Moments of Nucleon Light Cone Quark Distributions Calculated in Full Lattice QCD

Moments of the quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD. Calculations of proton matrix elements of operators corresponding to these moments through the operator product expansion have been performed on $16^3 \times 32$ lattices for Wilson fermions at $\beta = 5.6$ using configurations from the SESAM collaboration and at $\beta = 5.5$ using configurations from SCRI. One-loop perturbative renormalization corrections are included. At quark masses accessible in present calculations, there is no statistically significant difference between quenched and full QCD results, indicating that the contributions of quark-antiquark excitations from the Dirac Sea are small. Close agreement between calculations with cooled configurations containing essentially only instantons and the full gluon configurations indicates that quark zero modes associated with instantons play a dominant role. Naive linear extrapolation of the full QCD calculation to the physical pion mass yields results inconsistent with experiment. Extrapolation to the chiral limit including the physics of the pion cloud can resolve this discrepancy and the requirements for a definitive chiral extrapolation are described.Comment: 53 Pages Revtex, 26 Figures, 9 Tables. Added additional reference and updated referenced data in Table I

Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance

We have made a first measurement of the lepton momentum spectrum in a sample of events enriched in neutral B's through a partial reconstruction of B0 --> D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the Upsilon(4S) resonance by the CLEO II detector, is compared directly to the inclusive lepton spectrum from all Upsilon(4S) events in the same data set. These two spectra are consistent with having the same shape above 1.5 GeV/c. From the two spectra and two other CLEO measurements, we obtain the B0 and B+ semileptonic branching fractions, b0 and b+, their ratio, and the production ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950 (+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57 +- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes, tau+/tau0.Comment: 14 page, postscript file also available at http://w4.lns.cornell.edu/public/CLN

Observation of the Ξc+\Xi_c^+ Charmed Baryon Decays to Σ+K−π+\Sigma^+ K^-\pi^+, Σ+Kˉ∗0\Sigma^+ \bar{K}^{*0}, and ΛK−π+π+\Lambda K^-\pi^+\pi^+

We have observed two new decay modes of the charmed baryon $\Xi_c^+$ into $\Sigma^+ K^-\pi^+$ and $\Sigma^+ \bar{K}^{*0}$ using data collected with the CLEO II detector. We also present the first measurement of the branching fraction for the previously observed decay mode $\Xi_c^+\to\Lambda K^-\pi^+\pi^+$. The branching fractions for these three modes relative to $\Xi_c^+\to\Xi^-\pi^+\pi^+$ are measured to be $1.18 \pm 0.26 \pm 0.17$, $0.92 \pm 0.27 \pm 0.14$, and $0.58 \pm 0.16 \pm 0.07$, respectively.Comment: 12 page uuencoded postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

Aboveground biomass of a "campina" ecosystem in Roraima, Northern of Brazilian Amazonia

The aboveground biomass of a "campina" ecosystem was estimated in Roraima, in the northern portion of Brazilian Amazonia. The biomass was determined from a phytosociological inventory (1 ha) and distributed between two categories: (1) grassy-woody, composed of "herbs+lichens" (Poaceae, Cyperaceae, Eriocaulaceae, Cladonia spp), Bromeliaceae, seedlings, fine and coarse litter and, (2) woody, composed of trees and bushes. The grassy-woody category was estimated by the direct method (cutting and weighing) in 10 1-m² plots, taking advantage of transects of the inventory. The category woody was estimated by the indirect method cutting 98 individuals of different species and diameters. A model was generated to express the relationship among total dry above-ground biomass (kg), base circumference (cm) and total height (m) for the individuals in this category. The equation was applied to the 3,966 ind.ha-1 observed in the inventory. The total biomass was estimated at 15.91 t.ha-1, of which 2.20 ± 0.23 t.ha-1 (13.8%) was in the grassy-woody category and 13.70 ± 7.13 t.ha-1 (86.2%) in woody category. The tree species with the highest biomass was Humiria balsamifera (Aubl.) St. Hill. (8.43 t.ha-1), followed by Pagamea guianensis Aubl. (1.14 t.ha-1). These results are important for refining the calculations of greenhouse-gas emissions from burning and decomposition of above-ground biomass in "campina" ecosystems in the Amazon region.Foi estimada a biomassa (viva + morta) acima do solo de um ecossistema de "campina" localizado em Roraima, norte da Amazônia brasileira. A biomassa foi determinada a partir de um inventário fitossociológico (1 ha amostral) e distribuída em dois estratos(1) gramíneo-lenhoso, composto de "ervas + liquens" (Poaceae, Cyperaceae, Eriocaulaceae, Cladonia spp), Bromeliaceae, plântulas, "litter" fino e grosso e, (2) arbóreo-arbustivo, composto por árvores e arbustos. O estrato gramíneo-lenhoso foi estimado pelo método direto (corte e pesagem) através de 10 quadras de 1m², aproveitando os transectos do inventário. O estrato arbóreo-arbustivo foi estimado pelo método indireto com o corte de 98 indivíduos de diferentes espécies e diâmetros. Foi gerado um modelo para expressar a relação entre a biomassa seca total (kg), a circunferência de base (cm) e a altura total (m) para os indivíduos deste estrato. A equação foi aplicada nos 3.966 indivíduos.ha-1 observados no inventário. A biomassa total foi estimada em 15,91 t.ha-1, sendo 2,20 ± 0,23 t.ha-1 (13,8%) do estrato gramíneo-lenhoso e 13,70 ± 7,13 t.ha-1 (86,2%) do arbóreo-arbustivo. A espécie arbórea de maior biomassa foi Humiria balsamifera (Aubl.) St. Hill. (8,43 t.ha-1), seguida de Pagamea guianensis Aubl. (1,14 t.ha-1). Estes resultados são importantes para refinar os cálculos de emissão de gases do efeito estufa pela queima e decomposição da biomassa acima do solo em ecossistemas de campinas na Amazônia

Studies of the Cabbibo-Suppressed Decays D+→π0ℓ+νD^+ \to \pi^0 \ell^+ \nu and D+→ηe+νeD^+ \to \eta e^+ \nu_e

Using 4.8 fb$^{-1}$ of data taken with the CLEO II detector, the branching fraction for the Cabibbo-suppressed decay $D^+\to\pi^0\ell^+\nu$ measured relative to the Cabibbo favored decay $D^+\to\bar{K^0}\ell^+\nu$ is found to be $0.046\pm 0.014\pm 0.017$. Using $V_{cs}$ and $V_{cd}$ from unitarity constraints, we determine $| f_+^{\pi}(0)/f_+^K(0)|^2=0.9\pm 0.3\pm 0.3$ We also present a 90% confidence level upper limit for the branching ratio of the decay $D^+ \to \eta e^+\nu_e$ relative to that for $D^+ \to \pi^0 e^+\nu_e$ of 1.5.Comment: 10 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN