The The Scie Scientif ific I ic Impact mpact o of W Water- based Li Liquid Scintillator Hybrid De Detector ors R.Svoboda CPAD, 8 December, 2019
Development of Large Optical Detectors have ushered in a new era of Neutrino Physics Large size for cost, fast timing for background reduction, low threshold, reconfigurable as the field progressed R.Svoboda, CPAD 2019
Wa Water Cherenkov • Excellent Transparency • large size • Directionality Directionality • Particle ID • Potential for large Isotopic Loading Li Liquid Sci cintillator Super-K • High Light Yield • low threshold • good energy resolution Low threshold and • Can be radiologically very clean high energy resolution Could we make a hybrid detector? Borexino R.Svoboda, CPAD 2019
Why would you want a Hybrid Detector? • Cherenkov has directionality and kinetic energy, while scintillation carries information on the total deposited charge and PID • There is different information contained in the Cherenkov and scintillation light that can enable enhanced PID via the C/S ratio • Improved energy resolution via enhanced light yield • Detection of below Cherenkov threshold particles. E.g. stealth muons, kaons from proton decay, and low energy charged hadrons • Lower energy threshold due to addition of scintillation light R.Svoboda, CPAD 2019
How to Separate Cherenkov and Scintillation Photons? Timing Color Scintillation light has narrow bandwidth Cherenkov light comes early J.R.Alonso, et al Kaptanoglu, Luo, and Klein arXiv:1409.5864 JINST. 14 (2019) R.Svoboda, CPAD 2019
Advanced simulation New hybrid Novel and reconstruction target media photosensors Water-based Liquid Scintillator Super-K FitQun: J. Phys. Conf. Ser. 888 LAPPDs no. 1, (2017) (see talks by A.Lyashenko, H.Frisch, J.Xia, E.Angelico, E.Tiras) Dichroicon (see talk by J.Caravaca) (see talk by LENA 3D topological T.Kaptanoglu) Chroma optical reconstruction: JINST simulations - GPU 13 no. 07, (2018) R.Svoboda, CPAD 2019
(see talk by E.Tiras) - Gadolinium neutron tagging - LAPPD reconstruction - WbLS (planned) R.Svoboda, CPAD 2019
A series of workshops over last 4 years has led to a Theia : White Paper on the the physics potential of a Goddess of Light hybrid detector known as the Thei eia concept October 2016 March 2017 March 2016 April 2018 Theia International Interest Group (arXiv:1911.03501) December 2018 (to be submitted this week to Euro. Phys. J. C) R.Svoboda, CPAD 2019
(arXiv:1911.03501) 70m 18m T HEIA25 20m interior of Theia25 The White Paper considers two versions of the Theia concept, both assumed to be sited at the LBNF Theia25: 25 kTon (total) hybrid detector as the 4 th DUNE module Theia100: 100 kTon (total) hybrid detector as a future stand-alone experiment Theia100 R.Svoboda, CPAD 2019
Theia concept: a reconfigurable detector Theia would have a very broad science program based on the ability to upgrade the detector in incremental steps to “follow the science” This table shows a possible scenario with three phases of detector configurations (arXiv:1911.03501) R.Svoboda, CPAD 2019
Long Baseline Physics Old LBNE studies • In the last 10 years there based on SK-1 have been huge strides NC made in the analysis of water Cherenkov data by SK/T2K • >70% reduction in p 0 backgrounds current • ability to reconstruct multi- SK/T2K analysis track events so that more + other NC than 50% increase in signal in 2-3 GeV region + multi-track samples R.Svoboda, CPAD 2019
Long Baseline Physics CP Violation Sensitivity CP Violation Sensitivity • As a result, using the existing Super- 7 7 CP Violation Sensitivity K/T2K efficiencies and background Theia 70 kt Normal Ordering Theia 17 kt rejection, Theia100 (70 kTon fiducial) 6 6 7 years DUNE 10 kt (CDR) would have excellent CPV sensitivity 5 5 • Theia25 (17 kTon fiducial) would have 2 2 4 4 χ χ sensitivity comparable to one DUNE ∆ ∆ = = Lar module - appropriate for 4 th 3 3 σ σ module 2 2 • Possibility for additional 1 1 improvements using C/S information and fast timing needs to be explored 0 0 -1 -0.8 -0.6 -0.4 -0.2 -1 -0.8 -0.6 -0.4 -0.2 0 0 0.2 0.4 0.6 0.8 0.2 0.4 0.6 0.8 1 1 δ δ / / π π CP CP using DUNE CDR assumptions: 2% signal and 5% background uncertainty R.Svoboda, CPAD 2019
Diffuse SN Background LBNF is a very deep site (4300 mwe) far from nuclear reactors - reduction in spallation backgrounds - small reactor background Neutron tagging possible w/o gadolinium - assume 10% WbLS and 70% coverage C/S ratio before cuts - strong cut against NC events that can after cuts result in neutrons similar to inverse beta decay events Conclusion: even Theia25 could be large enough to make a 5 s discovery of the DSNB in less than 10 years Theia 100 kTon-year exposure R.Svoboda, CPAD 2019
SN Burst Neutrinos 100 kT WbLS @ 10 kpc Theia100(25) would see nearly 1000(250) Electron Scattering (ES) events Possibility of 7-Li loading for solar neutrinos would make Theia sensitive to n e CC events beyond just ES R.Svoboda, CPAD 2019
Solar Neutrinos • The CNO flux from the sun has never been measured directly and is critical to the resolution of the solar metallicity problem. A Theia detector could measure this using directionality in addition to scintillation using Electron Scattering (ES) events (assuming very high light collection - similar to JUNO) • Spectral upturn and Day/Night effect in 8-B can probe the energy region of the vacuum to matter transition • A Theia detector could also be loaded with 7-Li for enhanced CC detection R.Svoboda, CPAD 2019
Solar Neutrinos 90% PMT coverage, 5% WbLS, 0.6 MeV threshold, 25 o angular resolution, 250 kT-years Bonventre and Orebi Gann have explored the possibility of directional fitting in a WbLS detector of 50 kT (from Theia White Paper) Eur. Phys. J. C 78 (2018) 4a35, arXiv:1803.07109 Applied to a Theia detector, this would result in a definitive measurement of CNO R.Svoboda, CPAD 2019
Possibility of 7-Li loading: enhanced sensitivity to n e The ability to before ES cut make a solar direction cut to remove ES events results in an much enhanced capability 7-Li n e and other CC cross-sections. Note that 7-Li loading would be in WbLS after ES cut Note: 7-Li loading would also anable detecting n e CC in a SN burst R.Svoboda, CPAD 2019
Reactor and Geoneutrinos The reactor background at the LBNF is very low The flux of Geoneutrinos (26/kT-year)is comparable to the reactor flux (20/kT-year). A Theia detector would make a definitive measurement R.Svoboda, CPAD 2019
Neutrinoless Double Beta Decay 3 s discovery potential for proposed future experiments This shows results for Theia100 with 5% nat-Te an 8 meter radius inner vessel and 90% 3% enriched 136-Xe PMT coverage R.Svoboda, CPAD 2019
What’s Next? • Need to now make a hit-level reconstruction analysis for the LBL physics sensitivity studies that will go beyond simply taking existing Super-K efficiencies and resolutions. How can the fast timing and hybrid signal be exploited? A multi-university consortium is forming to propose a two-year program of detailed detector and physics simulations. • Need to pursue the further development of WbLS to determine stability, attenuation and scattering, effects on materials, and how to achieve required optical and radiological purity. There is a separate university/lab consortium that has formed to propose a coherent R&D program • Photosensor development (e.g. LAPPDs and Dichroicons) is proceeding under the current program, and should have continued support. R.Svoboda, CPAD 2019
Summary • The development of hybrid target materials, ultra-fast and color sensitive photosensors, and advanced imaging techniques have led to the maturing of the concept of a modern, large scale optical detector • Such a detector would be reconfigurable and able to adapt to new scientific discoveries and directions. • There are many talks at this workshop on technology relevant to a Theia concept detector - ranging from novel photosensors, to ultra- fast beam timing ideas, to new types of scintillators. There is a lot of community interest and lots of opportunity for bold, new thinking • The next Theia international meeting will be in Spring 2020 - think about attending! R.Svoboda, CPAD 2019
R.Svoboda, CPAD 2019
R.Svoboda, CPAD 2019
R.Svoboda, CPAD 2019
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