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

Σ−p\Sigma^- p emission rates in K−K^- absorptions at rest on 6^6Li, 7^7Li, 9^{9}Be, 13^{13}C and 16^{16}O

An experimental study of the $K^-_{stop}A\rightarrow \Sigma^- p A'$ reaction on $A=^6$Li, $^7$Li, $^9$Be, $^{13}$C and $^{16}$O $p$-shell nuclei is presented. The data were collected by the FINUDA spectrometer operating at the DA$\Phi$NE $\phi$-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 $(np)$ pair embedded in the $A$ 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 K−K^- in 6^6Li and 12^{12}C with FINUDA

Momenta spectra of protons emitted following the capture of $K^-$ in $^6$Li and $^{12}$C have been measured with 1% resolution. The $^{12}$C spectrum is smooth whereas for $^6$Li a well defined peak appears at about 500 MeV/$c$. The first observation of a structure in this region was identified as a strange tribaryon or, possibly, a $\bar K$-nuclear state. The peak is correlated with a $\pi^-$ coming from $\Sigma^-$ decay in flight, selected by setting momenta larger than 275 MeV/$c$. The $\Sigma^-$ could be produced, together with a 500 MeV/$c$ proton, by the capture of a $K^-$ in a deuteron-cluster substructure of the $^6$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 $^4$He targets and with the hypothesis that the $^6$Li nucleus can be interpreted as a $(d+\alpha)$ 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 7^7Li, 9^9Be, 13^{13}C and 16^{16}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 $\pi^-$, binding energies and formation probabilities of $^7_{\Lambda}$Li, $^9_{\Lambda}$Be, $^{13}_{\Lambda}$C and $^{16}_{\Lambda}$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 A(Kstop−,π±Σ∓)A′A(K^-_{stop},\pi^\pm\Sigma^\mp)A' reaction on p-shell nuclei

This letter is concerned with the study of the $K^-_{stop}A\rightarrow \pi^\pm\Sigma^\mp A'$ reaction in p-shell nuclei, i.e., $^{6,7}Li$, $^9Be$, $^{13}C$ and $^{16}O$. The $\pi^\pm\Sigma^\mp / K^-_{stop}$ emission rates are reported as a function of $A$. These rates are discussed in comparison with previous findings. The ratio $\pi^-\Sigma^+/\pi^+\Sigma^-$ 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 $\Lambda(1405)$. The continuum momentum spectra of prompt pions and free sigmas are also discussed as well as the $\pi^\pm\Sigma^\mp$ missing mass behavior and the link with the reaction mechanism. The apparatus used for the investigation is the FINUDA spectrometer operating at the DA$\Phi$NE $\phi$-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 Λd\Lambda d pairs from the Kstop−A→ΛdA′K^{-}_{stop} A \to \Lambda d A' reaction

Correlated $\Lambda d$ pairs emitted after the absorption of negative kaons at rest $K^{-}_{stop}A\to \Lambda d A'$ in light nuclei $^6Li$ and $^{12}C$ are studied. $\Lambda$-hyperons and deuterons are found to be preferentially emitted in opposite directions. The $\Lambda d$ invariant mass spectrum of $^6Li$ shows a bump whose mass is 3251$\pm$6 MeV/c$^2$. The bump mass (binding energy), width and yield are reported. The appearance of a bump is discussed in the realm of the [$\bar{K}3N$] clustering process in nuclei. The experiment was performed with the FINUDA spectrometer at DA$\Phi$NE (LNF).Comment: 13 pages, 5 figures, accepted for publication in Phys. Lett.