# Presentation: 158481

## Neutrino Oscillations Working Group Summary

- Steve Brice (FNAL)
- Debbie Harris (FNAL)
- Walter Winter (IAS, Princeton)

- The Excitement of Neutrino Physics
- What are the Measurements
- Possible Landscapes for Neutrino Oscillations at Proton Driver Startup
- Peek at physics reach with and without a proton driver

- Caveat:  Real summary of working group would take an hour or more!

## Neutrinos Are Everywhere

- Neutrinos outnumber ordinary matter particles in the Universe (electrons, protons, neutrons) by a factor of ten billion.
- Depending on their masses they may account for a fraction (few % ?) of the “dark matter”
- Neutrinos are important for stellar dynamics:  ~6.61010 cm-2s-1 stream through the Earth from the sun. Neutrinos also govern Supernovae dynamics, and hence heavy element production.
- If there is CP Violation in the neutrino sector, then neutrino physics might ultimately be responsible for Baryogenesis.
- To understand the nature of the Universe in which we live we must understand the properties of the neutrino.

- January 19, 2005

## What are these “Properties” of the Neutrino?

- We know there are three generations:  e
- We know they are spin 1⁄2 and have no charge...what else is there?
- Until lately we thought they had no mass...
- Pretend for the moment that there are 2 generations:

- Flavor Eigenstates
- (produce and detect)

- Mass Eigenstates
- (travel through space)

- Properties to measure:  mixing angle , and the masses m1 and m2
- But it looks like only |m22-m12| can be measured!

- January 19, 2005

## Why are Oscillation Measurements Exciting?

- Neutrino mass terms are Beyond the SM:  need
- right-handed neutrinos  Dirac mass terms, or
- violation of lepton number conservation  Majorana mass terms.
- We know that neutrino masses & mass splittings are tiny compared to the masses of the other fundamental fermions. This suggests radically new physics, which perhaps originates at the GUT or Planck Scale, or indicates the existence of new spatial dimensions, or .....

- January 19, 2005

## Neutrino Measurements Drive Theory!

- One thing we do know is Lepton Mixing is qualitatively very different from the quark mixing. This necessarily constrains theoretical ideas about the underlying relationship between quarks and leptons.
- Oscillation measurements have already eliminated a previous generation of GUT models, leading to a newset of models designed to accommodate the data.
- Further oscillation measurements will necessarily reject the majority of the new models, and hopefully lead to new ideas about physics beyond the Standard Model

- Quarks:
-  small

- Leptons:
- Is small?

- January 19, 2005

## Neutrino Mixing in 3 Generations

- We only know first and third matrix (roughly) right now...

- January 19, 2005

## Neutrino Masses

- We know mass 1 large mass splitting, 1 small mass splitting
- But we don’t know the ordering!
- From Mena and Parke,
- hep-ph/0312131

- Wolfenstein, PRD (1978)

- Changes effective mixing
- Angle and effective baseline

- e- density

- January 19, 2005

## Oscillation Probabilities

- For any one energy and baseline, you don’t get the whole story...
-       (two measurements three unknowns)
- Need two energies, or two baselines, and at least one baseline needs to be long enough to see matter effects to get to mass hierarchy!

- P(→e)=P1+P2+P3+P4

- Minakata & Nunokawa JHEP 2001

- January 19, 2005

## Electron Neutrino Appearance Key Points

- The mixing angle 13 sets the scale for the size of the effect
- CP violation term CP flips sign of second term
- compare  with anti- probability
- Mass Hierarchy changes the sign of matter potential
- compare  with anti- probability
- But Long baseline needed!

- January 19, 2005

## Predictions from theory

- Predictions from neutrino mass models (GUT models, flavor symmetries, textures etc):
- For 13
- For deviations from maximal mixing
- For mass schemes
- ...
- For example: 13Many models predict a 13 within the reach of proton driver based experiments!
- In addition: Quantum corrections can produce nonzero 13 even if zero at GUT scale!

- January 19, 2005

## What does a Proton Driver have to do with Neutrino Oscillation Measurements?

- Throughout history, accelerator-based neutrino experiments are always asking for more protons

- protons

- pions

-  neutrinos at 1km

-  neutrino interactions/kton at 1km

- NuMI Case
- (at .1MW):

- Need for protons will only get higher:
- 	looking for rare (<5%) processes
- 	need detectors very far away
- 	efficiency loss due to background rejection

-  neutrino interactions/kton at 735km

- January 19, 2005

## New Results Prior To PD Startup

- Conventional Beam
- Better measure m223, some sensitivity to 13
- MINOS (Fermilab to Minnesota)
- ICARUS (CERN to Gran Sasso, Italy)
- OPERA (CERN to Gran Sasso, Italy)
- SuperBeams
- Good sensitivity to 13, precision measurement of 23 , some sensitivity to hierarchy
- T2K (Tokai to Kamioka, Japan)
- NOA (Fermilab to Minnesota)
- Reactor
- Good sensitivity to 13
- Double Chooz (France)
- “Reactor II” (USA, China, Brazil,.....)
- Short Baseline
- Investigate LSND result
- MiniBooNE (Fermilab)

- January 19, 2005

## 3 Scenarios for sin2213 KnowledgePrior to PD Startup

- 3 Scenarios for SIN2213
- Scenario 1: SIN2213 > ~0.04
- Scenario 2: ~0.01 < SIN2213 < ~0.04
- Scenario 3: SIN2213 < ~0.01

- January 19, 2005

## Discovery Potential

- Answer depends MOSTLY on size of 13, but...
- The farther away  is from 0 or , the easier it will be to measure as being non-zero
- If mass hierarchy and CP are in “same direction” that also helps...
- No matter what,
-     we need more
-     protons...

- “Map” to define the
- parameter space:
- As function of sin2213,
- over how much of  can
- each physics goal be met?

- Reach without a new Proton Driver at FNAL:

- January 19, 2005

## “Existing” Detectors, Existing Beamlines + Proton Driver
NOA Detector (810km, 2GeV beam)

New Detectors, Existing Beamlines 
T2K measurements:  295km, 0.7GeV beam
Other Off-Axis Detectors:  710km, 0.7GeV beam 
New Beamlines, Existing Detectors
Pointed towards NOA Detector (still under study) 
New Detectors and New Beamlines 
National (Deep) Underground Science Laboratory 
One Broad-Band Beam (1290km or 2450km) 
Two Beamlines, one on axis, one off axis (1290km) 

New Technology:  Un-conventional Beams
Neutrino Factory
If technology breakthrough:  high energy beta-beam
Natural synergy with muon physics program

Best Long Term Option depends on what is seen in the next generation, and what happens in the rest of the world! 

- NOA Detector (810km, 2GeV beam)
- New Detectors, Existing Beamlines
- T2K measurements:  295km, 0.7GeV beam
- Other Off-Axis Detectors:  710km, 0.7GeV beam
- New Beamlines, Existing Detectors
- Pointed towards NOA Detector (still under study)
- New Detectors and New Beamlines
- National (Deep) Underground Science Laboratory
- One Broad-Band Beam (1290km or 2450km)
- Two Beamlines, one on axis, one off axis (1290km)
- New Technology:  Un-conventional Beams
- Neutrino Factory
- If technology breakthrough:  high energy beta-beam
- Natural synergy with muon physics program
- Best Long Term Option depends on what is seen in the next generation, and what happens in the rest of the world!

- Scenario 1:
- sin2213> ~0.04

- 

- Scenario 2:
- ~0.01<sin2213< ~0.04

- Scenario 3:
- sin2213< ~0.01

- Where we are determines how much we need:
- but need Proton Driver no matter what!

- January 19, 2005

## Scenario 1: sin2213 > ~0.04Existing Detectors, Existing Beamlines

| Vital Statistic | NOA | T2K |
| --- | --- | --- |
| Neutrino Energy | 2GeV | 0.7GeV |
| Baseline  | 810km | 295km |
| Detector Mass | 25 kT | 50 kT |
| Detector Technology | Scintillator | Water Cerenkov |
| Proton Energy | 120GeV | 120GeV |
| Proton Power | 2MW | 0.8MW |

- NOA Detector, NuMI Beamline

- Complmentarity between NOA and T2K

- Scenario 1: sin2213 > ~0.04Existing Detectors, Existing Beamlines

- January 19, 2005

## Scenario 2: ~0.01 < SIN2213 < ~0.04New Detectors, New Beamlines

- Need for underground lab from proton decay, Dark matter searches ...
- Massive detector good destination for long-baseline  neutrino beams-> Synergy!
- Study both broad and narrow band beams

*Highway tunnel*

*Detector*

*h =20 m*

***≈**70 m*

- A. Rubbia

- Liquid Argon TPC (100xIcarus)

- Water Cerenkov
- (20xSuperK)

- January 19, 2005

## Scenario 3: sin2213 < ~0.01New Beamline Technologies

- Neutrino Factory Still has the best sensitivity for seeing a non-zero sin2213

- First step towards a Neutrino Factory:
- Low Energy Protons, High Proton Power
- Detector Needed for Neutrino Factory:
- MINOSx10...(recall MINOS is modular!)

- Best reach for ~3000km baseline, 50GeV ring

- January 19, 2005

## Reach without new Proton Drivers:

- January 19, 2005

## Physics Reach with a Proton Driver

- For every scenario, the FNAL program can offer a unique opportunity to measure mass hierarchy
- For sin2213>.01 FNAL has already in hand very powerful tool to get to the physics:  the NuMI beamline

- January 19, 2005

## Summary

- There is much we do not know about neutrinos, yet they are more plentiful than ordinary matter
- There is much we didn’t not predict about neutrinos:  they provide a new window on processes beyond the standard model
- The only way to get at CP violation and the mass hierarchy is through accelerator-based oscillation measurements
- Fermilab Proton Driver provides a powerful tool to get to this new physics—our best bet for seeing mass hierarchy!
- Steve Brice’s talk in the Proton Driver Review was 1 hour, there is a lot I did not cover!
- What if LSND is due to oscillations?
- What about the23 mixing angle?  Is there a symmetry there?
- What if something else totally unexpected happens?
- Stay tuned for more talks about what we learned...

- January 19, 2005