1. Neutrino beams in China
Jingyu Tang
Institute of High Energy Physics, CAS
NNN16, IHEP, Beijing, Nov. 3-5, 2016

2. Outline Brief introduction to the MOMENT Recent study progress
Physics potential
MOMENT R&D and neutrino cross-section measurements at CSNS/EMuS
Summary

3. Brief introduction to MOMENT

4. MOMENT study
MOMENT: A muon-decay medium baseline neutrino beam facility
MOMENT was launched in 2013 as the third phase of neutrino experiments in China, following Daya Bay and JUNO
Originally as a dedicated machine to measure CP phase in the future, if there are still the needs then. Physics goals should be modified along with the neutrino physics development.
As a driving force to attract researchers from China as well international collaborators to work on neutrino experiments based on accelerators

5. Features: Using a CW proton linac as the proton driver: 15 MW
China-ADS linac development
Fluidized target in high-field SC solenoid
Muon transport and decay channel (Pure + or - decay, managed beam)
Also possible with -decayed beam and Decay-at-Rest neutrinos

6. Proton driver Design goal:
Beam power: 15 MW
Beam energy: 1.5 GeV
Beam current: 10 mA
Using the China-ADS linac or a dedicated linac with large simplification (much less redundancy)
3.2-MeV RFQ (room-temperature)
Three sections SC spoke cavities (160 MeV)
Two sections SC elliptical cavities (1.5 GeV)
In total, 196 SC cavities in 42 cryostats, linac length: ~ 300 m

7. Estimate of neutrino flux
POT (5000 h):  1024 proton/year
Muon yield: 1.62  /proton
Total neutrino yield: 4.8  /proton (in pair)
5.4  /year (in pair)
(NF: 1.1  /year )
Neutrino flux at detector: dependent on the distance
4.7  /m2/year km)

8. Recent progress

9. ADS linac development
Parallel efforts at IHEP and IMP on the linac front (RFQ + low- cavities, 10 MeV)
Very successful from both teams (different schemes)
RFQ CW operation (IMP: 100%, IHEP: 99%)
Low- superconducting cavities (10 MeV at IHEP, world first; 5 MeV at IMP, 10 mA; both pulsed)
Prototypes of different SC cavities (Spoke, HWR, Elliptical)
Second ADS phase (CIADS) approved
Will be in Huizhou, Guangdong (not far from Daya Bay)
250 MeV -10 mA, CW mode
Test-stand at IMP

10. Target Station Further optimization of the mercury jet target design
More interests in developing fluidized granular target in collaborating with the C-ADS target team, and also waiting for study result with fluidized tungsten-powder target in Europe

11. Schematic of a waterfall-like granular target
Preliminary study shows good heat transfer and pion capture efficiency
Implantation method (such as cutting slots in the inner shielding) is still under development

12. Charge selection
A selection section to select +/+ from -/-, as either + beam or - beam is used for producing the required neutrinos
Reverse the fields when changing from + to -
Also for removing very energetic pions who still survive
Very difficult due to extremely large beam emittance (T/L)
Two schemes: based on 3 SC dipoles with strong gradient (or FFAG), and bent SC solenoids
Present study shows Dipole+solenoid solution works for smaller emittance, bent solenoid solution works for very large emittance

13. Spent protons extraction
Features
Very important to avoid huge heat deposit and radiation in the target station (also meaningful for NF)
Spent protons can be reused
Very difficult in practice
Method
Extract only high-energy
protons (scattered from target)
Collimation and bent solenoids
(+dipole field)

14. Physics potentials

15. Physics potential in CP
Detecting CP-violating phase in the lepton sector
Absolute measurement: P(νμ→νe)
Relative measurement: P(νμ→νe)-P(νμ→νe)
Advantages of MOMENT
High intensity neutrino beam : >1021 /year
Relative low energy (~300 MeV) and short baseline (~150 km)
Minimum interference from matter effect
Low π0 background
Muon decay neutrinos
Measure multiple oscillation channels at the same time
Low beam intrinsic background
Requirement to the detector
e/μ identification
Neutrino/antineutrino identification

16. IBD spectrum in the detector
Signal and background
Detector options
Liquid scintillator
Gd-doped water Cherenkov detector
Signals (μ+ decay, 5,000kton×year, 100% efficiency)
IBD: 435 (easy to be identified with neutron tagging)
νe CC: ~1,600 (large contamination of νe without magnetized detector)
Oscillation signal of μ- decay is ~1/3 compared to μ+ decay
Major background
Atmospheric neutrinos
Charge mis-identification
Another calculation can be found in arXiv:
IBD spectrum in the detector

17. Direction of e+ from IBD
Perspective
e/μ identification in the liquid scintillator
MC studies are ongoing
Improve charge identification
A large magnetized detector?
Reduce atmospheric background
Reconstructing neutrino direction
Sending neutrino in short bunches (arXiv: )?
Not realistic in ADS-type accelerator (CW beam) μ+ e+
Scintillation light
Cherenkov light
Cherenkov ring
Direction of e+ from IBD

18. Another possibility Make use of decay-at-rest neutrinos? DAEδALUS
MOMENT-DAR
PRL 104, (2010)

19. Other physics potentials
Search for sterile neutrinos
DAR at the two beam dumps: target station and beam dump
Neutrino cross-section measurement
Both -decay and -decay neutrinos in MeV
Muon physics
Very high intensity DC muon beam

20. MOMENT R&D and neutrino cross-section measurements at CSNS/EMuS

21. EMuS at CSNS
We plan to build an experimental muon source (EMuS) at China Spallation Neutron Source (CSNS).
CSNS is under construction, expected to complete in March 2018, 100 kW at Phase I and 500 kW at Phase II
EMuS will use 4% beam power to produce intense muon beams for MOMENT R&D studies and SR multidisciplinary applications. Potentially it may be also used for neutrino cross-section measurements and muon physics.
MOMENT R&D studies include muon capture in high-field, charge selection, spent proton extraction etc.
Present EMuS study is supported by an NSFC fund for R&D and prototypes

22. 2009年5月9日 22

23. Beamline layout of EMuS and operation modes
Beam operation modes (independent):
Neutrino mode
Wide energy spectra
Ref. Pπ= MeV/c
Surface muon mode
Momentum spread: ±5%
Ref. Pμ=29MeV/c
Decay muon mode
Momentum spread: ± 10%
Ref. Pμ = MeV/c

24. ν-fluxes for neutrino beam - 100 % π+, π- selection (Decay channel: ~25 m, Aperture: 30 cm )
Detector 3 m upstream of the DT
Detector 3 m upstream of the DT
νμ , <Eν> ~ 200 MeV - νμ
neutrino beam
anti-neutrino beam - νμ νμ νe - νe
neutrino beam
anti-neutrino beam
Ν ν (x1014)
/ m2 / 200 days % νμ
260
97.5
2.2
2.5
νμ-
3.3
1.25 85
95.5 νe -
0.0002
1.8 2
2-5% stat. error
108 p.o.t. - -

25. CC-events (water target )
νμ , <E> ~ 300 MeV - νμ
neutrino beam
anti-neutrino beam νe νμ - νμ - νe
preliminary
neutrino beam
anti-neutrino beam
CC / ton / 200 days at 3m %
CC / ton / 200 days at 3m νμ
1034
98.6
5.6
7.3
2.9
0.3
71.5 90 νe
11.3
1.1 -
2.1
2.7 - -

26. ν cross-section measurements
World unique at energy of 300 MeV
1000 CC events / ton / 200 days (3.2x1020 p.o.t) at 3 m
Possible upgrade: beam power, higher capture field
(-> CC events / ton / 200 days at 3 m)
Might be interesting to explore sterile neutrinos (L/E ~ 1 m/MeV at 2500 m) similar to LSND and MiniBooNE

27. Summary
MOMENT is a driving force to attract Chinese researchers to collaborate on neutrino experiments based on accelerator-based neutrino beams
Also participating international projects: LBNF, MICE, …
Current studies focus on
Suitable detector and physics potential with different neutrino sources
Fluidized granular target and spent protons extraction
Charge selection methods
Some R&D will be done at CSNS/EMuS
It is also possible to carry out neutrino cross-section measurements and sterile neutrino search at EMuS

28. Thank you for attention!