0000000000179672
AUTHOR
Qian Liu
Rayleigh scattering of linear alkylbenzene in large liquid scintillator detectors.
Rayleigh scattering poses an intrinsic limit for the transparency of organic liquid scintillators. This work focuses on the Rayleigh scattering length of linear alkylbenzene (LAB), which will be used as the solvent of the liquid scintillator in the central detector of the Jiangmen Underground Neutrino Observatory. We investigate the anisotropy of the Rayleigh scattering in LAB, showing that the resulting Rayleigh scattering length will be significantly shorter than reported before. Given the same overall light attenuation, this will result in a more efficient transmission of photons through the scintillator, increasing the amount of light collected by the photosensors and thereby the energy…
Calibration strategy of the JUNO experiment
We present the calibration strategy for the 20 kton liquid scintillator central detector of the Jiangmen Underground Neutrino Observatory (JUNO). By utilizing a comprehensive multiple-source and multiple-positional calibration program, in combination with a novel dual calorimetry technique exploiting two independent photosensors and readout systems, we demonstrate that the JUNO central detector can achieve a better than 1% energy linearity and a 3% effective energy resolution, required by the neutrino mass ordering determination. [Figure not available: see fulltext.]
Search forηandη′→π+e−ν¯e+c.c.decays inJ/ψ→ϕηandϕη′
Using a sample of 225.3 million J/psi events collected with the BESIII detector at the BEPCII e(+)e(-) collider in 2009, searches for the decays of eta and eta' -> pi(+)e(-)(v) over bar (e) + c.c. in J/psi -> phi eta and phi eta' are performed. The phi signals, which are reconstructed in K+K- final states, are used to tag eta and eta' semileptonic decays. No signals are observed for either eta or eta', and upper limits at the 90% confidence level are determined to be 7.3 x 10(-4) and 5.0 x 10(-4) for the ratios B(eta ->pi(+)e(-)(v) over bar (e) + c.c)/B(eta ->pi(+)pi(-)pi(0)) and B(eta'->pi(+)e(-)(v) over bar (e) + c.c)/B(eta'->pi(+)pi(-)eta) respectively. These are the first upper- limit v…
Evidence forηc(2S)inψ(3686)→γKS0K±π∓π+π−
We search for the M1 radiative transition psi(3686) -> gamma eta(c)(2S) by reconstructing the exclusive eta(c)(2S) -> (KSK +/-)-K-0 pi(-/+)pi(+)pi(-) decay using 1.06 X 10(8) psi(3686) events collected with the BESIII detector. The signal is observed with a statistical significance of greater than 4 standard deviations. The measured mass of the eta(c)(2S) is 3646.9 +/- 1.6(stat) +/- 3.6(syst) MeV/c(2), and the width is 9.9 +/- 4.8(stat) +/- 2.9(syst) MeV/c(2). The product branching fraction is measured to be B(psi(3686) -> gamma eta(c)(2S)) X B(eta(c)(2S) -> gamma(KSK +/-)-K-0 pi(-/+)pi(+)pi(-) = (7.03 +/- 2.10(stat) +/- 0.70(syst)) X 10(-6). This measurement complements a previous BESIII m…
The Design and Sensitivity of JUNO's scintillator radiopurity pre-detector OSIRIS
The European physical journal / C 81(11), 973 (2021). doi:10.1140/epjc/s10052-021-09544-4
Observation ofe+e−→ηJ/ψat center-of-mass energys=4.009 GeV
Using a 478 pb(-1) data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring at a center-of-mass energy of root s = 4.009 GeV, the production of e(+)e(-) -> eta J/psi is observed for the first time with a statistical significance of greater than 10 sigma. The Born cross section is measured to be (32.1 +/- 2.8 +/- 1.3) pb, where the first error is statistical and the second systematic. Assuming the eta J/psi signal is from a hadronic transition of the psi(4040), the fractional transition rate is determined to be B(psi(4040) -> eta J/psi) = (5.2 +/- 0.5 +/- 0.2 +/- 0.5) x 10(-3), where the first, second, and third errors are statistical, s…
Radioactivity control strategy for the JUNO detector
JUNO is a massive liquid scintillator detector with a primary scientific goal of determining the neutrino mass ordering by studying the oscillated anti-neutrino flux coming from two nuclear power plants at 53 km distance. The expected signal anti-neutrino interaction rate is only 60 counts per day, therefore a careful control of the background sources due to radioactivity is critical. In particular, natural radioactivity present in all materials and in the environment represents a serious issue that could impair the sensitivity of the experiment if appropriate countermeasures were not foreseen. In this paper we discuss the background reduction strategies undertaken by the JUNO collaboration…
Search for hadronic transitionχcJ→ηcπ+π−and observation ofχcJ→KK¯πππ
Hadronic transitions of chi(cJ) -> eta(c)pi(+)pi(-) (J = 0, 1, 2) are searched for using a sample of 1.06 x 10(8) psi(3686) events collected with the BESIII detector at the BEPCII storage ring. The eta(c) is reconstructed with (KSK +/-)-K-0 pi(-/+) and K+K-pi(0) final states. No signals are observed in any of the three chi(cJ) states in either eta(c) decay mode. At the 90% confidence level, the upper limits are determined to be B(chi(c0) -> eta(c)pi(+)pi(-)) eta(c)pi(+)pi(-)) eta(c)pi(+)pi(-)) eta(c)pi(+)pi(-)) is lower than the existing theoretical prediction by almost an order of magnitude. The branching fractions of chi(cJ) -> (KSK +/-)-K-0 pi(-/+)pi(+)pi(-), K+K-pi(+)pi(-)pi(0), omega K…
Experimental study ofψ′decays toK+K−π0andK+K−η
Using (106 +/- 4) x 10(6) psi ' events accumulated with the BESIII detector at the BEPCII e(+)e(-) collider, we present measurements of the branching fractions for psi' decays to K+K- pi(0) and K+K- eta. In these final states, the decay psi' -> K-2(*) (1430)(+) K- + 10(-5), is observed for the first time, and its branching fraction is measured to be (7.12 +/- 0: 62(stat)(-0.61)(+1.13) (syst)) x 10(-5), which indicates a violation of the helicity selection rule in psi' decays. The branching fractions of psi' -> K* (892)(+) K- + c.c., phi eta, and phi pi(0) are also measured. The measurements are used to test the QCD predictions on charmonium decays.
Observation of the doubly radiative decay η′→γγπ0
Based on a sample of 1.31 billion J/psi events collected with the BESIII detector, we report the study of the doubly radiative decay eta' -> gamma gamma pi(0) for the first time, where the eta' meson is produced via the J/psi -> gamma eta' decay. The branching fraction of eta' -> gamma gamma pi(0) inclusive decay is measured to be B(eta' -> gamma gamma pi(0))(Incl) = (3.20 +/- 0.07(stat) +/- 0.23(sys)) x 10(-3), while the branching fractions of the dominant process eta' -> gamma omega and the non-resonant component are determined to be B(eta' -> gamma omega) x B(omega -> gamma pi(0)) = (23.7 +/- 1.4(stat) +/- 1.8(sys)) x 10(-4) and B(eta' -> gamma gamma pi(0))(NR) = (6.16 +/- 0.64(stat) +/-…
JUNO sensitivity to low energy atmospheric neutrino spectra
Atmospheric neutrinos are one of the most relevant natural neutrino sources that can be exploited to infer properties about cosmic rays and neutrino oscillations. The Jiangmen Underground Neutrino Observatory (JUNO) experiment, a 20 kton liquid scintillator detector with excellent energy resolution is currently under construction in China. JUNO will be able to detect several atmospheric neutrinos per day given the large volume. A study on the JUNO detection and reconstruction capabilities of atmospheric $\nu_e$ and $\nu_\mu$ fluxes is presented in this paper. In this study, a sample of atmospheric neutrino Monte Carlo events has been generated, starting from theoretical models, and then pro…
Neutrino Physics with JUNO
The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy as a primary physics goal. It is also capable of observing neutrinos from terrestrial and extra-terrestrial sources, including supernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos, atmospheric neutrinos, solar neutrinos, as well as exotic searches such as nucleon decays, dark matter, sterile neutrinos, etc. We present the physics motivations and the anticipated performance of the JUNO detector for various proposed measurements. By detecting reactor antineutrinos from two power plan…
Precision measurements ofB[ψ(3686)→π+π−J/ψ]andB[J/ψ→l+l−]
Based on (106.41 +/- 0.86) x 10(6) psi(3686) events collected with the BESIII detector at the BEPCII collider, the branching fractions of psi(3686) -> pi(+)pi(-)J/psi, J/psi -> e(+)e(-), and J/psi -> mu(+)mu(-) are measured. We obtain B[psi(3686) -> pi(+)pi(-)J/psi] = (34.98 +/- 0.02 +/- 0.45)%, B[J/psi -> e(+)e(-)] = (5.983 +/- 0.007 +/- 0.037)%, and B[J/psi -> mu(+)mu(-)] = (5.973 +/- 0.0007 +/- 0.038)%. The measurement of B[psi(3686) -> pi(+)pi(-)J/psi] confirms the CLEO-c measurement, and is apparently larger than the others. The measured J/psi leptonic decay branching fractions agree with previous experiments within one standard deviation. These results lead to B[J/psi -> l(+)l(-)] = (…
Observation of the Dalitz decayη′→γe+e−
We report the first observation of the Dalitz decay eta' -> gamma e(+)e(-), based on a data sample of 1.31 billion J/psi events collected with the BESIII detector. The eta' mesons are produced via the J/psi -> gamma eta' decay process. The ratio (eta' -> gamma e(+)e(-))/Gamma (eta' -> gamma gamma) is measured to be (2.13 +/- 0.09(stat) +/- 0.07(sys)) x 10(-2). This corresponds to a branching fraction B(eta' -> gamma e(+)e(-)) = (4.69 +/- 0.20(stat) +/- 0.23(sys)) x 10(-4). The transition form factor is extracted and different expressions are compared to the measured dependence on the e(+)e(-) invariant mass. The results are consistent with the prediction of the vector meson dominance model.
Precision measurements of branching fractions forψ′→π0J/ψandηJ/ψ
We present a precision study of the psi' -> pi(0)J/Psi and eta J/Psi decay modes. The measurements are obtained using 106 x 10(6) psi' events accumulated with the BESIII detector at the BEPCII e(+)e(-) collider operating at a center-of-mass energy corresponding to the psi' mass. We obtain B(psi' -> pi(0)J/Psi) = (1.26 +/- 0.02(stat) +/- 0.03(syst)) x 10(-3) and B(psi' -> eta J/Psi) = (33.75 +/- 0.17(stat) +/- 0.86(syst)) x 10(-3). The branching fraction ratio R = B(psi'->pi(0)J/psi)/B(psi'->eta J/psi) is determined to be (3.74 +/- 0.06(stat) +/- 0.04(syst)) x 10(-2). The precision of these measurements of B(Psi' -> pi(0)J/Psi) and R represent a significant improvement over previously publis…