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J. Bernabeu U. Valencia and IFIC B. Pontecorvo School September 2007 Energy Dependence and Physics Reach in regard to Beta/EC Beams
Energy Dependence and Physics potential in regard to Beta/EC Beams • 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 )
The Pontecorvo MNS Matrix Even if they are Majorana • Atmospheric KEK More LBL-beams • Solar KAMLAND After diagonalization of the neutrino mass matrix, For Flavour oscillations U: 3 mixings, 1 phase Appearance e! Reactor Matter in Atmospheric…
Beta Beam Concept P. Zuchelli Design and performance: M. Benedikt, M. Lindroos, M. Mezzetto…
Neutrino Oscillation Physics 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 • After atmospheric and solar discoveries and accelerator and reactor measurements → θ13 , δ
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 18 Ne 6 He
Fixing the CERN-Frejus baseline J. Burguet-Castell et al. • 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 !
Fixing γ • Is the sensitivity to θ13 and δ changing with the baseline? • L = 300 Km is clearly favoured, but … • The maximum energy reachable with the present SPS is γ=150.
Comparison of two set-ups Conclusion: Set up II is clearly better. It provides better precision and resolves the degeneracies. J. Burguet - Castell et al. • 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
Comparison of two set-ups Outlook: R & D effort to design Beta-beams for the upgraded CERN-SPS (Ep=1000 GeV) appears justified. CP violation exclusion plot at 99% CL. Exclusion plot for θ13 at 99 % CL.
Interest of energy dependence in suppressed neutrino oscillations • Appearance probability: This suggests the idea of a monochromatic neutrino beam to separate δ and |Ue3| by energy dependence! • |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 δ acts as a phase shift
Interest of energy dependence in suppressed neutrino oscillations Canfranc Frejus
Neutrinos from electron capture How can we obtain a monochromatic neutrino beam? J. Bernabeu et al boost Z protons N neutrons Z-1 protons N+1 neutrons Electron capture: 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 !
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.
Implementation • Partly charged ions have a short vacuum life-time. The isotope we discuss ( 150Dy) has a half-life ≤ vacuum half-life ~ few minutes. • 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. • For the rest, setup similar to that of a beta-beam. Due to possible problems with space charge 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 sec. 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 !
Experimental set-up for EC • Combine two different energies for the same ion and baseline Appearance & Disappearance • 440 kton water ckov detector • Set up I (low energy, Frejus): • Set up II (high energy, Canfranc): L = 650 km (CERN - Canfranc) • 1018 decaying ions/year 5 years 90 (close to minimum energy to avoid background) 5 years = 195 (maximum achievable at present SPS) Versus 10 years for each γ the virtues of two energies L = 130 km (CERN-Frejus) 5 years 95 (maximum achievable at present SPS) 5 years = 440(maximum achievable at upgraded SPS)
Much better separation for two different energies, even with lower statistics Access to measure the CP phase as a phase- shift Set up I - Disentangling θ13 and δ
The virtues of two energies 130 km
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
Set up I:Exclusion plot: sensitivity Total running time: 10 years... Significant below 1o
Set up I: Exclusion plot: CP sensitivity Total running time: 10 years... Significant for θ13 > 40
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
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
Set up II: θ13sensitivity 0.1 – 0.4 degrees, depending on δ
Set up II: Exclusion plot: CP sensitivity Without any previous information on θ13 …
Set up II: δ sensitivity δ sensitivity < 45º for θ13 ≥ 3º. Asymptotically, a δ sensitivity of ± 18º δ 99 % C L θ13
Set up II: Exclusion plot: CP sensitivity IMPRESSIVE !!! If θ13 previously known …
Set up II: δ sensitivity δ sensitivity < 45º for θ13 ≥ 0.4º. Asymptotically, a δ sensitivity of ± 8º 50 δ -50 99 % C L 1 3 θ13
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 δ is easier to observe in the region of the second oscillation: Set up II in EC beams has an impressive sensitivity to CPV, particularly if the mixing is previously known. 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
Outlook • The result of the synergy of Neutrino Oscillation Physics with LHC- Physics (SPS upgrade) and, in the case of Beta/EC Beams, with Nuclear Physics (EURISOL) for the Facility at CERN, could be completed with the synergy with Astroparticle Physics for a Multipurpose Detector, common to neutrino oscillation studies with terrestrial beams, Atmospheric Neutrinos (neutrino mass hierarchy), supernova neutrinos and Proton decay!!! MUCHAS GRACIAS!