# Presentation: 351036

## Next step in neutrino oscillation experiments?

- Let’s face the “facts”
- Neutrinos oscillate
- There is at least one oscillation in the frequency range m2~1-4x10-3 eV2
- Distance 730 km    1-3 GeV beam
- with sin22~1
-  MINOS will confirm the oscillatory pattern, improve the knowledge of m2
- Will have NUMI neutrino beam

## Want to know/measure

- 1-sin2223
- sin2223= 1  new symmetry ?
- Subdominant oscillation ->e:|Ue3|2
- Mass hierarchy
-  CP violation, if permitted by:
- m12 not too small
- |Ue3|2  not too  small
- The next step ?
- Determine/limit|Ue3|2
- If sizeable  get a shot at the mass hierarchy/CP

## NuMI Neutrino Beams

- signal

- Increase the flux in 1-2 GeV region ?
- Reduce the high(er) energy tail ?

## Two-body decay kinematics

## Low Energy Beam: Off-axis

- Neutrino event spectra at putative detectors located at different locations

## Medium Energy Beam: Off-axis

- More flux than low energy on-axis

## High Energy Beam: Off-axis

- 1/3 of a the flux with medium energy beam

## Low/Medium Energy: Beam Composition

- pions

- kaons

## Disappearance Experiment, 10 kty m2=0.0015/0.002 eV2

## Disappearance Experiment, 10 kty m2=0.0025/0.003 eV2

-  ~1-sin2223

**Oscillatory pattern!**

## Disappearance Experiment: m2=0.0035 eV2

## How to predict  the off-axis spectrum. 

- Neutrino fluxes detected at the near and far detectors produced by the same parent hadron beam, hence:

- Correlation function M depends mostly on the focusing system and the geometry of the beam line (hep-exp/011001). It depends on the location of the far detector.

- every neutrino event observed at the near detector implies a certain flux(E) at the far detector.

## How to predict  the off-axis spectrum II

- Decay angle QNQF, henceENEF.
- Take as an example two neutrino energy bins:

- Well focused, parallel beam of pions M11,M22 0, M12=M21=0
- Realistic beam, far detector on axis M11,M12 0, M21<M11, M12~0
- Off-axis beam M11,M22,M21~0, M12 0

## Systematics: Predict the Spectrum. Medium Energy

- Event spectra at far detectors located at different positions derived from  the  single near detector spectrum using _different particle production models._
- Four different histograms superimposed

**Total flux predictable to ~1%.**

## e appearance experiment

- Large number of  oscillating away
- Below  threshold
- The only backgrounds due to
- e component of the beam
- NC background
- NC background _as small as it can be_ (very small higher energy tail not contributing to the signal)
- Total energy constraint

## e Background: ME case

- 

- n

- e

- e ~0.5%

## Sensitivity to |Ue3|220 kto x  years exposure

- Assuming that the NC background is reduced below the intrinsic e level (~0.5%)

**Detector located at 10 km most sensitive**
**Sensitivity down to the level |U****e3****|****2**** ~ 0.003 **

## Mass hierarchy? CP?

- Minakata and Nunokawa, hep-ph/0108085
- m213=3x10-3 eV2
- m212=5x10-5 eV2
- sin2213=0.05

- vacuum

- m213< 0

- m213> 0

- P(->e)

- P(->e)

- P(->e)

- P(->e)

- P(->e)

- P(->e)

## Measuring/constraining CP parameters?

- 30 kton x year exposure (at a ‘design’ intensity) for neutrinos and 30 kton x year for antineutrinos

## Have beam. Just add detector(s).

- Given
-  a sensible size detector (20 kton?)
-  potential intensity upgrades (welcome, but not critical)
**There is a great physics potential of the NuMI neutrino beam.**
- _An unbiased physicist’s opinion:_
- It is very important that we build as good beam as _practically_ possible (just good enough for low energy run of MINOS may be not quite enough)

## Detector(s) Challenge

- Surface (or light overburden)
- High rate of cosmic ’s
- Cosmic-induced neutrons
- But:
- Duty cycle 0.5x10-5
- Known direction
- Observed energy > 1 GeV

- Principal focus: electron neutrinos identification:
-  Good sampling (in terms of radiation/Moliere length)
- Large mass:
- maximize mass/radiation length
- cheap

## A detector example/proof of principles

- Cheapest low z absorber: recycled plastic pellets
- Cheapest detector: glass RPC

## A step beyond the cartoon detector

- Full GEANT simulation (GMINOS is a wonderful tool. Thanks, Robert)
- Event displays. (MINOS_RECO is a wonderful tool.Thanks, Robert)
- Simple event reconstruction. (Magenta curve on the displays is a reconstructed track)
- Simple analysis.

## A ‘typical’ signal event

## A ‘typical’ background event

## And the result is:

- NC background sample reduced to 0.3% of the final electron sample

## This was just an ‘existence proof’

- Better reconstruction
- Optimized analysis
- Better detector
- Cheaper detector
- Optimized location (energy and/or baseline)
- Etc.. Etc..

## Conclusion/Recommendation

- There is an exciting physics opportunity in addition to MINOS
- Let’s have a focused workshop:
- ‘Physics opportunities with the NuMI neutrino beam’ – April/May at Fermilab
- including:
-  non-oscillation physics [relevant for the oscillations]
- Future proton upgrades