2. Present Understandings Solar, Kamland MSW-LMA Atmospheric Oscillation! Decay, decoherence LSND and Sterile

Solar neutrinos (Non-historical)

Neutrino Production in the Sun Light Element Fusion Reactions p + p 2H + e+ + e 99.75 % p + e- + p  2H + e 0.25 % 3He + p 4He + e+ + e ~10-5 % 7Be + e- 7Li + e 15 % 8B  8Be* + e+ + e 0.02 %

Types of Experiments Radio-Chemical ft-value of b decay can give cross sections with a few % accuracy n +A(Z,,N)→e + A’(Z+1,N-1) Give rates 37Ar(g.s.) - 37Cl = 0.816MeV Convenient Ar life time (t = 35 days) 71Ge(g.s.)-71Ga=0.233MeV electron capture (t = 11.43 days)

Real time measurements Water Cherenkov Super-Kamiokande n +e → n + e well defined by standard model s (ne) ; s (nm,nt)=1:1/6 forward peaked Heavy water Cherenkov :SNO n + e → n + e Same as water n + d → e + p + p (CC) measure ne component, slightly backward peaked n + d → n + p + n (NC) same cross section for all neutrinos, thermalized neutron capture,

Sudbury Neutrino Observatory 2092 m to Surface (6010 m w.e.) PMT Support Structure, 17.8 m 9456 20 cm PMTs ~55% coverage within 7 m Acrylic Vessel, 12 m diameter 1000 tonnes D2O 1700 tonnes H2O, Inner Shield 5300 tonnes H2O, Outer Shield Urylon Liner and Radon Seal Energy Threshold = 5.511 MeV

Neutrino Reactions in SNO Produces Cherenkov Light Cone in D2O CC n + d  p + p + e− e Q = 1.445 MeV good measurement of ne energy spectrum some directional info  (1 – 1/3 cosq) ne only n captures on deuteron 2H(n, g)3H Observe 6.25 MeV g NC x n +  p d Q = 2.22 MeV measures total 8B n flux from the Sun equal cross section for all n types n +  + Produces Cherenkov Light Cone in D2O ES e− n e− x x low statistics mainly sensitive to ne, some n and n strong directional sensitivity

Shape Constrained Signal Extraction Results CC 1967.7 +61.9 +60.9 +26.4 +25.6 ES 263.6 +49.5 +48.9 NC 576.5 #EVENTS

Shape Constrained Neutrino Fluxes Signal Extraction in FCC, FNC, FES with E > 5.511 MeV Fcc(ne) = 1.76 (stat.) (syst.) x106 cm-2s-1 +0.06 -0.05 +0.09 -0.09 Fes(nx) = 2.39 (stat.) (syst.) x106 cm-2s-1 +0.24 -0.23 +0.12 -0.12 Fnc(nx) = 5.09 (stat.) (syst.) x106 cm-2s-1 +0.44 -0.43 +0.46 Signal Extraction in Fe, Fmt

SNO NC in D2O (April 2002) ~ 2/3 of initial solar ne are observed at SNO to be nm,t Flavor change at 5.3 s level. Sum of all the fluxes agrees with SSM. FSSM = 5.05 +1.01 - 0.81 106 cm-2 s-1 FSNO = 5.09 +0.46 -0.43 +0.44 -0.43 106 cm-2 s-1 Phys. Rev. Lett. 89 (2002)

What have been clarified NC measurement confirmed main sequence star calculation SNO-NC = 5.09 +0.44-0.43+0.46-0.43 SSM calc. =5.05 +1.01-081 . electron neutrino component for >5MeV reduced to ~35% of SSM

The Solar Neutrino deficiencies Experiment Exp/SSM SAGE+GALLEX/GNO 0.55 Homestake 0.34 Kamiokande+SuperK 0.47 SNO CC 0.35 We need survival probabilities of 8B: ~1/3 7Be: <1/3 pp: ~2/3 Hard to accommodate by vacuum oscillation

Definition of mixing angle and components Define n1, n2 such that m2 > m1 Dm2 >0 Small angle solution n1~ne, n2 ~ nx Large angle solution q>45o cos2q <0 equivalently negative Dm2 Ares (>0) =Dm2 cos2q is not realized Matter effect determine sign of (m22-m12)

MSW in the Solar neutrinos In(Dm2) m2 n2 m1 In(sin2q) Matter in earth may regenerate ne more events in the night!

Matter-Enhanced Neutrino Oscillations Pee Spectrum Neutrinos produced in weak state e High density of electrons in the Sun Superposition of mass states 1, 2, 3 changes through the MSW resonance effect Solar neutrino flux detected on Earth consists of e + m,t Day/night Spectrum

Super-Kamiokande Known 8B- b decay spectrum predict spectrum of neutrinos Spectrum distortion Day-Night comparison

Bad fit for SMA and Just-so(vacuum oscillation) solutions. (0.75, 6.310-11eV2) Justso (6.310-3, 510-6eV2) SMA (0.8, 3.210-5eV2) LMA Bad fit for SMA and Just-so(vacuum oscillation) solutions.

Energy distribution for day/night-6bins Z mantle core Day MAN5 CORE MAN4 MAN3 MAN2 MAN1 SK SK 1258 days 22.5 kt SSM = BP2000 + new B8 spec. (Preliminary)

zenith spectrum shape alone using SSM 8B  flux prediction SK Constraint on mixing parameters zenith spectrum shape alone using SSM 8B  flux prediction Excluded Regions Allowed Regions Phys. Lett. B (2002) 179

391-day salt phase flux measurements vertex SSM 68%CL SNO NC 68%CL SNO CC 68%CL SNO ES SK ES cosqsun ~ isotropy CC NC

global solar data with 391-day SNO salt

Kamland

KamLAND detector Photo - coverage: 34% ~ 500 p.e. / MeV 13m 1000m Cosmic ray 's are suppressed by 1/100,000. 20 inch : 225 13m 1,000 ton liquid scintillator Dodecane : 80% Pseudocumene : 20% PPO : 1.5g/l Mineral oil Dodecane : 50% Isoparaffin : 50% 1.75m thickness KamLAND is located 1000m underground in Kamioka mine, and muon event rate is about 0.34Hz. The detector consist of 1000 tons of ultra-pure liquid scintillator and 1879 PMTs 17 inch :1325 20 inch : 554 ~8000 photons / MeV λ: ~10m Photo - coverage: 34% ~ 500 p.e. / MeV

e e- Greatly removes backgrounds ν detection in KamLAND e+ Position e+ + n e (0.51) Prompt e+ signal e e- e+ Te++annihilation =Eν - 0.8MeV Te+ p E1.8MeV (0.51) n  (2.2 MeV) p Delayed γ by neutron capture ~210μs Position Time correlation delayed energy information Neutrinos are detected by the inverse beta-decay reaction. Space and time correlations of prompt and delayed signal provide effective background reduction. d Greatly removes backgrounds

Reactors near the KamLAND 80% of total contribution comes from 130~220km distance effective distance ~180km This map shows the location of the Japanese power reactors and KamLAND. And this figure shows distances from KamLAND to reactors and thermal power of reactors. 80% of total contribution comes from 130 ~ 220km distance. KamLAND group also calculate effects from reactors of other countries, Taiwan effect is about 0.1% Reactor neutrino flux, ~95.5% from Japan ~3% from Korea (2nd result period)

Energy Spectrum This figure shows energy spectra of KamLAND data, no oscillation expected, scaled no oscillation expected, and backgrounds. From the hypothesis test of scaled no-oscillation, spectral distortion is 99.6% confidence level. And we use rate with shape information, no oscillation is excluded at 99.999995% confidence level. Hypothesis test of scaled no-oscillation: χ2/ndf = 37.3/18 ⇒ spectral distortion at > 99.6% C.L. Rate + Shape: no oscillation is excluded at 99.999995% C.L.

L/E plot with data for geo-ν analysis (759 days, 5m fiducial) low energy window best fit reactor + geo-neutrino model prediction Oscillation pattern with real reactor distribution Lo = 180 km is used for KamLAND There is clear Oscillatory behavior (peak and dip) oscillation parameter is determined.

q12 -Solar(ne) and Reactor(ne) Neutrino - hep-ex/0406035

Two mass eigen-states have Dm2 ~8x10-5 eV2 Lighter mass state contain ne more than 50% 8

Atmospheric Neutrinos Mixture of ne, ne, nm & nm Primary cosmic rays nm+nm flux nm (protons, He, , ,) 3D calculation L=10~20 km p, K m 10-1 1 10 102 En(GeV) nm e p→m+nm →e+nm+ne Flux ratio Low EnergyLimit nm : ne = 2 : 1 ne nm nm+nm ne+ne 2 10-1 1 10 102 En(GeV)

Event topology ne + N  e + X nm + N  m + X nt + N  t + X PC FC PC Initial neutrino energy spectrum Stopping muons Through-going muons FC + PC Interaction in the rock stopping muons through-going muons

A half of nm lost!

p=1 GeV/c, sin2 2q=1 Dm2=310–3(eV/c2)2 Earth ~6000 km Survival Probability p=1 GeV/c, sin2 2q=1 Dm2=310–3(eV/c2)2 Half of the up-going ones get lost

Cross Section of nt interacts very weakly with matter (nucleons) due to threshold effect of charged lepton mass Disappearance of neutrinos if nm→nt in atmospheric n nm CC nt CC En(GeV)

SK-I Zenith angle distributions (w/ 100yr MC) SK-I Atmospheric n Full Paper hep-ex/0501064 1R e 1R m MR m up-m <400MeV <400MeV sub-G stopping 1R e 1R m MR m up-m Number of events >400MeV >400MeV multi-G through 1R e 1R m cosQ data PC CR MC F? s? multi-GeV multi-GeV w/ oscillation fit cosQ cosQ cosQ up down

L/E analysis and Parameter determination All the data 1489.2days Data/prediction 100 1000 L/E (km/GeV) Rejected events horizontally going events:  due to large dL/dcosq low energy events:  due to large qnm angle Guide line L/E (km/GeV) Data/prediction 2726 events (3726 ev. expected) ~ 1 /5 of total data

Result of L/E analysis (SK-I) The first dip has been observed at ~500km/GeV This provide a strong confirmation of neutrino oscillation The first dip observed cannot be explained by other hypotheses 1489.2 days FC+PC Decoherence Decay 50 60 70 80 90 (%) Resolution Cuts vs Dc2 Dc2 Mostly PC through-going Decay rejected at 3.4 sigma Decoherence rejected at 3.8 sigma Oscillation 3.4 s to decay 3.8 s to decoherence

Constraint on the neutrino oscillation parameters from L/E analysis Best Fit (Physical Region) Dm2=2.4x10-3,sin22q=1.00 c2min=37.8/40 d.o.f. (sin22q=1.02, c2min=37.7/40 d.o.f) Dm2 Allowed region (@90%C.L.) 1.9x10-3 < Dm2< 3.0x10-3 eV2 0.90 < sin22q Consistent with the standard zenith angle analysis 1.5x10-3 < Dm2 < 3.4x10-3 eV2 0.92 < sin22q (@90%C.L.)

nm →Sterile ?

matter effect in the earth for sterile neutrinos PC, Evis>5GeV <Eν>～25GeV up/down ratio ns ns Z νμーνs νμーνs n νμーντ νμーντ up through going μ <Eν>～100GeV vertical/horizontal ratio n Compare high-low energy events

Three Flavor Mixing in Lepton Sector mass eigenstates Weak eigenstates m1 ne m2 nm nt m3 cij = cosqij, sij=sinqij Atm. Sol. q12, q23, q13 + d (+2 Majorana phase) Dm122, Dm232, Dm132

q13

CHOOZ 425 GWth L=1km 5t Liquid Scintillator H richparaffin Gd loaded (g 8MeV) sin22q13 <0.10 9° 90%CL sin22q13 <0.17 12°

Two mass eigen-states have Dm2 ~8x10-5 eV2 Define n1, n2 such that mn2 > mn1 Solar n MSW in neutrino (not anti-neutrino) n1 is the largest component in ne Third mass eigen-sate (n3) is separated by Dm2 ~ ±3x10-3 eV2 Small ne component in n3 (n3 consists of nm, nt, almost 50;50) which is larger in nt ? (q23<p/4 ?) neutrino mass and charged lepton mass ordering same or inverted 8 atm. 3x10-3eV2

LSND/KARMEN Experiment

The LSND Experiment View of the PMTs inside the detector vessel. (Vessel is filled with scintillator oil.)

Decay at Rest (DAR) Signal Prompt e+ Delayed g from n-capture Small intrinsic ne contamination few x 10-4

Gamma Ray Distribution

LSND Final Results

ISIS and KARMEN

KARMEN Distributions

KARMEN and LSND

‘Evidence’ of oscillations Cannot be accommodated in three neutrinos sin2 2q Dm2 (eV2) nmne nenm,nt nmnt (m22 –m12) +(m32 –m22)+ (m12 –m22)=0 ; need more than 3 mass eigen-states number of neutrinos, which couple to Z is 3 Sterile n or exotics or faulty experiment First, existence of the LSNDeffect…..

MiniBooNE Overview

MiniBooNE Flux

Approximate number of events and Background expected in MiniBooNE nm Charged Current, Quasi-elastic 500,000 events Intrinsic νe (from K&μ decay) : 236 events Background π0 mis-ID: 294 events (Neutral Current Interaction) Other νμ mis-ID: 140 events Signal LSND-like nmne signal: 300 events

Particle Identification: m, e, and p0 Neutrino interactions in oil produce: Prompt Čerenkov light in a cone centered on the track. Delayed scintillation light distributed isotropically. Čerenkov to scintillation ratio ~ 4 to 1 Particle ID is based on ring fuzziness, track length, ratio of prompt/late light. Fuzzy rings distinguish electrons from muons. p0 look like 2 electrons (usually) Short Exiting

Sensitivity to a Signal Mis-ID Intrinsic νe Δm2 = 1 ev2 Δm2 = 0.4 ev2

Present constraints Dm13, q13 Dm12, q12 Dm23, q23 SK Atm n K2K Reactor K2K SK Atm n K2K Dm122 (10-5eV2) sin22q13<~0.15 (q13<~10deg) @Dm13~2.5x10-3eV2 Dm13 unknown sin22q23 > 0.93 2.1 < Dm232 < 3.0×10-3eV2 (SK Zenith 90%CL)