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Register a new userTowards a reconstruction of Supernova Neutrino Spectra in JUNO
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Added by
Cristina Martellini
Publication date
2019
fields
Physics
and research's language is
English
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Observation of supernovae (SN) through their neutrino emission is a fundamental point to understand both SN dynamics and neutrino physical properties. JUNO is a 20kton liquid scintillator detector, under construction in Jiangmen, China. The main aim of the experiment is to determine neutrino mass hierarchy by precisely measuring the energy spectrum of reactor electron antineutrinos. However due to its properties, JUNO has the capability of detecting a high statistics of SN events too. Existing data from SN neutrino consists only of 24 events coming from the SN 1987A,the detection of a SN burst in JUNO at $sim 10 kpc$ will yield $sim 5 x 10^{3}$ inverse beta decay (IBD) events from electron antineutrinos, about 1500 from proton elastic scattering (pES) above the threshold of 0.2 MeV, about 400 from electron elastic scattering (eES), plus several hundreds on other CC and NC interaction channels from all neutrino species.
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Measuring precise all-flavor neutrino information from a supernova is crucial for understanding the core-collapse process as well as neutrino properties. We apply a chi-squared analysis for different detector setups to explore determination of $ u_{e}$ spectral parameters. Using a long-term two-dimensional core-collapse simulation with three time varying spectral parameters, we generate mock data to examine the capabilities of the current Super-Kamiokande detector and compare the relative improvements that gadolinium, Hyper-Kamiokande, and DUNE would have. We show that in a realistic three spectral parameter framework, the addition of gadolinium to Super-Kamiokande allows for a qualitative improvement in $ u_e$ determination. Significant improvements will be made by Hyper-Kamiokande and DUNE, allowing for much more precise determination of $ u_e$ spectral parameters.
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 proposed 180 days data taking, the sensitivity to the dark bosons can reach $sim10^{-5}$ 95%C.L. for the optimized signal to background ratio for the electron coupling constant $it{g_X} $ through inverse Compton-like scattering. The background systematic uncertainty presents as the main limiting factor for the further sensitivity improvement. 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.
The energy spectrum of a neutrino beam in the few-GeV region is free of uncertainties from nuclear effects when reconstructed via neutrino-hydrogen interactions. On a multinuclear (hydrogen containing) target such interactions can be extracted using transverse kinematic imbalance. We discuss the prospects of this technique for current experiments.
We study the physics reach of the long-baseline oscillation analysis of the DUNE experiment when realistic simulations are used to estimate its neutrino energy reconstruction capabilities. Our studies indicate that significant improvements in energy resolution compared to what is customarily assumed are plausible. This improved energy resolution can increase the sensitivity to leptonic CP violation in two ways. On the one hand, the CP-violating term in the oscillation probability has a characteristic energy dependence that can be better reproduced. On the other hand, the second oscillation maximum, especially sensitive to $delta_{CP}$, is better reconstructed. These effects lead to a significant improvement in the fraction of values of $delta_{CP}$ for which a $5 sigma$ discovery of leptonic CP-violation would be possible. The precision of the $delta_{CP}$ measurement could also be greatly enhanced, with a reduction of the maximum uncertainties from $26^circ$ to $18^circ$ for a 300~MW$cdot$kt$cdot$yr exposure. We therefore believe that this potential gain in physics reach merits further investigations of the detector performance achievable in DUNE.
In the late stages of nuclear burning for massive stars ($M>8~M_{sun}$), the production of neutrino-antineutrino pairs through various processes becomes the dominant stellar cooling mechanism. As the star evolves, the energy of these neutrinos increases and in the days preceding the supernova a significant fraction of emitted electron anti-neutrinos exceeds the energy threshold for inverse beta decay on free hydrogen. This is the golden channel for liquid scintillator detectors because the coincidence signature allows for significant reductions in background signals. We find that the kiloton-scale liquid scintillator detector KamLAND can detect these pre-supernova neutrinos from a star with a mass of $25~M_{sun}$ at a distance less than 690~pc with 3$sigma$ significance before the supernova. This limit is dependent on the neutrino mass ordering and background levels. KamLAND takes data continuously and can provide a supernova alert to the community.
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