The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.

https://hal.archives-ouvertes.fr/hal-01806968/document

The NUMEN project: NUclear Matrix Elements for Neutrinoless double beta decay

A new and innovative array, MUST, based on silicon strip technology and dedicated to the study of reactions induced by radioactive beams on light particles is described. The detector consists of 8 silicon strip – Si(Li) telescopes used to identify recoiling light charged particles through time of flight, energy loss and energy measurements and to determine precisely their scattering angle through X, Y position measurements. Each 60×60 mm 2 double sided silicon strip detector with 60 vertical and 60 horizontal strips yields an X – Y position resolution of 1 mm, an energy resolution of 50 keV, a time resolution of around 1 ns and a 500 keV energy threshold for protons. The backing Si(Li) detectors stop protons up to 25 MeV with a resolution of approximately 50 keV. CsI crystals read out by photo-diodes which stop protons up to 70 MeV are added to the telescopes for applications where higher energy particles need to be detected. The dedicated electronics in VXIbus standard allow us to house the 968 logic and analog channels of the array in one crate placed adjacent to the reaction chamber and fully remote controlled, including pulse visualization on oscilloscopes. A stand alone data acquisition system devoted to the MUST array has been developed. Isotope identification of light charged particles over the full energy range has been achieved, and the capability of the system to measure angular distributions of states populated in inverse kinematics reactions has been demonstrated.

Must: a silicon strip detector array for radioactive beam experiments

Experimental data obtained with the 4{pi} multidetector system INDRA are used to study the light charged particle (LCP, Z{le}2) and intermediate mass fragment (IMF, Z{ge}3) production in peripheral and semicentral collisions of Xe and Sn at 50 MeV/nucleon. It is found that a sizable fraction of the detected LCP`s and IMF`s originates from the midvelocity region. These fragments can be seen to come either from a prompt (preequilibrium) mechanism or from a slower but dynamically influenced emission process. The relative magnitude of the dynamically influenced emission relative to the isotropic statistical evaporation is presented as a function of the transverse energy of light particles, used as an impact parameter selector. The results are compared to dynamical models with which a good agreement is obtained. {copyright} {ital 1997} {ital The American Physical Society}

Dynamical effects and intermediate mass fragment production in peripheral and semicentral collisions of Xe+Sn at 50 MeV/nucleon

Excitation functions of flow and stopping observables for the Au+Au system at energies from 40 to 1500 MeV per nucleon are presented. The systematics were obtained by merging the results of the INDRA and FOPI experiments, both performed at the GSI facility. The connection to the nuclear equation of state is discussed.

/pdf/systematics-of-stopping-and-flow-in-au-au-collisions-555sj5e0yp.pdf

Systematics of stopping and flow in Au+Au collisions

A hot expanding source in 50 A MeV Xe + Sn central reactions

INDRA, a new and innovative highly segmented detector for light charged particles and fragments is described. It covers geometrically 90% of the 4π solid angle and has very low detection thresholds. The detector, operated under vacuum, is axially symmetric and segmented in 336 independent cells allowing efficient detection of high multiplicity events. Nucleus identification down to very low energy threshold (≈ 1 A MeV) is achieved by using ionization chambers operated with low pressure C 3 F 8 gas. Residual energies are measured by a combination of silicon (300 μm thick) and cesium iodide (5 to 14 cm in length) detectors. Very forward angles are covered by fast counting phoswich scintillators (NE102/NE115). Charge resolution up to Z = 50 is achieved on a large energy dynamic range (5000 to 1 for silicon detectors). Isotopic separation is obtained up to Z = 3. The treatment of the signals is performed through specifically designed and highly integrated modules, most of which are in the new VXIbus standard. Full remote control of parameter settings, including visualization of signals, is thus allowed. The detector is continuously monitored with a laser source and electronic pulsers and is found stable over several days. Energy calibration procedures, making use of specific detectors and the ability of the GANIL accelerator to deliver secondary beams, have been developed. First experiments were performed in the spring of 1993.

INDRA, a 4π charged product detection array at GANIL

https://cds.cern.ch/record/271733/files/SCAN-9411211.pdf

C. Spitaels

Papers

INDRA, a 4π charged product detection array at GANIL

INDRA : a $4\pi$ charged product detection array at GANIL