Prospects of Reactor ν Oscillation Experiments

Transcription

1 Prospects of Reactor ν Oscillation Experiments F.Suekane RCNS, Tohoku Univ. Erice School 3/09/009 1

2 Contents * Motivation * Physics of Neutrino Oscillation * Accessible Parameters of Reactor Neutrinos * Possibilities of Reactor Neutrinos st Δm 13 Oscillation Maximum nd Δm 13 O.M. st Δm 1 O.M. nd Δm 1 O.M. * Summary

3 An exciting time is just around the corner... Huber et al., heo-ph/ Now What reactor experiments could do next? 3

4 Issues for ν oscillation & solving methods (1) sin θ 13 ()Mass Hierarchy (3)θ 3 degeneracy (4) CP violating δ (1) ν µ => (accelerator) () ν µ => (accelerator) (3) Matter effect (accelerator) (4) ν µ =>ν µ (accelerator) (5) => (reactor) (6) Solar, Atmospheric Reactor xperiments are cost-effective way to get important information. Construction($$$) +ν=$$ Construction($~$$) ν= free 4

5 Physics of ν Oscillation (a different view) Oscillation Formula: Neutrino Mixing: ( ) = sin θ sin Δ 1 ; Δ 1 m m 1 P ν µ ν 1 ν cosθ sinθ = ν e sinθ cosθ ν µ ( )L 4E Time evolution of mass eigenstate Mass eignstate ν Equation of Motion: i d dt ν µ = µ e A µe ν e A µe µ µ ν µ θ µ µ µ e A µe Flavor Transitions: ν µ ν µ Transition Amplitudes ν µ µ e µ µ Α µe 5

6 What we measure by ν Oscillation ν µ ν µ µ e µ µ ν µ P( ν µ ) = sin θ sin Δm L 4E tanθ = A µe µ µ µ e Δm = µ µ +µ e ( ) ( µ µ µ e ) + 4A µe θ µ µ µ e A µe Α µe Existence of ν Oscillation is an evidence of finite A µe Transition amplitudes can be determined together with absolute mass. 6

7 Purpose of ν Oscillation experiment Physics of ν oscillation is to measure the flavor transition amplitudes (<= experimentalist) and think of its origin (<= theorist). Now we know ν α ν β exists. Non Standard Higgs? H 0 Sub Structure?? For Example, d d G s s π η ~ η uu dd ss Or something else?? A NP? 7

8 3 Flavors case Transitions ν µ ν µ ν τ ν τ µ e ν µ ν τ ν µ ν τ ν µ Α µe ν τ Α τe ν µ Α µτ ν τ µ µ µ τ Α * µe Α * CPV phase τe Α * µτ Mixing ν µ ν τ U e1 U e U e3 = U µ1 U µ U µ 3 U τ1 U τ U τ 3 ν 1 ν ν c 13 0 s 13 e iδ c 1 s 1 0 = 0 c 3 s s 1 c s 3 c 3 s 13 e iδ 0 c ν 1 ν ν 3 Oscillation ( ) ( ) = δ 4 Re U αβ αi P ν α ν β P ν α ν β * * ( U βi U αj U βj )sin Δ ij Im U * * ( αi U βi U αj U βj )sinδ ij i> j i> j 8

9 U MNS ~ Our Current Knowledge m 3 m ~ ev, m m 1 ( ) ~ ev s 13 e iδ s 13 < 0. If m 3 >m >>m 1 ~0, ν µ ν µ ν τ ν τ µ e ~3meV µ µ ~30meV µ τ ~30meV ν µ ν τ ν µ ν τ A eµ ~(30s 13 e iδ +3)meV A eτ ~(30s 13 e iδ 3)meV A µτ ~0meV (charged lepton=mass eigenstate) 9

10 Reactor neutrino ν ν ν ν ν ν ν are produced in β-decays of fission products. ~ / s / reactor E ν ~ 4 +4 MeV σ( + p e + + n) 10

11 Accessible Oscillations by Reactor ν E-L Relation of Oscillation Experiments Up to now Future Reactor Prospect Reactor (~8MeV) Accelerator Bugey Goesgen PaloVerde CHOOZ DChooz DayaBay RENO Both Oscillations can be accessible E = Δm π L KK Opera MINOS TK NOVA KamLAND

12 P( ) = 1 cos 4 θ13 sin θ1 sin Δ1 sin θ13 (cos θ1 sin Δ 31 + sin θ1 sin Δ 3 ) KamLAND precise θ13 Reactor Neutrino Oscillation sinθ13=0.1 assumed 1. P(!e -->!e ) Normal Hierarchy 0.4 Inverted Hierarchy Δm L(km) Very precise θ 1 Mass Hierarchy

13 1 st Δm 13 Maximum (L~1.5km) ; θ Reactor Neutrino Oscillation P(!e -->!e ) L(km) P R ( ) 1 sin θ 13 sin Δ 31 Future xperiments strongly depends on θ 13 Precise measurement of θ 13 is very important. Parameter δ CP θ 3 degeneracy Mass Hierarchy Measurement Method [ P A ( ν µ ) P A ( ν µ ~ 0.1sinθ 13 sinδ 3 P A ( ν µ ~ 0.5sin θ 13 ± 0.05sinθ 13 sinδ [ P A ( ν µ ) + P A ( ν µ ~ sin θ 3 sin θ 13 3 ( ) L L ( ) P A ( ν µ ;L) + P A ν µ ; L [ ( ~ sign Δm 3 3 P R ( )sin θ 13 ( ~ 1 0.5sin θ 13 sin Δ 31 + tan θ 1 sin Δ 3 13

14 DoubleChooz, Dayabay, RENO Double Chooz Daya Bay RENO Double Chooz Dayabay RENO Power(GWth) 8.6GW 11.6GWth (17.4GW>011) 16.4GW Detector(ton) 8+8 0x4+(0x) 16+ Baseline(km) sin θ 13 Sensitivity ~0.03 ~0.01 ~0.0 Operation start 010/ Results: within ~5years 14

15 Complementarity of Reactor-Accelerator θ 13 measurement P AC θ 3 degeneracy 0.50 ± 0.11 ( ν µ ) = L km Matter effect ( [ ]) sin θ 13 ± 0.045sinθ 13 sinδ δ dependece L=300km by Yasuda Accelerator Measurement Reactor Measurement 15

16 Settlement of θ 3 Degeneracy P( ν µ ) K.Hiraide, et al. PRD73, (006) Accelerator 4MW*0.54Mt +6years sin Θ 3 Reactor: 100t * 0GW *5y P( ν µ ν µ ) P( ) Accelerator Only Accelerator+Reactor 16

17 3 rd Generation; More Precise θ 13 For higher statistics, θ 13 cam be measured by energy spectrum distortion and δsin θ 13 <0.01 is possible P.Hauber et al. hrp-ph/03033 RENO DC DB ton x 0GW x 5year

18 Quick Access to δ CP δ CP =-π/ δ CP =0 δ CP =π/ δsin θ 13 =0.005 If θ 3 degeneracy and Mass Hierarchy are solved, only δ remains to be solved. Combination of high precision Reactor-θ 13 and Accelerator appearance may determine non-0 δ before anti-neutrino mode operation. 18

19 Parameter region to determine non-0 δ Accelerator Reactor 10ton x 0GW x 5year 100ton x 0GW x 5year H.Sugiyama hep-ph/041109v1 If sin θ 13 >0.05 there is a possibility to determine non-0 δ 19

20 P(!e -->!e ) Δm 13 nd Maximum (L~5km) ( Δm 13 measurement) Reactor Neutrino Oscillation L(km) Δm 31 NH > Δm 3 m3 m m1 Δm 31 IH Δ 31 Δ 3 Δ 31 Δ 3 < Δm 3 m m1 m3 P R ( ) 1 sin θ 13 sin Δ 31 However, accurcy of δ Δm 31, Δm 31 In principle, Mass Hierarchy is accessible δ Δm 3 << Δm 1 ~ 3% are necessary. Δm 3 Δm 3 TK & Nova expected δ Δm 3 Δm 3 ~ 4% Need to improve θ 13 is necessary to evaluate δ Δm 13 (KamLAND case; δ Δm 1 Δm 1 ~.6% ) 0

21 1 st Δm 1 Maximum(L~50km) (Very Precise θ 1 & Mass Hierarchy) Example of Japan case 50km Focus point ΣP~47GW th 1. 1 Reactor Neutrino Oscillation P(!e -->!e ) L(km) 1

22 P R 1 st Δm 1 Maximum ( ) =1 cos4 θ 13 sin θ 1 sin Δ 1 ( ) +sin θ 13 cos θ 1 sin Δ 31 + tan θ 1 sin Δ 3 sin θ 1 Large Deficit Rrecise θ 1 Ripple Mass Hierarchy sin Δ 31 + tan θ 1 sin Δ 3

23 Precise θ 1 δsin θ 1 1 Λ L ( ), Λ= Deficit probability; Λ( L) = ( ) ~ 0.8 ( ) ~ 0.4 (KamLAND) Λ 50km Λ 180km P( ) ~ cos 4 θ ( 13 1 sin θ 1 sin Δ ) 1 H.Minakata, hep-ph/ f ν 1kton x5gw x.5y δ sin θ 1 sin θ 1 ( E)sin Δ 1 de ( E)dE δsin θ 1 ~ 1 ( δsin θ 1 ) KamLAND f ν & Low geo neutrino BKG (high ν flux) ~.4% ( 1σ ) Current Global fit δsin θ 1 sin θ 1 ~ 6.3% ( 1σ ) 3

24 Determination of Mass Principle Petcov et al., Phys. Lett. B 533, 94 (00) S.Choubey et al., Phys. Rev. D 68, (003) J. Learned et al., hep-ex/060 L.Zhan et al., hep-ex/ M.Batygov et al., hep-ex/ Ripple sin θ ( 13 sin Δ 31 + tan θ 1 sin Δ ) 3 Fourier Analysis => Power Spectrum Peaks at The smaller peak is and larger peak is Δm 3 It is essential that θ 1 is not maximum (tan θ 1 ~0.4) ω = Δm 31, Δm 3 Δm 31, Δ 3 Δ 31 ω Δm 31 > Δm 3 : Normal Hierarchy Δ 31 Δ 3 ω Δm 31 < Δm 3 : Inverted Hierarchy

25 J.Learned et al. arxive-0610 Inverted Hierarchy Normal Hierarchy Simulation of power spectrum If sin θ 13 =0.05, 3kton x4gw x yr, Mass Hierarchy can be determined with 1σ significance. L.Zhan et al.=> Mass Hierarchy could be determined if sin θ 13 >

26 Merit & Issues of this method. * Need not to know absolute m 3 so precisely. It is enough only to separate two peak positions. δe E < 3% E MeV * However, a good energy resolution; ( ) is necessary. Borexino case δe E ~ 5% E MeV ( ) improvement of light yield: x1.5 more PMT x1.8 with UltraBialkali photocathode δe E = 3% E MeV can be achieved ( ) * Energy smearing due to recoil neutron energy & baseline difference may degrade performance. => Need more studies for specific sites 6

27 DoubleChooz-50 RENO-50 L~50km experiment may be a natural extension of current Reactor-θ13 Experiments * θ13 detectors can be used as near detector * Small background from other reactors. DayaBay-50 7

28 Δm 1 nd Maximum(L~150km) P(!e -->!e ) Reactor Neutrino Oscillation L(km) If SK detector is filled with LS, >0 times more statistics than KamLAND Δm 1 = tan θ 1 = ( ) ( syst) ( stat) ( syst) ( ) ( syst) ( stat) ( syst) stat stat 8

29 1E+4 1E+3 1E+ Electron Antineutrino Event Rate at Kamioka Reactor f ν ( E ν ) σ E ν p e + n ν ( ) Inverse beta decay threshold Event rate (/year/kt//mev) 1E+1 1E+0 1E-1 1E- 1E-3 1E-4 1E-5 1E-6 1E-7 Geo- Solar (0.01%) from Past Super Novae Atmospheric 1E-8 1E+0 1E+1 1E+ 0kt KamLAND Antineutrino Energy (MeV) KamLAND 1 event/year sensitivity KamLAND detects any E>1.8MeV No Backgrounds >8MeV with 0Kton KamLAND pushes the limit 0 times better and may reach Relic SN. 9

30 Summary = Current = θ 13 : DoubleChooz, RENO, Dayabay are going to start in 010. δsin θ 13 =0.01~0.03 in a few years. = Future = L~1.8km, High Precision θ 13 ; M~100ton x 4GW th => δsin θ 13 <0.01 θ 3 Degeneracy with accelerator early sinδ detection with accelerator L=50km, M~3Kton x 4GW th, High Precision θ 1 ; Mass hierarchy determination L=180km 0Kton KamLAND??? It is important to discuss about the future strategy taking into account the reactor-accelerator complementarity after the 1 st phase θ 13 measurements. 30

31 Back up slides 31

32 Relation of mass, mixing & transition amplitudes ν µ µ e µ µ ν µ m 1 = 1 µ +µ µ e m = 1 µ +µ + µ e ( µ µ µ e) + 4A µe ( µ µ µ e) + 4A µe θ µ µ µ e A µe ν µ tanθ = A µe µ µ µ e Α µe Δm = ( µ µ +µ e ) ( µ µ µ e ) + 4A µe 3

33 P Accel ( ν µ ) P Accel ν µ ( ) P Re actor ( ) Reactor θ 13 helps to pin down parameters 33