Pre-  Factory Possibilities Leslie Camilleri CERN, PH Scoping Study Meeting Imperial College May 6, 2005

Plan of talk The Past: excellent results from Solar, atmospheric, K2K and KAMLAND. The Future: A Neutrino Factory some time in the future. I will talk about the “bridge” between the past and the Factory. The interest:   , the mass hierarchy, the CP phase  Near Future: T2K NOvA C2GT Reactors Intermediate Future: SPL Beta beams But remember two persisting anomalies in physics: LSND(High mass  to e oscillations) and NuTeV(3  sin 2  W )

Near Future (Accelerators) T2K (Japan) 295km C2GT (CNGS beam) ~1200km NO A (NUMI beam) 810km All three projects are Long Baseline Off-axis projects: Can dial energy of beam To maximum of oscillation They look for   ~ e oscillations by searching for  e appearance in a   beam.

Correlations: 8-fold degeneracy From M. Lindner:       ambiguity   Mass hierarchy two-fold degeneracy     degeneracy: sin 2  23 is what enters in the oscillation formula. For sin2 2  23, say = 0.92, 2  23 is 67 o or 113 o and  23 is 33.5 o or 56.5 (x1.5)  If we just have a lower limit on sin 2 2  23 : all values in between are possible

Matter effects In vacuum and without CP violation: P(   e ) vac = sin 2  23 sin 2 2   sin 2  atm with  atm = 1.27  m 2 32 (L/E) For  m 2 32 = 2.5 x eV 2 and for maximum oscillation: Must have:  atm =  /2 L(km)/E(GeV) = 495 For L = 800km E = 1.64 GeV, For L = 295km E = 0.6 GeV Introducing matter effects, at the first oscillation maximum: P(   e ) mat = [1 +- (2E/E R )] P(   e ) vac with E R = [12 GeV][  m 2 32 /(2.5x10 -3 )][2.8 gm.cm -3 /  ] ~ 12 GeV +- depends on the mass hierarchy. Matter effects grow with energy and therefore with distance. 3 times larger (30%) at NO A (1.64 GeV) than at T2K (0.6 GeV)

T2K Detector 50 ktons (22.5 kton fiducial) Reconstructed Super- K T2K K2K Machine Energy 40 GeV 12 GeV Power(MW) Events(5yr)11000~150 Near detector at 280m to measure flux before oscillation 0.4 % intrinsic e background at peak Must know it well  Data taking 

 13  Sensitivity, correlations But, the limit on sin 2 2   is much worse if we take into account correlations and degeneracies Sin 2 2  13 ~ 0.04  CP 150

T2K II: Hyper-Kamiokande One megaton Water Cerenkov and 4MW accelerator.   +150 o -150 o sin 2 2  13 Improvement by more than an order of magnitude on  13 sensitivity All degeneracies included

T2K II: Sensitivity to  CP Definition: For each value of sin 2 2  13 : The minimum  for which there is a difference Of 3  between CP and NO CP violation Limited by statistics Limited because: CP violation asymmetry (  ) decreases with increasing sin 2 2  13 Sin 2 2  o 50 o 

NO A Detector Given relatively high energy of NUMI beam, decided to optimize NO A  for resolution of the mass hierarchy Detector: 14mrad (12 km) Off-axis of the Fermilab NUMI beam (MINOS). At Ash River near Canadian border (L = 810km) : New site. Above ground. Fully active detector consisting of 15.7m long plastic cells filled with liquid scintillator: Total mass 30 ktons. Each cell is viewed by a looped WLS fibre read by an APD cells

MINOS Near detector events, and Beam The NUMI beam is already functional ! MINOS NEAR detector has observed and reconstructed neutrino events. E Expected proton intensity on target 6.5 x per year greatly helped by cancellation of BTeV and foreseen end of collider programme in Longer term: 8 GeV proton driver: 25 x protons per year: Phase II. If approved in 2006, First kiloton: Full completion: 2011.

3  measurement limits for sin 2 2  13  5 years Phase I (NO proton driver)  m 2 > 0  m 2    m    m   T2K  NO A always MORE sensitive than T2K (about a factor of 1.4)

Mix Neutrinos and Anti neutrinos Comparison with Reactor  Neutrinos and anti neutrinos mix to have a more uniform dependence of the sensitivity on .  Proton driver brings a factor of 2 more sensitivity  Comparison with reactors, shows NO A always MORE sensitive.

Resolution of mass hierarchy  Fraction of  over which the mass hierarchy can be resolved at    qual amounts of neutrino and antineutrino running: 3 years each assuming Phase I.  Near the CHOOZ limit the mass hierarchy can be resolved over 50% of the range of .  T2K can only resolve the hierarchy in a region already excluded by CHOOZ. (Because of its lower energy).  Some small improvement if we combine T2K and NO A results CHOOZ limit T2K

Looking further ahead  With a proton driver, Phase II, the mass hierarchy can be resolved over 75% of  near the CHOOZ limit.  In addition to more protons in Phase II, to resolve hierarchy a second detector at the second oscillation maximum can be considered:   atm = 1.27  m 2 32 (L/E) =   L/E = 1485, a factor of 3 larger than at 1 st max.  For ~ the same distance, E is 3 times smaller:  matter effects are smaller by a factor of 3  50 kton detector at 710 km.  30km off axis (second max.)  6 years (3  + 3 ) Determines mass hierarchy for all values of  down to sin 2 2  13 = 0.02

CERN to Gulf of TARANTO  The CNGS beam continues SOUTH: beyond the Gran Sasso  Goes over the Gulf of Taranto.  A detector in the Gulf would be 40km OFF-AXIS.  And at a distance of ~1200km would be appropriate for the SECOND oscillation maximum.  Immersed in the sea at a depth of 1000m Required  energy:0.8 GeV Implies a modified lower energy CNGS beam Incompatible with OPERA running

CERN to Gulf of TARANTO: C2GT Basic Unit: 380mm diameter HPD with a cube of 5 Si sensors: One on each of 5 faces of cube :Uniform 110 o angular acceptance. Cube 5 Si sensors High pressure glass container Viewing distance of ~ 20m. Fiducial mass: 1.5 Mton Radius 150m 10m x 10m Proton intensity(rep. rate of accel.) and Flux (Proportional  to    make C2GT less competitive Waiting for OPERA completion also a problem

 13 with Reactors  The best limit comes from a reactor experiment: CHOOZ.  Energetically impossible to produce a  from  ’s, in an appearance experiment.  Technique: anti- e disappearance experiment P ee = 1 – sin 2 2  13 sin 2 [(  m 23 2 L)/(4E )] near oscillation maximum Advantage: NO dependence on  CP or on mass hierarchy: No ambiguities. Disadvantage: Cannot determine them! Measured through inverse  decay: e + p = e + + n Measure e + and n (capture in gadolinium or scintillator): Reconstruct energy Look for Distortion of the e energy spectrum Effects are SMALL :Must know e energy spectrum well to control systematics. Solution: Use a FAR detector to search for oscillations (1700m) and a NEAR detector to measure spectrum BEFORE oscillations(170m).

Example: Double Chooz detector Muons VETO (shield) Thickness = 150mm Acrylic Gamma catcher vessel Liquid scint. (R = 1,8m, H = 4 m, t = 8mm) LS + 0,1%Gd LS Acrylic Target vessel Liquid scint+Gd (R=1,2m,h=2,8m, t = 12mm) Non-scintillating Buffer: Water

Systematics Improvements over CHOOZ  Two detectors: Reactor power and cross sections, Energy per fission : Negligible.  Thicker non-scintillating buffer: Smaller singles rate allows e + threshold of 0.5 MeV well below the lowest possible 1.02 MeV. No Uncertainty due to Threshold.  Target mass: Only Relative mass needed. Will be measured by weighing filling vessel Before and After fill. ChoozDouble Chooz Power0.7% Reactor  ’ s 1.9% E/fission 0.6% Det. eff 1.5%0.5% #protons 0.8%0.2% Total 2.7% 0.6%

Schedule and Sensitivity Near det. ready SiteData takingProposalConstruction ?& design Far detector starts Near detector starts Near det. ready Far det. ready 0.02 Importance of Systematics 1% 0.4% 10 x run time only gains x 2 in sensitivity

Superconducting Proton Linac  Power : 4 MW  Kinetic Energy : 2.2 GeV (3.5 GeV)  Repetition Rate: 50 Hz  Spill Length: 11 msec.  Accumulator needed to shorten pulse length.  Target: Liquid Mercury Jet to cope with stress due to high flux.  Focusing: Horn and Reflector optimized for 600 MeV/c particles  Decay Tunnel: 20m long 1m radius  Neutrino energy to be at oscillation maximum for  m 23 2 = 2.5 x eV MeV  Distance: 130km  Location: New lab in Frejus tunnel  Detector mass: 440 kton fiducial.  Type: Water Cerenkov (Super-K)

Optimization of Proton beam energy Angle of emission of Pions (0.5 < p  < 0.7 GeV/c)/s Horn acceptance < 25 o More at GeV. Higher flux. 20% Increase in significance Better sensitivity at 3.5, 4.5 GeV 3.5, 4.5 GeV 2.2 GeV 2.2 GeV J.E. Campagne, A. Cazes hep-ex/

Optimization of the neutrino energy Modify horn Profitable to go to 350 MeV Instead of 260 MeV 350 MeV

Advantage of mixing neutrino and antineutrino running 3.5 and 4.5 GeV proton beam 260 and 350 MeV options 5 years of running. 2 years of running and 8 years of running The limit IMPROVES near  = 90 o

Beta beams Idea introduced by Piero Zucchelli. Accelerate radioactive ions decaying via  + or  -. Because of Lorentz boost, the decay electron neutrinos or antineutrinos will be focused forward into a beam. Look for: Appearance of  or  Advantages: “Clean” beams with no intrinsic  component. Precisely calculable energy spectra. Energy of beam tunable through acceleration of ions.  Accelerate protons in SPL  Impinge on appropriate source  Bunch resulting ions (atmospheric ’ s)  Accelerate ions in PS and SPS.  Store in decay ring. 8 bunches.  Favourite scheme:  6 He 6 Li + e - + e 18 Ne 18 F + e + + e Half lives: 0.8 sec and 0.64 sec. Stored together if  ( 18 Ne) = 1.67  ( 6 He) Detector: Same as for SPL (Frejus)

 sensitivity for  = 60,100 Statistics limited Limited because CP violation Asymmetry decreases with increasing    2% Syst. Unc. 2.9 x He ions and 1.2 x Ne ions per year decaying in straight sections M. Mezzetto SPSC Villars Down to 30 o

Optimization of  J. Burguet-Castell, hep/ph/ and M. Mezetto. Not necessary to store the 2 ion types simultaneously: 4 bunches each. Store 8 bunches of given type at a time and run each type half as long as in joint run. Frees from  ( 18 Ne) = 1.67  ( 6 He) constraint. Assume number of ions stored is INDEPENDENT of energy. Different schemes tried, all leading to higher energies. This is profitable because:  Higher event rates because of larger cross sections.  Better directionality: lower atmospheric background.  Signal events are in a region of lower atmospheric rate.  Fermi motion relatively less of a problem: better correlation between reconstructed and actual neutrino energy.  Can analyze energy dependence of appearance Events instead of just counting them.

Fix baseline at Frejus 99% CL on  improves from > 30 o to > 15 o for a symmetric  scheme. The  13 sensitivity improves a little.  60,100 scheme 6 He 18 Ne CC events  13 =1 o,  =0 o 7118  13 =1 o,  =90 o 4564 Beam back.00 Det. backs o 15 0  = 100  13 = 8 o  = 90 o  

Fix  at maximum SPS value: 150. For this  the optimum distance is 300 km The 99% CL  reach can be improved from 15 o to 10 o. and the  13 sensitivity can also be improved substantially But no existing laboratory at this distance! 300 km       60, km 150, km  sin 2 2  13 L(L( L(km)

Combining SPL and Beta beams The  beam is more sensitive than an SPL beam. The  beam only requires the SPL for 10% of its up time. Can therefore run of an SPL beam at the SAME TIME as the  beams. The combination improves over the  beam alone. SPL +  km  Both  SPL

Systematic uncertainties Must be kept at the 2% level Most important ones:  Target mass difference between near and far detectors.  Uncertainty on  and cross sections (will be measured by near detector)

T2K II vs Beta T2K Phase II and  beam   = 150) have very similar CP reach and sin 2 2  13 sensitivity. sin 2 2  13   T2K II  150 T2K II 

(Personal) Conclusions  Accelerator physicists must be encouraged to produce detailed studies of SPL and  beams scenarios.  Many options are still possible. Some optimizations are only days old. Work in progress.  Double Chooz, could be first to go, but its physics is limited.  T2K, will be next, and will include the physics of the reactor experiment.  NO A, provided it gets an early approval, has the most extensive physics reach, in particular a first look at the mass hierarchy.