Neutrino Oscillation and CP violation

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1 Neutrino Oscillation and CP violation Contents. Neutrino Oscillation Experiments and CPV. Possible CP measurements in TK 3. Summary Nov.4, K. Nishikawa Kyoto niversity

2 CP Violation Asymmetry between a particle and an anti-particle. Baryons in the niverse Many possible sources. So far only CKM source in quark. In quark sector, a LARGE CP violation has been established. It is well explained in the CKM model. δ ~ 6 ε K V ub -. η e iδ sinβ.6.8. ρ ρ iη M Bs M Bs -.6 M Bd

3 In lepton sector CP violation in leptonic - very small final state interactions Only possible in oscillation (and ββ) CPV(K ) a + a Two amplitudes & ( δ e iδ e iδ ) a * e iδ Diff. Im(a )sin( δ The solar, atmosphric observations are good at discovering a surprise (if it is a large effect) for which small scale (controlled) experiments do not have enough sensitivity. - Long baseline ( 8 km) They are however not good at measuring underlying parameters very precisely. Just entered an era of second generation high precision accelerator experiments Still rooms for surprises history of neutrino studies both in theory and in experiments 3 Generation scheme may have to be changed + a * e iδ δ a * δ 3 )

4 4 Maki-Nakagawa-Sakata Matrix and Oscillation probability = τ µ 3 CP M MNS e V = δ δ c s s c c e s e s c c s s c 3 i 3 i PMNS = α α e e V i i CP M Dirac CP Phase e iδ ) 3 )R 3 ( 3 )R ( R ( MNS θ θ θ = E L m sin Im 4E L m sin 4Re ) P( ij * i i j * j i j ij * i i j * j i j = α β α β > α β α β > β α 4E L m sin 4 ) P( ij j i i j = α α > α α

5 5 µ e with m ~ ev and CP violation = τ τ τ µ µ µ τ µ ) (m ) (m ) (m e3 e e e µ e * * * Interference CP violation supressed by small m small e3

6 Contour of allowed region for µ (τ) atmospheric linear scale.4-3 m [ev ] 68%.87-3 m [ev ] 9% 6

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8 Oscillations in 3 generation scheme with L/E ~ 3 km/ GeV atmospheric P P P P m m ij << m = m j 3 i m m ( ) 4 ( ) = cos θ sin θ sin.7 m L / E µ CHOOZ ( ) ( ) = sin θ sin.7 m L / E Next ( ) ( ) = sin θ sin θ sin.7 m L / E HE e µ τ θ project beam ( ) ( ) = cos θ sin θ sin.7 m L / E e e e e τ 3 θ? 3? ~? π / m 3 m 8 m m 3

9 Critical path for future oscillation experiment Confirmations Atmospheric ΚΚ Solar (Kamland) µ τ confirmation Surprises? Sterile 3 neutrinos cannot accommodate LSND Oscillation pattern(decay, de-coherence, ) se oscillation as a tool to study lepton sector Precision measurements of θ3 π/4? θ3 Solar sector θ, m CP violation Sign of m ( High E and Very Long baseline) 9

10 Why µ e P αβ = δ αβ 4 Re( j> i j> i * α i m Im( * α i β i β i α j α j * β j ) sin * β j ) sin (m (m j j 4E E m m i i )L )L = for α=β appearance exp! Recent developments toward CPV search CPV sinθ sinθ 3 sinθ 3 m (L/E) sinδ Solar LMA solution (large m, large θ ) Near max. mixing in atmospheric (θ 3 ~π/4)

11 µ e appearance & CPV Main CP-odd Solar δ δ, a -a for A CP P P + P P µ e m E L sin θ sinθ 3 sinδ a Matter Matter eff.: 5 ρ = E 7.56 [ev ] 3 [g cm ] [GeV] # of signal sin θ 3 (Stat err sinθ 3 ), CP-odd term sinθ 3 Sensitivity indep.. from θ 3 (if no BG & no syst.. err)

12 µ e oscillation probability sin θ 3 =. total θ 3 CP CP solar matter

13 CPV vs matter effect µ e osc. probability w/ CPV/matter 95km θ 3 =. Smaller distance/lower energy small matter effect Pure CPV & Less sensitivity on sign of m Combination of diff. E&L help to solve. 3

14 CP and mass hierarchy in neutrino factory 4

15 Possible approach to address CPV. Super- beam in low energy eperiments µ e versus µ e A larger detector than Super-K. Intense and beam. Super- beam + Reactor θ 3 measurements between super- beam and a reactor. The larger detector + a very precise reactor experiment. 5

16 . Possible CP measurements in TK LOI: hep-ex/69 Super-K: 5 kton Water Cherenkov ~Mt Hyper Kamiokande Kamioka µ beam of <GeV J-PARC (Tokai-village).75 MW 5 (4) GeV PS Approved exp (x of KK) µ x µ e appearance NC measurement disappearance Extension CP violation proton decay 4MW 5GeV PS Hyper Kamiokande ~36k µ CC/yr Small matter effect 6

17 beam Minimization of beam loss Increase harmonics, barrier bucket, etc.. more protons in the ring. Faster repetition rate see NP Web page ( 4MW beam line & target will be upgraded to accommodate 4MW 7

18 Conventional Neutrino Beam Proton Beam Target Focusing Devices π,k Decay Pipe µ µ Beam Dump Conventional neutrino beam with (Multi-)MW proton beam Pure µ beam ( 99%) e ( %) from π µ e chain and K decay(ke3) µ / µ can be switched by flipping polarity of focusing device Strongly motivated by high precision LBL osc. exp. 8

19 TargetHornsDecay Pipe High intensity narrow band beam -- Off-axis (OA) beam -- θ Decay Kinematics Far Det. (ref.: BNL-E889 Proposal) µ flux E (GeV) E (GeV) max 3 E [GeV] θ[mrad] 5 /γ π ~θ E π (GeV) Increase osc. max. Decrease background from HE tail 9

20 sensitivities for sin θ 3 Phase-with SK 9%C.L. sensitivities Off axis.5deg, 5GeV 5yr CHOOZ excluded exp d signal+bg total BG µ BG Off axis.5deg, 5GeV 5yr m =.5x - 3 ev, sin θ 3 =. sin θ reconstructed E (GeV) sin θ3 μ(cc+nc) Bean e Osc d e Signal+BG (OA.5deg, 5GeV 5yr)

21 Sensitivity for θ 3 sin θ 3 ~.8 (3σ) sin θ 3 ~.6 (9%).5xsin θ 3 sin θ 3 < - 3 can be searched if syst err ~ few %

22 Systematics on CP Selection of e events Low energy without HE tail ring e-like No decay electrons Visible Energy > MeV Tight e/π (NC) separation Reconstructed E by quasi-elastic e contamination Corrections matter effect (~7%), difference of spectrum (~5%) cross section detection eff.

23 / beam flux µ.%~.4% OAB (degree) µ-decay e µ ~5% diff. µ (flip horn polarity) K-decay 3

24 / CC interaction spectrum for CPV meas. N CC (/MeV/.5kt/year) cross section difference Wrong sign BG (x µ case) µ µ µ : years µ : 6.8 years 4

25 Near and Intermediate Detectors VERY Important to understand the neutrino flux at Kamioka for µ, µ, and e + e the neutrino interactions (cross section, q dependence, etc..) Efficiency for signal and background Background estimation the detector performance itself The detectors will be at 8m and ~km from the target. 5

26 number of e, e appearance events # of e + events include BG N(e + ) m 3 < # of e - events include BG 3σ stat only 3σ stat+% syst. N(e - ) sin θ 3 =. 9%C.L. stat only 9%C.L. stat+% syst. m 3 > CP phase 6

27 Sensitivity for CPV in TK-II 4MW, 54kt yr for µ 6~7yr for µ m =6.9x -5 ev m 3 =.8x -3 ev θ =.594 θ 3 =π/4 sin θ JHF-HK CPV Sensitivity stat+%syst. stat+5%syst. A CP m sin θ sin θ 4 E 3.8 sin δ.6 no BG.4 signal stat only. (signal+bg) stat only stat+%syst. TK 3σ discovery TK-I 9% sinδ 3σ CP sensitivity : δ > o for sin θ 3 >. with % syst. 7

28 Expected signal and BG (SK full sim) Very Preliminary sin θ 3 =. µ :yr, µ :6.8yr 4MW.54Mt m =6.9x -5 ev m 3 =.8x -3 ev θ =.594 θ 3 =π/4 θ 3 =.5 (sin θ 3 =.) signal background δ= δ=π/ total µ µ e e µ e µ e

29 More CP (beyond MNS) test NC π events ( + N + N + π ) Sensitive to τ flux can test µ τ vs µ τ Comparison of θ 3 from µ beam with a precise result from a reactor experiment if it exits. can test CP only with neutrino beam ( years) Measure the oscillation pattern in e events, and compare it with µ events. may observe additional contributions to θ 3 ( e3?) only. 9

30 pgrade of TK 3

31 Far Detector: Hyper-Kamiokande Need spec! Possible site for Hyper-K SK ~km HK detectors 48m 5m 5m, Total mass = Mton 3

32 Intermediate detector (~km from the target) In order to reduce the systematic uncertainty down to %, an intermediate detector will be necessary. The same spectrum at Kamioka (can apply the simple /r law for the flux estimation) A Water Cherenkov detector can be operated to minimize the systematic due to nuclear effects etc. (cf. too high rate at 8m). Fine grained scintillater tracker Water Cherenkov? Muon detector 3

33 Summary Systematic design efforts, based on KK, TK- The LMA solution of solar neutrinos, suggested by KamLAND, SK and SNO, has shown the CP violation in oscillation has benn can be observed The experiment with 4MW JAPC and Hyper-Kamiokande, the CP violation can be discovered for δ > and sin θ 3 >. with 3σ significance. nique opportunities for pure leptonic CP violation 33

34 Schedule of TK KK TK construction SK full rebuild PS commisionning physics run 34

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