The ρ\rho Meson Light-Cone Distribution Amplitudes of Leading Twist Revisited

We give a complete re-analysis of the leading twist quark-antiquark light-cone distribution amplitudes of longitudinal and transverse $\rho$ mesons. We derive Wandzura-Wilczek type relations between different distributions and update the coefficients in their conformal expansion using QCD sum rules including next-to-leading order radiative corrections. We find that the distribution amplitudes of quarks inside longitudinally and transversely polarized $\rho$ mesons have a similar shape, which is in contradiction to previous analyses.Comment: 21 pages, latex2e, requires a4wide.sty and epsf.sty, 6 PS figures include

Photothermal effect in narrow band gap PbTe semiconductor

In this paper we report the observation of photothermal effect in PbTe p-n junction. The effect is expressed in photosignal generation due to illumination by 100 ns pulse CO(2) laser with photon energy less than PbTe forbidden gap

Re-examination of the Perturbative Pion Form Factor with Sudakov Suppression

The perturbative pion form factor with Sudakov suppression is re-examined. Taking into account the multi-gluon exchange in the law $Q^2$ regions, we suggest that the running coupling constant should be frozen at $\alpha_s(t=\sqrt{})$ and $\sqrt{}$ is the average transverse momentum which can be determined by the pionic wave function. In addition, we correct the previous calculations about the Sudakov suppression factor which plays an important role in the perturbative predictions for the pion form factor.Comment: 11 pages, LaTex file, 2 figures as uu-encoded postscript file

Hard diffractive electroproduction, transverse momentum distribution and QCD vacuum structure

We study the impact of the "intrinsic" hadron transverse momentum on the pre-asymptotic behavior of the diffractive electroproduction of longitudinally polarized $\rho$-meson. Surprisingly, we find the onset of the asymptotic regime in this problem to be rather low, Q^2 ~ 10 GeV^2 where power corrections due to the transverse momentum do not exceed 20 % in the amplitude. This drastically contrasts with exclusive amplitudes where the asymptotics starts at much higher Q^2 = 50 - 100 GeV^2. The sources of such unexpected behavior are traced back to some general (the quark-hadron duality) as well as more silent (properties of higher dimensional vacuum condensates) features of QCD.Comment: 27 pages (LaTex), 1 figure (epsfig

Nonfactorizable soft contributions in the B⟶ηcK,χc0KB\longrightarrow \eta_c K,\chi_{c0} K decays with the light-cone sum rules approach

In this article, we calculate the nonfactorizable soft contributions in the $B \to \eta_c K, \chi_{c0} K$ decays with the light cone QCD sum rules approach. Our results show that the nonfactorizable corrections from the soft gluon exchanges in the decay $B \to \eta_c K$ are of $(15-30)$ and should not be neglected. As for the decay $B \to \chi_{c0} K$, the factorizable contributions are zero and the nonfactorizable contributions from the soft hadronic matrix elements are too small to accommodate the experimental data.Comment: 16 pages; Revised versio

The Q2Q^2 dependence of the hard diffractive photoproduction of vector meson or photon and the range of pQCD validity

We consider two coupled problems. We study the dependence on photon virtuality $Q^2$ for the semihard quasi--elastic photoproduction of neutral vector mesons on a quark, gluon or real photon (at $s\gg p_{\bot}^2,\;Q^2; \; p_{\bot}^2\gg \mu^2 \approx (0.3$ GeV)$^2$). To this end we calculate the corresponding amplitudes (in an analytical form) in the lowest nontrivial approximation of perturbative QCD. It is shown that the amplitude for the production of light meson varies very rapidly with the photon virtuality near $Q^2=0$. We estimate the bound of the pQCD validity region for such processes. For the real incident photon the obtained bound for the $\rho$ meson production is very high. This bound decreases fast with the increase of $Q^2$, and we expect that the virtual photoproduction at HERA gives opportunity to test the pQCD results. The signature of this region is discussed. For the hard Compton effect the pQCD should work good at not too high $p_{\bot}$, and this effect seems measurable at HERA.Comment: ReVTeX, 36 pages, 5 Postscript figures, uses epsf.st

Comments on Exclusive Electroproduction of Transversely Polarized Vector Mesons

We discuss the electroproduction of light vector mesons from transversely polarized photons. Here QCD factorization cannot be applied as shown explicitly in a leading order calculation of corresponding Feynman diagrams. It is emphasized that present infrared singular contributions cannot be regularized through phenomenological meson distribution amplitudes with suppressed endpoint configurations. We point out that infrared divergencies arise also from integrals over skewed parton distributions of the nucleons. In a phenomenological analysis of transverse vector meson production model dependent regularizations have to be applied. If this procedure preserves the analytic structure suggested by a leading order calculation of Feynman diagrams, one obtains contributions from nucleon parton distributions and their derivatives. In particular polarized gluons enter only through their derivative

Impact of forward bias injection on minority carrier transport in p-type ZnO nanowires

Minority carrier diffusion length in p-type Sb-doped ZnO nanowires was measured as a function of temperature and forward bias injection duration. The minority carrier diffusion length displays a thermally activated length increase with the energy of 144 +/- 5 meV. The forward bias injection exhibits an increase in diffusion length with the activation energy of 217 +/- 20 meV, indicating the possible involvement of a Sb(Zn)-2V(Zn) acceptor complex

Belief Propagation and Loop Series on Planar Graphs

We discuss a generic model of Bayesian inference with binary variables defined on edges of a planar graph. The Loop Calculus approach of [1, 2] is used to evaluate the resulting series expansion for the partition function. We show that, for planar graphs, truncating the series at single-connected loops reduces, via a map reminiscent of the Fisher transformation [3], to evaluating the partition function of the dimer matching model on an auxiliary planar graph. Thus, the truncated series can be easily re-summed, using the Pfaffian formula of Kasteleyn [4]. This allows to identify a big class of computationally tractable planar models reducible to a dimer model via the Belief Propagation (gauge) transformation. The Pfaffian representation can also be extended to the full Loop Series, in which case the expansion becomes a sum of Pfaffian contributions, each associated with dimer matchings on an extension to a subgraph of the original graph. Algorithmic consequences of the Pfaffian representation, as well as relations to quantum and non-planar models, are discussed.Comment: Accepted for publication in Journal of Statistical Mechanics: theory and experimen

P-wave Quarkonium Decays to Meson Pairs

The processes of P-wave Quarkonium exclusive decays to two mesons are investigated, in which the final state vector mesons with various polarizations are considered separately. In the calculation, the initial heavy quarkonia are treated in the framework of non-relativistic quantum chromodynamics, whereas for light mesons, the light cone distribution amplitudes up to twist-3 are employed. It turns out that the higher twist contribution is significant and provides a possible explanation for the observation of the hadron helicity selection rule violated processes $\chi_{c1}\rightarrow \phi\phi,\omega\omega$ by the BESIII collaboration in recently. We also evaluate the $\chi_{b1}\to J/\psi J/\psi$ process and find that its branching ratio is big enough to be measured at the B-factories.Comment: more results and discussions adde