The NUMEN Heavy Ion Multidetector for a Complementary Approach to the Neutrinoless Double Beta Decay

Abstract

Neutrinos are so far the most elusive known particles, and in the last decades many sophisticated experiments have been set up in order to clarify several questions about their intrinsic nature, in particular their masses, mass hierarchy, intrinsic nature of Majorana or Dirac particles. Evidence of the Neutrinoless Double-Beta Decay (NDBD) would prove that neutrinos are Majorana particles, thus improving the understanding of the universe itself. Besides the search for several large underground experiments for the direct experimental detection of NDBD, the NUMEN experiment proposes the investigation of a nuclear mechanism strongly linked to this decay: the Double Charge Exchange reactions (DCE). As such reactions share with the NDBD the same initial and final nuclear states, they could shed light on the determination of the Nuclear Matrix Elements (NMEs), which play a relevant role in the decay. The physics of DCE is described elsewhere in this issue, while the focus of this paper will be on the challenging experimental apparatus currently under construction in order to fulfil the requirements of the NUMEN experiment. The overall structure of the technological improvement to the cyclotron, along with the newly developed detection systems required for tracking and identifying the reaction products and their final excitation level are described.

The NUMEN Project: An Update of the Facility Toward the Future Experimental Campaigns

“…1429) are positioned on the top of these supporting flanges, outside the vacuum region. Long coaxial cables connect the front-end electronics to the read-out based on CAEN VX2740 multichannel digitizers (Finocchiaro et al, 2020). For the maintenance, each flange with pre-amplifiers circuits and suspended detectors will be hooked and lifted by a dedicated lifting system, positioned on board of the MAGNEX platform, in order to be placed on a stand near the spectrometer.…”

“…The working principles of the adopted solution and first results from a reduced size prototype of the tracker can be found in Finocchiaro et al (2020). As the focus of the present article is on recent advancements, two aspects need to be specifically considered.…”

“…The SiC detector is 100 µm thick and measures E. The CsI(Tl) inorganic scintillator is 5 mm thick and is coupled to a Hamamatsu S3590 photodiode of 1 × 1 cm area to measure E r . The capabilities of the system in terms of radiation hardness and mass resolution are discussed in Finocchiaro et al (2020). A new mechanical arrangement of the telescopes is presented here, as a result of optimization of the detection efficiency and the mechanical integration.…”

“…A new mechanical arrangement of the telescopes is presented here, as a result of optimization of the detection efficiency and the mechanical integration. Indeed, in the configuration shown in Finocchiaro et al (2020), the central region of the vertical coordinate (Y foc ∼0) was not covered as it corresponded to the dead region between two vertical modules. This would have determined a relevant efficiency loss, since close to the MAGNEX symmetry plane (Y foc ∼ 0) the ion rate is maximum (see for e.g., Cappuzzello et al, 2014;Carbone, 2015).…”

“…Part of the plans and activities in view of the upgrade of the experimental facility is described in Cappuzzello et al (2018), Finocchiaro et al (2020, Agodi et al (2021), while recent experimental results from NUMEN are cited in Section Experimental activity with accelerated beams during numen phase 2. In this manuscript an update of the NUMEN R&D activity is given, with special emphasis on recent advances on technical aspects not presented elsewhere.…”