Hyper-Kamiokande
Hyper-Kamiokande (also called Hyper-K or HK) is a
The Hyper-Kamiokande experiment facility will be located in two places:
- The neutrino beam will be produced in the accelerator complex Ibaraki prefecture, on the east coast of Japan.[3]: 31
- The main detector, also called Hyper-Kamiokande (HK), is being constructed under the peak of Nijuugo Mountain in Hida city, Gifu Prefecture, in the Japanese Alps (36°21′20.105″N 137°18′49.137″E / 36.35558472°N 137.31364917°E[3]: 56 ). The HK detector will be used for proton decay searches, studies of neutrinos from natural sources and will serve as a far detector for the measurement of the oscillations of an accelerator neutrino beam at the distance corresponding to the first oscillation maximum.[3]: 53–56 [5]
Physics program
Accelerator and atmospheric neutrino oscillations
ν
e,
ν
μ,
ν
τ
- three mixing angles (θ12, θ23 and θ13) governing the mixing between mass and flavour states,
- two mass squared differences (∆m221 and ∆m232, where ∆m2ij = m2i – m2j)
- one phase (δCP) responsible for the matter-antimatter asymmetry (CP symmetry violation) in neutrino oscillations,
and two parameters which are chosen for a particular experiment:
- neutrino energy
- baseline – the distance travelled by neutrinos at which oscillations are measured.[6]: 285–311 [3]: 20–23
Continuing studies done by the T2K experiment, the HK far detector will measure the energy spectra of electron and muon neutrinos in the beam (produced at J-PARC as an almost pure muon neutrino beam) and compare it with the expectation in case of no oscillations, which is initially calculated based on neutrino flux and interaction models and improved by measurements performed by the near and intermediate detectors. For the HK/T2K neutrino beam peak energy (600 MeV) and the J-PARC – HK/SK detector distance (295 km), this corresponds to the first oscillation maximum, for oscillations driven by ∆m232. The J-PARC neutrino beam will run in both neutrino- and antineutrino-enhanced modes separately, meaning that neutrino measurements in each beam mode will provide information about muon (anti)neutrino survival probability P
ν
μ →
ν
μ, P
ν
μ →
ν
μ, and electron (anti)neutrino appearance probability P
ν
μ →
ν
e, P
ν
μ →
ν
e , where Pνα → Pνβ is the probability that a neutrino originally of flavour α will be observed later as having flavour β.[3]: 202–224
Comparison of the appearance probabilities for neutrinos and antineutrinos (P
ν
μ →
ν
e versus P
ν
μ →
ν
e) allows measurement of the δCP phase. δCP ranges from −π to +π (from −180° to +180°), and 0 and ±π correspond to CP symmetry conservation. After 10 years of data taking, HK is expected to confirm at the 5σ
In order to determine the neutrino mass ordering (whether the ν3 mass eigenstate is lighter or heavier than both ν1 and ν2), or equivalently the unknown sign of the ∆m232 parameter, neutrino oscillations must be observed in matter. With HK beam neutrinos (295 km, 600 MeV), the matter effect is small. In addition to beam neutrinos, the HK experiment studies atmospheric neutrinos, created by cosmic rays colliding with the Earth's atmosphere, producing neutrinos and other byproducts. These neutrinos are produced at all points on the globe, meaning that HK has access to neutrinos that have travelled through a wide range of distances through matter (from a few hundred metres to the Earth's diameter). These samples of neutrinos can be used to determine the neutrino mass ordering.[3]: 225–237
Ultimately, a combined beam neutrino and atmospheric neutrino analysis will provide the most sensitivity to the oscillation parameters δCP, |∆m232|, sgn ∆m232, θ23 and θ13.[3]: 228–233
Neutrino Astronomy and Geoneutrinos
Neutrinos cumulatively produced by supernova explosions throughout the history of the universe are called supernova relic neutrinos (SRN) or diffuse supernova neutrino background (DSNB) and they carry information about star formation history. Because of a low flux (few tens/cm2/sec.), they have not yet been discovered. With ten years of data taking, HK is expected to detect about 40 SRN events in the energy range 16–30 MeV.[3]: 276–280 [8]
For the solar
ν
e's, the HK experiment goals are:
- Search for a day-night asymmetry in the neutrino flux – resulting from different distances travelled in matter (during the night neutrinos additionally cross the Earth before entering the detector) and thus the different oscillation probabilities caused by the matter effect.[3]: 238–244
- Measurement of the
ν
e survival probability for neutrino energies between 2 and 7 MeV – i.e. between regions dominated by oscillations in vacuum and oscillations in matter, respectively – which is sensitive to new physics models, like sterile neutrinos or non-standard interactions.[3]: 238–244 [9] - The first observation of neutrinos from the hep channel: predicted by the standard solar model.[3]: 238–244
- Comparison of the neutrino flux with the solar activity (e.g. the 11-year solar cycle).[10]
Proton Decay
The
. [11]After ten years of data taking, (in case no decay will be observed) HK is expected to increase the lower limit of the proton
p+
→
e+
+
π0
) and from 0.7x1034 to 2.0x1034 years for the
p+
→
ν
+
K+
channel.[3]
Dark Matter
: 281–286Experiment Description
The Hyper-Kamiokande experiment consists of an accelerator neutrino beamline, a set of near detectors, the intermediate detector and the far detector (also called Hyper-Kamiokande). The far detector by itself will be used for proton decay searches and studies of neutrinos from natural sources. All the above elements will serve for the accelerator neutrino oscillation studies. Before launching the HK experiment, the T2K experiment will finish data taking and HK will take over its neutrino beamline and set of near detectors, while the intermediate and the far detectors have to be constructed anew.[13]
Neutrino Beamline
Near Detectors
Intermediate Water Cherenkov Detector
The Intermediate Water Cherenkov Detector (IWCD) will be located at a distance of around 750 metres (2,460 ft) from the neutrino production place. It will be a cylinder filled with water of 10 metres (33 ft) diameter and 50 metres (160 ft) height with a 10 metres (33 ft) tall structure instrumented with around 400 multi-PMT modules (mPMTs), each consisting of nineteen 8 centimetres (3.1 in) diameter
Hyper-Kamiokande Far Detector
The Hyper-Kamiokande detector will be built 650 metres (2,130 ft) under the peak of Nijuugo Mountain in the Tochibora mine, 8 kilometres (5.0 mi) south from the Super-Kamiokande (SK) detector. Both detectors will be at the same off-axis angle (2.5°) to the neutrino beam centre and at the same distance (295 kilometres (183 mi)) from the beam production place in J-PARC.[note 2][3]: 35 [18]
HK will be a
HK detector construction began in 2020 and the start of data collection is expected in 2027.[3][4][13]: 24 Studies have also been undertaken on the feasibility and physics benefits of building a second, identical water-Cherenkov tank in South Korea around 1100 km from J-PARC, which would be operational 6 years after the first tank.[5][20]
History and schedule
A history of large water Cherenkov detectors in Japan, and long-baseline neutrino oscillation experiments associated with them, excluding HK:
- 1983-1996: Kamiokande (Kamioka Nucleon Decay Experiment), which main goal was proton decay searches (the Nobel Prize in Physics 2002 for Masatoshi Koshiba) – the predecessor of Super-Kamiokande[1]
- 1996–present: Super-Kamiokande experiment – the predecessor of the Hyper-Kamiokande experiment, studying neutrinos from natural sources and searching for proton decay (the Nobel Prize in Physics 2015 for Takaaki Kajita)[1]
- 1999–2004: K2K experiment – the predecessor of the T2K experiment
- 2010–present: T2K experiment – the predecessor of the Hyper-Kamiokande experiment, studying accelerator neutrino oscillations
A history of the Hyper-Kamiokande experiment:
- September 1999: First ideas of the new experiment presented[21]
- 2000: The name "Hyper-Kamiokande" used for the first time[22]
- September 2011: Submitting LOI[23]
- January 2015: MoU for cooperation in the Hyper-Kamiokande project signed by two host institutions: ICRR and KEK. Formation of the Hyper-Kamiokande proto-collaboration[24][25]
- May 2018: Hyper-Kamiokande Design Report[3]
- September 2018: Seed funding from MEXT allocated in 2019[26]
- February 2020: The project officially approved by the Japanese Diet[4]
- June 2020: Formation of the Hyper-Kamiokande collaboration
- May 2021: Start of the HK detector access tunnel excavation[27]
- 2021: Beginning of the photomultiplier tubes mass production[28]
- February 2022: Completion of the access tunnel construction[29]
- October 2023: Completion of the HK detector main cavern dome section[30]
- 2027: The expected beginning of data-taking[4]
Notes
- ^ The average energy of neutrinos decreases with the deviation from the beam axis.
- ^ The Super-Kamiokande detector serves as a far detector for the neutrino oscillation analysis by the T2K experiment. However, Super-Kamiokande is also a separate experiment in the matter of proton decay searches and studies of neutrinos from natural sources.
- ^ Veto is part of a detector where no activity should be registered to accept an event. Such a requirement allows constraining the number of background events in a selected sample.
See also
Bibliography
- Normile, D (2015). "Particle physics. Japanese neutrino physicists think really big". Science. 347 (6222): 598. PMID 25657225.
References
- ^ a b c "Hyper-Kamiokande website: Overview".
- ^ "Hyper-Kamiokande website: Collaboration Institutes".
- ^ arXiv:1805.04163 [physics.ins-det].
- ^ a b c d "Kamioka Observatory website: The Hyper-Kamiokande project is officially approved". Kamioka Observatory ICRR, The University of Tokyo. 12 February 2018.
- ^ .
- hdl:11585/900713.
- .
- .
- S2CID 254115998.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - ^ "Hyper-Kamiokande website: Cosmic Neutrino Observation: Solar neutrinos".
- ^ Mine, Shunichi (2023). "Nucleon decay: theory and experimental overview". Zenodo. .
- arXiv:1311.5285.
- ^ a b Vilela, Cristovao (September 5–10, 2021). "The status of T2K and Hyper-Kamiokande experiments". PANIC 2021 Conference. Archived from the original on 2021-09-29. Retrieved 2021-09-29.
- arXiv:1412.3086 [physics.ins-det].
- ^ nuPRISM Collaboration (7 July 2016). "Proposal for the NuPRISM Experiment in the J-PARC Neutrino Beamline" (PDF). Archived (PDF) from the original on 2 December 2020. Retrieved 1 April 2020.
- ^ Mark Hartz (2020-07-29). "Near Detectors for the Hyper-K Neutrino Experiment". 40th International Conference on High Energy Physics (ICHEP 2020).
- ^ a b Umut Kose (on behalf of the Hyper-Kamiokande Collaboration) (2023-12-07). "The Hyper-Kamiokande Experiment: Status and Prospect". The 17th International Workshop on Tau Lepton Physics (TAU2023). Retrieved 2024-02-08.
- ^ a b "Hyper-Kamiokande website: Hyper-Kamiokande Detector".
- .
- .
- .
- ^ Nakamura, K. (2000). "HYPER-KAMIOKANDE: A next generation water Cherenkov detector for a nucleon decay experiment". Part of Neutrino Oscillations and Their Origin. Proceedings, 1st Workshop, Fujiyoshida, Japan, February 11–13: 359–363.
- ].
- ^ "Hyper-Kamiokande website: The Inaugural Symposium of the Hyper-K Proto-Collaboration". Kashiwa, Japan. February 5, 2015.
- ^ "Proto-collaboration formed to promote Hyper-Kamiokande". CERN Courier. 9 April 2015.
- ^ "Hyper-Kamiokande construction to start in 2020". CERN Courier. 28 September 2018.
- ^ "Groundbreaking ceremony for Hyper-Kamiokande held in Hida, Japan". The University of Tokyo. 28 May 2021.
- S2CID 199687331.
- ^ "Hyper-Kamiokande experiment; Excavation of the gigantic underground cavern has finally begun".
- ^ "Kamioka Observatory website: Completion of the main cavern dome section of the Hyper-Kamiokande experiment". 11 October 2023.