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?

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

What do we know now? CP violation?

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

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

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

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

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.

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

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

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

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

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)

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

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 3.7 1020 protons on target/year was assumed. m2=0.0025 eV2, sin22θ23=1.0 sin22θ13=0.05, about half the CHOOZ limit E (GeV) Events Event neutrino energy spectrum

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

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 )

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

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

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

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

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

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 2006 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.