1. Beta beam scenarios … for neutrino oscillation physics Beta beam meeting Aachen, Germany October 31-November 1, 2007 Walter Winter Universität Würzburg

2. November 1, 2007Aachen 07 - Walter Winter2 Contents Introduction: Neutrino oscillation physics with beta beams Introduction: Neutrino oscillation physics with beta beams Beta beam scenarios Beta beam scenarios Optimization of a green-field scenario Optimization of a green-field scenario Using different isotopes Using different isotopes Physics case for a beta beam? Physics case for a beta beam? Summary Summary

3. November 1, 2007Aachen 07 - Walter Winter3 Neutrino oscillations with two flavors Mixing and mass squared difference:  “disappearance”:  “appearance”: Amplitude ~Frequency Baseline: Source - Detector Energy

4. November 1, 2007Aachen 07 - Walter Winter4 Picture of three-flavor oscillations Magnitude of  13 is key to “subleading” effects: Mass hierarchy determination CP violation Use e transitions on atmospheric oscillation scale (“Oscillation maximum”) Coupling strength:  13 Atmospheric oscillation: Amplitude:  23 Frequency:  m 31 2 Solar oscillation: Amplitude:  12 Frequency:  m 21 2 Sub- leading effect:  CP

5. November 1, 2007Aachen 07 - Walter Winter5 Matter effects in -oscillations (MSW) Ordinary matter contains electrons, but no ,  Ordinary matter contains electrons, but no ,  Coherent forward scattering in matter has net effect on electron flavor because of CC (rel. phase shift) Coherent forward scattering in matter has net effect on electron flavor because of CC (rel. phase shift) Matter effects proportional to electron density and baseline Matter effects proportional to electron density and baseline Hamiltonian in matter: Hamiltonian in matter: Y: electron fraction ~ 0.5 (electrons per nucleon) (Wolfenstein, 1978; Mikheyev, Smirnov, 1985) Matter potential not CP-/CPT-invariant!

6. November 1, 2007Aachen 07 - Walter Winter6 Appearance channels:  e  Complicated, but all interesting information there:  13,  CP, mass hierarchy (via A) (see e.g. Akhmedov, Johansson, Lindner, Ohlsson, Schwetz, 2004) Anti-nus

7. November 1, 2007Aachen 07 - Walter Winter7 The role of neutrinos+antineutrinos CP asymmetry (vacuum) suggests the use of neutrinos and antineutrinos CP asymmetry (vacuum) suggests the use of neutrinos and antineutrinos One discrete deg. remains in (  13,  )-plane One discrete deg. remains in (  13,  )-plane Best-fit  -beam,  -beam, anti-

8. November 1, 2007Aachen 07 - Walter Winter8 Often used performance indicators Future experiment performance depends on (simulated) values implemented by nature Future experiment performance depends on (simulated) values implemented by nature Often shown: Discovery reaches (  13, MH, CPV) as a function of these simulated values; mainly as a function of  13 and  CP Often shown: Discovery reaches (  13, MH, CPV) as a function of these simulated values; mainly as a function of  13 and  CP Sensitivity to  13 : Largest value of  13, which cannot be distinguished from a simulated  13 =0 Sensitivity to  13 : Largest value of  13, which cannot be distinguished from a simulated  13 =0  Corresponds to new exclusion limit if no signal  Marginalization over  13,  CP, mass hierarchy  Does not depend on simulated  CP

9. November 1, 2007Aachen 07 - Walter Winter9 Correlations and degeneracies Connected (green) or disconnected (yellow) degenerate solutions (at a chosen CL) in parameter space Connected (green) or disconnected (yellow) degenerate solutions (at a chosen CL) in parameter space Discrete degeneracies – even if s+anti- s: (Barger, Marfatia, Whisnant, 2001) Intrinsic ( ,  13 )-degeneracy (Burguet-Castell et al, 2001) sgn-degeneracy (Minakata, Nunokawa, 2001) (  23,  /2-  23 )-degeneracy (Fogli, Lisi, 1996) Discrete degeneracies – even if s+anti- s: (Barger, Marfatia, Whisnant, 2001) Intrinsic ( ,  13 )-degeneracy (Burguet-Castell et al, 2001) sgn-degeneracy (Minakata, Nunokawa, 2001) (  23,  /2-  23 )-degeneracy (Fogli, Lisi, 1996) Affect performance of appearance measurements. For example,  13 sensitivity: Affect performance of appearance measurements. For example,  13 sensitivity: (Huber, Lindner, Winter, 2002; Huber, Lindner, Rolinec, Winter, 2006)

10. November 1, 2007Aachen 07 - Walter Winter10 Example for degeneracy resolution: “Magic baseline” Idea: Yellow term = 0 independent of E, oscillation parameters Idea: Yellow term = 0 independent of E, oscillation parameters Purpose: “Clean” measurement of  13 and mass hierarchy Purpose: “Clean” measurement of  13 and mass hierarchy Drawback: No  CP measurement at magic baseline Drawback: No  CP measurement at magic baseline  combine with shorter baseline (Huber, Winter, 2003)

11. November 1, 2007Aachen 07 - Walter Winter11 Beta beam at very long baseline Operate a beta beam at the magic baseline? (Agarwalla, Choubey, Raychaudhuri, 2006) Operate a beta beam at the magic baseline? (Agarwalla, Choubey, Raychaudhuri, 2006) Use magnetized iron calorimeter as detector CERN-ICAL (INO) ~ magic baseline Use magnetized iron calorimeter as detector CERN-ICAL (INO) ~ magic baseline Authors use 8 B and 8 Li with rel. moderate  ~ 250 - 500 Authors use 8 B and 8 Li with rel. moderate  ~ 250 - 500 L~ 7000 – 9000 km bands

12. Beta beam scenarios

13. November 1, 2007Aachen 07 - Walter Winter13 Motivation: Experiment classes Source Production … and Detection LimitationsL<E> ReactorSystematics 1-2 km ~4 MeV Super- beam Intrinsic beam BG, systematics 100- 2,500 km 0.5 – 5 GeV Neutrino factory Charge identification, NC BG 700- 7,500 km 5-50 GeV  -beam Source luminosity? 100- 2,000 km 0.3 – 10 GeV For leading atm. params Signal prop. sin 2 2  13 Contamination

14. November 1, 2007Aachen 07 - Walter Winter14 Original beta beam concept Key figure (any beta beam): Useful ion decays/year? Key figure (any beta beam): Useful ion decays/year? Often used “standard values”: 3 10 18 6 He decays/year 1 10 18 18 Ne decays/year Often used “standard values”: 3 10 18 6 He decays/year 1 10 18 18 Ne decays/year Typical  ~ 100 – 150 (for CERN SPS) Typical  ~ 100 – 150 (for CERN SPS) (CERN layout; Bouchez, Lindroos, Mezzetto, 2003; Lindroos, 2003; Mezzetto, 2003; Autin et al, 2003) Compared to superbeam: no intrinsic beam background Compared to superbeam: no intrinsic beam background Compared to neutrino factory: no charge identification required Compared to neutrino factory: no charge identification required  In principle, very interesting alternative concept! (Zucchelli, 2002)

15. November 1, 2007Aachen 07 - Walter Winter15 Higher  beta beam

16. 16 Beta beam scenarios: He/Ne “Low” gamma (  <150?) “Low” gamma (  <150?) -Alternative to superbeam? Originally designed for CERN (SPS) -Water Cherenkov detector (see last slide; also: Volpe, 2003) “Medium” gamma (150<  <300-350?) “Medium” gamma (150<  <300-350?) -Alternative to superbeam! Possible at upgraded SPS? -Usually: Water Cherenkov detector (Burguet-Castell et al, 2003+2005; Huber et al, 2005; Donini, Fernandez-Martinez, 2006) “High” gamma (300-350<  <800?) “High” gamma (300-350<  <800?) -Specific physics case for that? Requires large accelerator (Tevatron-size) -Water Cherenkov detector or TASD or MID? (Burguet-Castell et al, 2003; Huber et al, 2005) “Very high” gamma (  >800?) “Very high” gamma (  >800?) -Alternative to neutrino factory? Requires very large accelerator (LHC-size) -Detector technology other than water (TASD? MID?) (Burguet-Castell et al, 2003; Huber et al, 2005; Agarwalla et al, 2005+) Gamma determines neutrino energy and therefore detector technology!

17. November 1, 2007Aachen 07 - Walter Winter17 Example: CERN-Memphys (a superbeam-beta beam hybrid) Beta beam (  =100) plus 4MW superbeam to 440 kt WC detector at Frejus site (L=130 km) Beta beam (  =100) plus 4MW superbeam to 440 kt WC detector at Frejus site (L=130 km) Effect of systematics smaller and absolute performance better than for T2HK Effect of systematics smaller and absolute performance better than for T2HK Antineutrino running not necessary because e to  (beta beam) and  to e (superbeam) channels present (see also: hep-ph/0703279) Antineutrino running not necessary because e to  (beta beam) and  to e (superbeam) channels present (see also: hep-ph/0703279) (Campagne, Maltoni, Mezzetto, Schwetz, 2006) 10 years, 3  Shading: systematics varied from 2% to 5% Example:  13 discovery Sensitive region

18. November 1, 2007Aachen 07 - Walter Winter18 Example:  =350 optimum at CERN? Requires refurbished SPS (supercond. magnets) Requires refurbished SPS (supercond. magnets) Maximum doable at CERN? Maximum doable at CERN? L=730 km L=730 km For CPV an medium  13 even competitive to an optimized high-E NuFact For CPV an medium  13 even competitive to an optimized high-E NuFact (Burguet-Castell, Casper, Couce, Gomez-Cadenas, Hernandez, 2005; Fig. from Huber, Lindner, Rolinec, Winter, 2006)

19. Green-field scenario

20. November 1, 2007Aachen 07 - Walter Winter20 Optimization of a green-field scenario Use two different detector technologies: Use two different detector technologies: –500 kt Water Cherenkov: Large mass, but poor energy resolution at high E (non-QE sample) –50 kt NOvA-like TASD: Smaller mass, but very good energy resolution at high E Assume specific isotopes: 6 He, 18 Ne, with 3 10 18 ( 6 He) and 10 18 ( 18 Ne) decays/year for 8 years (if simultaneous operation) Assume specific isotopes: 6 He, 18 Ne, with 3 10 18 ( 6 He) and 10 18 ( 18 Ne) decays/year for 8 years (if simultaneous operation) Main questions (this talk): Main questions (this talk): –Which is the optimal gamma –What is the optimal baseline? –Which fraction neutrinos/antineutrinos is necessary?

21. November 1, 2007Aachen 07 - Walter Winter21 Scaling with  Fix L/  =1.3 (~ 1st oscillation maximum) Fix L/  =1.3 (~ 1st oscillation maximum) The higher , the better (modulo detector!) The higher , the better (modulo detector!) (Huber, Lindner, Rolinec, Winter, 2005) Our setups 1, 2, 3

22. November 1, 2007Aachen 07 - Walter Winter22 Baseline optimization of a beta beam Baseline optimization depends on performance indicator and gamma setup: (Fig. from Huber, Lindner, Rolinec, Winter, 2005) Baseline optimization depends on performance indicator and gamma setup: (Fig. from Huber, Lindner, Rolinec, Winter, 2005) For lower gamma: Second osc. max. useful to resolve degs For lower gamma: Second osc. max. useful to resolve degs For higher gamma: Degs reolved by improved statistics For higher gamma: Degs reolved by improved statistics

23. November 1, 2007Aachen 07 - Walter Winter23 Balance calculate as fraction of running time; translates easily into balance of useful isotope decays (Fig. from Huber, Lindner, Rolinec, Winter, 2005) Balance calculate as fraction of running time; translates easily into balance of useful isotope decays (Fig. from Huber, Lindner, Rolinec, Winter, 2005) Hardly imbalance as long as ~ 10% of the total running time present (~ 10%/50%=20% of orig. isotope decays) Hardly imbalance as long as ~ 10% of the total running time present (~ 10%/50%=20% of orig. isotope decays) Neutrino-antineutrino balance

24. November 1, 2007Aachen 07 - Walter Winter24 Comparison of setups (Huber, Lindner, Rolinec, Winter, 2005) 3 

25. Using different isotopes

26. November 1, 2007Aachen 07 - Walter Winter26 Isotopes compared: Spectrum Example: Unoscillated spectrum for CERN-INO Example: Unoscillated spectrum for CERN-INO Total flux ~ N   2 (forward boost!) (N  : useful ion decays) Total flux ~ N   2 (forward boost!) (N  : useful ion decays) (from Agarwalla, Choubey, Raychaudhuri, 2006)  Peak E ~  E 0 Max. E ~ 2  E 0 (E 0 >> m e assumed; E 0 : endpoint energy) (E 0 ~ 14 MeV)(E 0 ~ 4 MeV)

27. November 1, 2007Aachen 07 - Walter Winter27 Examples for isotopes Examples for isotopes Want same neutrino energies (=same X-sections, L, physics): Peak energy ~  E 0, flux ~ N   2  Use high  and isotopes with small E 0 or low  and isotopes with large E 0 for same total flux (exact for m e /E 0 << 1) Want same neutrino energies (=same X-sections, L, physics): Peak energy ~  E 0, flux ~ N   2  Use high  and isotopes with small E 0 or low  and isotopes with large E 0 for same total flux (exact for m e /E 0 << 1) Example (table): N  (B/Li) ~ 12 N  (He/Ne),  (He/Ne) ~ 3.5  (B/Li) Example (table): N  (B/Li) ~ 12 N  (He/Ne),  (He/Ne) ~ 3.5  (B/Li) NB:  : Accelerator dof versus N  : ion source dof Where is the cost/feasibility break-even point? NB:  : Accelerator dof versus N  : ion source dof Where is the cost/feasibility break-even point? Different isotopes: Some thoughts ( http://ie.lbl.gov/toi )

28. November 1, 2007Aachen 07 - Walter Winter28 L-  -optimization for MID:  13 sensitivity Same luminosity, same detector! Same luminosity, same detector! Short baseline better for He/Ne, magic baseline for B/Li Short baseline better for He/Ne, magic baseline for B/Li (in prep. with Agarwalla et al)

29. November 1, 2007Aachen 07 - Walter Winter29 A matter of luminosity? Short vs. long baseline Gamma increase: ~ 2.9-4.6 Same physics for ~ 10 x luminosity (Agarwalla, Choubey, Raydchaudhuri, Winter, in prep.)

30. November 1, 2007Aachen 07 - Walter Winter30 Even use alternating ions? Alternating ions possible degeneracy resolution strategy Idea: main statistics at very different neutrino energies! (Donini, Fernandez-Martinez, 2006) Alternating ions possible degeneracy resolution strategy Idea: main statistics at very different neutrino energies! (Donini, Fernandez-Martinez, 2006) (for other degeneracy studies: see, e.g. Donini, Fernandez-Martinez, Rigolin, 2004; Donini, Fernandez-Martinez, Migliozzi, Rigolin, 2004) L=650 km

31. Physics case

32. November 1, 2007Aachen 07 - Walter Winter32 Discussion: Physics case for a beta beam? Can do  13, mass hierarchy, CPV measurements just as superbeam, neutrino factory; physics, in principle, similar Can do  13, mass hierarchy, CPV measurements just as superbeam, neutrino factory; physics, in principle, similar Cannot: Cannot: –Measure leading atm. parameters very well –Be used for muon physics (such as a NF frontend!) –Be used as a muon collider frontend (NF?) –Be used for muon neutrino X-section measurement Key questions: Key questions: –Synergies with other non-oscillation measurements? –Cost/useful ion decays (BB) versus cost/useful muon decays (NF)? How do BB compare to superbeams? –Different isotopes versus different  ? –Potential for non-standard physics? –Is there a seperate physics case for a beta beam?

33. November 1, 2007Aachen 07 - Walter Winter33 Separate physics case for a beta beam? Blue: Superbeam upgrade based upon: lower effort Blue: Superbeam upgrade based upon: lower effort Green: Beta beam based upon: Good CPV reach, MH in most cases Green: Beta beam based upon: Good CPV reach, MH in most cases Red: Neutrino factory (optimized) based upon: Good  13 reach Red: Neutrino factory (optimized) based upon: Good  13 reach (3  m 31 2 =0.0022 eV 2  Longer L

34. November 1, 2007Aachen 07 - Walter Winter34 Summary Beta beam performance depends on isotope and , which determine the physics reaches Beta beam performance depends on isotope and , which determine the physics reaches The physics potential can be made similar to that of a NF or SB; therefore, for standard oscillation physics, it all comes down to a cost comparison However: there might be a separate physics case for intermediate sin 2 2  13 The physics potential can be made similar to that of a NF or SB; therefore, for standard oscillation physics, it all comes down to a cost comparison However: there might be a separate physics case for intermediate sin 2 2  13 Isotope comparison master formulae:   E 0 (1) =   E 0 (2), N  (1) =N  (2) (E 0 (1) /E 0 (2) ) 2 Accelerator effort versus ion source effort Isotope comparison master formulae:   E 0 (1) =   E 0 (2), N  (1) =N  (2) (E 0 (1) /E 0 (2) ) 2 Accelerator effort versus ion source effort

35. November 1, 2007Aachen 07 - Walter Winter35 Beta beam vs. Superbeam vs. NuFact? Lower  : Can easily compete with superbeam upgrades if properly optimized Lower  : Can easily compete with superbeam upgrades if properly optimized Higher  : At least theoretically competitive to a neutrino factory Higher  : At least theoretically competitive to a neutrino factory Challenges: Challenges: -Can fluxes be reached? -Compare completely optimized accelerator strategies? (Fig. from Huber, Lindner, Rolinec, Winter, 2005)