and nd states, n=35-51, below E=2 eV electron kinetic energy with energy resolution 0.25 eV. Measured absolute cross sections near 0 eV range from sigma(35d) approximately 7 x 10(-10) to sigma(50d) approximately 4 x 10(-9) cm(2). The energy dependence is consistent with that of widely used binary encounter approximation cross sections, and sigma(n) follows a power law in n. The measured cross sections are 14 to 24 times larger than theoretically predicted values. This enhancement may signal the effect of large polarizabilities of high Rydberg states not yet accounted for in ionization theories.     

从热释光曲线同时确定电子复合与俘获之比及陷阱深度

复合发光的本质是两种载流子的复合,但其衰减规律则视具体情况可以从一个极限(指数)变到另一个极限(抛物线),即复合发光是一个连续变化的过程。这主要取决于导带电子的行为,导带电子的行为可以用电子与离化发光中心复合与被陷阱俘获之比来表示。加热发光是在变化温度下的发光弛豫,它既与复合与俘获之比有关,还是陷阱深度的函数,因此在利用加热发光曲线测定陷阱深度时,要同时确定这两个参数。利用热释光动力学模型及其原理,对其发光过程进行了分析,解释了热释光过程既不是一个单分子过程也不是一个双分子过程,这两个过程实际是两个极端情形,都是近似。文章同时利用一些工具软件具体计算了ZnS:Cu, Co的陷阱深度及电子复合与俘获概率之比,精确的计算了这些参数,得n₀ =2.6, ε=0.86eV。     

Persistence in systems with algebraic interaction

Persistence in coarsening one-dimensional spin systems with a power-law interaction r(-1-sigma) is considered. Numerical studies indicate that for sufficiently large values of the interaction exponent sigma (sigma > or =1/2 in our simulations), persistence decays as an algebraic function of the length scale L, P(L) approximately L(-theta). The persistence exponent theta is found to be independent on the force exponent sigma and close to its value for the extremal (sigma-->infinity) model, theta =0.175 075 88. For smaller values of the force exponent (sigma < 1/2), finite size effects prevent the system from reaching the asymptotic regime. Scaling arguments suggest that in order to avoid significant boundary effects for small sigma, the system size should grow as [O(1/sigma)](1/sigma).     

Scaling of the magnetoconductivity of silicon MOSFETs: evidence for a quantum phase transition in two dimensions

For a broad range of electron densities n and temperatures T, the in-plane magnetoconductivity of the two-dimensional system of electrons in silicon MOSFETs can be scaled onto a universal curve with a single parameter H(sigma)(n,T), where H(sigma) obeys the empirical relation H(sigma) = A(n) [Delta(n)(2)+T2](1/2). The characteristic energy k(B)Delta associated with the magnetic field dependence of the conductivity decreases with decreasing density, and extrapolates to 0 at a critical density n(0), signaling the approach to a zero-temperature quantum phase transition. We show that H(sigma) = AT for densities near n(0).     

Charmonium Decays of Y(4260), psi(4160), and psi(4040)

Using data collected with the CLEO detector operating at the CESR e+e- collider at sqrt[s]=3.97-4.26 GeV, we investigate 15 charmonium decay modes of the psi(4040), psi(4160), and Y(4260) resonances. We confirm, at 11 sigma significance, the BABAR Y(4260)-->pi+pi- J/psi discovery, make the first observation of Y(4260)--> pi(0)pi(0) J/psi (5.1 sigma), and find the first evidence for Y(4260)-->K+K- J/psi(3.7 sigma). We measure e+e- cross sections at sqrt[s]=4.26 GeV as sigma(pi+pi- J/psi)=58(+12)(-10)+/-4 pb, sigma(pi(0)pi(0) J/psi)=23(+12)(-8)+/-1 pb, and sigma(K+K- J/psi)=9(+9)(-5)+/-1 pb, in which the uncertainties are statistical and systematic, respectively. Upper limits are placed on other decay rates from all three resonances.     

NO分子A^2∑←X^2∏跃迁的激光双光子荧光激发谱

以Nd：YAD脉冲激光器泵浦的光学参量发生器／放大器(OPG／OPA)作激发光源,获得了420～472nm波长范围内NO分子的双光子激光荧光激发谱,并利用此技术对N0分子的能级结构进行了实验研究,将所得谱线峰归属为NO(A^2∑←X^2∏)的跃迁,荧光强度随激光强度的二次方变化关系表明此过程是一双光子激发过程。利用实验所得峰值波长计算了NO(A^2∑)态的基振动频率ωe和平衡位置的力常数k。通过对NO分子A^2∑←X^2∏跃迁的荧光时间分辨光谱进行实验研究,得到266Pa气压下A^2∑(v′=0)态的能级寿命r=53．76ns。测量荧光寿命随气压的变化,利用曲线拟合得到NOA。三(v′=0,1)两振动态的自发辐射寿命和无辐射跃迁驰豫速率常数。     

Phenomenological determination of the Kaon-neutron total cross-sections at high energy

Recent data on the scattering of neutralK mesons on various nuclei (regeneration amplitudes and totalK _L ⁰ cross-sections) are used to get a precise knowledge of inelastic rescattering of Kaons inside a nucleus, which allows a reliable phenomenological evaluation of the inelastic contributions to the cross-section defects in deuteron. New more accurate values for the Kaon-neutron total cross-section can then be deduced from Kaon-deuteron and Kaon-proton measurements. The total cross-sections \(\sigma _{K^ + p} ,\sigma _{K^ + n} ,\sigma _{K^ - p} ,\sigma _{K^ - n} \) are found to follow a classical Regge pattern, and the corresponding residues are determined.     

Direct calculation of the hard-sphere crystal /Melt interfacial free energy

We present a direct calculation by molecular-dynamics computer simulation of the crystal/melt interfacial free energy gamma for a system of hard spheres of diameter sigma. The calculation is performed by thermodynamic integration along a reversible path defined by cleaving, using specially constructed movable hard-sphere walls, separate bulk crystal, and fluid systems, which are then merged to form an interface. We find the interfacial free energy to be slightly anisotropic with gamma = 0.62+/-0.01, 0.64+/-0.01, and 0. 58+/-0.01k(B)T/sigma(2) for the (100), (110), and (111) fcc crystal/fluid interfaces, respectively. These values are consistent with earlier density functional calculations and recent experiments.     

Conductivity of a clean one-dimensional wire

We study the low-temperature low-frequency conductivity sigma of an interacting one-dimensional electron system in the presence of a periodic potential. The conductivity is strongly influenced by conservation laws, which, we argue, need to be violated by at least two noncommuting umklapp processes to render sigma finite. The resulting dynamics of the slow modes is studied within a memory matrix approach, and we find an exponential increase as the temperature is lowered, sigma approximately (Deltan)(2)e(T0/(NT)) close to commensurate filling M/N, Deltan = n-M/N<1, and sigma approximately e((T(')(0)/T)(2/3)) elsewhere.     

Magnitudes and orientations of the 15N chemical shift tensor of [1-15N]-2'-deoxyguanosine determined on a polycrystalline sample by two-dimensional solid-state NMR spectroscopy.

The magnitudes and orientations of the 15N chemical shift tensor of [1-15N]-2'-deoxyguanosine were determined from a polycrystalline sample using the two-dimensional PISEMA experiment. The magnitudes of the principal values of the 15N chemical shift tensor of the N1 nitrogen of [1-15N]-2'-deoxyguanosine were found to be sigma11 = 54 ppm, sigma22 = 148 ppm, and sigma33 = 201 ppm with respect to (15NH4)2SO4 in aqueous solution. Comparisons of experimental and simulated two-dimensional powder pattern spectra show that sigma33N is approximately collinear with the N-H bond. The tensor orientation of sigma33N for N1 of [1-15N]-2'-deoxyguanosine is similar to the values obtained for the side chain residues of 15Nepsilon1-tryptophan and 15Npi-histidine even though the magnitudes differ significantly.     

Heat transport in turbulent rayleigh-Benard convection

We present measurements of the Nusselt number N as a function of the Rayleigh number R in cylindrical cells with aspect ratios 0. 510(7) they are consistent with N = asigma-1/12R1/4+bsigma-1/7R3/7 as proposed by Grossmann and Lohse for sigma greater, similar2.     

Qualitative modification of the high energy atomic photoionization cross section

It is demonstrated that the nonrelativistic high energy omega-->infinity behavior of the photoionization cross section of an nl atomic subshell, sigma(nl)(omega), for l>0 is independent of l and is given by sigma(nl)(omega) approximately 1/omega(9/2), rather than the previously generally accepted sigma(nl)(omega) approximately 1/omega(l+7/2). Furthermore, for l = 1, although the exponent does not change, the coefficient is significantly altered. This modification of sigma(nl)(omega) is due to the interchannel interaction between ns photoionization channels and l not equal0 channels in the atom. As a result, for the photoionization of l not equal0 electrons, the single-particle approximation is never correct in the omega-->infinity limit. This has important consequences for sum rule calculations.     

利用发射光谱研究脉冲电晕放电中的自由基

利用发射光谱技术在大气压下测量了以氮气为载气的不饱和水蒸气体系针-板式正脉冲电晕放电产生的OH(A^2∑→X^2Ⅱ0—O)自由基和O(3p^5P→3s^5S^02777．4nm),Ha(3P→2S 656．3nm)活性原子的发射光谱,并由N2(C^3Ⅱu→B^3Ⅱg)的△v=-3和△v=-4振动带序发射光谱强度计算得出N2(C,v)的相对振动布居及其振动温度,进而采用高斯分布拟合准确地求出了N2(C^3Ⅱu→B^3Ⅱg)的△v= 1振动带序发射光谱强度,从而可以由N2(C^3Ⅱu→B^3Ⅱg)的△v= 1振动带序与OH(A^2∑→X^2Ⅱ0—0)的重叠发射光谱中准确求出OH(A^2∑→X^2Ⅱ0—0)自由基的发射光谱强度。由发射光谱强度得到了激发态OH(A^3∑)自由基和O(3p^5P),Ha(3P)活性原子的布居。还研究了激发态OH(A^2∑)自由基和O(3p^5P),Ha(3P)活性原子的布居随放电电压和放电频率的变化以及氧气对激发态OH(A^2∑)自由基和O(3p^5P),Ha(3P)活性原子布居的影响。     

Loudness growth observed under partially tripolar stimulation: model and data from cochlear implant listeners

Most cochlear implant strategies utilize monopolar stimulation, likely inducing relatively broad activation of the auditory neurons. The spread of activity may be narrowed with a tripolar stimulation scheme, wherein compensating current of opposite polarity is simultaneously delivered to two adjacent electrodes. In this study, a model and cochlear implant subjects were used to examine loudness growth for varying amounts of tripolar compensation, parameterized by a coefficient sigma, ranging from 0 (monopolar) to 1 (full tripolar). In both the model and the subjects, current required for threshold activation could be approximated by I(sigma)=Ithr(0)(1-sigmaK), with fitted constants Ithr(0) and K. Three of the subjects had a "positioner," intended to place their electrode arrays closer to their neural tissue. The values of K were smaller for the positioner users and for a "close" electrode-to-tissue distance in the model. Above threshold, equal-loudness contours for some subjects deviated significantly from a linear scale-up of the threshold approximations. The patterns of deviation were similar to those observed in the model for conditions in which most of the neurons near the center electrode were excited.     

Evidence for CP violation in B0-->D+D- decays

We report measurements of the branching fraction and CP violation parameters in B(0)-->D+ D- decays. The results are based on a data sample that contains 535 x 10(6) BB pairs collected at the Upsilon(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain [1.97+/-0.20(stat) +/- 0.20(syst)] x 10(-4) for the branching fraction of B0-->D+D-. The measured values of the CP violation parameters are S=-1.13+/-0.37+/-0.09, A=0.91+/-0.23+/-0.06, where the first error is statistical and the second is systematic. We find evidence of CP violation in B0-->D+D- at the 4.1sigma confidence level. While the value of S is consistent with expectations from other measurements, the value of the parameter A favors large direct CP violation at the 3.2sigma confidence level, in contradiction to standard model expectations.     

RbH(X1∑+,v=O～2)能级与H2碰撞振动能量转移

利用积分时间分辨荧光光谱方法,研究了RbH(X1∑+,v=0～2)与H2间的振动碰撞能量转移.在Rb-H2混合样品池中,泵浦激光双光子激发Rb原子至6D态,Rb(6D)与H2反应生成RbH(x1∑+)分子,探测激光延迟泵浦激光20 ns,通过激光感应荧光光谱(LIF)的测量,确定了X1∑+(v=0～2,J)原生态的转动...     

Dynamic correlation in wave propagation in random media

Field spectra are analyzed to yield the time-resolved statistics of pulsed transmission through quasi-one-dimensional dielectric media with static disorder. The normalized intensity correlation function with displacement and polarization rotation for an incident pulse of linewidth sigma at delay time t is a function only of the field correlation function, which is identical to that found for steady-state excitation, and of kappa(sigma)(t), the residual degree of intensity correlation at points at which the field correlation function vanishes. The dynamic probability distribution of normalized intensity depends only upon kappa(sigma)(t). Steady-state statistics are recovered in the limit sigma-->0, in which kappa(sigma=0) is the steady-state degree of correlation.     

Measurements of the cross section for e(+)e(-) --> hadrons at center-of-mass energies from 2 to 5 GeV

We report values of R = sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.     

Ascertaining the values of sigma x,sigma y,and sigma z of a polarization qubit

In the 1987 spin-retrodiction puzzle of Vaidman, Aharonov, and Albert one is challenged to ascertain the values of sigma(x), sigma(y), and sigma(z) of a spin-1/2 particle by utilizing entanglement. We report the experimental realization of a quantum-optical version in which the outcome of an intermediate polarization projection is inferred by exploiting single-photon two-qubit quantum gates. The experimental success probability is consistently above the 90.2% threshold of the optimal one-qubit strategy, with an average success probability of 95.6%.