Status, results and future prospects on the neutrino oscillation experiments
“The new, the rare and the beautiful” Zürich, 6th6th--8th8th 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) 33--flavourflavour oscillation parameters The neutrino oscillation probability depends on the
4 mixing parameters (θ23 , θ12 , θ13 , δcp ), the masses 2 2 2 differences (∆m ij = m i - m j) and the energy E and the distance L from the source (matter effect).
θ12 ν 1 0 0 c 0 s e−iδ c s 0ν e 13 13 12 12 1 c s s c νµ = 0 23 23 0 1 0 − 12 12 0ν2 s c s eiδ c ντ 0 − 23 23 − 13 0 13 0 0 1ν3
Flavor θ23 θ13 , δ C Mass ij = cos( θij ) eigenstates S eigenstates ij = sin( θij ) Oscillation probability
P ( ν e → ν e )
L/E
Neutrino flavor at L is given by lepton identification in CC interaction Solar neutrinos experiments
Experiments only sensitive to
νe flavor (CC interaction) Homestake – SK - Gallex/GNO - Sage
⇒Deficit of predicted νννe flux is measured “Solar Neutrino Problem”
Predicted ⇒⇒⇒ pp
7Be Measured ⇒⇒⇒ 8B
Gallex/Sage Cl SK Solar neutrinos experiments
• SNO: Experiment sensitive to 3 flavors (CC+NC interactions)
− CC νe + d → p + p + e
NC ν x + d → p + n +ν x - measures total 8B ν flux from the Sun - equal cross section for all active ν flavors
− − ES ν x + e → νx + e Solar neutrinos experiments
• SNO: Experiment sensitive to 3 flavors (CC+NC interactions)
⇐⇐⇐ predicted
⇐⇐⇐ measured
In 2001, deficit of νννe flux is also measured, but the total flux is measured using the 3 flavors ⇒⇒⇒ absence of deficit
⇒⇒⇒ Neutrino oscillates νe νµ,τ Solar neutrinos experiments Confirmation with the KamLAND experiment (reactor ν’s)
258 events observed 365.2 ± 23.7 expected
(Disappearance confirmed at 99.99%)
m2 + 19.0 −5 2 ∆ = 59.7 − 21.0 ×10 eV + 3.1 θ12 = 34 4. − 2.1 degrees
Phys.Rev.Lett.101:111301,2008 SOLAR + KAMLAND (Reactor ν’s) Atmospheric neutrinos experiments
• «up-down» symetry of the flux • L is linked to zenith angle θ
• Flux mainly νµ for high energy
( νµ /νe ~ 2 for E < 1 GeV) Atmospheric neutrinos experiments
Super-Kamiokande
• L/E dependance • The observed deficit favors the
νννµ → ν τττ oscillation (No appearance of νννe flavor is observed)
−3 2 −3 2 1.9 10 < ∆ m 23 < 3.0 10 eV
2 sin 2θ23 > 0.9 (90% CL) Atmospheric neutrinos experiments
Confirmed by K2K (accelerator neutrino’s)
112 events observed 158.1 ± 9 expected without oscillation
−−−3−333 2 −−−3−333 222 1.9 10 < ∆< ∆ m 23 < 3.5 10 eV
2 for sin 2θθθ23 = 1 (90% CL) Atmospheric neutrinos experiments ••ConfirmedConfirmed by MINOS (accelerator neutrino’s) Atmospheric neutrinos experiments
• Global results with Super-K, K2K and MINOS data The CHOOZ experiment
• Mesurement of the νe flux from nuclear reactor (at 1km)
– Search for νe disappearance
No observation of oscillation νννe→ν x
Confirmation of the non observation of
νννµµµ→→→νννe from atmospheric neutrinos
⇒ Limite on θθθ13
2 sin 2θθθ13 < 0.1 ⇒ θθθ13 < 11° (90% CL) 33--flavorflavor oscillation parameters Where are we?
What do we know:
- There are three families of active, light neutrinos (LEP) 0 2 -5 2 - Solar neutrino oscillations: θθθ121212 ~30 ∆∆∆m12 ~7 10 eV 0 2 -3 2 - Atmospheric (νννµ −−−>−> ν> ν τττ?) oscillations: θθθ232323 ~45 ∆∆∆m23 ~ 2.5 10 eV 0 - Electron neutrino oscillations are small: θθθ131313 <<<10 What we do not know:
- Several unknown parameters: θθθ13 (only a limit) δδδcp 2 mass hierarchy sign( ∆m23 )
- Why θθθ12 and θθθ23 angles are large and θθθ13 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 2 •• Improve the precision on the atmospheric parameteparametersrs θθθ232323 and ∆∆∆m23
−−ννµµ disappearance: MINOS (also ννee appearance) −−ννττ appearance: OPERA
• Short term (in the next years 2010-2015)
•• θθθ131313 measurement θθ1313 < 33°°_ _ -- reactor experiments ((ννee →ννee)) DoubleDouble--Chooz,Chooz, Daya Bay, Reno
-- Superbeam experiments: ( ννµµ →ννee)) T2K, NO ννAA • Longer term (>2015?) •• New beams: ββ--beam,beam, νν--factfact
2 θθ1313 , CP violation δδcpcp , mass hierarchy sign( ∆m23 ) The OPERA experiment
Goal: First observation of ννντττ appearance in a pure νννµ 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 10 19 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 ννντττ appearance in a pure νννµ 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 10 19 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 µm thick) poured on a 10.2 cm 205 µm plastic base 12.5 cm (δx ~1 μm δθ ~1 mrad) 7.5 cm 3 8.3 kg Plastic base The OPERA experiment
Goal: First observation of ννντττ appearance in a pure νννµ 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 10 19 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 µm thick) Total target mass : 1.25 kt poured on a 10.2 cm 205 µm plastic base 12.5 cm (δx ~1 μm δθ ~1 mrad) 7.5 cm 3 8.3 kg Plastic base The OPERA experiment
1300 µm Charm events from 2009 run 500 µm µ 4.3 GeV similar topology for νννµµµ ντ event
First τ event expected in 2010
Primary vertex
νµ CC with 4 prongs
Secondary vertex Charged Charm decay into 3 prongs Charm flight length: 4.4 mm θθ1313 measurement
• Hint of θ13 >0 in current data? From solar+reactor+atmospheric From MINOS
Not really conclusive, effect is 1 or 1.5 σσσ Early evidence or discovery with T2K or reactor exp. θθ1313 measurement • Two complementary approaches: _ •• ννee disappearance reactor experiments: Double Chooz, Daya Bay, Reno
2 2 2 - Depends on sin (2 θθθ13 ) & ∆m31 , weakly on ∆m21
- Measurement is independent of δδδCP 2 - negligible matter effect (1km) - independent of sign( ∆m 13 ) θ ⇒”clean” 13 measurement But neutrino beam is not well know (need near and far detectors) Systematic error dominant
•• ννee appearance in ννµµ beam: T2K (250 km), NONO νννA (810 km)
-- PPµµµe is a complicated function depending on various parameters
2 -- θ13 measurement is correlated with δδδCP and sign( ∆m 13 ) T2K experiment θ • Main goal: Discovery of non-zero 13 – Increase the current sensitivity by a factor ~10
Off-axis beam (2.5°) Near detector (ND280) Quasi-monochromatic νµ beam (beam characterization) L/E tuned for max sensitivity
Small fraction of νe Reduced high-E non-CCQE bckg 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
2 • If sin 2θ13 >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 (ν-factory, β-beam)
– measure the value of δCP (if θ13 ≠0!) 2 – determine the mass hierarchy - sign( ∆m 13 ) (earth matter effect) Conclusion
2 • Still unknown oscillation parameters: θ13 δcp sign( ∆m 13 ) – The others are measured with some accuracy
• Upcoming reactor and accelerator neutrino 2 experiments will reach sin 2θ13 ~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
θ All effects are driven by 13 ! 2 ˆ m2 L 2 2 sin [(1−A)∆] ∆ P ≅ sin 2θ sin θ 13 Oscillation phase ν µ →νe 13 23 2 ∆ ≡ ()1−Aˆ 4E ˆ ˆ Neutrinos + sin ()A∆ sin []()1−A ∆ dominant « on peak » −α sin θ13 ξ sin δCP sin ∆ Anti Nu - Aˆ ()1−Aˆ sin ()Aˆ∆ sin []()1−Aˆ ∆ +α sin θ13 ξ cos δCP cos ∆ Aˆ ()1−Aˆ 2 ˆ 2 2 2 sin ()A∆ +α cos θ23 sin 2θ12 Aˆ2 E 2 ˆ ∆m A ≡ 2 2GF ne α ≡ 21 ∆m2 m2 13 ∆ 13 Matter effect sensitive to : ∆ 2 2-3 10 -2 • Sign of m 13 ξ ≡cos θ13 sin 2θ12 sin 2θ23 ≈Ο )1( • neutrino versus anti-neutrino For the special case of νννµµµ ààà νννe 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)
2 it requires : ∆m 12 and sin2 θθθ12 large (LMA solar): OK ! larger effects for long L: 2 nd oscillation maximum however…
2 sin 2θθθ13 small: low statistics and large asymmetry 2 sin 2θθθ13 large: high statistics and small asymmetry impact on the detector design …and: 2 oscillations are governed by ∆m atm , L and E: E ≈≈≈ 5 GeV à 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 L M, unlike L V (vacuum), is independent of the energy
- as an example L M (rock) is ~ 10000 km while L M (Sun) ~ 200 km 2 In the limit of ∆m sol 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
2 By the measurement of this asymmetry one can determine whether ∆∆∆m 23 is positive or negative (hierarchy)
νννe
ννντττ νννµµµ ν2 2 ν3 ∆m ν1 sol 2 ∆m atm ∆m2 ν atm 2 2 ν1 ∆m sol ν3 A.Ereditato – Neuchatel 21-22 June 2004 For E ν ~ E R large amplification of P( νµàνe) at long distances
A.Ereditato – Neuchatel 21-22 June 2004 The NO ννA experiment
• NuMI beam off-axis – 810 km • Far detector 14 kton • Near detector 222 tons • Liquid scintillator (4x6 cm 2 cells) • First data 2012 (2.5 kton) • Full detector 2014
• Longer baseline (810 km) (mass hierarchy?)