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Unlocking Neutrino Mysteries: SPS Upgrade Potential for Beta/EC Beams

Explore the physics potential and experiments from 1998-2006 in neutrino oscillations, CP violation, and absolute neutrino masses, including Beta Beams and Double CHOOZ. Discover the implications of energy dependence in suppressed neutrino oscillations and the unique aspects of monochromatic neutrino beams.

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Unlocking Neutrino Mysteries: SPS Upgrade Potential for Beta/EC Beams

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  1. Physics potential of SPS upgrade in regard to Beta/EC Beams J. Bernabeu Univ. Valencia and IFIC LHC LUMI 2006 CARE-HHH-AP Workshop IFIC, October 2006

  2. Physics potential of SPS upgrade in regard to Beta/EC Beams • Experiments 1998  2006 in Neutrino Oscillations • What is known, what is unknown • Second generation approved experiments for U(e3) and third generation proposals for the CP phase δ • ß Beams: combination 6He ()- 18Ne() at the same γ • EC Beams: combination of two energies for the same ion 150Dy • Comparison between ( low energy Ep(SPS) ≤ 450 GeV, Frejus) and (high energy Ep(SPS) ≤ 1000 GeV, Canfranc )

  3. Experiments 1998 - 2006

  4. First very recent results from MINOS • From Fermilab to Sudan,  disappearance: L/E dependence Energy resolution in the detector allows a better sensitivity in Δm223 : compatible with previous results with some tendency to higher values

  5. Neutrino flavour oscillations What is known, what is unknown ? Absolute neutrino masses ? 3 H beta, Cosmology • Form of the mass spectrum • Matter effect in neutrino propagation Majorana neutrinos ?  0: masses and phases

  6. The Pontecorvo MNS Matrix After diagonalization of the neutrino mass matrix,  For Flavour oscillations U: 3 mixings, 1 phase Even if they are Majorana • Atmospheric KEK More LBL-beams Appearance e! Reactor Matter in Atmospheric… • Solar KAMLAND

  7. Second generation approved experiments for U(e3) • Appearance experiments for the suppressed transition νμνe : T2K, NOVA Off-axis neutrino beam from Fermilab to Soudan From J-PARC to SK

  8. Second generation approved experiments for U(e3) • Disappearance experiment from reactor νe: CHOOZ  Double CHOOZ at short and intermediate baselines with near and far detectors. The most stringent constraint on the third mixing angle comes from the CHOOZ reactor neutrino experiment with sin2(2θ13)<0.2. Double Chooz will explore the range of sin2(2θ13) from 0.2 to 0.03-0.02, within three years of data taking.

  9. Beta Beam Concept P. Zuchelli Design and performance: M. Benedikt, M. Lindroos, M. Mezzetto…

  10. Neutrino Oscillation Physics • After atmospheric and solar discoveries and accelerator and reactor measurements → θ13 , δ • CP violation accessible in suppressed appearance experiments Appearance probability: • For Beta Beams, • 6He antineutrino beam • combined with • 18Ne neutrino beam • 5 years each • Intensity of 2.9x1018 6He and • 1.1x1018 18Ne decays per year • Detection by charged-current event with a muon in the final state  440 Kton fiducial mass water Cherenkov detector

  11. Beta Beams • Neutrino Continuous Spectrum implies the need of the reconstruction • of the energy in the detector for each event, based on the quasi elastic • channel 6 He 18 Ne

  12. Fixing the CERN-Frejus baseline • Is the sensitivity to CP Violation and θ13 changing with energy? • For γ > 80, the sensitivity changes rather slowly because the flux at low energies does not reduce significantly. • Then it is not advantageous to increase the energy if the baseline is not correspondingly scaled to remain closed to the atmospheric oscillation maximum: remember L/E ! J. Burguet-Castell et al.

  13. Fixing γ • The maximum energy reachable with the present SPS is γ=150. • Is the sensitivity to θ13 and δ changing with the baseline? • L = 300 Km is clearly favoured, but …

  14. Comparison of two set-ups • Setups with the same γ for both ions • Set up I : γ=120, L=130 Km (Frejus) • Set up II : γ=330, L=650 Km (Canfranc) Set up II needs the upgrade of SPS until Ep=1000 GeV J. Burguet-Castell et al. Conclusion: Set up II is clearly better. It provides better precision and resolves the degeneracies.

  15. Comparison of two set-ups CP violation exclusion plot at 99% CL Exclusion plot for θ13 at 99 % CL Outlook: R & D effort to design Beta-beams for the upgraded CERN-SPS (Ep=1000 GeV) appears justified.

  16. Interest of energy dependence in suppressed neutrino oscillations • Appearance probability: • |Ue3| gives the strength of P(ne→νμ) • δ gives the interference pattern: CP odd term is odd in E/L • This result is a consequence of • a theorem under the assumptions of CPT invariance and absence of absorptive parts. This suggests the idea of a monochromatic neutrino beam to separate δ and |Ue3| by energy dependence! δ acts as a phase shift

  17. Interest of energy dependence in suppressed neutrino oscillations Canfranc Frejus

  18. Z protons N neutrons Z-1 protons N+1 neutrons Neutrinos from electron capture How can we obtain a monochromatic neutrino beam? J. Bernabeu et al Electron capture: boost Forward direction 2 body decay! a single discrete energy if a single final nuclear level is populated From the single energy e--capture neutrino spectrum, we can get a pure and monochromatic beam by accelerating ec-unstable ions  No need to reconstruct the neutrino energy in the detector !

  19. An idea whose time has arrived ! • In heavy nuclei (rate proportional to square wave function at the origin) and proton rich nuclei (to restore the same orbital angular momentum for protons and neutrons ) •  Superallowed Gamow-Teller transition The “breakthrough” came thanks to the recent discovery of isotopes with half-lives of a few minutes or less, which decay in neutrino channels near 100% through electron capture to a single Gamow-Teller resonance.

  20. Implementation • The facility would require a different approach to acceleration and storage of the ion beam compared to the standard beta-beam, as the atomic electrons of the ions cannot be fully stripped. • Partly charged ions have a short vacuum life-time. The isotope we discuss ( 150Dy) has a half-life ≤ vacuum half-life ~ few minutes. • For the rest, setup similar to that of a beta-beam. Like for Ne, there could be problems with charge space if we want to accumulate 1018 decaying ions per year  Look for an isotope with all the nice properties pointed out before and a half- life near 1 second ! Electron neutrino flux • Notice the proportionality with γ2 and the monochromaticity • Strategy: • Put all the intensity at the energy in which the sensitivity to • Physics is higher !

  21. Experimental set-up for EC • Combine two different energies for the same ion and baseline • 1018 decaying ions/year Appearance & Disappearance • 440 kton water ckov detector • Set up I (low energy, Frejus): 5 years g =90 (close to minimum energy to avoid background) 5 years g = 195 (maximum achievable at present SPS) Versus 10 years for each γ the virtues of two energies L = 130 km (CERN-Frejus) • Set up II (high energy, Canfranc): 5 years g = 195 (maximum achievable at present SPS) 5 years g = 440(maximum achievable at upgraded SPS) L = 650 km (CERN - Canfranc)

  22. Set up I - Disentangling θ13 and δ Much better separation for two different energies, even with lower statistics Access to measure the CP phase as a phase- shift

  23. The virtues of two energies 130 km

  24. Set up I: Fit of 13 ,  from statistical distribution The principle of an energy dependent measurement is working and a window is open to the discovery of CP violation

  25. Exclusion plot: sensitivity Total running time: 10 years... Impressive!! Significant even at 1o

  26. Exclusion plot: δ≠0sensitivity Total running time: 10 years... Significant for θ13 > 40

  27. Set up II: The virtues of combining two energies 650 km Conclusion: the separation between 13 and  is much better than that for set up I

  28. Set up II: θ13sensitivity 0.1 – 0.4 degrees, depending onδ δ 99 % C L θ13

  29. Set up II: δ sensitivity Significant for θ13 ≥ 0.2 degrees. Asymptotically, a δ sensitivity of ± 3 degrees δ 99 % C L IMPRESSIVE !!! θ13

  30. Set up II: Fit of 13 ,  from statistical distribution δ θ13 Conclusion: the precision reachable for the CP phase is better than that for set up I <-> WITH NEUTRINOS ONLY, AT TWO SELECTED DIFFERENT ENERGIES

  31. Conclusions • The simulations of the Physics Output for both Beta and EC beams indicate: THE UPGRADE TO HIGHER ENERGY (Ep = 1000 GeV) IS CRUCIAL TO HAVE A BETTER SENSITIVITY TO CP VIOLATION (the main objective of the third generation neutrino oscillation experiments) IFF ACCOMPANIED BY A LONGER BASELINE. • THE BEST E/L FOR HIGHER SENSITIVITY TO THE MIXING U(e3) IS NOT THE SAME THAN THAT FOR THE CP PHASE. Like the phase-shifts, the presence of δis easier to observe in the region of the second oscillation. The mixing is better seen around the first oscillation maximum, instead. • Besides the feasibility studies for the machine, MOST IMPORTANT FOR PHYSICS IS THE STUDY OF THE OPTIMAL CONFIGURATION BY COMBINING - Low energy ( < 2017(?)) with high energy (> 2017(?)) - Frejus (L=130 Km) with Canfranc (L=650 Km) , i.e., the decay “ring” should be a triangle and not a rectangle. - EC monochromatic neutrinos with 6He beta- antineutrinos. • MUST DEFINE A PROGRAM TO DETERMINE INDEPENDENTLY THE RELEVANT CROSS SECTION

  32. Outlook • The result of the synergy of Neutrino Physics with Nuclear Physics (EURISOL) and LHC- Physics (SPS upgrade) for the Facility at CERN could be completed with the synergy with Astroparticle Physics for the Detector, common to neutrino oscillation studies with terrestrial beams, atmospheric neutrinos (neutrino mass hierarchy), supernova neutrinos and Proton decay!!! • IF DONE, CERN AND EUROPE WILL RETAKE THE LEAD IN NEUTRINO PHYSICS AROUND 2020 WITH THE DISCOVERY OF CP VIOLATION IN THE LEPTON SECTOR.

  33. Access to a precise value of  650 Km 1. Enter into the second oscillation in E/L, where the sensitivity to  is higher  At fixed E, move to Canfranc: L=650 Km … in study at present 2. Check that the phase shift measured is the CP phase  combine EC  with - (6He) … preliminary

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