Two-pion production in deuteron-deuteron collisions at low energies

The cross section for the dd -> 4He pi pi reaction is estimated near threshold in a two-step model where a pion created in a first interaction produces a second pion in a subsequent interaction. This approach, which describes well the rates of 2pi and eta production in the pd -> 3He pi pi and dd -> 4He eta reactions, leads to predictions that are much too low compared to experiment. Alternatives to this and the double-Delta model will have to be sought to explain these data.Comment: 5 pages with 4 postscript figure

Body weight gain and carcass yield of llamas (Lama glama) subjected tofattening under four feeding types

Universidad Nacional Agraria La Molina. Escuela de Posgrado. Maestría en Producción AnimalEl objetivo del estudio fue evaluar la ganancia de peso y rendimiento de carcasa dellamas machos diente de leche sometidas a engorde con cuatro tipos de alimentación (T1:Pastura natural; T2: T1 + dosificación vitamínica; T3: T1 + heno de alfalfa; T4: T2 + henode alfalfa). Se utilizó un diseño completamente al azar con arreglo factorial de 2x2 con unanálisis de covarianza (peso vivo inicial como covariable). Se emplearon 32 llamas asig-nadas al azar a uno de los cuatro tratamientos por 84 días. La carga animal empleada fuede 1.3 unidades llama/ha. La ganancia diaria de peso (GDP) se evaluó en los periodos deengorde a 14, 28, 42, 56, 70 y 84 días. La GDP por periodo de engorde fue significativamentediferente entre periodos, donde los primeros tres periodos (14, 28 y 42 días) mostraronmejor GDP (337, 237 y 160 g/d, respectivamente). La GDP por tipo de alimentación fuemayor en T3 (157 g/d) durante el periodo de 84 días (p<0.01) y el mejor rendimiento decarcasa se obtuvo en T4 (53.60%) seguido por el T3 (53.20%) (p<0.01). Se concluye quela mayor GDP se logra hasta los 42 días y el mejor rendimiento de carcasa se logra en lapastura natural + suplementación con heno de alfalfa (T3)The aim of this study was to evaluate the bodyweight gain and carcass yield ofyoung male llamas (milk tooth) subjected to fattening with four types of feeding (T1:Natural pasture; T2: T1 + vitamin injection; T3: T1 + alfalfa hay; T4: T2 + hay alfalfa). A completely randomized design with a 2x2 factorial arrangement with a covariance analysis(initial live weight as covariate) was used. Thirty-two llamas were randomized assignedto one of the four treatments for 84 days. The stocking rate was 1.3 animal units/ha. Dailyweight gain (DWG) was evaluated in the fattening periods at 14, 28, 42, 56, 70 and 84days. The DWG per fattening period was significantly different between periods, in thefirst three periods (14, 28 and 42 days) showing the best DWG (337, 237 and 160 g/d,respectively). The DWG per feed type was higher in T3 (157 g/d) during the 84-dayperiod (p<0.01) and the best carcass yield was obtained in T4 (53.60%) followed by T3(53.20%) (p<0.01). It is concluded that the highest DWG is achieved at day 42 and thebest carcass yield is obtained with natural pasture + alfalfa hay supplementation (T3)

Near-Threshold Production of omega Mesons in the pp -> pp omega Reaction

The total cross section for omega production in the pp -> pp omega reaction has been measured at five c.m. excess energies from 3.8 to 30 MeV. The energy dependence is easily understood in terms of a strong proton-proton final state interaction combined with a smearing over the width of the state. The ratio of near-threshold phi and omega production is consistent with the predictions of a one-pion-exchange model and the degree of violation of the OZI rule is similar to that found in the pi-p -> n omega/phi reactions.Comment: Report in LaTeX2e. 12 pages with 2 eps figure

Comparison of eta and eta' production in the pp -> pp eta(eta') reactions near threshold

The total cross section of the pp -> pp eta' reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding eta production, in good agreement with the predictions of a one-pion-exchange model.Comment: 10 pages, Latex with 3 eps figure

Subthreshold K+ production in deuteron and alpha induced nuclear reactions

Double differential cross sections have been measured for pi+ and K+ emitted around midraidity in d+A and He+A collisions at a beam kinetic energy of 1.15 GeV/nucleon. The total pi+ yield increases by a factor of about 2 when using an alpha projectile instead of a deuteron whereas the K+ yield increases by a factor of about 4. According to transport calculations, the K+ enhancement depends both on the number of hadron-hadron collisions and on the energy available in those collisions: their center-of-mass energy increases with increasing number of projectile nucleons

Polarisation of the omega meson in the pd-->3He+omega reaction at 1360 and 1450 MeV

The tensor polarisation of omega mesons produced in the pd-->3He+omega reaction has been studied at two energies near threshold. The 3He nuclei were detected in coincidence with the pi0pi+pi- or pi0gamma decay products of the omega. In contrast to the case of phi meson production, the omega mesons are found to be unpolarised. This brings into question the applicability of the Okubo-Zweig-Iizuka rule when comparing the production of vector mesons in low energy hadronic reactions.Comment: 11 pages, 4 figure

The pd --> ^3He eta pi0 reaction at T_p = 1450 MeV

The cross section for the pd --> ^3He eta pi0 reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring and detecting one ^3He and four photons from the decays of the two photons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant masses of all three pairs of final state particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi^0 momentum in the ^3Hepi^0 system.Comment: 10 pages, 5 figure

Livestock keepers’ attitudes: Keystone of effective community-based breeding programs

Livestock keepers in southwestern Burkina Faso hold the local Lobi taurine breed, local Zebu cattle, and their crosses. Some communities in the region have begun to implement community-based cattle breeding programs (CBBPs), which involve animal tagging and recording and, potentially, also bull sharing. Based on the hypothesis that the participation of livestock keepers in CBBPs depends on their attitudes towards these programs, we used questionnaires to survey the attitudes of 125 farmers towards cattle breeding strategies and tools. Results were analyzed using principal component analysis. Farmers showed a highly positive attitude towards maintaining the features of their preferred cattle breed, but their attitudes varied substantially towards crossbreeding for breed improvement. Farmers generally agreed that performance was more important than animal appearance, and most of them were willing to cooperate with breeders’ associations but were skeptical about sharing their bulls with other farmers. The majority was reluctant to record performance data, which may be due to a capacity deficit and their confidence in being able to select the best animals based purely on phenotype. Our analysis suggests that breeders’ associations, as a key component of CBBPs, should lay down clear rules and obligations for their members from the outset. Timely consideration of farmers’ attitudes towards different breeding tools may improve their uptake and guarantee the sustainability of CBBPs