Università di Roma III 27 Gennaio 2003 L.Ludovici INFN Roma I Prospettive Sperimentali della Fisica delle Oscillazioni di Neutrini Scenario attuale LCPV - Factory 13 – Superbeam Presente Futuro Remoto Futuro Prossimo

2 Short Abstract... Long-term goal: Leptonic CPV at the Factory Uncertain perspective: technology, cost, physics. Mid-term goal: 13 discovery LMA ? 13 large? CPV already found ? Factory Doubtful... Only if Coll

Cited papers EVIDENCE FOR OSCILLATION OF ATMOSPHERIC NEUTRINOS Super-Kamiokande Collaboration (Y. Fukuda et al.). Phys.Rev.Lett.81:1562 (1998) hep-ex/ OBSERVATION OF TOP QUARK PRODUCTION IN ANTI-P P COLLISIONS CDF Collaboration (F. Abe et al.). Phys.Rev.Lett.74:2626 (1995) hep-ex/ OBSERVATION OF THE TOP QUARK. D0 Collaboration (S. Abachi et al.). Phys.Rev.Lett.74:2632 (1995) hep-ex/ ATMOSPHERIC / e RATIO IN THE MULTIGEV ENERGY RANGE Kamiokande Collaboration (Y. Fukuda et al.). Phys.Lett.B335:237 (1994) INITIAL RESULTS FROM THE CHOOZ LONG BASELINE REACTOR NEUTRINO OSCILLATION EXPERIMENT. CHOOZ Collaboration (M. Apollonio et al.). Phys.Lett.B420:397 (1998) hep-ex/ OBSERVATION OF A SMALL ATMOSPHERIC / e RATIO IN KAMIOKANDE. Kamiokande-II Collaboration (K.S. Hirata et al.). Phys.Lett.B280:146 (1992) FIRST MEASUREMENT OF THE RATE FOR THE INCLUSIVE RADIATIVE PENGUIN DECAY b s. CLEO Collaboration (M.S. Alam et al.). Phys.Rev.Lett.74:2885 (1995)611 8.LIMITS ON NEUTRINO OSCILLATIONS FROM THE CHOOZ EXPERIMENT. CHOOZ Collaboration (M. Apollonio et al.). Phys.Lett.B466:415 (1999) hep-ex/ EVIDENCE FOR e OSCILLATIONS FROM THE LSND EXPERIMENT AT LAMPF. LSND Collaboration (C. Athanassopoulos et al.). Phys.Rev.Lett.77:3082 (1996) nucl-ex/ EVIDENCE FOR TOP QUARK PRODUCTION IN p p COLLISIONS AT S 1/2 = 1.8-TeV. CDF Collaboration (F. Abe et al.). Phys.Rev.D50:2966 (1994) MEASUREMENT OF A SMALL ATMOSPHERIC MUON-NEUTRINO / ELECTRON-NEUTRINO RATIO. Super-Kamiokande Collaboration (Y. Fukuda et al.).Phys.Lett.B433:9 (1998) hep-ex/ MEASUREMENT OF THE RATE OF e + d p + p + e- INTERACTIONS PRODUCED BY B 8 SOLAR NEUTRINOS AT THE SUDBURY NEUTRINO OBSERVATORY. SNO Collaboration (Q.R. Ahmad et al.). Phys.Rev.Lett.87: (2001) nucl-ex/ STUDY OF THE ATMOSPHERIC NEUTRINO FLUX IN THE MULTI-GEV ENERGY RANGE. Super-Kamiokande Collaboration (Y. Fukuda et al.). Phys.Lett.B436:33 (1998) hep-ex/ MEASUREMENT OF THE SOLAR ELECTRON NEUTRINO FLUX WITH THE HOMESTAKE CHLORINE DETECTOR. Bruce T. Cleveland et al. Astrophys.J.496:505 (1998) THE e AND CONTENT OF THE ATMOSPHERIC FLUX. R. Becker-Szendy et al (IMB Coll.) Phys.Rev.D46:3720 (1992) 521

4 Present evidences of neutrino mass and mixing e, with m eV 2, almost (not fully) maximal mixing. and/or NC appearance from the Sun in SNO. 2.Lab Test: reactor e disappearance at L 200Km in Kamland (4.6 ) with m 2 = ( ) eV 2, sin 2 2 > 0.92 at 90%CL 1.Super-K upward-going atmospheric disappearance. 2.Most likely from o and matter effects in Super-K (2÷3 ) 3.Lab Test: disappearance in accelerator from K2K-I (2÷3 ) e with m 2 ~ 0.1 eV 2 1.LSND claimed evidence of neutrino oscillation. 2.Unseen by KARMEN with marginal sensitivity 3.Controversy to be solved by Mini-BooNE (results in )

C 23 S S 23 C 23 C 13 0 S 13 e i S 13 e -i 0 C 13 C 12 S S 12 C U = U A. U 13. U S = 3 neutrinos 2 mass differences, 3 angles and 1 CP phase m 2 12 m atmospheric solar ?? The Mixing Matrix e = U i pure flavour eigenstate back to flavour eigenstates each mass eigenstate takes a different phase jk = m 2 jk (eV 2 )L(Km)/E (GeV), W = U j U j U k U k P( ) = - 4 Re [ W ] sin 2 jk 2 Im [ W ] sin 2 jk ( ) jk k>j ( ) jk CP odd jk

6 Knowledge of mixing parameters Solar do mix. NC appearance in SNO Lab confirmation:claim of disappearance in KamLand Atmospheric disappear. Up/Down asymmetry in Super-K Lab confirmation:indication of disappearance in K2K e Negative result in CHOOZ m 2 23 = m 2 atm eV 2 m 2 12 = m 2 sun or eV o o 13 < 13 o No idea. <

7 For experiments at terrestrial baselines, with 12 <<1: P( e ) sin sin 2 23 sin 2 23 = sin 2 2 e sin 2 23 P( ) cos 4 13 sin sin 2 23 = sin 2 2 sin 2 23 P( e ) sin cos 2 23 sin 2 23 = P( ) 1 – (sin sin 2 2 e ) sin 2 23 P( e e ) sin sin 2 23 Only 3 parameters: 23 m Reduce to two flavour mixings with effective mixing angles: sin 2 2 = cos 4 13 sin sin sin 2 2 e = sin sin sin Effective Mixing Angles jk = m 2 jk (eV 2 )L(Km)/E (GeV), W = U j U j U k U k P( ) = - 4 Re [ W ] sin 2 jk 2 Im [ W ] sin 2 jk ( ) jk k>j ( ) jk CP odd jk

8 LCP Asymmetry Being 13 small, if m 2 12 is only times smaller than m 2 23 (LMA): P( e ) sin 2 23 sin sin cos 2 23 sin sin J 12 sin 13 cos( - 13 ) J = cos 13 sin2 12 sin2 23 sin2 13 large large large ?? ( ) LCP asymmetry vanishes for small 13. atmospheric solar interference J determinant e gives the best opportunity for LCPV due to the suppression of the leading CP conserving contributions Discovery of non-zero 13 is a pre-requisite of any sensible experimental strategy to attack the difficult problem of LCPV.

9 -FactoryKosharev 1974 Wojcicki 1974 Collins 1975 Geer colliderBudker 1969 Skrinski 1971 Neuffer 1979 SBL ( Km) LBL ( Km) VLBL (1 2 R EARTH ) kt Mass Detector SR e ( e ) + ( - ) ( ) Conventional pion beams are dominantly ( ) with a few percent contaminations of ( ) e e. Difficult to access all transitions and oscillation parameters are measured with uncertainty O(10%) while NuFact beams could allow O(1%) precision. E /m The Neutrino Factory Idea

10 E = 5,10,20,40 GeV L = 1000 Km e P. Lipari, hep-ph/ Well known flux ( decay kinematic, polarisation) Clean beam composition: 1:1 + e (or + e ) Flux scales with N E 2 /L 2 Average neutrino energy scales with E Interaction rate scales with M DET N E 3 /L 2 (y) = 2y 2 (3-2y) (y) (1-y) e (y) = 12y 2 (1-y) (y) (1-y) dN E 2 N dydS m 2 L 2 =0 (y) Neutrino Factory Fluxes E (GeV) cm E (GeV) cm 2

11 2 possible ways:A e = A e = Earth is CP-odd. In LBL and VLBL experiments (L>1000 Km) the effects of propagation in matter are in general large and P( ) P( ) even if CP is conserved. P( e ) - P( e ) P( e ) + P( e ) P( e ) - P( e ) P( e ) + P( e ) CP T A CP at NuFact comparing wrong sign - in a beam from + with the charge conjugate process and beam. Need subtraction of matter induced CP effects (two detectors at different baselines). Need precise knowledge of the relative neutrino (anti-) cross-sections. A T free from matter induced effects but it requires the lepton ID and charge determination not only for muons but also for electrons, very difficult in practice in a large O(50Kt) detector. LCPV at the Factory

12 Roadmap NOW K2K-II JHF ? Off-Axis HARP MICE ? Factory ? JHF-HK CNGS NuMI disappearance down to 1 o appearance NC/CC LCP violation down to 0.1 o LCP violation F R&D MiniBooNE LSND? KamLand m 2 12, 12 at 2%

13 JHF Physics Programme High intensity neutrino beam from JHF (0.75 MW) to Super-K (50kt) 1. Discovery of 13 down to sin > Precision measurement of sin and m Search for sterile components through NC interactions Phase I JHF upgrade to 4 MW power. Construction of Hyper-K (1Mt) 1. Discovery of 13 down to sin > Leptonic CP violation. down to degrees if sin > 0.01 Phase II

14 JHF facility Energy(GeV) Current( A) KEK-JAERI joint project 295 Km from Super-K (60Km NE of KEK) Construction Cost: 1335(1890) Oku Yen (1 Oku=10 8 ) JHFK2KNuMICNGS E(GeV) Intensity (10 12 ppp) Rate (Hz) Power (MW)

15 Off-Axis neutrino Beams Horns Target Decay Pipe Detector BNL proposal E889 E = m 2 – m 2 2 (E - p cos ) m 2 – m 2 m 2 ( ) E E >>m, and <<1 Much higher flux than old-style NBB. Strong cut-off of HE tail. Reduced e contamination. Tune energy to maximise sensitivity = m 2 (eV 2 ). L(Km) / E(GeV) Beam energy almost fixed by geometry = L 2 1 m E 2 ( ) 2 1 L 2 1 (E - p cos ) 2 m 2

16 JHF Beam =1 o =2 o =3 o Beam steering angle 2.5 o 0.5 o. Tune energy between 0.4 and 1 GeV Best tuning to m 2 =(1.6 4) eV 2 BeamE peak Flux ( 10 6 /cm 2 /yr) e / (%) All, CC events (events/22.5kt/yr) e e OA2 o OA3 o ppp at Hz (0.75 MW, 2.64 MJ/pulse) pot/yr in 130 days/yr SC proton transport line Carbon target Secondary pions focused by horns Decay pipe 130m length from target Near detector at 280m from target Intermediate detector at 1.5Km Super-K at 295 Km. (22.5 kt fiducial)

17 JHF Near Detectors Flux. L Super-K Flux. L 1.5 Km Flux. L 0.28 Km Covers from 0 o to 3 o. Monitor the beam stability and flux. High rate: 60 events/kt/spill. Study and e interactions: CCQE, CC, NC. Non point-like source, different target, different detector technology: flux extrapolation to Super-K problem. Off-Axis as Super-K Water-Cherenkov (100t fiducial mass) to cancel most of the flux extrapolation syst. Spectrum differences < 10% 2% systematic due to e background subtraction. 60% difference Better than 10% Intermediate detector at 1.5 Km Near detector at 280 m

18 Detector at 1.5Km Conceptual design.

19 Far detector

20 Neutrino Energy Measure =80MeV Ereco - Etrue (MeV) Etrue (MeV) Ereco (MeV) non-QE background CCQE E rec = m n E l – m l 2 /2 m n – E l + P l cos l Almost exact (Fermi motion) for QE interactions: l n l p non-QE CC interactions of higher energy neutrinos background for disappearance Coherent o production from NC interactions of higher energy neutrinos is a background for e appearance

21 13 ( e appearance) CC NCBeam e Oscillated e Events in FV Ring e-like e/ o separation GeV<E<1.2GeV Forward cut 2. high inv.mass cut rings likelihood cut 4. Ring balance cut e/ o separation m 2 = sin 2 13 =0.1

22 13 sensitivity

23 m 23, 23 ( disappearance) Fit with: P( ) = 1 - sin cos 4 13 sin 2 23 Measured spectrum in Super-K: Muon-like FC events in SK Neutrino energy reconstruction Subtraction of non-QE backg. Non-oscillated spectrum: Muon-like events in Near Detec. Neutrino energy reconstruction Subtraction of non-QE backg. Near-Far extrapolation Survival probability Measured/Non-Oscillated 22.5kt x 5 year Oscillation pattern clearly visible High precision determination: sin = 0.01 m 2 23 = eV 2 m 2 sin 2 2

24 Search for sterile neutrinos NC interactions sensitive to all active neutrinos. Together with and e, NC provide a measurement of and s. NC selection of single o, lepton-less events: N N o 90%CL bands Expected single o events 22.5kt x 5 year o production cross-section accurately measured (better than 5%) in the near detectors. No way to reconstruct the neutrino energy. Narrow Band neutrino beam essential.

25 JHF-II (>2012) MW beam power 50 kt 1 Mt water Cherenkov (Hyper-Kamiokande) 3x10 5 events/year Leptonic CPV

26 CPV Sensitivity of JHF-II Stat+BG 10%syst Stat+BG 5%syst Stat+BG 2%syst Stat+BG no syst Stat. Only. No BG 13 excluded by CHOOZ 13 not reachable by JHF-I sin Sin If JHF-I discovers non-zero 13, than JHF-II will be sensitive to LCPV down to =10-20 degrees. P( e ) - P( e ) P( e ) + P( e ) CP A e = = m 2 12 L 4 E sin sin 13 sin.. (without matter effects)

27 Status of JHF La costruzione di JHF è iniziata nel 2001 e il primo fascio è atteso nel La fase-I (0.75MW) è approvata e finanziata (oltre 1M). Il programma di neutrini è una delle principali motivazioni per la costruzione della facility. Lapprovazione e il finanziamento della neutrino beam-line è atteso per questa estate in Giappone (MEXT). Una prima LoI è apparsa nel Nel 2002 si sono tenuti due workshop internazionali, con partecipanti da Giappone, Canada, Francia, Italia, Corea, Russia, Spagna, UK e USA. Sono stati formati dei working groups internazionali. Una LoI aggiornata è stata inviata nel gennaio 2003, firmata da istituti in Giappone, Canada, Francia, Italia (Bari,Napoli,Padova,Roma I), Corea, Polonia, Russia, Spagna, Svizzera, UK and USA. JHFn è il progetto più interessante per scala dei tempi, strategia sperimentale, flessibilità e ricchezza del programma scientifico. La partecipazione italiana deve rafforzarsi per contribuire in modo rilevante e visibile.

28 Conclusioni La fisica delle oscillazioni di neutrini vive anni di importanti risultati. I neutrini solari oscillano. Evidenza di neutrini attivi non- e dal sole. Conferma da una sorgente artificiale. Forte indicazione di sparizione dei atmosferici. Conferma (non conclusiva) da una sorgente artificiale. K2K-II: Conferma sparizione. Pattern di oscillazione. NuMi: NC/CC, sterili/tau CNGS: apparizione diretta di tau MiniBooNE:LSND? Ricerca di 13. Segno di m 2 23 (gerarchia) ?. Misura di precisione dei parametri (GUT test, mass models,...) Finora Next (qualche anno) Next 2 (entro il decennio) Leptonic CP violation. Test del triangolo di unitarietà Next 3 (....)

29 Roadmap NOW K2K-II JHF ? Off-Axis HARP MICE ? Factory ? JHF-HK CNGS NuMI disappearance down to 1 o appearance NC/CC LCP violation down to 0.1 o LCP violation F R&D MiniBooNE LSND? KamLand m 2 12, 12 at 2%