B. E. Berger

Bio: B. E. Berger is an academic researcher from Institute for the Physics and Mathematics of the Universe. The author has contributed to research in topics: Sterile neutrino & Neutrino oscillation. The author has an hindex of 1, co-authored 1 publications receiving 873 citations.

Search for Majorana Neutrinos Near the Inverted Mass Hierarchy Region with KamLAND-Zen.

Abstract: We present an improved search for neutrinoless double-beta (0νββ) decay of ^{136}Xe in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a significant reduction of the ^{110m}Ag contaminant identified in previous searches. Combining the results from the first and second phase, we obtain a lower limit for the 0νββ decay half-life of T_{1/2}^{0ν}>1.07×10^{26} yr at 90% C.L., an almost sixfold improvement over previous limits. Using commonly adopted nuclear matrix element calculations, the corresponding upper limits on the effective Majorana neutrino mass are in the range 61-165 meV. For the most optimistic nuclear matrix elements, this limit reaches the bottom of the quasidegenerate neutrino mass region.

Global analysis of three-flavour neutrino oscillations: synergies and tensions in the determination of θ 23 , δ CP , and the mass ordering

Abstract: We present the results of a global analysis of the neutrino oscillation data available as of fall 2018 in the framework of three massive mixed neutrinos with the goal at determining the ranges of allowed values for the six relevant parameters. We describe the complementarity and quantify the tensions among the results of the different data samples contributing to the determination of each parameter. We also show how those vary when combining our global likelihood with the χ2 map provided by Super-Kamiokande for their atmospheric neutrino data analysis in the same framework. The best fit of the analysis is for the normal mass ordering with inverted ordering being disfavoured with a Δχ2 = 4.7 (9.3) without (with) SK-atm. We find a preference for the second octant of θ23, disfavouring the first octant with Δχ2 = 4.4 (6.0) without (with) SK-atm. The best fit for the complex phase is δCP = 215° with CP conservation being allowed at Δχ2 = 1.5 (1.8). As a byproduct we quantify the correlated ranges for the laboratory observables sensitive to the absolute neutrino mass scale in beta decay, $$ {m}_{ u_e} $$ , and neutrino-less double beta decay, mee, and the total mass of the neutrinos, Σ, which is most relevant in Cosmology.

DARWIN: towards the ultimate dark matter detector

Abstract: DARk matter WImp search with liquid xenoN (DARWIN(2)) will be an experiment for the direct detection of dark matter using a multi-ton liquid xenon time projection chamber at its core. Its primary g ...

Global constraints on absolute neutrino masses and their ordering

Abstract: Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta ($0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$) decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to $O({10}^{\ensuremath{-}1})\text{ }\text{ }\mathrm{eV}$ in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis that includes the latest results from oscillation experiments, $0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of $\ensuremath{\sim}2\ensuremath{\sigma}$, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases. Detailed constraints are obtained via the ${\ensuremath{\chi}}^{2}$ method, by expanding the parameter space either around separate minima in NO and IO or around the absolute minimum in any ordering. Implications for upcoming oscillation and nonoscillation neutrino experiments, including $\ensuremath{\beta}$-decay searches, are also discussed.

2020 global reassessment of the neutrino oscillation picture

Abstract: We present an updated global fit of neutrino oscillation data in the simplest three-neutrino framework In the present study we include up-to-date analyses from a number of experiments Concerning the atmospheric and solar sectors, besides the data considered previously, we give updated analyses of IceCube DeepCore and Sudbury Neutrino Observatory data, respectively We have also included the latest electron antineutrino data collected by the Daya Bay and RENO reactor experiments, and the long-baseline T2K and NOνA measurements, as reported in the Neutrino 2020 conference All in all, these new analyses result in more accurate measurements of θ13, θ12, $$ \Delta {m}_{21}^2 $$ and $$ \left|\Delta {m}_{31}^2\right| $$ The best fit value for the atmospheric angle θ23 lies in the second octant, but first octant solutions remain allowed at ∼ 24σ Regarding CP violation measurements, the preferred value of δ we obtain is 108π (158π) for normal (inverted) neutrino mass ordering The global analysis still prefers normal neutrino mass ordering with 25σ statistical significance This preference is milder than the one found in previous global analyses These new results should be regarded as robust due to the agreement found between our Bayesian and frequentist approaches Taking into account only oscillation data, there is a weak/moderate preference for the normal neutrino mass ordering of 200σ While adding neutrinoless double beta decay from the latest Gerda, CUORE and KamLAND-Zen results barely modifies this picture, cosmological measurements raise the preference to 268σ within a conservative approach A more aggressive data set combination of cosmological observations leads to a similar preference for normal with respect to inverted mass ordering, namely 270σ This very same cosmological data set provides 2σ upper limits on the total neutrino mass corresponding to Σmν < 012 (015) eV in the normal (inverted) neutrino mass ordering scenario The bounds on the neutrino mixing parameters and masses presented in this up-to-date global fit analysis include all currently available neutrino physics inputs

Status and future of nuclear matrix elements for neutrinoless double-beta decay: a review.

Abstract: The nuclear matrix elements that govern the rate of neutrinoless double beta decay must be accurately calculated if experiments are to reach their full potential. Theorists have been working on the problem for a long time but have recently stepped up their efforts as ton-scale experiments have begun to look feasible. Here we review past and recent work on the matrix elements in a wide variety of nuclear models and discuss work that will be done in the near future. Ab initio nuclear-structure theory, which is developing rapidly, holds out hope of more accurate matrix elements with quantifiable error bars.