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Model independent reconstruction of impact parameter distributions for intermediate energy heavy ion collisions
No full text14 pages, 7 figures. Revised version accepted for publication in Physical Review CInternational audienceWe present a model-independent method to reconstruct the impact parameter distributions of experimental data for intermediate energy heavy ion collisions, adapted from a recently proposed approach for ultra-relativistic heavy ion collisions. The method takes into account the fluctuations which are inherent to the relationship between any experimental observable and the impact parameter in this energy range. We apply the method to the very large dataset on heavy ion collisions in the energy range 20-100 MeV/nucleon obtained with the INDRA multidetector since 1993, for two observables which are the most commonly used for the estimation of impact parameters in this energy range. The mean impact parameters deduced with this new method for "central" collisions selected using typical observable cuts are shown to be significantly larger than those found when fluctuations are neglected, and as expected the difference increases as bombarding energy decreases. In addition, we will show that this new approach may provide previously inaccessible experimental constraints for transport models, such as an estimation of the extrapolated mean value of experimental observables for b = 0 collisions. The ability to give more realistic, model-independent, estimations of the impact parameters associated to different experimental datasets should improve the pertinence of comparisons with transport model calculations which are essential to better constrain the equation of state of nuclear matter
Inclusive heavy-flavour production at central and forward rapidity in Xe-Xe collisions at =5.44$ TeV
No full textInternational audienceThe first measurements of the production of muons and electrons from heavy-flavour hadron decays in Xe–Xe collisions at sNN=5.44 TeV, using the ALICE detector at the LHC, are reported. The measurement of the nuclear modification factor RAA is performed as a function of transverse momentum pT in several centrality classes at forward rapidity ( 2.5<y<4 ) and midrapidity ( |y|<0.8 ) for muons and electrons from heavy-flavour hadron decays, respectively. A suppression by a factor up to about 2.5 compared to the binary-scaled pp reference is observed in central collisions at both central and forward rapidities. The RAA of muons from heavy-flavour hadron decays is compared to previous measurements in Pb–Pb collisions at sNN=5.02 TeV. When the nuclear modification factors are compared in the centrality classes 0–10% for Xe–Xe collisions and 10–20% for Pb–Pb collisions, which have similar charged-particle multiplicity density, a similar suppression, with RAA∼0.4 in the pT interval 4<pT<8 GeV/ c , is observed. The comparison of the measured RAA values in the two collision systems brings new insights on the properties of the quark-gluon plasma by investigating the system-size and geometry dependence of medium-induced parton energy loss. The results of muons and electrons from heavy-flavour hadron decays provide new constraints to model calculations
In-medium effects in strangeness production in heavy-ion collisions at (sub-) threshold energies
No full textInternational audienceWe study the in-medium effects in strangeness production in heavyion collisions at (sub-)threshold energies based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach. The in-medium modifications of the antikaon properties are described via the self-consistent coupledchannel unitarized scheme based on a SU(3) chiral Lagrangian while the inmedium modification of kaons are accounted via the kaon-nuclear potential, which is assumed to be proportional to the local baryon density. We find that the modifications of (anti)kaon properties in nuclear matter are necessary to explain the experimental data in heavy-ion collisions
KM3NeT/ARCA expectations in view of a novel multimessenger study of starburst galaxies
No full textInternational audienceStarburst galaxies (SBGs) and more in general star-forming galaxies represent a class of galaxies with a high star formation rate (up to 100M/year). Despite their low luminosity, they can be considered as guaranteed “factories” of high energy neutrinos, being “reservoirs” of accelerated cosmic rays and hosting a high density target gas in the central region. In this contribution we present a novel multimessenger study of these sources and the possibility of observing their neutrino signals with the KM3NeT/ARCA telescope. The differential sensitivity for different SBG scenarios is reported considering track-like neutrino events in the 100 GeV–100 PeV energy range
An R&D program for the research of 2β0ν decay with a SPC
No full textInternational audienceThe objective of the R2D2 R&D is to test the concept of a spherical proportional counter (SPC) for the search of the neutrinoless double beta decay (2β0ν). For this, we built a small prototype (40 cm in diameter), which was filled with an argon-based gas mixture at pressures up to 1.1 bar, and irradiated with a 210 Po alpha source. We report on results obtained in terms of directional, volume, and energy responses. We performed time measurements by combining the charge readout from the SPC with the light detection provided by a SiPM. We also studied the possibilities of localizing tracks in the detector and of discriminating multiple tracks
Immobilization of I in nuclear waste glass matrixes synthesized under high-pressure conditions: an experimental study
No full textInternational audienceThere is major environmental interest in finding a sustainable solution to immobilize 129I, a by-product of the nuclear industry. The use of aluminoborosilicate glasses represents a good compromise. However, this solution does not appear adequate for 129I owing to its volatility at high temperature during the vitrification process. In the present work, we use a high-pressure (1.5 GPa) apparatus to synthesize I-rich aluminoborosilicate glasses. We show that the use of high-pressure conditions enhances the I solubility in glasses by several orders of magnitude as compared to 1 bar synthesis, with I solubility up to 5.7 mol%. We observed that I is more solubilized in Na-rich as compared to Ca-rich glass. Investigation of the I speciation using XPS also reveals that I solubility in glasses is much higher as I dissolves as I5+ in comparison to I−. Our work shows that using high-pressure appears to be a reliable solution for dissolving a large quantity of I within the structure of aluminoborosilicate glasses for the conditioning of nuclear waste. We also demonstrate that the oxidized I waste form should be employed to greatly increase I solubility in nuclear waste glasses. Therefore, it represents a potential pathway for solving the immobilization of 129I produced by anthropic nuclear activity
Total absorption gamma-ray spectroscopy study of the -decay of Hg
No full textInternational audienceThe Gamow-Teller strength distribution of the decay of Hg into Au has been determined for the first time using the total absorption gamma spectroscopy technique and has been compared with theoretical QRPA calculations using the SLy4 Skyrme force. The measured Gamow-Teller strength distribution and the half-life are described by mixing oblate and prolate configurations independently in the parent and daughter nuclei. The best description of the experimental beta strength is obtained with dominantly prolate components for both parent Hg and daughter Au. The approach also allowed us to determine an upper limit of the oblate component in the parent state. The complexity of the analysis required the development of a new approach in the analysis of the X-ray gated total absorption spectrum
Measurement of beauty and charm production in pp collisions at = 5.02 TeV via non-prompt and prompt D mesons
No full textInternational audienceThe p-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity (|y|< 0.5) in proton-proton collisions at = 5.02 TeV. The data sample used in the analysis corresponds to an integrated luminosity of (19.3 ± 0.4) nb. D mesons were reconstructed from their decays D→ Kπ, D→ Kππ, and {\mathrm{D}}_{\mathrm{s}}^{+}\to \upphi {\uppi}^{+}\to {\mathrm{K}}^{-}{\mathrm{K}}^{+}{\uppi}^{+} and their charge conjugates. Compared to previous measurements in the same rapidity region, the cross sections of prompt D and mesons have an extended p coverage and total uncertainties reduced by a factor ranging from 1.05 to 1.6, depending on p, allowing for a more precise determination of their p-integrated cross sections. The results are well described by perturbative QCD calculations. The fragmentation fraction of heavy quarks to strange mesons divided by the one to non-strange mesons, f/(f + f), is compatible for charm and beauty quarks and with previous measurements at different centre-of-mass energies and collision systems. The production cross section per rapidity unit at midrapidity, estimated from non-prompt D-meson measurements, is μb. It is compatible with previous measurements at the same centre-of-mass energy and with the cross section pre- dicted by perturbative QCD calculations.[graphic not available: see fulltext
Development of a Reference Database for Beta-Delayed Neutron Emission
No full textInternational audienceBeta-delayed neutron emission is important for nuclear structure and astrophysics as well as for reactor applications. Significant advances in nuclear experimental techniques in the past two decades have led to a wealth of new measurements that remain to be incorporated in the databases.We report on a coordinated effort to compile and evaluate all the available β -delayed neutron emission data. The different measurement techniques have been assessed and the data have been compared with semi-microscopic and microscopic-macroscopic models. The new microscopic database has been tested against aggregate total delayed neutron yields, time-dependent group parameters in 6-and 8-group re-presentation, and aggregate delayed neutron spectra. New recommendations of macroscopic delayed-neutron data for fissile materials of interest to applications are also presented. The new Reference Database for Beta-Delayed Neutron Emission Data is available online at: http://www-nds.iaea.org/beta-delayed-neutron/database.html
