Future Neutrino Facilities: Beta Beams and the Neutrino Factory

1. SPL, Beta beams and the Neutrino Factory. Leslie Camilleri NuSAG 20th May 2006

2. What’s needed next? • Determine q13. Plans for several experiments using reactors, accelerators, etc… • Determine the mass hierarchy. Some of these experiments, specially if extended through the use of upgraded accelerators, would address this. • Any CP violation in the neutrino sector? A new neutrino facility (a neutrino factory or a beta-beam complex) would be the only sure way to address this problem.

3. Acknowledgments • Beta Beams: Mats Lindroos, Mauro Mezzetto, J-E. Campagne. • Neutrino Factories. Alain Blondel, Talks based on April 2006 International Scoping Studymeeting at RAL. Presentations by: • Bob Palmer on machine • Paul Soler on Detectors • Yori Nagashima on Physics • Roland Garoby and his team

4. European efforts on Future Neutrino Facilities • Superconducting Proton Linac (SPL). • Beta-beams. Conceptual designfor a Nuclear Physics facility (ISOLDE type): Eurisol financed by European Union . Includes beta-beam studies. Synergy with beta-beams (radioactive ions): Proton driver, high power targets, beam cleaning ionization and bunching First stage acceleration , radiation issues. Will it be at CERN ? Decision in 2010. • Neutrino Factory The ultimate. Study under way through the International Scoping Study. • R&D on targets (MERIT) and muon cooling (MICE).

5. Evolution of the CERN accelerator complex:- Proposed combinations Proton flux / Beam power Linac4 Linac2 *1 50 MeV 160 MeV *3 PSB SPL’ RCPSB SPL 1.4 GeV ~ 5 GeV PS *2 26 GeV PS2 (PS2+) 40 – 60 GeV SPL: Superconducting Proton Linac (~ 5 GeV) SPL’: RCPSB injector (0.16 to 0.4-1 GeV) RCPSB: Rapid Cycling PSB (0.4-1 to ~ 5 GeV) PS2: High Energy PS (~ 5 to 50 GeV – 0.3 Hz) PS2+:Superconducting PS (~ 5 to 50 GeV – 0.3 Hz) SPS+: Superconducting SPS (50 to1000 GeV) DLHC: “Double energy” LHC (1 to ~14 TeV) Output energy SPS SPS+ *4 450 GeV 1 TeV LHC DLHC 7 TeV ~ 14 TeV Priorities will be driven by LHC upgrade: *1,*2,*3,*4

6. Superconducting Proton Linac • Power : 4 MW • Kin. Ener. : Up to 5 GeV. More p’s. • Repetition Rate: 50 Hz • Accumulator to shorten pulse length. (Reduce atmospheric n’s contam.) • Target: Liquid Mercury Jet to cope with stress due to high flux. • Focusing: Horn and Reflectoroptimized for 600 MeV/c particles • Detector: New lab in Frejus tunnel • (Safety gallery approved April 2006: opportunity) • Distance: 130km • Neutrino energy to be at oscillation maximum for Dm232 = 2.5 x 10-3 eV2260 MeV  350 MeV more sensitive • Detector mass: 440 kton fiducial. • Type: Water Cerenkov(Super-K)

7. MEMPHYS at Fréjus Up to 5 shafts possible Each 57m diam., 57m high For most studies assumed 3 x 145 ktons. Water Cerenkov Depth: 4800 m.w.e FOR 100 ktons) Per shaft: 81,000 12” PMT’s  80 M€ including electronics (65M$ KL 62M$ ) +80 M€ for civil engineering. (65M$ KL 29M$ )

8. Advantage of mixing neutrino and antineutrino running • 3.5 and 4.5 GeV proton beam • 260 and 350 MeV options • 5 years of n running. • 2 years of n running and 8 years of n running The curves flatten.  about 0.001.

9. Idea introduced by Piero Zucchelli. Accelerate radioactive ions decaying via b+ or b-. Because of Lorentz boost, the decay electron neutrinos or antineutrinos will be focused forward into a beam. Look for: Appearance of nm ornm Advantages: “Clean” beams with no intrinsicnmcomponent. No need for magnet. Precisely calculable energy spectra. Energy of beam tunable through acceleration of ions. • Accelerate protons in SPL • Impinge on appropriate source • Bunch resulting ions(atmospheric n’s !) • Accelerate ions in PS and SPS. • Store in decay ring. 8 bunches. • 6He 6Li + e- + ne 18Ne 18F + e+ + ne Half lives: 0.8 sec and 0.64 sec. Stored together if g(18Ne) = 1.67 g(6He) En= (3 MeV) x g = 200 – 500 MeV Detector: Same as for SPL (Frejus) Beta beams • Very attractive because: • Eurisol radioactive beam project for nuclear physics possibly at CERN.. • PS and SPS exist.

10. 6He production by 9Be(n,a) Converter technology: J. Nolen et al., NPA 701 (2002) 312c. need 100μA at 2.0 GeV for needed beta-beam flux For 18Ne: Proton beam into Magnesium oxide: Produce 18Ne directly by spallation Source must be hot for 18Ne to diffuse out. Cannot cool it. Limits beam and rate.

11. Production Production ring with ionization cooling • Major challenge for 18Ne But new production method: C. Rubbia et al. D2 • D2 gasjet in storage ring. • Inject ions (19F) and store • Go through jet repeatedly increases probability to form radioactive ions • Regain energy loss with RF • High energy ions have smaller dE/dx than low energy ones. But will gain same amount from RFeven more energy • To compensate shape jet (fan) such that high energy ions (larger radius) traverse more material. • Longitudinal cooling. High E Low E

12. d sensitivity for g = 60,100 En= (3 MeV) x g = 200 – 500 MeV M. Mezzetto SPSC Villars Statistics limited 2% Syst. Unc. CP violation Asymmetry decreases with increasing q13 Down to 30o 2.9 x 10186He ions and 1.2 x 1018 18Ne ions per year decaying in straight sections

13. Optimization of g • J. Burguet-Castell, hep/ph/0503021 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 g(18Ne) = 1.67 g(6He) constraint. • 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.

14. g = 60,100 scheme Fix baseline at Frejus 30o 150 q13 = 8o g= 100 • 99% CL on d improves from > 30o to > 15ofor a symmetric g > 100 scheme. • The q13sensitivity improves a little. d = 90o d = -90o

15. Fix g at maximum SPS value: 150. d q13 = 8o 300 km • For this g the optimum distance is 300 km • The 99% CL dreach can be improved from 15oto 10o. • and the q13 sensitivity can also be improved substantially But no existing laboratory at this distance! 10o L(km) L( 60,100 130km sin22q13 150,150 300km

16. Optimize for Gran Sasso • Optimize g for the a detector at the Gran Sasso (730km). • g = 350.  Needs new SPS. 350,350 730km 300 km Standard Frejus Gran Sasso

17. SPL, Beta-beam (g=100), T2HK comparisons J-E. Campagne et al hep/ph0603172 v1 • Mass: Each detector: 440 ktons , • Running time: SPL and T2HK: 2 yrs n+ 8 yrs n . Beta-beam: 5 yrs + 5 yrs. • Systematics: 2% - 5%. 3s discovery potential on sin2 2q13 3s discovery potential on CP viol. (Excluding d=0,p) 5% 2% 2%

18. Invoking CPT Replace beta beam ne by SPL nm Run simultaneously for A total of 5 yrs only. P(ne  nm) = P(nm  ne) 3s discovery Comparable to T2HK 10 yrs.

19. Mass Hierarchy Use atmospheric neutrinos (ATM) observed in MEMPHYS, in conjunction with SPL, beta and T2HK beams. Makes up for small matter effects due to short baseline With ATM

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

21. ??? Uncertainty on n cross-sections. Targets: free nucleons and water Below 250 MeV: Very uncertain At 250 MeV: Double ratio ~ 0.9 Nuclear effects ~ 5% How well do we know these?

22. New idea: Electron capture in 150Dy J. Bernabeu et al hep-ph/0605132 Atomic electron captured by proton in nucleus (A,Z) + e- (A,Z-1) + ne For instance: Dysprosium. Advantage: monochromatic nebeam • Partly stripped ions: The loss due to stripping smaller than 5% per minute in the decay ring • Possible to produce 1 1011 150Dy atoms/second (1+) with 50 microAmps proton beam with existing technology (TRIUMF). • Problem: long lived 7 minutes. • An annual rate of 1018 decays along one straight section seems a challenging target value for a design study • Beyond EURISOL Design Study: Who will do the design? • Is 150Dy the best isotope?

23. Potential of electron capture beams Run 5 years each at g=90 and g=195 440 ktons at Fréjus d = 90 d = 0 d = -90 5 test points 100 500 MeV CP dependence of nmne oscillationprobability

24. Year 2005 2010 2015 2020 Safety tunnel Excavation Lab cavity P.S Study Excavation detector PM R&D PMT production Outside lab. Installation Det.preparation P-decay, SN Non-acc.physics Superbeam Construction Superbeam betabeam Construction Beta beam A possible schedule for a European Lab. at Frejus decision for cavity digging decision for SPL construction decision for EURISOL site ???

25. Neutrino Factory Mandate of the International Scoping Study Being studied in the context of the International Scoping Study The InternationalScoping Study of a future accelerator neutrino complex will be carried by the international community between NuFact05, Frascati, 21-26 June 2005, and NuFact06, August 2006. The physics case for the facility will be evaluated and options for the accelerator complex and neutrino detection systems will be studied. Its reach and feasibility will be compared to the Beta-beam and SPL options. The principal objective of the study will be to lay the foundations for a full conceptual-design study of the facility.

26. WHO ? International effort: • The ECFA/BENE network in Europe. • The Japanese NuFact-J collaboration. • The US Muon Collider and Neutrino Factory Collaboration. • The UK Neutrino Factory collaboration. CCLRC's Rutherford Appleton Laboratory will be the 'host laboratory' for the Study. (The effort was initiated by the UK).

27. Simplified Neutrino Factory 1.2 1014 m/s =1.2 1021 m/yr 1016p/s Pion production target Ion source Pion to muon decay and beam cooling Muon accelerator Proton accelerator 9 x 1020 m/yr Muon-to-neutrino decay ring m+ e+ne nm 3 x 1020 ne/yr 3 x 1020 nm/yr per straight section Detector Earth’s interior

28. Principle of detection Look for ne nmoscillations using ne from m decay (Golden channel) 2 baselines or 2 energies to resolve ambiguities m+ e+nmne oscillates ne nm interacts givingm- WRONG SIGN MUON interacts giving m+ Need to measure m charge Magnetic detector Other channels: • Platinum channel: nm ne T violation. • Silver channel:ne  nt Resolve ambiguities.

29. Triangle or Race-track? Or else too many decays In 3rd “useless” leg. Minimum length of 3rd leg for given angle is when ring is vertical ~ 400m. Limited by geology If two far sites needed

30. Decisions taken at April ISS meeting Allows simultaneous collection of m+ and m-. instead of solid instead of horn 1021 (m+ + m-) decays per year Half per straight section

31. Knowledge of Matter density along n path Lithosphere: solid,heterogeneous 2500 km asthenosphere: Viscous, homogeneous “Best” 2s errors 1.5-3% Avoid: Alps, Central Europe Favour:Western Europe to US Atlantic Islands Oceans: simpler, more accurate. Continents: more complicated, less accurate.

32. Usefulness of the silver channel: ne nt Fine grained detector for t secondary vertex or kink: OPERA technology S. Rigolin, hep-ph/0407009 D. Autiero et al. hep-ph/0305185 ne nt andne nmchannels have “opposite” sign CP violation. n n 3000kmand 730km ne ntandne  nm Clones for 2 reactions are also at different positions. Clones at 2 baselines are at different positions Alternative to 2 baselines?

33. Detectors • Magnetized iron/scintillator. • Fully active scintillator + External magnetic field. • Water Cerenkov • Liquid argon in solenoidal field. • Hybrid emulsion detector in a magnetic field (Electron charge). • Near Detectors.

34. 1 cm Iron sheets Planes of triangular 4cm x 6 cm PVC tubes. Filled with liquid scintillator Read by looped WLS fibres Connected to APD’s. 60kA-turn central coil 0.5m x 0.5m Average field of 1.5T Extrapolation of MINOS Structure based on NOvA using MINERvA-like shapes Based on 175M$ for 90kt A Strawman Concept for a Nufact Iron Tracker Detector

35. Fully active detector (NOnA) with external magnetic field NOnA divided longitudinally into 10 sections Each section surrounded by low field solenoid. 10 solenoids next to each other. Horizontal field perpendicular to beam Each: 750 turns, 4500 amps, 0.2 Tesla. 42 MJoules . 5Meuros. Total: 420 MJoules (CMS: 2700 MJoules) Coil: Aluminium (Alain: LN2 cooled). 750 turns n B Problem: Periodic coil material every 15m: Increase length of solenoid along beam? How thick?

36. Giant Liquid Argon Charge Imaging Experiment US-Europe Synergy ? Impression was that magnet limited detector mass to 15 ktons. A. Rubbia

37. 1 mm t n Pb Emulsion layers DONUT/OPERA type target +Emulsion spectrometer Must be placed in a magnet B Air Gap Film Stainless steel or Lead ~ 3Xo ~10Xo Can measure momentum of muons and of some fraction of electrons Identify t usingtopology

38. Comparison of beta-beam and n factory Beta-beam advantages. • Synergy with Eurisol (if at CERN) + existing PS,SPS • Cost ? • Clean ne and ne beams: no need for magnet. • Negligible matter effects. (But hierarchy?) • Does not need 4 MW of power. (But if SPL is needed for better sensitivity…?) • Beta-beam disadvantages • Low energy: Cross sections not so well known, muon mass effect Fermi motion Atmospheric neutrinos background • Silver channel energetically impossible • Need of SPL: Improve sensitivity Measure ncross-sections

39. Comparison of beta-beam and n factory II Advantages of Neutrino Factory • Ultimate reach • Smaller systematic errors • Presence of both nmand ne in beam allows measurement of cross-sections in near detector • Higher energies: better measured cross sections. Disadvantages of Neutrino Factory. • Technically more challenging • Cost • Deeper tunnel limits sites. • Matter effects must be well understood. Baselines carefully chosen. • Need for a magnetic detector to separate signal from background

40. Reach of beta-beams and n Factory About the same for other 4 quadrants of CP phase. Beta-beams and beta-beams + SPL Are better for sin2 2q13 > 0.01. (needs confirmation: cuts used in analysis Em > 5 GeV) Below this value n factory is more sensitive.

41. MERIT: Hg jet target tests at CERN PS • Test performed in magnetic field (15T) • To simulate actual conditions: • collection solenoid Proton intensity: 2 x 1013 protons/pulse at 24 GeV 1cm diameter jet at small angle(40 mrad) to beam to maximize overlap: 2 inter. lengths. Aims: Proof of principle. Jet dispersal. Effect of field on jet flow and dispersal. Scheduled to run in Spring 2007

42. MICE: Muon cooling experiment at RAL Prove the feasibility of ionization cooling. Strong synergy with MUCOOL.

43. MICE:planning

44. Problems: a personal view. CERN: The priority will be given to a) Consolidation of existing machines. b) LHC luminosity upgrades, including whatever replacement machines it takes, including Nb3Sn IR quads. c) Possibly an energy upgrade of LHC. Nb3Sn dipoles ? d) Ongoing CLIC R&D. Internationally: a) ILC schedule, cost and site. b) Difficult to conceive the next big n project going ahead without having already measured q13. When will this be?

45. Time line 2010: A critical year in many ways. • Possible ILC decision. • CLIC possibilities. • LHC results. • Decision on LHC upgrade. • Eurisol siting. CERN ? • Possible first measurement of q13: MINOS, Double CHOOZ

47. Storing of both charges at once l l- l+ m+m- Muons of both signs circulate in opposite directions in the same ring. The two straight sections point to the same far detector(s). OK d Discriminate events On the basis of timing (d) Detector

48. Some decisions taken at April ISS meeting