# Presentation: 765601

## Response of a Large Water Detector to Superbeams

- D. CasperUniversity of California, Irvine

## Long-Baseline Experiments Today

| Experiment | Source | Baseline(km) | E(GeV) | Power(MW) | Rate(yr -1) |
| --- | --- | --- | --- | --- | --- |
| K2K | KEK | 250 | 1 | 0.005 | 50 |
| MINOS | FNAL | 732 | 3 | 0.4 | 1000 |
| CNGS | CERN | 730 | 17 | 0.17 | 3700 |

- Note: “1 year” is defined as 107 seconds

## View from the Crystal Ball

- Near-term long-baseline experiments focused on dominant  channel
- Expect ~few percent measurements
- Possible direct observation of  appearance
- Sensitivity to sin2213 around few % level
- Sensitivity of all limited if m232 small
- Kamland may find LMA solar solution
- Critical to CP violation searches
- Mini-BOONE will test LSND
- Precision mixing measurements imperative if confirmed

## Next Generation Goals

- Precision measurement of dominant oscillation  channel
- Determine sign of m232
- Sensitivity to sub-dominant e  channel at 1**‰** level
- Sensitivity to CP
- Probably a “phase 2” goal, after 13
- Dependent on solar neutrino solution

## Neutrino Factories

- The ultimate tool for probing neutrino oscillation
- Enormous luminosity
- Exceptional purity
- Perfect knowledge of spectrum
- Flavor of initial neutrino tagged by charge
- Caveats:
- Technical challenges to muon acceleration
- Cost
- Not considered here

## Superbeams

- Exploit extremely intense proton sources to produce beam from -decay
- Intermediate step to neutrino factory
-  beam necessary for  beam
- Sensitivity intermediate between near-term experiments and neutrino factory
- Cost also intermediate
- Technical hill less steep to climb
- Proton drivers essentially designed (or existing)
- Radiation damage near target station may be important

## Possible Future Proton Drivers

| Source | Location | Proton Energy(GeV) | Power(MW) |
| --- | --- | --- | --- |
| Upgraded Booster | FNAL | 16 | 1? |
| UpgradedNUMI | FNAL | 120 | 1.6 |
| 50 GeV PS | JHF | 50 | 0.77(4) |
| SPL | CERN | 2.2 | 4 |

## Upgraded NUMI Beams

- Expect four-fold luminosity increase of MINOS neutrino beam
- e contamination: 0.5%
- Beam direction fixed by existing MINOS experiment
- Go off-axis to suppress high-energy tail?

**MINOS**

## Off-axis/Dipole NUMI beams

- Variations on NUMI:
- Off-axis detector with MINOS low-energy beam? (D. Harris)
- Use dipole after second horn? (F.DeJongh)
- Higher energy implies matter effects

## JHF 50 GeV PS

- Approved:
- 50 GeV PS
- 0.77 MW
- Proposed:
- Neutrino beamline to Kamioka
- Upgrade to 4 MW
- Outlook:
- Completion of PS in 2006/2007

## JHF Neutrino Beams

- Wide-band beam
- Horn-focusing only
- Long high-energy tail
- Narrow-band beam
- Pions momentum-selected with dipole
- Lower intensity
- Off-axis beam
- Intense, narrow
- Less tail than WBB
- 0.2% e around peak energy

## CERN/SPL

- Proposed:
- Recycle LEP RF cavities into proton linac
- Proton kinetic energy: 2.2 GeV
- Power: 4 MW
- Outlook:
- Not yet approved
- Recommendation by ECFA considered likely

## SPL Neutrino Beam

- MARS Monte Carlo
- Liquid Hg jet target
- 20 m decay tunnel
- Kaon production negligible
- Few **‰ ********e** content
- E ~ 250 MeV

## Beta Beam

- Recall talks of Zucchelli and Mezzetto
- Look for numu appearance:
- Exploit low-energy to avoid pion production
- Use muon mass and Cherenkov threshold to avoid e/mu confusion
- Possibility to run with neutrino and anti-neutrino sources
- Sensitivity to few degrees in 13

## Comparing Superbeams

- Upgraded NUMI
- High energy (3-15 GeV)
- Large event rates/kton, requires long baseline
- Matter effects visible
- Backgrounds probably worst at high-energy
- JHF
- Intermediate energy (0.7-1 GeV)
- Good compromise between backgrounds, baseline and rate
- Matter effects small
- 1% e in off-axis beam (0.2% on peak)
- SPL
- Low energy
- Requires short baseline, large detector
- No matter effects
- Backgrounds probably smallest

## Oscillations with Superbeams

- Precision measurement of sin2223 and m232 by high-statistics  disappearance
- Search for 13 by e appearance
- Measure sign of m232 using matter effects on neutrino/anti-neutrino beams
- Search for CP violation using e appearance in neutrino/anti-neutrino beams

## Water Detectors

- Large mass (UNO 440 kton fiducial)
- Excellent performance on simple events
- Lepton ID from pattern recognition
- Good lepton momentum, direction
- Topological rejection of some NC
- Difficult to identify neutrino flavor without contamination in complex events
- Require single-ring topology = loss of efficiency for high-energy (E > 1 GeV) neutrinos
- Efficiency less important than background rejection due to large size

## Upgraded NUMI Studies

- Exhaustive scans of parameter space for several detector scenarios, beams, and baselines performed by Barger, et al
- Parameterize detector performance
- This study:
- Use two different proposed beams
- Full simulation of detector
- Full reconstruction

## NUMI Beams in UNO

- Off-axis NUMILow-energy beam

- Dipole Beam

- Mis-ID background: about 5% of single-ring CC rateEfficiency for signal at 2 GeV ~ 25%(single ring cut)Next talk will discuss NUMI beam physics reach

- Bkgd

- Bkgd

- AppearanceSignal (Posc=1)

- AppearanceSignal (Posc=1)

## JHF  Super-Kamiokande

- 295 km baseline
- Super-Kamiokande:
- 22.5 kton fiducial
- Excellent e/ ID
- Additional 0/e ID
- Hyper-Kamiokande
- 20 fiducial mass of SuperK
- Matter effects small
- Study using fully simulated and reconstructed data

## JHF  SK:  Precision

- 5 years, JHFSuperK

- OA 2°LE1.5LE3

## JHF  SK: θ13 Sensitivity

- 5 years, OA 2°sin2213 = 0.1

- sin2213 90% CL sensitivity ~ 0.01 for 1.610-3 < m2 < 410-3 eV2 (5 years)

## SJHF  HyperK: CP Sensitivity

- 4 MW (upgraded) JHF20SuperK detector
- 2 years neutrinos, 6 years anti-neutrinos
- Sensitive to maximal CP for LMA

## SPL  UNO

- SPL beam to Fréjus
- 130 km baseline
- UNO:
- Next-generation water Cerenkov nucleon decay and neutrino detector
- 20 fiducial mass of SuperK (445 ktons)
- Study using fully-simulated and reconstructed data

## /e Background Rejection

## Particle Identification Cut

- Use Cerenkov light pattern (including opening angle, if possible) as primary  rejection
- Tighten cut to reduce mis-ID further
- e CC Efficiency: 79%
-  CC Contamination:~0.6%

## Neutral Current 0 Production

- Data very sketchy
- ANL
-  p n + (7 events)
-  n n 0 (7 events)
- Gargamelle
-  p p 0 (178 events)
-  p p 0 (139 events)
- No cross-section
- BNL
-  p p – /  p p +
- Hope to measure with 1kton detector (K2K)

- K2K Preliminary1-kton, single 0’s

## Energy Flow Fitter

## 0/e Background Results

- 0/e Background Results

- Apply energy-flow fitter to surviving events
- Cut:
- M < 45 MeV
- Most 0 background eliminated

- Oscillated beam

- Beam Contamination

- NC 0

- Cut (45 MeV)

## CERN  UNO: θ13 Sensitivity

- Search for e appearance
- 90% CL sin2213 sensitivity at ‰ level in favored m2 region

## CERN  UNO: CP Sensitivity

- Sensitivity to maximal CP for LMA solution, sin2 213=0.03 or less
- No confusion from matter effects

- 13

## Beta Beam (Ne18)

- Apply simple cuts
- Fiducial volume
- Single-ring
- Particle ID
- Directional cut possible in principle for 6He
- Assume atmospheric neutrinos are excluded by event time

- Mu-like Signal

- E-like Bkgd

## Ne18 Beta Beam with Decay Cut

- Decay cut eliminates most mis-ID
- Remaining events are NC charged pi
- About 3 events background in 5-year 18Ne run
- One event background in 10-year 6He run

## Efficiency for Beta Beam

- Inefficiency is essentially due to energy transfer leaving lepton below threshold
- Close to 100% for muon momentum > 200 MeV/c
- Need to tune beam energy with oscillation parameters and efficiency

## Summary

- Long-baseline experiments with superbeams offer:
- 1% measurements of  oscillation
- 1**‰** sensitivity to sin2213
- Low or intermediate energy beams combined with large water detectors could also detect CP violation in favorable LMA scenarios
- Higher energy beams at very long baselines can measure sign of m232
- Superbeams fall short of a neutrino factory, but could bring us a step closer to building one