[Paper Review] CUPID pre-CDR

The CUPID Interest Group|arXiv (Cornell University)|Jul 22, 2019

Medical Imaging and Pathology StudiesMedicine33 citations

TL;DR

This document outlines CUPID, a next-generation bolometric search for neutrinoless double beta decay, built on CUORE infrastructure and using Li2MoO4 crystals enriched in 100Mo to achieve background suppression and high sensitivity.

ABSTRACT

CUPID is a proposed future tonne-scale bolometric neutrinoless double beta decay ($0νββ$) experiment to probe the Majorana nature of neutrinos and discover Lepton Number Violation in the so-called inverted hierarchy region of the neutrino mass. CUPID will be built on experience, expertise and lessons learned in CUORE, and will exploit the current CUORE infrastructure as much as possible. In order to achieve its ambitious science goals, CUPID aims to dramatically reduce the backgrounds in the region of interest introducing a high efficiently $α$/$β$ discrimination techniques, also demonstrated by the CUPID-0 and CUPID-Mo experiments, and using a high transition energy double beta decay nucleus, $^{100}$Mo. This document describe the main concepts related with the design of the CUPID experiment and indicates the projected sensitivities and the global scientific goal of the experiment.

Motivation & Objective

• Motivate the search for lepton-number violation via 0νββ decay and its implications for Majorana neutrinos and beyond-Standard-Model physics.
• Present the CUPID baseline design that leverages CUORE infrastructure to reach substantially lower backgrounds and higher discovery potential.
• Propose a scalable, multi-isotope bolometric approach enabling high energy resolution, strong alpha background rejection, and phased deployment.
• Evaluate the feasibility of deploying a ton-scale, 100Mo-enriched CUPID detector within the existing cryogenic infrastructure.
• Outline the expected physics reach, deployment timeline, and key technical upgrades required for CUPID success.

Proposed method

• Adopt scintillating bolometers with Li2MoO4 crystals enriched in 100Mo to enable simultaneous heat and light readout for alpha discrimination.
• Use Neutron Transmutation Doped (NTD) Ge thermistors as thermal sensors coupled to each crystal and light detector.
• Employ the CUORE cryostat and infrastructure with upgrades for low vibration and low radioactivity environments.
• Design a 1-ton scale prototype and a staged deployment plan to achieve a background index around 1e-4 counts/(keV·kg·yr).
• Structure the detector as tiled towers within the existing CUORE cryogenic system to minimize changes to the overall setup.
• Maintain the option to study alternative isotopes/crystal options (e.g., TeO2) for multi-isotope capability.

Experimental results

Research questions

• RQ1 What sensitivity to the effective Majorana mass mββ can CUPID achieve with ~10 years of operation in the baseline Li2MoO4(100Mo) configuration?
• RQ2 Can alpha background be effectively suppressed to reach a background index of ~1e-4 counts/(keV·kg·yr) in the 100Mo ROI?
• RQ3 Is a ton-scale CUPID detector feasible within the existing CUORE cryostat and infrastructure, and what upgrades are required?
• RQ4 How does the multi-isotope bolometric approach compare in discovery potential and practicality to alternative next-generation 0νββ projects?
• RQ5 What are the projected timelines and milestones to move from CUORE operations to a full CUPID deployment?

Key findings

• Baseline CUPID design uses Li2Mo100MoO4 crystals with ~308 g mass each, totaling ~253 kg of 100Mo and 1534 crystals.
• Projected energy resolution is ~5 keV FWHM at 2615 keV with ~79% containment efficiency and ~90% selection efficiency.
• Expected background index is ~1e-4 counts/(keV·kg·yr) in the 100Mo region of interest.
• Reachable 0νββ half-life sensitivity at 90% CL is 1.5e27 years, and discovery sensitivity at 3σ is 1.1e27 years for 10 years of livetime.
• In mββ terms, CUPID aims for a 90% CL limit of 10–17 meV and a 3σ discovery sensitivity of 12–20 meV.
• Demonstrators CUPID-0 and CUPID-Mo show 5 keV resolution, 99.9% α rejection with full β/γ acceptance, and internal radiopurity at or below 5 μBq/kg for 232Th/238U.