2,267 research outputs found
First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell {\Lambda}-Hypernuclei
Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of
eight Lambda-Hypernuclei (A = 5-16) have been revisited. New values of the
ratio of the two-nucleon and the one-proton induced decay widths,
Gamma_2N/Gamma_p, are obtained from single proton spectra, Gamma_2N/Gamma_p =
0.50 +/- 0.24, and from neutron and proton coincidence spectra,
Gamma_2N/Gamma_p = 0.36 +/- 0.14stat +0.05sys -0.04sys , in full agreement with
previously published ones. With these values, a method is developed to extract
the one-proton induced decay width in units of the free Lambda decay width,
Gamma_p/Gamma_Lambda, without resorting to Intra Nuclear Cascade models but by
exploiting only experimental data, under the assumption of a linear dependence
on A of the Final State Interaction contribution. This is the first systematic
determination ever done and it agrees within the errors with recent theoretical
calculations.Comment: 16 pages, 3 figures, 2 table
emission rates in absorptions at rest on Li, Li, Be, C and O
An experimental study of the reaction
on Li, Li, Be, C and O -shell nuclei is
presented. The data were collected by the FINUDA spectrometer operating at the
DANE -factory (LNF-INFN, Italy). Emission rates for the reaction in
the mentioned nuclei are measured and compared with the few existing data. The
spectra of several observables are discussed; indications of Quasi-Free
absorptions by a pair embedded in the nucleus can be obtained from
the study of the missing mass distributions.Comment: Version accepted by PR
A study of the proton spectra following the capture of in Li and C with FINUDA
Momenta spectra of protons emitted following the capture of in Li
and C have been measured with 1% resolution. The C spectrum is
smooth whereas for Li a well defined peak appears at about 500 MeV/. The
first observation of a structure in this region was identified as a strange
tribaryon or, possibly, a -nuclear state. The peak is correlated with a
coming from decay in flight, selected by setting momenta
larger than 275 MeV/. The could be produced, together with a 500
MeV/ proton, by the capture of a in a deuteron-cluster substructure of
the Li nucleus. The capture rate for such a reaction is (1.62\pm
0.23_{stat} ^{+0.71}_{-0.44}(sys))%/K^-_{stop}, in agreement with the existing
observations on He targets and with the hypothesis that the Li nucleus
can be interpreted as a cluster.Comment: 21 pages, 10 figures. Accepted for publication in NP
INFN What Next: Ultra-relativistic Heavy-Ion Collisions
This document was prepared by the community that is active in Italy, within
INFN (Istituto Nazionale di Fisica Nucleare), in the field of
ultra-relativistic heavy-ion collisions. The experimental study of the phase
diagram of strongly-interacting matter and of the Quark-Gluon Plasma (QGP)
deconfined state will proceed, in the next 10-15 years, along two directions:
the high-energy regime at RHIC and at the LHC, and the low-energy regime at
FAIR, NICA, SPS and RHIC. The Italian community is strongly involved in the
present and future programme of the ALICE experiment, the upgrade of which will
open, in the 2020s, a new phase of high-precision characterisation of the QGP
properties at the LHC. As a complement of this main activity, there is a
growing interest in a possible future experiment at the SPS, which would target
the search for the onset of deconfinement using dimuon measurements. On a
longer timescale, the community looks with interest at the ongoing studies and
discussions on a possible fixed-target programme using the LHC ion beams and on
the Future Circular Collider.Comment: 99 pages, 56 figure
Hypernuclear spectroscopy with K at rest on Li, Be, C and O
The FINUDA experiment collected data to study the production of hypernuclei
on different nuclear targets. The hypernucleus formation occurred through the
strangeness-exchange reaction K^-_{stop} + \; ^AZ \rightarrow \; ^A_{\Lambda}Z
+ \pi^-. From the analysis of the momentum of the emerging , binding
energies and formation probabilities of Li, Be,
C and O have been measured and are here
presented. The behavior of the formation probability as a function of the
atomic mass number A is also discussed.Comment: Accepted for publication in PL
Características termogravimétricas e combustão da madeira de Tachigali vulgaris proveniente de plantios com diferentes espaçamentos.
O Tachigali vulgaris (tachi-branco) é uma espécie madeireira da Amazônia, comumente utilizada para finalidades energéticas por populações locais. O conhecimento da cinética de degradação térmica da sua madeira é essencial para adequar os processos de conversão termoquímica visando à produção direta de energia ou de carvão vegetal. Portanto, o objetivo deste estudo foi avaliar o comportamento térmico da madeira do tachi-branco proveniente de diferentes espaçamentos de plantio, durante a combustão e pirólise. Foram coletadas árvores da espécie aos 87 meses de idade de um plantio experimental, localizado no Distrito de Monte Dourado, Pará, Brasil, cultivadas em diferentes espaçamentos de 3,0 x 1,5 m, 3,0 x 2,0 m, 3,0 x 2,5 m, 3,0 x 3,0 m, 3,0 x 3,5 m e 3,0 x 4,0 m. Para a pirólise da madeira, as curvas TG (termogravimétrica) e DTG (primeira derivada da termogravimétrica), sob atmosfera inerte de nitrogênio, exibiram três estágios distintos de perda de massa, correspondentes à degradação térmica das hemiceluloses, celulose e lignina. A faixa de temperatura para a decomposição das hemiceluloses variou de 280°C a 320°C, com perda de massa de 17%. Para a celulose a faixa foi de 340°C a 380°C com perda de massa de aproximadamente 50%. A partir de temperaturas próximas a 400°C, a degradação térmica da madeira diminuiu, correspondendo principalmente à degradação de lignina, com perda de massa de 5%. Madeiras provenientes dos espaçamentos 3,0 x 2,0 m, 3,0 x 2,5 m e 3,0 x 3,0 m foram as que apresentaram maior massa residual, o que sugere maior rendimento em carvão vegetal. Para a combustão, observaram-se duas reações principais de decomposição, correspondendo à volatilização das hemiceluloses, celulose e parte da lignina. No segundo estágio, ocorreu a decomposição da lignina remanescente e do carbono fixo. Independente do espaçamento de plantio, a baixa temperatura de ignição (233,7°C), aliada à elevada temperatura final da combustão (451,6°C) e ao elevado índice de ignição (4 x 103%/min3), demonstram que a espécie apresenta características adequadas para a produção direta de energia térmica
The reaction on p-shell nuclei
This letter is concerned with the study of the reaction in p-shell nuclei, i.e., , ,
and . The emission rates are
reported as a function of . These rates are discussed in comparison with
previous findings. The ratio in p-shell nuclei is
found to depart largely from that on hydrogen, which provides support for large
in-medium effects possibly generated by the sub-threshold . The
continuum momentum spectra of prompt pions and free sigmas are also discussed
as well as the missing mass behavior and the link with the
reaction mechanism. The apparatus used for the investigation is the FINUDA
spectrometer operating at the DANE -factory (LNF-INFN, Italy).Comment: 14 pages, 5 figures, accepted for publication in Phys. Lett.
Variations in productivity and wood properties of Amazonian tachi-branco trees planted at different spacings for bioenergy purposes.
Tachi-branco (Tachigali vulgaris, L.F.Gomes da Silva & H.C.Lima) is a leguminous tree species native to the Amazon rainforest that has drawn attention for its remarkably fast growth, a required trait for biomass/bioenergy plantations. In evaluations of biomass production and wood properties of T. vulgaris planted in homogeneous plantations at different spacings in the Amazonian state of Pará, Brazil, biomass of 7-year-old trees was quantified for individual trees and the entire population. Wood was also sampled to assess properties relevant to bioenergy applications. The choice for spacing dimension for planting nonclonal T. vulgaris should consider whether the priority is greater productivity per tree, achieved with greater spacings (9.0 m2 and 12.0 m2), or productivity per area, achieved with closer spacings (6.0 m2 and 7.5 m2). Genetic variability of the T. vulgaris seed stand and/or high heritability of wood traits overcame the effect of different spacing on all morphological, physical, chemical and energetic properties of T. vulgaris wood. This species has moderate basic density when cultivated at spacings larger than 6 m2 and net heating value above 7.95 MJ/kg, which is suitable for bioenergy purposes. The high variation in wood properties within tree spacing is strongly indicative of great potential for genetic breeding. The fast growth and the suitable moderate wood basic density confirm the outstanding potential of homogeneous plantations of T. vulgaris for providing wood for bioenergy.Publicado Online em 18 nov. 2019
Correlated pairs from the reaction
Correlated pairs emitted after the absorption of negative kaons
at rest in light nuclei and are
studied. -hyperons and deuterons are found to be preferentially
emitted in opposite directions. The invariant mass spectrum of
shows a bump whose mass is 32516 MeV/c. The bump mass (binding
energy), width and yield are reported. The appearance of a bump is discussed in
the realm of the [] clustering process in nuclei. The experiment was
performed with the FINUDA spectrometer at DANE (LNF).Comment: 13 pages, 5 figures, accepted for publication in Phys. Lett.
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