arxiv: 2512.15264 · v3 · submitted 2025-12-17 · ⚛️ physics.ins-det

Calibration Methods of Silicon Photomultiplier for JUNO-TAO Central Detector

Jiayang Xu , Yichen Li , Zhan Liang , Guofu Cao , Zelin Chen This is my paper

Pith reviewed 2026-05-16 21:39 UTC · model grok-4.3

classification ⚛️ physics.ins-det

keywords silicon photomultipliercalibrationJUNO-TAOdark count rateoptical crosstalkphoton detection efficiencyenergy resolutionneutrino detector

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The pith

Calibration of Silicon Photomultipliers in JUNO-TAO limits impacts on vertex and energy resolution to under 2% and 3%.

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

The paper establishes calibration procedures for the Silicon Photomultipliers in the JUNO-TAO central detector to support precise reactor antineutrino energy spectrum measurements with better than 2% resolution at 1 MeV. Channel-level methods use charge and time information to calibrate dark count rate, relative photon detection efficiency, time offset, gain, and internal optical crosstalk. A new tile-level approach for external optical crosstalk employs an LED to switch groups of SiPMs on and off. Simulations with one million events indicate that the resulting parameter biases are small enough to keep relative degradation in vertex precision below 2% and in energy resolution below 3%.

Core claim

The authors describe channel-level calibration methods for SiPM dark count rate, relative PDE, time offset, gain, and IOCT based on charge and time information, along with a novel method for tile-level EOCT rate and emission angle distribution by switching SiPM groups with an LED. Using one million simulated events, they evaluate expected biases: ~3% for relative PDE, 1.4% for IOCT, 0.4% for DCR, <0.1% for EOCT rate and gain, <0.2 ns for time offset, and <4% for the EOCT emission angle distribution in the main range. These accuracies ensure the overall impacts on vertex precision and energy resolution remain limited to relative degradations below 2% and 3%, respectively, verifying the method

What carries the argument

Charge and time based calibration for SiPM parameters combined with LED group-switching for external optical crosstalk measurement.

Load-bearing premise

The simulation of one million events accurately captures real detector behavior including LED light distribution and sensor response without unmodeled effects that would increase biases in actual operation.

What would settle it

Running the calibration on actual data from the deployed JUNO-TAO detector and comparing the obtained parameter values and resulting resolutions against the simulation predictions would falsify the claim if the observed degradations exceed 2% or 3%.

read the original abstract

The Taishan Antineutrino Observatory (TAO or JUNO-TAO) is a satellite observatory for the Jiangmen Underground Neutrino Observatory (JUNO), located 44 meters away from the No.1 reactor of the Taishan Nuclear Power Plant. TAO can measure the reactor antineutrino energy spectrum with excellent energy resolution (better than 2% at 1 MeV) using state-of-the-art Silicon Photomultipliers (SiPMs) operated at low temperature. To achieve this goal, the SiPMs (together with their readout electronics) must be well calibrated. This paper presents the channel-level calibration methods for the dark count rate (DCR), relative photon detection efficiency (PDE), time offset, gain, and internal optical crosstalk (IOCT) of the SiPMs based on charge and time information of the collected events. For the tile-level calibration of the external optical crosstalk (EOCT), in terms of its rate and emission angle distribution, a novel method is proposed by switching on and off different groups of SiPMs with an LED placed in the detector. Using one million simulated events, the expected calibration biases are evaluated for all the aforementioned parameters: relative PDE (~3%), IOCT (1.4%), DCR (0.4%), EOCT Rate (<0.1%), gain (<0.1%), time offset (<0.2 ns). The emission angle distribution of the EOCT photons could be measured with a bias of less than 4% in the main angular range. With the this calibration accuracy, the overall impacts of SiPM parameter uncertainties and calibration biases on vertex precision and energy resolution are limited, with relative degradation below 2% and 3%, respectively. It verifies the validity of the calibration method for the JUNO-TAO detector.

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.

Desk Editor's Note private letter to a colleague

The paper lays out usable channel-level SiPM calibration procedures plus a new LED group-switching method for external crosstalk, but all bias numbers and performance claims rest on one million simulated events with no real-data check.

read the letter

The main takeaway is that they give a clear, step-by-step set of methods for calibrating dark count rate, relative PDE, gain, time offset, and internal crosstalk from charge and time distributions, plus a practical LED-switching trick to measure external crosstalk rate and angular distribution at the tile level. The LED approach is presented as new and they show how to extract both quantities by turning groups on and off. That part is the actual addition worth noting for anyone building similar detectors. They run one million simulated events and report explicit bias figures: roughly 3% on PDE, 1.4% on IOCT, 0.4% on DCR, under 0.1% on EOCT rate and gain, under 0.2 ns on time offset, and under 4% on the angular distribution in the main range. They then propagate those numbers to claim relative degradation stays below 2% on vertex precision and 3% on energy resolution. The simulation checks are transparent and the numbers are given directly, which is better than many calibration papers that stop at the method. The soft spot is obvious and not minor: everything is simulation only. There is no real detector data shown to test whether the LED light distribution, sensor response, or unmodeled effects match the model, so the final impact numbers could move if the assumptions do not hold in the actual TAO setup. Event selection thresholds are listed as free parameters but not varied in the reported results. This is for the JUNO-TAO collaboration and groups doing SiPM work in large liquid-scintillator detectors who need concrete procedures they can adapt. A reader who wants the LED method or the bias estimates would get direct value. It deserves peer review because the methods are concrete and the simulation work is reproducible enough for referees to check the assumptions and ask for real-data validation in revision.

Referee Report

2 major / 2 minor

Summary. The manuscript presents channel-level calibration methods for SiPM parameters (DCR, relative PDE, time offset, gain, IOCT) extracted from charge and time distributions of collected events, along with a novel tile-level EOCT calibration using LED-driven group switching. Biases for all parameters are quantified from one million simulated events (PDE ~3%, IOCT 1.4%, DCR 0.4%, EOCT rate <0.1%, gain <0.1%, time offset <0.2 ns, EOCT angle distribution <4% bias in main range), and these are propagated to show relative impacts below 2% on vertex precision and 3% on energy resolution.

Significance. If the simulation model holds, the work supplies concrete, numerically explicit calibration procedures and bias estimates that keep SiPM uncertainties from materially degrading the <2% energy resolution target at 1 MeV. The direct extraction of biases from a large simulated sample and the parameter-free character of several reported quantities constitute clear strengths for an instrumentation paper supporting JUNO-TAO.

major comments (2)

[Abstract and results (bias evaluation)] Abstract and results section on bias propagation: the headline claims of relative degradation below 2% (vertex) and 3% (energy resolution) rest entirely on biases extracted from one million simulated events; any mismatch between the simulated LED light distribution, SiPM response, or unmodeled systematics and actual detector behavior would scale these impact numbers upward, yet no real-data cross-check or sensitivity study to model variations is provided.
[EOCT calibration subsection] EOCT tile-level method: the novel switching procedure for rate and emission-angle distribution is load-bearing for the <0.1% rate and <4% angle bias claims, but the manuscript does not quantify how uncertainties in the assumed LED spatial distribution or in the on/off switching transients propagate into the extracted EOCT parameters.

minor comments (2)

[Abstract] Abstract: the phrase 'With the this calibration accuracy' is grammatically incorrect and should read 'With this calibration accuracy'.
[Simulation and bias evaluation] The manuscript should add a short paragraph discussing the main assumptions of the simulation (LED uniformity, absence of temperature gradients, etc.) and how they might affect the quoted bias values.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive assessment of our manuscript and for the constructive comments. We address each major comment below and outline the revisions we will make.

read point-by-point responses

Referee: Abstract and results section on bias propagation: the headline claims of relative degradation below 2% (vertex) and 3% (energy resolution) rest entirely on biases extracted from one million simulated events; any mismatch between the simulated LED light distribution, SiPM response, or unmodeled systematics and actual detector behavior would scale these impact numbers upward, yet no real-data cross-check or sensitivity study to model variations is provided.

Authors: We acknowledge that all bias evaluations and propagated impacts are derived from one million simulated events. Real calibration data from the JUNO-TAO detector are not yet available, as the detector is still under construction. To address the concern about model dependence, we will add a dedicated sensitivity study in the revised manuscript. This study will vary key simulation inputs (LED light distribution, SiPM response models, and selected unmodeled systematics) and report the resulting changes to the bias and impact figures, thereby quantifying the robustness of the headline claims. revision: partial
Referee: EOCT tile-level method: the novel switching procedure for rate and emission-angle distribution is load-bearing for the <0.1% rate and <4% angle bias claims, but the manuscript does not quantify how uncertainties in the assumed LED spatial distribution or in the on/off switching transients propagate into the extracted EOCT parameters.

Authors: We agree that explicit propagation of these uncertainties would strengthen the EOCT calibration section. In the revised manuscript we will include an additional analysis that quantifies how uncertainties in the assumed LED spatial distribution and in the on/off switching transients affect the extracted EOCT rate and emission-angle distribution. This will be performed via dedicated simulations that vary the relevant parameters within their expected ranges and report the resulting variations in the EOCT observables. revision: yes

Circularity Check

0 steps flagged

No significant circularity in calibration methods or bias propagation

full rationale

The paper presents channel-level calibration procedures that extract DCR, PDE, time offset, gain, and IOCT directly from measured charge and time distributions of collected events, without any equations that define the target quantities in terms of the fitted outputs. Tile-level EOCT calibration uses a switching method on LED-illuminated groups. Bias estimates for these parameters are obtained by applying the same extraction procedures to one million independent simulated events that encode the assumed light distribution and sensor response; these simulations serve as an external benchmark rather than a self-referential input. The final impact figures (<2% vertex, <3% energy resolution degradation) are obtained by standard propagation of the reported bias values and do not reduce to the calibration inputs by construction. No load-bearing self-citations, uniqueness theorems, or ansatzes are invoked in the provided derivation chain.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Calibration relies on standard statistical models for photon counting and signal timing plus simulated data for bias estimation; no new entities are introduced.

free parameters (1)

event selection thresholds
Thresholds for identifying dark counts, single-photon events, and crosstalk signals are required but not numerically specified in the abstract.

axioms (1)

standard math Poisson statistics govern dark counts and photon arrivals
Implicit in dark count rate and photon detection efficiency extraction from charge spectra.

pith-pipeline@v0.9.0 · 5646 in / 1189 out tokens · 57793 ms · 2026-05-16T21:39:38.028153+00:00 · methodology

discussion (0)

Reference graph

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