The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment under construction in South China. This paper presents an updated estimate of JUNO’s sensitivity to neutrino mass ordering using the reactor antineutrinos emitted from eight nuclear reactor cores in the Taishan and Yangjiang nuclear power plants. This measurement is planned by studying the fine interference pattern caused by quasi-vacuum oscillations in the oscillated antineutrino spectrum at a baseline of 52.5 km and is completely independent of the CP violating phase and neutrino mixing angle θ $_{23}$. The sensitivity is obtained through a joint analysis of JUNO and Taishan Antineutrino Observatory (TAO) detectors utilizing the best available knowledge to date about the location and overburden of the JUNO experimental site, local and global nuclear reactors, JUNO and TAO detector responses, expected event rates and spectra of signals and backgrounds, and systematic uncertainties of analysis inputs. We find that a 3σ median sensitivity to reject the wrong mass ordering hypothesis can be reached with an exposure of about 6.5 years × 26.6 GW thermal power.

Chile

Angel Abusleme

France

Thomas Adam

Pakistan

Shakeel Ahmad

Rizwan Ahmed

Italy

Sebastiano Aiello

Muhammad Akram

Abid Aleem

China

Fengpeng An

Qi An

Giuseppe Andronico

JINR

Nikolay Anfimov

Vito Antonelli

Tatiana Antoshkina

Thailand

Burin Asavapibhop

João Pedro Athayde Marcondes de André

Didier Auguste

Weidong Bai

Nikita Balashov

Wander Baldini

Andrea Barresi

Davide Basilico

Eric Baussan

Marco Bellato

Marco Beretta

Antonio Bergnoli

Germany

Daniel Bick

Lukas Bieger

Svetlana Biktemerova

Thilo Birkenfeld

Iwan Morton-Blake

David Blum

Simon Blyth

Anastasia Bolshakova

Mathieu Bongrand

Taiwan

Clément Bordereau

Dominique Breton

Augusto Brigatti

Riccardo Brugnera

Riccardo Bruno

Antonio Budano

Jose Busto

Anatael Cabrera

Barbara Caccianiga

Hao Cai

Xiao Cai

Yanke Cai

Zhiyan Cai

Stéphane Callier

Antonio Cammi

Agustin Campeny

Chuanya Cao

Guofu Cao

Jun Cao

Rossella Caruso

Cédric Cerna

Vanessa Cerrone

Chi Chan

Jinfan Chang

Yun Chang

Auttakit Chatrabhuti

Chao Chen

Guoming Chen

Pingping Chen

Shaomin Chen

Yixue Chen

Yu Chen

Zhangming Chen

Zhiyuan Chen

Zikang Chen

Jie Cheng

Yaping Cheng

Yu Chin Cheng

Russia

Alexander Chepurnov

Alexey Chetverikov

Davide Chiesa

Brazil

Pietro Chimenti

Yen-Ting Chin

Ziliang Chu

Artem Chukanov

Gérard Claverie

Catia Clementi

Belgium

Barbara Clerbaux

Marta Colomer Molla

Selma Conforti DiLorenzo

Alberto Coppi

Daniele Corti

Simon Csakli

Flavio Dal Corso

United States

Olivia Dalager

Jaydeep Datta

Christophe De La Taille

Zhi Deng

Ziyan Deng

Xiaoyu Ding

Xuefeng Ding

Yayun Ding

Bayu Dirgantara

Carsten Dittrich

Sergey Dmitrievsky

Czechia

Tadeas Dohnal

Potential to identify neutrino mass ordering with reactor antineutrinos at JUNO  

The neutron total cross section of iron ( natFe) plays an important role in the basic science of nuclear physics, nuclear technology and nuclear energy application. A new measurement of the total cross section of iron from 0.3 eV to 150 MeV was carried out in single and double bunch modes by transmission method and time of flight method with multi-cell fast fission ionization chamber (FIC) with 235U and 238U coating materials at the China Spallation Neutron Source (CSNS). Normalized fission counts-neutron energy spectra for sample-in and sample-out states were obtained and superimposed. The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV. The transmissions obtained in single bunch and unfolded in double bunch coincided well. From 0.3 eV to 150 MeV, the ratio of most energy points of cross section in single bunch and in double bunch fluctuates within 10 %. In the energy range of 0.3 eV to 10 keV, the experimental results using 20 mm and 40 mm thickness iron samples both agree very well with the evaluated data of JEFF-3.3 and ENDF/B-VIII.0 at most energy points, fluctuating within 3 %. In the energy range of 10 keV to 150 MeV, the results agree well with the evaluated data in terms of values and trends. The main resonance peaks of the total cross section of iron at the energies of 3.94 keV, 6.24 keV, 7.76 keV, 27.9 keV, 52.1 keV, 74.1 keV, 83.9 keV, 141 keV, 170 keV, 188 keV and 386 keV are well represented in our results. The relative uncertainties of the total cross sections using the 40 mm iron sample by FIC- 235U are within 2 % at most energy points. In 1.5 MeV-140 MeV region, the relative uncertainties of the total cross section using the 20 mm iron and 40 mm iron samples by FIC- 238U are around 2 % and 1 %, respectively. The total cross section results can be used as a reference for nuclear data evaluation.

Jiangbo Bai

Jingyu Tang

Liqun Shi

Yonghao Chen

Han Yi

Guohui Zhang

Haofan Bai

Jie Bao

Ping Cao

Zhen Chen

Zengqi Cui

Anchuan Fan

Ruirui Fan

Changqing Feng

Fanzhen Feng

Keqing Gao

MinHao Gu

Changcai Han

Guozhu He

Yongcheng He

Yang Hong

Yiwei Hu

Hanxiong Huang

Weihua Jia

Haoyu Jiang

Wei Jiang

Zhijie Jiang

Zhengyao Jin

Ling Kang

Bo Li

Chao Li

Gong Li

Jiawen Li

Qiang Li

Xiao Li

Yang Li

Jie Liu

Shubin Liu

Guangyuan Luan

Changjun Ning

Binbin Qi

Jie Ren

Xichao Ruan

Zhaohui Song

Kang Sun

Zhixin Tan

Shengda Tang

Lijiao Wang

Pengcheng Wang

Zhaohui Wang

Xiaoguang Wu

Xuan Wu

Likun Xie

Yongji Yu

Linhao Zhang

Mohan Zhang

Qiwei Zhang

Xianpeng Zhang

Yuliang Zhang

Yue Zhang

Zhiyong Zhang

Maoyuan Zhao

Luping Zhou

Zhihao Zhou

Kejun Zhu

Measurement of the neutron total cross section of Iron at the Back-n white neutron source of CSNS

Photomultiplier tubes (PMTs) are widely used in particle experiments for photon detection. PMT waveform analysis is crucial for high-precision measurements of the position and energy of incident particles in liquid scintillator (LS) detectors. A key factor contributing to the energy resolution in large liquid scintillator detectors with PMTs is the charge smearing of PMTs. This paper presents a machine-learning-based photon counting method for PMT waveforms and its application to the energy reconstruction, using the JUNO experiment as an example. The results indicate that leveraging the photon counting information from the machine learning model can partially mitigate the impact of PMT charge smearing and lead to a relative 2.0–2.8% improvement on the energy resolution in the energy range of [1, 9] MeV.

Guihong Huang

Zhen Liu

Wuming Luo

Liangjian Wen

Jianyi Luo

Machine-learning based photon counting for PMT waveforms and its application to the improvement of the energy resolution in large liquid scintillator detectors

We explore the decay of bound neutrons in the JUNO liquid scintillator detector into invisible particles (e.g., $$n\rightarrow 3 \nu $$ or $$nn \rightarrow 2 \nu $$ ), which do not produce an observable signal. The invisible decay includes two decay modes: $$ n \rightarrow { inv} $$ and $$ nn \rightarrow { inv} $$ . The invisible decays of -shell neutrons in $$^{12}\textrm{C}$$ will leave a highly excited residual nucleus. Subsequently, some de-excitation modes of the excited residual nuclei can produce a time- and space-correlated triple coincidence signal in the JUNO detector. Based on a full Monte Carlo simulation informed with the latest available data, we estimate all backgrounds, including inverse beta decay events of the reactor antineutrino $${\bar{\nu }}_e$$ , natural radioactivity, cosmogenic isotopes and neutral current interactions of atmospheric neutrinos. Pulse shape discrimination and multivariate analysis techniques are employed to further suppress backgrounds. With two years of exposure, JUNO is expected to give an order of magnitude improvement compared to the current best limits. After 10 years of data taking, the JUNO expected sensitivities at a 90% confidence level are $$\tau /B( n \rightarrow { inv} ) > 5.0 \times 10^{31} \, \textrm{years}$$ and $$\tau /B( nn \rightarrow { inv} ) > 1.4 \times 10^{32} \, \textrm{years}$$ .