A new method of energy reconstruction for large spherical liquid scintillator detectors

Abstract

A: Liquid scintillators are commonly used to detect low energy neutrinos from the reactors, sun, and earth. It is a challenge to reconstruct deposited energies for a large liquid scintillator detector. For detectors with multiple optical mediums such as JUNO and SNO+, the prediction of the propagation of detected photons is extremely difficult due to mixed optical processes such as Rayleigh scattering, refraction and total reflection at their boundaries. Calibration based reconstruction methods consume impractical time since a large number of calibration points are required in a giant detector. In this paper, we propose a new model-independent method to reconstruct deposited energies with minimum requirements on the calibration system. This method is validated with JUNO's offline software. Monte Carlo studies show that the energy non-uniformity can be controlled below 1%, which is crucial for JUNO to achieve 3% energy resolution.

Event vertex and time reconstruction in large-volume liquid scintillator detectors

“…Another solution is to use a model independent method described in Ref. [30] to obtain the mean expected number of photoelectrons by putting gamma sources at 29 specific positions along the Z axis, which can be done through calibration procedure [31]. Unlike Ref.…”

Improving the energy uniformity for large liquid scintillator detectors

“…As described in Ref. [13], an optical model independent method was developed to reconstruct the energy of positrons in the JUNO CD. The observables for each positron are {k i }, where k i represents the number of detected PEs for the i th PMT and is expected to follow a Poisson distribution.…”

“…In Ref. [13], it is derived from the ACU calibration data, under the assumption that the JUNO CD has good spherical symmetry. If the calibration source position is defined as r = (r, θ, φ = 0) and the i th PMT position as R i , as shown in Fig.…”

“…Due to the complicated optical processes, an optical model independent method [13] was developed previously to reconstruct the energy of positrons from inverse β-decay (IBD) events in the Central Detector (CD) of JUNO. The basic idea is to construct the maps of expected photoelectrons (PEs) for Photomultiplier tubes (PMTs) from calibration data, and then use these maps to build a maximum likelihood function to reconstruct the event energy.…”

Measurements of Rayleigh Ratios in Linear Alkylbenzene

“…Besides, the Rayleigh scattering length itself is important for more comprehensive understanding of light propagation in large LS detectors. The space and time patterns of photons are modified due to Rayleigh scattering, which requires correct consideration in event reconstruction [12]. Optical processes in the LS detectors are dominated by the solvent due to its large amount, thus the optical properties of LAB are key indices for these experiments.…”