China

Xuewei Liu

Wei Dou

Japan

Benda Xu

Hanwen Wang

Guofu Cao

Erratum to: First-principle event reconstruction by time-charge readouts for TAO

The Taishan Antineutrino Observatory (TAO) is a liquid-scintillator satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO) to measure the reference reactor neutrino spectrum with unprecedented energy resolution. We use inhomogeneous Poisson process and Tweedie generalized linear model (GLM) to characterize the detector response and the charge distribution of a SiPM. We develop a pure probabilistic model for time and charge of SiPMs from first principles to reconstruct point-like events in the TAO central detector. Thanks to our precise model and the high photo-coverage and quantum efficiency of the SiPM tiles at TAO, we achieve vertex position resolution better than $$20\,\hbox {mm}$$ , energy resolution of about $$2\%$$ at $$1\,\hbox {MeV}$$ and $$<0.5\%$$ non-uniformity, marking the world’s best performance of liquid scintillator detectors. With such resolution, we perceive $$\hbox {MeV}$$ events to exhibit track effects. It opens up an exciting possibility of computed tracking calorimeter for unsegmented liquid scintillator detector like TAO. Our methodology is applicable to other experiments that utilize PMTs for time and charge readouts.

First-principle event reconstruction by time-charge readouts for TAO

CP violation in baryonic decays has not been significantly observed. With large data events accumulated at   $ {e^+e^-} $   colliders or the Large Hadron Collider, charmed baryon decays would provide a promising laboratory to test CP symmetry. In this study, we formulate   $ {e^+e^-} $   and   $ {e^+e^-} $   decays for the measurement of their asymmetry parameters in weak decays at the BESIII or LHCb experiments. The polarization transfer is analyzed in the two processes of   $ {e^+e^-} $   and   $ {e^+e^-} $  , and the formulas for the joint angular distribution of these processes are provided. The sensitivity of the measurement of the asymmetry parameters of the above two decay processes is estimated for future experiments.

Peng-Cheng Hong

Fang Yan

Rong-Gang Ping

Tao Luo

Study of parity violation in And Decays  

The Taishan Antineutrino Observatory (TAO or JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). Located near a reactor of the Taishan Nuclear Power Plant, TAO will measure the reactor antineutrino energy spectrum with an unprecedented energy resolution of  $$&lt;2\%$$  <math> <mrow> <mo>&lt;</mo> <mn>2</mn> <mo>%</mo> </mrow> </math>   at 1 MeV. Energy calibration is critical to achieve such a high energy resolution. Using the Automated Calibration Unit (ACU) and the Cable Loop System (CLS), multiple radioactive sources are deployed to various positions in the TAO detector for energy calibration. The residual non-uniformity can be controlled within 0.2%. The energy resolution degradation and energy bias caused by the residual non-uniformity can be controlled within 0.05% and 0.3%, respectively. The uncertainty of the non-linear energy response can be controlled within 0.6% with the radioactive sources of various energies, and could be further improved with cosmogenic  $$^{12}{\textrm{B}}$$  <math> <mrow> <msup> <mrow></mrow> <mn>12</mn> </msup> <mtext>B</mtext> </mrow> </math>   which is produced by the interaction of cosmic muon in the liquid scintillator. The stability of other detector parameters, e.g., the gain of each Silicon Photo-multiplier, will be monitored with an ultraviolet LED calibration system.

Hangkun Xu

Chile

Angel Abusleme

JINR

Nikolay Anfimov

France

Stéphane Callier

Agustin Campeny

Jun Cao

Cedric Cerna

Yu Chen

Russia

Alexander Chepurnov

Yayun Ding

Frederic Druillole

Italy

Andrea Fabbri

Zhengyong Fei

Maxim Gromov

Miao He

Wei He

Yuanqiang He

Joseph Hor

Shaojing Hou

Jianrun Hu

Jun Hu

Cédric Huss

Xiaolu Ji

Tao Jiang

Xiaoshan Jiang

Cécile Jolliet

Daozheng Li

Min Li

Ruhui Li

Yichen Li

Caimei Liu

Mengchao Liu

Yunzhe Liu

Claudio Lombardo

Selma Lorenzo

Peizhi Lu

Guang Luo

Stefano Mari

Xiaoyan Ma

Paolo Montini

Juan Ochoa-Ricoux

Yatian Pei

Frédéric Perrot

Fabrizio Petrucci

Xiaohui Qian

Abdel Rebii

Czechia

Bedr̆ich Roskovec

Arsenij Rybnikov

Germany

Hans Steiger

Xilei Sun

Pablo Walker

Derun Wang

Meifen Wang

Wei Wang

Zhimin Wang

Diru Wu

Xiang Xiao

Yuguang Xie

Zhangquan Xie

Wenqi Yan

Huan Yang

Haifeng Yao

Mei Ye

Chengzhuo Yuan

Kirill Zamogilnyi

Liang Zhan

Jie Zhang

Shuihan Zhang

Rong Zhao

Calibration strategy of the JUNO-TAO experiment

We study the sensitivity of JUNO and TAO to the oscillations induced by two well-motivated scenarios beyond the standard model: large extra dimensions (LEDs) and light sterile neutrinos in the context of <math><mrow><mn>3</mn><mo>+</mo><mn>1</mn></mrow></math> neutrino mixing. We find that <math><mrow><mi>JUNO</mi><mo>+</mo><mi>TAO</mi></mrow></math> can set competitive bounds on the parameter space of each scenario. In particular, we find that <math><mrow><mi>JUNO</mi><mo>+</mo><mi>TAO</mi></mrow></math> can be competitive with MINOS, DUNE, or KATRIN in the context of LED. If LEDs are present in nature, we show that the parameters could be measured with a similar precision as the standard oscillation parameters. We also show that <math><mrow><mi>JUNO</mi><mo>+</mo><mi>TAO</mi></mrow></math> can test nearly all of the parameter space preferred by gallium experiments in the context of <math><mrow><mn>3</mn><mo>+</mo><mn>1</mn></mrow></math> mixing. Finally, we discuss the possibility to distinguish the two scenarios from each other.

Colombia

Brazil

V. S. Basto-Gonzalez

D. V. Forero

C. Giunti

A. A. Quiroga

C. A. Ternes

Short-baseline oscillation scenarios at JUNO and TAO

We report a sensitive study of  $$D_s^+ \rightarrow \tau ^+ \nu _{\tau }$$  <math> <mrow> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>τ</mi> </msub> </mrow> </math>   decay via  $$\tau ^+ \rightarrow e^+ \nu _e \bar{\nu }_{\tau }$$  <math> <mrow> <msup> <mi>τ</mi> <mo>+</mo> </msup> <mo>→</mo> <msup> <mi>e</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>e</mi> </msub> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>τ</mi> </msub> </mrow> </math>   with an integrated luminosity of 1 ab $$^{-1}$$  <math> <msup> <mrow></mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </math>   at the center-of-mass energy of 4.009 GeV at a future Super Tau Charm Facility (STCF). Under the help of the fast simulation software package, the statistical sensitivity for the absolute branching fraction of  $$D_s^+ \rightarrow \tau ^+ \nu _{\tau }$$  <math> <mrow> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>τ</mi> </msub> </mrow> </math>   is determined to be  $$2\times 10^{-4}$$  <math> <mrow> <mn>2</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>4</mn> </mrow> </msup> </mrow> </math>  . Combining with our previous prospect of  $$D_s^+ \rightarrow \mu ^+ \nu _{\mu }$$  <math> <mrow> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi>μ</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>μ</mi> </msub> </mrow> </math>  , the ratio of the branching fractions for  $$D_s^+ \rightarrow \tau ^+ \nu _{\tau }$$  <math> <mrow> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>τ</mi> </msub> </mrow> </math>   over  $$D_s^+ \rightarrow \mu ^+ \nu _{\mu }$$  <math> <mrow> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi>μ</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>μ</mi> </msub> </mrow> </math>   can achieve a relative statistical precision of 0.5%, which will provide the most stringent test of the  $$\tau $$  <math> <mi>τ</mi> </math>  - $$\mu $$  <math> <mi>μ</mi> </math>   lepton flavor universality in heavy quark decays. Taking the decay constant  $$f_{D_s^+}$$  <math> <msub> <mi>f</mi> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> </msub> </math>   from lattice QCD calculations or the CKM matrix element  $$|V_{cs}|$$  <math> <mrow> <mrow> <mo>|</mo> </mrow> <msub> <mi>V</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>|</mo> </mrow> </mrow> </math>   from the CKMfitter group as an input, the relative statistical uncertainties for  $$|V_{cs}|$$  <math> <mrow> <mrow> <mo>|</mo> </mrow> <msub> <mi>V</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>|</mo> </mrow> </mrow> </math>   and  $$f_{D_s^+}$$  <math> <msub> <mi>f</mi> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> </msub> </math>   are estimated to be 0.3% and 0.2%, respectively.

Huijing Li

Xiaodong Shi

Xiaorong Zhou

Feasibility study of  $$D_s^+ \rightarrow \tau ^+ \nu _{\tau }$$  <math> <mrow> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> <mo>→</mo> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>τ</mi> </msub> </mrow> </math>   decay and test of lepton flavor universality with leptonic  $$D_s^+$$  <math> <msubsup> <mi>D</mi> <mi>s</mi> <mo>+</mo> </msubsup> </math>   decays at STCF

This work presents a sensitivity study of a reactor liquid scintillator detector to three kinds of dark bosons with masses below 1 MeV, such as dark photons, axion-like particles, and light scalar bosons. The JUNO-TAO detector with Taishan nuclear reactor is taken as a reference. With a proposed 180 days of data taking, the best sensitivity result at the level of <math><mrow><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup></mrow></math> 95% C.L. is achieved for dark photons with an optimized signal to background ratio for the electron coupling constant <math><mrow><msub><mrow><mi>g</mi></mrow><mrow><mi>X</mi></mrow></msub></mrow></math> through inverse Compton-like scattering. Similar calculations are completed for axion-like particles and scalar bosons. The background systematic uncertainty presents as the main limiting factor for the further sensitivity improvement. Several remarks are made to the controversial analysis for the NEOS experiment. Additionally the differential and the inverse differential cross sections have been derived for all three boson types and their interactions with electrons in liquid scintillator.

Mikhail Smirnov

United States

Guang Yang

Jiajun Liao

Zhuojun Hu

Jiajie Ling

Light dark bosons in the JUNO-TAO neutrino detector

The semileptonic decay of heavy flavor mesons offers a clean environment for extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, which describes the CP-violating and flavor changing process in the Standard Model. The involved form factors where the dynamical information is encoded play an essential role in achieving any conclusive statement. That is, the knowledge of the form factors should be under good control, requiring one to examine more observables in addition to the branching fraction. In this paper, we provide the mean value and the q 2-dependent shape for further observables [differential decay distribution (dΓ/dq 2), forward-backward asymmetry   <math> <mfenced> <msubsup> <mi>A</mi> <mi>FB</mi> <mi>ls</mi> </msubsup> </mfenced> </math>  $$ \left({\mathcal{A}}_{FB}^{ls}\right) $$ , longitudinal   <math> <mfenced> <msubsup> <mi>P</mi> <mi>L</mi> <mi>l</mi> </msubsup> </mfenced> </math>  $$ \left({P}_L^l\right) $$  and transverse   <math> <mfenced> <msubsup> <mi>P</mi> <mi>T</mi> <mi>l</mi> </msubsup> </mfenced> </math>  $$ \left({P}_T^l\right) $$  polarization of a charged lepton, longitudinal polarization of a vector meson in the final state   <math> <mfenced> <mrow> <msubsup> <mi>F</mi> <mi>L</mi> <mi>l</mi> </msubsup> <mfenced> <mi>V</mi> </mfenced> </mrow> </mfenced> </math>  $$ \left({F}_L^l(V)\right) $$ , leptonic convexity parameter   <math> <mfenced> <msubsup> <mi>C</mi> <mi>F</mi> <mi>l</mi> </msubsup> </mfenced> </math>  $$ \left({C}_F^l\right) $$ , and trigonometric moments   <math> <mfenced> <msubsup> <mi>W</mi> <mi>i</mi> <mi>l</mi> </msubsup> </mfenced> </math>  $$ \left({W}_i^l\right) $$  in the decay of D (s) and B (s) to P/Vl + ν  l  (l = e, μ or τ)], based on the predictions of the relevant form factors from the covariant light-front quark model. P and V denote the pseudoscalar and vector meson, respectively. As a comparison, we find a good agreement with the results from the covariant confining quark model and the relativistic quark model in the literature. As it has been observed that the   <math> <msubsup> <mi>P</mi> <mi>L</mi> <mi>l</mi> </msubsup> </math>  $$ {P}_L^l $$  and   <math> <msubsup> <mi>F</mi> <mi>L</mi> <mi>l</mi> </msubsup> <mfenced> <mi>V</mi> </mfenced> </math>  $$ {F}_L^l(V) $$  are crucial quantities to discriminate various New Physics models, the reexamination of these observables from a different method is also essential and necessary.

Lu Zhang

Xian-Wei Kang

Xin-Heng Guo

Ling-Yun Dai

Chao Wang

A comprehensive study on the semileptonic decay of heavy flavor mesons

The Jiangmen Underground Neutrino Observatory (JUNO) project aims at probing, at the same time, the two main frequencies of three-flavor neutrino oscillations, as well as their interference related to the mass ordering (normal or inverted), at a distance of <math><mo>∼</mo><mn>53</mn><mtext> </mtext><mtext> </mtext><mi>km</mi></math> from two powerful reactor complexes in China, at Yangjiang and Taishan. In the latter complex, the unoscillated spectrum from one reactor core is planned to be closely monitored by the Taishan Antineutrino Observatory (TAO), expected to have better resolution (<math><mo>×</mo><mn>1</mn><mo>/</mo><mn>2</mn></math>) and higher statistics (<math><mo>×</mo><mn>30</mn></math>) than JUNO. In the context of <math><mi>ν</mi></math> energy spectra endowed with fine-structure features from summation calculations, we analyze in detail the effects of energy resolution and nucleon recoil on observable event spectra. We show that a model spectrum in TAO can be mapped into a corresponding spectrum in JUNO through appropriate convolutions. The mapping is exact in the hypothetical case without oscillations and holds to a very good accuracy in the real case with oscillations. We then analyze the sensitivity to mass ordering of JUNO (and its precision oscillometry capabilities) assuming a single reference spectrum, as well as bundles of variant spectra, as obtained by changing nuclear input uncertainties in summation calculations from a publicly available toolkit. We show through an <math><msup><mi>χ</mi><mn>2</mn></msup></math> analysis that variant spectra induce little reduction of the sensitivity in JUNO, especially when TAO constraints are included. Subtle aspects of the statistical analysis of variant spectra are also discussed.

Francesco Capozzi

Eligio Lisi

Antonio Marrone

Mapping reactor neutrino spectra from TAO to JUNO

Measurements of decay asymmetry parameters of charmed baryons, e.g., 
					, provide more data to test the W-emission and W-exchange mechanisms controlled by strong and weak interactions. Taking advantage of the spin polarization in charmed baryon decays, we investigate the possibility to measure weak decay asymmetry parameters in the 
					 process. We analyze the transverse polarization spontaneously produced in this process and the spin transfer in the subsequent 
					 decays. The sensitivity to measure the asymmetry parameters is estimated for the decay 
					.
				

Tong-Zhu Han

Guang-Zhi Xu

Polarization in 
					 decays Supported by the National Natural Science Foundation of China (11875262, 11805037, 11705078), Joint Large-Scale Scientific Facility Funds of the NSFC and CAS (U1832121), Shanghai Pujiang Program (18PJ1401000) and Open Research Program of Large Research Infrastructures (2017), Chinese Academy of Sciences