1. BETA-BEAMS 363 days after Piero Zucchelli - CERN M. Mezzetto D. Casper M. Lindroos U. Koester S. Hancock B. Autin M. Benedikt H. Haseroth M. Grieser A. Jansson S. Russenschuck F. Wenander Physics Letters B 532 (3-4) (2002) pp. 166-172

2. GUIDELINES A. Neutrino beams from a different perspective B. The “Beta-Beam” Concept C. Experimental Scenario D. Beta-beams and neutrino physics E. Feasible? Cost-effective? Competitive? Current talk, previous talks, tables, sources: http://cern.ch/Piero.Zucchelli/files/betabeam. A Website by this summer.

3. The focussing properties are given only by: - the divergence of the parent “beam” - the Lorentz transformations between different frames P T = p T P L =  ( p + p  cos  ) from which, on average  1/  (it depends ONLY on parent speed!) E  E 0 and, in the forward direction, E  2  E 0 (same rest-frame spectrum shape multiplied by 2  ) Focussing Properties  parent are produced by weak “decay” of a parent: ,K,nucleus. We assume the decay to be isotropic at rest and call E 0 the rest frame energy of the neutrino.

4. LBL Scope maximum neutrino flux for a given  m 2  E/L  E 0 /L. The neutrino flux onto a “far” detector goes like  2 /L 2 ; Therefore  (  m 2 ) 2 /E 0 2. At a given parent intensity, low energy decays in the CMS frame are the most efficient in achieving the “LBL requirement”, and independently of the  factor. But we want to observe neutrino interactions: N=  If we assume to be in the regime where  E (>300 MeV for  ) N  (  m 2 ) 2  /E 0 And acceleration enters into the game; The “Quality Factor” of a “non-conventional” neutrino beam is therefore  /E 0

5. The BETA-BEAM 1. Produce a Radioactive Ion with a short beta-decay lifetime 2. Accelerate the ion in a conventional way (PS) to “high” energy 3. Store the ion in a decay ring with straight sections. 4. It will decay. e ( e ) will be produced. - SINGLE flavour - Known spectrum - Known intensity - Focussed - Low energy - “Better” Beam of e ( e ) The “quality factor” QF=  /E 0 is bigger than in a conventional neutrino factory. In addition, ion production and collection is easier. Then, 500000X more time to accelerate. Muons:  ~500 E 0 ~34 MeV QF~15 6 He Beta-:  ~150 E 0 ~1.9 MeV QF~79 18 Ne Beta+:  ~250 E 0 ~1.86 MeV QF~135

6. Possible  - emitters ( e )

7. Possible  + emitters ( e )

8. Anti-Neutrino Source Consider 6 He ++  6 Li +++ e e - E 0  3.5078 MeV T/2  0.8067 s 1. The ion is spinless, and therefore decays at rest are isotropic. 2. It can be produced at high rates, I.e. 5E13 6 He/s 3. The neutrino spectrum is known on the basis of the electron spectrum. DATA and theory: =1.578 MeV =1.937 MeV RMS/ =37% B.M. Rustand and S.L. Ruby, Phys.Rev. 97 (1955) 991 B.W. Ridley Nucl.Phys. 25 (1961) 483

9. Neutrino Source Possible neutrino emitter candidate: 18 Ne The same technology used in the production of 6 He is limited in the 18 Ne case to 10 12 ions/s. Despite it is very reasonable to assume that a dedicated R&D will increase this figure, this intensity is used as “today” reference. Issues: MgO less refractory, heat dissipation

10. The Acceleration principle ISOL Target and ECR LinacCyclotronStorage Ring PSSPS 2500 m R=300 m Decay ring/Buncher Bunch rotation is the crucial issue for atmospheric background control! Studies are made on EXISTING CERN machines. Why? Much more detailed knowledge exists, the best way to identify possible problems and limitations.

11. Bunched? 2500 m R=300 m The interactions time structure in the detector is identical to the time structure of the parents in the decay ring in a given position. The beta decay position does not matter, since the parents have the same speed of the neutrinos The far detector duty cycle is bunch length / ring length A B Interactions time Ion intensity time

12. The Decay Ring 100kW decay losses into the decay ring One bunch of 10 ns length From the physics point of view, the bigger the ring is, the better. straight section relative length fixed to 2500 m (~SPS diameter). The ring is essentially flat below ground (10 mrad).

13. A Neutrino Physics Scenario It is reasonable to assume that - in the next years - savings issues will dominate the scenario in EU HEP. A. Imagine a neutrino detector that could do Physics independently of the neutrino factory. B. Imagine to build it, to run it, and to explore non-accelerator physics. C. Imagine that, as soon as the SPL will be ready (~2015?), you make a superbeam shooting muon neutrinos onto it. If this will expand the physics reach, and you’re competitive with the other world programs, you’re ready to do it (known technology). D. Imagine that you have PREPARRED and STUDIED an option to shoot electron neutrinos onto the same detector. If the next neutrino physics will demand it, you’re ready to do it.

14. A Dream? A. the ~600 Kton UNO detector. B. Supernovae, Solar, Atmospheric, Proton Decay:  12,m 12,  23,m 23. C. Frejus site and SPL Super-Beam: possibly  13 D. Frejus site and SPS Beta-Beam: possibly  13, possibly CP (2) and T Is this physics program less wide than a muon-based neutrino factory program? The objectives are wider, the discovery potential is smaller. But, for example, we will see that the information on , if within reach, is even more comprehensive than a muon-based nufactory.

15. SuperBeam Sinergy The proton requirements of the Beta-Beam are part of the ISOLDE@SPL (100uA for 1s every 2-5 s). The ISOLDE@SPL plans 100 uA protons overall. The Superbeam uses 2mA from the SPL. Therefore: The BetaBeam affects the SuperBeam intensity by 3% at most.

16. Why Cherenkov? The detector needs to be very massive, and capable to distinguish electrons from muons Same requirement of the SuperBeam! You don’t need the charge identification......Therefore you don’t need a magnetic detector!

17. The Far Detector Observables The relative neutrino flux for a spinless* parents is ONLY function of  and L, not even of the parent itself. (* as it is for 6 He and 18 Ne)

18. beam-related backgrounds due to Lithium/Fluorine interactions at the end of the straight sections The Far Detector Background GEANT3 simulation, 3E6 proton interactions onto a Fe dump, tracking down to 10 MeV 100 mrad off-axis and 130 km distance. DIF and DAR (K+) contributions <10 -4 background @  =150

19. antineutrinos interactions on Oxygen are typically penalized by a factor ~ 6. Cross Sections T.K Gaisser and J.S. O’Connel, P.R.D34,3 (1986) 822. However: Free protons of H 2 O should also be included

20. The Signal maximization... The signal coming from appearance  interactions after oscillation @ 130 km and 440 kt-year fiducial mass in the hypothesis (  13 =  /2,m 13 =2.4E-3 eV 2 ). The machine duty-cycle is assumed to remain constant. table

21. …and the interaction background... NC interactions potentially produce  ++ decays (almost at rest) and the  + is misidentified as a muon. Asymmetries with Superbeams start to appear (the e/  0 separation becomes  /  ) Kinematical cuts are possible, still delicate and MC dependent. Another strategy consists in having the pions below Cherenkov threshold (see later). Interaction Background

22. ...and the Atmospheric “background” The atmospheric neutrino background has to be reduced mainly by “timing” on the 6He bunches (protons for the SuperBeam). The shortness of the ion bunches is therefore mandatory (10 ns for a ~SPS ring length). However, the directionality of the antineutrinos can be used to further suppress this background by a factor ~4-6X dependent on gamma. Atmospheric Background

23. Anue Summary Numbers

24. The Nue case Neon production Intensity is lower, HOWEVER: 1. 18 Ne has charge 10 and mass 18. 2. For the previous reason, SPS can accelerate the ion up to  =250 (250 GeV/nucleon) WITH THE SAME MAGNETIC FIELD used for 6 He and  =150. =0.93 GeV !!! 3. For the same reasons explained for the antineutrino case, the potential oscillation signal improves despite the fact /L=7E-3 GeV/km

25. Nue Summary Numbers

26. Super-Beta The Super-Beta Beams (SPL-BB) (Old) Super-Beam numu: 9,800 QE/Year @ 260 MeV @ 130 km Beta-Beam anue: 37,250 QE/Year @ 580 MeV @ 130 km (Old) Super-Beam anumu: 2050 QE/Year @ 230 MeV @ 130 km Beta-Beam nue: 18,950 QE/Year @ 930 MeV @ 130 km Obviously: the SuperBeam lower energy is “better”. Still, the oscillation probability of the Beta-Beams are 37% (anue) and 15% (nue) respectively. The SuperBeam has more beam-related background, but is much simpler to do. Beta-beam detector backgrounds to be studied. ONE DETECTOR, ONE DISTANCE, 2X2 BEAMS!

27. A CP or a T search? J. Sato, hep-ph 0006127 In the T search, ambiguities are resolved! The tunability of the beta-beam allows additional choice of the phase cot (  m 2 13 L / 4E) CP Asymmetry T Asymmetry

28. General Considerations A.  13 is just the starting step for super&beta-beams. B. CP violation at low energy is almost exempt from matter effect, therefore already particularly attractive (nue beta-beam, anue beta-beam). C. Who else can do T violation without magnetic field and electron charge identification? (nue beta-beam, numu super-beam). D. CPT test by anue beta-beam, numu super-beam is the ultimate validation of the 3-family mixing model and of the CP and T measurements. E. If LSND is confirmed, 6 mixing angles and 3 CP violation phases are waiting for us! The smallness of the LSND mixing parameter implies high purity beams, the missing unitarity constraints will demand sources with different flavours. H. Minakata, H. Nunokawa hep-ph0009091. CPT Asymmetry

29. One simple Optimization At the same time, it maximizes the overlap with the CP-odd term (at CERN-Frejus distance) Background should not generate a Cherenkov signal!

30. BetaBeam “downgrading”  =75, Flux Drop, Background Drop 11X Flux Drop!!!

31. General Considerations The neutrino factory golden-measurement is the CP violation. Super-Beam+Beta-Beam are competitive in various ways, including T violation!  = 90 deg 99%C.L. Curves (M. Mezzetto, NNN02)

32. Nu2002 comparison chart F. Dydak ~10 -4 ~1 YesYes Let’s Fill the BB column! 0.2-2 GeV

33. Comment on BB cost estimates

34. My Last Words 1. the Beta-Beams are possible! 3. Natural part of a program that starts with a non-accelerator Water Cherenkov phase and a SuperBeam phase. The program covers supernovae detection, proton decay, atmospheric neutrinos, solar neutrinos,  13 search, CP asymmetry, T asymmetry, CPT asymmetry. 4. Scaled technology approach based on existing accelerator technology 2. Unique, unprecedented high intensity high purity e  e beams

35. “Se son rose, fioriranno”. “If they're roses, they will blossom” “Si tiene barbas, San Antón, si no la Purísima Concepción”