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CP-even neutrino beam

CP-even neutrino beam. N. Sasao Kyoto University The talk is based on hep-ex/0612047 done in collaboration with A. F ukumi, I. Nakano, H. Nanjo, S. Sato, M. Yoshimura. Introduction. If finite value of q 13 is NOT found in the next round neutrino experiments, we need

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CP-even neutrino beam

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  1. CP-even neutrino beam N. Sasao Kyoto University The talk is based on hep-ex/0612047 done in collaboration with A. Fukumi, I. Nakano, H. Nanjo, S. Sato, M. Yoshimura Sasao @ Neutrino Telescope

  2. Introduction • If finite value of q13 is NOT found in the next round neutrino experiments, we need • More powerful superbeam • Neutrino factory • Muon-based neutrino factory • Beta-beam • We like to add one more option to neutrino factory, which would benefit CP phase measurement. Sasao @ Neutrino Telescope

  3. Concept of CP-even neutrino beam Point 1 • Ideal neutrino beam for CP phase (d) measurement: • Pure beams of neutrino and anti-neutrino. • Mono-energetic. • Flux is known and is composed of neutrino and anti-neutrino inversely proportional to their cross sections. • CP phase may be determined just counting the number of m +/- • We propose to use bound-state beta-decay (bb) to generate mono-energetic anti-neutrino in addition to electron capture (EC) neutrino. • This idea is an extension of beta-beam and EC beam. Point 2 Point 3 Sasao @ Neutrino Telescope

  4. Oscillation Probability Point 1 • Appearance experiment is needed to observe CP. • Matter effect is negligible at low energy. • For anti-neutrino, the 3rd term reverses its sign. • P (ne)+P (ne) is sensitive to q13while P (ne)-P (ne) to CP phase d. Sasao @ Neutrino Telescope

  5. Oscillation probability and CP asymmetry At the 1st oscillation peak, E/L=600 MeV/310 km. Sin22θ13=0.1, 0.05, 0.01 Sasao @ Neutrino Telescope

  6. Bound-state β-decay Point 2 If the parent atoms are (fully or partially) ionized, electrons emitted from ordinary beta decay may be captured in available atomic orbits. In this case, anti-neutrino becomes mono-energetic. Bound-state beta-decay has been studied theoretically for long time, but experimentally it was proven rather recently. Theoretical studies by R.Daude et al : Comptes. Rend. 224,1427 (1947) R.M.Shrk: Phy.Rev.84, 591(1949) J.H.Bahcall: Phy.Rev.124, 495(1961) Sasao @ Neutrino Telescope

  7. Ratio of bound-to-continuum beta decay Bound beta ratio The ratio is bigger for large Z and small Q. Unfortunately requirement of short life time means large Q and contradicts with the large bound-to-continuum ratio. Q value Sasao @ Neutrino Telescope

  8. Experimental studies PRL95,052501(2005) • The first experiment to demonstrate the bound-state beta decay was done in 1992 at GSI. • For example, fully ionized 187Re (the galactic chronometer) life time is shorter more than 109 times than the neutral Re. • The experiment shown here is to measure the bound-to-continuum ratio of 207Th. • 208Pb from the heavy ion synchrotron (SIS) hit a production target; 208Tl was selected by the fragments separator (FRS), and stored in the experimental storage ring (ESR); the daughter nuclei was identified by the Fourier analysis of the frequency change. Sasao @ Neutrino Telescope

  9. Bound Decay Branching The result agrees very well with the theoretical expectation. Sasao @ Neutrino Telescope

  10. Beta beam & EC beam Point 3 • The basic idea of beta beam is to accelerate and store beta unstable nuclides. Then sharply focused high energy neutrinos are obtained in the forward direction. • Merits of beta beam • Pure neutrino beam • Known energy spectrum • Known intensity • Merits of EC beam • Mono energetic Zucchelli:PLB532,166(2002) J. Sato: PRL95,131804(2005) J. Bernabeu et al: hep-ph/0605132; J. Bernabeu et al:JHEP0512,14(2005) Sasao @ Neutrino Telescope

  11. CERN scheme for beta & EC beam 10^14 ions /decay ring Volpe hep-ph/0605033 Sasao @ Neutrino Telescope

  12. Sensitivity to q13 J.E.Campagne et al Hep-ph/0603172 Sasao @ Neutrino Telescope

  13. Sensitivity to d • The red dashed curve is when beta intensity is ½ of the design. • Thus the intensity is the key parameter. Sasao @ Neutrino Telescope

  14. CP-even beam and its variants • (Pure) CP-even beam • Consists of single isotope which has both EC and bound-state beta decay channels. • Need a detector capable of m+/m- discrimination. • Examples: 108Ag, 110Ag, 114In, 104Rh • Mixed CP-even beam • Two separate isotopes, with EC or bound-state beta decay. • Need to store both beams simultaneously in a ring or store them in a time-sharing mode. • Examples:122Cd (bb) & 152Yb (EC) Sasao @ Neutrino Telescope

  15. １0847Ag 2.85% ｔ1/2=2.37 min 97.15% 1016keV, 1.76% 1484keV,0.26% 1918keV,2.35% 1649keV, 95.5% 10846Pd 10848Cd Property of 108Ag Neutral 108Ag has both EC and b-decay modes. Hydrogen-like 108Ag46+ has bound-state b-decay in addition. EC b-decay Sasao @ Neutrino Telescope

  16. Hydrogen-like 108Ag life 2.37min- 2.36min Sasao @ Neutrino Telescope

  17. ~0.3 Sasao @ Neutrino Telescope

  18. Rate Estimate • Boosting 108Ag46+ with g=180 produces (anti)-neutrino beam of En=600-700 MeV. • This choice of energy is made considering the cross section and multi-pion production rates.. • Reference rate • 1014 ions /ring (same as the beta-beam) • 100k ton target at L=310 km. • 4 mono-chromatic lines are included. • 2 QE events/year: too small ! Sasao @ Neutrino Telescope

  19. Mixed CP-even beam • For EC beam, better isotope is 152Yb. • Life time: 3 sec. • En =4988 keV • g=60 • EC/(EC+b+)=0.3 • Rate=1400 (QE) events/year • This rate is worth further study. Sasao @ Neutrino Telescope

  20. Mixed CP-even beam (2) • For bb beam, better isotope is 122Cd. • Life time: 5.24 sec. • En =3031 keV • bb/(bb+cb)=0.01 • Rate=12 events/year Sasao @ Neutrino Telescope

  21. Some comments • EC nuclide candidates: • 152Yb; Life time=3 sec; En =4988 keV; EC/(EC+b+)=0.3 • Isotope intensity in the ring • 1014 ions is assumed. • Limit comes from space charge and production rate. • Space charge limit is severer for highly charged ions. • Duty factor limit may be relaxed because of better background rejection. Bernabea et al. hep-ph/0510278 Sasao @ Neutrino Telescope

  22. Summary • CP-even neutrino beam • Pure mono-energetic ne and ne beam; suited to determine CP phase. • Bound-sate beta-decay is employed to produce ne in addition to EC for ne. • 108Ag for pure CP-even beam • 122Cd and 158Yb for mixed beam. • Feasibility very much depends on production rate of these isotopes as well as accelerator technology to store high current beams. • Hope RI factory may find better isotopes. • The option of CP-even beam should be kept in mind for further study. Sasao @ Neutrino Telescope

  23. Back Slides Sasao @ Neutrino Telescope

  24. Other isotope candidates for pure CP-even beam Sasao @ Neutrino Telescope

  25. Bound-state beta-decay、example 2 • Cosmological clock • 187Re neutral • T=42 Gyear • 187Re75+ • T=33 year PRL77,5190,1996 Sasao @ Neutrino Telescope

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