Atmospheric Neutrino Studies at Hyper-K Advanced Workshop on - PowerPoint PPT Presentation

Atmospheric Neutrino Studies at Hyper-K Advanced Workshop on Physics of Atmospheric Neutrinos - PANE 2018 Gianfranca De Rosa on behalf of the Hyper-Kamiokande Coll.

Outline • Hyper-Kamiokande • Atmospheric neutrino studies • Tokai-to-Hyper-Kamiokande (T2HK) • Atmospheric neutrinos and combination with beam neutrinos • Second tank: staging and Korean detector options • Summary Gianfranca De Rosa, Naples U. and INFN - 2 PANE 2018

Hyper-Kamiokande: overview Hyper-Kamiokande is a multi- purpose Water-Cherenkov detector with a variety of scientific goals:  Neutrino oscillations (atmospheric, accelerator and solar);  Neutrino astrophysics;  Proton decay;  Non-standard physics. Atmospheric n Supernova n Solar n Accelerator n Gianfranca De Rosa, Naples U. and INFN - 3 PANE 2018

Hyper-Kamiokande design HK builds on the successful strategies used to study neutrino oscillations in Super-Kamiokande, K2K and T2K with:  Larger detector for increased statistics  Improved photo-sensors for better efficiency  Higher intensity beam and updated/new near detector for accelerator neutrino part 2 tanks with staging construction.  Cylindrical tank: Φ 74 m and H 60 m Planned time line:  Total and fiducial volumes (for one Project approval 2019 tank): 0.26 and 0.19Mtons, resp. Experiment 2026 (1 st tank)  Photo-cathode coverage: 40%. 40,000 ID Proposals for a second tank PMTs and 6700 OD PMTs per tank. Gianfranca De Rosa, Naples U. and INFN - 4 PANE 2018

Recent R&D results on PMTs Requirements Wide dynamic range, High time&charge resolutions, high detection efficiency...  nsec time resolution 40% low background 187 kton photo- Clear photon counting, Fiducial coverage 60 m High rate tolerance Mass 258 kton About 7,000 PMTs for Outer Veto × 2 tanks Detector New high-QE 50 cm Box&Line PMT ID: Planned 40,000 photosensors × 2 high pressure bearing for 60 m depth Baseline option: 20’’ PMTs × 2 high detection efficiency Alternative option: and half time&charge resolutions 50% 20’’ PMTs and 50% mPMTs compared to Super-K PMT (up to  40m depth) 5

50 cm Photo-Detectors First 20-inch (50 cm) Photomultiplier Tube (PMT) For other experiments Hamamatsu R1449 (Venetian blind dynode) 42 cm (17”) Box&Line PMT R7250 (1983-1996) Supernova ν (Box&Line dynode) observation! with 50 cm bulb 1k PMTs of R3600 / 3 kton water R3600 (Venetian blind dynode, improved) 50 cm MCP PMT By NNVC, IHEP (1996- ) ν oscillation 11k PMTs discovery! / 50 kton water Recently developed in China 50 cm Box&Line PMT 50 cm Hybrid Photo-Detector (HPD) R12860-HQE R12850-HQE (Avalanche diode) (Box&Line dynode) Developed Under development → Photo -detector → Possible further in Hyper-K improvement of baseline design Hyper-K 6

fi fi fi fi カウントグラフ（ 軸） 50 cm Photo-Detectors 各 ポ ジ シ ョ ン で の カ ウ ン ト を グ ラ フ 化 （標 準 球 の カ ウ ン ト を 同 じ に し た 場 合 ） Total Detection Efficiency of 1 PE High Quantum Efficiency (QE) Measured at Hamamatsu by point source injection 40 Measured Relative single photoelectron hit efficiency Box&Line PMT HPD → 36% Measured Quantum Efficiency [%] 35 2 × 2 30 Box&Line PMTs 25 → 30% 20 1 15 Super-K 10 22% Super-K at peak 5 (-2016yr) 0 0 300 350 400 450 500 550 600 650 700 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 Wavelength [nm] Position angle [degree] Collection Efficiency (CE) こ の デ ー タ の カ ウ ン ト 値 は 入 射 光 子 数 が 一 定 に な る 様 補 正 し て あ る が 、 と の 固 体 差 が 含 ま れ て い る 。 Relative comparison of single PE と で は 、 同 一 光 子 数 を 入 射 し た と 仮 定 し た 場 合 の カ ウ ン ト 値 に 歴 然 と 差 が あ る こ と が 分 か る 。 By simulation In 46cmΦ (50cmΦ) counting compared with SK PMT ◦ ± by a uniform light injection • Super-K 67% (61%) Box&Line PMT : 1.91 of SK PMT • Box&Line PMT 95% (85%) HPD : 1.76 of SK PMT (2ch 20mm ΦAD) • HPD 97% (80%) (1ch 20mm ΦAD) (Low due to higher threshold for 1 PE) Detection efficiency was doubled in both new photo-detectors 7

Multi-PMT Option for Hyper-K Photodetectors and Based on KM3NeT electronics arranged optical module OD ID inside a pressure resistent vessel  (Almost) uniform coverage by PMTs  Directionality  Several manifacturers ” Increased granularity enhanced event reconstruction, in particular for multi- ring events 8

Atmospheric neutrinos Now that  13 is known to be quite large, there are several open questions remaining, including ordering of the neutrino masses  octant of the atmospheric mixing angle  whether or not neutrino oscillations violate CP  Atmospheric neutrinos are a good tool for studying L/E-style oscillations in a broad sense  With larger statistics, they can also provide information on sub- leading effects Matter effect gives improved sensitivity  Mass hierarchy  Asymmetry between neutrinos and antineutrinos  size of  13 and  CP  Magnitude of resonance effect  Octant of  23  Appearance and disappearance interplay Gianfranca De Rosa, Naples U. and 9 INFN - PANE 2018

Atmospheric neutrinos • Matter-induced parametric oscillations in the energy range 2- 10 GeV lead to significant enhancement of either the n μ  n e or the n   n e appearance probability for upward-going neutrinos depending upon the mass hierarchy. For the normal (inverted) hierarchy neutrino (antinuetrino) oscillations are enhanced The separation of atmospheric neutrino data into neutrino- • like and antineutrino like subsets with neutron tagging can be used to extract the hierarchy signal • Improved photon collection and increased statistic is expected to improve the sensitivity of atmospheric neutrinos Gianfranca De Rosa, Naples U. and INFN - 10 PANE 2018

Atmospheric neutrinos Using atmospheric neutrinos alone:  Determine mass hierarchy at 3σ when sin 2  23 > 0.53  Some sensitivity to θ 23 octant  Sensitivities depend on true θ 23 value Mass hierarchy determination Octant determination NH IH Sensitivity studies based on SK analysis Width of the bands shows the Scaled SK MC • (see talk by C. Bronner) uncertainty from δ CP • 10 years running with one 187 kt fv detector • No improvement of Super-K systematics assumed • True mass hierarchy not assumed to be known

Tokai-to-Hyper-Kamiokande (T2HK) long baseline neutrino oscillation experiment  Upgraded facility at J-PARC will deliver a muon (anti-)neutrino beam towards Hyper-K ( ≈ 0.75MW, 1.56 × 10 22 protons on target with 30 GeV proton beam);  2.5 o off-axis narrow-band beam:  Suppresses high energy background;  E ν ≈ 0.6 GeV peak at oscillation maximum;  Pure ν μ beam with < 1% n e contamination. new power upgrade plan of J- PARC → we expect ~>900kW by 2020, and ~1.3MW as early as 2026 Gianfranca De Rosa, Naples U. and INFN - 12 PANE 2018

Tokai-to-Hyper-Kamiokande (T2HK) Focus: measurements Intermediate n production of |  m 2 32 |, sin 2  23 , Near detector sin 2  13 and  CP detectors n  n    JPARC On-axis Far detector ) beamline Spans 1 to 2.5° Off-axis 4° off-axis Hyper-Kamiokande | | | // | 0 280 m 700 m -2 km 295 km E61 Updated ND and new ID to reduce systematics

T2HK: Sensitivity to atmospheric parameters After 10 years: A joint fit of n μ and n e samples to  Measure Δ m 2 32 with 1.4x10 -5 ev 2 precision precisely measure sin 2  23 and  m 2 32  Measure sin 2 θ 23 with precision 0.006 to 0.017  Some ability to determine octant of θ 23 Expected significance for wrong octant rejection, 90% CL allowed regions for the true values of sin 2  23 = 0.5 and  m 2 with reactor constraint,vs true sin 2  23 32 = 2.4 × 10 −3 eV 2 Reactor constraint on sin 2 2  13 = 0.1 ± 0.005 Gianfranca De Rosa, Naples U. and INFN - 14 PANE 2018

T2HK: Sensitivity to mass hierarchy Atmospheric+beam neutrinos Atmospheric neutrinos Beam neutrinos  Sensitive to mass hierarchy through  Very limited sensitivity to MH matter induced resonance  Good precision for θ 23 and |Δm 2 32 |  Size of the effect depends of θ 23 measurements  Limited precision for θ 23 and | Δm 2 32 | Combining the two:  > 3σ ability to reject wrong MH  5σ for larger values of sin 2 θ 23 True Atmospheric Atmospheric sin 2 θ 23 only +beam Atm+beam True Normal Atm+beam True Inverted 2.2 σ 3.8 σ 0.4 0.6 4.9 σ 6.2 σ Gianfranca De Rosa, Naples U. and INFN - 15 PANE 2018

T2HK: octant resolution sensitivity Atmospheric+beam neutrinos The ability to resolve the  23 octant improves with the combination Atmospheric neutrinos alone can resolve the octant at 3  if |  23 − 45| > 4° With combined analysis it can be resolved when this difference is only 2.3° True Atmospheric Atmospheric sin 2 θ 23 only +beam assuming a normal hierarchy, Δm 2 32 = 2.5 × 10−3eV 2 , sin 2 θ 23 = 0.0219, and the value of CP that minimizes the sensitivity 0.4 5 2.2 σ 6.2 σ 0. 55 1.6 σ 3.6 σ Gianfranca De Rosa, Naples U. and INFN - 16 PANE 2018