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Do Neutrinos Violate CP Symmetry? Insights from Hisakazu Minakata at NOVE06

In this presentation, Hisakazu Minakata from Tokyo Metropolitan University delves into the intriguing question of whether neutrinos violate CP symmetry. He argues that the answer is likely yes due to the properties of the MNS matrix, which suggests non-cancellation among the phases. Minakata discusses the significance of CP violation in neutrino physics and its implications for understanding baryon asymmetry in the universe. He highlights the importance of interdisciplinary approaches in measuring CP violation, exploring both low-energy and high-energy detection methods.

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Do Neutrinos Violate CP Symmetry? Insights from Hisakazu Minakata at NOVE06

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  1. Do Neutrinos Violate CP? Hisakazu Minakata Tokyo Metropolitan University

  2. Do neutrinos violate CP? Tough question! • I believe the answer YES, • Because MNS matrix is S+(l)S(); it is hard to believe that they all cancel out => next sheet • Possibility of cancellation? • accidentally small 13 vs. accidentally small  • small 13 may arise if there is a symmetry, but no symmetry is known for tuned small  Nishikawa-san may be right … NOVE06@Venice

  3. Do neutrinos violate CP? (continued) • Therefore, absence of KM type CPV highly unlikely • What is nontrivial, however, is to understand the meaning of  when it is measured • requires interdisciplinary knowledge, e.g., large mixing in susy sectors, LFV, leptogenesis, KM phase, etc NOVE06@Venice

  4. How about Majorana CPV? • There is a strong argument due to Yanagida-san, which answers the question in the positive • We know that our universe is asymmetric to baryon number • We know that above 1 TeV only meaningful quantum number is B-L, not B or L separately, because of anomaly (“sphaleron”) • Therefore, we must have B+L generation to have nonzero baryon number NOVE06@Venice

  5. How about Majorana CPV? (continued) • Let us assume SM of particle physics => no operator which violates B+L • The lowest dimension operator which violate B-L is which must exists • This is nothing but the neutrino mass operator observed by SK, SNO, KamLAND, and K2K, and others (confirmed to exists!) • Therefore,  Majorana mass must exist (otherwise, we do not have baryon # excess) NOVE06@Venice

  6. Rest of my talk • Comments on how to measure CPV • Issue of two (can be naturally) small quantities, 13,deviation from max 23 : • 13 revisited • 23 revisited NOVE06@Venice

  7. How can CPV be probed? NOVE06@Venice

  8. How can CPV be probed? • Low-energy superbeamvs. high-energy  factory • Low-energy because CPV is large • High-energy because muon detection is clean • Now, both approaches start to converge! JJ.Gomez-Cadenas (private), Brondel (Nufact-ISS2@KEK) NOVE06@Venice

  9. How CP phase  affects oscillation probability? At low energy  changes probability in a dynamic way and in a different way from matter Seen clearly by bi-probability plot Art work by Adam Para => Two solutions of S232 x NOVE06@Venice

  10. For experts Spectral information powerful • Intrinsic degeneracy nearly resolved by T2K II setting even at small 13 • Yet, sign-m2 (mass hierarchy) degeneracy is robust Ishitsuka et al. NOVE06@Venice

  11. 2 detector method for CPV HM-H.Nunokawa, 97 • Since  oscillation is a phase-modulated phenomenon, the distance-dependent information is important • Particularly powerful for 2nd baseline at ~ 2nd oscillation maximum => Kajita-san’s talk for more about it NOVE06@Venice

  12. NOVE03; birthplace of Kamioka-Korea strategy (my story) NOVE06@Venice

  13. How big is 13?; the crucial question NOVE06@Venice

  14. Vanishing 13; ‘t Hooft approved If  symmetry is the case … near maximal 23 small 23 Grimus, Ma, Valle … (infinite references) NOVE06@Venice

  15. There are 2 ways to answer the question LBL vs. reactor NOVE06@Venice

  16. New possibility! => Messbauer enhanced e-bar B decay+resonant absorption Raghavan, hep-ph/0511191, hep-ph/0601079 • e-bar+3He+bound-e -> 3H; resonant nature • Monochromatic (18.6keV) e-bar beam from inverse reaction; 3H bound state  decay • Recoilless setting by embedding 3H and 3He into solid => Messbauer effect 10 m baseline 13 experiment ! NOVE06@Venice

  17. Rate estimate =1132 s Doppler shift • res = 4.2 x 10-41 [4 (a Z)3] (E e-bar /MeV)/ft 1.2 x 10-5 106/(FDHM) =107 = 10-42 cm2 (capture cross section) • R = f NTres = 0.03/day (100 MCi, 1kg 3He) • T2 ~ 2 ms =>  = 3 x 10-13 relativeenhancement by a factor of ~ 1012 (x0.07) • res = 10-31 cm2 (11 order enhancement) • R = 3 x 106 /day (1 MCi, 100g 3He, L=10m) Messbauer enhancement million events a day! E/E ~ 10-17 => neutrino’s gravitational red shift NOVE06@Venice

  18. Which kind of 13 experiment? • Spectrum analysis requires multiple detector or movable detector possible because L=10 m • Reduction of systematic error => 0.1-0.3% if direct counting of 3H atom possible • Monochromatic beam + gigantic statistices => high sensitivity not only to 13 but also tom2 NOVE06@Venice

  19. Sensitivities to m2 and sin2213 sin2213 = 0.1 sin2213 = 0.01 • Run IIB = 10 point measurement at LOM/5, 3LOM/5, … 19LOM/5, • each 106 events, usys = 0.2%, c = 10% NOVE06@Venice

  20. Sensitivities to m2 and sin2213 1DOF, optimistic error: usys=0.2% HM & S. Uchinami, hep-ph/0602046 NOVE06@Venice

  21. Sensitivities to m2 and sin2213 1DOF, pessimistic error: usys=1% NOVE06@Venice

  22.  mass hierarchy by m2(ee) - m2() Nunokawa et al. 05 NOVE06@Venice

  23. Are there ways to solve 23 degeneracy? NOVE06@Venice

  24. Reactor + accelerator method • A-disappearance => s223=0.4 or 0.6 • A-appearance => s223sin2213 = 0.06 • R => sin2213 = 0.1 • Solves 23 degeneracy MSYIS, hep-ph/0211111 NOVE06@Venice

  25. Region of resolved 23 degeneracy T2K II (4MW+HK) + phase II type reactor; Hiraide et al. (7 Samurai), hep-ph/0601258 MSYIS => NOVE06@Venice

  26. Atm ; best way for 23 degeneracy? T.Kajita@NNN05 NOVE06@Venice

  27. n3 n2 n1 sin2q13 sin2q23 Kajita@Korean detector WS 0.092 Mtonyr Super-K data cosqzenith Analysis with and w/o solar terms Search for non-zero q13 En(GeV) with 12 terns (best fit s2q23 = 0.51) w/o 12 NOVE06@Venice

  28. Conclusion • Leptonic CPV, both KM and Majorana types, very likely to exist • There are still rooms in making progress with ‘‘known conventional beam’’ for exploring CPV • New opportunities exist in Messbauer enhanced recoilless resonant absorption • 23 degeneracy; hardest problem for accelerator (reactor or atmospheric?) NOVE06@Venice

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