Decay modes of excited compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40... more Decay modes of excited compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40 Ca and 86 Kr+ 48 Ca collisions at 10 A•MeV, are investigated. In particular, the competition between the various disintegration path of medium mass compound nuclei, formed by fusion processes, the production of the so referred Intermediate Mass Fragments (IMF), and the isospin dependence of the decay process are studied. Data were taken at the INFN-Laboratori Nazionali del Sud (LNS) by using the CHIMERA array. Data analysis is in progress; a first indication on the average-energy angular distributions suggests pre-equilibrium effects affecting the data and the presence of isotopical effects.
I. Stefan, 8 C. Stodel, 3 Ch. Theisen, 9 D. Verney, 3 and J.Żylicz IEP, Warsaw University, Ho ża ... more I. Stefan, 8 C. Stodel, 3 Ch. Theisen, 9 D. Verney, 3 and J.Żylicz IEP, Warsaw University, Ho ża 69, PL-00-681 Warszawa, Poland Oak Ridge National Laboratory, Physics Division, Oak Ridge, Tennessee 37831, USA GANIL, Boite Postale 55027, F-14076 Caen Cedex 5, France Gesellschaft für Schwerionenforschung mbH, D-64291 Darmstadt, Germany CEA Bruyéres-le-Châtel DIF/DPTA/SPN, Boite Postale 12, F-91680 Bruyères-le-Châtel, France St. Kliment Ohridski University of Sofia, BG-1164 Sofia, Bulgaria Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA IFIN, P.O. Box MG6, 76900 Bucharest-Magurele, Romania CEA Saclay, DSM/DAPNIA/SPhN, F-91191 Gif sur Yvette Cedex, France Department of Physics, University of Naples “Federico II,” I-80126 Naples, Italy CENBG, Boite Postale 120, F-33175 Gradignan Cedex, France IPN, 91406 Orsay Cedex, France Department of Particle Physics, The Weizmann Institute of Science, 76100 Rehovot, Israel Department of Radiation Sciences...
It has been demonstrated that the particle X-ray coincidence technique (PXCT) [1] can be used to ... more It has been demonstrated that the particle X-ray coincidence technique (PXCT) [1] can be used to get information on lifetimes of excited nuclear states in the time range of 10−15–10−17 s, such data being difficult to access by other methods. The PXCT technique uses an ”atomic clock” (filling of the atomic shell vacancy) to measure the time scale of the nuclear deexcitation process. The βdelayed proton emission following electron capture decay (ECp) is ideally suited for this type of measurements. In this case the PXCT method is based on the following principle: A nucleus (with atomic number Z) decaying, e.g., by K-electron capture to excited state in the daughter (Z–1) produces an atomic K-shell vacancy. If this level decays by proton emission, the X-rays related to the filling process are characteristic for (Z–1) or (Z–2) element, depending on whether the vacancy is filled before or after the proton emission, respectively. For a single proton transition the relative intensity of th...
Aria is a plant hosting a $${350}\,\hbox {m}$$ 350 m cryogenic isotopic distillation column, the ... more Aria is a plant hosting a $${350}\,\hbox {m}$$ 350 m cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of $${^{39}\hbox {Ar}}$$ 39 Ar in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed, $${^{39}\hbox {Ar}}$$ 39 Ar is a $$\beta $$ β -emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.
Proceedings of the 15th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG15), 2020
We have measured two important neutron-induced reactions 7 Be(n, p) 7 Li and 7 Be(n, α) 4 He whic... more We have measured two important neutron-induced reactions 7 Be(n, p) 7 Li and 7 Be(n, α) 4 He which are supposed to reduce the primordial abundance of 7 Li in the Big-Bang nucleosynthesis. We applied the Trojan Horse method by using a 7 Be radioactive isotope beam with the Center-for-Nuclear-Study Radioactive Isotope Beam separator in inverse kinematics. The preliminary excitation functions suggest that the (n, p 0) and the (n, α) channels are basically consistent with the recent experimental studies, and the first-ever data of the (n, p 1) channel may provide a significant extra contribution. We also performed a multi-channel R-matrix analysis to these three channels, confirming the present and the previous data from the point of view of the resonance structure. The result over the thermal neutron energy to the order of mega electron volt enables us to discuss the possible revision of the reaction rate and its impact on the cosmological lithium problem.
Studying interactions of radioactive ions with neutrons is particularly demanding and has been pe... more 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 7 Be destruction induced by the (n, α) reaction is investigated at the energies typical of the primordial nucleosynthesis by means of the Trojan Horse Method applied to the 2 H(7 Be, αα)p quasi-free reaction. The 7 Be(n, α) 4 He 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.
The study of the decay modes competition of the compound systems produced in the collisions 78 Kr... more The study of the decay modes competition of the compound systems produced in the collisions 78 Kr+ 40 Ca and 86 Kr+ 48 Ca at 10AMeV is presented. In particular, the N/Z entrance channel influence on the decay paths of the compound systems, directly connected to the isospin influence, is investigated. The experiment was performed at the INFN Laboratori Nazionali del Sud (LNS) in Catania by using the 4π multi-detector CHIMERA. Charge, mass, angular distributions and kinematical features of the reaction products were studied. The analysis shows some differences in the contribution arising from the various reaction mechanisms for the neutron poor and neutron rich systems. Comparison with theoretical statistical and dynamical models are presented for the two systems. Besides a study of the influence of the energy on the entrance channel is performed for the 78 Kr+ 40 Ca reaction, by comparing the results of this experiment to those obtained for the same system at 5.5 AMeV with the INDRA device at GANIL.
The β decay of 94 Ag, a nucleus with three proton and three neutron holes with respect to 100 Sn,... more The β decay of 94 Ag, a nucleus with three proton and three neutron holes with respect to 100 Sn, was investigated at the GSI on-line mass separator by using an array of germanium and silicon detectors. On the basis of a βγ γ coincidence measurement, the previously reported decay scheme has been considerably improved and evidence is presented for a spin-gap isomer with a spin-parity assignment of (21 +), i.e., the highest spin ever observed in β decay. The half-life of the low-spin isomer (7 +) was remeasured to be 0.59(2) s, whereas the half-life of the high-spin isomer was determined as 0.47(8) s. For the states in 94 Ag and 94 Pd, large-scale shell-model calculations that include up to 4p-4h excitations across the N = Z = 50 shell gap and employ a realistic interaction were carried out. These core excitations play a crucial role in generating the E4 isomerism required for the interpretation of the long half-life of the (21 +) state in 94 Ag.
The excitation of the Dynamical Dipole mode along the fusion path was investigated for the first ... more The excitation of the Dynamical Dipole mode along the fusion path was investigated for the first time in the formation of a heavy compound nucleus in the A∼190 mass region. The compound nucleus was formed at identical conditions of excitation energy and spin from two entrance channels having different charge asymmetry: the charge asymmetric 40 Ca + 152 Sm and the nearly charge symmetric 48 Ca + 144 Sm at E lab =11 and 10.1 MeV/nucleon, respectively. Both fusion-evaporation and fission events were studied simultaneously for the first time. The Dynamical Dipole mode excitation in the charge asymmetric channel was evidenced, in a model-independent way, by comparing the γ-ray multiplicity spectra and angular distributions of the two entrance channels with each other.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2008
A new beam line is now fully operational at Laboratori Nazionali di Legnaro (LNL) TANDEM/ALPI acc... more A new beam line is now fully operational at Laboratori Nazionali di Legnaro (LNL) TANDEM/ALPI accelerator for the in-flight production of light low-energy Radioactive Nuclear Beams (RNBs). The RNBs are produced by inverse kinematics reactions induced by heavy ions, such as 17 O and 6 Li, on 1 H and 3 He gas targets. The beam line has a large solid angle acceptance ðDX ¼ 10 msrÞ and a high rejection capability of spurious beams due to the combined action of magnetic rigidity and velocity filtering. A very pure (100%) and high intensity ð3:6 Â 10 6 ppsÞ 17 F 9þ secondary beam at E lab ¼ 86 AE 1 MeV has been produced and used for experiments. A 8 B 5þ beam at E lab ¼ 33 MeV, with a production rate of $ 2 Â 10 3 pps, is presently under commissioning.
The interaction of loosely bound (S p = 600 keV) 17 F ions with a 208 Pb target was studied at E ... more The interaction of loosely bound (S p = 600 keV) 17 F ions with a 208 Pb target was studied at E lab = 86 MeV, below the Coulomb barrier, by measuring the differential cross-section for the quasielastic scattering and the cross-section for the exclusive breakup process 17 F → 16 O + p. The small reaction and exclusive breakup cross-sections confirm the small reactivity of this system, even at low energy, and indicates that the 17 F small binding energy plays a minor role in the reaction dynamics.
Building on the successful experience in operating the DarkSide-50 detector, the Dark-Side Collab... more Building on the successful experience in operating the DarkSide-50 detector, the Dark-Side Collaboration is going to construct DarkSide-20k, a direct WIMP search detector using a two-phase Liquid Argon Time Projection Chamber (LAr TPC) with an active (fiducial) mass of 23 t (20 t). The DarkSide-20k LAr TPC will be deployed within a shield/veto with a spherical Liquid Scintillator Veto (LSV) inside a cylindrical Water Cherenkov Veto (WCV). Operation of DarkSide-50 demonstrated a major reduction in the dominant 39 Ar background when using argon extracted from an underground source, before applying pulse shape analysis. Data from DarkSide-50, in combination with MC simulation and analytical modeling, shows that a rejection factor for discrimination between electron and nuclear recoils of >3 × 10 9 is achievable. This, along with the use of the veto system, is the key to unlocking the path to large LAr TPC detector masses, while maintaining an "instrumental background-free" experiment, an experiment in which less than <0.1 events (other than ν-induced nuclear recoils) is expected to occur within the WIMP search region during the planned exposure. DarkSide-20k will have ultra-low backgrounds than can be measured in situ. This will give sensitivity to WIMP-nucleon cross sections of 1.2 × 10 −47 cm 2 (1.1 × 10 −46 cm 2) for WIMPs of 1 TeV/c 2 (10 TeV/c 2) mass, to be achieved during a 5 yr run producing an exposure of 100 t yr free from any instrumental background. DarkSide-20k could then extend its operation to a decade, increasing the exposure to 200 t yr, reaching a sensitivity of 7.4 × 10 −48 cm 2 (6.9 × 10 −47 cm 2) for WIMPs of 1 TeV/c 2 (10 TeV/c 2) mass.
Clustering phenomena are well known in nuclear physics for stable nuclei, both αconjugate (N=Z, A... more Clustering phenomena are well known in nuclear physics for stable nuclei, both αconjugate (N=Z, A=2N), like Be, O, Ne, and non-α-conjugate, like Li and Li. In general, it is expected that light exotic nuclei may also exhibit cluster behavior. Moving out of the valley of stability configurations can be found where at least one of the clusters is unbound or weakly bound, thus not satisfying the strong internal correlation requirement of classical clusters. This is so-called exotic clustering. The study of such systems presents many difficulties, due, mainly, to the low intensities typical of radioactive ion beams. Therefore, few significant experimental studies have been performed so far. In this work we searched for α-cluster states in Ne above its α-decay threshold measuring, for the first time, the O(He,He) elastic scattering excitation function. Moreover, this study classified low-energy states in Ne in the astrophysically important region in this HCNO-break-out nucleus.
We propose a study of the B + Pb system at the sub-Coulomb energy of 43 MeV via measurements of t... more We propose a study of the B + Pb system at the sub-Coulomb energy of 43 MeV via measurements of the elastic scattering and Be production cross sections. The main goal of this work is to answer a fundamental question concerning the competition between fusion and direct channels below the barrier for a proton halo nucleus like B incident on a heavy target. It is believed from phenomenological predictions that for weakly bound nuclei incident on heavy targets the direct channels exhaust most of the total reaction cross section for incident energies below the Coulomb barrier, with important consequences for both fusion and various astrophysical problems. In this context the sub-barrier breakup and elastic scattering will be investigated for a global understanding of this issue and the relevant channel coupling effects. In addition the elastic scattering measurement will address another fundamental question: how far does the elastic scattering for proton halo nuclei deviate from Rutherfo...
Finding unambiguous evidence of dark matter interactions in a particle detector is a main objecti... more Finding unambiguous evidence of dark matter interactions in a particle detector is a main objective of physics research. The liquid argon time projection chamber technique for the detection of Weakly Interacting Massive Particles (WIMP) allows sensitivities down to the so-called neutrino floor for high and low WIMP masses. Based on the successful operation of the DarkSide-50 detector, a new and more sensitive experiment, DarkSide-20k, was designed and is now under construction. A thorough understanding of the DarkSide-50 detector response to events classified as dark matter as well as all other interactions is essential for an optimal design of the new experiment. In this paper, we report on a particular set of events, for which scintillation-ionization signals are observed in association with signals from single or few isolated electrons. We identified and provided an interpretation for two event types in which electrons are produced via photoelectric effect on the cathode electrod...
Decay modes of excited compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40... more Decay modes of excited compound systems 118 Ba and 134 Ba, produced respectively in the 78 Kr+ 40 Ca and 86 Kr+ 48 Ca collisions at 10 A•MeV, are investigated. In particular, the competition between the various disintegration path of medium mass compound nuclei, formed by fusion processes, the production of the so referred Intermediate Mass Fragments (IMF), and the isospin dependence of the decay process are studied. Data were taken at the INFN-Laboratori Nazionali del Sud (LNS) by using the CHIMERA array. Data analysis is in progress; a first indication on the average-energy angular distributions suggests pre-equilibrium effects affecting the data and the presence of isotopical effects.
I. Stefan, 8 C. Stodel, 3 Ch. Theisen, 9 D. Verney, 3 and J.Żylicz IEP, Warsaw University, Ho ża ... more I. Stefan, 8 C. Stodel, 3 Ch. Theisen, 9 D. Verney, 3 and J.Żylicz IEP, Warsaw University, Ho ża 69, PL-00-681 Warszawa, Poland Oak Ridge National Laboratory, Physics Division, Oak Ridge, Tennessee 37831, USA GANIL, Boite Postale 55027, F-14076 Caen Cedex 5, France Gesellschaft für Schwerionenforschung mbH, D-64291 Darmstadt, Germany CEA Bruyéres-le-Châtel DIF/DPTA/SPN, Boite Postale 12, F-91680 Bruyères-le-Châtel, France St. Kliment Ohridski University of Sofia, BG-1164 Sofia, Bulgaria Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA IFIN, P.O. Box MG6, 76900 Bucharest-Magurele, Romania CEA Saclay, DSM/DAPNIA/SPhN, F-91191 Gif sur Yvette Cedex, France Department of Physics, University of Naples “Federico II,” I-80126 Naples, Italy CENBG, Boite Postale 120, F-33175 Gradignan Cedex, France IPN, 91406 Orsay Cedex, France Department of Particle Physics, The Weizmann Institute of Science, 76100 Rehovot, Israel Department of Radiation Sciences...
It has been demonstrated that the particle X-ray coincidence technique (PXCT) [1] can be used to ... more It has been demonstrated that the particle X-ray coincidence technique (PXCT) [1] can be used to get information on lifetimes of excited nuclear states in the time range of 10−15–10−17 s, such data being difficult to access by other methods. The PXCT technique uses an ”atomic clock” (filling of the atomic shell vacancy) to measure the time scale of the nuclear deexcitation process. The βdelayed proton emission following electron capture decay (ECp) is ideally suited for this type of measurements. In this case the PXCT method is based on the following principle: A nucleus (with atomic number Z) decaying, e.g., by K-electron capture to excited state in the daughter (Z–1) produces an atomic K-shell vacancy. If this level decays by proton emission, the X-rays related to the filling process are characteristic for (Z–1) or (Z–2) element, depending on whether the vacancy is filled before or after the proton emission, respectively. For a single proton transition the relative intensity of th...
Aria is a plant hosting a $${350}\,\hbox {m}$$ 350 m cryogenic isotopic distillation column, the ... more Aria is a plant hosting a $${350}\,\hbox {m}$$ 350 m cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of $${^{39}\hbox {Ar}}$$ 39 Ar in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed, $${^{39}\hbox {Ar}}$$ 39 Ar is a $$\beta $$ β -emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.
Proceedings of the 15th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG15), 2020
We have measured two important neutron-induced reactions 7 Be(n, p) 7 Li and 7 Be(n, α) 4 He whic... more We have measured two important neutron-induced reactions 7 Be(n, p) 7 Li and 7 Be(n, α) 4 He which are supposed to reduce the primordial abundance of 7 Li in the Big-Bang nucleosynthesis. We applied the Trojan Horse method by using a 7 Be radioactive isotope beam with the Center-for-Nuclear-Study Radioactive Isotope Beam separator in inverse kinematics. The preliminary excitation functions suggest that the (n, p 0) and the (n, α) channels are basically consistent with the recent experimental studies, and the first-ever data of the (n, p 1) channel may provide a significant extra contribution. We also performed a multi-channel R-matrix analysis to these three channels, confirming the present and the previous data from the point of view of the resonance structure. The result over the thermal neutron energy to the order of mega electron volt enables us to discuss the possible revision of the reaction rate and its impact on the cosmological lithium problem.
Studying interactions of radioactive ions with neutrons is particularly demanding and has been pe... more 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 7 Be destruction induced by the (n, α) reaction is investigated at the energies typical of the primordial nucleosynthesis by means of the Trojan Horse Method applied to the 2 H(7 Be, αα)p quasi-free reaction. The 7 Be(n, α) 4 He 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.
The study of the decay modes competition of the compound systems produced in the collisions 78 Kr... more The study of the decay modes competition of the compound systems produced in the collisions 78 Kr+ 40 Ca and 86 Kr+ 48 Ca at 10AMeV is presented. In particular, the N/Z entrance channel influence on the decay paths of the compound systems, directly connected to the isospin influence, is investigated. The experiment was performed at the INFN Laboratori Nazionali del Sud (LNS) in Catania by using the 4π multi-detector CHIMERA. Charge, mass, angular distributions and kinematical features of the reaction products were studied. The analysis shows some differences in the contribution arising from the various reaction mechanisms for the neutron poor and neutron rich systems. Comparison with theoretical statistical and dynamical models are presented for the two systems. Besides a study of the influence of the energy on the entrance channel is performed for the 78 Kr+ 40 Ca reaction, by comparing the results of this experiment to those obtained for the same system at 5.5 AMeV with the INDRA device at GANIL.
The β decay of 94 Ag, a nucleus with three proton and three neutron holes with respect to 100 Sn,... more The β decay of 94 Ag, a nucleus with three proton and three neutron holes with respect to 100 Sn, was investigated at the GSI on-line mass separator by using an array of germanium and silicon detectors. On the basis of a βγ γ coincidence measurement, the previously reported decay scheme has been considerably improved and evidence is presented for a spin-gap isomer with a spin-parity assignment of (21 +), i.e., the highest spin ever observed in β decay. The half-life of the low-spin isomer (7 +) was remeasured to be 0.59(2) s, whereas the half-life of the high-spin isomer was determined as 0.47(8) s. For the states in 94 Ag and 94 Pd, large-scale shell-model calculations that include up to 4p-4h excitations across the N = Z = 50 shell gap and employ a realistic interaction were carried out. These core excitations play a crucial role in generating the E4 isomerism required for the interpretation of the long half-life of the (21 +) state in 94 Ag.
The excitation of the Dynamical Dipole mode along the fusion path was investigated for the first ... more The excitation of the Dynamical Dipole mode along the fusion path was investigated for the first time in the formation of a heavy compound nucleus in the A∼190 mass region. The compound nucleus was formed at identical conditions of excitation energy and spin from two entrance channels having different charge asymmetry: the charge asymmetric 40 Ca + 152 Sm and the nearly charge symmetric 48 Ca + 144 Sm at E lab =11 and 10.1 MeV/nucleon, respectively. Both fusion-evaporation and fission events were studied simultaneously for the first time. The Dynamical Dipole mode excitation in the charge asymmetric channel was evidenced, in a model-independent way, by comparing the γ-ray multiplicity spectra and angular distributions of the two entrance channels with each other.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2008
A new beam line is now fully operational at Laboratori Nazionali di Legnaro (LNL) TANDEM/ALPI acc... more A new beam line is now fully operational at Laboratori Nazionali di Legnaro (LNL) TANDEM/ALPI accelerator for the in-flight production of light low-energy Radioactive Nuclear Beams (RNBs). The RNBs are produced by inverse kinematics reactions induced by heavy ions, such as 17 O and 6 Li, on 1 H and 3 He gas targets. The beam line has a large solid angle acceptance ðDX ¼ 10 msrÞ and a high rejection capability of spurious beams due to the combined action of magnetic rigidity and velocity filtering. A very pure (100%) and high intensity ð3:6 Â 10 6 ppsÞ 17 F 9þ secondary beam at E lab ¼ 86 AE 1 MeV has been produced and used for experiments. A 8 B 5þ beam at E lab ¼ 33 MeV, with a production rate of $ 2 Â 10 3 pps, is presently under commissioning.
The interaction of loosely bound (S p = 600 keV) 17 F ions with a 208 Pb target was studied at E ... more The interaction of loosely bound (S p = 600 keV) 17 F ions with a 208 Pb target was studied at E lab = 86 MeV, below the Coulomb barrier, by measuring the differential cross-section for the quasielastic scattering and the cross-section for the exclusive breakup process 17 F → 16 O + p. The small reaction and exclusive breakup cross-sections confirm the small reactivity of this system, even at low energy, and indicates that the 17 F small binding energy plays a minor role in the reaction dynamics.
Building on the successful experience in operating the DarkSide-50 detector, the Dark-Side Collab... more Building on the successful experience in operating the DarkSide-50 detector, the Dark-Side Collaboration is going to construct DarkSide-20k, a direct WIMP search detector using a two-phase Liquid Argon Time Projection Chamber (LAr TPC) with an active (fiducial) mass of 23 t (20 t). The DarkSide-20k LAr TPC will be deployed within a shield/veto with a spherical Liquid Scintillator Veto (LSV) inside a cylindrical Water Cherenkov Veto (WCV). Operation of DarkSide-50 demonstrated a major reduction in the dominant 39 Ar background when using argon extracted from an underground source, before applying pulse shape analysis. Data from DarkSide-50, in combination with MC simulation and analytical modeling, shows that a rejection factor for discrimination between electron and nuclear recoils of >3 × 10 9 is achievable. This, along with the use of the veto system, is the key to unlocking the path to large LAr TPC detector masses, while maintaining an "instrumental background-free" experiment, an experiment in which less than <0.1 events (other than ν-induced nuclear recoils) is expected to occur within the WIMP search region during the planned exposure. DarkSide-20k will have ultra-low backgrounds than can be measured in situ. This will give sensitivity to WIMP-nucleon cross sections of 1.2 × 10 −47 cm 2 (1.1 × 10 −46 cm 2) for WIMPs of 1 TeV/c 2 (10 TeV/c 2) mass, to be achieved during a 5 yr run producing an exposure of 100 t yr free from any instrumental background. DarkSide-20k could then extend its operation to a decade, increasing the exposure to 200 t yr, reaching a sensitivity of 7.4 × 10 −48 cm 2 (6.9 × 10 −47 cm 2) for WIMPs of 1 TeV/c 2 (10 TeV/c 2) mass.
Clustering phenomena are well known in nuclear physics for stable nuclei, both αconjugate (N=Z, A... more Clustering phenomena are well known in nuclear physics for stable nuclei, both αconjugate (N=Z, A=2N), like Be, O, Ne, and non-α-conjugate, like Li and Li. In general, it is expected that light exotic nuclei may also exhibit cluster behavior. Moving out of the valley of stability configurations can be found where at least one of the clusters is unbound or weakly bound, thus not satisfying the strong internal correlation requirement of classical clusters. This is so-called exotic clustering. The study of such systems presents many difficulties, due, mainly, to the low intensities typical of radioactive ion beams. Therefore, few significant experimental studies have been performed so far. In this work we searched for α-cluster states in Ne above its α-decay threshold measuring, for the first time, the O(He,He) elastic scattering excitation function. Moreover, this study classified low-energy states in Ne in the astrophysically important region in this HCNO-break-out nucleus.
We propose a study of the B + Pb system at the sub-Coulomb energy of 43 MeV via measurements of t... more We propose a study of the B + Pb system at the sub-Coulomb energy of 43 MeV via measurements of the elastic scattering and Be production cross sections. The main goal of this work is to answer a fundamental question concerning the competition between fusion and direct channels below the barrier for a proton halo nucleus like B incident on a heavy target. It is believed from phenomenological predictions that for weakly bound nuclei incident on heavy targets the direct channels exhaust most of the total reaction cross section for incident energies below the Coulomb barrier, with important consequences for both fusion and various astrophysical problems. In this context the sub-barrier breakup and elastic scattering will be investigated for a global understanding of this issue and the relevant channel coupling effects. In addition the elastic scattering measurement will address another fundamental question: how far does the elastic scattering for proton halo nuclei deviate from Rutherfo...
Finding unambiguous evidence of dark matter interactions in a particle detector is a main objecti... more Finding unambiguous evidence of dark matter interactions in a particle detector is a main objective of physics research. The liquid argon time projection chamber technique for the detection of Weakly Interacting Massive Particles (WIMP) allows sensitivities down to the so-called neutrino floor for high and low WIMP masses. Based on the successful operation of the DarkSide-50 detector, a new and more sensitive experiment, DarkSide-20k, was designed and is now under construction. A thorough understanding of the DarkSide-50 detector response to events classified as dark matter as well as all other interactions is essential for an optimal design of the new experiment. In this paper, we report on a particular set of events, for which scintillation-ionization signals are observed in association with signals from single or few isolated electrons. We identified and provided an interpretation for two event types in which electrons are produced via photoelectric effect on the cathode electrod...
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Papers by M. La Commara