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arxiv: 2605.22479 · v2 · pith:4U22X7GBnew · submitted 2026-05-21 · ⚛️ physics.ins-det

Energy Calibration and Performance of HPGe Detectors in the LEGEND-200 Experiment

The LEGEND Collaboration , H. Acharya , M. Agostini , A. Alexander , C. Alvarez-Garcia , V. Aures , F.T. Avignone III , M. Babicz
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W. Bae M. Balata A.S. Barabash P.S. Barbeau C.J. Barton L. Baudis C. Bauer S. Bellman E. Bernieri J.P. Ulloa Beteta L. Bezrukov K.H. Bhimani V. Biancacci A. Biondi R. Biondi E. Blalock P. Bongratz S.J. Borden G. Borghi F. Borra B. Bos A. Boston G. Botogoske R. Bouabid R. Brugnera T. B\"urger N. Burlac M. Busch S. Calgaro N. Canci L. Canonica S. Capra M. Carminati R.M.D. Carney L. Carroll C. Cattadori R. Cesarano Y.-D. Chan J.R. Chapman A. Chernogorov P.-J. Chiu O. Chkvorets C.D. Christofferson A.I. Colon-Rivera F. Confortini D. D'Agostino V. D'Andrea G. De Gregorio R. Deckert J.A. Detwiler N. Di Marco F. Di Capua C. Di Fraia A. Di Giacinto D. Di Leo T. Dixon K.-M. Dong A. Drobizhev G. Duran Yu. Efremenko S.R. Elliott T. Elmikawy C.H.J. Emmanuel E. Engelhardt E. Esch L. Favilla M. Febbraro F. Ferella R. Feriozzi D.E. Fields C. Fiorini M. Fomina N. Fuad R. Gala A. Galindo-Uribarri A. Gangapshev A. Garfagnini S. Gazzana A. Geraci L. Gessler C. Ghiano A. Gieb S. Giri A. Gogosha M. Gold M.P. Green G. Gr\"unauer J. Gruszko I. Guinn V.E. Guiseppe Y. Gurov K. Gusev B. Hackett F. Hagemann M. Haranczyk F. Henkes R. Henning J. Herrera D. Hervas Aguilar J. Hinton R. Hod\'ak H.F.R. Hoffmann M. Huber M. Hult A. Iorio U.T. Islek A. Jany J. Jochum D.S. Judson M. Junker J. Kaizer V. Kazalov M.F. Kidd T. Kihm K. Kilgus A. Klimenko K.T. Kn\"opfle I. Kochanek O. Kochetov I. Kontul V.N. Kornoukhov A.B. Kowaleswska P. Krause H. Krishnamoorthy V.V. Kuzminov K. Lang M. Laubenstein N.N.P.N. Lay A. Leder B. Lehnert A. Leonhardt N. Levashko A. Li L.Y. Li Y.-R. Lin I. Lippi A. Love A. Lubashevskiy B. Lubsandorzhiev N. Lusardi B. Majorovits F. Mamedov G.G. Marshall E.L. Martin R.D. Martin R. Massarczyk A. Mazumdar G. McDowell D.-M. Mei M. Menzel S. Mertens E. Miller I. Mirza M. Misiaszek M. Morella B. Morgan D. Muenstermann C.J. Nave M. Neuberger N. O'Briant F. Paissan L. Papp K. Pelczar L. Pertoldi W. Pettus F. Piastra M. Pichotta P. Piseri A.W.P. Poon P.P. Povinec A. Pullia W.S. Quinn D.C. Radford Y.A. Ramachers A.L. Reine S. Riboldi E. Richards K. Rielage C. Romo-Luque B. Rossi N. Rossi S. Rozov N. Rumyantseva R. Saakyan S. Sailer G. Salamanna F. Salamida G. Saleh E. Sanchez Garcia C. Savarese D.C. Schaper J. Schlegel S.J. Schleich L. Schl\"uter S. Sch\"onert O. Schulz A.-K. Sch\"utz M. Schwarz M. Schweizer B. Schwingenheuer C. Seibt G. Senatore A. Serafini K. Shakhov E. Shevchik H. Shi M. Shirchenko Y. Shitov N. Sierig H. Simgen F. \v{S}imkovic S. Simonaitis-Boyd M. Singh M. Skorokhvatov M. Slav\'i\v{c}kov\'a J.A. Solomon G. Song A.C. Sousa A.R. Sreekala L. Steinhart I. \v{S}tekl T. Sterr M. Stommel R. Stroili S.A. Sullivan R.R. Sumathi K. Szczepaniec L. Taffarello D. Tagnani V. Tretyak M. Turqueti E.E. van Nieuwenhuizen L.J. Varriano S. Vasilyev V. Vatsa C. Vignoli C. Vogl I. Wang A. Warren J.N. Warren D. Waters S.L. Watkins C. Wiesinger J.F. Wilkerson M. Willers M. Wojcik D. Xu E. Yakushev T. Ye C.-H. Yu V. Yumatov D. Zinatulina K. Zuber G. Zuzel
This is my paper

Pith reviewed 2026-05-25 05:31 UTC · model grok-4.3

classification ⚛️ physics.ins-det
keywords energy calibrationHPGe detectorsLEGEND-200neutrinoless double beta decayenergy resolution228Th calibrationpeak shape modeling
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The pith

LEGEND-200 HPGe detectors deliver 2.47 keV average resolution at 2039 keV with peak positions stable to 0.05 keV weekly.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper details the digital signal processing, peak modeling, and calibration methods used for high-purity germanium detectors in the LEGEND-200 neutrinoless double beta decay search. Weekly runs with a thorium-228 source establish the energy scale, and after applying systematic corrections for non-linearities, the combined resolution reaches 2.47 keV at the Q-value of interest. Peak positions remain stable across detectors and over time, with variations kept below 0.05 keV up to 2614 keV. These procedures directly support the first unblinding of the experiment by minimizing energy bias in the region of interest.

Core claim

The optimized energy reconstruction in LEGEND-200 achieves a combined average resolution of 2.47 ± 0.08 keV at 2039 keV. Weekly calibration peak positions vary by less than 0.05 keV up to 2614.5 keV, and systematic corrections remove residual non-linearities and bias in the region of interest.

What carries the argument

Weekly 228Th source calibration runs combined with peak-shape modeling and systematic non-linearity corrections to determine and stabilize the energy scale.

If this is right

  • The reported resolution and stability allow the experiment to set limits on neutrinoless double beta decay with reduced uncertainty from energy scale errors.
  • Systematic corrections applied in the region of interest remove measurable bias that would otherwise broaden or shift the expected signal peak.
  • High stability across many detectors supports uniform treatment of the full detector array in the blinded analysis.
  • The digital signal processing pipeline maintains performance without introducing additional time-dependent offsets.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the same calibration approach scales to larger detector masses, future phases of the experiment could maintain comparable resolution without proportional increases in calibration overhead.
  • The demonstrated level of energy-scale control could be compared directly with other germanium-based double beta decay searches to isolate differences in background modeling.
  • Residual non-linearities that remain after correction set a practical floor on how precisely the experiment can locate any candidate signal relative to the known Q-value.

Load-bearing premise

That the chosen weekly thorium calibrations and peak models fully capture all time-dependent and detector-specific variations that occur during actual physics data taking.

What would settle it

Observation of calibration peak shifts larger than 0.05 keV or resolution degradation beyond 2.55 keV at 2039 keV in a set of physics runs that were not used for the calibration fit.

read the original abstract

This paper describes the energy scale procedures and germanium detectors performance in the LEGEND-200 experiment, a critical component for the first unblinding in the search for neutrinoless double beta decay. We detail the digital signal processing pipeline, the methodologies for peak-shape modeling and energy calibration procedures utilizing weekly $^{228}$Th source calibration runs. The optimized energy reconstruction achieves a combined average resolution of $(2.47 \pm 0.08)$~keV at $Q_{\beta\beta} = 2039$~keV. The weekly variation of calibration peak positions are below 0.05~keV for energies up to 2614.5~keV, showing a high stability of the energy scale over time and across detectors. Furthermore, systematic corrections effectively address residual non-linearities and energy bias in the region of interest.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. This manuscript describes the digital signal processing pipeline, peak-shape modeling, and energy calibration procedures for HPGe detectors in the LEGEND-200 experiment, based on weekly 228Th source calibration runs. It reports a combined average resolution of (2.47 ± 0.08) keV at Q_ββ = 2039 keV, weekly calibration peak position variations below 0.05 keV up to 2614.5 keV, and the effectiveness of systematic corrections for residual non-linearities and energy bias in the region of interest.

Significance. If the reported resolution, stability, and correction efficacy apply to physics data, this constitutes an important experimental benchmark for the LEGEND-200 0νββ search, directly supporting background rejection and energy-scale precision in the ROI. The concrete measured values from calibration data provide a clear performance baseline for the detector array.

major comments (2)
  1. [energy calibration procedures and systematic corrections] The central performance claims (resolution at 2039 keV and stability) are derived exclusively from weekly 228Th source runs. The manuscript must demonstrate, with explicit cross-checks or independent validation, that these results and the associated systematic corrections hold during source-free physics data taking, where instantaneous rates, pile-up, baseline, and temperature coupling differ. This is load-bearing for applicability to the 0νββ search data.
  2. [peak-shape modeling and energy calibration procedures] Details on data selection criteria for the weekly calibration runs, error propagation in the quoted (2.47 ± 0.08) keV resolution, and quantitative validation of the peak-shape models are insufficiently described. These gaps directly affect confidence in the reported numbers and their uncertainties.
minor comments (1)
  1. [abstract] The abstract sentence 'The weekly variation of calibration peak positions are below 0.05 keV' contains a subject-verb agreement issue ('variation ... are').

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for their thorough review and valuable comments on our manuscript. We address the major comments point by point below, proposing revisions to improve clarity and completeness where possible.

read point-by-point responses

  1. Referee: [energy calibration procedures and systematic corrections] The central performance claims (resolution at 2039 keV and stability) are derived exclusively from weekly 228Th source runs. The manuscript must demonstrate, with explicit cross-checks or independent validation, that these results and the associated systematic corrections hold during source-free physics data taking, where instantaneous rates, pile-up, baseline, and temperature coupling differ. This is load-bearing for applicability to the 0νββ search data.

    Authors: The reported performance is based on calibration data because it allows for high-statistics measurements under controlled conditions. The same digital signal processing and calibration procedures are applied to the physics data. We will revise the manuscript to include a dedicated discussion on the applicability, noting that temperature and baseline conditions are monitored and stabilized similarly in both cases, and that pile-up is handled by the same algorithms. However, explicit cross-checks using physics data peaks are limited by the low event rates in the ROI and the blinded nature of the 0νββ analysis. We propose this as a partial revision. revision: partial

  2. Referee: [peak-shape modeling and energy calibration procedures] Details on data selection criteria for the weekly calibration runs, error propagation in the quoted (2.47 ± 0.08) keV resolution, and quantitative validation of the peak-shape models are insufficiently described. These gaps directly affect confidence in the reported numbers and their uncertainties.

    Authors: We agree that additional details are required. The revised manuscript will include: (1) explicit data selection criteria for the calibration runs, such as quality cuts and event selection; (2) a description of the error propagation for the resolution, including statistical and systematic contributions leading to the ±0.08 keV uncertainty; and (3) quantitative validation of the peak-shape models, for example through fit residuals or chi-squared per degree of freedom. These additions will be made in the relevant sections on peak-shape modeling and energy calibration. revision: yes

standing simulated objections not resolved
  • Providing explicit cross-checks or independent validation of the resolution and systematic corrections using source-free physics data, due to the blinded analysis strategy and significantly lower event rates in the region of interest.

Circularity Check

0 steps flagged

No circularity: experimental calibration report with no self-referential derivations

full rationale

The paper is a pure experimental methods and performance report. It describes digital signal processing, peak-shape modeling, and energy calibration procedures applied to weekly 228Th source runs, then reports measured quantities (resolution of 2.47 ± 0.08 keV at 2039 keV, peak-position stability <0.05 keV). No equations, predictions, or central claims reduce by construction to fitted parameters or self-citations; the reported numbers are direct outputs of the calibration pipeline applied to external source data. No uniqueness theorems, ansatzes smuggled via citation, or renaming of known results appear. The load-bearing assumption (that calibration runs adequately represent physics data) is an empirical question of applicability, not a circularity in the derivation chain itself. This meets the default expectation for an experimental instrumentation paper.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work is experimental calibration reporting measured performance; it relies on standard domain assumptions of gamma spectroscopy rather than introducing new free parameters, axioms, or entities.

axioms (1)
  • domain assumption Standard gamma-ray peak shape models and energy response assumptions hold without significant unaccounted biases for these HPGe detectors.
    Invoked implicitly in the peak-shape modeling and energy calibration procedures described.

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