JUNO Sensitivity to Invisible Decay Modes of Neutrons

We explore the bound neutrons decay into invisible particles (e.g., $n\rightarrow 3 \nu$ or $nn \rightarrow 2 \nu$) in the JUNO liquid scintillator detector. The invisible decay includes two decay modes: $n \rightarrow { inv}$ and $nn \rightarrow { inv}$. The invisible decays of $s$-shell neutrons in $^{12}{\rm C}$ 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 $\tau/B( n \rightarrow { inv} ) > 5.0 \times 10^{31} \, {\rm yr}$ and $\tau/B( nn \rightarrow { inv} ) > 1.4 \times 10^{32} \, {\rm yr}$.Comment: 28 pages, 7 figures, 4 table

Updated Geoneutrino Measurement with the Borexino Detector

Geoneutrinos are electron antineutrinos and neutrinos emitted in the radioactive decays from theEarth’s interior. Due to the intrinsic dependence of the geoneutrino flux and the heat producedin the radioactive decays, geoneutrinos contribute uniquely to our knowledge about the Earth.The main goal of neutrino geophysics is to use the obtained geoneutrino signals in estimating theabundance and distribution of the heat producing elements such as 238U, 235U, 232Th and 40K.The radiogenic heat contribution, especially the mantle contribution to the total surface heat fluxand the nature of the mantle still remain as open questions. The combination of the total geoneutrino flux (≈106cm−2s−1) and the weak interaction cross section (≈10−42 cm−2s−1) lead to hugestatistical uncertainties in the current measurements. This has made the study of geoneutrinosquite challenging and so far, only two detectors, namely KamLAND and Borexino, have measuredgeoneutrinos.The Borexino Detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy firstobserved geoneutrinos in 2010 followed by two measurements in 2013 and 2015. The latest geoneutrino measurement included a 5.9σ evidence of geoneutrinos and the rejection of the null hypothesisof the mantle signal at a 98% C.L. The uncertainty in the latest published result is 26.2%. Thiswork concentrates on the further improvement of the geoneutrino measurement. The increasedstatistics and the optimised selection cuts used for the analysis have made it possible to reduce theuncertainty to 20.6%. An uncertainty of less than 20% can be achieved by the further optimisationof the selection cuts and needs more investigation

Analysis Strategies for the Updated Geoneutrino Measurement with Borexino

Borexino, is one of the two detectors that has measured geoneutrinos, particles that carry direct information about the deep Earth. These electron antineutrinos can help us unravel details of the mantle, obtain the radiogenic heat contribution to Earth’s surface heat flux, and also give us limits to the hypothetical georeactor.Geoneutrinos are measured using the Inverse Beta Decay channel in Borexino and the latest published result in 2015 has an uncertainty of 26.2%. Thanks to the updated statistics and the various optimised selection cuts, it has been possible to reduce the uncertainty by a substantial amount. This poster will cover the details of the key improvements such as increased fiducial volume analysis, improved veto for cosmogenics, extended energy and coincidence time window, as well as a more efficient α/β discrimination technique. The highlights of the results obtained from the update will also be presented

Spectroscopy of geoneutrinos with Borexino

Abstract Borexino is a 280-ton liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso (LNGS), Italy and is one of the two detectors that has measured geoneutrinos so far. The unprecedented radio-purity of the scintillator, the shielding with highly purified water, and the placement of the detector at 3800 m w.e. depth have resulted in very low background levels, making Borexino an excellent apparatus for geoneutrino measurements. This article will summarize the recent geoneutrino analysis and results with Borexino, from the period December 2007 to April 2019. The updated statistics and the optimized analysis techniques such as an increased fiducial volume and sophisticated cosmogenic vetoes, have led to more than a two-fold increase in exposure when compared to the previous measurement in 2015, resulting in a significant improvement in the precision. In addition, Borexino has also been able to reject the null hypothesis of the mantle geoneutrino signal with 99% C.L., for the first time, by exploiting the extensive knowledge of the crust surrounding the detector. This article will also include other geological interpretations of the obtained results such as the calculation of the radiogenic heat and the comparison of the results to various predictions. Additionally, upper limits for a hypothetical georeactor that might be present at different locations inside the Earth will also be discussed.</jats:p