# Presentation: 712926

## A Super-Neutrino Beam from BNL to Homestake

- Steve Kahn
- For the BNL-Homestake Collaboration
- Presented at NuFact 02
- http://pubweb.bnl.gov/people/kahn/talks/bnlHomestake.pdf

- BNL Homestake Long Baseline

- 2 July 2002

## AGS Upgrade to Proton Driver

- BNL Homestake Long Baseline

- 2 July 2002

##  Oscillation Physics Agenda

- Precise measurement of m232.
- Disappearance experiment with good energy resolution.
- Measurement of 13.
- Detection of e appearance mode.
- Detection of CP violation in neutrino sector.
- Detection of asymmetry between e and e processes.
- Observation of the *matter enhancement effect *in e appearance.
- Allows the measurement of the sign of m232.

- BNL Homestake Long Baseline

- 2 July 2002

## Very Long Baseline Experiment:
Place detector at Homestake Mine in South Dakota 2540 km from BNL.
The WIPP site in New Mexico at 2880 km from BNL would be an acceptable alternative.
The Homestake  site would consist of  a cluster of TEN 100 kton water Cherenkov  detectors.  Five of these modules would be the minimum acceptable to do reasonable physics.
These modules would be beneath the ground so that proton decay physics could also be down.
The  beam would need to be inclined 11.5° from the earth surface for the Homestake site.
The  beam to Homestake would be on axis to obtain the maximum flux.

- Place detector at Homestake Mine in South Dakota 2540 km from BNL.
- The WIPP site in New Mexico at 2880 km from BNL would be an acceptable alternative.
- The Homestake  site would consist of  a cluster of *TEN* 100 kton water Cherenkov  detectors.  *Five *of these modules would be the minimum acceptable to do reasonable physics.
- These modules would be beneath the ground so that proton decay physics could also be down.
- The  beam would need to be inclined 11.5° from the earth surface for the Homestake site.
- The  beam to Homestake would be on axis to obtain the maximum flux.

**The Detector for the Very Long Baseline Site**

- BNL Homestake Long Baseline

- 2 July 2002

## The Detector for the Medium Long Baseline Site

- A desirable location for detector would be at the first maximum for oscillations.
- If m232=0.003 eV2 and <E>1GeV, the first oscillation  maximum is at 412 km.
- Placing the detector 1.5° off axis for the BNL beam would produce a narrow spectrum peaked at 1GeV.
- Possible detector choices for *Medium Long Baseline *experiment:
- 25 kton Liquid Argon TPC detector (note: LOI states only 10 ktons.)
- 100 kton Water Cherenkov detector.
- Both of these detectors are similarly priced (according to NuMI off-axis LOI.)
- This detector should produce a precise measurement of m232 and produce the best measurement of 13.  It may also be sensitive to CP violations (depending on the parameters).

- BNL Homestake Long Baseline

- 2 July 2002

## The Close-In Detector

- A close-in detector is needed to provide reliable  beam alignment.
- This detector could be placed ~220 meters from the target behind the muon stop.  It could be below the water table assuming  interactions do not contaminate the ground water.
- An ideal choice would be a 0.33 kton Liquid Argon TPC detector.
- A detector of this size has already been built.
- This detector would be immersed in a 0.5 T magnetic field to determine the lepton charge.
- Such a detector would provide an accurate description of the  beam  composition.
- The good electron identification of LiqAr is important for this.
- This detector would produce a very high statistics, high resolution data sample for non-oscillation physics.

- BNL Homestake Long Baseline

- 2 July 2002

## Non Oscillated  Flux at Detector Locations

- Close Detector at 250 m

- Off axis Detector at 400 km

- At Homestake 2500 km

- BNL Homestake Long Baseline

- 2 July 2002

## e Flux Contamination Seen at Various Detector Sights  

- At Close Detector

- At 400 km 1.5° off axis

- At Homestake

- BNL Homestake Long Baseline

- 2 July 2002

## Event Estimates Without Oscillations

- The table below shows estimates for *quasi-elastic events* expected at the different detectors.
- The source is a 1.2 MW proton driver.
- The experiment takes data for 5 Snowmass Years.  (5107 sec.)
- The horn is set for  production:
- We certainly could do decent physics at an earlier phase with 0.5 MW machine and 1⁄2 the proposed detector mass.
- The horn is set for  production:

- BNL Homestake Long Baseline

- 2 July 2002

## Determination of m322 by Disappearance

- A precise measurement of m322 can be obtained by comparing the flux at the 400 km detector to the flux seen at the close-in detector.
- Upper figure shows the non-oscillated flux and the flux corresponding to m322 =0.0035 ev2.
- The lower figure shows the ratio of the far to near detectors with statistical error bars.
- Fermi motion at low E and resolution can limit the quality of this measurement.

- BNL Homestake Long Baseline

- 2 July 2002

## m322 by Disappearance from BNL to Homestake

- Figures on the left show the spectra of quasi-elastic events seen at the Homestake Mine (2540 km from BNL) for a 1⁄2 MT H2O č detector and 0.5 MW proton beam.
- Upper figure shows m322=0.0026 eV2.
- Lower figure shows m322=0.001 eV2.
- The figures include a 10% energy resolution to for both measurement errors and nuclear effects.
- Matter effects are included in these figures.
- Errors indicate the sensitivity expected for 5 Snowmass years of running.

- BNL Homestake Long Baseline

- 2 July 2002

## Background to Appearance Signal

- e signal

- Beam Contamination

- Background from NC 

- NC  background seen in H2O č detector at 400 km 1.5° off axis.

- This BG would be significantly reduced in a Liquid Ar detector

- BNL Homestake Long Baseline

- 2 July 2002

## Detector Backgrounds for the Appearance Signal

- There are two important background sources for the appearance signal:
- e contamination in the  beam from Ke3 and  decay.
- This appears to be ~1% for both the 400 km off-axis detector and the Homestake detector.
- Background from N N events where the  decay asymmetrically such that only one photon is seen and is confused for an electron.
- The N background is particularly difficult for 1 GeV <E<2 GeV.
- Choosing the 1.5° off-axis beam for the 400 km detector lowers <E> to ~0.9 GeV.
- How to reduce this background will have an influence on the detector choice.
- Liquid Argon should have good photon identification and have a better discrimination against the N background (if it is affordable).
- Another approach is build a larger H2O č detector and exclude e candidates below 2 GeV.  Also one needs sufficient phototube coverage.
- These options are being studied and more work needs to be done.

- BNL Homestake Long Baseline

- 2 July 2002

## CP Violation and Matter Effects at Homestake

- A very long baseline experiment allows for the study of CP violation and the matter effects associated to e interactions off atomic electrons.
- The figures at the left show the probability e (e) appearance no CP violation and maximal CP violation.
- m322=0.0026 eV2 and sin2(213)=0.04
- The measurement of the CP phase comes from the comparison of e to e appearance rates at different E.

- BNL Homestake Long Baseline

- 2 July 2002

## e Appearance at Homestake

- Figure shows e appearance events at the Homestake mine for 5 Snowmass years with 0.5 MW and a 0.5 Megaton Detector.
- m322=0.0026 eV2 and sin2(213)=0.04
- The error bars correspond to statistical errors expected.
- A 10% energy resolution is assumed for reconstruction and nuclear effects.

- BNL Homestake Long Baseline

- 2 July 2002

## Oscillated Events at Far Detectors

**For 1.2 MW proton driver and 25 kton Liq Ar detector at 400 km for a 5********10****7**** second running period we would expect:**

**With a 1 megaton H****2****O ****č detector at 2500 km for 5********10****7**** second period we would expect:**

- BNL Homestake Long Baseline

- 2 July 2002

## What is Required for this Neutrino Facility

- Upgrades to AGS which could be done in phases:
- Phase 1 to 0.53 MW: Superconducting Linac upgrade and 2.5 GeV Accumulator.
- Cost $ 65M
- Phase 2 to 1.3 MW:  AGS+Booster power supplies, RF upgrade.
- Additional cost $54M Total AGS upgrade ~$110 M.
- Neutrino Beam Considerations:
-  beam must be inclined 11.5° (13.0°) to reach Homestake (WIPP).
- Only a 1.7° inclined beam is required for the closer Lansing, NY site.
- Estimated beamline costs are $35M.
- Detector costs:
- Estimating 100 kton of H2O č or 25 kton of Liquid Argon from NuMI off-axis detector LOI: (The H2O č detector cost should be more reliable.)
- ~ $65M for detector at 400 km.
- No estimate has been provided for the 1 Megaton detector.

- BNL Homestake Long Baseline

- 2 July 2002

## Details of AGS upgrade and  beamline will be given in Bill Weng’s talk at this Conference.

- Details of AGS upgrade and  beamline will be given in Bill Weng’s talk at this Conference.

- BNL Homestake Long Baseline

- 2 July 2002

## Current Status and Conclusions

- A *letter of intent *has been submitted to the BNL management.
- A written *R&D Study Report *which will provide the technical basis for a future proposal* *will be submitted to the BNL laboratory later this summer.
- Hopefully this new facility can be build for a reasonable expenditure.

- BNL Homestake Long Baseline

- 2 July 2002