We report on first experimental observations of nuclear fermionic and bosonic components displaying different behaviours in the decay of hot Ca projectile-like sources produced in mid-peripheral ...collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA 4π detector array to the forward angle VAMOS magnetic spectrometer, allowed to reconstruct the mass, charge and excitation energy of the decaying hot projectile-like sources. By means of quantum-fluctuation analysis techniques, temperatures and local partial densities of bosons and fermions could be correlated to the excitation energy of the reconstructed system. The results are consistent with the production of dilute mixed systems of bosons and fermions, where bosons experience higher phase-space and energy density as compared to the surrounding fermionic gas. Our findings recall phenomena observed in the study of Bose condensates and Fermi gases in atomic traps despite the different scales.
Abstract
The dynamics of a nuclear open quantum system could be revealed in the correlations between the breakup fragments of halo nuclei. The breakup mechanism of a proton halo nuclear system is of ...particular interest as the Coulomb polarization may play an important role, which, however, remains an open question. Here we use a highly efficient silicon detector array and measure the correlations between the breakup fragments of
8
B incident on
120
Sn at near-barrier energies. The energy and angular correlations can be explained by a fully quantum mechanical method based on the state-of-the-art continuum discretized coupled channel calculations. The results indicate that, compared to the neutron halo nucleus
6
He,
8
B presents distinctive reaction dynamics: the dominance of the elastic breakup. This breakup occurs mainly via the short-lived continuum states, almost exhausts the
7
Be yield, indicating the effect of Coulomb polarization on the proton halo state. The correlation information reveals that the prompt breakup mechanism dominates, occurring predominantly on the outgoing trajectory. We also show that, as a large environment, the continuum of
8
B breakup may not significantly influence elastic scattering and complete fusion.
Abstract
Directional sensitivity to nuclear recoils would provide a smoking gun for a possible discovery of dark matter in the form of WIMPs (Weakly Interacting Massive Particles). A hint of ...directional dependence of the response of a dual-phase argon Time Projection Chamber (TPC) was found in the SCENE experiment. Given the potential importance of such a capability in the framework of dark matter searches, a new dedicated experiment, ReD (Recoil Directionality), was designed by the Global Argon Dark Matter Collaboration, in order to scrutinise this hint. A small dual-phase argon TPC was irradiated with neutrons produced by the p(
7
Li,
7
Be)n reaction using the 15 MV TANDEM accelerator of the INFN - Laboratori Nazionali del Sud, Catania, Italy, so as to produce argon nuclear recoils in the range (20 - 100) keV of interest for dark matter searches. Energy and direction of nuclear recoils are inferred by the detection of the elastically-scattered neutron by a set of scintillation detectors. Events were selected by gating of the associated
7
Be, which is detected by a telescope of Si detectors.
Abstract
In this work we will document the design and the performances of a SiPM-based photo-detector with a surface area of 100 cm
2
conceived to operate as a replacement for PMTs. The signals from ...94 SiPMs are summed up to produce an aggregated output that exhibits in liquid nitrogen a dark count rate (DCR) lower than 100 cps over the entire surface, a signal to noise ratio better than 13, and a timing resolution better than 5.5 ns. The module feeds about 360 mW at 5 V with a dynamic range in excess of 500 photo-electrons on a 100 Ω differential line. The unit can also operate at room temperature, at the cost of an increase of DCR to 10
8
cps.
Equilibrium constants for hydrogen and helium isotopes as a function of density and temperature are measured in the framework of the study made by Qin et al 2012 Phys. Rev. Lett. 108 172701. We ...review and comment on all stages of the analysis and conclude that our measurements are not inconsistent with the results of Qin et al. Improvements are being made to the initial analysis and we raise the issue of the binding energies which has to be clarified.
By using freeze-out properties of multifragmenting hot nuclei produced in quasifusion central
129
Xe
+
nat
Sn
collisions at different beam energies (32, 39, 45 and 50 AMeV) which were estimated by ...means of a simulation based on experimental data collected by the
4
π
INDRA multidetector, heat capacity in the thermal excitation energy range 4–12.5 AMeV was calculated from total kinetic energies and multiplicities at freeze-out. The microcanonical formulation was employed. Negative heat capacity which signs a first order phase transition for finite systems is observed and confirms previous results using a different method.
The cosmological lithium problem (CLP) stems from the outstanding discrepancy between theoretical predictions and astronomical observations of primordial lithium abundances. For the radiogenic ...production of 7Li, 7Be plays a pivotal role in the Big Bang nucleosynthesis (BBN). Nevertheless, the data for neutron-induced 7Be destruction processes were still sparse, and especially lacked information on the contributions of transitions to the 7Li excited states. In this work, we have determined the 7Be\({(n,{p}_{0})}^{7}\)Li, 7Be\({(n,{p}_{1})}^{7}\)Li*, and 7Be\({(n,\alpha )}^{4}\)He reaction cross sections by means of the Trojan Horse method. The present and the previous data were analyzed together by a multichannel R-matrix fit, providing an improved uncertainty evaluation of the \((n,{p}_{0})\) channel and the first-ever quantification of the \((n,{p}_{1})\) contribution in the BBN-relevant energy range. We implemented the revised total reaction rate summing both the \((n,{p}_{0})\) and \((n,{p}_{1})\) contributions in a state-of-the-art BBN code PRIMAT. As a consequence, the present nuclear-physics data offers a reduction of the predicted 7Li abundance by about one-tenth, which would impose a stricter constraint on BBN and head us in the correct direction to the CLP solution.
Studying interactions of radioactive ions with neutrons is particularly demanding and has been performed only in a few cases. Some of these interactions are crucial in several astrophysical contexts. ...In the present work, the case of the 7Be destruction induced by the (n, ) reaction is investigated at the energies typical of the primordial nucleosynthesis by means of the Trojan Horse Method applied to the 2H(7Be, )p quasi-free reaction. The 7Be(n, )4He cross-section has been measured in a single experiment from ∼2 MeV down to cosmological energies. The corresponding deduced reaction rate has been adopted to evaluate the impact on big bang nucleosynthesis and on the lithium problem.
Abstract Liquid Argon (LAr) Time Projection Chambers (TPC) operating in double-phase can detect the nuclear recoils (NR) possibly caused by the elastic scattering of WIMP dark matter particles via ...light signals from both scintillation and ionization processes. In the scenario of a low-mass WIMP (< 2 GeV/c 2 ), the energy range for the NRs would be below 20 keV, thus making it crucial to characterize the ionization response in LAr TPCs as the lone available detection channel at such low energy. The Recoil Directionality (ReD) project, within the Global Argon Dark Matter Collaboration, aims to measure the ionization yield of a LAr TPC in the recoil energy range of 2–5 keV. The measurement was performed in winter 2023 at the INFN Sezione of Catania and the analysis is ongoing.
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