Experiments to detect q13 M.Apollonio Universita’ di Trieste e INFN 15/04/2004 IFAE 2004, Torino

Layout of the talk q13 and motivations to its measurement Chooz limit Appearance and disappearance experiments Accelerators (A) Nuclear Reactors (R) (A) Approved projects (Phase I) Phase II Phase III (R) Double-Chooz and similar 15/04/2004 IFAE 2004, Torino

q13 Scenario: MiniBoone disfavouring LSND “standard picture” 2 Dm2ij (Dm212, Dm223) indipendent 3 mixing angles (q12, q23, q13) 1 CP phase Mixing Matrix PMNS 1-2 solar mixing 2-3 atmospheric mixing 1-3 o e3 mixing: q13 describes oscillations ne at the atmospheric frequency dCP  introduces CP violation effects Current experimental results: Dm223 ~ 2x10-3 eV2 Dm212 ~ 7x10-5 eV2 Dm223 >> Dm212 q12~35o q23~45o 15/04/2004 IFAE 2004, Torino

Why measuring q13? The least known among the parameters in PMNS Coupled to eid (Ue3) q13>0 would allow to access d CP violation in the lepton sector 15/04/2004 IFAE 2004, Torino

What do we know about q13 today? q13 must be small (maybe null) The best limit up to date comes from the reactor experiment CHOOZ: q13 < 10o-17o (1.3x10-3<Dm232<3x10-3) [J.Bouchez, NO-VE 2003] [CHOOZ coll., Eur.Phys.J.C27(2003),331-374] 15/04/2004 IFAE 2004, Torino

3 families scenario: appearance experiments Accelerators NB: P sensitive to d (correlated with q13) a should be considered sign(Dm213) is present in A [P.Migliozzi, F.Terranova arXiv:hep-ph/0302274] 15/04/2004 IFAE 2004, Torino

Accelerators general concept: conventional beam Super Beam (SB) Broad band (BBB) Narrow band (NBB) Super Beam (SB) Off-Axis Beam (OA) b-Beam (bB) Neutrino Factory (NF) 15/04/2004 IFAE 2004, Torino

(A) General concept Production & focusing oscillation decay Main backgrounds: Initial ne contamination in the beam p0 production (NC) Near/Far detection Production & focusing oscillation decay (had+m stop) target detection (m,e,t) p p,K nm nm ne nm(>99%) m- e- CC ne nm e- m- ne(<1%) 15/04/2004 IFAE 2004, Torino

(A)-SB It is a conventional proton beam whose power is of the order of MW Produces nm (nm) Proton-driver: technically feasible PB: target Sol.: R&D Proposed rotating tantalum target ring 15/04/2004 IFAE 2004, Torino

(A)-OA Detector laying out of the main beam axis q Kinematics  n beam energy almost independent from Ep Monochromatic  suppresses the high energy tails You pay it in terms of flux Examples: En at 2 different energy scales for Ep at several OA angles q Target Horns Decay Pipe 15/04/2004 IFAE 2004, Torino

(A)b-Beams [P.Zucchelli, Phys.Lett. B532:166,2002] Original solution: radioactive ions with short lifetime acceleration storage decay Es.: b- (6He) ne, b+ (18Ne)  ne 15/04/2004 IFAE 2004, Torino

(A)-NF 15/04/2004 IFAE 2004, Torino

(A) Experiments [J.Bouchez, NO-VE 2003] Phase I: use an existing facility and approved projects (q13>5o) Phase II: go for 1st generation of Super-Beams (q13>2.5o) Phase III: 2nd generation of Super-Beams (q13>1o) [Phase IV: Neutrino Factories see relevant talk] 2006 5o L-Ar 732 20 0.17 ICARUS 7o Emulsion OPERA 2005 Calorimeter 730 3 0.4 MINOS Starting date Sens to q13 detector L (km) E (GeV) Power (MW) Experiment 2018 ? 0.5o WC/L-Ar [500kT] 130 0.3-0.6 0.2 b-Beam ~2015 1o WC/L-Ar [500kT] 0.27 4.0 SPL-SB 2020 ? WC (HyperK) [500kT] 295 0.7 T2K-II (OA) 2009 2.3o WC (SuperK) [20kT] 0.8 T2K (OA) 2008 ? 2.5o Fine grained calorimeter[20kT] 700/900 2 NuMI-OA Phase II Phase III Phase I 15/04/2004 IFAE 2004, Torino

(A) Experiments (cont’d) Requirements for Super-Beams (nmne appearance case) Beam side: Low ne contamination Good knowledge of ne/nm Good understanding of the beam (near to far) Detector side: Good e- efficiency Good p0 rejection Good understanding of bkg 15/04/2004 IFAE 2004, Torino

Which energy? Low or high? Focalisation of neutrinos ~g2~E2 Solid angle factor @ L ~1/g2~1/E2 s(n) ~g~E p flux ~1/g~1/E The 0th order approximation cannot help that much in the choice Other considerations mandatory ~1 15/04/2004 IFAE 2004, Torino

Low (E<1GeV) or High (E>1GeV) ? [choice related to bkg considered] intrinsic ne contamination and p0 mimicking e- WC technique gives a good p0 (NC) vs e- separation (2-ring vs 1-ring) Less ne (below K threshold) Fermi momentum  poor E resolution No matter effects Better use fine grained detectors or L-Ar TPC Need good p0 rejection More ne bkg Better resolution in E Matter effects can arise  sign(Dm213) caveat: stay below t threshold 15/04/2004 IFAE 2004, Torino

Underground or not? In principle not: just a matter of choosing the right (low) duty cycle [phase II, 20 kton] BUT it is a must if your detector is “multi-purpose” (e.g. searching for other effects like proton decay) [phase III, 500 kton] 15/04/2004 IFAE 2004, Torino

Near/Far Best way to determine ne bkg: measure it at a near location (before oscillation) Try to ensure equality of conditions between near and far detectors: i.e. same beam, same target nuclei (cross sections and p0 production do depend on nuclei) Near detector sufficiently far from the source  point-like assumption (~ 2 km) If you go closer then the source is not point-like anymore Near detector able to understand the different n interactions (QE/non-QE) Ideally TWO near detectors (~300 m, ~2 km): One giving a clear clue about n interactions The other as much as identical to the FAR detector 15/04/2004 IFAE 2004, Torino

Near/Far (cont’d): strategies for beam understanding Cheap solution: N sees a point-like source F and N use the same detection technique (1/L2 law) Good for discovery though it does not allow a precise measurement of q13 Beam Near(~2km) Far(700km) N F “Pricey” solution: VN  N1: similar detection techniques allowing beam understanding N1  N2: different in s(n) and detector performances  can be compared F and N2 using the same detection technique Should be optimal for high statistics phase III where you want to reduce systematics (less dramatic for phase II) N1 Beam V-Near(300m) Near(~2km) Far(700km) F VN N2 15/04/2004 IFAE 2004, Torino

T2K [I/II] OA: q~2o, JHF-PS(50 GeV p) SK[I]  HK[II] 50 kton Water Cherenkov T2K [I/II] Eπ vs. Eν 0.0゜ 1.0゜ 1.5゜ 2.0゜ 3.0゜ 5.0゜ OA: q~2o, JHF-PS(50 GeV p) SK[I]  HK[II] Maximize the potential discovery (on-peak)  d,q13,sign(Dm132) L~295 km, <E>~0.76GeV  on peak |A|~5x10-2  matter effects negligible Phase I: use SK detector (20 kton) Phase II: go for a more ambitious device  HK (500 kton) Max. osc. energy for 3×10-3eV2 OA3° OA2° OA1° 2200 CC νμ　/ year 800 CC νμ　/ year 15/04/2004 IFAE 2004, Torino

μ ν Muon detector Water Cherenkov detector Total mass : 1000ton Fid. Mass : 100ton ν beam Fine grained scintillater detector 5m 8m Water Cherenkov detector Muon detector p n 140m 0m 280m 2 km 295 km μ ν 15/04/2004 IFAE 2004, Torino

SuperKamiokande Water Cerenkov detector Sub-GeV  good p0/el. separation q13: 2.5o sensitivity after 5 yrs of data taking SK-90%CL allowed OAB (2degree) K-decay m-decay nm ne 0.2% Signal for non-zero θ13 in JHF-SK (νμ→νe) BG (NC π0 ….) T. Kajita, Fermilab – May 2003 15/04/2004 IFAE 2004, Torino