1. Peter Litchfield Minnesota University For the NOA collaboration
NOA, the next step in investigating the  sector
Measure sin22θ13?
Determine the sign of m2?
First possibility of seeing CP violation?

2. Three flavour mixing n1 n3 nt nm ne n2 Ue1 Ue2 Ue3 Um1 Um2 Um3
Ut1 Ut2 Ut3 =
PMNS matrix: the lepton analogue of the CKM matrix for
quarks. 3 mixing angles and 1 CP violating phase.
mass states
weak states
Accelerator e appearance and/or reactor experiments
Atmospheric
solar

3. What do we know now?
CP violation?

4. Oscillation formalism
Probability of  oscillating to e in vacuum:
P=P1+P2+P3+P4
P1=sin2θ23sin22θ13sin2(1.27m132L/E)
P2=cos2θ23sin22θ12sin2(1.27m122L/E)
P3= Jsinδsin(1.27m122L/E)
P4=Jcosδcos(1.27m122L/E)
J=cosθ13sin2θ12sin2θ13sin2θ23sin(1.27m122L/E)sin(1.27m132L/E)
In matter at oscillation maximum P1 ≈ P1(12E/ER) and P3,P4 ≈ P3,P4(1E/ER)
Top sign for neutrinos for normal hierarchy, antineutrinos for inverted hierarchy
~30% effect for NOA, ~11% for JPARC, more below maximum, less above

5. NOA, have beam, will travel
An intense  beam almost exists at Fermilab, first beam for MINOS in December.
How to use it to measure e?
Θ13 is small, rate low
Build big detector; 50 kton, nine times MINOS
Backgrounds are large, particularly from high energy  producing neutral current events
Make a narrow band beam at the oscillation maximum by going off-axis

6. Off-axis beam
At 14mrad off-axis almost all  produce  around 2 GeV, i.e. at oscillation maximum

7. Off-axis beam
At 10 km off axis compared to the zero degree beam we have;
~5 times the event rate around the oscillation maximum
Very much smaller high energy component, very much reduced neutral current background
The rates shown here are those that the present NuMI beam is expected to deliver on the time scale of NOA
A proton driver at Fermilab could increase the rates by at least a factor of 5

8. Detector The detector needs to be: ~9 times the mass of MINOS.
Not 9 times the cost. Total cost of beam + detectors for MINOS was ≈$170M. Reasonable that the total cost of the new experiment should be about the same. But no beam cost this time.
Optimised to detect charged current electron events and reject charged current muon and neutral current events.
Low Z to emphasize the electron shower
Good longitudinal sampling ≤ ⅓ radiation length to observe the shower development and separate  conversions from production electrons.
Good transverse granularity to separate the electron from other produced particles.
Liquid scintillator with particle board absorber chosen, based on a detailed cost and sensitivity analysis and backed by experience with the MINOS detectors.

9. Baseline Detector Monolithic structure to APD readout
Liquid Scintillator cells
4cm x 3 cm x 14.4 m
Read out by U-shaped WLS fiber into an APD
30-cell PCV extrusions,
24 extrusions/plane,
750 planes
= 18,000 extrusions
= 540,000 channels
Absorber:
20 cm particleboard/
plane (~1/3 Xo)
Total mass 50kton
to APD readout
750

10. APD readout
APD plus looped fiber the main advance from the MINOS system
85% quantum efficiency
Gain 100 (operate at -15C to reduce noise)
More sensitive than a PMT to the long wavelengths left after attenuation in fibers
Greater sensitivity enables readout of 15m instead of 8m cells
35 photoelectrons from far end of 15m cell for min-i particle
Low cost, ~$12/channel
2 fibers from cell to each pixel

11. Detector sites
Matter effects increase with distance, go as far away as possible. NUMI beam has a potential length > 800km. Compare with T2K at 295 km
Present preferred site is at Ash River, 810km from Fermilab, 12km off axis.
The detector has to be built on the surface, too large, too expensive to go underground.
Beam spill gives live time ~100 seconds/year. We believe this plus an active shield will give adequate cosmic background rejection. Test soon.
Similar near detector at Fermilab will monitor the initial beam and estimate backgrounds
Soudan

12. Totally Active Detector
90 m
17.5 m
We are investigating the possibility of removing the absorber and constructing a detector solely from scintillator modules
Thicker (more light), longer (less light) cells
85% scintillator, 15% PVC
Readout on top and one side
Same price implies half mass, 25kton
Lack of passive absorber implies better event definition and improved event selection and background rejection.
First simulations indicate that the sensitivity of the 25kton totally active detector is at least equivalent to the 50kton baseline detector and may be significantly better for the measurement of parameters such as sin22θ23
Currently studying engineering of constructing a totally active detector

13. A e event in the TA detector
The color code indicates the relative pulse height
The scale is in cell
numbers, so one unit is
4.9 cm horizontal axis
4.0 cm vertical axis
The lines are the trajectories
of the final state particles:
charged leptons in red,
charged pions in blue,
protons in black, and
neutral pions in green
The line length is proportional to energy, but NOT to the expected path length of the track
A ne CC event
p pi+ pi- e-   2.52 GeV, lower (1-y)

14. A background event The color code indicates the relative pulse height
The scale is in cell
numbers, so one unit is
4.9 cm horizontal axis
4.0 cm vertical axis
The lines are the trajectories
of the final state particles:
charged leptons in red,
charged pions in blue,
protons in black, and
neutral pions in green
The line length is proportional to energy, but NOT to the expected path length of the track
A background nm CC event, nm + A -> p + m- + p0+ p0 , En = 1.70 GeV

15. Simulations  CC NC Beam e Oscillated e
We have made a full GEANT based simulation of the beam, detector, event reconstruction and event selection for the baseline detector.
Neutrino events were produced using the NEUGEN3 generator.
A 5 year exposure to the 50kton detector, 12km off-axis at 810 km from Fermilab with a beam of protons on target/year was assumed.
m2= eV2, sin22θ23=1.0
sin22θ13=0.05, about half the CHOOZ limit
E (GeV)
Events
Event neutrino energy spectrum

16. Simulations
Events were reconstructed, required to lie in a containment volume and a candidate electron track identified.
Cuts were made on;
Event length
Total pulse height
Fraction of hits in the electron track
Hits/plane in the electron track
Angle of electron track to beam
A likelihood analysis based on event parameters made on the remaining events
Events
Pulse height
Hits/plane
Events
Likelihood ratio

17. Signal and background For these parameters we find after selection;
Signal 57.7 events (18% efficiency)
Background 24.3 events
1.1  CC, 10.5 NC, 12.7 beam e CC
Figure of merit (Signal/Background) 11.7
Off-axis distance (km)
Signal events
Background events
FOM*4
12km
Optimisation of offaxis position for detecting e (maximise FOM) and determining the sign of m2 (Maximise asymmetry between  and )

18. Ambiguities
We measure the probability of oscillation (P). This is dependent on sin22θ13, the sign of m2 and the CP violating parameter δ
Using both  and beams some but not all of the ambiguity can be resolved.
beams are much less intense so measurements are less accurate.
Alternatively reactor experiments which measure directly sin22θ13 or T2K measurements which are insensitive to the sign of m2 can be used to resolve the ambiguity

19. Discovery potential (sin22θ13)
The discovery limits will be a function of the other parameters
We thus present the limits as a function of δ and for both signs of m2
Solid lines are for a 5 year run with the NuMI beam intensity. A proton driver with 5 times the neutrino flux would give the dashed lines.
Note better sensitivity if m2>0

20. Discovery potential (sign m2)
To measure the sign of m2 we need to run with both  and
3 year run with each
Since the sign is a binary quantity 2σ is probably good enough
T2K has no sensitivity because of its short baseline

21. Long term m2 sign measurement
NOA, plus upgrades and/or other experiments, probes to low sin22θ13 values
+T2K
+ a Fermilab proton driver
+T2K and proton driver
+Hyper-K
+ a second NOA detector at the second oscillation maximum
However note that combining with a reactor experiment measurement of sin2θ13 gives little improvement in the m2 sign measurement

22. CP violation?
With a proton driver there is a possibility of observing CP violation at 3σ, if we are lucky with the value of δ
No possibility without
Combining NOA and T2K, both with proton drivers significantly increases the potential

23. Experiment status
The NOA collaboration has formed (34 institutions, ~160 physicists). New collaborators are still welcome.
NOA is in the prototyping and engineering phase where the preliminary costing of $147M will be solidified
A technically driven schedule could see detector construction starting in with first data in an incomplete detector in the existing beam in 2008
Quote from the Fermilab PAC June 2004: “The PAC strongly endorses the physics case for the NOA detector and would like to see NOA proceed on a fast track that maximises its physics impact”. This has been endorsed by the Fermilab management.
Fermilab has instituted a study of its future facilities which is focusing on the building of a proton driver which offers a natural upgrade path for NOA (and MINOS). With the proton driver it may be possible to observe CP violation in the neutrino sector.
MINOS + NOA + a proton driver offers an exciting long term neutrino program at Fermilab prior to the operation of a neutrino factory.