Neutrino Oscillation. Matthew Posik. Temple University

Transkriptio

1 Neutrino Oscillation Matthew Posik Temple University 1

2 Neutrino Oscillation What is neutrino oscillation Evidence for neutrino oscillation Future experiments 2

3 Solar Neutrino Problem Raymond Davis, Jr s Homestake Experiment (late 1960 s): collect and count neutrinos emitted from the sun Used a tank of 100,000 gallons of chlorine rich liquid, which upon neutrino collision emitted a radio active argon isotope Detected only 1/3 of the predicted (John Bahcall) neutrino flux! Results later verified by several independent experiments (Kamiokande, Gallex, ect) 3

4 U= Enter Bruno Pontecorvo Pontecorvo developed idea of neutrino oscillations (~1960) Neutrino oscillations due to mismatch in flavor and mass eigenstates να> = i U αi νi> (1) νi>= α U αi να> (2) Where for three neutrinos α = e, µ, τ are definite flavor and i = 1,2,3 are definite masses. Uαi is the Maki-Nakagawa-Sakata (MNS) matrix. For three neutrino flavors Ue1 Ue2 Ue3 Uµ1 Uµ2 Uµ3 Uτ1 Uτ2 Uτ3 = c12 s23 0 s23 c23 c13 0 s13e iδ s13e iδ 0 c13 c 12 s12 0 s12 c e iα e iα Neutrino mass, mixing and flavor change, B. Kayser (Fermilab)

5 Flavor Change Probability Consider how a neutrino born according to eq. (1) evolves in time. Apply Schrödinger's equation: νi(τi)>=e im iτi νi(0)> (mass frame) In lab frame, and treating the neutrino highly relativistic, the phase factor becomes: e i(m iτi)=e i(e it pil) e i(m i 2 2p )L να(l)> i U αi e i(m i 2p )L νi> (3) 2 Inverting (1) and putting it into (3) : να(l)> β [ i U αi e i(m i 2p )L Uβi] νβ> 2 (4) Neutrino mass, mixing and flavor change, B. Kayser (Fermilab) 5

6 Flavor Change Probability So the probability of a flavor change: P(να νβ)= <νβ να> 2 =δαβ 4 (i>j) R(U αi UβiUαjUβj )sin 2 ( m ij 2 L 4E ) +2 (i>j) I((U αi UβiUαjUβj )sin 2 ( m ij 2 L 2E ) ; mij 2 =mi 2 mj 2 Sinusoidal dependence on L/E and mass difference Neutrino oscillation introduces neutrino mass Neutrino mass, mixing and flavor change, B. Kayser (Fermilab) (5) 6

7 Flavor Change Probability If CPT invariance holds P(να νβ)=p(νβ να) Then P(να νβ;u)=p(νβ να;u ) If U is not real, then the probabilities of the neutrino and anti-neutrino can differ. This can be seen in the last term of eq. (5). If such a probability difference is seen, and CPT invariance holds, then CP would be violated. 7 Neutrino mass, mixing and flavor change, B. Kayser (Fermilab)

8 Atmospheric Neutrino Oscillation (Super-Kamiokande) Located in Mozumi mines in Japan Measure muon neutrino disappearance as a function of L/E and constrain the mixing angle. Survival Probability: P(νµ νµ)=1 sin 2 2θsin 2 ( 1.27 m2 (ev 2 )L(km) E(GeV) ) 8 Y. Fukuda et al. [Super-Kamiokande Collaboration], arxiv: hep-ex\ v1 (2004).

9 Super-Kamiokand Cherenkov Detector 50 kton water PMTs Inner detector (ID) Outer detector (OD) 1000m 9

10 Super- Kamiokande Results 1.9x10 3 ev 2 < m 2 <3.0x10 3 ev 2 ;sin 2 2θ>0.90 at 90% Y. Fukuda et al. [Super-Kamiokande Collaboration], arxiv: hep-ex/ v1 (2004). 10

11 KamLAND Reactor Anti- Neutrinos Located in the Kamioka mines in Japan Determine if antineutrino disappearance is present Anti-neutrinos created from radioactive decays Electron antineutrinos are detected through inverse beta decay νe+p e + +n 11

12 KamLAND Reactor Antineutrino Detector Stainless steel Vessel 13m D, nylon balloon w/pmt 1 kton liquid scintillator Water Cherenkov Detector Non scintillating oil 12

13 KamLAND Results m 2 = x10 5 ev 2 ;tan 2 θ= T. Araki et al. Phys. Rev. Lett. 94, (2005). 13

14 KamLAND Results (2008) arxiv: v2 14

15 What is Next m 2 atm m2 θ atm θ θ /-7o 33.9 o+2.4o 2.2 o < 3.2 o More precise measure of masses and mixing angles (θ13) Determine neutrino mass spectrum Search for CP violation Limit from the Solar and KamLAND Experiments, Phys. Rev. C 72, (2005); Kielczewska, Acta Phys. Pol. B 38 (2007) 15

16 Neutrino Mass Spec. 16