Transcript Status,_results_and_future_prospects_on_the

Status, results and
future prospects on the
neutrino oscillation
experiments
“The new, the rare and the beautiful”
Zürich, 6th-8th January 2010
F. Juget, LHEP Bern
Neutrino oscillation
experiments
• The 1rst idea of neutrino oscillations was put forward by
Pontecorvo in 1957
• First experiment Homestake in 1967 using solar neutrino
leading to the so-called “Solar Neutrino Problem”
• Natural neutrino sources
– Solar neutrinos
• Homestake, SAGE/GNO, Super-Kamiokande, SNO, Borexino
– Atmospheric neutrinos
• Super-Kamiokande
• Artificial neutrino sources
– Reactor neutrinos
• Chooz (1 km), KamLAND (180 km)
– Long baseline accelerator experiments
• K2K (250km), MINOS (730 km), OPERA (730 km)
3-flavour oscillation parameters
The neutrino oscillation probability depends on the
4 mixing parameters (θ23, θ12, θ13, dcp), the masses
differences (Dm2ij = m2i - m2j) and the energy E and
the distance L from the source (matter effect).
θ12
 id

 c12 s12 0  1 

1
0
0
c
0
s
e
 e 

13
13

  

 
1
0   s12 c12 0  2 
     0 c23 s23  0
   0  s c   s eid 0 c  0
 
0
1
23
23 
13
13 
  
 3 
Flavor
eigenstates
θ23
θ13, δ
Cij = cos(qij)
Sij = sin(qij)
Mass
eigenstates
Oscillation probability
P( e e)
L/E
Neutrino flavor at L is given by lepton identification in CC interaction
Solar neutrinos experiments
Experiments only sensitive to
e flavor (CC interaction)
Homestake – SK - Gallex/GNO - Sage
Deficit of predicted e flux
is measured
“Solar Neutrino Problem”
Predicted 
pp
7Be
Measured 
Gallex/Sage
8B
Cl
SK
Solar neutrinos experiments
• SNO: Experiment sensitive to 3 flavors
CC
 e + d  p + p + e−
NC
 x + d  p + n + x
- measures total 8B  flux from the Sun
- equal cross section for all active  flavors
ES
 x + e−   x + e−
(CC+NC interactions)
Solar neutrinos experiments
• SNO: Experiment sensitive to 3 flavors
(CC+NC interactions)
 predicted
 measured
In 2001, deficit of e flux is also measured, but the total flux is
measured using the 3 flavors
 absence of deficit
 Neutrino oscillates
e
,
Solar neutrinos experiments
Confirmation with the KamLAND experiment (reactor
258 events observed
365.2 ± 23.7 expected
(Disappearance confirmed at 99.99%)
5
Dm2  7.59+00..19

10
eV2
21
q12  34.4+11..23
degrees
Phys.Rev.Lett.101:111301,2008
SOLAR + KAMLAND (Reactor ’s)
’s)
Atmospheric neutrinos experiments
• «up-down» symetry of the flux
• L is linked to zenith angle θ
• Flux mainly
(

 /e ~ 2
for high energy
for E < 1 GeV)
Atmospheric neutrinos experiments
Super-Kamiokande
• L/E dependance
• The observed deficit favors the
   oscillation
(No appearance of e flavor is observed)
1.9 103< Dm223 < 3.0 103 eV2
sin22q23 > 0.9
(90% CL)
Atmospheric neutrinos experiments
Confirmed by K2K (accelerator neutrino’s)
112 events observed
158.1 ± 9 expected without oscillation
1.9 103< Dm223 < 3.5 103 eV2
for sin22q23  1
(90% CL)
Atmospheric neutrinos experiments
• Confirmed by MINOS (accelerator neutrino’s)
Atmospheric neutrinos experiments
• Global results with Super-K, K2K and MINOS data
The CHOOZ experiment
• Mesurement of the e flux from nuclear reactor (at 1km)
– Search for e disappearance
No observation of oscillation
ex
Confirmation of the non observation of
e from atmospheric neutrinos
 Limite on q13
sin22q13 < 0.1
 q13 < 11°
(90% CL)
3-flavor oscillation parameters
Where are we?
What do we know:
- There are three families of active, light neutrinos (LEP)
- Solar neutrino oscillations:
q12 ~300 Dm122~7 10-5eV2
- Atmospheric ( > ?) oscillations:
q23 ~450 Dm232~ 2.5 10-3eV2
- Electron neutrino oscillations are small:
q13 <100
What we do not know:
- Several unknown parameters:
q13 (only a limit)
dcp
mass hierarchy sign(Dm232)
- Why q12 and q23 angles are large and q13 seems very small or null ?
- Is there any CP violating phase in the mixing matrix ?
- Absolute mass values?
(beta or double beta experiments)
Where do we go?
• What is currently running
• Improve the precision on the atmospheric parameters q23 and Dm232
  disappearance:
  appearance:
MINOS (also
e appearance)
OPERA
• Short term (in the next years 2010-2015)
•
q13 measurement q13 < 3°_
_
- reactor experiments (e →e)
Double-Chooz, Daya Bay, Reno
-

Superbeam experiments: ( 
→e)
T2K, NOA
• Longer term (>2015?)
• New beams:
b-beam, -fact
q13, CP violation dcp , mass hierarchy
sign(Dm232)
The OPERA experiment
Goal: First observation of  appearance in a pure μ beam
• CNGS (CERN to Gran Sasso) beam
νμ beam tuned for the τ appearance at LNGS (730 km away from CERN)
Mean νμ energy : 17 GeV
Requested to deliver : 22.5 x 1019 pot (5 years)
The OPERA detector is installed in LNGS (Italy) which is
the largest underground laboratory in the world
3
The OPERA experiment
Goal: First observation of  appearance in a pure μ beam
• CNGS (CERN to Gran Sasso) beam
νμ beam tuned for the τ appearance at LNGS (730 km away from CERN)
Mean νμ energy : 17 GeV
Requested to deliver : 22.5 x 1019 pot (5 years)
The OPERA detector is installed in LNGS (Italy) which is
the largest underground laboratory in the world
• The OPERA target
Basic component: OPERA Brick = 57 nuclear emulsion films interleaved by 1 mm thick lead plates
Emulsion
Film : 2 emulsion layers
(44 m thick)
poured on a
205 m plastic base
10.2 cm
(δx~1 μm δθ~1 mrad)
12.5 cm
8.3 kg
7.5 cm
Plastic base
3
The OPERA experiment
Goal: First observation of  appearance in a pure μ beam
• CNGS (CERN to Gran Sasso) beam
νμ beam tuned for the τ appearance at LNGS (730 km away from CERN)
Mean νμ energy : 17 GeV
Requested to deliver : 22.5 x 1019 pot (5 years)
The OPERA detector is installed in LNGS (Italy) which is
the largest underground laboratory in the world
• The OPERA target
Basic component: OPERA Brick = 57 nuclear emulsion films interleaved by 1 mm thick lead plates
Emulsion
Film : 2 emulsion layers
The OPERA target is composed of 150,036 bricks
(44 m thick)
Total target mass : 1.25 kt
10.2 cm
(δx~1 μm δθ~1 mrad)
12.5 cm
8.3 kg
7.5 cm
poured on a
205 m plastic base
Plastic base
3
The OPERA experiment
Charm events from
2009 run
1300 m
500 m

 4.3 GeV
similar topology for
 event
First  event
expected in 2010
Primary vertex
 CC with 4 prongs
Secondary vertex
Charged Charm decay into 3 prongs
Charm flight length: 4.4 mm
q13 measurement
• Hint of q13 >0 in current data?
From solar+reactor+atmospheric
From MINOS
Not really conclusive, effect is 1 or 1.5 s
Early evidence or discovery with T2K or reactor exp.
q13 measurement
• Two complementary approaches:
_
•
e disappearance reactor experiments: Double Chooz, Daya Bay, Reno
- Depends on sin2(2q13) & Δm312, weakly on Δm212
- Measurement is independent of dCP
- negligible matter effect (1km) - independent of sign(Dm213)
”clean” θ13 measurement
But neutrino beam is not well know (need near and far detectors)
Systematic error dominant
•
e appearance in  beam:
T2K (250 km), NOA (810 km)
- Pe is a complicated function depending on various parameters
-
θ13 measurement is correlated with dCP and sign(Dm213)
T2K experiment
• Main goal: Discovery of non-zero θ13
– Increase the current sensitivity by a factor ~10
Off-axis beam (2.5°)
Quasi-monochromatic  beam
L/E tuned for max sensitivity
Small fraction of e
Reduced high-E non-CCQE bckg
Near detector (ND280)
(beam characterization)
Far detector
(Super-Kamiokande)
250 km from source
Cherenkov detector
50 kton Water
20” PMT x 11000
Data taking
Starts in 2010
T2K experiment
Far detector – Super-Kamiokande
T2K experiment sensitivity
The next 5 years
• If sin22q13>0.01
– evidence very soon
– firm observation by 2015
– CP search will be open:
new detectors, upgraded beams
•If no evidence by 2015
–Need new types of facility (-factory, b-beam)
– measure the value of dCP (if q13≠0!)
– determine the mass hierarchy - sign(Dm213)
effect)
(earth matter
Conclusion
• Still unknown oscillation parameters: q13 dcp
sign(Dm213)
– The others are measured with some accuracy
• Upcoming reactor and accelerator neutrino
experiments will reach sin22q13~0.01 (within 5 years)
• Even with upgrades these
experiments most likely
cannot say much on CP
violation and Mass Hierarchy
– Need new facility and detectors
(> 2015?)
(remark: Not taken into account LSND results)
The oscillation probability including matter effect
All effects are driven by θ13 !
P   e
Neutrinos
Anti Nu
(  
Dm L
D
4E
( 
sin (Aˆ D  sin (1  Aˆ D 
+
  sin q  sin d sin D
(1  Aˆ 
Aˆ
sin (Aˆ D  sin (1  Aˆ D 
+  sin q  cos d cos D
(1  Aˆ 
Aˆ
sin (Aˆ D 
+  cos q sin 2q
sin 2 1  Aˆ D
 sin 2q13 sin q 23
2
ˆ
1 A
2
2
2
13
Oscillation phase
dominant « on peak »
13
CP
13
CP
2
2
2
2
23

12
Aˆ 2
E
ˆ
A  2 2GF ne
Dm132
Dm
Dm
2-3 10-2
2
21
2
13
  cosq13 sin 2q12 sin 2q 23  (1)
Matter effect sensitive to :
• Sign of Δm213
• neutrino versus anti-neutrino
For the special case of   e oscillations, we have:
In vacuum, at leading order:
Pin down CP phase and mass
hierarchy
A.Ereditato – Neuchatel 21-22 June 2004
Detecting CP violating effects
Best method:
(in vacuum)
it requires:
however…
Dm212 and sin2q12 large (LMA solar): OK !
larger effects for long L: 2nd oscillation maximum
sin22q13 small: low statistics and large asymmetry
sin22q13 large: high statistics and small
asymmetry
…and:
impact on the detector design
oscillations are governed by Dm2atm , L and E:
E  5 GeV  L  3000 km
flux too low with a conventional LBL beam
A.Ereditato – Neuchatel 21-22 June 2004
Mass hierarchy from matter oscillations
Neutrinos oscillating through matter (MSW effect):
- different behavior of different flavors due to the presence of electrons in the medium
- additional phase contribution to that caused by the non zero mass states.
- asymmetry between neutrinos and antineutrinos even without CP violating phase in the matrix
- the related oscillation length LM, unlike LV (vacuum), is independent of the energy
- as an example LM (rock) is ~ 10000 km while LM (Sun) ~ 200 km
In the limit of Dm2sol approaching zero (for which there are no CP effects) and of running at the
atmospheric oscillation maximum, the asymmetry between neutrinos an antineutrinos equal to
with
By the measurement of this asymmetry one can determine whether Dm223 is positive or
negative (hierarchy)
e
3

 
2
Dm2atm
2
1
A.Ereditato – Neuchatel 21-22 June 2004
1
Dm2sol 3
Dm2sol
Dm2atm
For E ~ ER large amplification of P(e) at long distances
A.Ereditato – Neuchatel 21-22 June 2004
The NOA experiment
•
•
•
•
•
•
NuMI beam off-axis – 810 km
Far detector 14 kton
Near detector 222 tons
Liquid scintillator (4x6 cm2 cells)
First data 2012 (2.5 kton)
Full detector 2014
• Longer baseline (810 km)
(mass hierarchy?)