A new way to determine the neutrino mass hierarchy at reactors

The determination of the neutrino mass ordering is currently pursued by several experiments and proposals. A very challenging one is its evaluation from reactor experiments based on the tiny interference effect between the $\Delta m^2_{31}$ and $\Delta m^2_{32}$ oscillations. Current analyses require several years of data taking and an extreme energy resolution to achieve anyhow less than 5 $\sigma$. Referring to the JUNO experimental conditions we developed a completely new technique that would provide a robust 5 $\sigma$ measurement in less than six years of running. The two orderings could be discriminated at the price of allowing for two different values of $\Delta m^2_{31}$. This degeneracy on $\Delta m^2_{31}$ (around $12\times 10^{-5}$ eV$^2$) can however be measured at an unprecedented accuracy of much less than 1\%, i.e. $10^{-5}$ eV$^2$, within the same analysis. Analogies with the usual $\chi^2$ analysis, where the $\Delta m^2_{31}$ degeneracy is much more important, are discussed. Evaluation and inclusion of systematic errors and backgrounds have been performed, the most relevant among them being the addition of the two remote reactor plants 250 km away. Baselines of each contributing reactor core and its spatial resolution have been taken into account. Possible results after two years of running and the foreseen initially-reduced available reactor power have been studied, too. These results confirm the very positive perspectives for JUNO to determine the mass ordering in a vacuum-oscillation dominated region.Comment: 37 pages, 22 figures, in this version added one more appendix about Chi^2, formal foundation of F as optimal estimator, submitted to JHE

Sinteza i biološko djelovanje novih 1-benzil i 1-benzoil 3-heterocikličkih derivata indola

Starting from 1-benzyl- (2a) and 1-benzoyl-3-bromoacetyl indoles (2b) new heterocyclic, 2-thioxoimidazolidine (4a,b), imidazolidine-2,4-dione (5a,b), pyrano(2,3-d)imidazole (8a,b and 9a,b), 2-substituted quinoxaline (11a,b–17a,b) and triazolo(4,3-a)quinoxaline derivatives (18a,b and 19a,b) were synthesized and evaluated for their antimicrobial and anticancer activities. Antimicrobial activity screening performed with concentrations of 0.88, 0.44 and 0.22 g mm2 showed that 3-(1-substituted indol-3-yl)quinoxalin-2(1H)ones (11a,b) and 2-(4-methyl piperazin-1-yl)-3-(1-substituted indol-3-yl) quinoxalines (15a,b) were the most active of all the tested compounds towards P. aeruginosa, B. cereus and S. aureus compared to the reference drugs cefotaxime and piperacillin, while 2-chloro-3-(1-substituted indol-3-yl)quinoxalines (12a,b) were the most active against C. albicans compared to the reference drug nystatin. On the other hand, 2-chloro-3-(1-benzyl indol-3-yl) quinoxaline (12a) display potent efficacy against ovarian cancer xenografts in nude mice with tumor growth suppression of 100 0.3 %.U radu je opisana sinteza, antimikrobno i antitumorsko djelovanje heterocikličkih derivata indola. Polazeći iz 1-benzil- i 1-benzoil-3-bromacetil indola (2a i 2b) sintetizirani su novi heterociklički spojevi 2-tioksoimidazolidini (4a,b), imidazolidin-2,4-dioni (5a,b), pirano(2,3-d)imidazoli (8a,b i 9a,b), 2-supstituirani kinoksalini (11a,b–17a,b) i triazolo(4,3-a)kinoksalini (18a,b i 19a,b). Sintetizirani spojevi testirani su na antimikrobno i antitumorsko djelovanje. Ispitivanje antimikrobnog djelovanja provedeno je s koncentracijama otopina 0,88, 0,44 i 0,22 g mm2 i uspoređeno s referentnim lijekovima cefotaksimom i piperacilinom. Rezultati pokazuju da su 3-(1-supstituirani indol-3-il)kinoksalin-2(1H)oni (11a,b) i 2-(4-metil piperazin-1-il)-3-(1-supstituirani indol-3-il) kinoksalini (15a,b) najaktivniji spojevi na sojeve P. aeruginosa, B. cereus i S. aureus, dok su 2-klor-3-(1-supstituirani indol-3-il)kinoksalini (12a,b) najaktivniji na C. albicans (usporedba s nistatinom). Osim toga, 2-klor-3-(1-benzil indol-3-il) kinoksalin (12a) pokazuje veliku učinkovitost na tumore ovarija miševa (supresija rasta tumora 100 0,3 %)

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

A new way to determine the neutrino mass hierarchy at reactors

The neutrino mass ordering is one of the fundamental characteristics of the reference 3-neutrino mixing scheme that still remains undetermined experimentally at present. Some of basic neutrino physics observables, which are planned to be measured in currently running and/or upcoming neutrino experiments, depend critically on the neutrino mass ordering. The Neutrino Mass Hierarchy Determination ( MHD) is one of the main goals of the major current and future neutrino experiments. MHD corresponds to the sign of the so called atmospheric neutrino mass, |Delta(m^2_atm)|. The medium baselines reactor anti-neutrino experiments are designed to determine the neutrino mass hierarchy without exploring the matter effect that is used in long baseline accelerator and atmospheric neutrino experiments. The strategy of mass hierarchy study, in medium baselines reactor experiments, can be based on the study of the neutrino vacuum oscillations. A technique was developed, referring to the interference of the two different oscillation frequencies driven by Delta(m^2_31) and Delta(m^2_23), which at first order correspond to Delta(m^2_atm) separated by the much smaller solar neutrino mass, Delta(m^2_sol). Advances in statistical analysis techniques may play a decisive role in the discovery reach at neutrino physics experiments. The statistical analysis for neutrino mass ordering usually proceeds from the standard method based on Delta(Chi^2). This method shows some draw-backs and concerns, together with a debatable strategy. The issues of the standard method on MHD for the neutrino reactor experiments are explained. As a result, a new alternative statistical method was invented. The new method of determining the neutrino mass ordering in medium baseline experiments with reactor anti-neutrino is based on a bi-dimensional statistical estimator. Referring to the JUNO experimental conditions we developed a completely new technique that would provide a robust 5 measurement in less than six years of running. The two orderings could be discriminated at the price of allowing for two different degenerated values of Delta(m^2_atm). This degeneracy on Delta(m^2_atm) (around 12*10^-5 eV^2) can however be tackled at an unprecedented accuracy of much less than 1%, i.e. 10^-5 eV^2, within the same analysis. The sensitivity using the new estimator, F_MO, was obtained assuming that the |Delta(m^2_atm)|, identified as the mass difference between the lightest neutrino mass and the heaviest one, be unique for both hypotheses NH and IH. We will discuss the subtleties of such assumption. On the other hand, also the standard JUNO test statistic depends on some strong assumptions. There are two kinds of sensitivity studies performed in the dissertation. One is that coming from the standard method, a single dimensional (1D) estimator Delta(Chi^2); the other one is obtained using the new alternative method via the bi-dimensional estimator F_MO. The sensitivity is obtained by taking into account the reactor cores’ distribution uncertainty, Daya Bay and Huizhou nuclear power plants contributions, the spectrum shape uncertainty and the detector-related uncertainties, including the energy non-linear response of the detector. The background systematics, especially ^9Li, have minor impact on the sensitivity. Possible results after two, four and six years of running and the foreseen initially-reduced available reactor power have been studied, as well. F_MO estimator gives confidence to reject the false mass hierarchy at more than 5 sigma. These results confirm the very positive perspectives for JUNO to determine the mass ordering in a vacuum oscillation dominated regime if the proper statistical analysis is used

Charge reconstruction in large-area photomultipliers

Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single PMT in a few tens/hundreds of nanoseconds, resulting in several photoelectrons (PEs) to pile-up at the PMT anode. In such scenario, the signal generated by each PE is entangled to the others, and an accurate PMT charge reconstruction becomes challenging. This manuscript describes an experimental method able to address the PMT charge reconstruction in the case of large PE pile-up, providing an unbiased charge estimator at the permille level up to 15 detected PEs. The method is based on a signal filtering technique (Wiener filter) which suppresses the noise due to both PMT and readout electronics, and on a Fourier-based deconvolution able to minimize the influence of signal distortions ---such as an overshoot. The analysis of simulated PMT waveforms shows that the slope of a linear regression modeling the relation between reconstructed and true charge values improves from $0.769 \pm 0.001$ (without deconvolution) to $0.989 \pm 0.001$ (with deconvolution), where unitary slope implies perfect reconstruction. A C++ implementation of the charge reconstruction algorithm is available online at http://www.fe.infn.it/CRA

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022