CP-even neutrino beamCP甚至中微子束

1、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.,2007/3/8,1,Sasao Neutrino Tele

2、scope,Concept of CP-even neutrino beam,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

3、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 1,Point 3,2007/3/8,2,Sasao Neutrino Telescope,Oscillation Probability,Appearance exp

4、eriment 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 q13 while P (ne)-P (ne) to CP phase d.,Point 1,2007/3/8,3,Sasao Neutrino Telescope,Oscillation probability and CP asymmetry,Sin2213=0.1, 0.05,

5、0.01,At the 1st oscillation peak, E/L=600 MeV/310 km.,2007/3/8,4,Sasao Neutrino Telescope,Bound-state -decay,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

6、. Bound-state beta-decay has been studied theoretically for long time, but experimentally it was proven rather recently.,Point 2,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),2007/3/8,5,Sasao Neutrino Telesco

7、pe,Q value,Bound beta ratio,The ratio is bigger for large Z and small Q.,Ratio of bound-to-continuum beta decay,Unfortunately requirement of short life time means large Q and contradicts with the large bound-to-continuum ratio.,2007/3/8,6,Sasao Neutrino Telescope,Experimental studies,The first exper

8、iment 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 s

9、ynchrotron (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.,PRL95,052501(2005),2007/3/8,7,Sasao Neutrino Telescope,Bound Decay Bra

10、nching,The result agrees very well with the theoretical expectation.,2007/3/8,8,Sasao Neutrino Telescope,Beta beam J. Bernabeu et al: JHEP0512,14(2005),Zucchelli:PLB532,166(2002),Point 3,2007/3/8,9,Sasao Neutrino Telescope,CERN scheme for beta Life time=3 sec; En =4988 keV; EC/(EC+b+)=0.3 Isotope in

11、tensity 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/0510278,2007/3/8,20,Sasao Neutrino Telescope,Summary,CP-

12、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.,2007/3/8,21,Sasao Neutrino Telescope,2007/3/8,Sasao Neutrino Telescope,22,Back Slides,Other isotope candidates for p