Constraints on the Leading-Twist Pion Distribution Amplitude from A QCD Light-Cone Sum Rule with Chiral Current

We present an improved analysis of the constraints on the first two Gegenbauer moments, $a^\pi_2$ and $a^\pi_4$, of the pion's leading-twist distribution amplitude from a QCD light-cone sum rule analysis of $B\to\pi$ weak transition form factor $f_{+}(q^2)$. Proper chiral current is adopted in QCD light-cone sum rule so as to eliminate the most uncertain twist-3 contributions to $f_{+}(q^2)$, and then we concentrate our attention on the properties of the leading-twist pion DA. A nearly model-independent $f_+(q^2)$ as shown in Ref.\cite{pball0} that is based on the spectrum of $B\to\pi l\nu$ decays from BaBar, together with their uncertainties, are adopted as the standard shape for $f_+(q^2)$ to do our discussion. From a minimum $\chi^2$-fit and by taking the theoretical uncertainties into account, we obtain $a^\pi_2(1GeV)=0.17^{+0.15}_{-0.17}$ and $a^\pi_4(1GeV)=-0.06^{+0.20}_{-0.22}$ at the $1\sigma$ confidence level for $m^*_b\in[4.7,4,8] GeV$.Comment: 10 pages, 4 figures. References added. To be published in EPJ

Exclusive processes in position space and the pion distribution amplitude

We suggest to carry out lattice calculations of current correlators in position space, sandwiched between the vacuum and a hadron state (e.g. pion), in order to access hadronic light-cone distribution amplitudes (DAs). In this way the renormalization problem for composite lattice operators is avoided altogether, and the connection to the DA is done using perturbation theory in the continuum. As an example, the correlation function of two electromagnetic currents is calculated to the next-to-next-to-leading order accuracy in perturbation theory and including the twist-4 corrections. We argue that this strategy is fully competitive with direct lattice measurements of the moments of the DA, defined as matrix elements of local operators, and offers new insight in the space-time picture of hard exclusive reactions.Comment: 15 pages, 10 figure

The B-Meson Distribution Amplitude in QCD

The B-meson distribution amplitude is calculated using QCD sum rules. In particular we obtain an estimate for the integral relevant to exclusive B-decays \lambda_B = 460 \pm 110 MeV at the scale 1 GeV. A simple QCD-motivated parametrization of the distribution amplitude is suggested.Comment: 17 pages, 8 figures, Latex styl

The action of all-trans-retinoic acid (ATRA) and synthetic retinoid analogues (EC19 and EC23) on human pluripotent stem cells differentiation investigated using single cell infrared microspectroscopy

All trans-retinoic acid (ATRA) is widely used to direct the differentiation of cultured stem cells. When exposed to the pluripotent human embryonal carcinoma (EC) stem cell line, TERA2.cl.SP12, ATRA induces ectoderm differentiation and the formation of neuronal cell types. We have previously generated synthetic analogues of retinoic acid (EC23 and EC19) which also induce the differentiation of EC cells. Even though EC23 and EC19 have similar chemical structures, they have differing biochemical effects in terms of EC cell differentiation. EC23 induces neuronal differentiation in a manner similar to ATRA, whereas EC19 directs the cells to form epithelial-like derivatives. Previous MALDI-TOF MS analysis examined the response of TERA2.cl.SP12 cells after exposure to ATRA, EC23 and EC19 and further demonstrated the similarly in the effect of ATRA and EC23 activity whilst responses to EC19 were very different. In this study, we show that Fourier Transform Infrared Micro-Spectroscopy (FT-IRMS) coupled with appropriate scatter correction and multivariate analysis can be used as an effective tool to further investigate the differentiation of human pluripotent stem cells and monitor the alternative affects different retinoid compounds have on the induction of differentiation. FT-IRMS detected differences between cell populations as early as 3 days of compound treatment. Populations of cells treated with different retinoid compounds could easily be distinguished from one another during the early stages of cell differentiation. These data demonstrate that FT-IRMS technology can be used as a sensitive screening technique to monitor the status of the stem cell phenotype and progression of differentiation along alternative pathways in response to different compounds

Effect of interpregnancy interval on gestational diabetes: a retrospective matched cohort study

© 2019 The Authors Purpose: To examine the association between interpregnancy interval (IPI) and gestational diabetes using both within-mother and between-mother comparisons. Methods: A retrospective cohort study of 103,909 women who delivered three or more consecutive singleton births (n = 358,046) between 1 January 1980 and 31 December 2015 in Western Australia. The association between IPI and gestational diabetes was estimated using conditional logistic regression, matching pregnancies to the same mother and adjusted for factors that vary within-mother across pregnancies. For comparison with previous studies, we also applied unmatched logistic regression (between-mother analysis). Results: The conventional between-mother analysis resulted in adjusted odds ratios (aOR) of 1.13 (95% CI, 1.06–1.21) for intervals of 24–59 months and 1.51 (95% CI, 1.33–1.70) for intervals of 120 or more months, compared with IPI of 18–23 months. In addition, short IPIs were associated with lower odds of gestational diabetes with (aOR: 0.89; 95% CI, 0.82–0.97) for 6–11 months and (aOR: 0.92; 95% CI, 0.85–0.99) for 12–17-month. In comparison, the adjusted within-mother matched analyses showed no statistically significant association between IPIs and gestational diabetes. All effect estimates were attenuated using the within-mother matched model. Conclusion: Our findings do not support the hypothesis that short IPI (<6 months) increases the risk of gestational diabetes and suggest that observed associations in previous research might be attributable to confounders that vary between mothers

A lattice calculation of vector meson couplings to the vector and tensor currents using chirally improved fermions

We present a quenched lattice calculation of $f_V^\perp/f_V$, the coupling of vector mesons to the tensor current normalized by the vector meson decay constant. The chirally improved lattice Dirac operator, which allows us to reach small quark masses, is used. We put emphasis on analyzing the quark mass dependence of $f_V^\perp/f_V$ and find only a rather weak dependence. Our results at the $\rho$ and $\phi$ masses agree well with QCD sum rule calculations and those from previous lattice studies.Comment: 6 pages, 3 figures, one sentence remove

Rare Decays of \Lambda_b->\Lambda + \gamma and \Lambda_b ->\Lambda + l^{+} l^{-} in the Light-cone Sum Rules

Within the Standard Model, we investigate the weak decays of $\Lambda_b \to \Lambda + \gamma$ and $\Lambda_b \to \Lambda + l^{+} l^{-}$ with the light-cone sum rules approach. The higher twist distribution amplitudes of $\Lambda$ baryon to the leading conformal spin are included in the sum rules for transition form factors. Our results indicate that the higher twist distribution amplitudes almost have no influences on the transition form factors retaining the heavy quark spin symmetry, while such corrections can result in significant impacts on the form factors breaking the heavy quark spin symmetry. Two phenomenological models (COZ and FZOZ) for the wave function of $\Lambda$ baryon are also employed in the sum rules for a comparison, which can give rise to the form factors approximately 5 times larger than that in terms of conformal expansion. Utilizing the form factors calculated in LCSR, we then perform a careful study on the decay rate, polarization asymmetry and forward-backward asymmetry, with respect to the decays of $\Lambda_b \to \Lambda \gamma$, $\Lambda l^{+}l^{-}$.Comment: 38 pages, 15 figures, some typos are corrected and more references are adde

Nonfactorizable contributions to B→D(∗)MB \to D^{(*)} M decays

While the factorization assumption works well for many two-body nonleptonic $B$ meson decay modes, the recent measurement of $\bar B\to D^{(*)0}M^0$ with $M=\pi$, $\rho$ and $\omega$ shows large deviation from this assumption. We analyze the $B\to D^{(*)}M$ decays in the perturbative QCD approach based on $k_T$ factorization theorem, in which both factorizable and nonfactorizable contributions can be calculated in the same framework. Our predictions for the Bauer-Stech-Wirbel parameters, $|a_2/a_1|= 0.43\pm 0.04$ and $Arg(a_2/a_1)\sim -42^\circ$ and $|a_2/a_1|= 0.47\pm 0.05$ and $Arg(a_2/a_1)\sim -41^\circ$, are consistent with the observed $B\to D\pi$ and $B\to D^*\pi$ branching ratios, respectively. It is found that the large magnitude $|a_2|$ and the large relative phase between $a_2$ and $a_1$ come from color-suppressed nonfactorizable amplitudes. Our predictions for the ${\bar B}^0\to D^{(*)0}\rho^0$, $D^{(*)0}\omega$ branching ratios can be confronted with future experimental data.Comment: 25 pages with Latex, axodraw.sty, 6 figures and 5 tables, Version published in PRD, Added new section 5 and reference

Study of B→D∗∗πB\to D^{**} \pi decays

We investigate the production of the novel $P$-wave mesons $D^{*}_{0}$ and $D^{\prime}_{1} (D_{1})$, identified as $J^{P}=0^+$ and $1^+$, in heavy $B$ meson decays, respectively. With the heavy quark limit, we give our modelling wave functions for the scalar meson $D^{*}_{0}$. Based on the assumptions of color transparency and factorization theorem, we estimate the branching ratios of $B\to D^{*}_{0} \pi$ decays in terms of the obtained wave functions. Some remarks on $D^{(\prime)}_{1}$ productions are also presented.Comment: 16 pages, 2 figures, Revtex4, to be published in Phys. Rev.

Exclusive semileptonic B_s decays to excited D_s mesons: Search of D_{sJ}(2317) and D_{sJ}(2460)

We study the exclusive semileptonic decays B_s->D_{s0}^*\ell\bar\nu and B_s->D_{s1}^*\ell\bar\nu, where p-wave excited D_{s0}^* and D_{s1}^* states are identified with the newly observed D_{sJ}(2317) and D_{sJ}(2460) states. Within the framework of HQET the Isgur-Wise functions up to the subleading order of the heavy quark expansion are calculated by QCD sum rules. The decay rates and branching ratios are computed with the inclusion of the order of 1/m_Q corrections. We point out that the investigation of the B_s semileptonic decays to excited D_s mesons may provide some information about the nature of the new D_{sJ}^* mesons.Comment: 15 pages, 6 eps figures, RevTeX 4, accepted for publication in Phys. Rev.