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Exploring the keV-scale physics potential of CUORE

CUORE Collaboration, D. Q. Adams, C. Alduino, K. Alfonso, A. Armatol, F. T. Avignone, O. Azzolini, G. Bari, F. Bellini, G. Benato, M. Beretta, M. Biassoni, A. Branca, C. Brofferio, C. Bucci, J. Camilleri, A. Caminata, A. Campani, J. Cao, C. Capelli, S. Capelli, L. Cappelli, L. Cardani, P. Carniti, N. Casali, E. Celi, D. Chiesa, M. Clemenza, S. Copello, A. Cosoli, O. Cremonesi, R. J. Creswick, A. DAddabbo, I. Dafinei, S. DellOro, S. Di Domizio, S. Di Lorenzo, T. Dixon, D. Q. Fang, M. Faverzani, E. Ferri, F. Ferroni, E. Fiorini, M. A. Franceschi, S. J. Freedman, S. H. Fu, B. K. Fujikawa, S. Ghislandi, A. Giachero, M. Girola, L. Gironi, A. Giuliani, P. Gorla, C. Gotti, P. V. Guillaumon, T. D. Gutierrez, K. Han, E. V. Hansen, K. M. Heeger, D. L. Helis, H. Z. Huang, M. T. Hurst, G. Keppel, Yu. G. Kolomensky, R. Kowalski, R. Liu, L. Ma, Y. G. Ma, L. Marini, R. H. Maruyama, D. Mayer, Y. Mei, M. N. Moore, T. Napolitano, M. Nastasi, C. Nones, E. B. Norman, A. Nucciotti, I. Nutini, T. ODonnell, M. Olmi, B. T. Oregui, S. Pagan, C. E. Pagliarone, L. Pagnanini, M. Pallavicini, L. Pattavina, M. Pavan, G. Pessina, V. Pettinacci, C. Pira, S. Pirro, E. G. Pottebaum, S. Pozzi, E. Previtali, A. Puiu, S. Quitadamo, A. Ressa, C. Rosenfeld, B. Schmidt, R. Serino, A. Shaikina, V. Sharma, V. Singh, M. Sisti, D. Speller, P. T. Surukuchi, L. Taffarello, C. Tomei, A. Torres, J. A. Torres, K. J. Vetter, M. Vignati, S. L. Wagaarachchi, R. Wang, B. Welliver, J. Wilson, K. Wilson, L. A. Winslow, F. Xie, T. Zhu, S. Zimmermann, S. Zucchelli

TL;DR

CUORE demonstrates keV-scale physics potential by developing dedicated low-energy analysis techniques for a large-scale cryogenic calorimeter array. Through offline triggering, detector-by-detector spurious-event rejection, and robust near-threshold calibrations, the study achieves thresholds down to $3$ keV with substantial background suppression and quantified reconstruction efficiencies of $26\%$ at $3$ keV and $50\%$ at $10$ keV. The resulting exposure- and detector-dependent spectra reveal key low-energy features and are coupled with a data-driven background model to enable future keV-scale searches, including axions and WIMP scenarios. These results validate the scalability of tonne-scale cryogenic calorimeters for broad energy-range physics and guide the design and operation of next-generation detectors like CUPID.

Abstract

We present the analysis techniques developed to explore the keV-scale energy region of the CUORE experiment, based on more than 2 tonne yr of data collected over 5 years. By prioritizing a stricter selection over a larger exposure, we are able to optimize data selection for thresholds at 10 keV and 3 keV with 691 kg yr and 11 kg yr of data, respectively. We study how the performance varies among the 988-detector array with different detector characteristics and data taking conditions. We achieve an average baseline resolution of 2.54 $\pm$ 0.14 keV FWHM and 1.18 $\pm$ 0.02 keV FWHM for the data selection at 10 keV and 3 keV, respectively. The analysis methods employed reduce the overall background by about an order of magnitude, reaching 2.06 $\pm$ 0.05 counts/(keV kg days) and 16 $\pm$ 2 counts/(keV kg days) at the thresholds of 10 keV and 3 keV. We evaluate for the first time the near-threshold reconstruction efficiencies of the CUORE experiment, and find these to be 26 $\pm$ 4 \% and 50 $\pm$ 2 \% at 3 keV and 10 keV, respectively. This analysis provides crucial insights into rare decay studies, new physics searches, and keV-scale background modeling with CUORE. We demonstrate that tonne-scale cryogenic calorimeters can operate across a wide energy range, from keV to MeV, establishing their scalability as versatile detectors for rare event and dark matter physics. These findings also inform the optimization of future large mass cryogenic calorimeters to enhance the sensitivity to low-energy phenomena.

Exploring the keV-scale physics potential of CUORE

TL;DR

CUORE demonstrates keV-scale physics potential by developing dedicated low-energy analysis techniques for a large-scale cryogenic calorimeter array. Through offline triggering, detector-by-detector spurious-event rejection, and robust near-threshold calibrations, the study achieves thresholds down to keV with substantial background suppression and quantified reconstruction efficiencies of at keV and at keV. The resulting exposure- and detector-dependent spectra reveal key low-energy features and are coupled with a data-driven background model to enable future keV-scale searches, including axions and WIMP scenarios. These results validate the scalability of tonne-scale cryogenic calorimeters for broad energy-range physics and guide the design and operation of next-generation detectors like CUPID.

Abstract

We present the analysis techniques developed to explore the keV-scale energy region of the CUORE experiment, based on more than 2 tonne yr of data collected over 5 years. By prioritizing a stricter selection over a larger exposure, we are able to optimize data selection for thresholds at 10 keV and 3 keV with 691 kg yr and 11 kg yr of data, respectively. We study how the performance varies among the 988-detector array with different detector characteristics and data taking conditions. We achieve an average baseline resolution of 2.54 0.14 keV FWHM and 1.18 0.02 keV FWHM for the data selection at 10 keV and 3 keV, respectively. The analysis methods employed reduce the overall background by about an order of magnitude, reaching 2.06 0.05 counts/(keV kg days) and 16 2 counts/(keV kg days) at the thresholds of 10 keV and 3 keV. We evaluate for the first time the near-threshold reconstruction efficiencies of the CUORE experiment, and find these to be 26 4 \% and 50 2 \% at 3 keV and 10 keV, respectively. This analysis provides crucial insights into rare decay studies, new physics searches, and keV-scale background modeling with CUORE. We demonstrate that tonne-scale cryogenic calorimeters can operate across a wide energy range, from keV to MeV, establishing their scalability as versatile detectors for rare event and dark matter physics. These findings also inform the optimization of future large mass cryogenic calorimeters to enhance the sensitivity to low-energy phenomena.

Paper Structure

This paper contains 11 sections, 14 figures, 2 tables.

Table of Contents

  1. Introduction
  2. The CUORE Experiment
  3. Data Analysis
  4. Validation data and energy scale calibration
  5. Optimum Trigger
  6. Tagging of multi-site events
  7. Spurious events discrimination
  8. Data Selection Results
  9. Efficiencies
  10. Low Energy Spectra
  11. Conclusion and Outlook

Figures (14)

  • Figure 1: A sample of pulses from the same detector and operating conditions with different energies, decreasing from $\sim$2.5 MeV, in the energy region of interest for the 0$\nu\beta\beta$, to $\sim$5 keV, near CUORE threshold. The amplitude and the offset are normalized to be the same for all the pulses.
  • Figure 2: Data and model of Te X-rays peaks in a 20 keV width window. The events here reported belong to a sample calibration dataset of CUORE and they are selected to have multiplicity equal to 2 in order to enhance the signal-to-background ratio. The model consists of two Gaussian functions and a linear background. The fit to data resulted into a $\chi^2/\nu$ = 101/93, where $\nu$ is the number of degrees of freedom. The result in all of the other datasets is consistent with the example reported here.
  • Figure 3: The histogram shows the distribution of low energy events coincident with the 1460 keV line from $^{40}$K line. The peak of the distribution coincide with the expected energy of the X-ray from the $^{40}$K electron capture. The total energy range of search extends up to 40 keV, and presents two more events not shown here for illustrative purposes.
  • Figure 4: Distribution of the trigger thresholds namely, the energy at which trigger efficiency is 90%, for the detector-dataset pairs used in the 2 tonne yr low energy dataset. The different colors highlight the pairs belonging to different data taking conditions, i.e. operation temperature at 12 or 15 mK, and employing an optimal vibration damping system configuration. Any distribution refers to all the operated CUORE detectors, but to a different number of datasets, depending on the experimental conditions.
  • Figure 5: Example of $\chi^2_{OF}$ (Pulse Shape Parameter) as a function of the energy for a single detector, with a $\sim$2 keV trigger threshold, and dataset. We show two pulses having similar energy ($\sim$15 keV), but different $\chi^2_{OF}$. The left pulse belongs to the spurious events band, while the right one to the signal band.
  • ...and 9 more figures