Final-State Phases in Doubly-Cabibbo-Suppressed Charmed Meson Nonleptonic Decays

Cabibbo-favored nonleptonic charmed particle decays exhibit large final-state phase differences in $\bar K \pi$ and $\bar K^* \pi$ but not $\bar K \rho$ channels. It is of interest to know the corresponding pattern of final-state phases in doubly-Cabibbo-suppressed decays, governed by the $c \to d u \bar s$ subprocess. An experimental program is outlined for determining such phases via measurements of rates for $D \to K^* \pi$ and $K (\rho, \omega,\phi)$ channels, and determination of interference between bands in Dalitz plots. Such a program is feasible at planned high-intensity sources of charmed particles.Comment: 12 pages, LaTeX, 2 figures, to be submitted to Phys. Rev. D. Revised versio

Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells

Inhibition of cyclooxygenase (COX)-2 elicits therapeutic effects in solid tumors that are coupled with the inhibition of cell proliferation and induction of apoptosis in tumor cells. Aim: This study was designed to investigate the role of COX-2 inhibitor nimesulide in cell growth and apoptosis of the cultured human hepatocellular carcinoma HepG2 cells. Methods: We performed the MTT assay, flow cytometric analysis and cell morphology study to evaluate growth inhibition and cell apoptosis upon the action of nimesulide alone or along with doxorubicin, a common agent for the treatment of human hepatocellular carcinoma. Results: Our results showed that the treatment of HepG2 cells with more than 50 µM of nimesulide suppressed COX-2 enzyme activity because of reduced PGE2 production, and then induced growth inhibition and cell apoptosis despite no alterations of COX-2 protein expression. Importantly, the combination of 50 µM or 100 µM of nimesulide and low concentrations (5 µM to 20 µM) of doxorubicin resulted in enhanced cell growth inhibition, apoptosis induction and reduced VEGF production. Conclusion: These data suggest synergistic and/or additive effects of COX-2 inhibitors and chemotherapeutic agents, and may provide the rational for clinical studies of COX-2 inhibitors on the treatment or chemoprevention of human hepatocellular carcinoma.Угнетение циклооксигеназы-2 (ЦОГ-2) оказывает терапевтический эффект при лечении больных с солидными опухолями и сопровождается снижением пролиферации опухолевых клеток и индукцией апоптоза. Цель: изучение роли ингибитора ЦОГ-2 — нимесулида в процессах роста и апоптоза культивированных клеток гепатокарциномы человека HepG2. Методы: для оценки апоптоза и угнетения роста клеток при применении нимесулида самостоятельно и в сочетании с доксорубицином применяли MTT-анализ, проточную цитометрию и стандартные морфологические методы. Результаты: установлено, что обработка клеток HepG2 cells нимесулидом в концентрации > 50 μM приводила к угнетению активности ЦОГ-2 за счет снижения продукции PGE2 , после чего отмечали подавление роста и апоптоз клеток при неизмененном уровне экспрессии ЦОГ-2. Комбинированное применение 50 μM или 100 μM нимесулида и доксорубицина в концентрации 5–20 μM обусловило усиленное угнетение роста клеток, индукции апоптоза и снижение продукции VEGF. Выводы: полученные данные свидетельствуют о синергическом и/или аддитивном эффекте при применении ингибиторов ЦОГ-2 и химиотерапевтических препаратов

Threshold resummation for exclusive B meson decays

We argue that double logarithmic corrections $\alpha_s\ln^2 x$ need to be resumed in perturbative QCD factorization theorem for exclusive $B$ meson decays, when the end-point region with a momentum fraction $x\to 0$ is important. These double logarithms, being of the collinear origin, are absorbed into a quark jet function, which is defined by a matrix element of a quark field attached by a Wilson line. The factorization of the jet function from the decay $B\to\gamma l\bar\nu$ is proved to all orders. Threshold resummation for the jet function leads to a universal, {\it i.e.}, process-independent, Sudakov factor, whose qualitative behavior is analyzed and found to smear the end-point singularities in heavy-to-light transition form factors.Comment: 10 pages, more details are include

kTk_T factorization of exclusive processes

We prove $k_T$ factorization theorem in perturbative QCD (PQCD) for exclusive processes by considering $\pi\gamma^*\to \gamma(\pi)$ and $B\to\gamma(\pi) l\bar\nu$. The relevant form factors are expressed as the convolution of hard amplitudes with two-parton meson wave functions in the impact parameter $b$ space, $b$ being conjugate to the parton transverse momenta $k_T$. The point is that on-shell valence partons carry longitudinal momenta initially, and acquire $k_T$ through collinear gluon exchanges. The $b$-dependent two-parton wave functions with an appropriate path for the Wilson links are gauge-invariant. The hard amplitudes, defined as the difference between the parton-level diagrams of on-shell external particles and their collinear approximation, are also gauge-invariant. We compare the predictions for two-body nonleptonic $B$ meson decays derived from $k_T$ factorization (the PQCD approach) and from collinear factorization (the QCD factorization approach).Comment: 11 pages, REVTEX, 5 figure

Imaging of Low Compressibility Strips in the Quantum Hall Liquid

Using Subsurface Charge Accumulation scanning microscopy we image strips of low compressibility corresponding to several integer Quantum Hall filling factors. We study in detail the strips at Landau level filling factors $\nu =$ 2 and 4. The observed strips appear significantly wider than predicted by theory. We present a model accounting for the discrepancy by considering a disorder-induced nonzero density of states in the cyclotron gap.Comment: 5 pages, 3 figure

Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach

The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD approach. It is found that form factors and branching ratios are sensitive to the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of the charmonium wave functions for Coulomb potential and harmonic oscillator potential, respectively, f_J/psi and f_etac are the decay constants of the J/psi and etac mesons, respectively. The large branching ratios and the clear signals of the final states make the Bc --> J/psi pi, etac pi decays to be the prospective channels for measurements at the hadron collidersComment: 21 pages, revtex

Classification and nondegeneracy of SU(n+1)SU(n+1) Toda system with singular sources

We consider the following Toda system \Delta u_i + \D \sum_{j = 1}^n a_{ij}e^{u_j} = 4\pi\gamma_{i}\delta_{0} \text{in}\mathbb R^2, \int_{\mathbb R^2}e^{u_i} dx -1$,$\delta_0$is Dirac measure at 0, and the coefficients$a_{ij}$form the standard tri-diagonal Cartan matrix. In this paper, (i) we completely classify the solutions and obtain the quantization result:$$\sum_{j=1}^n a_{ij}\int_{\R^2}e^{u_j} dx = 4\pi (2+\gamma_i+\gamma_{n+1-i}), \;\;\forall\; 1\leq i \leq n.$$This generalizes the classification result by Jost and Wang for$\gamma_i=0$,$\forall \;1\leq i\leq n$. (ii) We prove that if$\gamma_i+\gamma_{i+1}+...+\gamma_j \notin \mathbb Z$for all$1\leq i\leq j\leq n$, then any solution$u_i$ is \textit{radially symmetric} w.r.t. 0. (iii) We prove that the linearized equation at any solution is \textit{non-degenerate}. These are fundamental results in order to understand the bubbling behavior of the Toda system.Comment: 28 page

Observation of the screening signature in the lateral photovoltage of electrons in the Quantum Hall regime

The lateral photovoltage generated in the plane of a two-dimensional electron system (2DES) by a focused light spot, exhibits a fine-structure in the quantum oscillations in a magnetic field near the Quantum Hall conductivity minima. A double peak structure occurs near the minima of the longitudinal conductivity oscillations. This is the characteristic signature of the interplay between screening and Landau quantization.Comment: 4 pages, 4 figures, to be published in Phys. Rev.

B→KB\to K Transition Form Factor up to O(1/mb2){\cal O}(1/m^2_b) within the kTk_T Factorization Approach

In the paper, we apply the $k_T$ factorization approach to deal with the $B\to K$ transition form factor $F^{B\to K}_{+,0}(q^2)$ in the large recoil regions. The B-meson wave functions $\Psi_B$ and $\bar\Psi_B$ that include the three-particle Fock states' contributions are adopted to give a consistent PQCD analysis of the form factor up to ${\cal O} (1/m^2_b)$. It has been found that both the wave functions $\Psi_B$ and $\bar\Psi_B$ can give sizable contributions to the form factor and should be kept for a better understanding of the $B$ meson decays. Then the contributions from different twist structures of the kaon wavefunction are discussed, including the $SU_f(3)$-breaking effects. A sizable contribution from the twist-3 wave function $\Psi_p$ is found, whose model dependence is discussed by taking two group of parameters that are determined by different distribution amplitude moments obtained in the literature. It is also shown that $F^{B\to K}_{+,0}(0)=0.30\pm0.04$ and $[F^{B\to K}_{+,0}(0)/F^{B\to \pi}_{+,0}(0)]=1.13\pm0.02$, which are more reasonable and consistent with the light-cone sum rule results in the large recoil regions.Comment: 22 pages and 6 figure