Recent Neutrino Results

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Recent Neutrino Results
European Physical Society HEPP2005

• Brief Overview
• Solar Sector
• Atmospheric Sector
• Neutrinoless Double Beta Decay

Josh Klein, University of Texas at Austin
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What Weve Learned in Past 10 years

• ns change flavor as they travel through vacuum
  and matter

Neutrinos are produced weak interaction (flavor)
eigenstates (ne,nm,nt) but propagate in mass
eigenstates (n1,n2,n3)
Remarkably, survival probability is
well-described by two-flavor approximation
(vacuum only)
But n Standard Model assumes three flavor mixing
as in quark sector
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What Weve Learned in Past 10 years

• atmospheric mixing angle qijq23 is maximal
  (45o)
• atmospheric Dm223 is 2.5x10-3 eV2
• solar mixing angle qijq12 is large (33o)
• solar Dm212 is 8x10-5 eV2
• cross mixing angle qijq13 is small (lt12o)
• cross Dm213 is Dm213Dm223-Dm212Dm223
• The Sun works!

Beam of nms will later be ½ nts.
Gateway to CP violation
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What Weve Learned in Past 10 years

• Mixing Summary

B.Kayser, FCP05
Dont know yet absolute offset for m
(direct searches from tritium b-decay)
(cosmological datamodel)
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So What?
Doesnt this make neutrinos just like the other
fundamental fermions?
Not quite

• n masses are much smaller than other particles

Hints at new mass-generating mechanism
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So What?
Doesnt this make neutrinos just like the other
fundamental fermions?
Not quite

• n mass may require addition of fields to SM
  Lagrangian
• e.g.
• n mass allows (Majorana neutrinos,
  )

Which in turn allows new CP-violating phases
Majorana CP heavy NR Origin of
matter/antimatter asymmetry?
7
So What?
Doesnt this make neutrinos just like the other
fundamental fermions?
Not quite

• n interferometry probes flavor non-diagonal
  processes

For example, when traveling through matter
Simple approach
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So What?
Doesnt this make neutrinos just like the other
fundamental fermions?
Not quite

• n interferometry probes flavor non-diagonal
  processes

Hamiltonian matrix now has new matter
eigenvalues and vectors
Which evolve again as
But with
and
Resonance when
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And

• LSND Experiment

4.1s appearance signal using from stopped
ps
J. Conrad, FCP05
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But

• LSND Experiment

But CERN tells us there are just 3 light, active
neutrinos
2.5 x 10-3 eV2
8 x 10-5 eV2
So we either have (at least) one sterile n, or
something more exotic (or LSND is just wrong).
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Todays Experimental Goals

• Measure mixing parameters (esp. unknowns q13 and
  dCP)
• Test the oscillation model
• Resolve the mass hierarchy
• Determine magnitude of at least one mn
• Demonstrate Majorana or Dirac hypothesis
• Resolve LSND Anomaly
• Use neutrinos as astrophysical probes
• Look for the unknown

• this talk

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Recent Solar Sector Measurements

• Sudbury Neutrino Observatory

Before SNO
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Recent Solar Sector Measurements

• SNO n Reactions

1000 tons of D2O 2 km underground
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Recent Solar Sector Measurements

• Phase I Pure D2O
• Simple detector configuration, clean measurement
• Low neutron sensitivity
• Poor discrimination between neutrons and
  electrons
• Phase II D2O NaCl
• Very good neutron sensitivity
• Better neutron electron separation
• Phase III D2O 3He Proportional Counters
• Good neutron sensitivity
• Great neutron/electron separation

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Recent Solar Sector Measurements

• SNO Phase III Results

• Phase I
• Phase II

But the new neutrino model makes other
predictions besides fluxes
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Recent Solar Sector Measurements

• MSW (Matter Effect) Phenomenology

Day/Night ne Asymmetry
Day/Night Asymmetry
s(nm,t) 0.155s(ne)
Rise of survival probability at low Tn
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Recent Solar Sector Measurements

• SNO MSW Results

Day/Night Asymmetry
Spectrum
Day/Night Asymmetry
A 0.0370.040
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Recent Solar Sector Measurements

• SNO Search for Solar n Flux Periodicity (New)

Controversial claims of periodic signals in solar
n data sets---
Could indicate coupling of mn to varying solar B
field
SNO search using both binned and unbinned methods
sees no evidence for periodic behavior from
f1/day to f1/10 years.
S. Oser, EPS/HEPP2005
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Recent Solar Sector Measurements

• Super-Kamiokande

40 kTon H2O Cerenkov
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Recent Solar Sector Measurements

• Super-Kamiokande I Results

M. Vagins, EPS/HEPP2005
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Recent Solar Sector Measurements

• Super-Kamiokande II Results

Excellent agreement with S-K I results
M. Vagins, EPS/HEPP2005
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Recent Solar Sector Measurements

• Super-Kamiokande MSW Results

S-K II ADN 0.0140.049(stat.)0.024(sys.)
-0.025
M. Vagins, EPS/HEPP2005
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Recent Solar Sector Measurements

• Super-Kamiokande MSW Results

M. Vagins, EPS/HEPP2005
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Recent Solar Sector Measurements

• Solar Mixing Parameter Summary

All Solar Data
So far, it seems that Nature has picked out just
about the only point where wed miss a direct MSW
signature
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Recent Solar Sector Measurements

• KamLANDBack to the Vacuum

Solar data
This is the best fit value of the vacuum mass
difference and mixing angle under the hypothesis
that observations are due to MSW (matter)
oscillations.
But if we plug these values into the vacuum
survival probability
We find that oscillation length L70 km for E4
MeV.
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1000 tons of liquid scintillator
ne p ? e n
J.S. Ricol, EPS/HEPP2005
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KamLAND, PRL 90, 2003
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Recent Solar Sector Measurements

• KamLAND Testing the Model with L/E Behavior

• Rate Shape Oscillations at 99.999995 C.L.

KamLAND, PRL 94, 2005
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Recent Solar Sector Measurements

• KamLANDSNO Testing the Model

KamLAND, PRL 94, 2005
Only(?) n Standard Model predicts these 2
experimental regimes see the same effect
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Recent Solar Sector Measurements

• KamLANDSolar Measuring n(1,2) Parameters

Solar alone
SolarKamLAND
(Maximal mixing excluded at gt5 s)
KamLAND best-fit (rate shape)
Solar
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Recent Atmospheric Sector Measurements

• Super-Kamiokande

Cant measure En or Ln, but can look at
cosqzenith in bins of Elepton
D. Casper, SLAC Summer Inst. (2004)
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Recent Atmospheric Sector Measurements

• Zenith angle distributions showing nm
  disappearance

upgoing
M. Vagins, EPS/HEPP2005
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Recent Atmospheric Sector Measurements

• Zenith angle distributions showing nm
  disappearance

S-K II 627 live-days
upgoing
downgoing
M. Vagins, EPS/HEPP2005
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Recent Atmospheric Sector Measurements

• Testing the Model L/E Behavior

New (S-K II Data)
decoherence
decay
best-fit osc (favored by gt3 s)
"the dip"
Preliminary
K. Scholberg, WIN05
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Recent Atmospheric Sector Measurements

• Mixing Parameters

Best Fit Results Dm2 2.1 x 10-3 eV2
sin2(2q) 1.0 (constrained to physical
region) c2min 174.8/177 DOF
Best Fit Results Dm2 2.5 x 10-3 eV2
sin2(2q) 1.0 (constrained to physical
region) c2min 375.2/367 DOF
Preliminary
K. Scholberg, WIN05
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Recent Atmospheric Sector Measurements

• K2K Long Baseline Accelerator (KEK to Kamioka)

First long baseline accelerator experiment
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Recent Atmospheric Sector Measurements

• K2K Long Baseline Accelerator (KEK to Kamioka)

Near Detector
SciBar
Critical to both measure flux and allow
extrapolation to Super-K
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Recent Atmospheric Sector Measurements

• K2K Long Baseline Accelerator (KEK to Kamioka)

Best Fit Results Dm2 2.8 x 10-3 eV2
sin2(2q) 1.0 (constrained to physical region)
K. Scholberg, WIN05
Total 107 beam events observed expect
149.7
No-oscillation excluded at gt4s
Single-ring m-like events
Consistent with SK atmospheric n's
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Checking the LSND Anomaly

• MiniBooNE

Results expected end of 2005
If signal, possible new stopped p experiment at
SNS
M. Shaevitz, WIN05
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Majorana Nature and mn

• 2nbb vs. 0nbb

e-
ni
ni
e-
e-
e-
ni
W-
W-
W-
W-
N
N
N
N
Nuclear matrix element (not OK)
Phase space (OK)
Mass is mixed average
Allowed in some even-even nuclei
S. Elliott, SLAC Summer Inst. (2004)
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0nbbMajorana Nature and mn

• Desired Limits

Lower bound to heaviest neutrino
But the bad news is that mixing
is small if m3 is heaviest state q13lt12o ?
We hope that either hierarchy is inverted or
masses are somewhat degenerate.
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0nbbMajorana Nature and mn

• Experimental Challenges

• Big mass for lifetime sensitivity
• Low radioactive backgrounds
• Good energy resolution to avoid 2nbb
  background
• Various species to avoid matrix element
  uncertainties
• Various technologies to avoid unexpected
  systematics

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Recent 0nbb Results

• NEMO3

In Frejus _at_4800 meters water equivalent

• Basic approach is to use
• tracking for background rejection
• calorimetry for energy resolution
• multiple isotopes for systematics

L. Simard, WIN05
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Recent 0nbb Results

• NEMO3

L. Simard, WIN05
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Recent 0nbb Results

• CUORE

• Basic approach
• Bolometry to give excellent energy resolution (5
  keV)
• TeO2 crystals for low radioactivity
• Segmentation for background rejection
• Gran Sasso to get away from cosmics

M. Pavan, WIN05
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Recent 0nbb Results
Pavan

• CUORE

M. Pavan, WIN05
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Summary

• Precision measurement era beginning for
  neutrinos
• First real tests of the model are underway
• Just starting to probe exciting region for 0nbb
• Many surprises possible!---see next F. Sanchezs
  talk